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Geological Survey of Western Australia

RECORD 2019/8

METAMORPHIC AND ISOTOPIC CHARACTERISATION OF PROTEROZOIC BELTS AT THE MARGINS OF THE NORTH AND WEST AUSTRALIAN CRATONS

Government of Western AustraliaDepartment of Mines, Industry Regulationand Safety

byJ AndersonDepartment of Earth Sciences, The University of Adelaide

RECORD 2019/8

METAMORPHIC AND ISOTOPIC CHARACTERISATION OF PROTEROZOIC BELTS AT THE MARGINS OF THE NORTH AND WEST AUSTRALIAN CRATONS

byJ Anderson Department of Earth Sciences, The University of Adelaide

PERTH 2019

Government of Western AustraliaDepartment of Mines, Industry Regulation and Safety

MINISTER FOR MINES AND PETROLEUMHon Bill Johnston MLA

DIRECTOR GENERAL, DEPARTMENT OF MINES, INDUSTRY REGULATION AND SAFETYDavid Smith

EXECUTIVE DIRECTOR, GEOLOGICAL SURVEY AND RESOURCE STRATEGYJeff Haworth

REFERENCEThe recommended reference for this publication is:Anderson, J 2019, Metamorphic and isotopic characterisation of Proterozoic belts at the margins of the North and West Australian

Cratons: Geological Survey of Western Australia, Record 2019/8, 43p.

ISBN 978-1-74168-855-9 ISSN 2204-4345

Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zone 50. All locations are quoted to at least the nearest 100 m.

Disclaimer This product was produced using information from various sources. The Department of Mines, Industry Regulation and Safety (DMIRS) and the State cannot guarantee the accuracy, currency or completeness of the information. Neither the department nor the State of Western Australia nor any employee or agent of the department shall be responsible or liable for any loss, damage or injury arising from the use of or reliance on any information, data or advice (including incomplete, out of date, incorrect, inaccurate or misleading information, data or advice) expressed or implied in, or coming from, this publication or incorporated into it by reference, by any person whosoever.

About this publicationThis Record is a chapter from a PhD thesis of The University of Adelaide. The chapter was researched, written and compiled as part of an informal agreement between the Geological Survey of Western Australia (GSWA) and The University of Adelaide. Although GSWA provided access to the samples necessary for this chapter’s research, the scientific content of the Record, and the drafting of figures, was the responsibility of the author. No editing has been undertaken by GSWA.

Published 2019 by the Geological Survey of Western AustraliaThis Record is published in digital format (PDF) and is available online at <www.dmp.wa.gov.au/GSWApublications>.

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JADE ANDERSON

Department of Earth SciencesUniversity of Adelaide

requirements for the degree of Doctor of Philosophy

November 2015

Metamorphic and isotopic characterisation of Proterozoic belts at the margins of the North and West

Australian Cratons

101

Mesoproterozoic metamorphism in the Rudall Province: revising the timeline of the Yapungku Orogeny and implications for cratonic Australia

assembly

ABSTRACTLA−ICP−MS U−Pb zircon and monazite geochronology from metasedimentary rocks from the Connaughton and Talbot Terranes in the western Rudall Province, North Australia provides evidence for two metamorphic events at c. 1665 Ma and between c. 1380−1275 Ma. P−T (pressure−temperature) pseudosection modelling of a staurolite–biotite bearing assemblage from the Talbot Terrane suggests peak P−T conditions of ~5.5−8.5 kbar, ~600−650 °C were at-tained at c. 1285 Ma. P−T modelling on garnet−clinopyroxene-bearing mafic amphibolite from the Rudall Province shows that peak metamorphic conditions of ~8–11 kbar, and minimum ~620–650 °C were attained at c. 1380 Ma and followed a clockwise retrograde evolution. The geochronology and P−T modelling suggest that the age of regional metamorphism (M2, Ya-pungku Orogeny) is Mesoproterozoic rather than c. 1800−1765 Ma. If regional metamorphism in the Rudall Province does reflect the collision of the North and West Australian Cratons, it occurred during the Mesoproterozoic and not the Paleoproterozoic as has previously long been assumed. Metamorphic age data and physical conditions of metamorphism from the Rudall Province may reflect a stage-wise tectonic evolution, involving the accretion of ribbons, and outboard migration of subduction and the back-arc over time, producing both medium-P, and high-thermal gradient conditions. In this proposed scenario, the system was closed during the final amalgamation of the North Australian Craton to the accreted ribbons (West Australian Craton) during the Mesoproterozoic.

1. Introduction

The Rudall Province occurs at the north-eastern margin of the West Australian Craton (WAC) and has long been recognised as occupying a critical location for understanding the Australian continent assembly (e.g. Clarke, 1991; Smithies and Bagas, 1997; Bagas, 2004; Betts et al., 2006; Cawood and Korsch, 2008; Payne et al., 2009). The Rudall Province is one of the few localities in Australia where Proterozoic-aged medium to high pressure metamorphic assemblages are preserved (minimum apparent thermal gradients of ~60–80 °C.kbar-1). Evidence for regional, moderate-thermal gradient conditions (corresponding to eclogite-high pressure granulite thermal gradients of Brown, 2007), combined with evidence for thrust stacking and magmatism has led to the proposal that the Rudall Province records crustal thickening associated with the collision of the WAC and North Australian Craton (NAC) at c. 1830−1765 Ma (e.g. Bagas, 2004; Cawood and Korsch, 2008).

Despite its apparent importance in

the assembly of Proterozoic Australia, the Rudall Province is an understudied region, and as a consequence, the tectonic evolution of the Rudall Province and its implications for the assembly of Proterozoic Australia is still notional rather than demonstrated (e.g. Maidment, 2007, 2014). The Rudall Province is considered to have a protracted tectonic history spanning at least c. 1300 M. y. from the Paleoproterozoic to the late Neoproterozoic–Cambrian (e.g. Bagas et al., 2000; Bagas, 2004; Kirkland et al., 2013). U–Pb zircon geochronology from voluminous felsic magmatic rocks of the Kalkan Supersuite comprises the largest dataset for constraining the absolute timing of tectonism in the Rudall Province (Nelson, 1995, 1996; Kirkland et al., 2013). However, the Kalkan Supersuite, and consequently the majority of the geochronological dataset, is restricted to the time interval c. 1800–1765 Ma, which comprises only the oldest part of the history (Nelson, 1995, 1996; Kirkland et al., 2013). At present, absolute time-related interpretations for metasedimentary rocks of the Rudall Province are largely based on extrapolation of

102

Chapter 4 Mesoproterozoic metamorphism in the Rudall Province

magmatic rock geochronology to fit structural and metamorphic constraints. Metasediments comprise approximately 10−60 % of the terranes within the outcropping Rudall Province (Bagas et al., 2000) and therefore present an effectively untapped opportunity to understand the fuller tectonic—including metamorphic and temporal—history.

