a geochemical and u-pb isotope study of lower crustal ...€¦ · the earth’s continental crust...

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i A geochemical and U-Pb isotope study of lower crustal xenoliths from the Monaro Volcanic Province, NSW: Implications for the deep crustal evolution of eastern Australia Natasha Barrett (20761355) School of Earth and Environment Supervisors: Dr Tony Kemp & Associate Professor Eric Tohver This thesis is submitted to fulfill the requirements for Master of Science (Geology) by way of Thesis & Coursework Faculty of Science The University of Western Australia (November 2014)

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Page 1: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

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A geochemical and U-Pb isotope study of

lower crustal xenoliths from the Monaro

Volcanic Province, NSW: Implications for

the deep crustal evolution of eastern

Australia

Natasha Barrett (20761355)

School of Earth and Environment

Supervisors: Dr Tony Kemp & Associate Professor Eric Tohver

This thesis is submitted to fulfill the requirements for Master of Science (Geology)

by way of Thesis & Coursework

Faculty of Science

The University of Western Australia

(November 2014)

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TABLE OF CONTENTS

1. Acknowledgements………………………………………………..…...….....iv

2. Abstract………………………………………………………………...……..v

3. Introduction……………………………………………………………...…1-8

3.1. Summary of 2013 findings……………………………………...…..2-3

3.2. Geological setting……………………………………………….…..4-7

3.3. Aims and objectives………………………………………….………..8

4. Methodology………………………………………………………………9-17

4.1. LA-ICP-MS……………….………………….……………………9-13

4.1.1. Analytical methods……………………………………………..9-11

4.1.2. Data processing………………………………………….……….13

4.2. Whole rock geochemistry…………………………………….…..13-14

4.2.1. Sample preparation………………………………………………13

4.2.2. Analytical methods…………………………………………....13-14

4.3. Calculations applied to geochemical data………………………...…14

4.4. SHRIMP U-Pb zircon geochronology…………………….……...15-17

4.4.1. Mineral separation…………………………………….………….15

4.4.2. Grain mount preparation…………………………………………15

4.4.3. Electron imaging……………………………………….…………16

4.4.4. Analytical methods………………………………….………….…16

4.4.5. Data processing……………………………………….……….16-17

5. Results……………………………………………...…………...……....…18-54

5.1. Mineral chemistry……………………………..……………...……18-27

5.1.1. Plagioclase…………………………………………….….………21

5.1.2. Scapolite………………………………………………….…….…22

5.1.3. Clinopyroxene…………………………………...……….……23-24

5.1.4. Orthopyroxene……………………………………………………25

5.1.5. Garnet………………………………………………………….…26

5.1.6. Rutile………………………………………………………...……27

5.2. Whole rock geochemistry…………………………………...……28-39

5.2.1. Major element geochemistry………………………….………28-32

5.2.2. Trace element geochemistry………………………….…….…33-39

5.2.2.1. Normalisation to bulk continental crust………………38-39

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5.2.2.2. Normalisation to mid ocean ridge basalts (MORB)…...…39

5.3. Mineral/whole rock concentration ratios……………………..…40-43

5.4. Zircon mineralogy………………………………………………..44-46

5.5. U-Pb (SHRIMP II) age determinations – Monaro Volcanic Province

xenoliths…………………………………………...………….…47-52

5.6. Comparison of the dated xenoliths to the Delegate breccia pipe

xenoliths……………………………………………………….…..…52

5.7. Age comparison to the regional lithological units………………52-54

6. Discussion………………………………………………………….…..…54-64

6.1. Origin of xenoliths from the Monaro Volcanic Province ……....54-58

6.1.1. Evidence from trace element geochemistry………...……...…54-56

6.1.2. Evidence from zircon analysis………..…………………….…56-58

6.1.2.1. Textural context and microstructures………….…...…56-57

6.1.2.2. Geochronology…………………………………………...57

6.2. Implications for crustal evolution………………………………..58-62

6.2.1. Relationship with regional granites………………………...…58-59

6.2.2. Implications of the Lachlan Fold Belt/Tasmanides evolution -

evidence from xenoliths…………………………………..……59-61

6.2.3. Implications for general crust forming processes……………...…62

6.3. Conclusions and future research…………………………………….63

7. References………………………….…………………………………..…64-72

APPENDIX 1. Summary of mineralogy and hand samples

APPENDIX 2. Original EMP data

APPENDIX 3. Pressure-temperature estimates

APPENDIX 4. Whole rock geochemistry data

APPENDIX 5A. Photomicrograph of thin sections analysed by LA-ICP-MS

APPENDIX 5B. LA-ICP-MS raw data

APPENDIX 6. Calculated concentration ratios and partition co-efficients

APPENDIX 7. SHRIMP data

APPENDIX 8. 2014 research proposal

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1. Acknowledgements

The research conducted for this MSc thesis was made possible by a number of

contributors and departments of whom I would like to express my appreciation

towards. Firstly, I would thank my supervisor Dr Tony Kemp for giving me the

opportunity to work on such an interesting project and for being a supportive and

knowledgeable mentor for the past two years, and to my co-supervisor, Associate

Professor Eric Tohver for his helpful advice and support, and discussions

throughout the year.

Analytical work was made possible by the staff and facilities at the Advanced

Analytical Centre, James Cook University, the Centre of Microscopy,

Characterisation and Analysis, UWA, and the John de Laeter Isotope Research

Centre at Curtin University. I would also like to thank the staff and services of the

GeoAnalytical Laboratory at Washington State University who produced high

quality whole rock geochemical data for this project, and Professor Richard

Arculus from the Australian National University for collecting these samples and

making them available for this study.

Travel costs were covered by a post-graduate student bursary kindly offered by the

Geological Society of Australia (Western Australian division).

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2. Abstract

Granulite xenoliths are fragments of the Earth’s lower continental crust. These samples

are transported to the Earth’s surface by younger, and explosive volcanic pipes,

providing a unique insight into the composition of rock material at inaccessible crustal

depths. This research builds on a detailed petrological study of granulite xenoliths

collected from alkali basalt pipes in the Monaro Volcanic Province and breccia pipes

near the town of Delegate, both within New South Wales, Australia. Geochemical

signatures indicate that these samples are basaltic cumulates, formed by the

accumulation of plagioclase during basaltic underplating that subsequently underwent

granulite facies metamorphism. Whole rock geochemistry further indicates a magmatic

provenance similar to arc basalts, suggesting that a subduction component has

influenced the composition of the lower crust beneath eastern Australia. Samples are

also depleted in heat producing elements (Th, U), characteristic of a residual lower

crust, with some showing a strong REE enrichment and negative Eu anomaly. These

compositions are suggestive of fractionated melt, perhaps complementary to the

depleted granulites.

Ion microprobe analysis of zircon from two Monaro Volcanic Province samples

(MVP10436 and MVP10437), yields a U-Pb concordia age of 419.4 ± 6.6 Ma and 402.5

± 6.3 Ma respectively. The 402.5 ± 6.3 Ma age is derived from a loose array along

concordia and its significance remains ambiguous. The 419.4 ± 6.6 Ma age is defined

by a tighter cluster of concordant data and is shown to be contemporaneous with the

emplacement of the Late Silurian I-type granites within the eastern Lachlan Fold Belt.

This age relationship provides new evidence for a genetic link between the mafic and

granulitic lower crust, and the more felsic upper crustal granites in eastern Australia,

signifying that arc magmatism and fractionation magma differentiation are key

processes in the growth and evolution of the continental crust during the Palaeozoic.

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3. Introduction

The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor

and McLennan, 1985). While this is true for much of the Earth’s middle and upper

crust, this classification is biased by the availability of upper crustal material over the

basaltic and inaccessible lower crustal region (>23km depth; Rudnick and Gao, 2003).

The origin of the continental crust remains actively debated, and multiple fields of Earth

science are involved in unravelling its composition, structure and formation. It is much

older than the oceanic crust and contains most rocks in the geological record, thus

preserving an archive of Earth evolution. Calculating the chemical composition of the

lower crust is far more difficult due to the inaccessibility of the Earth’s crust beyond

~12kms depth (Kremenetsky and Ovchinnikov, 1986). Exposed lower crustal material

exists as tectonically exhumed granulite facies terranes or in the form of xenoliths in

volcanic pipes (e.g. Irving, 1974; Francis, 1976). These pipes, forming explosive

diatremes, bring upper mantle and lower crustal fragments to the surface within hours to

days (e.g. Kushiro, 1976), which is ideal for preserving the prograde, high temperature

mineral assemblages of the lower crust. Their mineralogy denotes pressure and

temperature conditions of granulite facies metamorphism, possibly driven, at least in

part, through heat advection from mantle-derived magmas (e.g. Wells, 1980). Lower

crustal xenoliths therefore provide a potential record for the addition of new material to

the continents (Kemp et al., 2007).

The lower continental crust of post-Archean regions is dominantly mafic in composition

(e.g. Voshage et al., 1990; Miller and Christensen, 1994; Ross, 1985; Hart et al., 1990).

The majority of lower crustal xenolith samples are also mafic in composition (e.g.

Rudnick and Presper, 1990; Rudnick, 1992; Downes, 1993), although it is still unclear

how representative these xenoliths are of the lower crust (Rudnick and Gao, 2003). It is

believed that the granulitic lower crust generally represents a residual or cumulate

composition from the crystallisation and extraction of magmas, and thus is refractory,

depleted in radioactive heat producing incompatible elements (K, Th, U), and

mechanically strong due to the dominance of pyroxene over quartz (Taylor and

McLennan, 1985). Formation of the lower crust may therefore be fundamental for the

preservation, strengthening and stabilisation of continents as a whole (Rudnick, 1995).

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This project will explore these problems through studying deep-seated xenoliths, hosted

in breccia and alkali basalt pipes from southern New South Wales, Australia. By

assessing their geochemical signatures and using geochronology to constrain ages, it is

possible to determine if samples are fragments of lower crust, or represent a younger

magmatic material. This information will provide a unique insight into crustal processes

at inaccessible depths.

3.1. Summary of 2013 findings

Part 1 of this project undertaken in 2013, involved the detailed petrological study of

seventeen xenoliths samples from alkali basalt pipes of the Monaro Volcanic Province

and breccia pipes near the town of Delegate in NSW. These previous results will be

referred to as “Part 1” throughout this thesis. The major rock types from the Monaro

Province were a two pyroxene granulite (cpx+opx+pl±scp±rt±ilm), a garnet granulite

(grt+cpx+pl±scp±rt), and one sample showing disequilibrium textures between cpx,

opx, pl, grt, sp and ilm, referred to as a reaction intermediate (abbreviations after Kretz,

1983). The later suggests a dynamic and complex history in the lower crust, and

potentially provides evidence for larger scale processes of crustal thickening and

extension, as typifies convergent plate margins. Samples from the breccia pipes in

Delegate also included the garnet granulite and two pyroxene granulites and one

eclogite sample (grt+cpx±rt).

The first stages of analysis involved documentation of samples, petrophysical

measurements and preparation of thin sections. A summary of the major mineral

assemblages are provided in Table 1, and a summary of the mineralogy and hand

sample descriptions are presented in Appendix 1. This was followed by scanning

electron microscopy (imaging and semi-quantitative SEM-EDS), and electron

microprobe (WDS-EMP) analysis (Appendix 2). The results from this analysis were

used to analyse the mineralogy and mineral chemistry of the samples, and infer

pressure-temperature conditions of formation through thermobarometry calculations.

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Table 1. Classification of major rock types from the Delegate breccia pipes and Monaro Volcanic

Province (MVP) alkali basalt pipes. Xenolith classifications based on mineral assemblages in Lovering

and White, (1964) and mineral abbreviations according to Kretz, (1983).

The mineralogy of the xenoliths suggest pressure and temperature conditions of

granulite facies metamorphism (e.g. Wells, 1980), and the derived P-T values

(Appendix 3) are consistent with a thermally perturbed and thickened lower continental

crust. These data thus fitted the experimentally determined P-T conditions on previously

studied samples from Delegate, NSW (Irving, 1974). From this, a lower crustal origin

was suggested by analogy with the Delegate xenoliths (Chen et al., 1998).

Additional findings included the identification of scapolite in textural equilibrium with

granulite minerals. This appears to be a widespread, and possibly even a unique feature,

of deep crust beneath eastern Australia. The inferred primary nature of scapolite and its

crystallographically bound volatiles (CO3 and SO4) at the weight percent level suggest

that this mineral is potentially reservoir for carbon and sulfur in the lower crust.

Rock type Host rock/location Mineral Assemblage

Two-pyroxene

granulite

Alkali Basalt - MVP

Breccia pipe - Delegate

Opx+ Cpx + Pl ± Scp ± Ilm ± Mg ± Rt

Garnet granulite Alkali Basalt - MVP Grt + Cpx + Pl ± Scp ± Rt

Eclogite Breccia pipe - Delegate Cpx + Grt ± Rt

Reaction

intermediate Alkali Basalt - MVP

Cpx, Opx, Grt, Pl, Spl, Ilm

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3.2. Geological setting

Xenolith samples were collected from two localities in southeastern New South Wales,

Australia (Figure 1). Five samples were from the two diatremes known as the Delegate

breccia pipes outcropping at Airlie Park homestead, 35kms northwest of Delegate,

NSW (Lovering and White, 1969) (Figure 2A). These pipes are Mid-Jurassic in age,

~168 Ma based on K-Ar dating methods (Lovering and Richards, 1964). Twelve

xenolith samples were from alkali basalt pipes, Eocene-Oligocene in age (56-34 Ma;

Taylor et al., 1990) located northwest of Delegate around the town of Nimmitabel,

NSW within the Monaro Volcanic Province. This Monaro Volcanic Province hosts

approximately 65 eruption sites within its basaltic lava field (Roach et al., 1994). The

region has experienced extensive mafic volcanism which began during the late

Palaeocene and lasted for about 20 million years, where at least 630 cubic kilometres of

pyroclasts and lava erupted (Brown et al., 1993). The province is believed to be built up

by eruptions of alkali basalt, basanite and nephelinite (Roach et al., 1994). The surface

geology is dominated by mafic lavas and Tertiary volcanogenic sediments, which

overly Ordovician-Devonian bedrock.

The Delegate breccia pipes intrude the Silurian Snodgrass Adamellite (Chappell et al.,

1991). The pipes are in close proximity to the west of the Delegate and Buckleys Lake

Adamellite, and outcrop slightly north of the Tingaringy Granodiorite, all part of the

Berridale Batholith (Figures 2A and 2B). The Monaro Volcanic Province xenoliths are

taken from pipes within the lava field. The exact location was not specified, except

understood to be taken around the town of Nimmitabel, NSW. The Monaro Volcanic

Province lies within the Bega and the Berridale Batholiths. Nearby granitic units include

the Buckleys Lake Adamellite of the Berridale Batholith and the Glenbog Granodiorite

of the Bega Batholith (Figures 3A and 3B). Both xenolith localities occur within the

Ordovician-Devonian Lachlan Fold Belt of eastern Australia, but are related to a much

younger hot-spot magmatism (Lewis and Glen, 1995). The Lachlan Fold Belt is itself

part of the Terra Australis Orogen, a vast subduction-related accretionary orogenic

system that developed along the eastern Palaeo-pacific margin of Gondwanaland during

the Palaeozoic and Mesozoic (Cawood and Buchan, 2007; Braun and Pauselli, 2004).

This tectonic unit comprises the eastern third of the Australian continent (Gray and

Foster, 2004), as well as comprising a large part of western Antarctica and Argentina.

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Figure 1. Locations of the Delegate breccia pipes (A) and the Monaro Volcanic Province (B) in

southeastern, NSW. Regional geology is from the Bega-Mallacoota 1:250 000 geological sheet

(Lewis and Glen, 1995). Grid lines indicate 10 000m intervals of the Australian map grid zone 55.

Outline of eastern Australia is modified from Chen et al., (1998).

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Figure 2A. Enlarged map of region A from Figure 1 showing the location of the Delegate breccia pipes

1 and 2 intruding into the Snodgrass Adamellite. Pipes outcrop at the Airlie Park homestead, 35kms

North of Delegate, NSW. Other lithological regions including the Buckleys Lake Adamellite, Delegate

Adamellite and Tingaringy Granodiorite are also included. Regional geology from Bega-Mallacoota

1:250 000 geological sheet (Lewis and Glen, 1995).

Figure 2B. Simplified map of

the Numbla map sheet (White

and Chappell, 1989), modified

by Chen et al., (1998) showing

the major regional granite types

and the Delegate breccia pipe

localities.

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Figure 3A. Larger map of region B from Figure 1. Xenoliths are taken from one of the alkali basalt pipes

within the Monaro Volcanic Province near the town of Nimmitabel. Other major lithological regions

include the Glenbog Granodiorite and the Buckleys Lake Adamellite. Regional geology from Bega-

Mallacoota 1:250 000 geological sheet (Lewis and Glen, 1995).

Figure 3B. Simplified outline of

the Monaro Volcanic Province.

Samples were collected around

the town of Nimmitabel. The

shaded region represents mafic

lavas and Tertiary sediments,

while the surrounding area

represents the Ordovician-

Devonian Bedrock. Lava pile

outline is from Lewis et al.,

(1994) modified by Roach,

(2004).

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3.3. Aims and objectives

The aim of this study is to clarify the origin of granulite xenoliths from the Delegate and

Monaro Volcanic Province in eastern Australia. Particular attention will be on samples

from the Monaro Volcanic Province, as limited geochemical analysis has been

undertaken on these samples. This project will build on the foregoing detailed

petrological study of these xenoliths, and will focus on trace element geochemistry and

U-Pb zircon geochronology. A broader objective is to place new constraints on the

growth and evolution of the continental crust as a whole, from a lower crustal

perspective.

It is proposed that U-Pb geochronology of zircon will date the age of granulite facies

metamorphism by analogy with zircon ages from the Delegate breccia pipe xenoliths by

Chen et al., (1998). This could indicate whether granulite metamorphism in both

samples is driven by heat related to production of voluminous felsic magmatism and

batholith emplacement in this part of the Lachlan Fold Belt (~420 to 380 Ma; Gray and

Foster, 2004). Previous studies across several continents have assumed that xenoliths

contained by similar volcanic pipes represent fragments of lower crust (e.g. Francis,

1976; Selverstone and Stern, 1983; Kempton and Harmon, 1992; Kay and Kay, 1983;

Leyreloup et al., 1982). The exact origin of samples in this project has, however, yet to

be determined. Before interpreting data from the xenoliths in terms of lower crustal

processes, we first need to consider if the study samples did in fact originate from the

lower crust, which can be established from dating the xenolith samples relative to the

younger Eocene-Oligocene aged host rock (Roach, 2004).

Geochemical data will be used to determine the composition of the source magma and

to establish whether the xenolith samples represent cumulates, restites or solidified

basalts possibly related to the host pipes, and were subsequently crystalised under

granulite facies conditions. Determining the mode of formation and the compositional

variation of such samples is key to understanding crustal evolution as a whole.

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4. Methodology

4.1. Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS)

Preparation of seventeen (50µm) polished thin sections, optical microscopy, scanning

electron microscopy (SEM) and electron microprobe (EMP) analysis was undertaken in

Part 1 of this project (see Appendix 1 and 2). Petrography (optical microscopy and SEM

imaging), and EMP analysis was essential for characterising the mineral assemblages

and major element chemistry prior to LA-ICP-MS analysis.

4.1.1. Analytical methods

Six polished thin sections (MVP10438, MVP10437, DEL99-2-01, DEL2-10434,

MVP99-2-22, MVP99-2-12) were analysed using the LA-ICP-MS at the Advanced

Analytical Centre, James Cook University, Townsville, Australia. In situ trace element

analysis was carried out for 37 elements (Table 2) in garnet, plagioclase, pyroxene,

scapolite and rutile. LA-ICP-MS analysis was conducted using the Varian 820

quadrupole ICP-MS attached to a MicroLas ArF laser system of 193nm wavelength. A

carrier gas of helium (at ~ 0.8 l/min) was used to transport the ablated aerosol particles,

and was mixed with a nebulizer flow of argon (0.95 l/min) in a small glass mixing

chamber (~ 1cm3 volume) before entering the plasma torch. A small Ar sheath gas flow

of 0.1 l/min was used to enhance sensitivity and reduce oxide production. The mass

spectrometer was tuned at plasma conditions of Th/U ~ 1 in a NIST610 silicate glass,

and the production of molecular oxide species monitored by maintaining a low ThO/Th

ratio ~ 0.25%.

The laser system was operated at a 10Hz repetition rate, with an output energy of 100mJ

and laser fluence of 6 J/cm2. Spot sizes varied from 32 to 44µm in diameter, depending

on the size of the analytical target. The dwell time for all analyte elements was set to

10ms (except 139La and 151Eu at 20ms), corresponding to a mass sweep time of 843ms.

The total measurement time was 75 secs, of which the first 30 s was for blank

measurement (laser firing, shutter closed). Element concentrations were calibrated using

silicate glass NIST610 (Table 3) and by using predetermined EMP values of CaO and

TiO2 as internal standards. The silicate glass NIST612 was analysed as a secondary

standard (see Table 4).

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Element

and

isotope

Dwell

time

(ms)

L.O.D (ppm)

Element

and

isotope

Dwell

time

(ms)

L.O.D (ppm)

Mean Min Max Mean Min Max

7Li 10 1.07

0.35 2.49 140Ce 10 0.0025 0.00053 0.039

24Mg 10 2.55

0.94 5.48 141Pr 10 0.0016

0.00044 0.0042

29Si 10 1426.90

435.22 3615.97 143Nd 10 0.011

0.004 0.033

31P 10 16.82 5.37 40.05 147Sm 10 0.009 0.0024 0.029

43Ca 10 0.013

0.0042 0.033 151Eu 20 0.0026 0.00044 0.013

45Sc 10 0.17 0.055 0.4 157Gd 10 0.01 0.002 0.033

49Ti 10 0.58 0.21 1.44 159Tb 10 0.0014 0.00038 0.0059

51V 10 0.05 0.019 0.12 163Dy 10 0.005 0.0015 0.022

52Cr 10 1.08 0.39 2.57 165Ho 10 0.0014 0.00042 0.0049

60Ni 10 1.37 0.45 3.12 167Er 10 0.007 0.0016 0.021

65Cu 10 1.45 0.15 1.04 169Tm 10 0.001 0.00041 0.0048

85Rb 10 0.022 0.0059 0.074 171Yb 10 0.010 0.0033 0.048

88Sr 10 0.0088 0.0023 0.12 175Lu 10 0.0015 0.00045 0.0056

89Y 10 0.0094 0.0027 0.022 178Hf 10 0.0065 0.0012 0.039

90Zr 10 0.028 0.0069 0.058 181Ta 10 0.0023 0.00047 0.043

93Nb 10 0.0032 0.00085 0.01 208Pb 10 0.0056 0.0013 0.015

133Cs 10 0.0047 0.0011 0.053 232Th 10 0.0028 0.00056 0.018

137Ba 10 0.029 0.01 0.11 238U 10 0.0023 0.00051 0.015

139La 20 0.0024 0.00046 0.015

Table 2. Elements and isotopes analysed by LA-ICP-MS showing Limit of Detection (L.O.D) calculated

to 99% confidence.

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Element

and

isotope

Mean

(n=14)

±2 SD RSD

%

Values*

(ppm)

Element

and

isotope

Mean

(n=14)

±2 SD RSD

%

Values*

(ppm)

7Li 498.67 89.59 17.97 468.00 ± 24 140Ce 447.47 6.12 1.37 453.00 ± 8

24Mg 480.96 64.93 13.5 432.00 ± 29 141Pr 429.57 5.63 1.31 448.00 ± 7

31P 339.93 19.57 5.76 413.00 ± 46 143Nd 430.42 5.88 1.37 430.00 ± 8

43Ca 11.5 0 0 11.40 ± 0.2 147Sm 449.95 6.21 1.38 453.00 ± 11

45Sc 441.61 2.66 0.6 455.00 ± 10 151Eu 460.06 6.27 1.36 447.00 ± 12

49Ti 434.33 4.02 0.93 452.00 ± 10 157Gd 443.43 6.72 1.52 449.00 ± 12

51V 442.64 4.17 0.94 450.00 ± 9 159Tb 442.5 6.95 1.57 437.00 ± 9

52Cr 405.49 4.65 1.15 408.00 ± 10 163Dy 426.66 7.45 1.75 437.00 ± 11

60Ni 458.55 16.84 3.67 458.70 ± 4 165Ho 448.91 8.89 1.98 449.00 ± 12

65Cu 430.94 9.58 2.22 441.00 ± 15 167Er 425.87 8.47 1.99 455.00 ± 14

85Rb 425.08 5.87 1.38 425.70 ± 1 169Tm 420.07 8.25 1.96 435.00 ± 10

88Sr 514.26 6.74 1.31 515.50 ± 1 171Yb 444.71 8.1 1.82 450.00 ± 9

89Y 449.29 5.14 1.14 462.00 ± 11 175Lu 434.44 6.77 1.56 439.00 ± 8

90Zr 439.24 5.11 1.16 448.00 ± 9 178Hf 431.06 8.11 1.88 435.00 ± 12

93Nb 418.47 4.57 1.09 465.00 ± 34 181Ta 450.76 9.42 2.09 446.00 ± 33

133Cs 360.91 5.68 1.57 366.00 ± 9 208Pb 425.83 11.69 2.75 426.00 ± 1

137Ba 434.73 6.67 1.53 452.00 ± 9 232Th 458.14 13.53 2.95 457.20 ± 1

139La 456.56 6.68 1.46 440.00 ± 10 238U 463.81 17.56 3.79 461.50 ± 1

Table 3. NIST610 primary standard trace element concentrations MDL filtered. Uncertainty on NIST610

literature values from GeoReM (95% CL). Silica values are omitted as NIST610 is a silica glass. Values*

= literature values from Jochum et al., (2011).

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12

Table 4. NIST612 primary standard trace element concentrations MDL filtered. Uncertainty on NIST612

literature values from GeoReM (95% CL). Silica values are omitted as NIST612 is a silica glass. Values*

= literature values from the Jochum et al., (2011).

4.1.2. Data processing

Data were processed using the software package ‘Glitter’ (Van Achterberg et al., 2001).

Trace element compositions were calibrated using the major element compositions from

each mineral analysed where available. It is important to note that EMP analysis was

not originally done on sample MVP10437. Later in the project it was found that this

sample was significant as it contained zircon. Subsequently, trace elements in this

Element Mean

(n=9)

± 2 SD RSD% Values*

(ppm)

Element Mean

(n=9)

± 2 SD RSD

%

Values*

(ppm)

7Li 42.85 6.99 16.32 40.20 ±1.30 140Ce 38.31 1.10 2.86

38.40 ± 0.70

24Mg 60.97 7.72 12.66 68.00 ±5.10 141Pr 36.73 1.09 2.96

37.90± 1.00

31P 25.70 6.95 27.03 46.60 ±6.90 143Nd 35.39 1.03 2.92

35.50± 0.70

43Ca 11.85 0.00 0.00 11.90 ±0.10 147Sm 37.59 0.98 2.61

37.70± 0.80

45Sc 37.23 0.29 0.79 39.90 ±2.50 151Eu 37.02 1.03 2.79

35.60± 0.80

49Ti 37.67 1.31 3.47 44.00 ±2.30 157Gd 37.78 1.10 2.90

37.30± 0.90

51V 37.59 0.27 0.72 38.80 ±1.20 159Tb 38.28 1.24 3.24

37.60± 1.10

52Cr 33.73 1.04 3.09 36.40 ±1.50 163Dy 35.15 1.25 3.56

35.50± 0.70

60Ni 39.09 1.57 4.01 38.80 ±0.20 165Ho 38.77 1.45 3.74

38.30± 0.80

65Cu 38.64 0.69 1.79 37.80 ±1.50 167Er 36.42 1.52 4.18

38.00± 0.90

85Rb 31.72 0.49 1.55 31.40 ±0.40 169Tm 36.53 1.49 4.07

36.80± 0.60

88Sr 78.82 1.24 1.57 78.40 ±0.20 171Yb 38.40 1.36 3.55

39.20± 0.90

89Y 37.89 0.63 1.66 38.30 ±1.40 175Lu 36.99 1.18 3.19

37.00± 0.90

90Zr 37.93 0.95 2.50 37.90 ±1.20 178Hf 37.24 1.31 3.51

36.70± 1.20

93Nb 34.85 0.82 2.35 38.90 ±2.10 181Ta 38.30 1.30 3.40

37.60± 1.90

133Cs 41.63 1.13 2.70 42.70 ±1.80 208Pb 38.73 1.78 4.59

38.57± 0.20

137Ba 37.96 1.25 3.29 39.30 ±0.90 232Th 38.32 1.93 5.05

37.79± 0.08

139La 37.77 1.13 2.98 36.00 ±0.70 238U 38.04 2.28 5.99

37.38± 0.08

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13

sample analysed by LA-ICP-MS were calibrated using average values from the other

two pyroxene granulites (DEL99-2-01 and MVP10438).

4.2. Whole rock geochemistry

4.2.1. Sample preparation

Sample preparation for whole rock geochemistry was undertaken on twelve samples

(Table 5) at the University of Western Australia’s geotechnical laboratory, and

GeoAnalytical Laboratory, Washington State University. Twelve samples were cut with

a diamond saw, polished, washed in deionised water and placed in an ultrasonic bath to

remove surface contamination (i.e. saw marks, ink or alteration from weathering), that

could potentially affect the geochemical results. Each sample was reduced to rock chips

using a hydraulic tungsten-carbide rock crusher, and the least-altered material was

handpicked for geochemical analysis. This material was then reduced to a powder using

an agate (silica based) ball mill to avoid tungsten carbide contamination, which can

compromise trace elements such as Ta.

Whole rock geochemistry

MVP10436 DEL99-2-01

MVP10438 DEL2-10434

MVP99-2-08 MVP99-2-13

MVP10437 MVP99-2-22

DEL2-10431 MVP99-2-12

DEL2-10430 MVP99-2-04

Table 5. Samples selected and analysed for whole rock geochemistry

4.2.2. Analytical methods

Whole rock major and trace element analysis was undertaken on the twelve xenoliths.

Sample powders were sent to the GeoAnalytical Laboratory at Washington State

University. Each powder (~ 4g) was fused with a di-lithium-tetraborate (Li2B4O7)

(Spectromelt ® A-10, EM Science, Gibbstown, NJ) flux and made into homogenous

glass disks for major and trace elements. A ThermoARL X-ray Fluorescence

Spectrometer (XRF) was used to measure major and some trace elements, and an

Agilent 4500 Quadrupole Inductively Coupled Plasma Mass Spectrometer (Q-ICP-MS)

was used for determination of most trace elements (Appendix 4). For the latter

instrument, fused discs were prepared separately and dissolved in a mixture of HF-

HNO3. Ru, In and Re are used as internal standards to correct for instrumental drift and

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14

mass-dependant differences, REEs are standardised using a linear interpolation method

between In and Re (Doherty, 1989). To avoid isobaric interferences, the CeO/Ce ratio

is maintained at <0.5%. Several reference rock powders from USGS international rock

standards (Jenner et al., 1990; Lichte et al., 1987; Longerich et al., 1990), were analysed

concurrently with the samples to assess the accuracy of the results. Volatile components

were determined by loss on ignition, which involved heating ~ 2g of sample powder in a

carbon crucible overnight at 1100°C in a furnace.

4.3. Calculations applied to geochemical data

Equations used for both whole rock and LA-ICP-MS geochemical data in this thesis are

provided here.

Equation 1. Mineral/whole rock concentration ratios (C)

C = Cmini

CWRi

i = element, C = concentration of trace element, min = mineral analysed, WR = whole

rock sample.

Equation 2. Europium anomaly (Eu/Eu*)

Eu/Eu*= (Eu/EuN) /√Sm/SmN ∗ Gd/GdN

Sm/SmN, Gd/GdN and Eu/EuN represent values normalised to CI Chondrite by Sun and

McDonough, (1995).

Equation 3. Magnesium Number (Mg#)

Mg# = 100 x MgO (mol %)

(MgO+FeO)mol %

FeO represents total Fe3+ and Fe2+

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15

4.4. SHRIMP II U-Pb zircon geochronology

4.4.1. Mineral separation

Two samples were selected for zircon separation, based on their moderately high

zirconium contents (~ 100 ppm Zr) as ascertained by whole rock geochemistry. For this

purpose, the remaining crushed sample material that was not used for whole rock

geochemical analysis (~ 500 g) was pulverised using a disk mill adjusted to 500µm

grainsize output. Unwanted material was initially removed by carefully decanting

suspended fine particles from a water filled beaker. A hand magnet was run then over

the mineral separates to remove as much strongly magnetic material as possible. The

remaining material was then run through a Frantz magnetic separator, incrementally

increasing the magnetic current (0.4A, 0.8A, 1.0A and 1.2A), and using gradient

settings of tilt angle 10° and side slope of 15°. Zircon was isolated from the non-

magnetic fraction using a LST (Lithium heteropolytungstate) heavy liquid (2.67g/cm3)

and a 26 cm plastic gold pan.

4.4.2. Grain mount preparation

Approximately two hundred zircon grains were hand-picked under a binocular

microscope from each sample and cast into a 25 mm diameter epoxy resin (Buehler

Epoxicure®) disc, which was left to cure overnight. The grain mount was then polished

to expose the centre of the zircon crystals, using a 3µm diamond compound on a

diamond impregnated polishing lap, and then with a 1µm diamond paste on a silk

polishing lap for 3-5 minutes. The polished sample was viewed under a reflected light

microscope to check for small scratches, and polishing continued as appropriate to

remove surface marks, cleaning the sample ultrasonically between each stage.

Gold coating of the grain mount was undertaken at the John de Laeter Centre for

Isotope Research, Curtin University. Prior to coating, the grain mount was cleaned with

propanol, and consecutively placed in an ultrasonic bath of petroleum spirit, soap

solution and de-ionised water before being placed in <60°C oven for 30 mins to dry.

Gold coating was done using an EMITECH K950X vacuum evaporator set to 40nm at a

deposition rate of 1nm/sec. The glass vacuum chamber was cleaned with Kimwipes and

the mount placed in the centre of the dish. Gold was added to the wire basket, and the

current increased (5-6 A) until the gold melts and vaporises, and the target coating

thickness is met.

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16

4.4.3. Electron imaging

Zircon grains were characterised using Scanning Electron Microscopy (SEM), applying

both backscattered electron (BSE) and cathodeluminescence (CL) imaging. Electron

imaging was undertaken at UWA’s Centre for Microscopy, Characterisation and

Analysis. SEM operating conditions for BSE imaging were an accelerating voltage of

10kV, beam intensity of 20 Amps, process time of 5 seconds and working distance of

10 mm for the Zeiss 1555 VP-FESEM and 15 mm for the TESCAN VEGA3. CL

imaging was done using the CL detector attached to the TESCAN VEGA3. This was

required to reveal any internal microstructures and to identify areas for spot analysis by

SHRIMP. Conditions for CL imaging were an accelerating voltage of 10kV, beam

intensity of 15 Amps and low magnification (100-150 x Mag).

4.4.4. Analytical methods

U-Pb geochronology of zircon was undertaken at the John de Laeter Centre for isotope

research at Curtin University, using the Sensitive High Resolution Ion Microprobe

(SHRIMP II). Established analytical protocols were followed for this analysis, as

described by Williams, (1998). Sample zircons were mounted with reference zircons

TEMORA 2 (416.8 ± 0.3 Ma; Black et al., 2003) and M257 (561.3 ± 0.3 Ma; Nasdala et

al., 2008), along with NIST610 glass to ensure accurate centring on the small 204Pb

peak. The reference zircons were analysed after every 3-4 spot analysis. Common lead

(204Pb) correction were applied based on the measured background-corrected 204Pb

counts, using the methods applied in Compston et al., (1984).

4.4.5. Data processing

Data reduction and processing was done using SQUID 2.50 and ISOPLOT 3.71 (add-

ins for Microsoft Excel; Ludwig, 2009), using the decay constants by Steiger and Jäger,

(1997). Individual uncertainty analyses are reported at 1σ level and mean ages for

206Pb/238U calculated to 2σ. The isotope ratios were plotted on Tera-Wasserburg

concordia diagrams (Tera and Wasserburg, 1972) to permit data processing without

correction for common 204Pb, allowing for any inaccurate or negative corrections

associated with background interference. Weighted mean ages were determined using

the 206U/238Pb ratios. Common lead (204Pb) corrected values were used when this

correction was positive, and the uncorrected 206U/238Pb values used when this correction

was negative. These values used to calculate the weighted mean ages are shown in

Table 6.

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17

Table 6. 204Pb corrected or uncorrected values used to calculate weighted mean ages for samples

MVP10436, MVP10437 and TEMORA-2 zircon standard.

206U/238Pb common lead corrected age

MVP10436 Age (Ma) MVP10437 Age (Ma) TEMORA-2 Age (Ma)

36-01 409±10.7 37-04 372±8 TEM2-09 408±7.4

36-06 385±7.2 37-05 400±9

36-11 431±9.1 37-11 396±7

36-15 440±16.7 37-15 383±8

36-17 424±8.4

36-18 433±8.9

206U/238Pb uncorrected age

MVP10436 Age (Ma) MVP10437 Age (Ma) TEMORA-2 Age (Ma)

36-02 421±7.4 37-01 371±9 TEM2-01 428.9±17.6

36-03 408±8.0 37-02 368±9 TEM2-02 419.8±7.5

36-04 412±7.9 37-03 352±10 TEM2-03 423.0±7.6

36-05 401±8.7 37-06 385±8 TEM2-04 415.8±8.0

36-07 394±8.1 37-07 407±11 TEM2-05 403.1±8.0

36-08 360±11.3 37-08 401±9 TEM2-06 410.0±8.0

36-09 415±10.3 37-09 358±10 TEM2-07 413.8±7.9

36-10 419±21.8 37-10 421±9 TEM2-08 404.4±7.7

36-12 402±14.6 37-12 386±7 TEM2-10 411.8±7.8

36-13 412±7.4 37-13 352±6 TEM2-11 417.1±8.8

36-14 413±7.3 37-14 411±9

36-16 433±8.0 37-16 423±7

37-17 404±9

Page 24: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

18

5. Results

5.1. Mineral chemistry

Major element compositions from EMP analysis for plagioclase, orthopyroxene,

clinopyroxene, garnet and scapolite were determined in Part 1 of this study. End

member compositions were also calculated from the EMP data and are summarised in

Table 7.

Sample End member composition

MVP10438

(two pyroxene)

Pl (An92-93Ab9-10Or0.1-0.2) + Cpx (En38Fs12-14Wo49) + Opx (En65-67Fs33-34Wo0.1-1.5) +

Scp (Me83-85Ma16-17)

DEL99-2-01 (two

pyroxene)

Pl (An92-94Ab6-8Or0-0.1) + Cpx (En40Fs9-10Wo50-51) + Opx (En72-77Fs23-24Wo0-1.5)

MVP10437 (two

pyroxene)

(End member compositions unavailable for sample MVP10437 as explained in

methods section 4.1.2.). Pl (An89-91) by optical microscopy.

MVP99-2-22

(garnet granulite) Cpx (En37-38Fs19-20Wo42-43) + Grt (Al39-46Gr15-23Py38-39)

MVP99-2-12

(garnet granulite) Cpx (En39Fs14Wo48) + Grt (Al35-37Gr21-22Py41-43) + Scp (Me83-84Ma16-17)

DEL2-10434

(eclogite)

Cpx (En35-38Fs12-14Wo49) + Grt (Al40-41Gr20-23Py36-39)

Table 7. Summary of mineral assemblages and end members for the samples analysed for LA-ICP-MS.

This year’s research focused on the trace element compositions of these major minerals

by LA-ICP-MS. Analysis was conducted on six thin sections, the two pyroxene

granulites MVP10437, MVP10438 and DEL99-2-01, the garnet granulites MVP99-2-12

and MVP99-2-22, and eclogite DEL2-10434. These samples were chosen as they

showed the least grain boundary alteration without evidence for textural disequilibrium

(e.g. reaction relationships) between phases. It is important to state at the outset that the

major minerals of these samples showed very little variation in major element

composition, and the trace element inventory of each mineral within a given sample was

also remarkably uniform. For this reason, the below descriptions and corresponding

diagrams refer to average compositions of each mineral within a particular xenolith

sample. Trace element averages for each mineral and sample are shown in Tables 8 and

9. Photomicrographs of these thin sections and the original LA-ICP-MS data for all spot

analyses are presented in Appendix 5A and 5B.