In this contribution we present an integrated metamorphic and U−Pb monazite and zircon geochronology study on metamorphic rocks of the Talbot and Connaughton Terranes of the Rudall Province. The aim of this study is to more completely understand the metamorphic evolution of the Yapungku Orogeny (M2) and its implications for the timing of assembly of the WAC and NAC.

2. Geological Background

The Paleo- to Mesoproterozoic Rudall Province is located within the approximately 2000 km long, north-west trending, late Neoproterozoic to Cambrian-aged Paterson

Orogen, which is exposed along the eastern margin of the Pilbara Craton in north-western Australia. The Paterson Orogen continues into the Musgrave Province in central Australia (Fig. 1) where it is known as the Petermann Orogen (e.g. Bagas and Smithies, 1998; Camacho and McDougall, 2000; Wade et al., 2005; Raimondo et al., 2009, 2010; Walsh et al., 2013).

The Rudall Province contains P a l e o p r o t e r o z o i c – M e s o p r o t e r o z o i c metaigneous rocks and metasedimentary rocks with Paleoproterozoic protolith depositional ages (Nelson, 1995, 1996; Smithies and Bagas, 1997; Bagas and Smithies, 1998; Bagas, 2004; Kirkland et al., 2013). The Rudall Province has experienced a number of phases of tectonism, which have been assigned to the following events: a) the Yapungku Orogeny (D1−D2) spanning c. 1800−1765 Ma and corresponding to the emplacement of voluminous felsic magmatic rocks of the Kalkan Supersuite; b) the Miles Orogeny (D3−D4) at c. 650 Ma; c) the Blake Movement (D5), a poorly constrained Neoproterozoic

AruntaProvince

Ngalia Basin

Archean-Mesoproterozoicblock/sedimentary basin

West Australian Craton

South Australian Craton

Craton

Tasm

an L

ine

Paleo-Mesoproterozoic Orogen

West Australian Craton

ARRP

AFO

North Australian Craton

Inferred Craton Margin

500 km

GI

GC CP

MI

COGO

MP

CI

Figure 1

PCHCO(YO?)

PO

PilbaraCraton

Fig. 1. Simplified map of Australia showing Archean-Mesoproterozoic geological components. AFO = Albany Fraser Orogen, AR = Arunta Region, CI = Coen Inlier, CO = Capricorn Orogen, CP = Curnamona Province, GC = Gawler Craton, GO = Gascoyne Orogen, HCO = Halls Creek Orogen, MI = Mount Isa Inlier, MP = Musgrave Province, PC = Pine Creek Orogen, PO = Paterson Orogen, RP = Rudall Province, YO = Yampi Orogen. Modified after Cawood and Korsch (2008) and Walsh et al. (2013).

103


deformation; and d) the Paterson Orogeny (D6; c. ≥550 Ma; Smithies and Bagas, 1997; Bagas and Smithies, 1998; Bagas et al., 2000; Bagas, 2004; Czarnota et al., 2009; Kirkland et al., 2013). Earlier work ascribed D2 and M2 to a c. 1300 Ma event based on Rb–Sr ages obtained from felsic magmatic rocks (Chin and de Laeter, 1981; Clarke, 1991). This timeline is broadly contemporaneous with the crystallisation of interpreted post- D2 intrusive rocks and minor evidence for metamorphic zircon growth between c. 1310 and 1220 Ma (Nelson, 1995, 1996; Bagas, 2004; Kirkland et al., 2013). However, subsequent studies have favoured a Paleoproterozoic c. 1800−1760 Ma age for D2 and M2 based on zircon U−Pb data for magmatic crystallisation ages from the Kalkan Supersuite that were interpreted to be syn-deformational with regional medium to high-P metamorphism (Nelson, 1995, 1996; Smithies and Bagas, 1997; Bagas, 2004). This event has been interpreted to record the amalgamation of the NAC with the WAC (e.g. Li, 2000; Bagas, 2004) and has been adopted by virtually all recent paleo-tectonic reconstructions of Proterozoic Australia (e.g. Betts et al., 2002; Betts and Giles, 2006; Cawood and Korsch, 2008; Payne et al., 2009; Huston et al., 2012; Johnson, 2013). As a result, the regional significance of c. 1300 Ma ages has diminished somewhat.

Unconformably overlying the Rudall Province are deformed but poorly age-constrained late Mesoproterozoic to early Neoproterozoic sedimentary rocks of the Yeneena Supergroup, which are overlain by Phanerozoic cover sequences (Bagas and Smithies, 1998; Williams and Bagas, 1999; Bagas, 2004). Rocks of the Rudall Province have variably undergone retrogression to greenschist facies (Bagas and Smithies, 1998), which may be related to the Miles (D4) and/or c. 550 Ma Paterson (D6) orogenies.

Three terranes have been distinguished in the Rudall Province. To the southwest, the Talbot and Connaughton Terranes record similar poly-deformation histories but are distinguished on lithological differences, with the exception of the voluminous orthogneisses that occur in both terranes (Fig. 2). The Talbot and Connaughton Terranes are separated

by an east-dipping thrust, interpreted to have formed during or before the Yapungku Orogeny and are commonly interpreted to have undergone similar tectonic histories thereafter (D1 or D2; Smithies and Bagas, 1997; Bagas, 2004). A kyanite−sillimanite isograd in the Connaughton and Talbot Terranes is interpreted to have formed during M2 (Smithies and Bagas, 1997). To the north-east, the poorly outcropping Tabletop Terrane contains early Mesoproterozoic granitoids and is separated from the Talbot and Connaughton Terranes by the Camel–Tabletop Fault Zone (Smithies and Bagas, 1997). The relationship between the Tabletop Terrane and the Talbot and Connaughton Terranes is uncertain. The geology of the Connaughton, Talbot and Tabletop Terranes are described below, and existing constraints on the tectonic evolution of the Rudall Province are summarised in Table 1.

2.1 Talbot Terrane

The Talbot Terrane is composed of sedimentary derived and granitoid rocks that have been multiply deformed and metamorphosed to amphibolite facies (Smithies and Bagas, 1997; Bagas and Smithies, 1998; Bagas, 2004). Clarke (1991) divided the metasedimentary rocks of the Talbot Terrane into: 1) an older Yandagooge Formation, which appears to record a poorly preserved, high-thermal gradient M1–D1 event; and 2) the younger Tjingkulatjatjarra Formation, inferred to post-date D1–M1 and the majority of the emplacement of orthogneisses. Both formations and many of the orthogneisses of the Kalkan Supersuite are considered to record the M2–D2 Yapungku Orogeny, associated with crustal thickening (Watarra Orogeny of Clarke, 1991). There are no direct age data on the timing of D1–M1; however, two orthogneiss samples reported to contain S1 and S2 fabrics yield zircon U–Pb magmatic crystallisation ages of c. 2015 Ma (Sample 104932; Nelson, 1995; Hickman and Bagas, 1998) and c. 1801 Ma (Sample 112310; Nelson, 1995; Kirkland et al., 2013). A major phase of felsic magmatism occurred at c. 1800–1765 Ma, based on U–Pb zircon age data from orthogneisses assigned to the Kalkan Supersuite. These granitoids are

104


interpreted to be coeval with M2–D2 and have been variably deformed during D2 (cf. Nelson, 1995; Bagas, 2004; Kirkland et al., 2013). The younger age limit on the timing of D2–M2 is interpreted to be c. 1765 Ma, based on U–Pb zircon age data from an aplite dyke considered to cross-cut the S2 foliation (Nelson, 1995; Bagas, 2004). Evidence for a major phase of Mesoproterozoic tectonism in the Talbot Terrane is limited, though a monzogranite that cuts D2 fabrics yields a U−Pb zircon age of c. 1476 Ma (Nelson, 1996; Bagas, 2004). Qualitative P−T conditions for the M2 event were previously estimated to have reached approximately ≥5 kbar and 600 °C, based on the presence of kyanite–staurolite and garnet–staurolite bearing assemblages (Clarke, 1991). However, these metamorphic mineral assemblages, and therefore P–T conditions, have not been temporally quantified to have grown during D2−M2.

2.2 Connaughton Terrane

The Connaughton Terrane contains multiply deformed banded iron-formation, metasediments, metachert, orthogneiss and metagranitoids and voluminous deformed mafic rocks that have been metamorphosed at amphibolite to granulite facies conditions (Bagas and Smithies, 1998; Bagas et al., 2000). Available zircon U−Pb geochronology of two samples of the voluminous orthogneisses and metagranitoids of the Kalkan Supersuite yield U−Pb zircon magmatic crystallisation ages of c. 1780−1770 Ma and are interpreted to be coeval with D2, similar to the Talbot Terrane (Nelson, 1995, 1996; Bagas, 2004). A garnet-bearing microgneiss and pegmatite, both interpreted to post-date D2 yield U−Pb zircon magmatic crystallisation ages of c. 1222 and c. 1291 Ma respectively (Nelson, 1995, 1996). Recently, Kirkland et al (2013) reinterpreted a c. 1200 Ma U–Pb zircon analysis from the

Tabletop T errane

Meso to Neoproterozoic sedimentary rocks

Phanerozoic

Orthogneiss and granitoid rocks

Metasediments, amphibolite and ultramafic rocks

MetasedimentsTalbot T errane

Connaughton T errane

Orthogneiss and granitoid rocks

Fault

Thrust

Sample locality

122°00’ 123°00’22

°30’

23°0

0’

Southwest Thrust

0 20km

N

103603D

103617 103618

115638

115669

115866

Figure 2

Camel-Tabletop Fault Zone

113019

Fig. 2. Map of the Rudall Province, showing lithological associations, major structures and sample locations. Modified from Geological Survey of Western Australia (1999).

105


Tabl

e 1.

Geo

logi

cal h

isto

ry o

f the

Rud

all P

rovi

nce

Even

tsTa

lbot

Ter

rane

Con

naug

hton

Ter

rane

Tabl

etop

Ter

rane

Con

stra

inin

g da

taR

efer

ence

<c.

2800

Ma

Sedi

men

tatio

n: M

axim

um

depo

sitio

nal a

ge fo

r qua

rtzite

U-P

b zi

rcon

geo

chro

nolo

gyM

aidm

ent,

(200

7)

>180

0 M

aSe

dim

enta

tion

of o

lder

turb

iditi

c su

cces

sion

Sedi

men

tatio

nM

inim

um a

ge d

efin

ed b

y pr

e D

1 in

trusi

ves

Hic

kman

and

Bag

as, (

1998

); Ba

gas,

(200

4)c.

201

5* M

a, 1

800

Ma

Pre

D1

gran

itoid

s?

Cry

stal

lisat

ion

ages

of b

ande

d or

thog

neis

s in

terp

rete

d to

con

tain

ear

ly fo

liatio

ns.

Nel

son,

(199

5); H

ickm

an a

nd

Baga

s, (1

998)

; Kirk

land

et a

l. (2

013)

c. 1

800

Ma

Yapu

ngku

Oro

geny

(D

1-M

1)D

1: L

ayer

par

alle

l she

ar, l

ayer

par

alle

l sc

hist

osity

D1:

Poo

rly p

rese

rved

but

infe

rred

S1

incl

usio

n tra

ils in

som

e ga

rnet

gra

ins

in

amph

ibol

ite

?Ag

e in

ferre

d ba

sed

on p

re a

nd p

ost D

1 in

trusi

ves

of c

. 18

00 M

a, n

o di

rect

age

co

nstra

ints

Nel

son,

(199

5); B

agas

, (20

04);

see

Kirk

land

et a

l. (2

013)

for

rein

terp

reta

tion

of U

-Pb

data

M1:

Am

phib

olite

faci

es m

etam

orph

ism

, an

dalu

site

bea

ring

asse

mbl

ages

(hig

h ap

pare

nt th

erm

al g

radi

ents

)

M1:

Poo

rly p

rese

rved

but

infe

rred

asse

mbl

age

of g

arne

t, ep

idot

e,

horn

blen

de, a

patit

e in

maf

ic a

mph

ibol

ite

c. 1

790

Ma

Sedi

men

tatio

n (d

epos

ition

of F

ingo

on

Qua

rtzite

)M

axim

um d

epos

ition

al a

ge o

f pro

tolit

h to

Fi

ngoo

n Q

uartz

iteN

elso

n, (1

995)

c. 1

800-

1760

Ma

Yapu

ngku

O

roge

ny (D

2-M

2)^

D2:

N-N

W tr

endi

ng is

oclin

al fo

lds,

E to

NE

dipp

ing

thru

sts

with

you

nger

thru

sts

to th

e E-

N

E, W

to S

W m

ovem

ent,

S2 c

omm

only

de

fined

by

alig

nmen

t of m

icas

and

qua

rtz

D2:

N-N

W tr

endi

ng is

oclin

al fo

lds,

E to

N

E di

ppin

g th

rust

s w

ith y

oung

er th

rust

s to

the

E- N

E, W

to S

W m

ovem

ent

?Ag

e co

nstra

ined

by

crys

talli

satio

n ag

es o

f in

terp

rete

d pr

e, s

yn a

nd p

ost g

rani

toid

sBa

gas

(200

4); B

agas

et a

l, (2

000)

M2:

am

phib

olite

faci

es m

etam

orph

ism

, ~ >

5

kbar

, 600

° C

M2:

am

phib

olite

-gra

nulit

e fa

cies

, pea

k co

nditi

ons

~12

kbar

, up

to ~

800

°C,

follo

wed

by

stee

p de

com

pres

sion

ther

mob

arom

etry

on

amph

ibol

ite a

nd

biot

ite-g

arne

t gne

iss

sam

ples

Cla

rke

(199

1); S

mith

ies

and

Baga

s (1

997)

c. 1

800-

1765

Ma

Empl

acem

ent o

f the

Kal

kan

Supe

rsui

teEm

plac

emen

t of t

he K

alka

n Su

pers

uite

Kirk

land

et a

l. (2

013)