Page 25: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

19

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6.1

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52

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47

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48

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62

87

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93

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17

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95

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0.0

60

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0.0

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0.0

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0.0

00

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.11

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0.0

50

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60

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55

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41

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17

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3.2

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0.4

77

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1.7

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18

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8.3

78

.93

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9.2

50

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0.1

10

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9.4

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4.9

42

.95

3.2

43

.29

1.7

91

7.9

70

.01

0.0

30

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0.9

71

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1.5

90

.93

1.4

60

.95

0.7

63

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0.0

10

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0.0

30

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0.5

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4.4

51

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63

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2.7

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0.5

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0.0

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0.0

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2.5

30

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2.1

44

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3.4

92

1.8

50

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0.2

20

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0.0

80

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0.3

90

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0.3

30

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0.7

64

.51

0.0

30

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0.3

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0.0

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0.7

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0.6

32

.17

2.0

21

1.6

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0.2

31

.20

0.0

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0.0

70

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0.0

70

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0.2

91

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0.3

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60

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0.0

40

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0.0

40

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0.2

71

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40

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20

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0.4

50

.34

0.2

00

.93

0.8

33

.14

5.6

44

.36

V1

36

.73

25

3.1

61

78

.26

0.5

70

.59

0.2

74

.32

1.3

15

76

.70

20

94

.88

72

6.7

9

Cr

53

8.3

04

86

.85

56

6.1

6-

0.9

0-

9.7

9-

51

4.9

97

83

.74

65

8.1

9

Ni

25

.34

35

.98

21

.16

-1

.03

-1

.74

1.5

1-

5.8

2-

Cu

1.0

51

.38

1.4

2-

1.5

0-

0.5

5-

2.3

33

.11

2.5

5

Rb

0.0

30

.08

0.0

40

.28

0.5

20

.13

0.0

60

.04

0.0

20

.03

-

Sr

0.4

90

.50

0.1

12

44

6.4

68

44

.45

58

4.5

86

48

.32

67

4.8

31

.50

1.3

91

.43

Y8

2.8

71

9.3

86

1.1

9-

0.0

40

.14

0.1

81

.13

0.1

20

.12

0.1

0

Zr

49

.36

27

.08

11

.60

-0

.04

0.0

30

.05

0.1

38

89

.41

14

64

.94

13

18

.60

Nb

0.0

10

.02

0.0

00

.01

0.0

00

.00

0.0

00

.00

10

0.2

94

10

3.3

07

18

.73

Cs

0.0

10

.07

--

0.0

00

.00

--

0.0

10

.03

0.0

0

Ba

0.0

30

.23

0.0

41

51

.64

12

1.4

82

6.1

61

4.9

81

31

.21

1.1

3-

0.0

4

La

0.0

30

.04

0.0

14

.11

1.0

61

.79

0.5

61

5.3

90

.03

0.1

5-

Ce

0.3

80

.46

0.1

25

.09

1.2

82

.71

1.0

42

6.2

30

.01

0.0

40

.00

Pr

0.1

70

.19

0.0

60

.42

0.1

20

.26

0.1

22

.50

0.2

70

.01

0.0

0

Nd

2.2

42

.19

0.9

31

.01

0.4

20

.84

0.4

88

.50

0.0

10

.15

-

Sm

2.4

51

.81

1.4

50

.08

0.0

60

.12

0.0

60

.99

--

0.1

0

Eu

1.4

40

.99

1.1

60

.34

0.3

80

.36

0.2

42

.18

-0

.01

0.0

0

Gd

6.7

22

.99

4.7

90

.05

0.0

30

.06

0.0

80

.60

0.0

10

.09

0.4

4

Tb

1.6

90

.53

1.2

30

.01

0.0

00

.00

0.0

10

.05

0.0

0-

0.0

0

Dy

13

.07

3.6

49

.65

0.0

10

.01

0.0

30

.04

0.2

4-

--

Ho

3.3

00

.81

2.4

1-

0.0

00

.00

0.0

10

.03

-0

.00

0.0

1

Er

9.7

02

.25

7.1

20

.01

0.0

10

.01

0.0

20

.08

-0

.01

-

Tm

1.4

80

.34

1.1

1-

0.0

0-

0.0

00

.01

-0

.00

-

Yb

10

.34

2.3

87

.63

0.0

30

.01

0.0

10

.02

0.0

50

.01

-0

.07

Lu

1.5

80

.36

1.2

1-

0.0

0-

-0

.01

0.0

00

.05

0.0

0

Hf

0.6

50

.44

0.2

5-

0.0

1-

0.0

00

.01

33

.34

43

.37

31

.85

Ta

0.0

10

.00

0.0

0-

0.0

0-

0.0

0-

8.7

03

80

.02

67

.65

Pb

0.0

10

.04

0.0

23

.49

1.1

51

.02

0.3

37

.99

0.0

20

.01

-

Th

0.0

00

.00

0.0

0-

0.0

00

.00

-0

.00

0.2

9-

0.0

8

U0

.01

0.0

00

.00

-0

.00

-0

.00

-0

.69

1.2

91

.14

Page 27: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

21

5.1.1. Plagioclase

Plagioclase is present in the two pyroxene xenoliths MVP10437, MVP10438, DEL99-

2-01, and garnet granulites MVP99-2-12 and MVP99-2-22. Figure 3A shows that

plagioclase is enriched in Ba (15-152 ppm) and Sr (585-2447 ppm) relatively to other

trace elements in plagioclase. The REE patterns of plagioclase is characterised by a

strong positive Eu anomaly (Eu/Eu* = 8.6- 26.9), and a positive LREE/HREE ratio

(LaN/YbN = 22.3- 246.6) (Figure 3B). Sample MVP10437 shows a similar pattern to

plagioclase in the other samples, but is significantly enriched in the REEs.

Figure 3A & 3B. Multi-element and REE diagrams for trace elements in plagioclase normalised to CI

Chondrite (Sun and McDonough, 1995). Garnet granulites = red and two pyroxene granulites = green.

0.001

0.01

0.1

1

10

100

1000

Cs Rb Ba Th U Nb Ta Pb Sr Hf Zr Y

Min

era

l/C

hon

dri

te

(3A) Plagioclase

0.01

0.1

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Min

eral/

Ch

on

dri

te

(3B)

MVP99-2-12 MVP99-2-22MVP10438 DEL99-2-01MVP10437

Page 28: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

22

5.1.2. Scapolite

Scapolite occurs in the two pyroxene granulite MVP10438, and garnet granulite

MVP99-2-12. As with plagioclase, scapolite displays a high concentration of Ba (483-

2003 ppm) and Sr (26 -66 ppm) (Figure 4A). It is also noted that the Ba and Sr

concentrations are greater in scapolite contained by the garnet bearing sample (MVP99-

2-12). Scapolite shows an overall positive LREE/HREE ratio (Figure 4B). Scapolite in

these two samples shows a positive Eu anomaly (Eu/Eu* = 1.9-2.4), and an unusual

relative depletion in Sm. HREEs are depleted in scapolite of the garnet-bearing sample

MVP99-2-22 relative to that in the two pyroxene granulite MVP10438.

Figure 4A & 4B. Multi-element and REE diagrams for trace elements in scapolite normalised to CI

Chondrite (Sun and McDonough, 1995). Garnet granulites = red and two pyroxene granulites = green.

0.001

0.01

0.1

1

10

100

Rb Ba Th U Nb Ta Pb Sr Hf Zr Y Cs Ti V

Min

eral/

Ch

on

dri

te

(4A) Scapolite

0.01

0.1

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Min

eral/

Ch

on

dri

te

(4B)

MVP99-2-12 MVP10438

Page 29: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

23

5.1.3. Clinopyroxene

Clinopyroxene occurs in the two pyroxene granulites MVP10437, MVP10438, DEL99-

2-01, the garnet granulites MVP99-2-12 and MVP99-2-22, and the eclogite sample

DEL2-10434. Clinopyroxene in most xenoliths shows relative depletions in Cs, Rb, Ba,

Ni, Pb, Nb and Ta, and enrichments in Sr, Zr, Hf, Ti, Y, Sc and Li (Figure 5A). The two

pyroxene granulites have a Sr content in clinopyroxene ranging from 12-20 ppm,

whereas the garnet granulites show a higher and more variable Sr content ranging from

49 -181 ppm.

REE concentrations in clinopyroxene are highly variable, with the garnet bearing

samples (DEL2-10434, MVP99-2-12 and MVP99-2-22) having a positive LREE/HREE

ratio, and the non-garnet bearing samples (MVP10438, DEL99-2-01 and MVP10437)

with a negative LREE/HREE ratio. Clinopyroxene in the two pyroxene granulites

MVP10437, MVP10438 and DEL99-2-01shows a strong LREE depletion and a

negative Eu anomaly in MVP10437 and MVP10438. Clinopyroxene in MVP10437

show a higher concentration in REEs relative to clinopyroxene in the other analysed

samples. Clinopyroxene in the garnet bearing samples MVP99-2-12 and MVP99-2-22

shows a relative depletion in the HREEs, reflecting the presence of garnet.

Page 30: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

24

0.0001

0.001

0.01

0.1

1

10

100

Li Cs Rb Ba Th U Nb Ta Pb Sr Zr Hf Ti V Y Sc Cr Ni

Min

eral/

Cch

on

dri

te

(5A) Clinopyroxene

DEL2-10434 MVP99-2-12 MVP99-2-22

MVP10438A DEL99-2-01 MVP10437

0.1

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Min

era

l/C

hon

dri

te

(5B)

DEL2-10434 MVP99-2-12 MVP99-2-22

MVP10438A DEL99-2-01 MVP10437

Figure 5A & 5B. Multi-element and REE diagrams for trace elements in clinopyroxene

normalised to CI Chondrite (Sun and McDonough, 1995). Garnet granulites = red, two pyroxene

granulites = green and eclogite = black.

Page 31: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

25

5.1.4. Orthopyroxene

Orthopyroxene is a major mineral in the two pyroxene granulite MVP99-2-10 and

MVP10438. Most trace elements in orthopyroxene are present in low concentrations,

and measurable elements include U, Y, Sc, Ti an V. Rare earth elements in

orthopyroxene show a strong depletion in LREEs relative to HREEs, and a slight

negative Eu anomaly is observed in MVP10437 (Figure 6B).

Figure 6A & 6B. Multi-element and REE diagrams for orthopyroxene normalised to CI Chondrite (Sun

and McDonough, 1995). Two pyroxene granulites = green.

0.0001

0.001

0.01

0.1

1

10

Ba Th Nb Ta Pb Sr Hf Zr Y Ti Sc V Cr Ni

Min

eral/

Ch

on

dri

te

(6A) Orthopyroxene

0.001

0.01

0.1

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

MIn

eral/

Ch

on

dri

te

(6B)

DEL99-2-01 MVP10438A MVP10437

Page 32: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

26

5.1.5. Garnet

Garnet is present in the garnet granulites MVP99-2-12, MVP99-2-22, and the eclogite

sample DEL2-10434. Most non-REE trace elements in Figure 7A are low in

concentrations relative to the high field strength elements Zr, Hf, Ti, Y and Sc. As is

typical of garnet, rare earth elements show a HREE enrichment and depletion in LREEs

(Figure 7B). The degree of fractionation within the LREEs is much more significant

than the HREE fractionation, with sample MVP99-2-12 showing little to no HREE

fractionation.

Figure 7A & 7B. Multi-element and REE diagrams for trace elements in garnet normalised to CI

Chondrite (Sun and McDonough, 1995). Garnet granulite = red and eclogite = black.

0.001

0.01

0.1

1

10

100

Cs Rb Ba Th U Nb Ta Pb Sr Zr Hf Ti V Y Sc

Min

eral/

Ch

on

dri

te

(7A) Garnet

0.01

0.1

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Min

eral/

chon

dri

te

(7B)

DEL2-10434 MVP99-2-12

MVP99-2-22

Page 33: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

27

5.1.6. Rutile

Trace elements were determined from rutile of the garnet granulite samples MVP99-2-

12 and MVP99-2-22, and the eclogite sample DEL2-10434. Rutile was analysed for the

full suite of trace elements, with most elements at concentrations below the detection

limits. Chondrite normalised values of the most abundant trace elements show an

enrichment in Zr, Nb, Hf, Ta and U relative to Sc, V, Cr, Cu, Sr and Y (Figure 8). Of

the more enriched elements, Nb and Ta show large variations between rutile grains of

the different rock types (Nb = 100-4141 ppm, Ta = 9-384 ppm).

Figure 8. Multi-element diagram for trace elements in rutile normalised to CI Chondrite (Sun and

McDonough, 1995). Garnet granulites = red and eclogite = black.

0.01

0.1

1

10

100

1000

10000

U Nb Ta Sr Zr Hf V Y Sc Cr Cu

Min

era

l/C

hon

drt

ie

Rutile

DEL2-10434 MVP99-2-12

MVP99-2-22

Page 34: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

28

5.2. Whole rock geochemistry

5.2.1. Major element geochemistry

Whole rock major and trace element compositions were determined for eight samples

from the Monaro Volcanic Province, and four samples from the Delegate breccia pipes

(Table 10). All samples are basaltic and metaluminous in composition (ASI = 0.54-

0.95). The SiO2 content ranges from 46.9-51.5 wt. % for the two pyroxene and garnet

granulite samples, while the eclogite sample (DEL2-10434) has a slightly lower silica

content at 45.1 wt. %. Two pyroxene granulites MVP10436 and MVP10437 show a

higher TiO2 concentration (2.0 and 1.8 wt. %), than the other two pyroxene granulites

(<0.3 wt. %), and the garnet granulites (<1.1 wt. %), reflecting the Fe-Ti oxide minerals

in these samples. The magnesium number (Mg#) is variable among the samples,

although MVP10436 and MVP10437 have distinctively lower magnesium numbers

(52.3 and 54.5, respectively). Garnet granulite MVP99-2-22 has a slightly lower Al2O3

content at 15.9 wt. %, compared to the granulite samples.

The two pyroxene granulite from Griffin & O’Reilly, (1986) with later zircon U-Pb age

determinations from Chen et al., (1998), are included in Table 11. The major element

compositions from Griffin & O’Reilly, (1986) show the same characteristics as samples

MVP10436 and MVP10437 determined by this study. Bulk lower crustal compositions

from Rudnick and Presper, (1990) and Rudnick and Fountain, (1995), are also

compared to values from this study. The average silica content for xenoliths from the

Monaro and Delegate samples is 48.5 wt. %, slightly lower than the values from

Rudnick and Presper, (1990) and Rudnick and Fountain, (1995). The average Mg# of

the Monaro and Delegate xenoliths (64.6) is slightly higher than average values given

by Rudnick and Presper, (1990) and Rudnick and Fountain, (1995).

Page 35: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

29

Table 10. Whole rock major element wt. % oxides for two pyroxene granulite (2pG), garnet granulite

(GG) and eclogite (Ec) xenoliths. DEL = Delegate breccia pipes, MVP = Monaro Volcanic Province. FeO

= total iron. Mg# calculated following Equation 3 in methods section 4.3.

Rock 2pG 2pG 2pG 2pG GG GG

Sample

MVP10436

MVP10437

MVP10438

MVP99-2-08

MVP99-2-04

MVP99-2-12

SiO2 46.87 47.61 48.44 49.13 50.46 46.99

TiO2 1.98 1.77 0.27 0.15 0.49 0.72

Al2O3 17.22 16.49 20.97 18.55 19.33 18.50

FeO 11.88 11.81 7.15 6.21 6.37 10.69

MnO 0.21 0.22 0.14 0.13 0.13 0.18

MgO 7.30 7.93 8.39 10.96 7.87 9.08

CaO 11.37 10.79 13.13 13.68 11.35 10.91

Na2O 2.54 2.80 1.39 1.14 3.64 2.14

K2O 0.31 0.31 0.11 0.05 0.41 0.72

P2O5 0.32 0.27 0.02 0.01 0.05 0.06

Mg# 52.27 54.48 67.66 75.88 68.77 60.22

Rock GG GG 2pG Ec 2pG 2pG

Sample

MVP99-2-

13

MVP99-2-22

DEL99-2-01

DEL

2-10434

DEL

2-10430

DEL2

-10431

SiO2 48.89 51.53 48.78 45.09 50.22 47.75

TiO2 0.39 1.09 0.24 1.96 0.76 0.60

Al2O3 17.55 15.88 19.06 14.04 17.50 20.18

FeO 7.76 9.32 6.25 11.48 7.42 8.34

MnO 0.16 0.17 0.12 0.20 0.14 0.15

MgO 10.54 7.29 11.37 9.86 9.02 7.38

CaO 11.45 9.95 12.76 14.42 12.12 13.13

Na2O 2.70 4.21 1.35 2.67 2.61 2.12

K2O 0.52 0.56 0.07 0.16 0.13 0.16

P2O5 0.04 0.02 0.01 0.13 0.08 0.20

Mg # 70.77 58.23 76.43 60.49 68.42 61.2

Page 36: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

30

Table 11. Whole rock major element wt. % oxides for two pyroxene granulite (2pG), garnet granulite

(GG) and eclogite (Ec) xenoliths from published values on similar rock types (Lovering and White, 1969;

Griffin and O’Reilly, 1986). Bulk lower crustal values from Rudnick and Presper, (1990) and Rudnick

and Fountain, (1995). Average major element compositions from this study for the Monaro Volcanic

Province samples only and Monaro samples including the Delegate breccia pipe xenoliths. FeO = total

iron. Mg# calculated following Equation 3 in methods section 4.3.

Lovering and White, (1969)

Rock 2pG 2pG 2pG GG GG Ec

Sample R18 R52 R112 R130 R46 R11

SiO2 44.46 47.6 51.12 45.93 45.51 45.09

TiO2 0.74 0.33 0.06 0.56 1.96 1.26

Al2O3 17.46 18.17 16.4 16.97 16.58 12.53

FeO 9.02 4.18 4.82 5.8 6.03 8.21

MnO 0.22 0.12 0.15 0.17 0.19 0.23

MgO 10.16 10.18 8.34 7.97 7.57 10.12

CaO 12.72 14.73 11.22 11.96 11.88 12.37

Na2O 0.33 1.19 2.99 3.21 3.1 2.02

K2O 0.53 0.03 0.43 0.21 0.23 0.17

P2O5 0.15 0.09 0.15 0.47 0.76 0.34

Mg# 66.75 81.25 75.52 71.01 69.11 68.72

Rock

Sample

Griffin & O’Reilly, (1986)

2pG

10430/1

Rudnick

and

Presper,

(1990)

Rudnick and

Fountain,

(1995)

Average wt.

%

(MVP

xenoliths)

Average wt.

%

(This study)

SiO2 46.85 52.0 53.4 48.74

48.48

TiO2 1.72 1.13 0.82 0.86 0.87

Al2O3 16.45 17.0 16.9 18.06 17.94

FeO 11.83 9.08 8.57 8.90 8.72

MnO 0.13 0.15 0.10 0.17 0.16

MgO 7.87 7.21 7.24 8.67 8.92

CaO 11.04 10.28 9.59 11.58 12.09

Na2O 2.78 2.61 2.65 2.57 2.44

K2O 0.28 0.54 0.61 0.37 0.29

P2O5 0.27 0.13 0.10 0.10 0.10

Mg # 54.26 58.6 60.09 63.46 64.58

Page 37: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

31

Variation diagrams for major elements plotted against Mg# are shown in Figures 9A-

9H. With an increasing Mg# there is a general decrease in TiO2, FeO, P2O5, Na2O and

K2O, and an increase in CaO, Al2O3 and SiO2. Plots of Mg# vs. K2O and CaO (Figure

9E and 9F), separate the garnet and the non-garnet bearing samples. The eclogite has a

high CaO and low Al2O3 and SiO2 compared to the other xenoliths in this study.

Published values from similar rock types (Lovering and White, 1969), are also plotted

on these diagrams. The two pyroxene granulites R112 and R18 in Figures 9E and 9F do

not plot within the non-garnet bearing as do the samples from this study. With literature

values plotted, correlation trends with Mg# become less evident, except Mg# vs. FeO

wt. % (Figure 9D) which still shows a strong negative correlation.

A B

C D

Page 38: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

32

Figures 9A-9H. Major element variation plots showing Mg# vs. SiO2, TiO2, Al2O3, FeO, MnO, CaO,

Na2O, K2O and P2O5. Al2O3 vs. SiO2 and FeO. Garnet granulite =red, two pyroxene granulite =green and

eclogite sample =black. FeO calculated as total FeO and Fe2O3. Mg# calculated using Equation 3 in

methods section 4.3. Clear circle show published values for similar rock types by Lovering and White,

(1969).

E F

G H

Page 39: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

33

5.2.2. Trace element geochemistry

Trace element concentrations for the xenoliths are given in Table 12. Selected trace

elements from xenolith samples are normalised to bulk continental crust (Figure 10),

and plotted against average lower crustal compositions (Rudnick and Presper, 1990;

Rudnick and Fountain, 1995). Trace elements were similarly normalised to mid ocean

ridge basalt (MORB) compositions from Keleman et al., (2003) (Figure 11), and plotted

against typical basalt types. REEs normalised to chondrite are plotted separately and

shown in Figure 12.

Some general trends in the trace element data are observable in both of these plots.

Trace elements in the two pyroxene xenoliths show a greater range than the garnet

granulites. Significant relative enrichments in Ba, Pb, and Sr, and depletions in Nd, Zr

and Hf are shown by most samples excluding MVP10436, MVP10437 and DEL2-

10434. Some notable features include a cluster Sr values showing similar concentrations

across all samples, a considerably greater Ba concentration in DEL2-10431 compared to

other samples, and a strong K depletion in the eclogite sample (DEL2-10434), relative

to the neighbouring elements. Generally, the garnet and non-garnet bearing xenoliths

can be separated by their K and Rb contents.

Most samples, irrespective of major mineralogy show a slight enrichment in LREE

relative to the HREE (LaN/YbN = 0.5-5.2), the exception being sample MVP99-2-22 and

DEL99-2-01. HREE trends are mostly flat (GdN/LuN = 1.0-1.7), and most samples have

a positive Eu anomaly (Eu/Eu* = 0.8– 1.9; Table 13), these being most conspicuous in

the LREE depleted samples. The eclogite sample has a smooth chondrite normalised

pattern with no significant Eu anomaly, and the two pyroxene granulites MVP10436

and MVP10437 have a negative Eu anomaly and show the greatest REE enrichment.

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34

Ta

ble

12

. W

ho

le r

ock

tra

ce e

lem

ent

anal

ysi

s (v

alu

es i

n p

pm

). 2

pG

= t

wo p

yro

xen

e g

ran

uli

te,

GG

= g

arn

et g

ran

uli

te a

nd

Ec

= e

clo

git

e

Ro

ck2p

G2p

G2p

G2p

GG

GG

GG

GG

G2p

GE

c2p

G2p

G

Sam

ple

n

o.

10436

10437

10438

99-2

-08

99-2

-04

99-2

-12

99-2

-13

99-2

-22

DE

L-9

9-2

-

01

DE

L-2

-

10434

DE

L-2

-

10430

DE

L-2

-

10431

Cs

0.0

80.0

80.8

10.1

44

1.2

94.8

0.4

60.4

33.2

90.1

90.6

2

Rb

9.5

83

1.7

7.6

18.3

10.1

11.5

3.9

9.5

2.6

4.1

Ba

80

87

328

63

316

637

770

437

81

527

107

2135

Th

0.1

20.1

40.0

70.1

0.5

30.3

70.2

20.0

70.1

50.7

90.1

90.7

3

U

0.0

60.0

50.0

20.0

20.1

20.0

90.0

50.0

30.0

40.3

20.0

50.1

8

Nb

9.2

28.0

50.3

70.9

13.8

512.1

31.3

1.2

90.9

913.7

42.4

85.4

1

Ta

0.5

90.5

30.0

20.0

60.2

0.6

60.0

70.0

90.0

40.7

0.1

60.2

8

La

13.3

11.9

31.6

42.3

53.5

95.1

11.9

1.5

71.0

28.4

25.4

89.1

9

Ce

34.8

930.9

23.3

74.9

36.5

511.4

33.9

3.9

31.8

820.8

812.3

116.7

9

Pb

3.1

73.1

0.5

50.6

1.0

91.3

20.6

20.5

50.4

30.6

2.1

11.4

5

Pr

5.4

54.8

90.4

90.6

60.8

21.6

20.5

60.6

90.2

63.2

71.7

32.2

Sr

615

655

561

448

548

864

550

445

482

366

424

701

Nd

26.5

623.9

42.4

12.8

23.4

87.3

52.7

74.3

1.4

16.3

77.9

69.5

1

Sm

7.3

76.8

80.7

30.7

60.9

42

0.9

21.9

60.5

34.9

42.4

12.3

4

Zr

103

80

45

11

41

11

32

4106

25

18

Hf

2.5

42.0

20.1

50.1

50.3

41.1

50.3

81.4

10.2

13.0

10.8

70.5

Eu

2.0

81.9

20.4

0.3

80.6

20.8

70.5

51.1

40.3

11.8

10.8

80.9

7

Gd

7.7

77.4

0.8

10.7

81.1

22.1

21.1

12.9

0.7

55.9

42.8

52.4

2

Tb

1.3

1.2

40.1

40.1

30.2

10.3

50.2

0.5

70.1

51.0

50.5

20.3

9

Dy

7.8

37.6

30.9

10.8

61.2

92.2

31.3

63.7

51.0

66.6

3.3

52.4

5

Y

37.9

436.6

24.5

54.3

16.5

210.8

56.9

719.8

95.3

234.0

917.0

513.7

Ho

1.5

71.5

20.1

90.1

80.2

70.4

70.3

0.8

10.2

21.3

90.6

90.5

1

Er

4.0

64.0

30.5

20.4

90.7

11.2

80.8

42.2

50.6

23.6

71.8

71.3

6

Tm

0.5

70.5

50.0

80.0

70.1

0.1

80.1

20.3

20.0

90.5

30.2

70.1

9

Yb

3.3

53.2

30.4

70.4

50.6

41.1

30.7

52.0

50.5

63.2

11.6

61.1

6

Lu

0.4

90.4

70.0

70.0

70.1

0.1

70.1

10.3

10.0

80.4

90.2

50.1

8

Sc

51.5

50.9

36.9

38.8

33.2

49.7

40.5

38.9

39.2

43.1

37.3

39.5

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35

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36

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37

Page 44: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

38

Figure 10. Multi-element plot for xenoliths normalised to bulk continental crust (Rudnick and Gao,

2003). Two pyroxene granulites = green, garnet granulites = red, eclogite = black and bulk lower crustal

compositions = pink. Bulk lower crustal values from Rudnick and Presper, (1990) and Rudnick and

Fountain, (1992).

Figure 11. Multi-element plot for xenoliths normalised to mid ocean ridge basalt (Kelemen et al., 2003).

Xenoliths plotted against average ocean island basalts, oceanic arc basalts and continental arc basalts also

compiled by Kelemen et al., (2003). Two pyroxene granulites = green, garnet granulites = red, eclogite =

black and basalts from Kelemen et al., (2003) = blue.

Figure 12. Rare earth element data from whole rock geochemistry normalised to CI Chondrite

(McDonough and Sun, 1995). Two pyroxene granulites = green, garnet granulites = red and eclogite

black.

Sample Rock type Eu/Eu*

10436

2Py

0.84

10437 2Py 0.82 10438 2Py 1.58 99-2-08 2Py 1.51

DEL-2-10430 2Py 1.03 DEL-2-10431 2Py 1.24 DEL-99-2-01 2Py 1.49 99-2-04 GG 1.85

99-2-12 GG 1.29 99-2-13 GG 1.65 99-2-22 GG 1.45 DEL-2-10434 Ec 1.02

Rudnick and Presper, (1990) Bulk lower crust 1.05 Rudnick and Fountain, (1995) Bulk lower crust 1.14

Table 13. Eu/Eu* values calculated using Equation 2 from methods section 4.3. Eu/Eu* for bulk lower

crust calculated using Eu, Sm and Gd values from Rudnick and Presper, (1990) and Rudnick and

Fountain, (1995).

5.2.2.1. Normalisation to bulk continental crust

Normalisation to bulk continental crust shows a general depletion in most trace

elements except Sr, which is enriched in all samples. Ta, Nb and Ti enrichments are also

observed, possibly reflecting the presence of rutile. Lower crustal compositions,

inferred from these xenoliths suggest a greater depletion in radiogenic elements (Th, U)

and a strong Ba enrichment compared to the bulk lower crustal compositions (Rudnick

and Presper, 1990; Rudnick and Fountain, 1995).

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39

The Ta/Nb ratio in lower crustal averages based on mafic xenolith compositions

(Rudnick and Presper, 1990), is similar to that of xenoliths analysed in this study. The

Ta/Nb ratio in lower crustal averages by Rudnick and Fountain, (1995) on the other

hand, which are derived mainly from exposed granulite terranes and seismic profiling

show a lower Ta/Nb ratio. The Sr abundance in average lower crustal compositions is

similar to compositions of the bulk continental crust, both of which are slightly lower

than the Sr content in the analysed xenoliths.

5.2.2.2. Normalisation to mid ocean ridge basalts (MORB)

Compared to MORB compositions these granulite xenoliths show an enrichment in Ba,

Sr, Pb and depletion in U, Ta, Nb, Zr and Hf (Figure 12). MORB-normalised trends are

clearly distinct from ocean island basalts, however, show similar trace element

characteristics to oceanic and continental arc basalts. The Ta and Nb depletions relative

to La are characteristic of typical arc basalts and emphasise these similarities. Most

xenoliths are depleted in Th, U, Pb, Zr and Hf, and are enriched in Ba relative to both

the ocean island basalts and arc basalts. The flat HREE pattern of the xenolith samples

is similar to that of MORB and arc basalts, although lack any Eu anomaly or REE

fractionation observed in these xenoliths. The eclogite sample (DEL2-10434), does not

show the same characteristic as the two pyroxene and garnet granulites. It has a smaller

enrichment in Ba and Sr, and generally displays a much flatter trend compared to the

other rock types.

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40

5.3. Mineral/whole rock concentration ratios

Trace element concentrations in clinopyroxene, orthopyroxene, plagioclase, garnet and

rutile, were divided by their abundance in the corresponding whole rock sample

(Equation 1 in methods section 4.3). These values, referred to as concentration ratios

(CX/WRi ) can be compared with known mineral-melt partition coefficients in basaltic

rocks and are plotted in Figures 13A-13E. High concentration ratios (C>1) indicate that

trace element concentrations in individual minerals are greater than their concentration

in the whole rocks. Average values for each mineral were calculated, given the small

variation of trace elements within and between the same mineral phase of a given

xenolith sample.

Clinopyroxene in the two pyroxene granulites contain concentration ratios Ccpx >1 for

elements Ni, Cr, Hf, Sc, Zr, Y and the REEs (Figure 13A). The garnet granulites and

eclogite sample show similar concentration ratios in clinopyroxene, apart from a strong

depletion in the HREEs (Ccpx <1) reflecting the presence of garnet. Experimental

mineral-melt partition co-efficients in clinopyroxene (Arth, 1976; Fujimaki et al., 1984)

show an enrichment in Th, U, Nb, Ta, Sr, Ni, Cr and the HREEs, relative to the

concentration ratios of clinopyroxene in these xenoliths (Figure 13A). Trace elements in

orthopyroxene on the other hand, show similar trends between the calculated

concentration ratios and the experimental partition coefficients by Arth, (1976) (Figure

13B). This reflects the minimal input orthopyroxene has on the trace element budget of

the whole rock compositions, and of basaltic rocks in general.

Plagioclase in these samples, particularly in the two pyroxene granulites, show similar

trace element concentration ratios to the experimental partition coefficients from Arth,

(1976) and Fujimaki et al., (1984) (Figure 13C). With the exception of the strong

depletions in Zr, Hf and Nb, concentration ratios for plagioclase in these xenoliths are

typical of crystallising plagioclase from a basaltic melt.

Experimental partition coefficients for trace elements in garnet from Johnson, (1998),

Hauri et al., (1994) and Irving and Frey, (1978), are shown in Figure 13D.

Concentration ratios for garnet in these xenoliths are slightly depleted in Ba and Sr, and

significantly more depleted in Nb compared to the partition coefficients for garnet in a

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41

basaltic melt. Garnet also lacks a strong Hf depletion, and show a greater depletion in

the LREEs relative to the HREEs compared to experimental partition coefficients.

Concentration ratios of rutile in these samples are depleted in most elements except U,

Nb, Ta, Hf, Zr. Partition coefficients for rutile in basaltic rock were available for Nb,

Ta, Hf and Zr, and are plotted against the calculated concentration ratios in Figure 13E.

Rutile in these samples, particularly in the garnet granulites show a greater enrichment

in Nb, Ta, Hf and Zr compared to the experimental partition coefficients by Bennett et

al., (2004) and Klemme et al., (2005). Sample MVP99-2-12 also shows a greater Nb/Ta

vs. Zr/Hf fractionation relative to rutile in samples MVP99-2-22 and DEL2-10434.

0.00

0.01

0.10

1.00

10.00

Rb Th U Ta Nb La Ce Sr Nd Zr Hf Sm Eu Gd Dy Y Er Yb Lu Ni Cr

Min

eral/

wh

ole

rock

Clinopyroxene

MVP10437

MVP10438

DEL99-2-01

MVP99-2-12

MVP99-2-22

DEL2-10434

Experimental partition coefficients

Figure 13A. Concentration ratios plotted against experimental mineral/melt partition coefficients for

clinopyroxene. Experimental partition coefficients from Arth, (1976) and Fujimaki et al., (1984).

Page 48: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

42

0.001

0.010

0.100

1.000

Nd Zr Sm Eu Gd Dy Y Er Yb Lu

Min

eral/

wh

ole

rock

Orthopyroxene

MVP10437

MVP10438

DEL99-2-01

Experimental partition coefficients

0.000

0.001

0.010

0.100

1.000

10.000

Rb Ba Th U Nb La Ce Sr Nd Zr Hf Sm Eu Gd Dy Y Er Yb Lu

Min

eral/

wh

ole

rock

Plagioclase

MVP10437 MVP10438

DEL99-2-01 MVP99-2-12

MVP99-2-22 Experimental partition coefficients

Figure 13B. Concentration ratios plotted against mineral/melt partition coefficients for

orthopyroxene. Experimental partition coefficients from Arth, (1976).

Figure 13C. Concentration ratios plotted against mineral/melt partition coefficients for

plagioclase. Experimental partition coefficients from Arth, (1976) and Fujimaki et al.,

(1984).

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43

0.0000

0.0001

0.0010

0.0100

0.1000

1.0000

10.0000

Rb Ba Th Nb La Ce Sr Nd Zr Hf Sm Eu Gd Dy Y Er Yb Lu

Min

era

l/ w

ho

le r

ock

Garnet

MVP99-2-12

MVP99-2-22

DEL2-10434

Experimental partition coefficients

1

10

100

1000

Nb Ta Zr Hf

Min

eral/

Wh

ole

rock

Rutile

MVP99-2-12

MVP99-2-22

DEL2-10434

Experimental partition coefficients

Figure 13D. Concentration ratios plotted against experimental mineral/melt partition

coefficients for garnet (Johnson, 1998; Hauri et al., 1994; Irving and Frey, 1978).

Figure 13E. Concentration ratios plotted against mineral/melt partition coefficients.

Elements above detection limits are plotted. Experimental partition coefficients from

Bennett et al., (2004) and Klemme et al., (2005).

Page 50: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

44

5.4. Zircon mineralogy

Reflected and transmitted light microscopy, and BSE and CL imaging was carried out

on individual zircon grains in the xenolith samples before and after mineral separation.

Zircon grains range from 50 -200µm in size (Figure 14A-14F). Their morphology is

variable, ranging from rounded to elongate to irregular shapes dictated by the geometry

of adjacent minerals. In thin section, zircon exists as inclusions in the major minerals

(Figures 14A, 14B and 14C), and also at the grain boundaries of the major minerals,

particularly ilmenite (Figures 14D, 14E and 14F). These textures show evidence for

zircon crystallisation both before and during/after the formation of the granulite

mineralogy. Internal features observed in CL imaging include irregular zoning patterns,

some sector zoning, and inclusions (Figures 15A – 15F). A generally strong CL

response, observed in these grains is consistent with their low uranium concentrations

(e.g. Kroner et al., 1987). The 206Pb/238U mean weighted ages added on these grains

show no relationship between microstructures or size of the zircons.

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45

Figure 14A-14F. In situ zircon imaging of sample MVP10436. A.Transmitted light (PPL) zircon in

plagioclase x 5 Magnification. B. Transmitted light (PPL) zircon in plagioclase x 20 Magnification. C.

BSE image of zircon inclusion in plagioclase (1812 x Mag, 15kV, WD 10mm). D. Transmitted light

(PPL) zircon in contact with plagioclase, ilmenite and clinopyroxene. E. BSE image of image D (Mag

1472 x, WD 10mm, 15Kv). F. Deformed zircon between clinopyroxene and Ilmenite (Mag 710 x, 15kV,

WD 10mm). Abbreviations follow Kretz, (1983).

A B

C D

E F

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46

Figures 15A-15F. CL images of zircon grains for sample MVP10437 (A-C), and sample MVP10436 (D-

F). 206Pb/238U mean weighted ages for individual SHRIMP pits are included (see Table 6 in section 4.4.5

in methods for selection criteria). Ages represent the majority, but not all analyses – for the purpose of

relating ages to microstructures.

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47

5.5. U-Pb (SHRIMP II) age determinations- Monaro Volcanic Province xenoliths

Seventeen spot analyses were conducted on eleven zircon grains from MVP10437, and

eighteen spot analyses on fifteen zircon grains from MVP10436 (Appendix 7). The

uranium content in samples MVP10436 and MVP10437 are variable, ranging from 23-

465 ppm, and 27-454 ppm respectively. The common lead corrected 206Pb/238U ages

from the zircons in these xenoliths vary from 375 ± 11.3 Ma to 439 ± 16.7 Ma for

MVP10436 and 352 ± 6.3 Ma to 428 ± 9 Ma for sample MVP10437.

Eleven analyses from the TEMORA-2 zircon standard yield a concordia age of 414 ±

4.8 Ma (Figure 16A), and mean weighted ages (Figure 16B) within analytical

uncertainty of the recommended 416.8 ± 0.3 Ma value from Black et al., (2003).

Weighted age averages provided a selection criteria to identify populations of data to

calculate concordia ages for the xenolith samples. These plots showed less variability in

the distribution of age data from sample MVP10436 (Figure 17A) compared to

MVP10437 (Figure 18A).

Sample MVP10436 produced a U-Pb concordia age of 419.4 ± 6.6 Ma based on the

observed cluster of data, and rejecting four analyses with low 206Pb/238U ages attributed

to lead loss (Figures 17B and 17C). Data from sample MVP10437 (Figure 18B) showed

a greater spread along concordia compared to sample MVP10436. The interpretation of

these data is therefore less straightforward. This spread may be interpreted as complete

lead loss, and therefore, none of these data ellipses are representative of the true zircon

age, or alternatively, zircons may have undergone partial lead loss, and the oldest group

of data represents the true zircon age. If the second scenario is true, a U-Pb concordia

age can be calculated from the oldest cluster of data which gives an age of 402.5 ± 6.3

Ma (Figure 18C).

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48

Figure 16A. Terra-Wasserburg concordia plot in the TEMORA-2 zircon standards 414 ± 4.8 Ma. (2s,

decay-constant errors included).

Figure 16B. 206Pb/238U results from the TEMORA-2 zircon standard. Mean weighted ages calculated to

95% confidence. 0 of 11 rejected.

385

395

405

415

425

435

445

455

206P

b/2

38U

Ag

es (

Ma

)

box heights are 1sMean age = 413.0 ± 4.8 Ma

MSWD = 0.71

Probability of fit = 0.72

0.049

0.051

0.053

0.055

0.057

0.059

0.061

12.5 13.5 14.5 15.5 16.5

207P

b/2

06P

b

238U/206Pb

TEMORA-2

Age = 414.0 ±4.8 Ma

MSWD = 1.9

Probability = 0.17

data-point error ellipses are 68.3% conf.

380

420

460

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49

Figure 17A. 206Pb/238U results from sample MVP10436. Ages calculated to 95% confidence,

including error in standard deviation. 4 of 18 rejected.

330

350

370

390

410

430

450

470

206P

b/2

38U

Ag

es (

Ma

)

box heights are 1s

MVP10436

Mean Age = 419 ± 4.9 Ma

MSWD = 1.19

Probability = 0.28

0.045

0.055

0.065

0.075

11 13 15 17 19

207P

b/2

06P

b

238U/206Pb

MVP10436 data-point error ellipses are 68.3% conf.

350

450

550

Figure 17B. Tera - Wasserburg diagram showing ellipses for all spot analysis of zircons in

the two pyroxene xenolith MVP10436. Red ellipses are excluded from the U-Pb concordia

age calculation.

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50

330

350

370

390

410

430

206P

b/2

38U

Ag

es (

Ma

)

box heights are 1s

MVP10437

Mean age = 400.5 ± 9.6 Ma

MSWD = 3.0

Probability = 0.001

0.046

0.050

0.054

0.058

0.062

12 13 14 15 16 17

20

7P

b/

20

6P

b

238U/206Pb

MVP10436 data-point error ellipses are 68.3% conf.

360400

440

480

Concordia age = 419.4 ±6.6 Ma

MSWD = 1.05

Probability = 0.31

N = 14 of 18

Figure 17C. Tera – Wasserburg concordia plot, excluding values with suspected Pb loss shown

from 19A. Concordia age is calculated at 419.4 ±6.6 Ma at 95% confidence, including decay-

constant errors.

Figure 18A. 206Pb/238U results from sample MVP10437. Ages calculated to 95% confidence,

including error in standard deviation. 6 of 17 rejected.

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51

Figure 18B. Tera – Wasserburg diagram showing ellipses for all spot analysis of zircons

in the two pyroxene xenolith MVP10437.