; Nel

son,

(1

995;

199

6)po

st- D

2In

ferre

d m

etam

orph

ism

of

orth

opyr

oxen

e-ga

rnet

gne

iss

('cha

rnoc

kite

'), ~

2.4−

3.7

kbar

, 770

−860

°C

ther

mob

arom

etry

Smith

ies

and

Baga

s (1

997)

c. 1

590-

1550

Ma

Cal

c-al

kalin

e m

agm

atis

m o

f the

Kr

acka

tinny

Sup

ersu

iteU

-Pb

zirc

on g

eoch

rono

logy

Mai

dmen

t (20

07),

Mai

dmen

t (2

014)

c. 1

475-

1450

Ma

Cry

stal

lisat

ion

of m

onzo

gran

ite (p

ost-D

2 pr

e D

4)C

ryst

allis

atio

n of

gra

nodi

orite

(pos

t D

2- p

re D

4)U

-Pb

zirc

on g

eoch

rono

logy

Nel

son

(199

6); B

agas

(200

4)

c. 1

330

Ma

Rb-

SrC

hin

and

de L

aete

r (19

81)

c. 1

310-

1222

Ma

Cry

stal

lisat

ion

of p

ost D

2 ga

rnet

m

icro

gnei

ss, r

eint

erpr

eted

as

met

amor

phic

age

(one

ana

lysi

s)

Cry

stal

lisat

ion

of in

terp

rete

d po

st

D2

intru

sive

s, p

egm

atite

U

-Pb

zirc

onBa

gas

(200

4); N

elso

n (1

995;

19

96);

Kirk

land

et a

l (20

13)

c. 6

50 M

a M

iles

Oro

gney

(D3-

4,

M3-

4)D

3: lo

cal r

ecum

bent

fold

ing,

D4:

upr

ight

, tig

ht

fold

ing,

SW

dire

cted

com

pres

sion

, S4

axia

l su

rface

cle

avag

e

D4:

upr

ight

, tig

ht fo

ldin

g, S

W d

irect

ed

com

pres

sion

, S4

axia

l sur

face

cle

avag

eD

4: u

prig

ht, t

ight

fold

ing,

SW

di

rect

ed c

ompr

essi

on, S

4 ax

ial

surfa

ce c

leav

age,

form

atio

n of

the

Cam

el-T

able

top

Shea

r Zon

e

Min

imum

age

con

stra

ined

by

post

-D4

intru

sive

cry

stal

lisat

ion

age

Cza

rnot

a et

al (

2009

) and

re

fere

nces

ther

in

M3-

4: g

reen

schi

st fa

cies

met

amor

phis

mM

3-4:

gre

ensc

hist

faci

es m

etam

orph

ism

c. 8

00-6

10 M

a B

lake

Mov

emen

t (D

5)Lo

cal d

efor

mat

ion,

NW

- dire

cted

co

mpr

essi

on, o

pen

fold

sLo

cal d

efor

mat

ion

Loca

l def

orm

atio

nBa

gas,

(200

4); B

agas

et a

l. (2

000)

c.

550

Ma

Pate

rson

Oro

geny

(D

6)D

6: B

rittle

def

orm

atio

n, N

NE-

dire

cted

co

mpr

essi

on, W

NW

-NW

stri

king

stri

ke s

lip

and

thru

st fa

ults

D6:

Brit

tle d

efor

mat

ion,

NN

E- d

irect

ed

com

pres

sion

, WN

W-N

W s

triki

ng s

trike

sl

ip a

nd th

rust

faul

ts

D6:

Brit

tle d

efor

mat

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106

Chapter 4 Mesoproterozoic metamorphism in the Rudall Provincegarnet-bearing microgneiss as metamorphic based on Cathodoluminescence zircon imagery.

Quantitative P−T estimates for metamorphic mineral assemblages in the Connaughton Terrane are based on conventional thermobarometry for garnet–clinopyroxene, orthopyroxene–clinopyoxene, garnet–biotite and orthopyroxene–garnet bearing assemblages (Smithies and Bagas, 1997). The P–T conditions have been attributed to M2 (i.e. c. 1800–1765 Ma). Estimated peak P−T conditions of up to ~12 kbar and ~770 °C were obtained from mafic amphibolite from the ‘kyanite zone’, and ~800 °C at 7 kbar were obtained from orthopyroxene-clinopyroxene bearing amphibolite from the ‘sillimanite zone’ (Smithies and Bagas, 1997). The P−T evolution of the Connaughton as well as Talbot Terrane was inferred by Smithies and Bagas (1997) to have followed a steeply decompressive clockwise path, based on the presence of symplectic plagioclase-hornblende coronas on garnet in some mafic amphibolites. P−T estimates corresponding to very high thermal gradient conditions (~2.4−3.7 kbar, ~770−860 °C; thermal gradient of approximately 210–360 °C kbar -1) were obtained from an orthopyroxene–garnet gneiss that is interpreted to record post M2−D2 conditions driven by magmatism (Smithies and Bagas, 1997).

2.3 Tabletop Terrane

The Tabletop Terrane is separated from the Talbot and Connaughton Terranes by the southeast trending Camel–Tabletop Fault that postdates the Kalkan Supersuite. Outcropping areas of the Tabletop Terrane are comprised of volumetrically extensive felsic and mafic intrusives that have been metamorphosed to greenschist facies, dolerite dykes, ultramafic schists and low-volume supracrustal rocks (Bagas and Smithies, 1998). The Krackatinny Supersuite exhibits calc-alkaline geochemical signatures and were largely emplaced at c. 1590−1550 Ma (Maidment, 2007; Neumann and Fraser, 2007). Other felsic intrusives record U−Pb zircon magmatic crystallisation ages of c. 1476 Ma and 1310 Ma (Nelson, 1996; Bagas, 2004). No metamorphic work has

been undertaken on rocks from the Tabletop Terrane.