Figure 18C. Tera – Wasserburg concordia plot of a possible population of concordant data from

Figure 18B. Age is calculated to 95% confidence, including decay constant errors.

0.04

0.05

0.06

0.07

0.08

13.5 14.5 15.5 16.5 17.5

20

7P

b/2

06P

b

238U/206Pb

MVP10437

Concordia age: 402.5 ±6.3 Ma

MSWD = 0.13,

Probability = 0.72

N= 11 of 17

data-point error ellipses are 68.3% conf.

370410450

340380420460

0.04

0.05

0.06

0.07

0.08

13 15 17 19

207P

b/2

06P

b

238U/206Pb

MVP10437 data-point error ellipses are 68.3% conf.

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52

5.6. Comparison of the dated xenoliths to the Delegate breccia pipe xenoliths

The dated xenoliths in this study from the Monaro Volcanic Province (MVP10436 and

MVP10437), and the previously dated Delegate breccia pipe xenoliths by Chen et al.,

(1998) (sample 10430/1) resemble a two pyroxene mineralogy and are geochemically

identical. These samples are geochemically distinct from the non-zircon bearing two

pyroxene granulites. Major element comparisons are presented in Table 11 from section

5.2.1, and available trace elements are provided in Table 14 below.

Table 14. Available trace element comparison between samples from Griffin and O’Reilly, (1986)

(10430/1) and this study (MVP10436 and MVP10437).

Zircon U-Pb concordia ages from the previously studied Delegate xenoliths (using ID-

TIMS) were 398 ± 2 Ma and 391 ± 2 Ma (Chen et al., 1998). The low U concentration

in zircon meant that multiple grains needed to be dissolved together to provide enough

pictograms of Pb for the analyses. Grain fractions for ID-TIMS were selected based on

grains showing a similar morphology as described in Chen et al., (1995). These ages are

younger than the SHRIMP 419.4 ± 6.6 Ma from sample MVP10436 in this study,

however, show a closer relationship with the more obscure 402.5 ±6.3 Ma ages from

sample MVP10437 which showed a spread of data along concordia in Figure 18B.

5.7. Age comparison to the regional lithological units

The 419.4 ± 6.6 Ma U-Pb zircon age from sample MVP10436 is within the ages of the

I-type granites of the Berridale Batholith (Ickert and Williams, 2011), and Bega

Batholith (Chen and Williams, 1990). Unlike sample MVP10436, the 402.5 ±6.3 Ma

age produced by sample MVP10437 does not fall within the ages of the regional

granites, although both ages are significantly older than the Monaro Volcanic Province

alkali basalt pipes, of which they are hosted in (55-34 Ma; Wellman and McDougall,

1974b). The ages of the lithological units near the xenolith pipe localities are

summarised here in Table 15 for comparison with the zircon ages from these xenoliths.

10430/1 MVP10436 MVP10437

Rb 9.1 9.5 8

Sr 602 615 655

Y 41 37.94 36.62

Zr 62 103 80

Nb 9 9.22 8.05

Ba 86 80 87

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Rock type Dating method Age & reference

Two pyroxene granulite xenoliths

(Monaro Volcanic province).

Zircon U-Pb

(SHRIMP)

419.4 ± 6.6 Ma (this study

MVP10436)

402.5 ±6.3 Ma (this study

MVP10437)

Two pyroxene granulite xenoliths

(Delegate breccia pipes)

Zircon U-Pb

(IDTIMS)

398 ± 2 Ma (Chen et al., 1998)

391 ± 2 Ma (Chen et al., 1998)

Breccia pipes (Delegate) K-Ar 160-170 Ma (Lovering and

Richards, 1964; White and Chappell,

1989)

Alkali basalt pipes (Monaro)

K- Ar 55-34 Ma (Wellman and

McDougall, 1974b)

Berridale Batholith: I Type granites.

Zircon U-Pb

(SHRIMP)

412.6 ± 4.1 Ma – 436.2 ± 4.7 Ma

(Ickert and Williams, 2011).

(Majority ~417 Ma)

Berridale Batholith: S Type granites. Zircon U-Pb

(SHRIMP)

425.5 ± 4.3 to 435.6 ± 5.1 Ma

(Ickert and Williams, 2011)

(Majority ~ 432 Ma)

Delegate Adamellite pluton (I-type)

(within Berridale Batholith)

Zircon U-Pb

(SHRIMP)

419.2 ± 6 Ma (Ickert and Williams,

2011).

Glenbog Granodiorite (Bega

Batholith)

Zircon U-Pb

(SHRIMP)

412 ± 3 Ma and 414 ± 2 Ma (Chen

and Williams, 1990)

Buckleys Lake Adamellite

(Berridale Batholith)

Zircon U-Pb

(SHRIMP)

415.6 ± 4.4 Ma (Ickert and

Williams, 2011).

Tingaringy Granodiorite

(Berridale Batholith)

Zircon U-Pb

(SHRIMP)

425.5 ± 4.3 (Ickert and Williams,

2011).

Table 15. Summary of geological units of the eastern Lachlan Fold belt in close proximity to the xenolith

samples.

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6. Discussion

6.1. Origin of xenoliths from the Monaro Volcanic Province

Mafic xenoliths of lower crustal derivation may represent (1) cumulates from mantle

derived magmas (e.g. Rogers and Hawkesworth, 1982), (2) restites following partial

melt extraction (e.g. Rudnick, 1986; Rudnick and Taylor, 1987), (3) crystal cumulates

related to their host basalts (e.g. White, 1966), or (4) a combination of these.

The MVP xenoliths show strong preservation of the original cumulate textures (see

Appendix 1). Such features imply a cumulate origin, however, the metamorphic

mineralogy and granulitic textures of these xenoliths suggest they are not direct igneous

cumulates. Samples may also represent orthocumulates with trapped melt phases

(Arculus et al., 1989), which under granulite facies conditions, would be difficult to

distinguish texturally and without geochemical data. Bearing in mind these observed

textural features, the mineral specific trace element chemistry, whole rock

geochemistry, and zircon U-Pb geochronology are discussed in this section to

distinguish melt and crystallisation phases, and understand the crustal growth history

preserved in these samples.

6.1.1. Evidence from trace element geochemistry

Major element compositions provide supporting evidence for a mafic lower crust

composed of predominantly basaltic material. The trace element compositions are

indicative of gabbroic cumulates, exhibiting large positive Sr anomalies and moderate

positive Eu anomalies (Rogers and Hawkesworth, 1982).

Samples are generally depleted in trace element concentrations relative to average lower

crustal compositions, particularly Th, U, Nd, Hf and Sm. These depletions are

characteristic of the mafic lower crust, produced by differentiation of a basaltic magma,

melt loss from cumulates (Rudnick, 1992), or reflecting, at least in part, a pre-existing

feature of the original magma (Roberts and Ruiz, 1989). While low concentrations of

Rb, Zr, Hf and Nd are characteristic of basaltic rocks, significant depletions in these

elements, along with enrichments in Ba, Sr and Pb (shown in Figure 11) are not typical

of common basaltic melts.

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55

These signatures suggest that the MVP samples are more complex than simply

representing crystallised basalts under granulite facies conditions, and attest to the

fractionation and/or partial melting in these xenoliths. Strong Nb and Ta depletions

relative to La (Figure 12), observed in these samples is similar to arc magmas, and

suggest subduction zone magmatism may have influenced the compositions of these

xenoliths. While the exact origin of Nb and Ta depletions in the crust still remain

enigmatic (Hermann and Rubatto, 2009), signatures retained from the partitioning of Nb

and Ta into rutile during subduction of oceanic crust are thought to be preserved in

newly formed continental crust. The enrichment and limited concentration range of Sr

reflects the accumulation of plagioclase, however may also be sourced from processes

such as, subduction and recycling (e.g. Sobolev et al., 2000), additions to the lower

crust by mantle degassing (Korringa and Noble, 1971), or contamination with the host

pipe (e.g. Mitchell and Crocket, 1971).

The smooth REE pattern, slight depletion towards the HREEs and positive Eu anomaly

is suggestive of a cumulate origin (Rogers and Hawkesworth, 1982). The zircon bearing

xenoliths (MVP10436 and MVP10437) are geochemically distinct from the non-zircon

bearing two pyroxene granulites. They are enriched in trace elements, particularly the

REEs and characterised by a negative Eu anomaly, more representative of a partial or

extracted melt (e.g. Rudnick et al., 1986; Rudnick, 1992).

Partition coefficients of trace elements within minerals of naturally occurring melts are

derived from experimental results on basaltic rocks and compared to mineral/whole

rock trace element ratios from these xenoliths. The mineralogy and distinct cumulate

layering in these xenoliths suggest the study samples are not basaltic melts, and

significant differences in comparison to experimental values may reflect their

crystallisation and melt history, the accumulation of specific mineral phases (e.g. Frey

and Prinz, 1978), their crustal origin and tectonic setting. While comparisons are made

between similar rock types, it should be noted that variations in mineralogy may also

affect these values.

The mineral chemistry and concentration ratios of plagioclase show enrichments in Ba,

Sr and Eu, elements considered to be compatible in plagioclase crystallising from a

basaltic melt (Arth, 1976). Samples MVP10436 and MVP10437, illustrating whole rock

geochemical characteristics of a melt fraction, still show these enrichments in

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56

plagioclase (Figure 3A and 3B, and 13C), and therefore, may have originally

represented cumulates undergone partial melting. If plagioclase crystallised as an

interstitial melt rather than by crystal accumulation, the mineral/whole rock ratios of

other elements apart from Ba, Sr and Eu, may also be enriched.

Positive concentration ratios of Ni and Cr in clinopyroxene show no enrichment relative

to other trace elements, suggesting clinopyroxene did not form by crystal accumulation

as shown by plagioclase. The greater HREE depletion of clinopyroxene within the

garnet bearing samples suggest the crystallisation or recrystallisation of clinopyroxene

in equilibrium with garnet. The flat HREEs are characteristic of garnet under granulite

conditions (e.g. Rubato, 2002) and provide evidence for sub-solidus re-equilibration

under granulite conditions as suggested by Chen et al., (1998). Together with a

cumulate interpretation for these samples (as indicated by plagioclase), garnet is

understood to have grown during granulite facies metamorphism of a basaltic cumulate.

Rutile is an essential component of geochemical signatures in arc magmas (Foley et al.,

2000), and is considered to be a primary mineral causing fractionation in high field

strength elements (Nb, Ta, Hf, Zr) (Ayers and Eggler, 1995; Brenan et al., 1995b; Ayers

et al., 1997; Adam et al., 1997; Stalder et al., 1998). Rutile in these xenoliths are

significantly enriched in high field strength elements Nb, Hf, Ta, and Zr, and these

elements, particularly Nb and Ta are highly compatible in crystallising rutile (Bennett et

al., 2004). The greater enrichment of these elements indicated by the whole rock

chemistry in sample MVP99-2-12 over MVP99-2-22, suggests MVP99-2-22 has

undergone a greater degree of differentiation than MVP99-2-12 and potentially derived

from a more fractionated arc magma.

6.1.2. Evidence from zircon analysis

6.1.2.1. Textural context and microstructures

Understanding the origin of these xenoliths using U-Pb geochronology of zircon

requires knowledge of how the zircon formed, and essentially, how these grains relate to

the major mineralogy. Before assigning geological significance to U-Pb ages, textural

and microstructural features of the zircon grains are discussed.

The microstructures and morphology of the zircons in the granulite samples are

characteristic of metamorphic zircon (e.g. Kroner et al., 1987). Fewer zircons show a

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57

more rounded version of the classical prismatic shape, a common feature of

metamorphic zircons in fluid-rich environments (Corfu et al., 2003). The intergrowth of

zircon, often in contact with ilmenite suggests a relationship between the two minerals.

Exsolution lamellae in ilmenite, consistent with the incipient breakdown of this mineral,

may suggest ilmenite is a possible source of Zr for metamorphic zircon growth in the

granulite facies (e.g. Bingen et al., 2001), although this interpretation was made by

observation of a zircon rim around ilmenite, a feature that is not observed in these

samples. Zircon only occurs in samples MVP10436 and MVP10437. These xenoliths

are both characterised by REE enrichment and have undergone greater degrees of

differentiation to produce the elevated Zr contents required to crystallise zircon.

6.1.2.2. Geochronology

The dated xenoliths at 419.4 ± 6.6 Ma (sample MVP10436) and 402.5 ± 6.3 Ma (sample

MVP10437) are significantly older than the alkali basalt pipes of the Monaro Volcanic

Province (55-34 Ma; Wellman and McDougall, 1974b), and the Delegate breccia pipes

(160-170 Ma; Lovering and Richards, 1964), and therefore unrelated to the host magma.

The zircon ages cannot distinguish between a residual or cumulate origin, however, do

provide strong evidence that samples are not fragments of the host pipe basalts (e.g.

White, 1966).

The two pyroxene granulite (10430/1) from the nearby Delegate breccia pipes produced

ID-TIMS ages of 391 ± 2 Ma and 398 ± 2 Ma by Chen et al., (1998), and are

comparable to the 402.5 ± 6.3 Ma ages from sample MVP10437. The spread of data

along concordia shown by sample MV10437 may be due to intracrystalline Pb loss

and/or the redistribution of Pb, common in high-grade metamorphism (McFarlane et al.,

2005). This would imply that this younger age does not have geological significance, in

which case these data provide little information regarding the xenolith origin. The tight

cluster of concordant ages obtained from zircons in sample MVP10436 on the other

hand, and their age similarity with the late Silurian regional granites (Ickert and

Williams, 2011), suggest that this sample formed during the emplacement of the

Lachlan Fold Belt batholiths. It cannot be ruled out that the zircon grains formed prior

to metamorphism. It is important to note that granulite facies conditions denoted by

these samples exceed the closure temperature for the U-Pb Zircon geochronometer

(Cherniak and Watson, 2001). It is possible that zircons are older than their determined

U-Pb age and represent magmatic zircons which have been isotopically reset by the host

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pipe volcanism or by a separate magmatic event (e.g. Bomparola, 2007). This is,

however, not supported by the REE signatures and grain morphology which suggest

zircon crystallised under granulite facies conditions.

6.2. Implications for crustal evolution

6.2.1. Relationship with regional granites

The mafic compositions of these xenoliths are broadly complementary to the more

felsic upper crustal granites of the eastern Lachlan Fold Belt (Chappell and White,

1992). Similarly, the positive Eu anomaly in majority of these xenoliths complement the

negative Eu anomaly in the Lachlan granites and the post Archean upper continental

crust in general (Taylor and McLennan, 1995). A positive Eu anomaly estimated for the

Earth’s lower crust is often considered to be complementary to the negative Eu anomaly

established for the Earth’s upper crust (Rudnick and Gao, 2003). This positive Eu

anomaly is, however, too small to satisfy this complementary relationship. The mass

balance discrepancy is either an indication of the limited lower crustal material available

for sampling, a lower crust that is not a direct residue of the upper crust, or some other

undetermined process. The MVP samples provide evidence that a more Eu-rich lower

crust exists, which could also help this mass balance problem.

The Monaro Volcanic Province xenoliths have a discrete zircon population producing a

U-Pb concordia age of 419.4 ± 6.6 Ma. In contrast, the previously dated Delegate

breccia pipe xenoliths (Chen at al., 1998) showed no age relationship with any of the

late Silurian regional granites. The U-Pb zircon age from sample MVP10436 reported in

this study, delivers the first geochronological evidence linking the unexposed granulitic

lower crust to the upper crustal granites of the Lachlan Fold Belt. This age association,

along with the trace element signatures exhibited by these xenoliths, implies that crustal

growth is a product of subduction related magmatism, and has significant implications

for understanding crustal processes at inaccessible depths. These may include the timing

of large scale basaltic magmatism and deep fractionation processes, which may provide

important information for the production of the granitic upper crust.

The significance of the younger 402.5 ± 6.3 Ma age can only be assessed by further

isotope analysis, however, if ages were related to separate magmatic events, this would

provide evidence that basaltic magmatism and underplating was episodic, and continued

after the formation of the late Silurian granites of the eastern Lachlan Fold Belt. Such a

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59

process is considered imperative for the strengthening and stabilisation of the

continental crust (Rudnick, 1995).

6.2.2. Implications of the Lachlan Fold Belt/Tasmanides evolution - evidence from

xenoliths

The Lachlan Fold Belt has been the focus of extensive geophysical, tectonic and

petrological research (e.g. Collins and Vernon, 1992; Gray and Cull, 1992; Collins,

1998). Its evolution is important in understanding the development of the larger Terra

Australis Orogen, a series of orogenic belts recording the formation of crust along the

eastern margin of Gondwana during the Palaeozoic (Glen, 2005). Information about the

lower crust below this region is limited to xenoliths and seismic profiling, making a

complete understanding of crust-forming processes in this orogen, and particularly the

processes of granitic magma generation, elusive.

During the Silurian to Mid-Devonian, the southern Tasmanides developed a large back-

arc basin as part of the Tabberabberan cycle, and underwent lithospheric extension

caused by roll back of the southern proto-Pacific plate (Glen, 2005). The distribution of

the I-type granites over the S-type in the eastern Lachlan Fold Belt is considered to be a

result of this thinning and extension of the back-arc, following S-type granite plutonism

(Collins and Richards, 2008). Figure 19 shows a model for the S and I-type granite

formation in a subduction zone setting by Collins and Richards, (2008). In the context

of this study, these figures highlight the relationship between basaltic intra/under

plating, the mafic granulitic lower crust and the formation of the I-type granites during

back-arc extension. Following this model, xenoliths representing fragments of the lower

crust, and produced by basaltic magmatic cumulates, show a closer age relationship

with the I-type granites as opposed to the S-type granites shown in Table 15.

The xenoliths of this study represent highly equilibrated granulite textures, and as a

result, evidence from any deformation features (i.e. foliation or deformation

microstructures) which could point towards the wider tectonic setting are absent.

However, complex disequilibrium textures and multiple coronae textures identified in

Part 1 of this study (Appendix 1), provided evidence for isobaric cooling and a dynamic

lower crustal environment.

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The trace element compositions of these xenoliths are depleted in radioactive heat

producing elements, as expected for the deep crust beneath the I-type granites, and

lower crustal material in general (Sawka and Chappell, 1986; Collins and Hobbs, 2001).

Furthermore, xenoliths show geochemical signatures similar to those of arc basalts,

suggesting the origin of the source magma may be associated with a subduction setting

rather than an intraplate oceanic magma protolith (Griffin and O’Reilly, 1986). The

xenolith geochemistry and age association with the I-type granites provide a significant

relationship for understanding the evolution of the regional granites. The I-type granites

also have a subduction related chemistry, and are understood to be derived from mid to

deep crustal sources as a result of underplating by mafic magmas during extension

(Chappell and White, 1992). Both the geochemical and geochronological data from

these xenoliths provide evidence supporting the proposed model of I-type granite

formation by Collins and Richards, (2008), and supports most crust forming

mechanisms consisting of a mafic lower crust/mantle composition and subduction

component (e.g. Powell, 1983).

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61

Figure 19. Tectonic diagram from

Collins and Richards, (2008) showing

how the mafic lower crust might form

from crustal-scale magmatic events.

Xenoliths represent samples from this

basaltic granulitic lower crust

underneath the exposed I-type

granites.

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6.2.3. Implications for general crust forming processes

The preserved cumulate textures, geochemistry and geochronology collectively point

towards a cumulate origin of these xenoliths, subsequently recrystallised under granulite

facies conditions and significantly different from their host basalt. The basaltic

compositions of the enclaves provide direct evidence for the large amounts of mafic

material beneath eastern Australia (e.g. Chen et al., 1998), and a lower crust consisting

of a granulite and eclogite mineralogy (Foley et al., 2002).These basaltic cumulates

provide key evidence for the addition of new crustal material by magmatic underplating,

typical of subduction zones and intraplate settings during the Palaeozoic (Rudnick et al.,

1986).

These xenoliths represent samples in which the protolith may have been an igneous

cumulate, but after crystallisation they were metamorphosed to granulite facies. It is

possible that this process of cumulate formation was related to granite generation, as

represented by the Collins and Richard model (Figure 19). The results from this study

not only constrained an age of metamorphism as suggested by Chen et al., (1998), but

were able to relate this age to the regional granites, providing both geochemical and

chronological evidence for a residual and granulitic lower crust during batholith

emplacement (Ickert and Williams, 2001).

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6.3. Conclusions and future research

Conclusions of this study can be summarised as follows:

1. The study samples are basaltic cumulates, formed by the accumulation of

plagioclase during basaltic underplating that subsequently underwent granulite

facies metamorphism.

2. Samples are depleted in heat producing elements (Th, U) characteristic of a

residual lower crust, with some showing a strong REE enrichment and negative

Eu anomaly. These compositions are suggestive of fractionated magma, perhaps

complementary to the depleted granulites.

3. The least fractionated samples on the other hand show a positive Eu anomaly

characteristic of many lower crustal xenoliths, although the presence of samples

with a negative Eu anomaly suggest Eu signatures of the bulk lower crust may

be influenced by sampling bias, or a bulk lower crust that is not a residue

following the extraction of the upper crust.

4. Significant depletions in Nb and Ta suggest subduction processes have

influenced lower crustal compositions, indicating a magmatic provenance

similar to arc basalts beneath eastern Australia.

5. Ion microprobe analysis of zircon from two Monaro Volcanic Province samples

yields a U-Pb concordia age of 419.4 ± 6.6 Ma age contemporaneous with the

emplacement of the Late Silurian I-type granites within the eastern Lachlan Fold

Belt. A second age group was derived from a scatter of data along concordia,

however its significance remains ambiguous.

6. This age relationship provides new evidence for a genetic link between the mafic

and granulitic lower crust, and the more felsic upper crustal granites in eastern

Australia. It further signifies that arc magmatism and magma differentiation are

key processes in the growth and evolution of the continental crust during the

Palaeozoic.

Samples of the granulitic lower crust, in the form of xenoliths provide essential

information regarding the nature and composition of the inaccessible lower crust. The

age association between the regional granites and xenolith samples provide an excellent

opportunity to study isotopic systematics between the upper and lower continental crust.

Future research will focus on S and C isotope signatures in scapolite, along with O and

Lu-Hf isotope analysis in zircon. This may determine if zircon did in fact form during

metamorphism or is magmatic derived, and understand the distribution of stable

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isotopes at deep crustal levels, and their relationship to global isotope reservoirs. These

studies will help reveal critical processes for the evolution of the granitic upper crust

preserved in such xenoliths.

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73

APPENDIX 1 -SUMMARY OF MINERALOGY AND HAND SAMPLE

DESCRIPTIONS (From Part 1 – 2013 thesis)

Appendix Figure 1 Exposed cut surface (on left) and whole rock (on right) representing each rock type.

(A) and (B) two-pyroxene granulite (MVP10438), (C) and (D) garnet granulite (MVP99-2-12), (D) and

(E) Eclogite (DEL2-10434), (F) and (G) reaction intermediate (MVP10435).

B

H

F

D C

E

G

A

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Appendix Figure 2 Optical microscope and BSE images. (A) and (B) are the two–pyroxene granulite in

PPL and XPL, (C) and (D) are the two-pyroxene granulite with scapolite in PPL and XPL, (E) and (F)

rutile and Cpx in PPL and BSE imaging, (F) and (G) show the garnet granulite in PPL and BSE imaging.

A B

G

F E

D C

H

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Appendix Figure 3 (A), (B) and (C) Scapolite in the garnet granulite in PPL, XPL and BSE imaging, (D)

Showing scapolite in garnet granulite which is also in contact with Pl, (E) and (F) show the thick isotropic

rims around garnet of the fassaite eclogite in PPL and BSE imaging.

A B

F E

C D

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Appendix Figure 4 Image (A) displays coronas of Opx rimmed by Cpx, rimmed by Grt in contact with

Pl. Image (B) shows similar coronas but with Grt exsolution lamellae in the centre grain. In (C) Grt rims

in image (A) at higher magnification under BSE imaging. Image (D) shows the instability between calcic

Pl and Cpx. On the right Cpx is rimmed by sodic Pl and on the development of the Grt rim. In (E) and (F)

Spl symplectite occurs as intergrowths with the Grt rims, the darker grain in the BSE image is the altered

sodic Pl. (G) and (H) show larger grains of Spl rimmed by Grt and its common co-existence with

ilmenite.

A

H G

F E

D C

B

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Two-pyroxene granulites

Major mineral assemblage: clinopyroxene + orthopyroxene + plagioclase.

The hand specimens are 6x12cm in diameter and shows compositional banding,

characteristic of cumulate layering (Figures 1a & 1b).

Sample MVP10438 contained scapolite (<2%) as part of its mineral assemblage, DEL99-2-

01 was lacking in scapolite.

The mineralogy of this rock type is variable, comprising of approximately 15% pale brown

to apple green clinopyroxene, 30% pale brown to green and distinctly pleochroic

orthopyroxene and 60% plagioclase.

Scapolite occurs as part of polygonal granular assemblages with pyroxenes. The general

appearance of scapolite is distinguished by its high blue to green birefringence (Figure 2c &

2d).

Accessory minerals are magnetite and rutile. Rutile is bronze under optical microscopy and

characterised by a thin alteration to ilmenite around its edges and as thin plates throughout

the rutile grain (Figure 2e & 2f).

Garnet granulites

Major mineral assemblage: garnet + clinopyroxene + plagioclase ± scapolite ± rutile.

Scapolite and non-scapolite

The hand specimen is 4-5cm in diameter and is grey in appearance (Figure 1c & 1d).

Garnet appears orange/red and is easily observed on the outer weathered surface.

Mineralogy is also variable with clinopyroxene approximately 40%, plagioclase 30% and

garnet 25-30%. Medium to coarse grained similar to the two-pyroxene granulite (0.5-2mm).

In contrast to the two-pyroxene granulite, this assemblage lacks orthopyroxene and contains

garnet (Figure 2g & 2h).

Garnet appears pale brown/pink in thin section and contains a thin alteration around its

edges. The appearance of clinopyroxene and plagioclase under thin section are similar to

the two-pyroxene granulite.

Often scapolite shows high birefringence under cross polarised light and distinct alteration

to plagioclase around its rim. Alteration exists around the scapolite rim but remains within

its grain boundary, suggesting it is not a result of a reaction with the co-existing minerals

Eclogite

Major mineral assemblage: garnet + clinopyroxene with accessory rutile, with rutile

showing alteration to ilmenite around its rim.

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78

Minor mounts of green spinel are present in some of the grain alteration around

clinopyroxene.

The original sample is roughly 10cm in size but appears to be broken from an originally

larger sample (Figure 1f).

The hand specimen shows a coarser grainsize than the other samples, ranging from 1-5mm

(Figure 1e).

Hand sample is dark grey reflecting the lack of plagioclase.

Under thin section, grains appear highly fractured with secondary alteration contained in

these cracks and along edges of the grains. Garnet contains a dark isotropic rim around its

edges (Figure 3e and 3f), interpreted previously as kelyphite, an isochemical breakdown

product of garnet (Keankeo et al., 2000). While present in all garnet grains, this rim is

thickest in the eclogite sample

Only a few garnet grains show the original unaltered, inclusion-free mineral in the centre.

Reaction intermediate

The rock is distinguished from the other samples in displaying several complex reaction

textures.

Sample MVP10435 is a coarse grained rock (average grainsize 1.5mm) and initially appear

to consisting of plagioclase and pyroxene. In hand specimen, grain boundaries are indistinct

compared to previous rock types, reflecting the disequilibrium textures later observed under

optical microscopy.

Sample shows multiple coronae (Figure 4a) with pale brown orthopyroxene in the centre

rimmed by green clinopyroxene that is, in turn, overgrown by garnet. This thin garnet rim is

also in contact with plagioclase, and separates clinopyroxene and plagioclase throughout the

entire sample. Ilmenite is also present in this sample surrounded by a similar garnet rim.

The reaction texture shown in Figure 4b shows a similar texture to that in Figure 4a, except

inclusions of brown, tabular shaped garnet grains occur within the orthopyroxene.

These grains are <50µm in thickness and appear to represent garnet exsolution lamellae, a

product of isobaric cooling (e.g. Becker 1997).

Figure 4c shows a moat of garnet around the central clinopyroxene grain, all which is

surrounded by plagioclase.

Clinopyroxene and calcic plagioclase are never in direct contact.

The boundary between these minerals is separated by a rim of garnet, and in one instance it

is separated by an indistinct rim/halo or sodic plagioclase, as shown in Figure 4d. The grain

on the right contains a rim of sodic plagioclase separating clinopyroxene and calcic

plagioclase. The left grain also shows this rim, but with garnet beginning to develop

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79

suggesting that the formation of the sodic plagioclase is associated with growth of the

garnet rim. Both appear to be products of a reaction involving clinopyroxene and calcic

plagioclase.

Another textural feature of this sample is symplectite intergrowth between garnet and green

(hercynite) spinel (Figure 4e & 4f). This texture appears to be common in garnet rims

surrounding ilmenite and altered sodic plagioclase grains, and does not occur in garnet

rimming orthopyroxene and clinopyroxene. Spinel occurs in two forms, as symplectite

intergrowths within garnet and as larger grains rimmed by garnet (Figure 4g).While the

larger grain appears almost opaque under optical microscopy, the spinel symplectite is dark

green in colour. The opaque appearance may reflect fine intergrowth with ilmenite (Figure

4h) as evident from BSE imaging.

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80

APPENDIX 2 – Original EMPA DATA (From Part 1- 2013 thesis)

SAM

PLE

DEL9

9-2-

01

Spot

12

34

56

78

910

1112

1314

1516

1718

1920

2122

2324

25

MIN

ERAL

Opx

Opx

Cpx

PlPl

Opx

Opx

Cpx

Cpx

PlPl

Opx

Opx

Opx

PlPL

Opx

Cpx

PlCp

xCp

xO

pxO

pxPl

Pl

SiO

2 51

.83

51.8

149

.76

45.8

645

.68

51.6

751

.48

49.5

549

.45

45.5

045

.76

51.6

651

.96

51.7

445

.96

46.1

951

.88

49.7

045

.37

48.6

349

.13

51.3

551

.24

44.1

544

.47

TiO

2 0.

070.

080.

71b.

d.b.

d.0.

070.

080.

730.

66b.

d.b.

d.0.

070.

050.

05b.

d.b.

d.0.

070.

74b.

d.0.

770.

740.

050.

06b.

d.b.

d.

Al2O

3 5.

655.

566.

8633

.69

33.5

95.

395.

586.

776.

6833

.89

33.6

85.

585.

475.

4433

.62

33.8

25.

416.

7133

.81

6.81

6.79

5.61

5.41

33.1

133

.63

Cr2O

3 b.

d.0.

070.

15b.

d.b.

d.0.

060.

110.

190.

12b.

d.b.

d.b.

d.b.

d.0.

11b.

d.b.

d.0.

080.

18b.

d.0.

140.

160.

12b.

d.b.

d.b.

d.

FeO

15

.01

14.5

45.

440.

28b.

d.15

.06

14.6

55.

735.

31b.

d.0.

2014

.35

14.1

714

.02

b.d.

0.29

14.5

55.

45b.

d.6.

155.

7013

.92

13.9

00.

41b.

d.

MnO

0.

320.

230.

11b.

d.b.

d.0.

380.

300.

110.

14b.

d.b.

d.0.

270.

280.

29b.

d.b.

d.0.

250.

13b.

d.0.

160.

180.

340.

27b.

d.b.

d.

MgO

26

.52

26.5

213

.01

b.d.

b.d.

26.6

026

.59

12.9

213

.09

b.d.

b.d.

26.4

926

.65

26.4

3b.

d.b.

d.26

.73

13.3

1b.

d.13

.16

13.2

826

.55

26.5

3b.

d.b.

d.

CaO

0.

270.

1722

.63

17.7

017

.97

0.47

0.54

22.9

122

.45

18.2

118

.23

0.47

0.26

0.28

17.6

417

.76

0.55

22.7

717

.71

22.4

022

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0.38

b.d.

17.4

818

.25

Na2O

0.

040.

020.

801.

631.

520.

03b.

d.0.

850.

831.

361.

480.

020.

03b.

d.1.

611.

62b.

d.0.

801.

440.

810.

820.

030.

041.

501.

36

K2O

b.

d.b.

d.b.

d.0.

020.

04b.

d.b.

d.b.

d.0.

010.

020.

03b.

d.0.

01b.

d.0.

030.

030.

02b.

d.0.

010.

01b.

d.0.

010.

010.

040.

03

P2O

5 b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.

SO

3 b.

d.b.

d.b.

d.b.

d.0.

02b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.0.

04b.

d.

Cl

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

0.01

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

0.01

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

0.05

0.01

TOTA

L99

.72

99.0

099

.47

99.1

998

.81

99.7

399

.32

99.7

598

.76

98.9

799

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98.9

198

.88

98.3

798

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99.7

299

.54

99.8

198

.35

99.0

599

.52

98.3

697

.45

96.7

797

.76

Si

1.86

81.

875

1.84

32.

132

2.13

01.

866

1.86

31.

836

1.84

42.

119

2.12

51.

872

1.88

01.

882

2.14

02.

136

1.87

01.

838

2.12

41.

819

1.82

61.

870

1.87

92.

108

2.10

1

Ti

0.00

20.

002

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00.

000

0.00

00.

002

0.00

20.

020

0.01

90.

000

0.00

00.

002

0.00

10.

001

0.00

00.

000

0.00

20.

021

0.00

00.

022

0.02

10.

001

0.00

20.

000

0.00

0

Al

0.24

00.

237

0.29

91.

846

1.84

60.

229

0.23

80.

295

0.29

41.

860

1.84

40.

238

0.23

30.

233

1.84

51.

843

0.23

00.

292

1.86

50.

301

0.29

80.

241

0.23

41.

864

1.87

3

Cr

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00.

002

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50.

000

0.00

00.

002

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30.

006

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40.

000

0.00

00.

001

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10.

003

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00.

000

0.00

20.

005

0.00

00.

004

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50.

003

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10.

000

0.00

1

Fe

0.45

30.

440

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80.

011

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00.

455

0.44

30.

177

0.16

60.

001

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80.

435

0.42

90.

426

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00.

011

0.43

90.

169

0.00

00.

192

0.17

70.

424

0.42

60.

016

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0

Mn

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007

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30.

000

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00.

012

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90.

003

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50.

000

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10.

008

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90.

009

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00.

000

0.00

80.

004

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00.

005

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60.

010

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80.

001

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1

Mg

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51.

431

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90.

000

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01.

432

1.43

40.

714

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80.

000

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01.

431

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71.

433

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00.

000

1.43

70.

734

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00.

734

0.73

61.

441

1.45

00.

000

0.00

0

Ca

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00.

007

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80.

882

0.89

80.

018

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10.

910

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70.

908

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70.

018

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00.

011

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00.

880

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10.

902

0.88

80.

898

0.90

50.

015

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00.

894

0.92

4

Na

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30.

002

0.05

80.

147

0.13

80.

002

0.00

10.

061

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00.

123

0.13

40.

002

0.00

20.

001

0.14

60.

145

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10.

057

0.13

10.

059

0.05

90.

002

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30.

139

0.12

5

K 0.

000

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00.

000

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10.

002

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00.

000

0.00

00.

000

0.00

10.

002

0.00

00.

001

0.00

00.

002

0.00

20.

001

0.00

00.

001

0.00

10.

000

0.00

10.

001

0.00

20.

002

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000

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00.

000

0.00

00.

000

0.00

00.

000

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10.

001

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00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

10.

000

S 0.

000

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00.

000

0.00

00.

001

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

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000

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00.

000

0.00

00.

000

0.00

00.

000

0.00

00.

000

0.00

10.

000

0.00

00.

000

0.00

00.

000

0.00

00.

001

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10.

000

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00.

000

0.00

00.

000

0.00

10.

004

0.00

1

TOTA

L4.

011

4.00

44.

014

5.01

95.

015

4.01

84.

015

4.02

34.

018

5.01

35.

021

4.00

74.

003

4.00

05.

012

5.01

74.

012

4.02

25.

009

4.03

54.

032

4.00

84.

004

5.03

15.

027

NOX

66

68

86

66

68

86

66

88

66

86

66

68

8

Si C

DL99

0.01

1485

0.01

1934

0.01

015

0.01

2215

0.01

1634

0.01

3626

0.01

4094

0.01

1893

0.00

9323

0.01

2903

0.01

0426

0.00

9079

0.01

2211

0.01

4267

0.01

1916

0.01

1031

0.01

1519

0.01

0891

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9229

0.00

9712

0.01

0955

0.00

9235

0.00

6401

0.01

062

0.01

2827

Ti C

DL99

0.01

9648

0.01

885

0.02

0062

0.01

8666

0.01

9803

0.01

9235

0.01

8802

0.01

984

0.02

0103

0.01

9333

0.01

9114

0.01

9397

0.01

9436

0.01

951

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0007

0.01

9173

0.01

8997

0.01

9732

0.01

9038

0.02

0294

0.02

0157

0.01

9372

0.01

9404

0.01

9464

0.01

9445

Al C

DL99

0.00

9638

0.00

942

0.00

9276

0.01

0419

0.01

0259

0.00

9584

0.00

9426

0.00

9102

0.00

8957

0.01

050.

0102

960.

0095

380.

0095

860.

0095

940.

0099

940.

0101

490.

0094

640.

0093

070.

0102

20.

0090

010.

0091

110.

0096

980.

0095

0.01

0031

0.01

0113

Cr C

DL99

0.04

0065

0.03

9561

0.03

6802

0.03

7541

0.03

6799

0.03

9222

0.03

6415

0.03

9292

0.04

5506

0.04

1712

0.03

7925

0.03

9202

0.03

6547

0.03

3795

0.03

742

0.03

6943

0.03

5881

0.03

7845

0.04

216

0.03

5779

0.03

7689

0.03

888

0.03

792

0.04

0137

0.03

9691

Fe C

DL99

0.01

4257

0.03

7158

0.04

5626

0.01

3632

0.06

1365

0.00

5484

0.02

634

0.04

3607

0.05

6167

0.04

680.

0222

50.

0562

070.

0546

430.

0654

130.

0529

610

00.

0508

770.

0603

10

0.02

0915

0.06

9701

0.05

0177

00.

0675

54

Mn

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90.

0366

220.

0385

740.

0392

210.

0374

20.

0405

620.

0331

690.

0375

150.

0383

420.

0372

820.

0360

690.

0341

860.

0366

50.

0388

180.

0317

790.

0397

820.

0383

090.

0400

030.

0361

80.

0367

850.

0374

550.

0372

780.

0371

480.

0377

750.

0351

930.

0349

59

Mg

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90.

0155

140.

0144

340.

0144

240.

0114

240.

0132

210.

0139

370.

0129

380.

0171

970.

0127

520.

0107

480.

0089

040.

0128

0.01

5586

0.01

3299

0.01

010.

0123

750.

0150

960.

0106

460.

0133

930.

0133

720.

0108

720.

0140

470.

0152

60.

0103

890.

0119

21

Ca C

DL99

0.01

1111

0.01

3118

0.00

906

0.01

1751

0.00

3956

0.00

5281

00

0.01

0362

0.00

5667

00.

0053

420.

0109

330.

0101

090.

0117

570.

0087

760

0.00

4998

0.01

5576

0.01

362

0.00

4676

0.00

7723

0.01

6892

0.01

0606

0.00

4571

Na C

DL99

0.01

3425

0.01

3843

0.01

3746

0.01

3586

0.01

4017

0.01

2572

0.01

3887

0.01

3704

0.01

3909

0.01

3381

0.01

2919

0.01

3251

0.01

3762

0.01

4341

0.01

3153

0.01

3567

0.01

4715

0.01

4727

0.01

2599

0.01

4045

0.01

481

0.01

4143

0.01

3661

0.01

3592

0.01

4389

K C

DL99

0.00

8386

0.00

8305

0.00

8027

0.00

792

0.00

7591

0.00

8058

0.00

8069

0.00

7935

0.00

8067

0.00

7903

0.00

7831

0.00

818

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7998

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8117

0.00

7826

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7698

0.00

8158

0.00

8291

0.00

8019

0.00

7822

0.00

8148

0.00

8069

0.00

8362

0.00

7916

0.00

769

P C

DL99

0.01

1866

0.01

3124

0.01

1489

0.01

1691

0.01

1901

0.01

2763

0.01

2101

0.01

0774

0.01

0788

0.01

2124

0.01

0338

0.01

1385

0.01

3765

0.01

2009

0.01

2257

0.01

1698

0.01

163

0.01

2765

0.01

2898

0.01

2125

0.01

1701

0.01

1651

0.01

1536

0.01

0357

0.01

1682

S C

DL99

0.00

814

0.00

7559

0.00

7874

0.00

796

0.00

7761

0.00

7554

0.00

8037

0.00

7937

0.00

7456

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7694

0.00

8202

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8289

0.00

8453

0.00

7889

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7976

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7994

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7857

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8125

0.00

8143

0.00

775

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7672

0.00

8056

0.00

7771

0.00

7019

0.00

7791

Cl C

DL99

0.01

121

0.00

9926

0.01

1053

0.00

967

0.01

0388

0.01

0856

0.01

0957

0.01

0373

0.01

0211

0.00

980.

0100

290.

0107

850.

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030.

0104

460.

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720.

0089

870.

0105

650.

0105

120.

0102

290.

0110

750.

0112

830.

0111

510.