2.4 Constraints on tectonic boundaries in the Rudall Province

Earlier work on the Rudall Complex assigned rocks in the Talbot Terrane to belong to an eastern and western supracrustal suite based on distinct lithologies and magmatic ages (Bagas, 2004). Bagas (2004) suggested that the eastern and western supracrustal suites of the Rudall Province preserved early magmatic and metamorphic histories that were similar to the Paleoproterozoic Arunta Region (eastern supracrustal) and Gascoyne Complex (western supracrustal), and suggested that the boundary between these supracrustal suites may represent a terrane boundary between the NAC and WAC. Whereas there is an apparent absence of the Kalkan Supersuite in the Tabletop Terrane, the Camel-Tabletop Fault is not interpreted as a major crustal boundary given the common crustal source region of the Kalkan Supersuite and Tabletop granitic rocks (Kirkland et al., 2013). Kirkland et al. (2013) presented Hf isotopic data for interpreted magmatic and inherited zircon from previously dated (U–Pb zircon), variably deformed granitoids of the Kalkan Supersuite and intrusive rocks with younger crystallisation ages or age components between 1450 and 1200 Ma from the Connaughton, Talbot and Tabletop Terrane (Kirkland et al., 2013). The isotopic dataset of Kirkland et al. (2013) indicates the rocks of the Rudall Province were sourced from crust similar to that of the WAC. As such, the location of the suture between the WAC and NAC is likely to be to the east of the Rudall Province.

3. Sample descriptions

The aim of this study is to directly determine the timing of the peak regional metamorphism by dating minerals that grew during the metamorphic development, as opposed to previous studies that sought to constrain the timing of deformational/metamorphic events via dating of magmatic rocks with inferred emplacement relationships to deformation.

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Chapter 4 Mesoproterozoic metamorphism in the Rudall Province Samples for this study come from the Connaughton and Talbot Terranes and were obtained from the Geological Survey of Western Australia legacy collections. U–Pb zircon geochronology was conducted on an unmigmatised garnet-diopside bearing amphibolite. Additionally, zircon and garnet trace element chemistry was collected to assist in linking metamorphic silicate phases to zircon growth. U−Pb monazite geochronology was conducted on three metapelitic samples from the Talbot Terrane (within the Tjingkulatjatjarra Formation of Clarke, 1991) and three metasedimentary samples from the Connaughton Terrane. P–T pseudosections were calculated for one of the dated metapelitic samples from the Talbot Terrane and a garnet–diopside bearing amphibolite from the Connaughton Terrane.

3.1 Sample 103603D: Kyanite-bearing metapelite (Talbot Terrane)

Bladed kyanite (up to 5 mm) forms aggregates of up to ~15 mm that have aspect ratios of 1:1 to 1:3 (the latter with long axis aligned parallel to schistosity, Figure 3a). Albite is blocky and sub to euhedral (up to 10 mm along long axis). Chlorite (up to 2 mm) and muscovite (up to 6 mm) occur as grains oriented parallel with the foliation and as unoriented grains, and commonly surround and stop at the boundaries of kyanite. Muscovite and chlorite additionally separate kyanite and plagioclase. Fine-grained rutile–ilmenite grains and apatite occur in contact with chlorite, plagioclase, muscovite and retrograde sericite (<0.5 mm). Monazite grains occur as inclusions in chlorite, muscovite and sericite. Kyanite, plagioclase, quartz and rutile–ilmenite are interpreted to comprise the peak metamorphic assemblage, which has been overprinted by retrograde chlorite–muscovite and later sericite.

3.2 Samples 103617 and 103618: staurolite-biotite bearing metapelites (Talbot Terrane)

Sample 103617 exhibits a single foliation defined by subhedral biotite (up to about 10 mm) and in places by staurolite (up to 15 mm long, aspect ratio about 1:1–1:15). Staurolite occurs as poikiloblasts with

inclusions of quartz, plagioclase and ilmenite (<0.5 mm), and inclusion poor grains, with some poikiloblastic staurolite occurring as rims on inclusion-poor staurolite grains (Figure 3b). Quartz (up to 6 mm), plagioclase (up to 5 mm), subhedral apatite (< 1 mm), intergrowths of rutile−magnetite (potentially previously ilmenite <1 mm) and fine grained magnetite (<< 1 mm) comprise the matrix. Fine-grained ilmenite additionally occurs within staurolite fractures. Subhedral to anhedral chlorite (up to 10 mm, aspect ratio 1:1−1:3) typically occurs as oriented and unoriented grains, in contact with biotite and staurolite, and commonly infills embayed staurolite grain boundaries. Chlorite is interpreted to have grown at the expense of staurolite, and there is late sericite development. Monazite occurs as inclusions in staurolite and within the matrix. The peak assemblage for sample 103617 is interpreted to be staurolite–plagioclase–quartz–ilmenite–magnetite. Chlorite is interpreted to post-date peak metamorphism. All minerals except chlorite and sericite have previously been interpreted as being stable during S2 (Clarke, pers. comm).

Sample 103618 contains an S–C style fabric in which biotite, staurolite and chlorite define the S and C planes. Staurolite grains are curvilinear in 2D sections, up to 8 mm long and typically have aspect ratios from 1:1 to 1:10 (Figure 3c). Staurolite commonly occurs in aggregates intergrown with quartz and plagioclase that are interpreted to be poikiloblasts. In places these poikiloblasts are wrapped by biotite and chlorite foliae. Subhedral biotite and chlorite (up to 6 mm long) are intergrown with each other, define the fabric and are in direct contact with matrix quartz (< 2mm), plagioclase (< 5 mm) and magnetite (<1 mm). Both chlorite and biotite are in direct contact with staurolite. Ilmenite grains (and ilmenite-rutile intergrowths) are fine grained (<0.5 mm) occur as inclusions in staurolite, in contact with biotite and in the matrix and are commonly aligned parallel to the foliation. Magnetite grains are typically anhedral, unoriented, up to 1 mm in size and occur in the matrix. Monazite grains occur as staurolite inclusions and in the matrix. The peak assemblage for sample 103618 is interpreted to be staurolite–plagioclase–

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quartz–chlorite–biotite–magnetite–ilmenite.

3.3 Sample 115638: Quartz-garnet-sillimanite gneiss (Connaughton Terrane)

Sample 115638 was described by Smithies and Bagas (1997) but not used for thermobarometry. The sample contains equant subhedral garnet grains (< 2 mm) that are typically poikiloblastic, containing fine-grained lobate quartz and K-feldspar, and subhedral rutile inclusions (typically <0.5 mm, Figure 3d). Prismatic sillimanite is <1 mm in length and occurs as oriented and unoriented grains, in areas deflecting around garnet. Sillimanite, quartz and K-feldspar (<0.5–2 mm, aspect ratios of 1:1 to 1:3 aligned with the foliation), rutile and ilmenite grains (< 0.5 mm) comprise the matrix and are in contact with garnet. The foliation is defined in places defined by K-feldspar, quartz and sillimanite. Monazite grains occur the matrix and as inclusions in garnet. The interpreted peak mineral assemblage is garnet–sillimanite–plagioclase–K-feldspar–quartz–rutile–ilmenite. Garnet and sillimanite were interpreted by Smithies and Bagas (1997) as late- to post-D2 based on the observation that sillimanite grains define as well as cross cut the foliation, and some garnet grains that show minimal or no deflection of the S2 foliation.

3.4 Sample 115669: Kyanite-sillimanite quartzite (Connaughton Terrane)

Sample 115669 was described by Smithies and Bagas (1997). The sample is quartz -rich and contains kyanite and sillimanite. At the scale of the thin section, localised strain varies from medium to high on the basis of the aspect ratios of quartz in different layers of the fabric (~1:1−1:5, Figure 3e). Prismatic to bladed kyanite (<1 mm long) is interpreted to have been variably recrystallised parallel to foliation, and is partly replaced by acicular to fibrolitic sillimanite (<<1 mm). Sillimanite defines the fabric and also cross cuts the fabric, overprinting quartz and kyanite. Ilmenite–magnetite porphyroblasts (up to about 5 mm long) also occur in the sample and are partially surrounded by chloritoid, which is interpreted to be replacing the porphyroblasts. Quartz (<2 mm) comprises the bulk of the matrix, with

minor fine-grained muscovite also present. Monazite grains occur in the matrix. Smithies and Bagas (1997) inferred sample 115669 to be located close to the sillimanite–kyanite isograd. In addition, they inferred and that sillimanite growth was late with respect to D2, and the change from kyanite to sillimanite stability occurred on the prograde path of a single tectonic cycle.

3.5 Sample 115866: Garnet-orthopyroxene gneiss (Connaughton Terrane)

This sample is located close to the Camel–Tabletop Fault zone in the Connaughton Terrane, and was termed a charnockite by Bagas and Smithies (1998). Bagas et al. (2000) reinterpreted the rock to potentially represent quartzofeldspathic/psammitic metasediment. Smithies and Bagas (1997) used this sample for conventional thermobarometry and retrieved very high thermal gradient conditions (~2–4 kbar, 800 °C). The lithology was interpreted to have a foliation unrelated to S2 and therefore could relate to a thermal/metamorphic event post-dating D2 (Smithies and Bagas, 1997). The gneissic fabric is defined by discontinuous layers of orthopyroxene, garnet, ilmenite and magnetite alternating with layers of abundant plagioclase, quartz, K-feldspar and perthite/mesoperthite. Garnet is fine grained (< 1mm) and occurs in a number of morphologies: 1) as equant grains in the matrix; 2) as coronae on fine-grained (<1 mm) magnetite or ilmenite; 3) as quartz–garnet symplectites surrounding, or in contact with, magnetite or ilmenite (e.g. Figure 3f); and 4) in contact and partly surrounded by fine-grained quartz−biotite symplectites. Orthopyroxene occurs as aggregates up to 2 mm in size. Magnetite and ilmenite grains that are mantled by garnet or garnet–quartz symplectites commonly occur next to orthopyroxene. Other grains of magnetite(-spinel) and ilmenite (both <1 mm) are not mantled by garnet, but may be mantled by fine-grained biotite. Anhedral quartz, plagioclase and perthite/mesoperthite (approximately 0.5–2 mm) occur in the matrix, with subhedral to anhedral biotite (<3 mm). Monazite grains occur in the matrix, in contact with quartz/feldspar or magnetite(-spinel), or biotite. The peak assemblage is interpreted to

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have been orthopyroxene–garnet–magnetite–ilmenite–plagioclase–K-feldspar–quartz and melt.

3.6 Sample 113019: Garnet−diopside amphibolite (Connaughton Terrane)

Sample 113019 is from the western Connaughton Terrane within the kyanite zone from the same lithology for which medium to high−P estimates for the Yapungku Orog-eny were obtained by Smithies and Bagas (1997). It is a foliated unmigmatised garnet−diopside-bearing amphibolite. Garnet grains

Figure 3

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Fig. 3. Thin section photos of samples used in this study: a) Sample 103603D, kyanite surrounded by fine grained sericite, and chlorite, quartz, albite and muscovite, b) sample 103617, staurolite with inclusion rich domains, in contact with plagioclase, quartz, ilmenite and biotite, c) sample 103618, staurolite, plagioclase and quartz wrapped by biotite, d) sample 115638, poikil-oblastic garnet in a quartz, K-feldspar, sillimanite, rutile and ilmenite matrix. Sillimanite is both in contact with and in areas wraps around garnet, defining the fabric of the rock, e) sample 115669, kyanite−sillimanite−quartz−magnetite sample, kyanite is in areas recrystallised parallel to the fabric, and fine-grained acicular sillimanite occurs as oriented grains parallel to the fabric and unoriented grains, and f) sample 115866, orthopyroxene adjacent to magnetite mantled by garnet−quartz symplectites in a K-feldspar, (meso)perthite, plagioclase, quartz matrix. Monazite is locally abundant.

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(~0.5−1.5 mm in diameter) are typically equant and contain very-fine-grained (<< 0.5 mm) titanite, quartz, plagioclase, hornblende and rare zircon inclusions that are unoriented or occur either as inclusion trails that transect the garnet grain or in the core of the garnet (Fig. 4). Diopside is fine-grained (< 1 mm) and occurs with matrix minerals plagioclase (< 2 mm, anhedral), quartz (< 1mm, anhe-dral), hornblende (< 2mm, subhedral to anhe-dral) and minor apatite and pyrite (< 0.5 mm). Hornblende is foliated and also partially sur-rounds garnet and diopside as fine−medium sized grains (< 2mm). Hornblende also occurs as part of a fine-grained and locally devel-oped symplectic intergrowth with plagioclase ± quartz ± titanite, partially separating garnet from matrix hornblende or diopside grains. The peak mineral assemblage is interpreted to be garnet−diopside−hornblende−plagioclase−quartz−titanite−apatite.

4. Analytical Techniques

4.1 Electron Microprobe Analysis (EPMA) spot and elemental maps

Mineral chemical composition analyses were obtained using a Cameca SXFive electron microprobe at the University of Adelaide using a beam current of 20 nA and accelerating voltage of 15 kV. Monazite elemental maps were obtained using a beam current of 200 nA and accelerating voltage of 15–20 kV. Y, Th, Ce, U and Pb were mapped using WDS and P was mapped using EDS.

4.2 Zircon and Monazite U–Pb Geochronology

Zircon from sample 113019 and monazite from the remaining six samples from the Rudall Province were analysed for U–Pb geochronology using the Laser Ablation–Inductively Coupled Plasma–Mass Spectrometer (LA−ICP−MS) at Adelaide Microscopy, University of Adelaide. Zircon from sample 113019 (garnet−diopside amphibolite) was prepared using panning, Franz and heavy liquid techniques at Geotrack International, and mounted in epoxy resin. Prior to laser ablation, zircon grains were imaged using a Gatan Cathodoluminescence (CL) detector attached to a Phillips XL40 SEM. Monazite grains were imaged using a Phillips XL30 SEM.