0112

40.

0099

570.

0094

27

Page 87: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

81

SAM

PLE

MV

P9

9-2

-22

SPO

T N

°1

23

45

67

89

10

11

12

13

14

15

16

17

18

19

MIN

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AL

Grt

Grt

Grt

Grt

(Rim

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im)

Cp

xC

px

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Pl

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Grt

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11

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39

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35

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50

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07

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52

2.9

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92

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13

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21

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27

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15

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10

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1.3

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99

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10

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00

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21

0.5

21

2.5

38

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10

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10

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10

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10

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10

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10

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Ca

O

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86

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01

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13

90

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17

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11

87

30

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06

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19

85

10

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95

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0.0

19

00

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62

60

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34

50

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94

90

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11

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10

51

10

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09

93

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50

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41

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0.0

10

01

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35

60

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55

3

Cr

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66

20

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44

40

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06

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54

80

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56

51

0.0

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57

40

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0.0

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72

40

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04

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68

30

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60

60

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61

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40

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43

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65

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17

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26

9

Fe C

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81

60

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70

08

0.0

52

60

90

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54

30

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67

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13

91

80

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39

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58

35

50

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74

50

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33

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25

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45

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16

30

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10

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70

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20

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40

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70

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08

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59

09

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12

10

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99

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80

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60

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54

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59

50

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44

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1

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84

99

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45

60

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22

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30

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67

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90

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15

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08

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12

06

50

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49

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40

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20

60

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30

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90

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10

01

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93

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85

90

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10

94

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82

3

S C

DL9

90

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79

80

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80

75

0.0

08

15

60

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81

12

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17

60

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Cl C

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05

69

0.0

10

04

40

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10

99

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10

98

50

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11

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0.0

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45

10

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02

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70

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0.0

10

14

8

Page 88: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

82

SAM

PLE

MVP

1043

5

SPO

T N

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23

45

67

89

1011

1213

1415

1617

1819

2021

2223

2425

MIN

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Cpx

Cpx

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Grt

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TiO

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300.

31b.

d.0.

06b.

d.b.

d.0.

400.

04b.

d.0.

08b.

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d.0.

290.

33b.

d.b.

d.0.

05b.

d.0.

080.

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d.33

.75

0.03

b.d.

Al2O

3 4.

174.

2421

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21.4

221

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20.5

617

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10.8

233

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32.6

11.

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d.b.

d.b.

d.b.

d.b.

d.0.

110.

06b.

d.b.

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d.b.

d.b.

d.b.

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d.0.

11b.

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d.

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221

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01.

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425

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34.8

37.

550.

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MnO

b.

d.0.

060.

510.

530.

500.

500.

290.

62b.

d.b.

d.0.

180.

160.

090.

070.

560.

460.

510.

560.

540.

580.

17b.

d.0.

140.

570.

59

MgO

12

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12.4

18.

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758.

358.

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0.28

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11.8

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8.62

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93.

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149.

509.

56

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21

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57.

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524.

592.

2816

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13.9

10.

390.

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O

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0.28

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0.12

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0.97

2.08

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d.b.

d.b.

d.b.

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090.

150.

010.

090.

15b.

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d.b.

d.b.

d.b.

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030.

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P2O

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d.b.

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SO

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d.b.

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19b.

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d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

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d.

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b.d.

b.d.

b.d.

b.d.

b.d.

0.13

b.d.

b.d.

0.01

b.d.

b.d.

b.d.

b.d.

b.d.

0.01

b.d.

b.d.

0.01

b.d.

b.d.

b.d.

0.01

b.d.

b.d.

TOTA

L97

.81

98.5

698

.87

100.

1898

.92

95.4

567

.30

98.3

910

1.21

100.

2390

.16

91.0

190

.86

100.

1499

.44

98.7

475

.35

98.0

710

0.20

98.8

896

.89

99.8

193

.63

99.1

999

.13

Si

1.90

91.

907

6.04

56.

002

6.07

16.

050

4.23

27.

035

2.16

82.

226

1.88

21.

877

1.84

81.

913

6.01

36.

005

7.78

56.

055

5.94

74.

784

6.45

22.

177

0.00

46.

014

6.02

2

Ti

0.00

90.

009

0.00

20.

007

0.00

30.

000

0.07

30.

004

0.00

00.

003

0.00

00.

001

0.00

90.

009

0.00

00.

002

0.00

70.

003

0.00

90.

010

0.00

00.

000

0.73

40.

004

0.00

1

Al

0.18

70.

189

3.87

53.

857

3.93

53.

872

4.97

81.

951

1.79

91.

758

0.08

60.

088

0.17

30.

191

3.86

13.

836

0.00

03.

914

3.52

54.

205

4.71

41.

796

0.04

43.

863

3.82

6

Cr

0.00

00.

001

0.00

00.

000

0.00

00.

003

0.00

00.

000

0.00

10.

004

0.00

20.

000

0.00

00.

000

0.00

10.

004

0.00

30.

000

0.00

20.

001

0.00

50.

001

0.00

20.

004

0.00

0

Fe

0.27

50.

278

2.72

02.

838

2.70

42.

831

4.40

22.

891

0.06

40.

099

0.71

70.

740

0.32

20.

290

2.89

72.

926

3.93

02.

795

3.36

54.

841

0.92

70.

016

1.35

72.

794

2.81

2

Mn

0.00

10.

002

0.06

60.

069

0.06

50.

067

0.06

00.

080

0.00

00.

001

0.00

60.

006

0.00

30.

002

0.07

20.

061

0.09

20.

073

0.07

10.

081

0.02

10.

000

0.00

30.

075

0.07

6

Mg

0.69

50.

700

2.01

91.

992

1.91

02.

028

1.45

03.

634

0.00

40.

019

1.36

21.

341

0.74

00.

685

1.97

82.

008

2.89

91.

961

2.25

62.

970

0.83

40.

000

0.09

22.

173

2.19

1

Ca

0.86

10.

854

1.28

11.

293

1.25

81.

116

1.20

10.

374

0.81

90.

682

0.01

70.

024

0.90

70.

840

1.22

01.

213

1.41

91.

163

1.08

50.

208

2.08

00.

835

0.00

01.

113

1.13

0

Na

0.09

80.

099

0.00

00.

000

0.01

10.

057

0.07

30.

022

0.12

90.

142

0.00

40.

004

0.10

80.

103

0.00

50.

004

0.11

60.

002

0.03

70.

000

0.27

60.

186

0.00

00.

002

0.00

0

K 0.

000

0.00

00.

000

0.00

00.

000

0.01

80.

048

0.00

30.

005

0.00

90.

000

0.00

00.

000

0.00

00.

000

0.00

10.

000

0.00

20.

002

0.00

00.

006

0.00

40.

000

0.00

00.

000

P 0.

001

0.00

00.

004

0.00

00.

003

0.00

00.

040

0.00

10.

002

0.00

10.

000

0.00

10.

000

0.00

00.

003

0.00

50.

002

0.00

60.

000

0.00

10.

004

0.00

20.

000

0.00

30.

003

S 0.

000

0.00

00.

000

0.00

10.

000

0.00

30.

217

0.00

00.

002

0.00

70.

000

0.00

00.

000

0.00

00.

001

0.00

10.

002

0.00

20.

000

0.00

00.

001

0.00

00.

000

0.00

00.

000

Cl

0.00

00.

000

0.00

00.

001

0.00

00.

000

0.05

50.

002

0.00

00.

001

0.00

00.

000

0.00

00.

000

0.00

00.

003

0.00

20.

000

0.00

30.

000

0.00

10.

000

0.00

10.

000

0.00

2

TOTA

L4.

036

4.03

816

.011

16.0

6015

.960

16.0

4516

.828

15.9

984.

993

4.95

24.

076

4.08

04.

110

4.03

316

.052

16.0

6916

.258

15.9

7516

.303

17.1

0115

.322

5.01

72.

238

16.0

4516

.063

NO

X6

624

2424

2424

248

86

66

624

2424

2424

2424

83

2424

Si C

DL9

90.

0087

760.

0117

030.

0123

970.

0088

780.

0141

470.

0085

040.

0076

50.

0098

250.

0108

540.

0123

630.

0127

380.

0099

270.

0117

460.

0124

70.

0115

940.

0107

290.

0092

360.

0115

580.

0131

190.

0092

360.

0108

330.

0081

640.

0087

410.

0112

410.

0127

04

Ti C

DL9

90.

0202

320.

0200

720.

0200

770.

0195

450.

0201

140.

0218

350.

0203

110.

0203

350.

0201

460.

0200

810.

0200

850.

0196

610.

0198

380.

0203

30.

0202

20.

0200

880.

0188

480.

0196

430.

0195

530.

0200

890.

0198

840.

0193

950.

0226

740.

0198

490.

0204

26

Al C

DL9

90.

0093

380.

0091

110.

0103

690.

0107

540.

0105

230.

0102

710.

0093

730.

0099

90.

0103

040.

0107

550.

0096

690.

0093

670.

0089

30.

0092

830.

0102

390.

0105

840.

0107

150.

0106

480.

0109

460.

0109

020.

0099

790.

0103

010.

0111

150.

0107

510.

0101

52

Cr C

DL9

90.

0418

820.

0383

330.

0423

0.04

0942

0.03

8752

0.03

4953

0.03

6746

0.03

8467

0.03

6694

0.03

8274

0.03

4357

0.03

8687

0.03

8287

0.04

3364

0.03

7716

0.03

3673

0.03

6109

0.04

2416

0.03

4712

0.03

8976

0.03

3453

0.03

5778

0.04

468

0.03

4282

0.03

8407

Fe C

DL9

90.

0524

070

0.08

1635

00.

0118

370.

0451

230.

0371

420.

0598

660

0.02

4564

0.07

3183

0.03

1582

0.04

6578

0.03

0012

0.05

0255

0.03

1244

00.

0911

270

0.06

0215

0.04

6205

00.

0678

340.

0350

640.

0472

8

Mn

CDL9

90.

0397

60.

0369

380.

0404

090.

0399

560.

0377

640.

0389

220.

0389

840.

0377

040.

0401

760.

0369

460.

0404

280.

0379

780.

0396

650.

0376

110.

0382

960.

0443

30.

0366

320.

0397

480.

0413

080.

0409

340.

0410

630.

0381

070.

0447

440.

0373

120.

0385

26

Mg

CDL9

90.

0140

160.

0135

990.

0120

260.

0092

720.

0114

20.

0125

220.

0105

330.

0132

540.

0145

760.

0098

630.

0122

470.

0164

390.

0107

920.

0153

080.

0102

520.

0117

080.

0135

20.

0134

850.

0133

840.

0104

450.

0102

090.

0097

970.

0145

690.

0083

620.

0114

12

Ca C

DL9

90.

0118

070.

0125

70.

0056

20.

0084

640.

0160

410.

0027

010

0.01

507

0.01

5741

0.01

5766

0.01

3317

0.00

9437

0.01

0252

00.

0101

570.

0032

220.

0112

960.

0144

080.

0066

140.

0134

10.

0125

280

0.01

1997

0.00

5992

0

Na

CDL9

90.

0153

230.

0152

460.

0153

860.

0158

380.

0154

30.

0147

540.

0159

280.

0157

180.

0151

210.

0147

170.

0146

80.

0157

090.

0153

380.

0146

860.

0152

670.

0151

360.

0167

730.

0142

610.

0150

780.

0171

970.

0142

930.

0144

460.

0236

790.

0149

490.

0146

56

K C

DL9

90.

0080

920.

0078

630.

0087

590.

0084

940.

0083

610.

0083

480.

0081

040.

0084

430.

0079

420.

0081

490.

0084

810.

0083

460.

008

0.00

8168

0.00

8596

0.00

8251

0.00

8468

0.00

8253

0.00

8518

0.00

8945

0.00

8027

0.00

7818

0.00

9237

0.00

8438

0.00

8356

P C

DL9

90.

0101

910.

0117

170.

0105

730.

0130

270.

0123

10.

0118

710.

0109

030.

0115

520.

0108

890.

0108

220.

0134

080.

0113

820.

0114

50.

0134

840.

0112

760.

0119

580.

0119

880.

0104

430.

0125

90.

0122

250.

0113

540.

0107

670.

0125

10.

0123

220.

0118

72

S C

DL9

90.

0077

330.

0080

590.

0085

130.

0077

710.

0080

160.

0079

30.

0069

240.

0085

790.

0077

120.

0082

670.

0085

040.

0082

140.

0079

470.

0081

130.

0083

170.

0075

330.

0083

80.

0078

840.

0082

840.

0085

540.

0075

180.

0072

480.

0085

590.

0082

630.

0085

66

Cl C

DL9

90.

0098

220.

0104

250.

0110

420.

0100

840.

0105

750.

0107

40.

0106

910.

0103

60.

0102

020.

0098

280.

0108

630.

0113

880.

0104

790.

0112

210.

0110

550.

0103

40.

0105

310.

0108

290.

0104

10.

0119

410.

0104

810.

0102

940.

0113

30.

0108

750.

0100

03

Page 89: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

83

SA

MP

LE M

VP

10

43

8

SP

OT

12

34

56

78

91

01

11

21

31

4

MIN

ER

AL

Scp

Scp

Scp

Scp

(Rim

)S

cp(R

im)

Op

xP

lP

lP

lP

lO

px

Op

xO

px

Op

x

SiO

2

42

.61

42

.40

50

.34

51

.30

58

.50

50

.65

45

.22

45

.87

45

.14

45

.49

50

.21

50

.54

49

.72

50

.43

TiO

2

b.d

.b

.d.

b.d

.b

.d.

b.d

.0

.10

b.d

.b

.d.

b.d

.b

.d.

0.0

6b

.d.

0.2

00

.05

Al2

O3

2

6.4

82

7.4

72

8.4

72

8.7

71

8.9

34

.29

33

.47

33

.40

33

.43

33

.73

4.2

34

.26

4.2

24

.16

Cr2

O3

b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.

Fe

O

0.4

90

.45

0.2

10

.24

0.6

51

9.6

80

.55

0.1

8b

.d.

0.3

71

9.3

52

0.7

11

9.2

61

9.9

1

Mn

O

b.d

.0

.07

b.d

.b

.d.

b.d

.0

.51

b.d

.b

.d.

b.d

.0

.08

0.4

20

.45

0.4

40

.43

Mg

O

0.1

20

.10

0.0

70

.04

0.1

92

2.6

7b

.d.

b.d

.b

.d.

b.d

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2.6

12

2.8

72

2.3

22

2.6

4

Ca

O

19

.32

19

.13

13

.20

12

.67

8.3

1b

.d.

17

.93

17

.76

17

.91

18

.07

0.5

70

.71

1.0

90

.85

Na

2O

2

.54

2.4

63

.36

2.6

13

.28

0.0

31

.58

1.6

81

.59

1.5

1b

.d.

b.d

.0

.06

0.0

2

K2

O

0.0

70

.07

0.4

90

.42

0.2

3b

.d.

0.0

40

.05

0.0

40

.05

b.d

.b

.d.

b.d

.b

.d.

P2

O5

0

.10

0.1

80

.04

0.0

40

.47

b.d

.b

.d.

0.0

4b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.

SO

3

5.3

55

.45

0.1

00

.08

0.3

6b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

C

l b

.d.

b.d

.0

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0.1

00

.08

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.

TO

TA

L9

7.0

79

7.7

89

6.3

79

6.2

89

1.0

09

7.9

29

8.8

09

8.9

89

8.1

19

9.3

19

7.4

59

9.5

39

7.3

09

8.5

0

Si

6.9

26

6.8

03

7.1

99

7.2

24

8.6

86

1.9

02

2.1

17

2.1

37

2.1

21

2.1

17

1.8

96

1.8

79

1.8

85

1.8

91

Ti

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

03

0.0

00

0.0

00

0.0

00

0.0

00

0.0

02

0.0

01

0.0

06

0.0

01

Al

5.0

74

5.1

97

4.8

01

4.7

76

3.3

14

0.1

90

1.8

46

1.8

34

1.8

51

1.8

50

0.1

88

0.1

87

0.1

89

0.1

84

Cr

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

02

0.0

00

0.0

02

0.0

01

0.0

01

0.0

01

Fe

0

.06

60

.06

10

.02

50

.02

90

.08

10

.61

80

.02

20

.00

70

.00

00

.01

40

.61

10

.64

40

.61

00

.62

4

Mn

0

.00

00

.00

70

.00

00

.00

00

.00

00

.01

60

.00

00

.00

00

.00

00

.00

30

.01

30

.01

40

.01

40

.01

4

Mg

0

.02

80

.02

30

.01

40

.00

90

.04

11

.26

90

.00

00

.00

00

.00

00

.00

01

.27

31

.26

81

.26

11

.26

5

Ca

3

.36

43

.29

02

.02

31

.91

31

.32

30

.00

00

.90

00

.88

70

.90

10

.90

10

.02

30

.02

80

.04

40

.03

4

Na

0

.80

10

.76

60

.93

10

.71

10

.94

30

.00

20

.14

30

.15

20

.14

50

.13

70

.00

10

.00

00

.00

40

.00

2

K

0.0

15

0.0

15

0.0

90

0.0

76

0.0

43

0.0

00

0.0

02

0.0

03

0.0

03

0.0

03

0.0

00

0.0

00

0.0

01

0.0

00

P

0.0

14

0.0

24

0.0

05

0.0

05

0.0

59

0.0

00

0.0

01

0.0

01

0.0

01

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

S

0.6

52

0.6

56

0.0

11

0.0

08

0.0

40

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

01

0.0

01

0.0

00

Cl

0.0

00

0.0

00

0.0

23

0.0

24

0.0

20

0.0

03

0.0

03

0.0

02

0.0

03

0.0

03

0.0

03

0.0

03

0.0

03

0.0

03

TO

TA

L1

6.9

41

16

.84

31

5.1

21

04

14

.77

51

4.5

50

4.0

04

5.0

34

5.0

23

5.0

26

5.0

29

4.0

11

4.0

27

4.0

19

4.0

19

NO

X1

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l6

88

88

66

66

Si

CD

L99

0.0

09

67

50

.01

69

73

0.0

18

24

0.0

22

32

10

.00

96

26

0.0

21

53

20

.00

94

85

0.0

16

43

0.0

05

74

20

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98

39

0.0

14

15

10

.01

87

34

0.0

19

83

50

.01

89

94

Ti

CD

L99

0.0

26

26

80

.02

77

10

.02

71

84

0.0

29

85

80

.02

86

0.0

28

22

90

.02

67

33

0.0

27

79

80

.02

62

71

0.0

28

13

40

.02

80

15

0.0

27

68

70

.02

81

08

0.0

28

34

1

Al

CD

L99

0.0

14

52

30

.01

43

79

0.0

14

13

80

.01

49

44

0.0

14

63

10

.01

41

30

.01

44

22

0.0

13

60

30

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38

96

0.0

14

93

70

.01

50

02

0.0

15

09

50

.01

53

43

0.0

13

78

6

Cr

CD

L99

0.0

61

66

90

.04

68

45

0.0

59

18

10

.05

38

20

.06

11

41

0.0

53

79

10

.05

96

11

0.0

52

64

10

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68

29

0.0

59

56

80

.06

11

73

0.0

44

20

90

.04

96

11

0.0

53

76

2

Fe

CD

L99

0.0

86

80

90

00

00

.08

81

11

0.0

85

30

90

.04

59

76

0.1

03

10

90

0.0

52

42

0.0

75

12

90

0.1

00

85

1

Mn

CD

L99

0.0

53

38

90

.05

20

82

0.0

52

71

70

.05

75

71

0.0

44

63

40

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28

03

0.0

44

63

50

.04

82

36

0.0

52

24

30

.05

92

78

0.0

55

25

20

.05

92

86

0.0

43

11

30

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10

35

Mg

CD

L99

0.0

13

37

10

.01

39

39

0.0

10

33

0.0

12

99

30

.01

35

65

0.0

15

89

30

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60

74

0.0

11

75

0.0

18

07

10

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18

94

0.0

17

58

40

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49

28

0.0

20

13

10

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40

02

Ca

CD

L99

0.0

18

69

70

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02

45

00

00

0.0

22

60

50

0.0

53

22

30

00

00

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01

63

Na

CD

L99

0.0

09

31

70

.01

48

66

0.0

14

94

20

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38

91

0.0

14

0.0

13

68

90

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40

53

0.0

13

58

40

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48

92

0.0

13

84

0.0

14

06

70

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35

93

0.0

13

36

50

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46

94

K C

DL9

90

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10

44

0.0

11

34

20

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15

35

0.0

11

16

30

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14

16

0.0

11

17

60

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10

56

0.0

10

91

80

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22

0.0

11

19

0.0

10

77

30

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13

74

0.0

10

80

50

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8

P C

DL9

90

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64

48

0.0

16

41

90

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61

38

0.0

16

74

60

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26

75

0.0

14

60

10

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56

93

0.0

20

39

50

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94

95

0.0

16

47

30

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48

21

0.0

13

70

50

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85

68

0.0

18

62

4

S C

DL9

90

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06

02

0.0

10

29

30

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17

42

0.0

10

85

60

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18

93

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06

40

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07

73

0.0

10

50

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12

17

0.0

10

06

50

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09

69

0.0

10

11

0.0

11

84

50

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16

83

Cl

CD

L99

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

0.0

55

Page 90: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

84

SAM

PLE

MV

P1

04

38

SPO

T N

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51

61

71

81

92

02

12

22

32

42

52

62

72

82

93

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1

MIN

ER

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Cp

xC

px

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Pl

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48

.72

49

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48

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48

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63

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20

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Mn

O

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60

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30

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1

2.4

71

2.4

01

2.7

36

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5.2

10

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0.0

90

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b.d

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12

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O

22

.52

21

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21

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2.0

20

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18

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18

.88

19

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18

.59

18

.40

17

.70

17

.82

22

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17

.44

17

.59

17

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17

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Na

2O

0

.57

0.5

40

.61

0.0

50

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2.4

42

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2.6

12

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2.5

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90

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1.6

91

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81

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b.d

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0.0

80

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SO

3

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b.d

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b.d

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75

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54

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TO

TA

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8.8

89

8.5

69

8.5

31

01

.17

98

.89

96

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96

.95

97

.18

96

.68

96

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98

.79

99

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97

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98

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98

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98

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98

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Si

1.8

39

1.8

56

1.8

49

0.5

21

0.4

84

6.7

67

6.7

98

6.7

89

6.7

91

6.8

14

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93

1.5

64

1.8

51

2.0

82

2.1

22

2.1

32

2.1

26

Ti

0.0

19

0.0

20

0.0

17

2.1

41

2.2

31

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

18

0.0

00

0.0

00

0.0

00

0.0

00

Al

0.2

59

0.2

66

0.2

51

0.0

51

0.0

43

5.2

33

5.2

02

5.2

11

5.2

09

5.1

86

1.8

88

1.4

18

0.2

67

1.9

13

1.8

63

1.8

57

1.8

54

Cr

0.0

02

0.0

02

0.0

03

0.0

05

0.0

01

0.0

00

0.0

00

0.0

00

0.0

00

0.0

12

0.0

00

0.0

00

0.0

01

0.0

00

0.0

02

0.0

00

0.0

00

Fe

0.2

51

0.2

53

0.2

66

0.1

54

0.1

49

0.0

00

0.0

00

0.0

22

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0.0

53

0.0

20

0.0

22

0.2

25

0.0

00

0.0

00

0.0

04

0.0

06

Mn

0

.00

50

.00

60

.00

40

.00

40

.00

30

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00

.00

00

.00

00

.00

00

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00

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20

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00

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50

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30

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00

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Mg

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01

0.6

98

0.7

19

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48

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0.0

21

0.0

09

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00

0.0

00

0.0

00

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04

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98

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Ca

0

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60

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83

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70

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0

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50

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0.0

00

0.0

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18

0.0

16

0.0

15

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14

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TO

TA

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24

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14

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23

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43

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61

6.7

13

16

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51

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95

5.0

31

3.7

79

4.0

17

5.0

42

5.0

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5.0

25

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27

NO

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66

66

12

Si+

Al

12

Si+

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12

Si+

Al

12

Si+

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12

Si+

Al

88

68

88

8

Si C

DL9

90

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19

05

0.0

20

32

30

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72

85

0.0

16

15

10

0.0

25

45

20

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60

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18

35

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91

90

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61

14

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69

40

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30

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79

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80

80

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18

Ti C

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82

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26

10

20

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87

23

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28

81

20

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92

73

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50

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60

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67

27

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28

21

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69

21

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27

08

80

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82

96

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04

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28

04

1

Al C

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90

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51

32

0.0

14

16

30

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41

56

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13

50

70

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28

42

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56

30

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69

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80

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72

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50

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14

40

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49

99

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15

49

20

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48

32

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56

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Cr

CD

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44

50

10

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92

98

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50

64

40

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14

63

0.0

50

22

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54

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86

60

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72

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35

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26

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16

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3

Fe C

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0.1

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83

10

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02

32

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55

37

60

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42

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31

97

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82

18

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72

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92

19

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57

20

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39

26

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92

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22

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73

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80

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50

53

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10

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49

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51

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66

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54

60

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55

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40

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69

84

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25

79

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81

15

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99

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63

60

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65

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92

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53

71

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30

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51

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91

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39

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29

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72

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P C

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07

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50

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50

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50

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50

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50

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50

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50

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50

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50

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50

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50

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5

Page 91: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

85

SAM

PLE

DEL

2-10

434

SPO

T N

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23

45

67

89

1011

1213

1415

1617

1819

2021

2223

2425

MIN

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Grt

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SiO

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38.4

538

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42.9

342

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37.6

339

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39.2

447

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139

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539

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420.

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420.

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941.

990.

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440.

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360.

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362.

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111

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119

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111

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120.

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100.

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160.

11b.

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3617

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0.12

0.13

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0.08

0.09

0.07

1.72

2.82

2.83

2.86

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d.b.

d.b.

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16b.

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d.

P2O

5 b.

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05b.

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080.

04b.

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110.

120.

09b.

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SO

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d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

d.b.

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03b.

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d.

Cl

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b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

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b.d.

b.d.

b.d.

b.d.

b.d.

b.d.

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b.d.

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0.09

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TOTA

L98

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98.2

498

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99.1

398

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94.2

393

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397

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101.

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Si

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840

5.88

75.

867

5.89

11.

704

1.71

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777

6.09

25.

961

1.77

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783

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941

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845

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1.78

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Ti

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60.

058

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016

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6

Al

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524

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23.

846

3.78

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904

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50.

488

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936

3.92

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942

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73.

976

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493

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10.

487

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002

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001

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279

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600

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466

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508

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287

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557

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62.

366

2.51

52.

371

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52.

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351

2.38

42.

362

2.37

72.

362

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532

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50.

527

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2

Ca

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289

1.09

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11.

479

0.91

31.

152

0.71

70.

717

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71.

190

1.19

71.

293

1.17

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286

1.25

71.

177

1.10

20.

708

0.70

80.

715

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3

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188

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027

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20.

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002

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30.

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002

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3

TOTA

L16

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16.1

0716

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16.3

6816

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4.08

44.

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6216

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664.

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4616

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NO

X24

2424

2424

66

2424

246

66

2424

2424

2424

2424

66

66

Si C

DL9

90.

0187

340.

0216

40.

0155

810.

0141

730.

0152

830.

0165

640.

0206

120.

0212

050.

0090

540.

0203

580.

0205

120.

0142

760.

0171

970.

0165

930.

0103

620.

0073

130.

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110.

0168

430.

0197

240.

0172

20.

0191

770.

0165

410.

0214

660.

0129

620.

0204

33

Ti C

DL9

90.

0274

680.

0275

180.

0287

790.

0273

760.

0279

920.

0272

150.

0283

10.

0279

0.02

9657

0.02

8204

0.02

8215

0.02

8457

0.02

7012

0.02

7229

0.02

869

0.02

803

0.02

7933

0.02

8551

0.02

9177

0.02

8846

0.02

925

0.02

7989

0.02

7465

0.02

8929

0.02

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Al C

DL9

90.

0153

950.

0155

760.

0147

960.

0155

620.

0147

140.

0138

890.

0143

680.

0153

360.

0144

470.

0147

380.

0142

650.

0137

90.

0143

880.

0150

430.

0157

70.

0151

830.

0159

430.

0155

720.

0150

930.

0149

70.

0145

40.

0136

370.

0138

890.

0136

070.

0135

49

Cr C

DL9

90.

0572

280.

0581

540.

0505

230.

0469

630.

0547

430.

0526

610.

0549

610.

0518

450.

0477

310.

0474

630.

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210.

0552

530.

0584

010.

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920.

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220.

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180.

0629

540.

0570

240.

0515

270.

0546

340.

0551

570.

0583

460.

0529

990.

0574

580.

0586

24

Fe C

DL9

90.

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220

00.

0697

870

00.

0420

610.

0783

260

00

0.07

9788

00.

0645

50

0.13

5943

00

00.

1187

270.

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0212

40.

0656

240.

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430.

0204

79

Mn

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420.

0573

040.

0476

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40.

0534

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0497

120.

0547

80.

0502

510.

0573

70.

0550

650.

0565

480.

0542

170.

0535

480.

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210.

0521

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70.

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0503

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0527

910.

0594

340.

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850.

0554

0.04

2714

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880.

0161

060.

0198

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260.

0156

370.

0186

310.

0200

360.

0124

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0147

760.

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330.

0167

780.

0198

390.

0165

180.

0180

290.

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040.

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50.

0152

390.

0131

340.

0144

390.

0186

730.

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0156

570.

0213

840.

0108

740.

0238

31

Ca C

DL9

90.

0215

860

0.02

2695

0.00

208

0.01

5531

0.01

596

0.01

3929

0.00

3991

00

0.00

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0.01

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00.

0161

240.

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530

0.01

9985

00

0.01

9652

00.

0136

270.

0200

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6458

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030.

0144

780.

0147

630.

0158

270.

0150

90.

0152

370.

0153

310.

0161

170.

0144

680.

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150.

0151

0.01

4355

0.01

6726

0.01

4629

0.01

469

0.01

5196

0.01

5128

0.01

4648

0.01

4271

0.01

5301

0.01

492

0.01

4767

0.01

4384

0.01

4474

0.01

4634

K C

DL9

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0117

80.

0118

580.

0115

340.

0115

980.

0115

940.

0111

390.

0110

630.

0121

560.

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620.

0116

390.

0116

970.

0115

750.

0110

990.

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640.

0117

340.

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570.

0119

50.

0119

360.

0118

730.

0114

450.

0116

880.

0114

950.

0115

840.

0111

960.

0114

39

P C

DL9

90.

0188

0.02

0086

0.01

9078

0.01

6115

0.01

646

0.02

0088

0.01

7697

0.01

5043

0.01

4475

0.01

6437

0.01

6254

0.01

8597

0.01

4597

0.01

3676

0.01

6753

0.01

5811

0.01

7974

0.01

7046

0.01

6752

0.01

740.

0173

730.

0135

420.

0159

710.

0152

940.

0162

34

S C

DL9

90.

0106

370.

0117

930.

0114

560.

0120

110.

0116

620.

0112

250.

0103

740.

0110

260.

0113

440.

0108

480.

0118

670.

0110

110.

0111

190.

0115

860.

0124

980.

0102

760.

0113

420.

0109

820.

0110

210.

0103

580.

0092

460.

0107

340.

0114

990.

0107

650.

0113

12

Cl C

DL9

90.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

0.05

50.

055

Page 92: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

86

SAM

PLE

MV

P9

9-2

-22

SPO

T N

°1

23

45

67

89

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

MIN

ERA

LC

px

Cp

xC

px

Cp

xC

px

Cp

xG

rtG

rtG

rtSc

pSc

pSc

pSc

pSc

pSc

pSc

pG

rtG

rtG

rtC

px

Cp

xC

px

Cp

xSc

p

SiO

2

48

.86

49

.02

49

.19

49

.42

48

.89

b.d

.3

8.6

83

8.8

03

9.0

74

5.9

44

5.9

24

5.9

34

5.7

94

6.5

64

6.9

54

6.6

73

8.8

23

8.1

23

7.9

34

4.3

74

4.2

84

8.3

34

8.2

24

2.3

5

TiO

2

1.1

11

.10

1.0

71

.11

1.0

21

.01

0.1

80

.25

0.2

3b

.d.

0.0

60

.07

b.d

.0

.05

0.0

6b

.d.

0.2

40

.21

0.2

31

.14

1.0

91

.10

1.1

0b

.d.

Al2

O3

9

.59

9.5

29

.53

9.4

29

.50

10

.57

22

.98

22

.81

23

.15

25

.48

25

.39

25

.22

25

.25

24

.91

24

.81

24

.63

22

.96

22

.93

23

.14

9.7

09

.81

9.6

89

.58

26

.36

Cr2

O3

0

.09

b.d

.0

.08

b.d

.b

.d.

0.0

9b

.d.

0.1

1b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.0

.10

b.d

.b

.d.

b.d

.b

.d.

b.d

.

Fe

O

7.0

46

.53

7.1

26

.95

7.2

37

.10

17

.78

16

.81

17

.01

0.3

3b

.d.

0.2

70

.57

0.2

40

.15

0.4

81

7.1

61

6.9

31

6.7

77

.15

7.0

37

.51

6.4

70

.71

Mn

O

0.0

9b

.d.

b.d

.0

.12

0.1

1b

.d.

0.3

00

.39

0.2

8b

.d.

b.d

.b

.d.

b.d

.b

.d.

0.0

8b

.d.

0.3

20

.35

0.3

40

.13

0.0

70

.07

b.d

.b

.d.

MgO

1

0.9

61

0.9

21

1.0

11

1.0

21

1.2

11

1.7

01

1.3

21

1.2

71

1.1

80

.21

0.1

90

.29

0.2

60

.14

0.2

00

.20

11

.44

11

.14

11

.26

10

.66

10

.51

11

.03

11

.14

0.3

1

CaO

1

9.7

61

9.4

92

0.0

12

0.0

31

9.0

11

9.2

48

.29

7.9

18

.20

16

.43

16

.66

16

.48

15

.95

16

.39

16

.08

16

.18

8.1

37

.98

8.1

81

9.4

81

9.1

11

9.3

81

9.5

41

5.7

6

Na2

O

1.6

11

.72

1.6

31

.63

1.6

71

.79

b.d

.0

.04

0.0

43

.60

3.6

63

.59

3.7

03

.60

3.6

83

.64

0.0

30

.05

0.0

51

.67

1.6

91

.72

1.6

43

.55

K2

O

b.d

.0

.01

b.d

.0

.02

b.d

.b

.d.

b.d

.b

.d.

b.d

.0

.20

0.2

20

.21

0.2

10

.22

0.2

20

.21

b.d

.b

.d.

b.d

.b

.d.

0.0

2b

.d.

b.d

.0

.22

P2

O5

b

.d.

b.d

.b

.d.

0.0

4b

.d.

b.d

.0

.05

0.0

50

.05

0.1

30

.13

0.1

30

.15

0.1

50

.13

0.1

10

.07

0.0

50

.05

0.0

5b

.d.

b.d

.b

.d.

0.1

5

SO

3

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.4

.51

4.5

34

.35

4.5

24

.53

4.6

34

.53

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.4

.39

Cl

b.d

.0

.06

b.d

.b

.d.

b.d

.b

.d.

b.d

.b

.d.

b.d

.0

.10

0.0

90

.11

0.1

00

.09

0.0

80

.10

b.d

.0

.06

b.d

.b

.d.

b.d

.b

.d.

b.d

.0

.12

TOTA

L9

9.1

09

8.3

69

9.6

59

9.7

69

8.6

35

1.5

19

9.5

79

8.4

59

9.1

99

6.9

49

6.8

69

6.6

59

6.4

99

6.8

79

7.0

89

6.7

59

9.1

69

7.8

19

8.0

39

4.3

69

3.6

19

8.8

29

7.6

89

3.9

4

Si

1.8

16

1.8

27

1.8

18

1.8

22

1.8

21

0.0

00

5.8

26

5.8

84

5.8

78

7.2

55

7.2

64

7.2

84

7.2

72

7.3

59

7.3

94

7.3

98

5.8

54

5.8

30

5.7

89

1.7

48

1.7

56

1.8

04

1.8

12

6.9

21

Ti

0.0

31

0.0

31

0.0

30

0.0

31

0.0

29

0.0

69

0.0

20

0.0

29

0.0

25

0.0

00

0.0

07

0.0

08

0.0

00

0.0

06

0.0

08

0.0

00

0.0

27

0.0

24

0.0

26

0.0

34

0.0

33

0.0

31

0.0

31

0.0

00

Al

0.4

20

0.4

18

0.4

15

0.4

09

0.4

17

1.1

30

4.0

80

4.0

77

4.1

04

4.7

45

4.7

36

4.7

16

4.7

28

4.6

41

4.6

06

4.6

02

4.0

80

4.1

34

4.1

62

0.4

50

0.4

59

0.4

26

0.4

24

5.0

79

Cr

0.0

03

0.0

02

0.0

02

0.0

02

0.0

01

0.0

07

0.0

06

0.0

13

0.0

05

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

02

0.0

04

0.0

12

0.0

02

0.0

00

0.0

01

0.0

00

0.0

00

Fe

0.2

19

0.2

03

0.2

20

0.2

14

0.2

25

0.5

39

2.2

39

2.1

32

2.1

40

0.0

44

0.0

00

0.0

36

0.0

76

0.0

32

0.0

20

0.0

64

2.1

64

2.1

65

2.1

40

0.2

36

0.2

33

0.2

35

0.2

03

0.0

97

Mn

0

.00

30

.00

20

.00

20

.00

40

.00

40

.00

10

.03

80

.05

00

.03

50

.00

00

.00

00

.00

00

.00

00

.00

00

.00

90

.00

00

.04

00

.04

50

.04

40

.00

40

.00

20

.00

20

.00

10

.00

0

Mg

0.6

07

0.6

07

0.6

06

0.6

06

0.6

23

1.5

83

2.5

42

2.5

48

2.5

09

0.0

49

0.0

46

0.0

68

0.0

61

0.0

32

0.0

47

0.0

46

2.5

71

2.5

39

2.5

62

0.6

26

0.6

21

0.6

14

0.6

24

0.0

76

Ca

0.7

87

0.7

78

0.7

92

0.7

91

0.7

59

1.8

71

1.3

37

1.2

86

1.3

21

2.7

80

2.8

25

2.8

01

2.7

14

2.7

76

2.7

13

2.7

48

1.3

13

1.3

07

1.3

38

0.8

23

0.8

12

0.7

75

0.7

87

2.7

60

Na

0.1

16

0.1

24

0.1

17

0.1

17

0.1

20

0.3

14

0.0

05

0.0

13

0.0

11

1.1

04

1.1

24

1.1

03

1.1

38

1.1

04

1.1

23

1.1

17

0.0

08

0.0

14

0.0

14

0.1

28

0.1

30

0.1

24

0.1

19

1.1

26

K

0.0

00

0.0

01

0.0

00

0.0

01

0.0

00

0.0

00

0.0

00

0.0

00

0.0

01

0.0

40

0.0

45

0.0

43

0.0

43

0.0

44

0.0

43

0.0

43

0.0

00

0.0

00

0.0

01

0.0

00

0.0

01

0.0

00

0.0

00

0.0

46

P

0.0

00

0.0

00

0.0

00

0.0

01

0.0

01

0.0

02

0.0

06

0.0

07

0.0

07

0.0

18

0.0

17

0.0

18

0.0

20

0.0

20

0.0

18

0.0

15

0.0

09

0.0

07

0.0

07

0.0

02

0.0

00

0.0

00

0.0

00

0.0

21

S 0

.00

00

.00

00

.00

00

.00

00

.00

00

.00

00

.00

20

.00

10

.00

10

.53

50

.53

80

.51

80

.53

90

.53

70

.54

70

.53

90

.00

10

.00

10

.00

00

.00

00

.00

00

.00

00

.00

00

.53

8

Cl

0.0

03

0.0

04

0.0

02

0.0

03

0.0

03

0.0

06

0.0

09

0.0

10

0.0

09

0.0

28

0.0

23

0.0

29

0.0

27

0.0

25

0.0

22

0.0

27

0.0

11

0.0

16

0.0

09

0.0

03

0.0

03

0.0

02

0.0

02

0.0

34

TOTA

L4

.00

33

.99

84

.00

44

.00

04

.00

25

.52

31

6.1

10

16

.04

81

6.0

46

16

.59

71

6.6

24

16

.62

41

6.6

18

16

.57

51

6.5

50

16

.60

01

6.0

79

16

.08

71

6.1

04

4.0

56

4.0

50

4.0

16

4.0

05

16

.69

9

NO

X6

66

66

62

42

42

41

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l1

2 S

i+A

l2

42

42

42

46

66

61

2 S

i+A

l

Si C

DL9

90

.01

27

03

0.0

15

90

50

.01

71

86

0.0

08

66

0.0

20

61

20

.01

61

90

.02

07

41

0.0

11

79

70

.01

58

0.0

15

44

70

.01

77

99

0.0

18

99

10

.02

00

26

0.0

15

56

50

0.0

09

67

30

.01

63

66

0.0

20

26

80

.01

73

34

0.0

14

31

90

.01

53

29

0.0

12

78

70

.01

80

08

0

Ti C

DL9

90

.02

79

33

0.0

29

02

0.0

27

03

40

.02

68

07

0.0

28

92

80

.02

89

32

0.0

29

10

90

.02

74

36

0.0

27

70

90

.02

71

13

0.0

27

13

20

.02

69

27

0.0

27

69

10

.02

64

34

0.0

27

29

20

.02

85

41

0.0

27

53

80

.02

78

18

0.0

28

22

30

.02

92

12

0.0

28

33

10

.02

94

36

0.0

28

32

40

.02

86

47

Al C

DL9

90

.01

42

40

.01

39

40

.01

36

28

0.0

13

53

40

.01

43

01

0.0

16

06

90

.01

46

08

0.0

15

59

60

.01

54

88

0.0

14

24

70

.01

48

90

.01

49

78

0.0

14

21

70

.01

43

57

0.0

13

80

10

.01

46

54

0.0

15

14

70

.01

52

81

0.0

14

66

10

.01

41

59

0.0

14

31

30

.01

37

59

0.0

14

30

90

.01

48

67

Cr

CD

L99

0.0

54

08

70

.05

41

27

0.0

47

88

20

.05

58

81

0.0

53

95

0.0

52

40

.04

85

64

0.0

44

34

20

.05

74

80

.05

87

34

0.0

50

10

70

.05

58

37

0.0

56

07

60

.05

19

98

0.0

54

65

50

.04

95

17

0.0

55

52

50

.05

29

82

0.0

45

50

30

.05

39

31

0.0

53

83

40

.05

74

93

0.0

57

84

70

.05

66

24

Fe C

DL9

90

.09

24

59

0.1

12

14

10

.08

67

92

0.0

44

26

20

.06

86

15

0.0

73

34

90

0.0

65

46

20

.05

96

0.0

55

89

30

.10

72

07

0.0

67

55

80

.02

14

17

0.0

69

98

30

.07

31

95

0.0

39

13

0.0

59

61

50

.07

99

70

.07

98

42

0.0

26

87

70

.06

19

03

00

.08

35

70

Mn

CD

L99

0.0

51

18

0.0

55

00

20

.05

72

51

0.0

51

85

20

.05

49

54

0.0

54

19

50

.06

22

60

.04

98

45

0.0

59

20

20

.05

35

02

0.0

50

97

10

.05

99

61

0.0

54

68

80

.05

88

19

0.0

46

85

90

.05

15

98

0.0

57

58

0.0

55

85

90

.05

41

58

0.0

53

06

80

.04

58

37

0.0

49

26

70

.05

61

91

0.0

46

11

2

Mg

CD

L99

0.0

22

55

50

.01

66

75

0.0

18

62

30

.02

24

70

.01

44

06

0.0

14

47

0.0

16

98

10

.01

37

33

0.0

15

80

50

.01

66

21

0.0

16

66

70

.00

86

35

0.0

12

53

80

.02

02

10

.01

80

64

0.0

16

42

10

.01

92

28

0.0

17

57

60

.02

12

30

.02

32

08

0.0

21

75

50

.01

22

14

0.0

15

05

70

.01

37

08

Ca

CD

L99

0.0

11

33

80

.01

25

00

0.0

28

09

40

.00

89

14

00

.01

52

45

0.0

08

98

20

.01

19

01

00

.01

08

60

.02

49

47

0.0

19

75

20

.02

37

85

0.0

17

61

30

.00

43

31

0.0

16

29

10

.00

71

44

00

.02

02

17

0.0

20

56

0.0

18

29

30

.01

36

51

Na

CD

L99

0.0

13

95

20

.01

41

55

0.0

13

82

10

.01

51

21

0.0

14

02

10

.01

52

64

0.0

15

69

80

.01

36

25

0.0

15

44

10

.01

42

24

0.0

15

73

40

.01

40

35

0.0

13

42

20

.01

39

95

0.0

13

27

80

.01

45

95

0.0

15

58

70

.01

42

73

0.0

13

20

60

.01

49

23

0.0

14

74

60

.01

52

51

0.0

14

36

30

.01

43

22

K C

DL9

90

.01

15

95

0.0

11

81

10

.01

12

67

0.0

11

06

40

.01

15

40

.01

08

23

0.0

11

77

30

.01

17

84

0.0

11

92

10

.01

12

16

0.0

10

79

10

.01

09

60

.01

06

55

0.0

11

22

70

.01

10

11

0.0

11

28

60

.01

19

38

0.0

11

62

40

.01

18

27

0.0

11

34

50

.01

12

37

0.0

11

55

70

.01

14

33

0.0

11

13

3

P C

DL9

90

.01

93

83

0.0

18

35

20

.02

09

03

0.0

13

52

40

.01

59

81

0.0

15

10

40

.01

44

26

0.0

15

83

30

.01

40

84

0.0

18

93

80

.01

72

32

0.0

18

11

10

.01

53

53

0.0

14

66

70

.01

63

32

0.0

15

36

20

.01

37

12

0.0

16

78

40

.01

37

06

0.0

15

57

0.0

16

54

90

.01

83

35

0.0

18

06

60

.01

19

61

S C

DL9

90

.01

06

99

0.0

12

16

60

.01

13

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50

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50

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5

Page 93: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

87

SAM

PLE

MV

P99-

2-22

SPO

T N

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2627

2829

3031

3233

3435

3637

3839

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MIN

ERA

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rt(R

im)

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751

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0

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200.

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d.b.

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180.

230.

180.

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O3

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Al C

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055

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50.

055

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50.

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5

Page 94: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

88

APPENDIX 3 – PRESSURE-TEMPERATURE ESTIMATES (From Part 1 – 2013

thesis)

Appendix Figure 5. Calculated temperatures for pressures between 7-22Kb and calculated pressures for

temperatures between 950-1150⁰C using the geothermometer calibrated by Ravna (2000) and the

geobarometer calibrated by Newton and Perkins (1982). Sample MVP99-2-12 in red and MVP99-2-22 in

blue and black lines representing experimental P-T limits for this assemblage from Irving (1974) using

Delegate sample R130.

Appendix Figure 6. Calculated temperatures between pressures of 6-16Kb using the geothermometer

calibrated by Brey and Kohler (1990). Dashed lines show temperature paths for sample MVP10438 (blue)

and DEL99-2-01 (red). Black lines represent experimental P-T limits for this assemblage from Irving

(1974) based on Delegate sample R698.

Page 95: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

89

Appendix Figure 7. Calculated temperatures between pressures of 13-32Kb using the geothermometer

calibrated by Ravna (2000). Calculated temperatures for sample DEL-2-10434 shown in red. Solid black

lines represent experimental P-T limits and dashed lines for changes in the modal abundance of garnet

based on Delegate sample R392.

Page 96: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

90

APPENDIX 4 –WHOLE ROCK GEOCHEMISTRY DATA

Trac

e el

emen

ts Q

-IC

P-M

S an

alys

is (W

SU G

eoA

nal

ytic

al L

ab)

Sam

ple

ID

La p

pm

Ce

pp

mP

r p

pm

Nd

pp

mSm

pp

mE

u p

pm

Gd

pp

mT

b p

pm

Dy

pp

mH

o p

pm

Er

pp

mT

m p

pm

Yb p

pm

Lu p

pm

DE

L99

-2-0

11.

021.

880.

261.

400.

530.

310.

750.

151.

060.

220.

620.

090.

560.

08

DE

L2-1

04

30

5.48

12.3

11.

737.

962.

410.

882.

850.

523.

350.

691.

870.

271.

660.

25

DE

L2-1

04

31

9.19

16.7

92.

209.

512.

340.

972.

420.

392.

450.

511.

360.

191.

160.

18

DE

L2-1

04

34

8.42

20.8

83.

2716

.37

4.94

1.81

5.94

1.05

6.60

1.39

3.67

0.53

3.21

0.49

MV

P1

04

36

13.3

034

.89

5.45

26.5

67.

372.

087.

771.

307.

831.

574.

060.

573.

350.

49

MV

P1

04

37

11.9

330

.92

4.89

23.9

46.

881.

927.

401.

247.

631.

524.

030.

553.

230.

47

MV

P1

04

38

1.64

3.37

0.49

2.41

0.73

0.40

0.81

0.14

0.91

0.19

0.52

0.08

0.47

0.07

MV

P9

9-2

-04

3.59

6.55

0.82

3.48

0.94

0.62

1.12

0.21

1.29

0.27

0.71

0.10

0.64

0.10

MV

P9

9-2

-08

2.35

4.93

0.66

2.82

0.76

0.38

0.78

0.13

0.86

0.18

0.49

0.07

0.45

0.07

MV

P9

9-2

-12

5.11

11.4

31.

627.

352.

000.

872.

120.

352.

230.

471.

280.

181.

130.

17

MV

P9

9-2

-13

1.90

3.90

0.56

2.77

0.92

0.55

1.11

0.20

1.36

0.30

0.84

0.12

0.75

0.11

MV

P9

9-2

-22

1.57

3.93

0.69

4.30

1.96

1.14

2.90

0.57

3.75

0.81

2.25

0.32

2.05

0.31

Sam

ple

ID

Ba

pp

mT

h p

pm

Nb

pp

mY

pp

mH

f p

pm

Ta

pp

mU

pp

mP

b p

pm

Rb

pp

mC

s p

pm

Sr p

pm

Sc p

pm

Zr p

pm

DE

L99

-2-0

181

0.15

0.99

5.32

0.21

0.04

0.04

0.43

3.9

0.43

482

39.2

4

DE

L2-1

04

30

107

0.19

2.48

17.0

50.

870.

160.

052.

112.

60.

1942

437

.325

DE

L2-1

04

31

2135

0.73

5.41

13.7

00.

500.

280.

181.

454.

10.

6270

139

.518

DE

L2-1

04

34

527

0.79

13.7

434

.09

3.01

0.70

0.32

0.60

9.5

3.29

366

43.1

106

MV

P1

04

36

800.

129.

2237

.94

2.54

0.59

0.06

3.17

9.5

0.08

615

51.5

103

MV

P1

04

37

870.

148.

0536

.62

2.02

0.53

0.05

3.10

8.0

0.08

655

50.9

80

MV

P1

04

38

328

0.07

0.37

4.55

0.15

0.02

0.02

0.55

3.0

0.81

561

36.9

4

MV

P9

9-2

-04

316

0.53

3.85

6.52

0.34

0.20

0.12

1.09

7.6

4.00

548

33.2

11

MV

P9

9-2

-08

630.

100.

914.

310.

150.

060.

020.

601.

70.

1444

838

.85

MV

P9

9-2

-12

637

0.37

12.1

310

.85

1.15

0.66

0.09

1.32

18.3

1.29

864

49.7

41

MV

P9

9-2

-13

770

0.22

1.30

6.97

0.38

0.07

0.05

0.62

10.1

4.80

550

40.5

11

MV

P9

9-2

-22

437

0.07

1.29

19.8

91.

410.

090.

030.

5511

.50.

4644

538

.932

Page 97: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

91

XR

F D

AT

A (

WS

U G

eo

An

aly

tica

l La

b)

Ro

ck t

yp

eG

G2

pG

2p

GE

c2

pG

2p

G2

pG

GG

2p

GG

GG

GG

G2

pG

Scp

Scp

Scp

Scp

DE

L99

-2-0

1D

EL2

-10

43

0D

EL2

-10

43

1D

EL2

-10

43

4M

VP

10

43

6M

VP

10

43

7M

VP

10

43

8M

VP

99

-2-0

4M

VP

99

-2-0

8M

VP

99

-2-1

2M

VP

99

-2-1

3M

VP

99

-2-2

2D

EL2

-10

43

0

Da

te

1

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

1-M

ay

-14

11

-Ma

y-1

41

0-M

ay

-14

Un

no

rma

lize

d M

ajo

r E

lem

en

ts (

We

igh

t %

):

SiO

2

48

.36

4

9.8

7

46

.90

4

3.9

7

45

.98

4

6.5

4

48

.01

4

9.6

4

48

.53

4

6.2

3

47

.37

5

0.3

9

49

.87

TiO

2

0.2

34

0.7

50

0.5

89

1.9

12

1.9

44

1.7

26

0.2

66

0.3

92

0.1

47

0.7

11

0.3

82

1.0

61

0.7

50

Al2

O3

1

8.9

0

17

.38

1

9.8

2

13

.69

1

6.8

9

16

.12

2

0.7

8

19

.01

1

8.3

2

18

.20

1

7.0

1

15

.53

1

7.3

8

Fe

O*

6.2

0

7.3

7

8.1

9

11

.19

1

1.6

5

11

.55

7

.09

6

.27

6

.13

1

0.5

2

7.5

1

9.1

1

7.3

7

Mn

O

0

.12

00

.14

10

.14

70

.19

10

.20

20

.21

00

.13

70

.12

50

.12

70

.17

60

.15

60

.16

20

.14

1

Mg

O

1

1.2

7

8.9

6

7.2

5

9.6

2

7.1

6

7.7

5

8.3

1

7.7

4

10

.83

8

.94

1

0.2

1

7.1

2

8.9

6

Ca

O

1

2.6

5

12

.04

1

2.8

9

14

.06

1

1.1

6

10

.55

1

3.0

1

11

.17

1

3.5

2

10

.73

1

1.0

9

9.7

3

12

.04

Na

2O

1

.34

2

.59

2

.08

2

.60

2

.49

2

.74

1

.38

3

.58

1

.13

2

.11

2

.62

4

.12

2

.59

K2

O

0

.07

0

.13

0

.15

0

.15

0

.31

0

.30

0

.11

0

.40

0

.05

0

.71

0

.50

0

.55

0

.13

P2

O5

0

.00

90

.07

80

.20

00

.12

40

.31

60

.26

60

.01

90

.05

00

.01

00

.06

10

.03

70

.02

30

.07

8

Su

m9

9.1

5

99

.32

9

8.2

3

97

.50

9

8.1

0

97

.76

9

9.1

1

98

.38

9

8.7

9

98

.38

9

6.8

9

97

.79

9

9.3

2

LOI

(%)

1.2

4

1.3

4

1.8

7

1.7

9

1.0

4

1.2

7

0.8

3

1.7

4

1.1

8

1.7

2

2.5

8

1.4

6

1.3

4

No

rma

lize

d M

ajo

r E

lem

en

ts (

We

igh

t %

):

DE

L99

-2-0

1D

EL2

-10

43

0D

EL2

-10

43

1D

EL2

-10

43

4M

VP

10

43

6M

VP

10

43

7M

VP

10

43

8M

VP

99

-2-0

4M

VP

99

-2-0

8M

VP

99

-2-1

2M

VP

99

-2-1

3M

VP

99

-2-2

2D

EL2

-10

43

0

SiO

2

48

.78

5

0.2

2

47

.75

4

5.0

9

46

.87

4

7.6

1

48

.44

5

0.4

6

49

.13

4

6.9

9

48

.89

5

1.5

3

50

.22

TiO

2

0.2

36

0.7

55

0.6

00

1.9

61

1.9

81

1.7

65

0.2

68

0.3

98

0.1

49

0.7

23

0.3

94

1.0

85

0.7

55

Al2

O3

1

9.0

6

17

.50

2

0.1

8

14

.04

1

7.2

2

16

.49

2

0.9

7

19

.33

1

8.5

5

18

.50

1

7.5

5

15

.88

1

7.5

0

Fe

O*

6.2

5

7.4

2

8.3

4

11

.48

1

1.8

8

11

.81

7

.15

6

.37

6

.21

1

0.6

9

7.7

6

9.3

2

7.4

2

Mn

O

0

.12

10

.14

20

.15

00

.19

60

.20

60

.21

50

.13

80

.12

70

.12

90

.17

90

.16

10

.16

50

.14

2

Mg

O

1

1.3

7

9.0

2

7.3

8

9.8

6

7.3

0

7.9

3

8.3

9

7.8

7

10

.96

9

.08

1

0.5

4

7.2

9

9.0

2

Ca

O

1

2.7

6

12

.12

1

3.1

3

14

.42

1

1.3

7

10

.79

1

3.1

3

11

.35

1

3.6

8

10

.91

1

1.4

5

9.9

5

12

.12

Na

2O

1

.35

2

.61

2

.12

2

.67

2

.54

2

.80

1

.39

3

.64

1

.14

2

.14

2

.70

4

.21

2

.61

K2

O

0

.07

0

.13

0

.16

0

.16

0

.31

0

.31

0

.11

0

.41

0

.05

0

.72

0

.52

0

.56

0

.13

P2

O5

0

.00

90

.07

80

.20

40

.12

70

.32

20

.27

20

.02

00

.05

10

.01

00

.06

20

.03

90

.02

40

.07

8

To

tal

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

10

0.0

0

Page 98: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

92

XR

F D

AT

A (

WS

U G

eo

An

aly

tic

al

La

b)

Ro

ck

ty

pe

GG

2p

G2

pG

Ec

2p

G2

pG

2p

GG

G2

pG

GG

GG

GG

2p

G

Sc

pS

cp

Sc

pS

cp

DE

L9

9-2

-01

DE

L2

-10

43

0D

EL

2-1

04

31

DE

L2

-10

43

4M

VP

10

43

6M

VP

10

43

7M

VP

10

43

8M

VP

99

-2-0

4M

VP

99

-2-0

8M

VP

99

-2-1

2M

VP

99

-2-1

3M

VP

99

-2-2

2D

EL

2-1

04

30

Da

te

1

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

0-M

ay

-14

10

-Ma

y-1

41

1-M

ay

-14

11

-Ma

y-1

41

0-M

ay

-14

Un

no

rma

lize

d T

rac

e E

lem

en

ts (

pp

m):

Ni

17

7

10

5

11

8

16

3

27

2

9

64

1

02

6

8

10

1

63

7

9

10

5

Cr

36

2

47

9

12

4

45

5

50

8

3

12

3

24

8

30

5

26

0

37

5

27

0

47

9

Sc

38

3

7

39

4

3

50

5

2

37

3

3

39

5

0

39

3

8

37

V1

69

2

03

2

00

3

30

3

63

3

33

1

65

1

45

1

24

3

06

1

73

2

67

2

03

Ba

81

1

15

2

16

3

53

3

86

9

1

32

9

31

9

63

6

51

7

75

4

46

1

15

Rb

5

4

6

10

1

0

9

4

8

3

20

1

1

12

4

Sr

47

9

42

0

70

0

35

9

60

4

64

0

56

3

54

7

44

6

86

3

54

3

43

5

42

0

Zr

3

25

1

9

10

6

10

2

80

4

1

1

5

42

1

1

32

2

5

Y6

1

8

14

3

4

38

3

6

5

8

5

12

8

2

0

18

Nb

1.0

2.7

5.8

13

.61

0.3

9.1

1.1

3.8

1.1

12

.91

.72

.42

.7

Ga

11

1

4

17

1

7

19

1

9

16

1

4

13

1

9

14

1

6

14

Cu

77

4

0

82

5

2

33

3

5

16

5

8

47

1

9

20

2

1

40

Zn

34

5

9

65

8

5

11

3

11

9

56

5

3

48

9

5

64

6

4

59

Pb

1

2

3

1

4

3

0

1

0

2

0

1

2

La

3

6

12

9

1

4

14

0

2

4

6

2

3

6

Ce

7

17

1

9

20

3

9

32

8

1

1

5

14

6

2

1

7

Th

0

1

1

2

1

1

0

0

0

2

0

0

1

Nd

4

9

8

14

2

7

23

3

4

2

8

2

2

9

U0

1

2

0

1

0

0

0

1

2

0

0

1

su

m t

r.1

45

8

15

57

3

59

6

22

48

1

58

9

16

08

1

39

5

15

68

1

17

8

24

84

2

10

8

17

11

1

55

7

in %

0.1

5

0.1

6

0.3

6

0.2

2

0.1

6

0.1

6

0.1

4

0.1

6

0.1

2

0.2

5

0.2

1

0.1

7

0.1

6

su

m m

+tr

99

.29

9

9.4

7

98

.59

9

7.7

3

98

.26

9

7.9

2

99

.25

9

8.5

3

98

.91

9

8.6

3

97

.10

9

7.9

6

99

.47

M+

To

xid

es

99

.34

9

9.5

2

98

.66

9

7.8

0

98

.31

9

7.9

6

99

.28

9

8.5

7

98

.95

9

8.6

9

97

.15

9

8.0

1

99

.52

w/L

OI

10

0.5

8

10

0.8

6

10

0.5

3

99

.59

9

9.3

4

99

.23

1

00

.11

1

00

.32

1

00

.12

1

00

.41

9

9.7

3

99

.47

1

00

.86

if F

e3

+1

01

.27

1

01

.68

1

01

.44

1

00

.83

1

00

.64

1

00

.51

1

00

.89

1

01

.01

1

00

.80

1

01

.57

1

00

.57

1

00

.48

1

01

.68

NiO

22

5.2

13

3.4

14

9.5

20

7.8

33

.83

6.9

81

.81

29

.98

6.3

12

8.8

80

.41

00

.81

33

.4

Cr2

O3

52

8.7

69

9.6

18

1.9

66

5.5

72

.91

21

.21

79

.93

62

.44

45

.73

80

.15

47

.73

94

.96

99

.6

Sc

2O

35

8.5

57

.05

9.5

65

.47

7.3

79

.45

6.8

50

.56

0.1

76

.25

9.7

58

.35

7.0

V2

O3

24

8.1

29

8.7

29

4.4

48

5.6

53

3.3

49

0.6

24

2.2

21

3.1

18

2.5

45

0.5

25

4.2

39

2.1

29

8.7

Ba

O9

0.5

12

8.7

24

14

.95

94

.99

6.1

10

1.9

36

7.8

35

6.6

70

.57

26

.48

65

.74

98

.31

28

.7

Rb

2O

5.6

4.0

6.9

10

.91

1.4

9.3

4.3

9.0

3.1

21

.61

2.1

13

.44

.0

SrO

56

6.3

49

7.2

82

7.5

42

4.3

71

4.7

75

7.3

66

5.8

64

7.4

52

7.0

10

20

.66

42

.65

14

.54

97

.2

ZrO

24

.63

4.4

25

.21

43

.41

37

.41

08

.25

.31

4.3

6.1

56

.91

5.4

43

.83

4.4

Y2

O3

7.1

22

.91

7.5

43

.74

8.4

45

.87

.01

0.2

6.5

14

.91

0.2

25

.62

2.9

Nb

2O

51

.43

.98

.31

9.5

14

.71

3.0

1.5

5.5

1.5

18

.52

.43

.43

.9

Ga

2O

31

5.1

18

.22

2.7

23

.22

5.0

25

.22

1.2

18

.61

6.9

26

.01

8.6

22

.01

8.2

Cu

O9

6.7

49

.91

02

.46

5.4

41

.54

3.7

20

.67

2.4

59

.42

3.9

25

.32

5.9

49

.9

Zn

O4

2.1

74

.08

0.6

10

6.4

14

0.3

14

7.8

69

.26

6.0

60

.11

18

.47

9.2

80

.37

4.0

Pb

O1

.12

.52

.70

.73

.83

.50

.30

.70

.12

.00

.00

.62

.5

La

2O

33

.47

.01

3.9

10

.51

6.1

16

.10

.22

.64

.46

.82

.33

.67

.0

Ce

O2

8.9

20

.42

3.6

24

.74

7.6

39

.39

.31

3.3

6.3

16

.67

.12

.02

0.4

Th

O2

0.0

0.9

1.0

1.8

0.6

1.2

0.3

0.0

0.0

2.1

0.0

0.1

0.9

Nd

2O

34

.51

0.3

8.9

16

.53

1.8

27

.03

.04

.82

.78

.82

.51

.91

0.3

U2

O3

0.2

0.6

2.2

0.3

1.1

0.5

0.0

0.0

0.6

2.3

0.0

0.0

0.6

Cs2

O0

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.0

As2

O5

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

W2

O3

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

su

m t

r.1

90

8

20

64

4

24

4

29

10

2

04

8

20

68

1

73

7

19

77

1

54

0

31

02

2

62

5

21

82

2

06

4

in %

0.1

9

0.2

1

0.4

2

0.2

9

0.2

0

0.2

1

0.1

7

0.2

0

0.1

5

0.3

1

0.2

6

0.2

2

0.2

1

Page 99: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

93

APPENDIX 5A – PHOTO MICROGRAPHS OF THIN SECTIONS ANALYSED

BY LA-ICP-MS

MVP10437 MVP99-2-22

MVP10438

DEL99-2-01 MVP99-2-12

DEL2-10434

Page 100: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

94

APPENDIX 5B - LA-ICP-MS RAW DATA: Including 1 sigma errors, minimum

detection limits 99% and mean raw cps background subtracted data). Please note that all

values for the internal standard(s) are reported in units of weight% oxide. All other values are

reported in ppm

SA

MP

LE

DE

L2-1

0434

GL

ITT

ER

!: T

race E

lem

en

t C

on

cen

trati

on

s M

DL

fil

tered

.

Ele

men

tD

EL

-2-1

0434-s

pt2

-grt-

aD

EL

-2-1

0434-s

pt2

-grt-

bD

EL

-2-1

0434-s

pt2

-grt-

cD

EL

-2-1

0434-s

pt2

-cp

x-a

DE

L-2

-10434-s

pt2

-cp

x-b

DE

L-2

-10434-s

pt2

-cp

x-c

DE

L-2

-10434-s

pt6

-grt-

a

Li7

<1.8

8<

1.8

0<

1.7

26.3

78.2

11.0

6<

1.9

8

Mg24

69186.4

568133.9

767505.8

861327.5

661485.6

963100.5

667473.7

8

Si2

9239390.9

5250455.3

8232364.3

4255792.4

2265636.4

1280076.0

9222135.8

1

P31

333.3

8330.8

6373.1

1126.6

8125.9

2107.2

6328.3

Ca43

7.3

27.3

27.3

218.0

618.0

618.0

67.3

2

Sc45

61.3

61.2

260.6

633.4

633.6

433.3

762.3

1

Ti4

92314.1

42312.7

62320.8

511109.8

811156.6

811277.9

92329.5

9

V51

137.9

2137.9

6139.1

454.8

8463.7

2457.4

6130.2

7

Cr52

443.0

3439.3

6435.8

2470.7

8481.6

5474.7

5781.9

5

Ni6

024.9

224.3

324.6

6178.7

9187.5

2183.9

223.5

9

Cu

65

<0.5

81.0

2<

0.5

62.4

82.3

53.2

20.8

8

Rb

85

0.0

31

<0.0

29

<0.0

28

<0.0

195

<0.0

205

1.2

35

<0.0

33

Sr88

0.4

64

0.4

55

0.4

6178.2

9180.6

5188.6

30.4

86

Y89

74.2

575.0

175.1

98.6

99.0

59.4

980.9

1

Zr90

46.9

149.5

848.5

593.3

96.6

597.7

46.4

1

Nb

93

0.0

047

0.0

109

0.0

102

0.0

682

0.0

584

0.0

927

0.0

113

Cs1

33

<0.0

0<

0.0

040

0.0

056

<0.0

036

<0.0

033

0.1

717

<0.0

061

Ba137

<0.0

29

0.0

36

<0.0

25

0.0

53

0.0

43

0.5

62

<0.0

33

La139

0.0

225

0.0

265

0.0

275

4.2

4.3

84.4

60.0

23

Ce140

0.3

46

0.3

78

0.3

84

17.2

517.9

818.5

90.3

49

Pr141

0.1

676

0.1

704

0.1

757

3.1

14

3.2

33

3.3

49

0.1

712

Nd

143

2.2

05

2.2

41

2.2

88

17.5

118.1

618.4

41.9

45

Sm

147

2.2

22

2.1

74

2.5

44.7

45.0

35.2

52.3

19

Eu

151

1.3

39

1.3

37

1.3

89

1.5

27

1.6

12

1.6

76

1.3

35

Gd

157

6.1

46.1

46.5

54.4

14.3

64.7

36.1

6

Tb

159

1.5

55

1.5

11.5

62

0.5

79

0.5

58

0.5

77

1.5

93

Dy163

11.2

611.6

12

2.4

12.5

58

2.7

44

12.2

4

Ho165

2.7

81

2.9

06

2.9

89

0.3

67

0.3

91

0.3

86

3.1

34

Er167

8.2

98.4

98.7

20.6

63

0.7

39

0.7

98

9.4

5

Tm

169

1.2

49

1.2

61.2

69

0.0

729

0.0

675

0.0

769

1.4

2

Yb

171

8.7

58.8

9.2

70.3

55

0.3

69

0.3

09

10.1

8

Lu

175

1.2

61

1.2

86

1.3

34

0.0

337

0.0

482

0.0

456

1.6

33

Hf1

78

0.6

12

0.6

71

0.6

54

3.1

93.3

82

3.5

50.6

52

Ta181

<0.0

0170

<0.0

0174

0.0

058

0.0

115

0.0

057

0.0

086

<0.0

0

Pb

208

<0.0

093

<0.0

039

0.0

038

0.0

53

0.0

742

0.0

728

0.0

189

Th

232

0.0

02

0.0

029

<0.0

00.0

336

0.0

389

0.0

256

<0.0

030

U238

0.0

057

0.0

047

<0.0

049

0.0

121

0.0

14

0.0

104

<0.0

029

Pm

147

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Po208

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

U232

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Pu

238

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Page 101: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

95

SA

MP

LE

DE

L2-1

0434

GL

ITT

ER

!: T

race E

lem

en

t C

on

cen

trati

on

s M

DL

fil

tered

.

Ele

men

tD

EL

-2-1

0434-s

pt6

-cp

x-a

DE

L-2

-10434-s

pt5

-grt-

aD

EL

-2-1

0434-s

pt5

-grt-

bD

EL

-2-1

0434-s

pt5

-grt-

cD

EL

-2-1

0434-s

pt3

-rt-

aD

EL

-2-1

0434-s

pt3

-rt-

bD

EL

-2-1

0434-s

pt3

-il-

a

Li7

7.0

1<

2.0

6<

2.0

0<

1.8

4<

1.0

5<

1.0

1<

0.9

3

Mg24

58773.4

172496.4

71399.0

972265.6

286.8

390.6

425381.0

5

Si2

9249687.0

6250868.9

7250870.2

2231705.3

<1355.7

3<

1367.5

3<

1186.7

4

P31

98.5

3289.0

3269.2

2239.0

6<

16.6

2<

16.7

7<

15.6

8

Ca43

17.8

57.8

27.8

27.8

2<

92.0

5<

96.5

3<

88.8

3

Sc45

32.5

269.7

69.2

170.0

94.1

94.6

78.7

7

Ti4

911160.5

82542.1

62508.3

32554.1

699.9

99.9

62.5

V51

437.1

4140.8

139.5

9139.1

5748.6

1707.5

8683.9

9

Cr52

662.0

8578.7

1561

566.2

6635.2

7685.8

9699.3

5

Ni6

0178.9

827.6

30.3

428.5

2<

1.2

8<

1.2

4452

Cu

65

1.9

21.0

31.5

80.6

73.4

3.3

33.1

2

Rb

85

2.4

4<

0.0

34

<0.0

30

<0.0

32

<0.0

179

<0.0

198

<0.0

193

Sr88

225.8

30.5

59

0.4

72

0.5

54

1.4

24

1.4

58

1.0

28

Y89

9.2

590.3

690.4

892.3

0.1

059

0.5

19

0.3

8

Zr90

94.1

450.0

551

51.4

41331.7

81316.7

1611.5

7

Nb

93

0.1

051

<0.0

049

0.0

121

0.0

083

724.1

5717.6

2674.6

4

Cs1

33

5<

0.0

055

<0.0

057

<0.0

062

0.0

031

<0.0

042

0.0

041

Ba137

1.5

34

<0.0

39

0.0

206

<0.0

35

<0.0

215

0.0

30.0

25

La139

4.2

10.0

30.0

308

0.0

227

<0.0

0221

<0.0

0245

0.0

794

Ce140

17.4

60.3

67

0.4

09

0.3

80.0

029

0.0

051

0.1

15

Pr141

3.1

69

0.1

737

0.1

734

0.1

703

<0.0

0180

0.0

0153

0.0

05

Nd

143

17.6

42.3

74

2.2

76

2.1

79

<0.0

134

<0.0

00.0

266

Sm

147

5.0

22.7

76

2.5

37

2.4

56

<0.0

00.1

19

<0.0

083

Eu

151

1.6

01

1.5

04

1.4

45

1.5

91

<0.0

0277

0.0

0107

<0.0

0255

Gd

157

4.3

87.1

57.2

47.0

1<

0.0

063

0.5

05

0.0

283

Tb

159

0.5

64

1.8

09

1.7

52

1.8

71

0.0

0138

0.0

0052

0.0

08

Dy163

2.6

58

14.0

714.1

414.4

8<

0.0

038

<0.0

037

0.0

419

Ho165

0.3

94

3.5

39

3.5

29

3.7

19

<0.0

0098

0.0

146

0.0

183

Er167

0.6

49

10.5

210.2

310.7

<0.0

079

<0.0

039

0.0

934

Tm

169

0.0

795

1.6

95

1.5

99

1.6

62

<0.0

0157

<0.0

0178

0.0

21

Yb

171

0.3

39

11.5

911.2

11.1

4<

0.0

134

0.0

81

0.1

43

Lu

175

0.0

386

1.7

81

1.7

58

1.8

18

0.0

0155

0.0

091

0.0

29

Hf1

78

3.2

52

0.6

28

0.5

89

0.6

74

32.1

632.1

716.5

3

Ta181

<0.0

42

<0.0

035

0.0

05

<0.0

019

67.7

768.3

361.8

Pb

208

0.0

512

<0.0

078

0.0

087

0.0

087

<0.0

058

<0.0

057

0.0

619

Th

232

0.0

384

<0.0

022

<0.0

030

0.0

053

<0.0

0143

0.0

871

0.0

753

U238

0.0

124

<0.0

030

0.0

084

0.0

072

1.1

55

1.1

49

0.4

48

Pm

147

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Po208

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

U232

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Pu

238

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Page 102: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

96

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MP

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L2

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43

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ITT

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sig

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tD

EL

-2-1

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t2-g

rt-

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rt-

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Li7

0.9

20

.78

0.7

81

.44

1.8

2.3

60

.85

Mg

24

77

75

.17

76

74

.01

76

20

.31

69

35

.57

69

70

.02

71

70

.31

76

90

.44

Si2

93

66

76

12

38

38

49

83

56

25

08

.25

39

23

10

0.7

54

07

55

38

.25

42

98

61

8.5

34

10

57

2.5

P3

12

10

.18

20

8.4

42

34

.81

79

.92

79

.43

67

.73

20

6.2

2

Ca

43

0.1

80

.18

0.1

80

.42

0.4

20

.42

0.1

8

Sc4

51

.53

1.5

31

.51

0.8

30

.84

0.8

31

.56

Ti4

95

8.4

75

8.4

25

8.5

52

75

.84

27

7.1

12

80

.13

58

.95

V5

13

.53

.53

.52

11

.35

11

.57

11

.41

3.3

1

Cr5

21

2.0

91

1.9

91

1.8

81

2.7

11

3.0

11

2.8

22

1.3

3

Ni6

01

.44

1.4

11

.39

7.7

58

.13

7.9

81

.44

Cu

65

0.2

60

.27

0.2

50

.23

0.2

30

.25

0.3

1

Rb

85

0.0

12

0.0

12

0.0

12

0.0

08

0.0

08

80

.04

60

.01

4

Sr8

80

.02

0.0

20

.01

94

.77

4.8

45

.05

0.0

21

Y8

92

2.0

22

.02

0.2

40

.25

0.2

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Page 104: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

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L2

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Page 105: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

99

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MP

LE

DE

L2

-10

43

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GL

ITT

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(99

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1365.5

1508.3

91283.4

16114.2

96181.7

369.1

1367.3

3365.0

2370.6

9180.3

9173.9

6

V51

1.0

79

0.7

29

255.2

7228.3

5717.6

1715.7

90.8

18

1.0

30.8

27

1.0

44

0.4

88

0.6

46

Cr52

<2.5

9<

2.4

5354.0

1349.1

8315.8

9322.2

1<

2.1

7<

2.4

1<

2.0

1<

1.8

8<

2.1

4<

2.2

7

Ni6

0<

3.1

13.0

635.3

834.9

5264.7

4270.1

1<

2.9

1<

3.1

8<

2.5

2<

2.4

9<

2.7

5<

2.9

5

Cu

65

<0.9

8<

0.9

72.7

2<

1.0

34.4

4.7

11.0

8<

1.0

1<

0.8

0<

0.7

8<

0.8

9<

0.9

5

Rb

85

<0.0

74

0.1

57

<0.0

45

<0.0

43

<0.0

28

<0.0

31

0.1

81

0.1

32

0.1

22

0.0

83

0.2

58

0.3

03

Sr88

1929.2

91957.5

40.2

83

0.3

18

125.2

4126.1

62048.2

12025.3

51984.8

72034.3

62485.6

52409.8

6

Y89

0.2

12

0.2

15

18.7

618.8

41.9

26

1.8

71

0.2

34

0.2

10.2

34

0.2

02

<0.0

188

<0.0

221

Zr90

0.1

67

0.1

79

28.6

524.0

966.1

166.7

30.1

44

0.1

88

0.2

21

0.2

01

<0.0

46

<0.0

49

Nb

93

<0.0

101

0.0

136

0.0

183

<0.0

073

0.2

58

0.1

95

0.0

395

0.0

398

0.0

291

0.0

244

<0.0

082

0.0

092

Cs1

33

0.0

131

<0.0

067

<0.0

078

0.0

121

<0.0

042

<0.0

053

0.0

099

<0.0

080

<0.0

082

<0.0

055

<0.0

086

<0.0

096

Ba137

60.5

962.9

1<

0.0

58

<0.0

46

<0.0

26

<0.0

47

67.0

265.6

264.4

665.9

4153.5

5147.5

3

La139

16.2

716.6

90.0

461

0.0

274

5.1

45.0

517.3

417.4

616.9

117.5

24.1

54.0

1

Ce140

27.4

827.9

20.4

67

0.4

08

17.7

418

28.7

528.8

628.4

829.5

55.1

84.9

4

Pr141

2.6

88

2.6

48

0.1

763

0.1

753

2.8

43

2.8

51

2.7

71

2.7

81

2.7

31

2.9

10.4

17

0.4

14

Nd

143

8.9

59.3

1.9

36

2.0

114.3

114.4

19.7

39.1

19.3

99.1

71.0

41

0.9

75

Sm

147

0.8

15

0.9

76

1.7

37

1.7

64

2.8

71

2.9

71.0

48

0.8

87

0.9

74

1.0

51

0.0

95

0.0

74

Eu

151

0.4

77

0.4

36

0.9

16

0.9

53

0.9

22

0.8

93

0.4

84

0.5

03

0.5

02

0.4

98

0.3

56

0.3

24

Gd

157

0.5

22

0.3

93

2.8

32.5

71.6

51

1.6

15

0.4

0.3

61

0.3

68

0.2

60.0

5<

0.0

200

Tb

159

0.0

152

0.0

267

0.5

08

0.5

06

0.1

757

0.1

553

0.0

272

0.0

248

0.0

254

0.0

277

0.0

056

<0.0

048

Dy163

0.0

88

0.0

578

3.4

83.4

80.5

95

0.5

91

0.0

92

0.0

71

0.0

93

0.0

92

<0.0

081

0.0

121

Ho165

0.0

184

0.0

072

0.7

32

0.7

56

0.0

83

0.0

97

0.0

048

0.0

099

0.0

12

0.0

145

<0.0

036

<0.0

049

Er167

<0.0

156

0.0

124

2.0

47

2.0

61

0.1

45

0.1

46

0.0

247

0.0

127

<0.0

167

0.0

099

0.0

078

<0.0

176

Tm

169

0.0

0201

0.0

0098

0.3

14

0.3

10.0

16

0.0

182

0.0

028

<0.0

043

<0.0

017

<0.0

029

<0.0

019

<0.0

020

Yb

171

<0.0

22

<0.0

214

2.4

36

2.2

26

0.0

82

0.0

7<

0.0

242

0.0

225

0.0

186

<0.0

175

0.0

264

<0.0

210

Lu

175

0.0

023

0.0

055

0.3

38

0.3

19

0.0

035

0.0

056

<0.0

022

<0.0

043

<0.0

0196

0.0

052

<0.0

031

<0.0

023

Hf1

78

<0.0

086

<0.0

121

0.4

93

0.3

47

2.5

64

2.6

34

0.0

079

<0.0

089

<0.0

071

<0.0

121

<0.0

080

<0.0

118

Ta181

<0.0

066

0.0

04

<0.0

030

0.0

086

0.0

202

0.0

27

<0.0

038

<0.0

00.0

0244

<0.0

024

<0.0

039

<0.0

0

Pb

208

3.6

53.6

10.0

402

0.1

01

0.2

30.2

69

43.8

13.6

23.9

13.5

43.3

5

Th

232

0.0

047

0.0

046

<0.0

057

<0.0

073

0.0

153

0.0

149

0.0

06

<0.0

048

<0.0

038

<0.0

045

<0.0

074

<0.0

055

U238

<0.0

054

<0.0

044

<0.0

045

0.0

045

<0.0

025

0.0

114

<0.0

050

<0.0

046

<0.0

037

0.0

036

<0.0

050

<0.0

061

Pm

147

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Po208

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

U232

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Pu

238

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

<-N

aN

Page 109: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

103

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MP

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Li7

<2

.08

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3.0

51

51

7.7

31

2.1

21

3.4

15

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1.4

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1.6

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1.0

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0.9

6

Mg

24

73

35

7.8

74

65

1.7

37

40

95

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16

70

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16

77

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66

51

0.6

56

93

47

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70

20

9.2

47

81

33

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78

16

2.9

27

83

21

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69

7.0

72

00

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Si2

92

33

13

0.5

62

28

24

5.6

32

19

02

3.8

42

33

93

9.2

23

96

16

.69

24

82

97

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25

57

68

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25

59

76

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24

11

66

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24

56

55

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24

72

55

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25

0.8

11

71

7.3

7

P3

16

5.0

21

13

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14

6.1

15

73

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66

0.7

36

3.9

46

3.2

26

6.9

49

9.2

41

35

.72

11

6.3

62

1.8

3<

16

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Ca

43

8.1

8.1

8.1

16

.56

16

.56

19

.38

19

.38

19

.38

8.2

98

.29

8.2

91

54

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89

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Sc4

57

7.8

77

8.7

67

6.8

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0.2

50

.45

34

.74

35

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34

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3.2

98

3.9

48

4.6

95

.75

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Ti4

91

50

7.0

61

53

9.2

51

46

6.2

43

71

.04

39

2.2

76

04

0.2

26

16

7.5

36

16

8.0

11

42

8.6

51

50

0.3

91

51

0.2

39

9.9

99

9.9

9

V5

12

51

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25

1.4

72

46

.71

0.9

71

1.1

13

71

4.5

97

22

.22

73

3.0

42

61

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26

8.0

52

67

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21

20

.42

07

9.5

8

Cr5

23

35

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33

2.5

63

33

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<1

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32

0.0

43

30

.24

34

2.7

56

63

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69

1.5

36

95

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79

2.7

67

79

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Ni6

03

8.8

23

9.4

63

8.7

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2.0

42

.62

64

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73

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28

1.4

53

3.7

83

6.2

63

8.0

16

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<1

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Cu

65

1.1

1.4

51

.19

<0

.59

0.7

15

.35

5.3

95

.51

0.9

91

.48

0.7

13

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3.6

9

Rb

85

0.1

27

0.0

91

<0

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20

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61

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94

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00

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09

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26

0.0

33

0.0

58

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08

Sr8

80

.85

91

.33

71

.09

72

05

0.8

22

11

8.8

41

29

.65

12

5.1

91

27

.75

0.3

01

0.3

25

0.3

31

1.3

89

1.3

93

Y8

91

9.7

71

9.8

91

9.3

70

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0.1

92

1.8

41

1.8

75

1.9

34

19

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19

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19

.73

0.2

12

0.1

08

8

Zr9

02

9.9

83

1.9

29

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0.1

71

0.1

99

67

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68

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68

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25

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26

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26

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14

68

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14

77

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Nb

93

0.0

29

20

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11

0.0

15

80

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82

0.0

44

50

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40

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70

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10

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04

0.0

08

60

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09

40

81

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41

36

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20

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80

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0.9

48

0.0

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67

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70

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31

7.9

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5.3

55

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0.0

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70

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71

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30

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31

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Ce1

40

0.4

49

0.4

83

0.4

72

30

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31

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8.3

21

8.8

11

9.0

20

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70

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70

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50

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80

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31

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41

0.2

05

60

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90

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66

2.8

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62

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22

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43

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50

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84

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15

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00

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Nd

14

32

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61

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62

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99

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10

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14

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4.5

61

4.9

82

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72

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22

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98

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78

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14

71

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41

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31

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61

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11

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2.7

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15

11

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61

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90

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40

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31

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1.7

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50

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50

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93

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16

50

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0.8

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0.7

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82

90

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67

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71

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17

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Tm

16

90

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70

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50

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80

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41

20

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48

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14

30

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20

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0.0

01

58

Yb

17

12

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42

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52

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60

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0.0

66

60

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55

0.0

52

12

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52

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7

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50

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80

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80

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57

0.0

02

50

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0.0

11

80

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0.3

91

0.3

51

0.0

62

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0.0

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33

Hf1

78

0.4

29

0.5

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97

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2.7

24

2.8

16

2.8

35

0.3

80

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30

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43

44

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Ta

18

10

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61

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0.0

04

60

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09

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0.0

01

80

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09

0.0

22

40

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01

86

0.0

02

97

0.0

02

07

37

8.5

33

85

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Pb

20

80

.03

54

0.0

19

40

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85

4.3

84

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0.3

10

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30

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4<

0.0

07

30

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91

0.0

09

40

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35

0.0

10

9

Th

23

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04

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0.0

04

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0.0

03

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0.0

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0.0

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50

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84

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77

0.0

14

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0.0

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40

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0.1

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0.0

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44

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38

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0.0

02

40

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31

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19

30

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52

0.0

04

90

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45

<0

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Page 110: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