U–Pb analyses of zircon and monazite were obtained using an Agilent 7500cs ICP–MS with a New Wave 213 nm Nd–YAG laser in a helium ablation atmosphere. For zircon, a laser spot size of 20–30 μm, repetition rate of 5 Hz and laser intensity of 80–100 % was used. A 30 second gas blank was initially measured followed by 80 seconds of zircon sample ablation. The laser was fired for 10 seconds with the shutter closed prior to ablation in order to allow for beam and crystal stabilization. Analyses measured isotopes 204Pb, 206Pb, 207Pb, 208Pb, 232Th and 238U for 10, 15, 30, 10, 10, 15 ms respectively for zircon. Common lead was not corrected due to an unresolvable interference of 204Hg and 204Pb peaks. However, 204Pb was monitored to assess the common lead of each analysis.

500 µmTtn Qtz+Pl+Amph

symplectite

Pl

QtzHbl

Hbl

Qtz

Grt

HblDi

Figure 4. Photomicrograph of sample 113019 showing peak assemblage garnet, diopside, hornblende, quartz, plagioclase and titanite. Quartz, plagioclase, amphibole symplectite sepa-rating garnet and matrix hornblende is also shown.

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For monazite, a 15–16 μm spot size, repetition rate of 5 Hz and laser intensity of 80–100 % was used. A 30 second gas blank was initially measured followed by 40 to 50 seconds of monazite sample ablation. The laser was fired for 10 seconds with the shutter closed prior to ablation in order to allow for beam and crystal stabilisation. Analyses measured isotopes 204Pb, 206Pb, 207 Pb and 238U for 10, 15, 30 and 15 ms respectively for monazite. Common lead was not corrected for zircon or monazite analyses due to an unresolvable interference of 204Hg and 204Pb peaks. However, 204Pb was monitored to assess the common lead of each analysis.

Zircon and monazite data was corrected for mass-bias and fractionation using the real-time correction program Glitter v. 4.23 (Griffin et al., 2008). Gemoc zircon standard GJ-1 was used to correct for mass bias and fractionation (TIMS normalisation data: 207Pb/206Pb = 608.3 Ma, 206Pb/238U = 600.7 Ma and 207Pb/235U = 602.2 Ma; Jackson et al. 2004). An uncertainty of 1% was assigned to the age of the GJ-1 zircon standard. Accuracy of zircon analyses were monitored by analysing internal standards Plesovice (ID TIMS 206Pb/238U age = 337.13 ± 0.37 Ma; Sláma et al. 2008) and OG-1 (ID TIMS 207Pb/206Pb age = 3465.4 ± 0.6 Ma; Stern et al., 2009) prior to and throughout unknown analysis runs. Average Plesovice ages obtained during this study were 207Pb/235U = 339 ± 4 Ma (95 % confidence, n = 16, MSWD = 1.9), 207Pb/206Pb = 339 ± 17 Ma (MSWD = 0.38) and 206Pb/238U = 340 ± 2.9 Ma (MSWD = 2.9). Average OG-1 ages obtained during this study were 207Pb/206Pb = 3464 ± 15 Ma (95 % confidence, n = 6, MSWD = 0.6), 207Pb/235U = 3461 ± 37 Ma (MSWD = 6.3), and 206Pb/238U = 3458 ± 110 Ma (MSWD = 9.4).

Monazite standard Madel was used to correct for mass bias and fractionation for monazite analyses (TIMS Madel age: 207Pb/206Pb = 490.0 Ma, 206Pb/238U = 518.37 Ma and 207Pb/235U = 513.13 Ma; Payne et al., 2008, updated with additional TIMS data). 1% uncertainty was given to the age of the Madel standard for sample age error calculations. Accuracy was monitored by analysing the 222 (c. 450 Ma; Maidment, 2005) monazite standard prior to and throughout unknown

analysis runs. Average 222 ages obtained throughout this study were 207Pb/235U = 454 ± 2 Ma (95 % confidence, n = 59, MSWD = 1.2), 207Pb/206Pb = 461 ± 7 Ma (MSWD = 0.46) and 206Pb/238U = 452 ± 2 Ma (MSWD = 1.5). Conventional concordia, weighted averages, and linear probability plots were generated using Isoplot version 4.11 (Ludwig, 2008).

4.3 Zircon and garnet REE: Sample 113019

REE and trace elements of zircon and garnet grains were analysed using the LA−ICP−MS at Adelaide Microscopy). Zircon grains were analysed in grain mounts, whereas garnet grains were analysed in situ. Moderately luminescent zircon with homogenous, fir-tree zoned and irregular/patchy zones with pre-collected U–Th–Pb data were analysed. LA–ICP–MS REE chemistry of garnet grains were obtained via transects across garnet grains over pre-collected EPMA spot analysis transects. Analyses for zircon and garnet were conducted using 30 µm laser spot size at 100 % intensity and 5 Hz repetition rate. Total acquisition time was 100 seconds for zircon and 150 seconds for garnet, and incorporated 30 seconds of background acquisition and 10 seconds of laser firing with the shutter closed at the start of each zircon and garnet analysis. External standard Nist 610 was used to correct for fractionation and mass bias (Pearce et al. 1997), and standards Nist 612 and BHVO were used as internal standards to monitor the accuracy of analyses. Data was corrected using GLITTER software (Van Achterbergh et al. 2001). Analyses were calibrated internally using Hf oxide weight percent measurements on zircon domains and Ca oxide weight percent measurements on garnet corresponding to spot locations of LA–ICP–MS REE and trace element analyses using Cameca SX51 microprobe at Adelaide Microscopy. An accelerating voltage of 15 kV and beam current of 20 nA was used.

4.4 Mineral equilibria modelling

Bulk chemical compositions of samples 103618 and 113019 were determined using whole-rock geochemical analyses. Major element concentrations were determined by X-ray fluorescence (XRF), using a Panalytical

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2404 XRF unit at Franklin and Marshall College, United States. Samples were prepared for analysis by fusion of the milled sample with lithium tetraborate. Estimates on the proportion of Fe2O3 to FeO in the rocks were made by estimating the modal abundance of minerals in a sample and combining that information with oxide wt% compositions of Fe3+ bearing minerals recast for Fe2O3 using the stoichiometric method of Droop (1987). For staurolite–magnetite–ilmenite bearing sample 103618, 85% of the analysed Fe2O3 was converted to FeO.

P−T pseudosections were calculated using THERMOCALC v3.33 (October 2009 update of Powell and Holland, 1988), with the internally consistent dataset of Holland and Powell (1998; tc-ds55, Nov. 2003 update). The model chemical system NCKFMASHTO (Na 2O−CaO−K 2O−FeO−MgO−Al 2O 3−SiO2−H2O−TiO2−Fe2O3) was used for P−T pseudosection calculations for sample 103618 using a−x relationships of White et al. (2007) for biotite, garnet and silicate melt, White et al. (2000) for ilmenite and hematite, Holland and Powell (2003) for K-feldspar and plagioclase, Holland and Powell (1998) for cordierite, staurolite and epidote, Coggon and Holland (2002) for muscovite and paragonite, Holland et al. (1998) for chlorite and White et al. (2000) for magnetite.