104

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MP

LE

MV

P99-2

-12

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ITT

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men

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Li7

1.7

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61.1

71.2

12.4

92.3

83.6

44.3

72.0

82.5

11.0

21.0

6

Mg24

184.9

2178.1

8573.2

98511.4

47700.1

37821.3

7192.4

3190.0

6193.9

6192.2

21.4

121.1

2

Si2

93584655.5

3391078.5

3499859

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53669654

3757762

3298801.2

53431799

3593566.5

3592794

4676827

4677466

P31

300.8

299.1

763.6

862.6

44.6

18.6

9259.3

9306.3

9351.7

5362.7

446.2

235.5

8

Ca43

0.3

80.3

80.2

0.2

0.4

60.4

60.3

80.3

80.3

80.3

80.1

90.1

9

Sc45

0.1

60.1

61.9

92.0

10.8

80.8

80.1

50.1

70.1

40.1

30.1

50.1

6

Ti4

99.7

99.8

439.1

33.3

3153.4

155.2

29.9

39.9

49.7

79.8

65.1

95.0

7

V51

0.0

69

0.0

62

6.5

65.8

718.0

217.9

90.0

67

0.0

69

0.0

57

0.0

61

0.0

55

0.0

6

Cr52

1.1

81.0

79.8

99.7

58.6

68.8

50.9

31.0

30.9

0.8

0.9

0.9

8

Ni6

01.3

21.2

92.1

92.1

611.7

211.9

91.2

41.3

41.0

81.0

41.1

81.2

5

Cu

65

0.4

10.4

10.4

70.4

40.3

60.3

80.4

10.4

20.3

50.3

40.3

80.3

9

Rb

85

0.0

29

0.0

23

0.0

20.0

19

0.0

12

0.0

13

0.0

24

0.0

23

0.0

19

0.0

19

0.0

26

0.0

29

Sr88

52.6

253.4

50.0

19

0.0

23.4

33.4

656.3

455.8

454.7

456.1

769.5

467.6

4

Y89

0.0

15

0.0

16

0.5

30.5

30.0

60.0

59

0.0

16

0.0

16

0.0

15

0.0

14

0.0

086

0.0

097

Zr90

0.0

26

0.0

26

0.8

0.6

71.7

61.7

80.0

26

0.0

27

0.0

25

0.0

24

0.0

20.0

21

Nb

93

0.0

042

0.0

05

0.0

04

0.0

034

0.0

13

0.0

12

0.0

06

0.0

058

0.0

052

0.0

05

0.0

036

0.0

034

Cs1

33

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0.0

032

0.0

032

0.0

032

0.0

019

0.0

023

0.0

038

0.0

037

0.0

034

0.0

026

0.0

035

0.0

037

Ba137

1.7

21.7

80.0

27

0.0

18

0.0

13

0.0

21

1.9

11.8

81.8

41.8

84.3

74.2

2

La139

0.4

30.4

40.0

049

0.0

044

0.1

40.1

40.4

60.4

60.4

50.4

60.1

20.1

1

Ce140

0.7

0.7

10.0

19

0.0

17

0.4

50.4

60.7

40.7

40.7

30.7

60.1

40.1

4

Pr141

0.0

72

0.0

71

0.0

092

0.0

089

0.0

73

0.0

74

0.0

74

0.0

75

0.0

73

0.0

77

0.0

15

0.0

16

Nd

143

0.2

80.2

80.0

92

0.0

93

0.3

90.4

0.3

0.2

80.2

80.2

70.0

60.0

58

Sm

147

0.0

48

0.0

55

0.0

80.0

79

0.0

97

0.1

0.0

55

0.0

52

0.0

51

0.0

52

0.0

14

0.0

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151

0.0

22

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20.0

35

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35

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30.0

29

0.0

22

0.0

23

0.0

21

0.0

21

0.0

17

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17

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157

0.0

38

0.0

32

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10.1

0.0

64

0.0

63

0.0

34

0.0

33

0.0

29

0.0

24

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092

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159

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19

0.0

18

0.0

075

0.0

07

0.0

032

0.0

03

0.0

03

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0.0

016

0.0

017

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0.0

12

0.0

09

0.1

10.1

10.0

27

0.0

27

0.0

11

0.0

12

0.0

11

0.0

11

0.0

04

0.0

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0.0

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0.0

25

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25

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054

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0.0

078

0.0

057

0.0

77

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77

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13

0.0

13

0.0

069

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08

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169

0.0

0082

0.0

0057

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13

0.0

13

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02

0.0

022

0.0

012

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01

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171

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98

0.0

91

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11

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175

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14

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13

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Page 111: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

105

SA

MP

LE

MV

P99-2

-12

GL

ITT

ER

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sig

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men

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0.9

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33.1

13.6

82.4

92.7

53.0

80.7

30.7

10.7

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90.4

2

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9038.3

99230.1

99193.6

2208.0

4209.6

88338.2

98726.2

78867.9

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610010.5

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Si2

93613054.5

3538628

3396886.7

53629526

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3855088.7

53972526.2

53977187.2

53748438.7

53819608.7

53845877.2

56175.5

230260.2

1

P31

42.2

671.2

690.9

5353.6

6407.0

639.9

839.5

741.8

61.9

283.9

772.2

516.5

420.2

Ca43

0.2

0.2

0.2

0.3

90.3

90.4

50.4

50.4

50.2

0.2

0.2

41.3

39.7

5

Sc4

51.9

71.9

91.9

40.1

10.1

20.8

70.8

80.8

82.1

2.1

12.1

40.1

80.1

8

Ti4

939

39.8

537.9

69.8

410.6

9152.7

9156.2

1156.3

937.0

238.8

839.2

12.3

32.3

3

V51

6.4

56.4

66.3

30.0

55

0.0

67

18.0

718.2

818.5

76.7

26.8

96.8

852.3

651.3

5

Cr5

29.4

9.3

39.3

50.7

10.7

8.8

89.1

89.5

418.6

219.4

319.5

920.4

520.1

2

Ni6

02.1

62.1

72.1

20.8

90.9

612.0

612.5

212.9

21.8

61.9

62.0

60.6

90.5

7

Cu

65

0.3

60.3

50.3

50.2

60.3

10.3

40.3

50.3

50.3

0.2

90.3

0.2

80.2

7

Rb

85

0.0

19

0.0

18

0.0

13

0.0

18

0.0

68

0.0

081

0.0

085

0.0

091

0.0

13

0.0

11

0.0

13

0.0

10.0

084

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80.0

34

0.0

48

0.0

41

57.3

659.5

93.6

43.5

23.6

0.0

16

0.0

17

0.0

17

0.0

42

0.0

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0.5

60.5

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13

0.0

15

0.0

56

0.0

58

0.0

60.5

50.5

70.5

70.0

11

0.0

076

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00.8

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90.8

10.0

19

0.0

25

1.8

31.8

81.8

80.7

10.7

40.7

439.4

239.6

6

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93

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0.0

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0.0

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0.0

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0.0

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0.0

11

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12

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0.0

026

0.0

036

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33

0.0

11

0.0

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0.0

029

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0.0

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0.0

32

0.0

026

0.0

028

0.0

028

0.0

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0.0

40.0

63

0.0

21

1.9

52.5

40.0

36

0.0

14

0.0

10.0

16

0.0

19

0.0

15

0.0

13

0.0

098

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0.0

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0.0

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0.0

042

0.4

80.5

0.1

40.1

50.1

50.0

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0.0

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0.0

037

0.0

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0.0

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40

0.0

17

0.0

18

0.0

18

0.7

80.8

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90.4

90.0

17

0.0

17

0.0

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0.0

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41

0.0

093

0.0

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0.0

086

0.0

76

0.0

83

0.0

75

0.0

76

0.0

78

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0.0

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Nd

143

0.0

96

0.0

85

0.0

94

0.2

80.3

30.3

90.4

0.4

10.0

89

0.0

89

0.0

89

0.0

22

0.0

042

Sm

147

0.0

71

0.0

78

0.0

78

0.0

48

0.0

59

0.0

93

0.0

90.0

99

0.0

72

0.0

73

0.0

76

0.0

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0.0

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Eu

151

0.0

35

0.0

34

0.0

35

0.0

19

0.0

24

0.0

28

0.0

28

0.0

29

0.0

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0.0

32

0.0

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157

0.1

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10.0

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0.0

34

0.0

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0.0

60.0

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0.1

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0.0

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Ho165

0.0

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0.0

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0.0

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0.0

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0.0

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0.0

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0.0

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0.0

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0.0

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Er1

67

0.0

79

0.0

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0.0

78

0.0

069

0.0

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0.0

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0.0

12

0.0

11

0.0

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76

0.0

75

0.0

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Tm

169

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0.0

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13

0.0

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0.0

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0.0

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0.0

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0041

0.0

0056

Yb

171

0.0

93

0.0

92

0.0

83

0.0

059

0.0

029

0.0

095

0.0

093

0.0

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85

0.0

85

0.0

86

0.0

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0.0

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Lu

175

0.0

15

0.0

15

0.0

14

0.0

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0.0

01

0.0

015

0.0

015

0.0

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0.0

13

0.0

14

0.0

13

0.0

04

0.0

0079

Hf1

78

0.0

26

0.0

29

0.0

28

0.0

038

0.0

023

0.0

84

0.0

87

0.0

88

0.0

22

0.0

23

0.0

26

1.3

51.4

Ta181

0.0

016

0.0

016

0.0

013

0.0

0056

0.0

011

0.0

022

0.0

026

0.0

031

0.0

0082

0.0

0099

0.0

0085

11.6

711.9

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208

0.0

063

0.0

058

0.0

075

0.2

0.2

0.0

18

0.0

19

0.0

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0.0

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106

SA

MP

LE

MV

P99-2

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ITT

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!: M

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det

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(99%

con

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ence

).

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men

t99-2

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107

SA

MP

LE

MV

P99

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ITT

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ce).

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Page 118: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

112

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114

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20.9

74

0.9

68

1.9

41.7

8

Cu

65

0.5

68

0.5

84

0.5

19

0.3

21

0.3

12

0.5

10.6

90.3

0.4

03

0.3

07

0.3

16

0.6

37

0.5

87

Rb

85

0.0

29

0.0

276

0.0

487

0.0

168

0.0

153

0.0

273

0.0

278

0.0

146

0.0

183

0.0

164

0.0

147

0.0

277

0.0

299

Sr88

0.0

108

0.0

094

0.0

0816

0.0

0475

0.0

0852

0.0

0949

0.0

105

0.0

0566

0.0

0674

0.0

0516

0.0

0638

0.0

064

0.0

0718

Y89

0.0

112

0.0

123

0.0

123

0.0

0661

0.0

0704

0.0

117

0.0

114

0.0

0635

0.0

0757

0.0

0606

0.0

0726

0.0

115

0.0

137

Zr90

0.0

302

0.0

311

0.0

28

0.0

164

0.0

175

0.0

279

0.0

321

0.0

165

0.0

229

0.0

183

0.0

168

0.0

357

0.0

25

Nb

93

0.0

0521

0.0

0296

0.0

027

0.0

0234

0.0

016

<0.0

0000

<0.0

0000

0.0

0216

0.0

0204

0.0

0163

0.0

0162

0.0

0335

0.0

0614

Cs1

33

0.0

061

0.0

0541

0.0

0512

0.0

0222

0.0

0325

0.0

06

0.0

049

0.0

03

0.0

0273

0.0

0261

0.0

0285

0.0

0589

0.0

0562

Ba137

0.0

45

0.0

427

0.0

324

0.0

229

0.0

169

0.0

229

0.0

244

0.0

173

0.0

399

0.0

226

0.0

225

0.0

464

0.0

476

La139

0.0

0361

0.0

0355

0.0

0324

0.0

0154

0.0

0136

0.0

0243

0.0

0232

0.0

0183

0.0

0189

0.0

0175

0.0

0151

0.0

0312

0.0

0286

Ce140

<0.0

0000

0.0

0312

<0.0

0000

0.0

0213

0.0

0119

0.0

0151

0.0

0278

0.0

0139

0.0

0186

0.0

0171

0.0

0171

0.0

0176

0.0

0162

Pr141

0.0

0276

0.0

0172

0.0

0156

0.0

0068

0.0

0131

0.0

0204

0.0

0177

0.0

014

0.0

0221

0.0

0094

0.0

0149

0.0

0238

0.0

0178

Nd

143

0.0

106

0.0

104

0.0

134

0.0

0824

0.0

0975

0.0

101

0.0

215

<0.0

0000

<0.0

0000

0.0

0573

<0.0

0000

<0.0

0000

0.0

286

Sm

147

0.0

0869

<0.0

0000

0.0

078

0.0

0478

0.0

0462

0.0

143

0.0

0882

<0.0

0000

0.0

0588

0.0

0471

<0.0

0000

0.0

168

0.0

125

Eu

151

0.0

0379

<0.0

0000

0.0

038

<0.0

0000

0.0

0225

0.0

0255

0.0

0272

<0.0

0000

0.0

0181

0.0

0145

0.0

0144

0.0

0517

<0.0

0000

Gd

157

0.0

15

0.0

0854

0.0

156

0.0

0676

0.0

0653

0.0

166

0.0

125

0.0

0882

0.0

118

<0.0

0000

0.0

105

0.0

168

0.0

0887

Tb

159

0.0

0131

<0.0

0000

0.0

0166

0.0

0125

0.0

0121

<0.0

0000

0.0

0188

0.0

0133

0.0

0125

<0.0

0000

0.0

01

0.0

0146

<0.0

0000

Dy163

0.0

0734

0.0

0511

0.0

0806

<0.0

0000

<0.0

0000

<0.0

0000

0.0

0527

0.0

0264

0.0

0352

<0.0

0000

0.0

028

0.0

0579

0.0

075

Ho165

0.0

0189

0.0

0186

0.0

0169

0.0

0104

0.0

0071

0.0

0127

0.0

0192

0.0

0136

0.0

0091

0.0

0102

0.0

0072

<0.0

0000

0.0

0193

Er167

0.0

0764

0.0

0752

0.0

108

0.0

0595

0.0

0498

0.0

0892

<0.0

0000

0.0

0614

0.0

0732

0.0

0293

0.0

0583

0.0

0603

0.0

0782

Tm

169

<0.0

0000

0.0

0211

<0.0

0000

<0.0

0000

0.0

0093

0.0

0118

0.0

0178

<0.0

0000

<0.0

0000

0.0

0067

0.0

0067

0.0

0138

0.0

022

Yb

171

<0.0

0000

<0.0

0000

0.0

0819

0.0

0711

0.0

0972

0.0

195

0.0

131

0.0

0464

0.0

0875

0.0

099

0.0

0493

0.0

144

0.0

0934

Lu

175

0.0

0283

0.0

0311

0.0

0127

<0.0

0000

0.0

0075

0.0

0135

0.0

0203

0.0

0072

<0.0

0000

0.0

0077

0.0

0108

<0.0

0000

<0.0

0000

Hf1

78

0.0

089

0.0

113

0.0

0652

0.0

0566

0.0

0273

0.0

049

0.0

0904

0.0

0369

0.0

0492

0.0

0482

0.0

048

0.0

081

0.0

0525

Ta181

0.0

0351

0.0

0173

<0.0

0000

0.0

0193

0.0

0132

0.0

0334

<0.0

0000

0.0

0089

<0.0

0000

0.0

0134

0.0

0134

0.0

0276

0.0

0179

Pb

208

0.0

097

0.0

0872

0.0

0711

0.0

0436

0.0

0365

0.0

10.0

09

0.0

0403

0.0

0537

0.0

144

0.0

0302

0.0

0625

0.0

0993

Th

232

0.0

0195

0.0

0332

0.0

0247

<0.0

0000

0.0

0147

<0.0

0000

0.0

0443

0.0

161

0.0

0229

0.0

0106

<0.0

0000

0.0

0218

0.0

0346

U238

0.0

0266

0.0

0186

0.0

0415

<0.0

0000

0.0

0174

0.0

018

0.0

0192

0.0

0136

<0.0

0000

0.0

0145

0.0

0204

0.0

0422

0.0

0274

Pm

147

<0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0

Po208

<0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0

U232

<0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0

Pu

238

<0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

0<

0.0

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0.0

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0.0

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0.0

0<

0.0

0<

0.0

0

Page 121: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

115

SA

MP

LE

MV

P99-2

-22

GL

ITT

ER

!: M

inim

um

dete

cti

on

lim

its

(99%

con

fid

en

ce).

Ele

men

t99-2

-22-s

pt5

-cp

x-a

99-2

-22-s

pt5

-cp

x-b

99-2

-22-s

pt5

-pl-

a99-2

-22-s

pt5

-pl-

b99-2

-22-s

pt6

-grt-

a99-2

-22-s

pt6

-grt-

b99-2

-22-s

pt6

-cp

x-a

99-2

-22-s

pt6

-cp

x-b

99-2

-22-s

pt6

-cp

x-c

99-2

-22-s

pt6

-pl-

a99-2

-22-s

pt6

-pl-

b99-2

-22-r

t-a

99-2

-22-i

lm-a

99-2

-22-r

t-b

Li7

0.9

18

0.4

82

0.8

21

0.7

72

0.8

18

0.8

18

0.5

52

0.5

11

0.5

21

0.8

90.8

44

1.0

20.8

51

0.9

57

Mg24

2.2

71.1

82.1

12

1.9

92.1

81.4

11.4

31.4

72.3

72.2

92.4

52.0

62.3

Si2

91254.0

8693.4

61114.0

31033.5

91097.0

91169.8

766.6

7698.8

9640.4

31231.9

91256.6

11385.1

51055.3

31220.8

4

P31

14.8

28.2

13.5

212.9

913.7

13.6

79.1

68.7

28.3

915.0

414.0

615.3

314

14.6

4

Ca43

0.0

11

0.0

0635

0.0

104

0.0

102

0.0

105

0.0

105

0.0

073

0.0

0699

0.0

0675

0.0

114

0.0

11

85.3

476.8

85.0

6

Sc45

0.1

56

0.0

831

0.1

42

0.1

35

0.1

41

0.1

42

0.0

996

0.0

949

0.0

891

0.1

56

0.1

49

0.1

61

0.1

40.1

47

Ti4

90.4

62

0.2

55

0.4

23

0.4

31

0.4

32

0.3

82

0.2

94

0.3

20.2

68

0.5

12

0.4

40.0

0009

0.0

0009

0.0

0008

V51

0.1

17

0.0

233

0.0

346

0.0

40.0

40.0

431

0.0

304

0.0

25

0.0

264

0.0

526

0.0

412

0.0

509

0.0

412

0.0

43

Cr52

0.9

30.5

14

0.8

52

0.8

34

0.9

01

0.8

79

0.5

90.5

61

0.5

32

0.9

39

0.8

99

1.0

10.8

61

0.9

17

Ni6

01.2

20.6

49

1.1

31.1

1.1

21.1

10.7

64

0.7

35

0.6

84

1.2

41.1

91.3

1.1

21.2

Cu

65

0.3

83

0.2

34

0.3

96

0.3

58

0.3

75

0.3

82

0.2

38

0.2

42

0.2

38

0.4

14

0.3

98

0.4

04

0.3

42

0.4

23

Rb

85

0.0

19

0.0

089

0.0

129

0.0

171

0.0

186

0.0

156

0.0

13

0.0

235

0.0

125

0.0

194

0.0

162

0.0

18

0.0

168

0.0

185

Sr88

0.0

0523

0.0

0309

0.0

0724

0.0

0928

0.0

0407

0.0

0623

0.0

0308

0.0

0364

0.0

0351

0.0

0552

0.0

0618

0.0

0515

0.0

0526

0.0

043

Y89

0.0

0769

0.0

0446

0.0

061

0.0

0764

0.0

0691

0.0

0713

0.0

0558

0.0

0472

0.0

0478

0.0

089

0.0

0916

0.0

0838

0.0

0648

0.0

0804

Zr90

0.0

241

0.0

106

0.0

172

0.0

198

0.0

20.0

198

0.0

119

0.0

146

0.0

125

0.0

205

0.0

192

0.0

203

0.0

222

0.0

215

Nb

93

0.0

0293

<0.0

0000

0.0

0268

0.0

026

0.0

0191

0.0

0197

0.0

0264

<0.0

0000

<0.0

0000

<0.0

0000

0.0

0355

0.0

022

0.0

0276

<0.0

0000

Cs1

33

0.0

0393

0.0

0184

0.0

0373

0.0

0428

0.0

0375

0.0

0245

0.0

0212

0.0

0224

0.0

0207

0.0

189

0.0

039

0.0

0316

0.0

028

0.0

0251

Ba137

0.0

248

0.0

112

0.0

201

0.0

285

0.0

324

0.0

344

0.0

14

0.0

176

0.0

12

0.0

291

0.0

26

0.2

02

0.0

246

0.0

342

La139

0.0

0157

0.0

0087

0.0

0176

0.0

0185

0.0

0217

0.0

028

0.0

0123

0.0

0137

0.0

0104

0.0

0235

0.0

0206

0.0

062

0.0

0128

0.0

023

Ce140

<0.0

0000

0.0

006

0.0

01

<0.0

0000

0.0

0174

0.0

0147

0.0

0069

0.0

0095

<0.0

0000

<0.0

0000

0.0

0108

0.0

0116

0.0

0103

<0.0

0000

Pr141

0.0

0147

0.0

0081

0.0

0174

0.0

0107

<0.0

0000

0.0

0081

0.0

0076

0.0

0157

<0.0

0000

0.0

0201

0.0

0084

0.0

0181

0.0

008

0.0

0165

Nd

143

0.0

103

0.0

057

0.0

163

<0.0

0000

<0.0

0000

0.0

0693

0.0

0656

0.0

0448

<0.0

0000

0.0

0771

0.0

0722

0.0

0774

0.0

097

0.0

0709

Sm

147

0.0

0846

<0.0

0000

0.0

0774

0.0

0531

0.0

0551

0.0

114

0.0

0381

0.0

0367

<0.0

0000

0.0

0632

0.0

103

0.0

127

<0.0

0000

0.0

0582

Eu

151

0.0

0261

0.0

0102

0.0

0119

0.0

0164

0.0

0208

0.0

0175

0.0

0144

0.0

0196

0.0

0134

0.0

039

0.0

0129

0.0

0367

0.0

0174

0.0

022

Gd

157

0.0

0598

0.0

0331

0.0

0548

0.0

0531

0.0

078

0.0

0569

<0.0

0000

0.0

0973

0.0

0502

<0.0

0000

<0.0

0000

0.0

0636

0.0

0796

<0.0

0000

Tb

159

0.0

009

<0.0

0000

<0.0

0000

0.0

0113

0.0

0118

0.0

0149

0.0

0115

0.0

0096

<0.0

0000

0.0

0096

0.0

0127

0.0

0096

0.0

012

0.0

0088

Dy163

0.0

0506

0.0

0198

0.0

0464

0.0

0318

0.0

033

0.0

0482

0.0

0228

0.0

0311

0.0

03

0.0

0536

<0.0

0000

0.0

0659

<0.0

0000

0.0

0348

Ho165

0.0

0092

0.0

0114

0.0

0119

0.0

0082

<0.0

0000

0.0

0124

<0.0

0000

0.0

0057

0.0

0077

0.0

0098

0.0

0129

0.0

0139

0.0

0087

0.0

009

Er167

0.0

0745

0.0

0291

0.0

0683

0.0

0469

0.0

0595

0.0

0615

0.0

0412

0.0

0459

<0.0

0000

0.0

0559

0.0

0827

0.0

056

0.0

0496

0.0

131

Tm

169

0.0

0121

<0.0

0000

0.0

0175

0.0

0132

<0.0

0000

<0.0

0000

0.0

0109

0.0

0091

0.0

0072

0.0

0157

0.0

0085

0.0

0158

<0.0

0000

0.0

0083

Yb

171

0.0

0891

0.0

0603

<0.0

0000

0.0

056

0.0

101

0.0

06

0.0

0803

<0.0

0000

0.0

0374

0.0

116

0.0

108

0.0

0947

<0.0

0000

<0.0

0000

Lu

175

0.0

0098

0.0

0076

<0.0

0000

0.0

0087

0.0

009

0.0

0161

0.0

0124

0.0

006

0.0

0058

0.0

0146

0.0

0137

0.0

0104

0.0

013

0.0

0095

Hf1

78

0.0

0501

0.0

0277

<0.0

0000

0.0

0445

0.0

0326

0.0

0584

0.0

0319

0.0

0218

0.0

0297

0.0

053

0.0

0351

0.0

0376

0.0

0333

<0.0

0000

Ta181

0.0

0171

0.0

0116

0.0

0111

0.0

0107

0.0

0111

0.0

0115

0.0

0133

0.0

0105

0.0

0072

0.0

0221

0.0

012

0.0

0128

0.0

0161

0.0

0204

Pb

208

0.0

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117

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3.8

2

Tb1

59

0.0

22

40

.02

12

0.6

42

0.6

45

0.0

93

30

.00

49

0.0

75

8<0

.00

20

0.6

56

Dy1

63

0.2

10

.23

44

.12

3.9

90

.42

70

.03

26

0.4

12

0.0

38

94

.01

Ho

16

50

.05

53

0.0

63

40

.82

60

.82

50

.06

95

0.0

01

76

0.0

58

10

.00

69

0.8

39

Er1

67

0.2

09

0.2

62

.18

92

.18

10

.13

30

.01

58

0.1

76

0.0

11

12

.20

6

Tm1

69

0.0

45

0.0

52

10

.32

26

0.3

14

90

.02

62

<0.0

01

31

0.0

19

9<0

.00

40

0.3

31

Yb

17

10

.45

70

.46

61

.99

42

.11

50

.09

80

.00

78

0.0

89

20

.01

04

2.1

27

Lu1

75

0.0

64

70

.08

41

0.2

93

20

.28

83

0.0

17

5<0

.00

10

60

.01

69

<0.0

00

96

0.3

00

8

Hf1

78

0.0

52

30

.04

38

0.7

57

0.6

75

0.0

03

<0.0

08

6<0

.00

65

<0.0

04

90

.64

6

Ta1

81

<0.0

01

11

<0.0

01

23

0.0

03

53

0.0

01

29

<0.0

01

32

<0.0

01

31

<0.0

01

71

<0.0

01

19

<0.0

01

09

Pb

20

80

.00

6<0

.00

84

0.0

67

30

.05

99

1.2

89

1.0

58

1.2

94

1.0

72

0.0

64

9

Th2

32

0.0

06

50

.00

21

90

.01

84

0.0

18

8<0

.00

21

<0.0

00

.00

50

.00

35

0.0

21

U2

38

<0.0

01

21

<0.0

01

90

0.0

02

09

0.0

03

48

0.0

01

1<0

.00

20

2<0

.00

24

1<0

.00

22

4<0

.00

09

7

Pm

14

7<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

Po

20

8<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

U2

32

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN

Pu

23

8<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

Page 125: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

119

SAM

PLE

MV

P1

04

38

GLI

TTER

!: 1

sig

ma

err

or.

Ele

me

nt

10

43

8A

-sp

t1-o

px-

a1

04

38

A-s

pt1

-op

x-b

10

43

8A

-sp

t1-c

px-

a1

04

38

A-s

pt1

-cp

x-b

10

43

8A

-sp

t4-s

cp-a

10

43

8A

-sp

t4-s

cp-b

10

43

8A

-sp

t2-s

cp-a

10

43

8A

-sp

t2-p

l-a

10

43

8A

-sp

t2-c

px-

a

Li7

1.3

31

.78

1.6

61

.88

7.1

50

.38

5.7

10

.42

1.5

1

Mg2

42

54

78

.75

26

72

6.0

91

19

49

.41

12

27

4.5

31

17

.55

14

.12

11

3.7

11

5.3

51

17

11

.05

Si2

95

01

26

60

.55

26

61

26

38

15

48

7.7

53

82

48

66

.75

33

87

13

44

32

07

20

.53

30

44

87

.25

43

40

57

4.5

36

71

89

5.5

P3

14

.57

4.8

22

3.1

11

6.4

72

76

.52

77

.44

25

2.8

75

6.2

33

8.1

9

Ca4

30

.01

90

.02

0.5

30

.53

0.4

50

.45

0.4

40

.42

0.5

2

Sc4

51

.38

1.4

63

.56

3.3

10

.06

30

.07

30

.05

70

.07

33

.2

Ti4

92

4.3

31

9.9

21

17

.39

90

.06

6.9

50

.77

3.6

0.9

99

.2

V5

18

.19

8.8

91

4.3

41

4.2

20

.02

60

.02

80

.01

90

.02

81

3.4

7

Cr5

26

.47

7.2

68

.69

8.6

50

.41

0.4

50

.37

0.4

58

.38

Ni6

09

.75

11

.01

4.6

34

.67

0.5

10

.58

0.4

30

.55

4.7

3

Cu

65

0.3

20

.34

0.2

40

.28

0.1

80

.18

0.1

70

.20

.24

Rb

85

0.0

05

40

.00

59

0.0

04

40

.00

42

0.0

29

0.0

12

0.0

22

0.0

15

0.0

03

8

Sr8

80

.00

46

0.0

03

80

.59

0.6

41

5.6

11

9.9

21

5.2

11

8.9

30

.58

Y8

90

.05

50

.05

80

.64

0.6

20

.06

70

.01

0.0

63

0.0

09

20

.65

Zr9

00

.03

70

.03

50

.47

0.4

60

.00

81

0.0

09

80

.00

80

.01

0.4

7

Nb

93

0.0

01

40

.00

04

60

.00

08

10

.00

05

50

.00

08

50

.00

12

<0.0

00

.00

17

0.0

00

49

Cs1

33

0.0

00

95

0.0

01

0.0

03

50

.00

08

20

.00

28

0.0

01

80

.00

20

.00

17

0.0

00

66

Ba1

37

0.0

06

60

.00

85

0.0

06

40

.00

66

0.8

90

.89

0.8

70

.94

0.0

07

2

La1

39

0.0

01

50

.00

24

0.0

45

0.0

45

0.2

50

.06

10

.25

0.0

58

0.0

47

Ce

14

00

.00

31

0.0

04

0.2

0.1

90

.46

0.0

86

0.4

70

.08

40

.2

Pr1

41

0.0

01

10

.00

13

0.0

39

0.0

40

.05

20

.01

0.0

50

.01

0.0

4

Nd

14

30

.00

94

0.0

11

0.2

60

.26

0.2

30

.04

60

.23

0.0

44

0.2

7

Sm1

47

0.0

04

10

.00

63

0.1

0.1

0.0

50

.01

30

.04

20

.01

40

.09

8

Eu1

51

0.0

02

10

.00

18

0.0

27

0.0

27

0.0

21

0.0

15

0.0

18

0.0

16

0.0

27

Gd

15

70

.00

88

0.0

08

20

.11

0.1

10

.04

10

.00

91

0.0

34

0.0

10

.12

Tb1

59

0.0

01

60

.00

16

0.0

18

0.0

18

0.0

05

40

.00

11

0.0

03

80

.00

11

0.0

18

Dy1

63

0.0

11

0.0

12

0.1

20

.12

0.0

24

0.0

05

20

.01

90

.00

59

0.1

2

Ho

16

50

.00

29

0.0

03

20

.02

40

.02

40

.00

47

0.0

00

96

0.0

03

30

.00

13

0.0

25

Er1

67

0.0

11

0.0

13

0.0

67

0.0

67

0.0

12

0.0

03

50

.01

10

.00

47

0.0

68

Tm1

69

0.0

02

40

.00

27

0.0

09

90

.00

97

0.0

02

70

.00

05

90

.00

17

0.0

01

30

.01

Yb

17

10

.02

10

.02

20

.05

80

.06

10

.01

40

.00

44

0.0

09

50

.00

50

.06

1

Lu1

75

0.0

03

90

.00

38

0.0

08

70

.00

86

0.0

02

30

.00

05

80

.00

17

0.0

00

65

0.0

08

8

Hf1

78

0.0

05

0.0

04

70

.02

80

.02

50

.00

17

0.0

02

70

.00

22

0.0

03

0.0

24

Ta1

81

0.0

00

41

0.0

00

61

0.0

00

69

0.0

00

38

0.0

00

92

0.0

00

58

0.0

00

61

0.0

00

62

0.0

00

55

Pb

20

80

.00

19

0.0

03

30

.00

55

0.0

05

10

.07

60

.06

20

.07

40

.06

50

.00

53

Th2

32

0.0

01

10

.00

09

30

.00

17

0.0

01

70

.00

13

<0.0

00

.00

10

.00

14

0.0

01

6

U2

38

0.0

00

66

0.0

00

74

0.0

00

59

0.0

00

73

0.0

00

64

0.0

00

90

.00

08

20

.00

07

0.0

00

51

Pm

14

7<0

.00

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0<0

.00

<0.0

0<0

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<0.0

0<0

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Po

20

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0<0

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0<0

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0<0

.00

U2

32

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0<0

.00

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.00

<0.0

0<0

.00

<0.0

0<0

.00

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0

Pu

23

8<0

.00

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0<0

.00

<0.0

0<0

.00

<0.0

0<0

.00

<0.0

0<0

.00

Page 126: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

120

SAM

PLE

MV

P1

04

38

GLI

TTER

!: M

inim

um

de

tect

ion

lim

its

(99

% c

on

fid

en

ce).

Ele

me

nt

10

43

8A

-sp

t1-o

px-

a1

04

38

A-s

pt1

-op

x-b

10

43

8A

-sp

t1-c

px-

a1

04

38

A-s

pt1

-cp

x-b

10

43

8A

-sp

t4-s

cp-a

10

43

8A

-sp

t4-s

cp-b

10

43

8A

-sp

t2-s

cp-a

10

43

8A

-sp

t2-p

l-a

10

43

8A

-sp

t2-c

px-

a

Li7

0.5

84

0.5

73

0.4

37

0.4

52

0.6

45

0.8

58

0.6

67

0.7

94

0.4

21

Mg2

41

.47

1.8

21

.28

1.3

71

.78

2.6

41

.92

2.3

41

.26

Si2

97

50

.44

91

3.4

76

69

61

1.7

29

50

.58

12

75

.91

10

35

.41

12

81

.78

61

9.1

2

P3

11

0.4

51

0.9

27

.86

8.2

11

1.4

61

5.2

51

1.9

11

3.7

97

.29

Ca4

30

.00

83

70

.00

91

30

.00

67

20

.00

68

20

.00

88

40

.01

24

0.0

09

45

0.0

11

10

.00

56

9

Sc4

50

.10

20

.10

70

.08

03

0.0

83

70

.11

40

.16

20

.12

30

.15

20

.07

73

Ti4

90

.34

70

.38

80

.26

10

.33

10

.37

80

.58

30

.47

10

.50

10

.26

1

V5

10

.02

79

0.0

31

60

.02

37

0.0

24

20

.03

33

0.0

48

40

.03

46

0.0

39

60

.02

44

Cr5

20

.67

0.6

99

0.5

21

0.5

37

0.7

69

1.0

20

.80

90

.94

60

.48

1

Ni6

00

.79

10

.85

80

.64

70

.68

30

.93

91

.32

0.9

68

1.1

50

.60

9

Cu

65

0.2

38

0.2

73

0.2

13

0.2

22

0.3

46

0.4

10

.33

40

.43

10

.21

9

Rb

85

0.0

12

70

.01

40

.00

96

10

.00

92

30

.01

46

0.0

18

70

.01

55

0.0

17

90

.00

89

8

Sr8

80

.00

38

50

.00

40

10

.00

36

30

.00

36

90

.00

33

90

.02

34

0.0

03

21

0.0

07

47

0.0

04

33

Y8

90

.00

57

0.0

05

09

0.0

04

66

0.0

05

98

0.0

06

35

0.0

09

81

0.0

06

70

.00

84

0.0

04

17

Zr9

00

.01

24

0.0

14

20

.01

03

0.0

12

60

.01

52

0.0

21

70

.01

69

0.0

18

70

.01

2

Nb

93

0.0

02

33

0.0

01

49

0.0

01

91

<0.0

00

00

0.0

02

76

0.0

02

23

<0.0

00

00

<0.0

00

00

<0.0

00

00

Cs1

33

0.0

02

05

0.0

02

27

0.0

02

02

0.0

02

14

0.0

02

69

0.0

03

41

0.0

02

71

0.0

02

52

0.0

01

54

Ba1

37

0.0

16

20

.02

31

0.0

11

70

.01

48

0.0

16

90

.11

30

.01

51

0.0

27

0.0

19

7

La1

39

0.0

01

45

0.0

01

50

.00

11

10

.00

08

90

.00

14

90

.00

33

0.0

01

11

0.0

02

04

0.0

01

29

Ce

14

0<0

.00

00

00

.00

15

70

.00

05

80

.01

54

0.0

01

46

0.0

02

36

0.0

01

26

<0.0

00

00

0.0

00

57

Pr1

41

0.0

01

24

0.0

01

37

0.0

01

01

0.0

01

07

0.0

00

66

0.0

01

84

0.0

01

83

0.0

01

18

0.0

00

44

Nd

14

30

.00

82

20

.00

74

10

.00

54

80

.00

41

20

.00

79

50

.01

58

0.0

10

30

.01

01

0.0

05

34

Sm1

47

0.0

03

89

0.0

06

08

0.0

04

50

.00

33

8<0

.00

00

0<0

.00

00

00

.00

84

3<0

.00

00

00

.00

31

Eu1

51

0.0

01

20

.00

09

40

.00

15

50

.00

16

50

.00

10

10

.00

34

60

.00

21

30

.00

12

80

.00

09

6

Gd

15

70

.00

55

10

.00

60

90

.00

31

90

.00

58

60

.00

46

2<0

.00

00

00

.00

84

50

.00

58

7<0

.00

00

0

Tb1

59

0.0

00

59

<0.0

00

00

0.0

00

68

<0.0

00

00

0.0

01

21

0.0

00

98

0.0

00

74

0.0

01

98

0.0

00

66

Dy1

63

0.0

03

30

.00

25

80

.00

33

10

.00

28

70

.00

27

70

.00

38

80

.00

29

2<0

.00

00

0<0

.00

00

0

Ho

16

50

.00

06

0.0

00

66

0.0

00

70

.00

09

1<0

.00

00

00

.00

17

3<0

.00

00

00

.00

09

10

.00

04

8

Er1

67

0.0

04

22

0.0

03

80

.00

28

10

.00

29

90

.00

28

9<0

.00

00

00

.00

30

50

.00

73

40

.00

19

4

Tm1

69

0.0

00

56

<0.0

00

00

0.0

00

46

0.0

00

69

0.0

01

15

0.0

01

31

<0.0

00

00

0.0

04

04

0.0

00

45

Yb

17

10

.00

58

20

.00

64

30

.00

47

5<0

.00

00

00

.00

48

70

.00

68

3<0

.00

00

00

.00

62

0.0

04

64

Lu1

75

0.0

05

62

0.0

01

22

0.0

00

73

0.0

00

78

0.0

00

75

0.0

01

06

0.0

00

80

.00

09

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0.0

01

32

0.0

01

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0.0

01

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0.0

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19

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Pb

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80

.00

30

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83

70

.00

20

60

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26

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.00

21

20

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72

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10

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Page 127: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

121

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20

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49

52

44

41

15

56

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89

81

64

13

41

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16

15

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21

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78

62

27

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62

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33

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99

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18

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13

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45

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65

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65

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11

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81

48

88

50

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25

38

42

93

12

53

85

91

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74

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01

43

52

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45

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37

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13

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22

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23

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57

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53

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122

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41

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12

51

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5.7

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71

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47

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23

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10

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20

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12

50

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60

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01

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40

.00

31

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01

67

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03

58

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01

78

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01

75

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01

86

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01

73

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21

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15

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59

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15

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0.3

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76

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43

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91

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75

2.0

87

0.0

06

17

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25

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02

26

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46

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05

0.4

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73

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18

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16

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66

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30

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70

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86

3.7

93

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54

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59

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76

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2.9

37

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56

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55

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27

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59

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11

40

.01

11

0.5

27

0.5

11

0.4

76

0.5

43

0.5

39

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09

07

0.0

07

07

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12

3

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43

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3.6

0.0

98

20

.09

91

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86

Ho

16

50

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14

0.0

41

0.7

96

0.7

88

0.7

59

0.8

07

0.7

71

0.0

30

80

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05

0.0

27

1

Er1

67

0.1

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22

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42

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91

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43

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27

90

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45

7

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0.0

34

90

.03

98

0.3

22

0.3

13

0.2

85

20

.30

49

0.3

01

30

.02

40

.02

75

0.0

25

5

Yb

17

10

.33

60

.31

82

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71

.99

11

.73

2.0

31

.84

10

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20

.35

50

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6

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75

0.0

81

80

.08

04

0.2

87

0.2

64

40

.26

80

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73

0.2

74

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47

0.0

52

20

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04

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40

40

.04

35

0.7

11

0.6

81

0.6

91

0.7

90

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80

.02

40

.02

26

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39

1

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01

04

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01

50

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01

45

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01

27

0.0

01

53

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01

16

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00

96

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00

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.02

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57

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20

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39

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06

60

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56

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04

50

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32

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Page 129: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

123

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1

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52

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49

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11

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50

52

63

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6.4

71

75

28

26

4

P3

11

8.4

8<1

3.5

3<1

3.9

5<6

.74

<6.9

5<9

.02

<43

2.0

1<7

.17

<44

5.8

2

Ca4

31

8.2

51

8.2

51

8.2

52

2.9

12

2.9

10

.47

22

.63

22

.63

22

.63

Sc4

51

.23

50

.99

40

.63

61

04

.39

10

6.3

63

5.8

71

82

8.6

21

13

.71

97

5.5

1

Ti4

95

8.6

26

9.7

94

3.8

73

97

0.3

34

03

4.9

66

27

.76

34

29

7.3

94

40

0.0

93

43

46

.18

V5

15

.66

4.9

82

.72

34

50

.32

45

6.0

32

39

.58

11

63

1.8

44

62

.06

12

96

9.6

8

Cr5

21

4.9

77

.99

6.4

59

53

.34

98

0.3

57

40

.03

33

86

6.2

39

58

.18

36

87

2

Ni6

02

.04

<1.1

1<1

.22

98

.77

10

4.1

62

45

.11

16

10

.15

97

.29

12

48

1.1

6

Cu

65

<0.4

60

.95

<0.3

91

.91

1.6

83

.18

16

0.4

61

.65

15

7.6

Rb

85

0.0

31

60

.09

20

.04

02

0.0

10

2<0

.00

89

<0.0

14

1<0

.63

<0.0

10

2<0

.65

Sr8

85

94

.14

72

2.5

85

87

.33

16

.12

16

.07

0.0

11

10

.31

51

4.7

10

.42

Y8

90

.18

90

.16

30

.17

71

7.0

91

80

.95

84

4.4

11

9.1

54

7.9

8

Zr9

00

.07

50

.04

70

.04

56

.61

6.8

90

.37

62

0.0

88

.51

20

.71

Nb

93

0.0

02

35

<0.0

02

8<0

.00

20

90

.02

56

0.0

14

40

.00

19

10

.10

10

.01

18

0.1

27

Cs1

33

<0.0

0<0

.03

1<0

.00

37

<0.0

01

70

<0.0

01

67

<0.0

02

43

<0.1

35

<0.0

01

94

<0.1

13

Ba1

37

13

.54

16

.59

12

.95

<0.0

16

20

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15

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14

1<1

.03

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10

8<1

.01

La1

39

0.5

71

0.5

45

0.5

77

0.2

83

0.2

89

0.0

01

24

<0.0

62

0.3

12

<0.0

62

Ce

14

01

.01

81

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31

.07

51

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91

.65

40

.00

10

60

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61

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90

.13

8

Pr1

41

0.1

26

90

.13

25

0.1

07

40

.41

0.4

29

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00

84

<0.0

38

0.4

56

0.1

33

Nd

14

30

.47

80

.50

20

.47

3.3

3.4

9<0

.00

88

<0.3

33

.96

0.7

5

Sm1

47

0.0

81

60

.03

93

0.0

36

51

.74

11

.65

0.0

09

40

.39

1.8

67

0.2

8

Eu1

51

0.2

62

0.2

54

0.2

33

0.7

34

0.7

37

<0.0

02

20

.30

50

.80

.37

8

Gd

15

70

.09

60

.06

80

.08

32

.50

22

.67

80

.02

51

.68

2.9

83

2.2

8

Tb1

59

0.0

10

80

.01

38

0.0

05

54

0.4

58

0.5

0.0

12

0.5

39

0.5

25

0.5

58

Dy1

63

0.0

38

90

.03

89

0.0

28

93

.33

.43

0.1

30

65

.33

.69

5.8

8

Ho

16

50

.00

79

0.0

09

60

.00

78

0.7

15

0.7

52

0.0

33

71

.65

0.7

91

1.8

2

Er1

67

0.0

15

0.0

26

40

.02

52

1.9

44

1.9

91

0.1

55

55

.04

2.1

47

6.5

8

Tm1

69

<0.0

01

60

0.0

02

80

.00

19

50

.26

63

0.2

80

10

.03

32

1.6

0.3

01

1.4

9

Yb

17

10

.01

08

<0.0

06

10

.01

76

1.6

95

1.8

42

<0.0

49

12

.72

.10

31

4.9

4

Lu1

75

<0.0

01

48

<0.0

03

4<0

.00

14

00

.24

11

0.2

62

80

.06

27

2.6

20

.28

18

2.9

2

Hf1

78

0.0

04

0.0

09

90

.00

59

0.5

03

0.5

09

<0.0

40

1.5

20

.60

92

.12

Ta1

81

0.0

00

69

<0.0

01

16

<0.0

02

45

<0.0

01

32

<0.0

00

64

<0.0

05

0<0

.03

9<0

.00

12

9<0

.05

5

Pb

20

80

.32

70

.35

60

.33

10

.02

45

0.0

17

80

.00

86

0.6

80

.03

11

0.3

2

Th2

32

<0.0

0<0

.00

13

2<0

.00

13

90

.00

37

20

.00

74

2<0

.00

13

5<0

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40

.00

36

3<0

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9

U2

38

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02

02

<0.0

01

28

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02

34

0.0

02

61

0.0

04

28

0.0

00

43

17

.30

.00

47

6<0

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1

Pm

14

7<-

NaN

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aN<-

NaN

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aN<-

NaN

<-N

aN<-

NaN

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aN<-

NaN

Po

20

8<-

NaN

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aN<-

NaN

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aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

U2

32

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aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN

Pu

23

8<-

NaN

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aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

<-N

aN<-

NaN

Page 130: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

124

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DEL

99

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Li7

0.4

70

.61

0.6

0.3

80

.33

0.3

50

.51

0.2

40

.44

0.5

1

Mg2

43

84

85

.39

37

75

4.7

21

30

75

.92

13

53

1.5

41

47

16

.43

14

13

7.6

11

40

77

.81

25

20

0.1

62

80

97

.07

28

43

8.9

7

Si2

96

18

05

66

64

76

90

1.5

40

66

36

2.2

53

96

62

19

40

35

19

6.7

53

90

49

78

.75

40

08

75

2.7

54

21

65

96

.54

63

96

33

.54

52

65

56

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P3

16

.32

5.3

89

.62

5.0

74

.03

3.8

21

0.1

7.4

13

.37

6.2

4

Ca4

30

.01

70

.01

70

.53

0.5

30

.53

0.5

30

.53

0.0

11

0.0

11

0.0

12

Sc4

51

.38

1.3

63

.11

2.9

12

.92

3.1

22

.93

0.8

80

.93

1

Ti4

92

6.0

52

61

29

.78

11

9.3

91

14

.96

13

3.0

21

17

.41

15

.51

7.3

91

8.9

V5

19

.33

9.0

31

3.0

11

2.6

41

2.3

11

2.7

71

2.4

75

.83

6.2

26

.73

Cr5

23

0.3

43

1.2

63

0.4

22

9.9

13

0.0

83

0.3

53

0.5

20

.32

21

.44

22

.64

Ni6

01

6.1

81

6.7

65

.55

5.4

95

.49

5.4

65

.87

10

.81

2.4

12

.67

Cu

65

0.3

10

.29

0.1

60

.15

0.1

40

.14

0.1

40

.20

.21

0.2

5

Rb

85

0.0

06

80

.00

58

0.0

04

30

.00

45

0.0

03

80

.00

46

0.0

04

70

.00

44

0.0

04

40

.00

46

Sr8

80

.00

30

.00

25

0.5

0.5

30

.53

0.5

40

.56

0.0

03

0.0

02

60

.00

25

Y8

90

.04

40

.04

30

.64

0.6

40

.60

.65

0.6

30

.03

0.0

32

0.0

33

Zr9

00

.02

50

.02

60

.32

0.3

10

.31

0.3

60

.34

0.0

20

.02

0.0

2

Nb

93

0.0

01

30

.00

09

90

.00

15

0.0

01

90

.00

13

0.0

01

70

.00

16

0.0

00

81

0.0

00

79

0.0

00

71

Cs1

33

0.0

01

10

.00

12

0.0

00

83

0.0

00

87

0.0

00

74

0.0

00

79

0.0

00

78

0.0

00

76

0.0

00

81

0.0

00

91

Ba1

37

0.0

10

.01

20

.00

72

0.0

06

0.0

06

0.0

07

20

.00

63

0.0

07

70

.00

65

0.0

06

7

La1

39

0.0

00

76

0.0

00

82

0.0

12

0.0

12

0.0

12

0.0

13

0.0

14

0.0

00

44

0.0

00

64

0.0

00

54

Ce

14

00

.00

06

90

.00

06

0.0

59

0.0

58

0.0

59

0.0

63

0.0

64

0.0

00

84

0.0

00

95

0.0

00

5

Pr1

41

0.0

00

72

0.0

00

52

0.0

15

0.0

15

0.0

15

0.0

16

0.0

16

0.0

00

31

0.0

00

47

0.0

00

31

Nd

14

30

.00

56

0.0

04

0.1

20

.12

0.1

20

.13

0.1

30

.00

38

0.0

03

50

.00

34

Sm1

47

0.0

03

50

.00

53

0.0

65

0.0

63

0.0

57

0.0

63

0.0

63

0.0

02

70

.00

31

0.0

02

9

Eu1

51

0.0

01

80

.00

16

0.0

23

0.0

23

0.0

22

0.0

23

0.0

23

0.0

02

40

.00

12

0.0

01

1

Gd

15

70

.00

65

0.0

05

30

.09

0.0

94

0.0

82

0.0

94

0.0

94

0.0

04

60

.00

51

0.0

05

2

Tb1

59

0.0

01

30

.00

13

0.0

16

0.0

15

0.0

14

0.0

16

0.0

16

0.0

00

90

.00

08

50

.00

11

Dy1

63

0.0

09

60

.00

83

0.1

10

.11

0.0

99

0.1

10

.11

0.0

06

50

.00

67

0.0

06

3

Ho

16

50

.00

26

0.0

02

60

.02

50

.02

40

.02

30

.02

50

.02

40

.00

19

0.0

01

90

.00

18

Er1

67

0.0

12

0.0

11

0.0

67

0.0

67

0.0

64

0.0

66

0.0

69

0.0

07

80

.00

75

0.0

08

8

Tm1

69

0.0

02

30

.00

25

0.0

10

.01

0.0

09

20

.00

98

0.0

09

70

.00

16

0.0

01

80

.00

17

Yb

17

10

.02

0.0

19

0.0

61

0.0

60

.05

20

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0.0

55

0.0

13

0.0

18

0.0

14

Lu1

75

0.0

04

0.0

04

0.0

08

90

.00

83

0.0

08

20

.00

90

.00

84

0.0

02

40

.00

27

0.0

02

6

Hf1

78

0.0

04

60

.00

54

0.0

28

0.0

27

0.0

27

0.0

30

.02

80

.00

29

0.0

03

0.0

04

7

Ta1

81

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00

59

0.0

00

62

0.0

00

72

0.0

00

64

0.0

00

61

0.0

00

52

0.0

00

48

0.0

00

35

<0.0

00

.00

03

6

Pb

20

80

.00

30

.00

27

0.0

03

40

.00

22

0.0

02

10

.00

27

0.0

02

90

.00

16

0.0

01

70

.00

14

Th2

32

0.0

00

73

0.0

00

33

0.0

01

0.0

01

20

.00

10

.00

11

0.0

02

50

.00

06

20

.00

03

40

.00

07

3

U2

38

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0.0

00

77

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01

0.0

00

87

0.0

00

79

0.0

00

75

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00

64

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90

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4

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.00

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0<0

.00

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.00

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0

Page 131: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

125

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1

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80

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19

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72

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2

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43

62

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16

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88

7.4

91

55

80

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15

54

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93

46

93

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81

01

49

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18

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94

51

33

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05

04

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66

83

58

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90

72

26

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39

75

36

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55

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39

25

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20

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27

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31

55

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32

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11

86

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92

03

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0.4

30

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0.5

30

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14

0.6

70

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50

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30

.08

70

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22

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2.7

71

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53

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2.9

75

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6

Ti4

91

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1.4

91

10

.36

11

2.4

19

.31

10

62

.75

12

3.3

31

09

1.6

8

V5

10

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0.1

70

.09

21

2.3

12

.48

7.2

23

53

.13

12

.71

40

3.4

4

Cr5

20

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0.5

40

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30

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31

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25

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11

64

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30

.61

12

94

.99

Ni6

00

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0.5

90

.54

5.8

26

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14

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70

7.8

55

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77

1.5

9

Cu

65

0.1

90

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0.1

80

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0.1

50

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12

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13

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Rb

85

0.0

08

40

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30

.00

82

0.0

04

30

.00

41

0.0

05

60

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0.0

04

80

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Sr8

82

0.3

72

4.9

12

0.2

90

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0.5

60

.00

25

0.0

97

0.5

20

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Y8

90

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10

.01

20

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0.5

90

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0.0

38

1.7

80

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1.9

7

Zr9

00

.01

10

.01

30

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10

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0.2

30

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91

0.2

91

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Nb

93

0.0

00

96

0.0

01

40

.00

09

20

.00

23

0.0

01

90

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08

90

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40

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17

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43

Cs1

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00

.02

30

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17

0.0

00

72

0.0

00

71

0.0

00

93

0.0

52

0.0

00

88

0.0

46

Ba1

37

0.5

0.6

20

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0.0

06

0.0

07

0.0

05

60

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57

0.4

1

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0.0

21

0.0

22

0.0

21

0.0

10

.01

10

.00

04

50

.02

50

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20

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Ce

14

00

.03

40

.03

80

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60

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0.0

52

0.0

00

36

0.0

28

0.0

60

.03

6

Pr1

41

0.0

05

80

.00

71

0.0

05

20

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30

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40

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03

40

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60

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50

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8

Nd

14

30

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0.0

37

0.0

29

0.1

10

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0.0

04

30

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0.1

30

.19

Sm1

47

0.0

09

90

.00

97

0.0

06

50

.06

0.0

58

0.0

03

0.1

40

.06

60

.16

Eu1

51

0.0

12

0.0

14

0.0

11

0.0

22

0.0

22

0.0

01

10

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90

.02

50

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4

Gd

15

70

.01

20

.01

20

.01

0.0

82

0.0

88

0.0

04

50

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0.1

0.3

5

Tb1

59

0.0

01

50

.00

20

.00

09

80

.01

40

.01

50

.00

12

0.0

56

0.0

16

0.0

61

Dy1

63

0.0

05

50

.00

74

0.0

07

50

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0.0

08

30

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0.1

20

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Ho

16

50

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13

0.0

01

80

.00

14

0.0

23

0.0

24

0.0

02

20

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0.0

26

0.1

3

Er1

67

0.0

04

10

.00

65

0.0

04

90

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40

.06

60

.00

97

0.3

70

.07

20

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Tm1

69

0.0

00

75

0.0

01

10

.00

07

80

.00

87

0.0

09

30

.00

21

0.1

0.0

10

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Yb

17

10

.00

47

0.0

04

0.0

04

60

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10

.05

60

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0.7

70

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40

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Lu1

75

0.0

00

72

0.0

01

20

.00

06

90

.00

75

0.0

08

20

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32

0.1

40

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90

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Hf1

78

0.0

02

30

.00

42

0.0

02

0.0

21

0.0

21

0.0

17

0.2

0.0

26

0.2

4

Ta1

81

0.0

00

40

.00

07

50

.00

07

60

.00

06

10

.00

02

70

.00

17

0.0

17

0.0

00

64

0.0

22

Pb

20

80

.02

40

.02

80

.02

40

.00

30

.00

26

0.0

02

20

.12

0.0

03

90

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Th2

32

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00

.00

04

10

.00

07

60

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07

70

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09

80

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05

50

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90

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09

30

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63

0.0

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83

0.0

00

84

0.0

00

74

0.0

00

92

0.0

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25

0.9

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70

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5

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0<0

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0<0

.00

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Page 132: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

126

SAM

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DEL

99

-2-0

1

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Li7

0.7

08

0.6

98

0.4

61

0.5

02

0.4

05

0.4

37

0.4

15

0.5

24

0.4

63

0.4

62

Mg2

42

.04

2.1

41

.48

1.5

21

.28

1.4

11

.47

1.4

41

.61

1.6

5

Si2

91

06

2.4

41

05

8.0

96

15

.22

63

0.7

46

36

.62

71

3.9

96

47

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58

6.2

47

87

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76

4.0

6

P3

11

1.7

51

2.1

28

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8.4

67

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7.3

37

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7.0

37

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8.1

1

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30

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01

0.0

10

10

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68

10

.00

66

40

.00

57

20

.00

59

30

.00

57

70

.00

56

80

.00

66

50

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69

7

Sc4

50

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60

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0.0

91

60

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66

0.0

75

20

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12

0.0

79

50

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93

0.0

85

30

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89

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90

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80

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60

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0.2

91

0.2

16

0.2

45

0.2

89

0.3

08

0.3

21

0.2

62

V5

10

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18

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37

60

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83

0.0

27

20

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14

0.0

24

50

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31

0.0

23

70

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84

0.0

26

3

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20

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20

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0.5

83

0.5

76

0.5

02

0.5

13

0.5

08

0.4

93

0.5

42

0.5

57

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00

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41

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0.6

98

0.7

18

0.5

94

0.6

17

0.6

51

0.6

28

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89

0.7

07

Cu

65

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49

0.3

64

0.2

34

0.2

45

0.1

99

0.1

99

0.2

17

0.2

09

0.2

41

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25

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85

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14

90

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45

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10

20

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08

0.0

08

57

0.0

11

40

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10

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0.0

10

60

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01

Sr8

80

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53

40

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38

40

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31

20

.00

35

70

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24

50

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32

70

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34

70

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44

30

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31

40

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27

1

Y8

90

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60

80

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63

60

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46

0.0

04

53

0.0

05

31

0.0

04

36

0.0

04

50

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37

50

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52

90

.00

52

9

Zr9

00

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02

0.0

18

10

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37

0.0

12

60

.01

07

0.0

11

30

.01

28

0.0

11

30

.01

06

0.0

13

9

Nb

93

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00

00

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00

00

0.0

01

24

0.0

01

25

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00

00

0.0

01

62

0.0

02

31

0.0

01

60

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12

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00

0

Cs1

33

0.0

02

40

.00

22

60

.00

16

70

.00

14

30

.00

17

80

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17

50

.00

18

60

.00

17

30

.00

22

10

.00

21

6

Ba1

37

0.0

22

60

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72

0.0

15

0.0

15

90

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40

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84

0.0

15

40

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03

0.0

12

30

.01

62

La1

39

0.0

01

79

0.0

01

82

0.0

01

06

0.0

00

68

0.0

01

50

.00

13

80

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14

60

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07

50

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14

30

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8

Ce

14

00

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09

40

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00

00

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06

60

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05

60

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06

10

.00

12

20

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06

0.0

00

66

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00

00

Pr1

41

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01

46

0.0

01

05

0.0

00

51

0.0

01

03

0.0

00

61

0.0

01

06

0.0

00

67

0.0

00

66

0.0

01

03

0.0

00

74

Nd

14

30

.00

88

70

.00

63

80

.00

75

90

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62

60

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64

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00

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00

00

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39

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44

20

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7

Sm1

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05

14

0.0

07

39

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03

62

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05

28

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03

32

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00

00

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04

63

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05

12

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51

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02

25

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01

98

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01

11

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01

37

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00

67

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01

45

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24

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27

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76

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36

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57

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27

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29

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59

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01

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95

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80

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97

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20

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30

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05

20

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Er1

67

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45

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34

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03

19

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06

83

0.0

02

71

0.0

03

61

0.0

02

98

0.0

02

06

0.0

03

22

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Tm1

69

0.0

00

74

0.0

00

75

0.0

00

90

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05

20

.00

04

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00

00

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06

80

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06

70

.00

07

40

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3

Yb

17

10

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77

10

.00

96

0.0

03

81

0.0

06

66

0.0

08

55

0.0

04

98

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00

00

0.0

06

01

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00

00

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05

54

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00

86

0.0

00

59

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01

45

0.0

00

50

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07

70

.00

05

50

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09

30

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08

40

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Hf1

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38

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00

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56

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15

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50

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14

50

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12

70

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10

70

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11

60

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09

60

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Pb

20

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33

50

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53

90

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23

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00

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35

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42

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44

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Page 133: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

127

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PLE

DEL

99

-2-0

1

GLI

TTER

!: M

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um

de

tect

ion

lim

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(99

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Ele

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DEL

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52

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2.6

2.8

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88

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1.5

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91

45

2.7

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9.6

11

42

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59

0.6

56

95

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69

1.6

54

53

69

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56

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59

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44

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30

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18

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70

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08

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05

45

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05

41

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07

05

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49

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73

0.3

69

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60

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90

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90

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65

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76

60

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24

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50

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30

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22

14

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62

16

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45

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42

0.0

20

90

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35

0.0

33

21

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23

31

.67

Cr5

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80

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0.9

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82

0.5

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33

29

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98

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Cu

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57

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0.0

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80

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20

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89

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40

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60

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5

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83

70

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20

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49

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70

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0.6

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9

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00

00

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01

67

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43

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70

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60

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20

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68

0.0

02

27

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15

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01

11

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00

55

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80

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00

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50

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00

75

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00

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01

49

0.0

00

59

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54

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00

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11

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71

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20

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6

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59

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63

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0.0

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85

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99

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99

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12

30

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30

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04

60

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50

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00

00

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43

80

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47

60

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1

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75

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48

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39

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01

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09

60

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01

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54

30

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80

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00

00

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0.0

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45

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01

32

0.0

00

64

0.0

04

98

0.0

38

70

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12

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54

Pb

20

80

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58

90

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37

40

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39

50

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26

90

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25

30

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33

20

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50

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32

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0<0

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0<0

.00

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0<0

.00

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128

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1

GLI

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!: M

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Raw

CP

S b

ackg

rou

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71

83

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41

51

16

31

59

26

00

19

52

32

Mg2

41

06

45

01

11

01

87

89

85

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86

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51

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66

47

42

56

58

52

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72

90

65

10

21

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34

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37

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97

70

87

93

77

14

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52

87

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48

10

18

18

17

82

3

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73

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11

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32

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32

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75

52

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81

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53

53

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33

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32

32

53

15

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93

12

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62

72

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99

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02

58

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25

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63

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69

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8

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51

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81

41

05

13

77

01

60

92

15

12

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45

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30

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0

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65

46

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11

29

32

51

30

92

84

24

54

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82

52

13

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45

39

49

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61

99

44

22

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54

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39

01

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91

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71

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38

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31

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33

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31

33

83

33

23

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58

02

54

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33

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93

91

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51

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59

81

52

51

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69

61

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61

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51

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84

20

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11

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74

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71

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22

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52

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59

44

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86

27

67

30

23

32

66

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11

54

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66

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63

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21

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50

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50

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52

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56

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57

15

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25

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70

44

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67

17

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49

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27

27

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30

34

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81

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91

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54

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82

66

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42

99

29

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11

17

12

11

11

07

36

31

53

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81

20

43

70

20

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32

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01

16

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22

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14

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22

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00

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129

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d.

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me

nt

DEL

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97

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29

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03

25

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54

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01

02

63

98

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18

27

37

21

92

74

00

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81

45

15

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64

91

94

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50

44

61

59

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25

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63

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86

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64

59

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48

67

31

41

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59

57

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68

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30

66

73

11

10

14

96

73

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18

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65

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23

33

67

30

14

42

47

72

82

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9

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85

29

94

38

20

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88

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51

10

89

99

84

27

06

48

71

74

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39

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71

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51

22

50

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78

38

48

36

79

00

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20

83

20

38

83

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11

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90

01

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23

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11

17

11

18

31

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01

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11

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74

80

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65

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62

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49

60

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50

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60

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01

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60

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21

34

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45

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26

5.6

72

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15

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26

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0.9

79

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93

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93

4.9

93

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88

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51

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42

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52

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68

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15

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94

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32

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66

1.8

72

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13

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31

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72

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32

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72

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82

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32

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71

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64

0.6

63

22

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16

15

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53

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64

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0.0

47

0.0

54

23

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63

21

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22

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21

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22

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22

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45

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25

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62

24

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49

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45

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16

54

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34

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41

3.9

70

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41

0.0

36

65

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14

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14

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67

11

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11

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11

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12

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55

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59

10

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51

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96

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25

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3

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25

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36

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51

1.6

59

11

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38

0.0

07

11

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12

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12

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17

19

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10

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9.7

10

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10

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10

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10

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42

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56

10

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11

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51

10

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72

19

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11

70

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47

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88

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20

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33

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3.8

43

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6.5

80

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12

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73

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93

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0.0

17

60

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16

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13

30

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67

0.0

65

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01

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80

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40

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50

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60

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61

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7<-

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8<-

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NaN

Page 137: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

131

SAM

PLE

MV

P10

437

GLI

TTER

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sig

ma

err

or.

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ent

1043

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x-a

1043

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x-b

1043

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x-c

1043

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x-d

1043

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x-e

1043

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t1-p

x-f

1043

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l-a

1043

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1043

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1043

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t2-p

x-b

1043

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3.08

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2613

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2.63

169.

2859

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1555

1.43

1226

287.

2512

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0.5

4076

597

4263

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541

4839

7.25

2565

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858

0893

561

8635

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522

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2.68

2.85

163.

2326

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19.9

35.

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7.92

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24

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30.

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530.

530.

530.

640.

420.

420.

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630.

64

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4.46

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63.0

80.

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54.

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3

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46.5

744

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379.

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882.

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531.

4652

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39.

739.

9910

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9.47

211.

580.

061

0.05

611

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3222

4.75

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25.

215.

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325.

334.

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5.57

0.49

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108.

0710

9.07

Ni6

01.

271.

281.

441.

51.

412

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0.63

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105.

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Cu

650.

120.

110.

130.

120.

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20.

260.

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9.4

Rb

850.

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015

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350.

220.

21

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0.44

0.42

0.48

0.49

0.46

0.11

24.4

324

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0.8

0.13

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3.99

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94.

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20.

20.

20.

190.

160.

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1

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230.

230.

240.

230.

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143

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1.56

1.55

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1.58

0.54

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0.3

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0.64

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70.

550.

570.

550.

570.

570.

540.

046

0.05

0.63

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10.

081

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70.

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70.

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120.

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157

0.63

0.67

0.63

0.66

0.66

0.88

0.03

20.

037

0.72

0.84

0.81

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90.

098

0.1

0.09

80.

10.

10.

190.

0033

0.00

370.

110.

20.

2

Dy1

630.

650.

680.

660.

680.

71.

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015

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70.

751.

841.

73

Ho

165

0.14

0.14

0.14

0.14

0.15

0.52

0.00

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003

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0.55

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70.

360.

370.

360.

380.

392.

090.

0079

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10.

412.

332.

26

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90.

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90.

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0009

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0014

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40.

470.

45

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250.

270.

250.

260.

273.

490.

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3.54

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50.

035

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70.

037

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70.

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0.00

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001

0.04

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780.

130.

120.

130.

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130.

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0029

0.00

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130.

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26

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0006

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208

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150.

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0009

50.

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220.

0008

80.

0017

0.00

088

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147

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0

Page 138: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

132

SAM

PLE

MV

P1

04

37

GLI

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!: M

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ce).

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me

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10

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94

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18

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41

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91

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98

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84

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44

3.4

65

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55

7.8

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47

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29

82

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71

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47

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52

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40

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49

20

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40

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80

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80

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04

69

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50

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59

70

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50

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62

43

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70

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.21

30

.23

50

.26

51

3.6

70

.60

90

.70

60

.20

71

1.4

11

3.8

6

V5

10

.01

85

0.0

20

60

.02

10

.02

19

0.0

19

41

.25

0.0

61

40

.05

57

0.0

21

31

.28

1.3

3

Cr5

20

.38

30

.38

50

.40

80

.39

0.3

92

4.6

41

.12

1.1

40

.43

24

.65

25

.47

Ni6

00

.43

90

.45

30

.49

80

.48

80

.48

13

0.9

11

.36

1.4

10

.52

93

1.3

13

1.7

8

Cu

65

0.1

50

.16

90

.15

70

.16

20

.17

41

0.0

70

.46

30

.58

10

.18

10

.64

10

.58

Rb

85

0.0

05

94

0.0

06

47

0.0

07

37

0.0

07

77

0.0

07

12

0.4

60

.04

03

0.0

32

60

.00

67

80

.53

0.5

22

Sr8

80

.00

23

30

.00

27

60

.00

24

70

.00

26

30

.00

25

50

.17

30

.01

08

0.0

29

60

.00

55

90

.15

90

.14

8

Y8

90

.00

27

0.0

05

23

0.0

04

38

0.0

04

85

0.0

05

13

0.2

62

0.0

10

80

.00

90

60

.00

37

20

.24

50

.23

5

Zr9

00

.00

68

90

.00

97

20

.00

92

40

.01

05

0.0

11

0.6

39

0.0

27

90

.02

46

0.0

09

46

0.5

61

0.5

93

Nb

93

<0.0

00

00

0.0

01

40

.00

08

7<0

.00

00

00

.00

08

50

.05

50

.00

36

1<0

.00

00

0<0

.00

00

0<0

.00

00

00

.08

36

Cs1

33

0.0

01

26

0.0

01

09

0.0

01

83

0.0

01

21

0.0

02

13

0.1

01

0.0

04

89

0.0

04

17

0.0

01

39

0.0

99

0.1

13

Ba1

37

0.0

12

10

.01

03

0.0

12

60

.01

01

0.0

11

41

.11

0.0

27

30

.04

16

0.0

10

90

.67

70

.71

6

La1

39

0.0

00

47

0.0

01

16

0.0

00

88

0.0

01

24

0.0

00

98

0.0

69

80

.00

30

90

.00

38

20

.00

10

40

.06

77

0.0

64

Ce

14

00

.00

05

30

.00

13

50

.00

10

30

.00

18

80

.00

14

90

.10

9<0

.00

00

00

.00

41

0.0

00

72

0.0

59

2<0

.00

00

0

Pr1

41

0.0

00

77

0.0

00

94

0.0

00

80

.00

07

70

.00

09

30

.05

56

0.0

01

49

0.0

03

19

0.0

01

05

0.0

40

.05

46

Nd

14

30

.00

43

50

.00

75

70

.00

43

50

.00

72

60

.00

67

30

.47

70

.00

90

50

.01

58

0.0

05

88

<0.0

00

00

0.2

96

Sm1

47

0.0

02

91

0.0

03

31

0.0

03

56

0.0

02

42

0.0

04

26

0.1

59

0.0

07

4<0

.00

00

00

.00

27

70

.28

0.1

71

Eu1

51

0.0

00

45

0.0

01

45

0.0

00

95

0.0

01

30

.00

09

30

.09

22

0.0

02

29

0.0

03

65

0.0

01

49

0.0

70

80

.06

49

Gd

15

70

.00

20

70

.00

47

10

.00

50

60

.00

42

20

.00

42

90

.32

0.0

07

45

0.0

13

0.0

02

79

0.2

30

.24

4

Tb1

59

0.0

00

54

0.0

00

62

0.0

00

38

0.0

00

74

0.0

00

65

0.0

42

<0.0

00

00

0.0

01

61

<0.0

00

00

0.0

34

80

.05

21

Dy1

63

0.0

02

15

0.0

02

83

0.0

02

15

0.0

02

54

0.0

01

49

0.2

36

0.0

04

47

<0.0

00

00

0.0

02

91

0.0

97

9<0

.00

00

0

Ho

16

50

.00

05

50

.00

06

30

.00

07

80

.00

08

50

.00

11

50

.04

97

<0.0

00

00

<0.0

00

00

0.0

00

43

0.0

35

80

.04

64

Er1

67

0.0

03

18

0.0

02

56

0.0

01

59

0.0

03

75

0.0

03

11

0.2

25

0.0

08

10

.00

81

8<0

.00

00

0<0

.00

00

00

.18

8

Tm1

69

0.0

00

42

0.0

00

48

0.0

00

52

0.0

00

61

0.0

00

71

<0.0

00

00

0.0

01

07

0.0

01

53

0.0

00

57

0.0

40

70

.04

97

Yb

17

10

.00

43

7<0

.00

00

00

.00

37

90

.00

51

60

.00

37

10

.24

<0.0

00

00

0.0

11

30

.00

41

80

.24

40

.25

8

Lu1

75

0.0

00

58

0.0

00

67

0.0

00

72

0.0

00

80

.00

05

70

.04

53

0.0

01

72

<0.0

00

00

0.0

00

46

0.0

59

50

.04

88

Hf1

78

0.0

01

22

0.0

02

42

<0.0

00

00

0.0

02

04

0.0

04

15

0.0

95

<0.0

00

00

0.0

07

72

0.0

27

10

.16

70

.20

4

Ta1

81

0.0

00

59

0.0

00

47

0.0

01

02

0.0

01

20

.00

05

0.0

32

30

.00

15

0.0

01

52

<0.0

00

00

0.0

80

50

.03

48

Pb

20

80

.00

13

40

.00

24

20

.01

10

.00

25

10

.00

30

20

.10

40

.00

59

40

.00

69

30

.00

28

80

.15

0.1

12

Th2

32

0.0

00

95

<0.0

00

00

0.0

00

58

0.0

05

46

0.0

01

14

0.0

52

1<0

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00

00

.00

34

60

.00

14

40

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76

0.0

39

7

U2

38

0.0

00

80

.00

05

30

.00

08

0.0

00

95

0.0

01

24

<0.0

00

00

0.0

02

36

0.0

04

13

0.0

00

63

0.0

51

80

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71

Pm

14

7<0

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.00

Po

20

8<0

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0<0

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32

<0.0

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0<0

.00

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0

Pu

23

8<0

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0<0

.00

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0<0

.00

<0.0

0<0

.00

<0.0

0<0

.00

Page 139: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

133

SAM

PLE

MV

P1

04

37

GLI

TTER

!: M

ean

Raw

CP

S b

ackg

rou

nd

su

btr

acte

d.

Ele

me

nt

10

43

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pt1

-px-

a1

04

37

-sp

t1-p

x-b

10

43

7-s

pt1

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c1

04

37

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t1-p

x-d

10

43

7-s

pt1

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e1

04

37

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t1-p

x-f

10

43

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pt1

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a1

04

37

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t1-p

l-b

10

43

7-s

pt2

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a1

04

37

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t2-p

x-b

10

43

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pt2

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c

Li7

22

71

25

52

27

93

32

41

31

30

22

32

60

56

18

33

19

25

00

25

90

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47

34

40

80

71

42

09

16

84

23

86

66

71

39

76

52

59

65

95

78

93

82

62

42

90

43

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27

12

68

46

26

50

85

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Si2

91

04

65

10

20

99

50

29

86

39

71

99

71

54

88

05

14

89

29

18

78

99

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11

85

34

51

12

33

50

38

33

62

42

16

90

22

2

Ca4

33

17

22

13

11

25

12

94

11

22

92

12

72

96

07

84

78

88

50

62

84

32

52

83

77

34

86

34

74

9

Sc4

52

41

25

12

26

12

82

18

93

82

17

92

72

15

56

84

58

92

41

23

59

22

49

35

49

00

44

83

99

Ti4

91

75

69

01

32

21

61

29

85

81

23

55

81

11

05

11

56

60

58

91

69

71

45

11

72

23

23

21

32

6

V5

15

55

19

64

71

31

94

56

35

64

65

65

44

34

34

51

44

55

06

36

54

54

98

98

81

56

18

81

51

64

3

Cr5

21

68

67

71

60

25

01

59

01

11

57

83

41

38

36

46

14

62

26

61

95

12

59

89

49

36

44

84

75

Ni6

04

30

74

24

14

51

24

64

24

36

76

19

71

04

99

44

21

52

99

57

90

Cu

65

29

22

51

31

82

47

31

04

45

30

28

94

81

38

6

Rb

85

22

43

25

92

10

63

43

80

0

Sr8

84

56

14

42

03

44

52

58

45

62

24

34

39

34

82

66

19

82

38

05

71

64

06

23

7

Y8

94

49

84

94

64

51

44

13

51

34

22

34

54

38

15

52

29

35

14

99

16

71

44

63

91

25

56

32

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13

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01

91

72

31

84

95

41

63

67

41

75

70

11

81

94

82

62

25

41

13

14

13

86

19

57

11

94

Nb

93

21

51

69

18

91

71

18

21

40

44

04

21

0

Cs1

33

08

01

50

00

03

00

0

Ba1

37

16

01

65

01

71

70

38

02

73

85

87

19

87

84

La1

39

40

77

73

76

63

35

88

63

55

13

33

98

62

72

34

24

13

26

93

37

98

39

65

2

Ce

14

02

31

26

62

19

01

92

10

68

52

11

58

62

11

43

65

88

59

21

35

71

73

22

34

29

41

72

84

Pr1

41

65

92

76

43

00

60

81

26

24

85

61

74

41

46

71

84

70

38

63

67

51

26

10

6

Nd

14

34

72

31

48

00

64

48

36

45

76

94

56

77

93

28

46

27

93

46

55

71

42

89

Sm1

47

21

20

62

17

05

19

58

62

01

05

20

53

71

44

38

44

14

21

18

81

23

80

Eu1

51

11

51

21

21

53

10

89

41

11

99

11

47

01

09

28

74

28

53

11

55

88

89

8

Gd

15

72

44

20

25

40

42

25

72

23

45

12

38

07

30

22

25

26

22

45

02

29

22

72

Tb1

59

27

68

22

86

48

25

60

42

64

25

27

00

95

35

12

41

41

28

07

45

88

56

1

Dy1

63

42

66

94

38

05

40

13

24

05

81

42

01

41

36

21

49

17

24

27

51

14

94

13

57

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16

53

38

87

35

27

43

16

02

32

50

63

40

22

16

21

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93

34

63

51

76

11

68

0

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67

21

60

32

21

81

20

12

72

09

35

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86

71

57

93

76

62

18

96

18

04

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69

13

00

61

32

28

11

81

01

26

00

12

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41

38

61

01

91

30

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07

11

34

41

01

47

10

52

01

07

23

18

46

16

21

10

77

51

94

91

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6

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75

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82

99

56

93

03

93

56

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04

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18

62

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19

71

92

34

62

24

3

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78

73

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65

16

67

02

71

17

69

35

19

97

36

46

11

53

94

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81

10

48

78

77

29

25

00

10

90

5

Pb

20

87

64

72

45

39

75

47

72

45

70

41

70

88

83

61

19

40

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32

65

63

75

32

32

75

14

85

74

02

85

11

7

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38

41

38

13

13

61

42

48

00

28

00

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72

12

06

21

70

51

95

86

20

10

52

05

37

14

43

84

41

42

11

88

12

38

0

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20

87

64

72

45

39

75

47

72

45

70

41

70

88

83

61

19

40

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32

65

63

75

32

32

75

14

85

74

02

85

11

7

Pu

23

84

13

81

31

36

14

24

80

02

80

0

Page 140: A geochemical and U-Pb isotope study of lower crustal ...€¦ · The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor and McLennan, 1985). While

134

APPENDIX 6 – CALCULATED CONCETRATION RATIOS AND PARTITION

CO-EFFICIENTS FROM PUBLISHED DATA.

Cli

nop

yroxen

e m

ineral/

wh

ole

rock

con

cen

trati

on

rati

os

Rb

T

h

U

Ta

Nb

L

a

Ce

Sr

Nd

Z

rH

f S

m

Eu

Gd

D

y

Y

Er

Yb

L

u

Ni

Cr

MV

P10437

0.0

00.3

90.4

60.0

30.0

10.4

91.1

00.0

22.0

61.1

81.7

62.6

11.6

12.8

22.8

63.0

02.8

93.0

62.9

50.8

01.9

1

MV

P10438

0.0

00.2

80.1

70.1

20.0

00.9

02.0

30.0

33.7

13.9

04.4

54.5

02.3

94.6

34.4

24.4

04.2

24.3

83.9

41.3

92.3

4

DE

L99-2

-01

0.0

00.0

60.0

90.0

30.0

10.3

20.9

90.0

32.6

62.2

53.0

83.3

62.4

63.6

73.2

93.4

83.2

63.3

63.1

70.5

82.7

1

MV

P99-2

-12

-0.0

50.0

80.0

30.0

21.0

21.6

00.1

51.9

71.6

52.3

61.4

51.0

50.7

80.2

80.1

70.1

20.0

60.0

52.6

41.2

5

MV

P99-2

-22

-0.3

30.1

20.0

20.0

11.3

01.6

90.1

11.9

51.4

61.8

01.6

51.2

81.1

90.5

70.3

80.2

80.1

60.1

32.0

51.7

9

DE

L2-1

0434

-0.0

50.0

40.0

10.0

00.5

20.8

50.4

91.1

00.9

01.1

11.0

00.8

80.7

50.3

80.2

60.2

00.1

20.0

91.0

81.0

4

Exp

erim

en

tal

parti

tion

coeff

icie

nts

0.0

31

0.0

30.0

40.0

13

0.0

05

0.1

047

0.1

254

0.0

60.2

866

0.1

31

0.1

208

0.4

774

0.5

618

0.5

954

0.6

218

0.9

0.6

356

0.6

01

0.5

602

2.6

3.8

Arth

, (1

976)

Fu

jim

ak

i et

al.

, (1

984)

Myse

n, (1

978)

Hart

an

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135

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136

APPENDIX 7 – SHRIMP DATA

U-Pb isotope analyses of zircons from the two pyroxene granulite xenolith MVP10436. (Error for ages

quoted as 1σ). (204 Pb) corrected 206Pb/238U Ma (1σ error)

Zircon U-Pb spot analysis MVP10436

Grain

number

Spot

analysis

U (ppm) Th (ppm) 206Pb/238U Age 1s error

Zrc_1 36-01 23.266 10.11761 409.4373 10.67743

Zrc_1 36-02 320.1134 253.2767 422.4775 7.417539

Zrc_2 36-03 94.29916 65.30674 410.9466 8.042007

Zrc_3 36-04 114.6473 59.65866 414.0471 7.871262

Zrc_4 36-05 70.15758 53.64626 410.9062 8.66768

Zrc_4 36-07 70.22831 58.98187 397.615 8.14862

Zrc_5 36-06 124.3823 101.1763 385.4857 7.239134

Zrc_6 36-08 24.49363 12.0519 375.9392 11.25381

Zrc_7 36-09 40.13716 16.9941 425.8215 10.25929

Zrc_8 36-10 464.7232 407.1909 419.7649 21.80092

Zrc_8 36-11 51.71911 28.74154 430.8182 9.063939

Zrc_9 36-12 190.0077 151.261 405.5114 14.61896

Zrc_10 36-13 234.545 171.198 413.6329 7.399428

Zrc_11 36-14 307.1234 253.2527 414.6151 7.298821

Zrc_12 36-15 292.0162 214.1255 439.5797 16.72235

Zrc_13 36-16 146.7853 119.1733 433.4253 7.975261

Zrc_14 36-17 74.27484 48.48459 424.3781 8.435999

Zrc_15 36-18 63.98417 22.50337 432.5754 8.912881

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137

U-Pb isotope analyses of zircons from the two pyroxene granulite xenolith MVP10437. (Error for ages

quoted as 1σ)

Zircon U-Pb spot analysis MVP10437

Grain

number

Spot

analysis

U (ppm) Th (ppm) 206Pb/238U Age 1s

err

Zrc_1 37-01 54.4346 41.46334 386.4381 9.17449

Zrc_1 37-02 55.58839 40.73986 381.1109 8.908048

Zrc_1 37-03 31.45861 30.91883 364.0612 9.961885

Zrc_1 37-04 60.59974 47.84816 371.8599 7.831385

Zrc_1 37-15 57.45387 42.07266 382.8903 8.320198

Zrc_2 37-05 35.68257 24.49753 399.8503 9.366056

Zrc_2 37-07 27.0405 20.20708 415.2181 10.92836

Zrc_3 37-06 56.38366 40.24586 390.1589 8.414634

Zrc_4 37-08 47.22175 17.47131 408.0798 9.362504

Zrc_5 37-09 33.64235 13.59223 378.2102 10.45922

Zrc_6 37-10 69.97747 54.19293 427.5121 8.967268

Zrc_7 37-11 589.6441 498.1413 395.7399 6.827423

Zrc_8 37-12 454.065 467.3586 387.116 6.737261

Zrc_9 37-13 264.6763 239.143 351.9511 6.265138

Zrc_10 37-14 40.41176 28.1932 412.7752 9.183357

Zrc_11 37-16 422.2244 269.0493 423.2044 7.363166

Zrc_11 37-17 63.35662 44.7374 412.4974 8.969504

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138

References in Appendix

Keankeo, W., Taylor, W.R., FitzGerald, J,D., 2000. Clinoferrosilite-bearing kelyphite: a

breakdown product of xenolithic garnet, Delegate breccia pipes, New South

Wales, Australia. Mineral. Mag. 64, 469-479

Becker, H., 1997. Sm-Nd garnet ages and cooling history of high-temperature garnet

peridotite massifs and high pressure granulites from Lower Austria. Contrib.

Mineral. Petrol. 127, 224–236.

TEMORA

Grain

number

Spot

analysis

U (ppm) Th (ppm) 206Pb/238U Age 1s

err

Zrc_1 TEM2-01 138.4216 63.49054 435.2258 17.64489

Zrc_1 TEM2-02 281.4164 72.21548 421.1413 7.475124

Zrc_1 TEM2-03 218.6967 55.76253 423.4799 7.563013

Zrc_1 TEM2-04 134.796 62.22951 421.116 7.960547

Zrc_2 TEM2-05 126.683 57.84554 405.7282 8.01859

Zrc_3 TEM2-06 86.21236 24.7627 411.2918 8.045914

Zrc_4 TEM2-07 112.7308 59.25016 416.3577 7.927833

Zrc_5 TEM2-08 121.0498 59.7806 407.2281 7.711487

Zrc_5 TEM2-09 182.6942 84.52465 408.1324 7.446298

Zrc_5 TEM2-10 148.0921 74.09509 415.9314 7.818975

Zrc_5 TEM2-11 65.99863 21.6506 421.5372 8.806397

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139

APPENDIX 8 – RESEARCH PROPOSAL

Major and trace element geochemistry,

geochronology and isotopic

compositions of deep-seated xenolith

inclusions from the Monaro Volcanic

Province, NSW Australia

Research proposal and literature review

Natasha Barrett

School of Earth and Environment, University of Western Australia, Crawley

May 2014

Word Count: 4685

Supervisors:

Dr Tony Kemp

A/Prof Eric Tohver (co-supervisor)

Formatted according to Earth and Planetary Science Letters (EPSL)

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140

TABLE OF CONTENTS

8. Abstract………………………………………………………………………iii

9. Introduction……..…………………………..………………………….......1-2

10. Review of literature……………….….…………..………………………...2-9

10.1. Chemical composition of the lower continental crust………...……..2-5

10.2. Stable isotope studies……………………………………….….……5-8

10.3. U-Pb geochronology………………………………………..…...…….9

11. Geological setting……………………………………………………..…10-12

12. Summary of 2013 findings…………………………………..….…………..13

13. Aims and objectives…………………………………..……………... .…14-15

14. Significance and outcomes…………………………………………....…15-16

15. Methodology……………………………………..………….…….…..….16-18

8.1. Sample preparation………....…………………..……………....…16-17

8.2. BSE and CL imaging………….……………….…….….………..…...17

8.3. Trace element LA-ICPMS analysis….…………….…….……..……..17

8.4. SHRIMP U-Pb geochronology…………..………….……..….………17

8.5. Sulfur and carbon isotope analysis…………..……………………17-18

16. Conclusion………………………………………………….…….………..…18

17. References……………………...……………………………….……..…19-21

18. Appendices…………………...……………………………….….………22-25

18.1. Budget…………………………………….………………...….….….22

18.2. Timeline 2014…………………...……….………………...….…..….22

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141

1. Abstract

Granulite xenoliths are samples of rock formed at deep levels within the Earth. They are

rapidly transported to the surface by volcanic pipes, and potentially represent direct

samples of the lower continental crust. Applying geochronology, along with major and

trace element analysis, to granulite xenoliths from the Monaro Volcanic Province (New

South Wales, Australia) will be the focus of this project. Obtaining high quality

geochemical data from whole rocks and minerals will build on a detailed petrographic

study conducted in 2013, and reveal if samples are lower crustal in origin by association

with the Silurian aged granitoid plutonism of the region. The first phase of this study

recognised primary scapolite, a mineral that is generally rare in exposed granulite

terranes and lower crustal xenoliths, but endemic to deep-seated xenoliths found in

eastern Australia. The structural properties of scapolite make this mineral a potential

stable reservoir for carbon and sulfur in the lower crust. This project will assess the

stable isotope fractionation of sulfur and carbon, and determine if there is any

relationship between volatiles in the lower crust and geochemical cycles observed at the

Earth’s surface. These sulfur and carbon isotope signatures in conjunction with zircon

ages, P-T estimates (from quantitative geothermobarometry) and bulk geochemistry will

form a basis for distinguishing the origin of the lower crust in this region, and provide

constraints on its evolution, chemical composition, and the significance and source of

its volatile reservoir.

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1

2. Introduction

The Earth’s continental crust is characterised by its bulk andesitic composition (Taylor

and McLennan, 1985). While this is true for much of the Earth’s middle and upper

crust, this classification is favoured by the availability of upper crustal material over the

basaltic and inaccessible lower crust region (>23km depth; Rudnick and Gao, 2003).

The origin of the continental crust remains actively debated, and multiple fields of Earth

science are involved in unravelling its formation, structure and composition. It is much

older than the oceanic crust and contains most rocks in the geological record, thus

preserving an archive of Earth evolution. Exposed lower crustal material exists as

tectonically exhumed granulite facies terranes or in the form of xenoliths in volcanic

pipes (e.g. Irving, 1974; Francis, 1976).These pipes, forming explosive diatremes, bring

upper mantle and lower crustal fragments to the surface within hours to days (e.g.

Kushiro, 1976), which is ideal for preserving the prograde, high temperature mineral

assemblages of the lower crust.

This study focuses on deep-seated xenoliths, potentially representing samples of lower

crustal material, beneath the Monaro Volcanic Province, NSW Australia. Their

mineralogy denotes pressure and temperature conditions of granulite facies

metamorphism, possibly driven, at least in part, through heat advection from mantle-

derived magmas (e.g. Wells, 1980). Studying lower crustal rocks provides us with a

potential record for the addition of new material to the continents (Kemp et al., 2007) as

well as the petrological and chemical nature of the deep crust (Chen et al., 2001). The

proposed project will build on a detailed petrological study conducted in Part 1 of this

project (in 2013), where characterisation of the Monaro Volcanic Province xenoliths by

optical microscopy, scanning electron microscopy (SEM) and electron microprobe

analysis (EMPA), supported a lower crustal origin by analogy with several xenolith

samples from the previously studied Delegate breccia pipes in NSW (Chen et al., 1998;

Irving, 1974).

The aim of this study is to perform major and trace element geochemical analysis and

geochronology (zircon, U-Pb isotopes) on these xenoliths and key constituent minerals,

to determine the nature and potentially the age of the igneous protolith, or the time that

it was metamorphosed. In particular, primary scapolite identified in two rock types from

the Monaro Volcanic Province (two-pyroxene granulite and garnet-plagioclase-

clinopyroxenite) will be analysed, focusing on the nature of the crystallographic bound

volatile components, specifically carbon dioxide and sulfate. While it is expected that

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2

sulfur and carbon in this lower crustal region derives from a magmatic source (e.g.

Hoeffs et al., 1982; Iyer et al., 1992), isotopic data can confirm this hypothesis through

δ34S (‰) and δ13C (‰) variations in scapolite from these samples. (δ34S (‰) denotes the

34S/32S abundance relative to the Canyon Diablo troilite meteorite, and δ13C (‰)

represents 13C/12C relative to the Pee Dee Belemnite Cretaceous marine fossil -

discussed further in later sections). Calculated δ34S (‰) and δ13C (‰) deviations will

reveal if sulfur and carbon originated from the oceanic crust (including evaporite

deposits and marine sediments), or if the source is mantle derived. This information,

together with geochronology, whole rock geochemistry and quantitative pressure-

temperature estimates calculated from whole rock data, will provide insight into the

metamorphic history of the lower crust beneath eastern Australia. Findings will

contribute to characterising the bulk chemical composition of the continental crust, and

by obtaining information on the metamorphic history and potential origin of lower

crustal material, answer existing questions regarding the nature of the continental crust

as a whole, and the processes responsible for its formation and preservation through

time.

3. Review of literature

3.1. Chemical composition of the lower continental crust

The bulk continental crust is currently regarded to be intermediate in composition

(Taylor and McLennan, 1985), and holds the majority of the Earth’s heat producing

incompatible trace elements, e.g., 35-55% of the Rb, Ba, Pb, K, Th and U (Rudnick and

Fountain, 1995). Calculating the chemical composition of the lower crust is far more

difficult due to the inaccessibility of the Earth’s crust beyond 12kms depth

(Kremenetsky and Ovchinnikov, 1986). While granulites studied from xenoliths and

exposed granulite terranes are lithologically heterogeneous, they are mostly mafic,

approaching a basaltic composition (Rudnick and Fountain, 1995). The granulitic lower

crust is generally believed to represent a residual or cumulate composition from the

crystallisation and extraction of magmas, and thus be refractory, depleted in radioactive

heat producing incompatible elements (K, Th, U) (Figure 1), and mechanically strong

due to the dominance of pyroxene over quartz (Taylor and McLennan, 1985). Formation

of the lower crust may therefore be fundamental for the preservation, strengthening and

stabilization of continents as a whole (Rudnick, 1995). Several estimates of the

composition of the lower and bulk continental crust are presented in Table 1.

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Figure 1. (A) Rare earth element patterns of upper (Taylor and McLennan, 1985), middle and lower

continental crust. (B) Relative enrichment/depletion of elements in the middle and lower crusts compared

with upper crust from Rudnick and Fountain (1995).

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Lower continental

crust

Lower

continental crust

Continental

crust

Continental

crust

Continental

crust

Taylor and

McLennan (1985)

(wt. %)

Rudnick and

Fountain (1995)

(wt. %)

Taylor and

McLennan

(1985) (wt. %)

Rudnick and

Fountain

(1995) (wt. %)

Wedepohl

(1995) (wt. %)

SiO2 54.4 52.3 57.3 59.1 61.5

TiO2 1.0 0.8 0.9 0.7 0.68

Al2O3 16.1 16.6 15.9 15.8 15.1

FeO 10.6 8.4 9.1 6.6 6.28

MgO 6.3 7.1 5.3 4.4 3.7

CaO 8.5 9.4 7.4 6.4 5.5

Na2O 2.8 2.6 3.1 3.2 3.2

K2O 0.34 0.6 1.1 1.88 2.4

Total 100.04 97.80 100.1 98.08 98.36

Rb

(ppm)

5.3 11 32 58 78

Sr

(ppm)

230 348 260 325 333

Y

(ppm)

19 16 20 20 24

Zr

(ppm)

70 68 100 123 203

Nb

(ppm)

6 5 11 12 19

Cs

(ppm)

0.1 0.3 1.0 2.6 3

Ba

(ppm)

150 259 250 390 584

La

(ppm)

11 8 16 18 30

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Pb

(ppm)

4.0 4.2 8.0 12.6 14.8

Th

(ppm)

1.06 1.2 3.5 5.6 8.5

U

(ppm)

0.28 0.2 0.91 1.42 1.7

Table 1. Compositional estimates of the lower continental crust and bulk composition of the continental

crust from Yanagi, (2011). (Total Iron as FeO)

Geochemical data will be obtained from the Monaro Volcanic Province xenoliths in

conjunction with samples from the Delegate breccia pipes, to investigate the

heterogeneity of the lower crust beneath eastern Australia. Both suites of volcanically

derived xenoliths reside within the eastern Lachlan Fold Belt, and geochemical analysis

will therefore determine if samples represent fragments of lower crust subject to the

same, or an entirely different, metamorphic history.

The two major rock types from the Delegate pipes, a two-pyroxene granulite and garnet-

plagioclase-clinopyroxenite have a significantly different major and trace element

distribution to other granulites from these xenolith suites (Irving, 1974). Additionally,

some of the previously studied Delegate xenoliths have higher Al and Ca but lower Na

and K contents than typical basalts. These xenoliths have been understood to represent

early cumulates from basaltic magmas, or residues of partial melting, where the amount

of alkalis and SiO2 was reduced by the removal of a more felsic composition melt phase

(White and Chappell, 1989).

Analysing the Delegate samples, in addition to those from the Monaro Volcanic

Province, will ensure the collected data is consistent for comparison with previous

chemical signatures, and produce reliable results for investigation regarding the

composition of the lower crust under eastern Australia. Major and trace element

analysis from both whole rock and minerals (the later by laser ablation ICPMS) will

potentially tell us the nature of the source rock in the deep crust or upper mantle, and

processes by which it was formed or modified.

3.2. Stable isotope studies

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While it is understood that sulfur and carbon in the oceanic crust and sediments are

introduced into the mantle at subduction zones, much is still unknown about the fate of

this material in the Earth’s interior (Figure 2). An important feature of the Monaro

Volcanic Province xenoliths is the presence of primary scapolite in several of these

samples. The physical properties of scapolite and its ability to sequester SO4 and CO2 in

its structure make it possible to investigate the nature and source of these volatiles in the

lower crust.

The sulfur cycle has been studied over several decades (e.g. Canfield, 2004; Seal, 2006),

although little has been published on its isotopic effects during subduction and high-

pressure metamorphism in the lower crust. Most models on the global sulfur budget are

developed without knowledge of these processes, and leave much to be answered

regarding the nature of geochemical cycles at both lower crustal and mantle depths

(Figure 3). An important question that needs to be addressed is whether sulfur and

carbon in the lower crust originated from the Earth’s surface, and was recycled through

subduction or other crust-mantle exchange processes (e.g. density foundering), or if this

reservoir of sulfur and carbon is derived from the mantle via the emplacement of

primitive magmas.

There are 4 stable isotopes of sulfur 32S,33S, 34S, and 36S. Figure 4 shows a graph of

natural sulfur isotope reservoirs with a summary of isotopic compositions of some

major rock types. The 34S/32S ratio of sample material is conventionally expressed

relative to the S isotope composition of troilite from the from the Canyon Diablo troilite

meteorite, and given by the notation δ34S. This is calculated as follows:

δ34 S [‰] =

(

(S34

S32⁄ )

Sample

(S34

S32⁄ )

CDT

− 1

)

x 1000

With respect to δ34S, there are 3 distinct reservoirs, these are (1) sulfur derived from the

mantle, δ34S ranging 0 ± 3 ‰ (Chaussidon and Lorand, 1990), (2) sulfur derived from

sea water, δ34S ranging from +18.5 to 21.0 ‰ for modern sea water and (3) sedimentary

sulfur showing strong negative to positive δ34S values ranging from -56 to +20 ‰, in

part reflecting fractionation associated with biological activity (see Figure 4). This

proposed study will aim to investigate the isotope composition of sulfur in scapolite

occurring naturally in high pressure rock samples. This will be done by comparing

δ34S‰ values in scapolite with those of natural sulfur reservoirs, and thus determining

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the potential source for stable sulfur in the lower crust, and to test whether this can only

be explained by an internal magmatic source (e.g. Hoefs et al., 1982; Iyer et al., 1992).

It is also possible that, like sulphur addition, regions of the mantle have been carbonated

by earlier subduction of supracrustal carbonate-rich sediments, and have entered into the

lower crust via CO2 fluxes which caused granulite metamorphism (Harley, 1989).

Carbon has 2 stable isotopes, 13C and 12C, where δ13C‰ represents the ratio of 13C/12C

relative to the Pee Dee Belemnite, a Cretaceous marine fossil used as the reference

standard. This value is given by:

δ13 C [‰] =

(

(C13

C12⁄ )

Sample

(C13

C12⁄ )

PDB

− 1

)

x 1000

δ13C‰ will be analysed to determine if deviations from the standard are consistent with

the crystallization of scapolite from a mafic melt emplaced at the lower crust such as

xenoliths studied in Moecher et al., (1994) producing δ13C ‰ values of -8.2 to -1.2 in

scapolite.

Figure 2. Vertical cross section sketch through the crust and upper mantle showing the sulfur cycle in the

plate tectonic context by Shimizu and Marschall, (2012). Input materials delivered to subduction zones

are shown in blue, and output materials shown in orange. Diagram shows a significant gap in our

knowledge on the sulfur cycle, as no data exists on the processes effecting the sulfur budget and

isotopic composition of materials within subduction zones (outlined in red).

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The lower crust represents an unconstrained ‘black box’ on the sulfur and carbon

budgets. While it signifies a potential sink for sulfur and carbon, its remains poorly

understood due to the extensive area it covers. The exact amount of these elements in

the lower crust, how they are hosted in rocks, and their origin still remain largely

enigmatic.

Figure 3. Schematic diagram showing the cycle of sulfur/sulfur isotopes between surface reservoirs.

Ocean sulfate (blue), sulfides (yellow) and sulfates (orange) in crustal rocks and the mantle (green) (data

from Canfield, 2004). The isotopic composition of crustal and surface reservoirs are well characterised

whereas subduction-zone input into the mantle and lower crust remain in question (Shimizu and

Marschall, 2012).

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Figure 4. Natural sulphur isotope reservoirs. Data from Sakai et al., (1982; 1984), Ueda and Sakai,

(1984), Claypool et al., (1980), Kerridge et al., (1983), Chambers, (1982), Coleman, (1977) and

Chaussidon et al., (1989).

3.3. U-Pb geochronology

While geochemistry and thermobarometry provide potential pressure and temperature

conditions for formation, it is not possible to classify samples as fragments of lower

crust without information on their age, distinguishing samples from the host rock, and

thus ruling out the possibility of a magmatic cumulate subject to granulite conditions.

Isotope studies have been done on metamorphic zircons in the two-pyroxene granulite

xenoliths from the Delegate breccia pipes using a thermal ionisation mass spectrometer,

producing U-Pb ages of 398±2 Ma and 391±2 Ma (Chen et al., 1998). Zircon ages have

also been reported from xenoliths hosted by alkali basalts in the McBride Province,

north Queensland giving U-Pb ages of ̴ 320-220 Ma by ion microprobe analysis

(Rudnick and Williams, 1987). Both localities have been interpreted to date granulite

facies metamorphism in the lower crust.

U-Pb geochronology on the Delegate pipe xenoliths by Chen et al., (1998) was

conducted using the VG354 thermal ionisation mass spectrometer (TIMS) at the Royal

Ontario Museum’s Geochronology Laboratory, Canada, while zircon ages from the

McBride Province in north Queensland were analysed using the sensitive high

resolution ion microprobe (SHRIMP) at the Australian National University Research

School of Earth Science. The McBride Province study suggested that the use of the ion

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microprobe would allow analysis of multiple growth phases within small (approx.

<60µm) zircons, critical to date episodic events of crustal growth (Rudnick, 1992;

Hancher and Rudnick, 1995). Additionally, retaining the analysed zircons from

SHRIMP dating will allow further analysis of trace elements and oxygen isotope

compositions on the same zircon grains. For these reasons, in-situ analysis of zircon by

ion microprobe will be the preferred method for instrumental analysis in this project.

Samples in this study contain mineral assemblages showing both equilibrium and

disequilibrium textures, as established during the first phase of this study completed in

2013. While disequilibrium textures can help decipher a P-T path, it is difficult to apply

quantitative thermobarometry and geochronology to these samples. Nonetheless,

analysing the petrography of the disequilibrium samples along with geochronology

from the other samples within the Monaro Volcanic Province, may provide a unique

insight into the lower crust and a polymetamorphic history.

4. Geological setting

Xenolith samples were collected from two localities in southeastern New South Wales

by Professor Richard Arculus at the Australian National University in 2000, and made

available for this study. Five samples were from the two diatremes known as the

Delegate breccia pipes outcropping at Airlie Park homestead, 35kms northwest of

Delegate, NSW (Lovering and White, 1969) (Figure 5). These pipes are Mid-Jurassic in

age, ̴ 168 Ma based on K-Ar dating methods (Lovering and Richards, 1964). Twelve

xenolith samples were from alkali basalt pipes, Eocene-Oligocene in age (56-34 Ma;

Taylor et al., 1990) located north of the Delegate around the town of Nimmitabel, NSW

within the Monaro Volcanic Province (Figure 6). This Monaro Volcanic Province hosts

approximately 65 eruption sites within its basaltic lava field (Roach et al., 1994). The

region has experienced extensive mafic volcanism which began during the late

Palaeocene and lasted for about 20 million years, where at least 630 cubic kilometres of

pyroclasts and lava erupted (Brown et al., 1993). The province is believed to be built up

by eruptions of alkali basalt, basanite and nephelinite (Roach et al., 1994). The surface

geology is dominated by mafic lavas and Tertiary volcanic sediments which overly

Ordovician-Devonian bedrock (Figure 6). Although much of the volcanic material has

been eroded away, several landmarks still exist showing evidence of a formerly active

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volcanic province including the Brothers volcanic plugs and several flat topped hills

which represent stacks of lava flows (Brown et al., 1993).

Both localities occur within the Ordovician-Devonian Lachlan Fold Belt of eastern

Australia, but are related to a much younger hot-spot magmatism (Johnson et al., 1999).

The Lachlan Fold Belt is itself part of the Terra Australis Orogen, a vast subduction-

related accretionary orogenic system that developed along the eastern paleo-pacific

margin of Gondwanaland during the Palaeozoic and Mesozoic (Cawood and Buchan

2007; Braun and Pauselli, 2004). This tectonic unit comprises the eastern third of the

Australian continent (Gray and Foster, 2004), as well as comprising a large part of

western Antarctica and Argentina.

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Figure 5. Map showing the location and regional setting of the Delegate pipes, in southern NSW,

Australia (Lovering and White, 1969).

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Figure 6. Outline of the Monaro Volcanic Province. Samples were collected around the town of

Nimmitabel. The shaded region represents mafic lavas and Tertiary sediments, while the surrounding area

represents the Ordovician-Devonian Bedrock. Lava pile outline is from Lewis et al., (1994) modified by

Roach, (2004).

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5. Summary of 2013 findings

This investigation will aim to build on the research project undertaken in 2013 which

focused on characterising the petrography and mineral chemistry of unclassified

xenoliths from the Monaro Volcanic Province. The 2013 study identified 3 rock types, a

two pyroxene granulite, garnet-plagioclase-clinopyroxenite and a reaction intermediate

showing disequilibrium textures between plagioclase, clinopyroxene, orthopyroxene,

garnet, spinel and ilmenite. The two pyroxene granulite and garnet-plagioclase-

clinopyroxenite samples showed the widespread occurrence of scapolite co-existing in

textural equilibrium with granulite minerals. Pressure and temperature ranges for these

samples were constrained from electron microprobe data, and are consistent with

derivation from a thermally perturbed and thickened lower continental crust. Textures

identified in the third sample indicate a dynamic and complex history in the lower crust,

and could potentially provide evidence for larger scale processes of crustal thickening

and extension, as typifies convergent plate margins. Findings from optical microscopy,

secondary electron microscopy and electron microprobe analysis performed in the initial

stages of this project, have provided a basis for more quantitative microanalysis

focusing on whole rock geochemistry, trace element analysis and geochronology, to

further investigate the history of the lower crust and characterise its composition.

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6. Aims and objectives

The aim of this study is to make progress towards classifying the origin, and eventually,

resolving the genesis of granulite xenoliths from the Delegate and Monaro Volcanic

Province localities. The specific objectives of this project are:

1. Obtaining accurate and precise whole rock, major and trace element data for

each classified rock type, and to interpret this data by constructing REE and

multi-element spider diagrams.

2. To analyse the trace element content in each mineral, including major peak

metamorphic minerals, to further constrain P-T estimates (such as the Zr

exchange between co-existing rutile and zircon) and understand the growth

history and equilibrium/chemical exchange amongst phases.

3. Determine ages of granulite facies metamorphism, and potentially the igneous

protolith, through U-Pb geochronology of zircon.

4. And investigate the stable isotopes of sulfur and carbon in scapolite, and

determine the origin of these elements in the lower crust.

It is proposed that U-Pb geochronology of zircon will date the age of granulite facies

metamorphism, by analogy with similar zircon ages obtained from xenolith from the

Delegate Breccia pipes (Chen et al., 1998). This could suggest whether granulite

metamorphism in both samples is driven by heat related to production of voluminous

felsic magmatism and batholith emplacement in this part of the Lachlan Fold Belt (~420

to 380 Ma; e.g. Gray and Foster, 2004). Previous studies across several continents have

assumed that xenoliths contained by similar volcanic rocks represent fragments of lower

crust (e.g. Francis, 1976; Selverstone and Stern, 1983; Kempton and Harmon, 1992;

Kay and Kay, 1983; Leyreloup et al., 1982). The exact origin of samples in this project

has, however, yet to be determined. Before interpreting data from the xenoliths in terms

of lower crustal processes, we first need to consider if the study samples did in fact

originate from the lower crust, which can be established from dating the xenolith

samples relative to the younger Eocene-Oligocene aged host rock (Roach, 2004).

Whole rock geochemistry will also be used to constrain pressure and temperature

estimates by applying this data to the thermodynamic database THERMOCALC

(Powell and Holland, 1988). Geochronology and whole rock geochemical data will be

analysed in conjunction with mineralogy and textural features to assess changes in P-T

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16

conditions through time, as well as making interpretations regarding the chemical

composition of the lower crust relative to the upper crust.

Stable isotope studies of sulfur and carbon (as SO4 and CO2) in scapolite will give

isotopic signatures that will determine if carbon and sulfur in the deep earth originated

from a magmatic source in the deep mantle or a potential upper crustal reservoir. If

isotopic data reveal signatures exclusively generated through atmospheric

photochemical reactions and oceanic sediments, results could confirm the cycling of

sulfur and/or carbon between the major geochemical reservoirs and extend from the

oceans and atmosphere to the lower crust via subduction, and ultimately return these

elements to the Earth’s surface through volcanic pipes. Such results in combination with

geochronology, would additionally reveal that this material must have originated at the

surface prior to the age of metamorphism determined by U-Pb zircon dating, and help

constrain the tectonic setting.

7. Significance and outcomes

The bulk andesitic nature of the Earth’s continental crust is a unique feature in our solar

system (Taylor and McLennan, 1985). Characterising the composition of the lower crust

and the crust as a whole is the first stage in unravelling its nature and development, and

plays an important role in understanding the evolution of our planet. Direct, pristine

samples of lower crustal rock are currently only available in the form of xenoliths

brought to the surface by ascending mantle-derived magmas. Exposed granulite terranes

are generally considered to be less representative of the lower crust, and processes

responsible for their exhumation typically result in samples where little of the prograde

mineral assemblage has been preserved.

There are several unanswered questions relating to the composition, formation and

association of the lower crust with the more felsic upper crust. Linking geochronology

with petrology and geochemistry will help resolve this knowledge gap and make way

for future research. Investigating lower crustal xenoliths from the Lachlan Fold Belt

and wider Terra Australis Orogen, will provide information about magmatic processes

along this margin, as well as the general evolution of the continental crust. This is

important, as magmatic processes during the evolution of this orogenic system formed

the eastern third of the Australian continent, representing an efficient mechanism for

generation and preservation of continental material on Earth.

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Geochemical cycles, particularly the CO2 budget, are critical for maintaining a habitable

Earth climate through geological time (e.g. Dasgupta and Hirschmann, 2010). The

examination of sulfur and carbon isotopes in scapolite will characterise the source of

volatiles in the lower crust, as well as provide potential evidence for deep crustal

recycling through subduction. This speaks to the mass balance of recycling processes

during subduction, i.e. how much subducted material is returned to the continents via

subduction, and how much of this material disappears into the deep mantle.

8. Methodology

8.1. Sample preparation

Contamination on rock samples (i.e. saw marks, ink or alteration from weathering)

could potentially effect the geochemical results. To avoid this, samples are trimmed,

polished, washed in deionise water and placed in an ultrasonic cleaner bath to remove

excess artefacts. Each sample will then be reduced to rock chips using a hydraulic

tungsten-carbide rock crusher. Only the freshest material will be used for geochemical

analysis. Samples for mineral separation are pulverised using a disk mill adjusted to

500µm grainsize output, and those for geochemical analysis reduced to a powder using

an agate (silica based) mill to avoid tungsten carbide contamination, which can

compromise trace elements such as Ta. Both crushing and milling of samples will be

undertaken in the crushing rooms at the University of Western Australia.

Mineral separation will involve several steps. Initially, the heavy fraction will be pre-

concentrated by hydrodynamic methods (Wilfley Table and/or panning). The magnetic

minerals will be removed from this with a Frantz isodynamic magnetic separator.

Zircon and other accessory minerals are then isolated from the non-magnetic fraction

using a LST heavy liquid (density ~2.9g/cm3). Samples are run through the magnetic

separator a second time to allow the highest quality, crack free zircons to be hand-

picked and mounted into an epoxy resin for in situ microprobe analysis. This work will

be conducted in UWA’s mineral separation laboratory.

The powder for bulk chemical analysis will be sent to the GeoAnalytical Laboratory at

Washington State University, where each powder is fused with a Lithium Tetraborate

flux and made into homogenous glass disks for major and trace element signatures

using X-Ray fluorescence (XRF, for major and some trace elements), and inductively

coupled mass spectrometry (ICPMS, for most trace elements, involves acid digestion of

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the disc followed by dilution and analysis in solution mode). Volatile components will

be determined by loss on ignition, heating the sample overnight at 1100°C in a furnace.

Several reference rock powders will be analysed as unknowns concurrently with the

samples to assess the accuracy of the results.

8.2. BSE and CL imaging

Zircon grains will be characterised using Scanning Electron Microscopy, applying both

backscattered electron (BSE) and cathodeluminescence (CL) imaging. Both techniques

will show any growth zoning or internal structures in zircon, which is important to

establish before performing SHRIMP analysis. This will be undertaken at UWA’s

Centre for Microscopy, Characterisation and Analysis.

8.3. Trace element LA-ICPMS analysis

In situ trace element analysis of major minerals (e.g., garnet, plagioclase, pyroxene) will

be conducted on 6 polished thin sections using LA-ICPMS in the Advanced Analytical

Centre at James Cook University Townsville, Queensland. Spot analysis will be done

on minerals where previous EMP major element data has been collected to calibrate

areas for trace element analysis (Reed, 2005). Whole rock analysis will also provide

major, trace element and rare earth element geochemical data. This information will be

applied to the thermodynamic database program THERMOCALC for quantitative P-T

values.

8.4. SHRIMP U-Pb geochronology

U-Pb Geochronology in zircon will be undertaken at the John de Laeter Centre for

isotope research at Curtin University, using the Sensitive High Resolution Ion

Microprobe (SHRIMP). This high spatial resolution method will be used for reasons

outlined above. Well established analytical protocols will be followed for this analysis

(Williams, 1998). 8.5. Sulfur and carbon isotope analysis

In order to distinguish deep-seated sulfur from sulfur occurring in secondary minerals

(mainly fines sulphides located in altered areas in the rock), scapolite grains are

individually picked for analysis following magnetic separation of mafic minerals.

Contamination, particularly calcite could affect the δ13Cscap results. Any impurities will

be assessed using optical microscopy, BSE, CL and EMP imaging where possible. CO2

can be extracted from scapolite without fractionating the carbon isotopes by reaction

with phosphoric acid (H3PO4) at 25°C (e.g. Moecher, 1994). Acid extraction of

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scapolite will yield both CO2 and SO4. The gas from the reaction between scapolite and

H3PO4 and CO2 and SO4 separated by distillation in an n-pentane slush. Isotopic

analysis of CO2 and SO4 will be done at GNS Science, National Isotope Centre, New

Zealand.

9. Conclusion

The main objective of this project will be to obtain high quality geochemical and

geochronological data on deep-seated xenolith samples from the Monaro Volcanic

Province, NSW Australia, and to link this chemical record with petrology and textures.

Such information from lower crustal samples is important for understanding the

dynamics of the Earth’s lithosphere in terms of its metamorphism and orogenesis. The

volatile nature of the lower crust remains a critical knowledge gap, and analysing the

existence of sulfur and carbon in scapolite will characterise their isotopic signatures in

the lower crust and potentially the origin of lower crustal material in this region.

Findings from this project will contribute to further research on these samples including

the application of other isotopic systems (e.g. Lu-Hf, Sm-Nd of garnet, pyroxene) and

dating of other accessory phases to derive additional chronological constraints. In

general, as more similarly derived xenolith suites are characterised around the world we

can more accurately determine the bulk composition of the lower crust and the

continental crust as a whole.

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11. Appendices

11.1. Budget

Task and details Anticipated expenditure

CMCA facilities (Zeiss 1555 VP-FESEM, TESCAN

VEGA3 and JEOL 8530F microprobe)

$500.00

AAC facilities (Townsville) (LA-ICPMS and EMPA)

$1000.00

John de Laeter Centre (SHRIMP analysis) $1400.00

Flights/accommodation/transport $1900.00

T

Whole rock major and trace element analysis $2200.00

Sulfur and carbon isotope analysis $1000.00

Crushing and milling facilities $300.00

Postage costs

$100.00

Sandvik sample vials and self-seal plastic bags

$20.00

Printing/Copying $100.00

Total expected costs $8520.00

11.2. Timeline 2014 F M A M J J A S O

Sample preparation for geochemical analysis (by 31st

March)

X X

Sample preparation (mineral separation) X X

Proposal seminar presentation (12th May) X

SEM imaging of zircon X

Trace element analysis LA-ICPMS (by June 30th) X

SHRIMP geochronology/ additional isotope work (by

July 15th)

X

Compilation of results: tables, figures etc. X X

Thesis- draft (by 1st September) X X X

Advanced ore deposits unit (September 1st – 17th) X

Thesis- final (Due 22nd October) X X

Final project seminar (28th October) X