For sample 113019, the model chemical system NCFMASHTO (Na2O−CaO−FeO−MgO−Al2O3−SiO2−H2O−TiO2−Fe2O3) was used for sample 113019 using a−x relationships of Green et al. (2007) for clinopyroxene, Diener et al. (2007) for hornblende, White et al. (2007) for garnet, Holland and Powell (1998) for epidote, Holland et al. (1998) for chlorite, Holland and Powell (2003) for plagioclase and White et al. (2000) for ilmenite. Estimates on the proportion of Fe2O3 to FeO were made by estimating the modal abundance of minerals in the sample and combining that information with oxide wt.% compositions of Fe3+ bearing minerals recast for Fe2O3 using the stoichiometric method of Droop (1987). 90% of the analysed Fe2O3 was converted to FeO for sample 113019. Water was set to excess (water saturated) for samples 103618 and 113019 as peak P–T conditions of

both samples are interpreted to be subsolidus.

5. Results

Representative EPMA spot analyses are provided in Table 2 and mineral chemistry is detailed in Appendix 1.

5.1 In situ monazite U–Pb Geochronology

Representative EPMA maps and BSE images of monazite for sample 115638 and 115866 are shown in Figure 5. BSE images of monazite grains from samples 103603D, 103617, 103618 and 115669 are shown in Figure 6a−d. Cathodoluminescence images of zircon from sample 113019 are show in Figure 6e. U−Pb geochronology data are provided in Appendix 2.

5.1.1. Sample 103603D (kyanite−bearing pelite, Talbot Terrane)

Monazite grains occur as inclusions in chlorite, muscovite and sericite, do not show zoning in BSE imagery and range in size from ~50 to 200 µm. Twenty analyses were obtained (Fig. 7a, b). Seventeen analyses are within 5 % concordance, lie on a linear array in the plotted linear probability diagram, and are interpreted to comprise one age population. The above concordant analyses yield a Pb207/Pb206 age weighted average of 1275 ± 11 Ma (n = 17, MSWD = 0.3, 95 % confidence).

5.1.2. Sample 103617 (staurolite−bearing pelite, Talbot Terrane)

Monazite grains range from ~20 to 100 µm and show variable internal morphologies in BSE imagery varying from no zoning, irregular/patchy zoning to monazite grains with lighter cores. Thirty-five analyses were obtained from monazite grains located within the matrix and as inclusions in staurolite grains (Fig. 7c). 100 ± 5 % concordant analyses were included in the linearised probability plot (Fig. 7d). 25 analyses form a linear array on Figure 7d and are interpreted as one age population. These analyses yield a Pb207/Pb206 age weighted average of 1666 ± 8 Ma (n = 25, MSWD = 0.73, 95 % confidence).

113


Table 2. Representative mineral compositions for samples 103617 and 103618Sample 103617 103617 103617 103617 103617 103617 103618 103618 103618 103618 103618 103618 103618Mineral Chl Bt St Qtz Pl Mag Chl Bt St Qtz Pl Mag IlmID number 1 51 18 30 34 40 72 42 4 44 67 36

SiO₂ 26.29 34.93 26.36 98.66 65.80 0.35 24.65 33.96 25.90 99.11 67.42 0.31 0.04TiO₂ 0.42 1.13 0.55 0.00 0.01 0.06 0.08 1.42 0.55 0.01 0.00 0.03 52.12Al2O₃ 22.56 17.96 52.88 0.01 19.79 0.14 22.46 19.30 52.02 0.02 18.57 0.46 0.01Cr2O₃ 0.02 0.00 0.00 0.01 0.00 0.00 0.01 0.03 0.00 0.01 0.00 0.00 0.01FeO 19.63 17.41 13.23 0.02 0.00 90.49 21.38 18.19 14.67 0.00 0.00 87.10 44.52MnO 0.07 0.08 0.26 0.01 0.00 0.04 0.10 0.05 0.22 0.00 0.01 0.01 1.28MgO 18.83 14.51 2.07 0.00 0.00 0.05 18.48 13.33 1.83 0.00 0.00 0.01 0.31ZnO 0.00 0.00 0.14 0.00 0.03 0.05 0.02 0.03 0.00 0.00 0.03 0.03 0.06CaO 0.00 0.00 0.01 0.01 0.49 0.04 0.02 0.07 0.01 0.00 0.78 0.03 0.00Na₂O 0.01 0.16 0.00 0.02 11.75 0.02 0.00 0.20 0.00 0.00 11.72 0.04 0.01K₂O 0.56 8.13 0.00 0.00 0.05 0.04 0.06 7.37 0.01 0.01 0.04 0.00 0.01Total 88.39 94.31 95.51 98.73 97.92 91.29 87.25 93.95 95.22 99.17 98.56 88.02 98.37No. Oxygens 14 11 46 2 8 4 14 11 46 2 8 4 3Si 2.67 2.65 7.51 1.00 2.95 0.01 2.56 2.59 7.46 1.00 3.00 0.01 0.00Ti 0.03 0.06 0.12 0.00 0.00 0.00 0.01 0.08 0.12 0.00 0.00 0.00 1.00Al 2.70 1.61 17.75 0.00 1.04 0.01 2.75 1.73 17.65 0.00 0.97 0.02 0.00Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00Fe³+ 1.97 1.95 0.00Fe²+ 1.66 1.10 3.15 0.00 0.00 1.00 1.86 1.16 3.53 0.00 0.00 1.00 0.95Mn²+ 0.01 0.01 0.06 0.00 0.00 0.00 0.01 0.00 0.05 0.00 0.00 0.00 0.03Mg 2.85 1.64 0.88 0.00 0.00 0.00 2.86 1.51 0.78 0.00 0.00 0.00 0.01Zn 0.00 0.00 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00Ca 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.01 0.00 0.00 0.04 0.00 0.00Na 0.00 0.02 0.00 0.00 1.02 0.00 0.00 0.03 0.00 0.00 1.01 0.00 0.00K 0.07 0.79 0.00 0.00 0.00 0.00 0.01 0.72 0.00 0.00 0.00 0.00 0.00

Total Cations (S) 10 8 29.5 1 5 3 10 8 30 1 5 3 2

X( Mg) = (Mg/(Fe+Mg)) 0.63 0.60 0.22 0.61 0.57 0.18 0.01X( Na) = (Na/(Na+Ca) 0.98 0.96X( Mg) = (Mg/(Mg+Zn+Fe²++Mn) 0.01

5.1.3. Sample 103618 (staurolite−bearing pelite, Talbot Terrane)

Monazite grains are ~40–200 µm in size, occur both in the matrix and as inclusions within staurolite, and display internal morphologies in BSE imagery that vary from no zoning to patchy zoning. 25 analyses were obtained, with 23 analyses are within 100 ± 5 % concordance and are shown in linearised probability plot (Fig. 7e, f). A Pb207/Pb206 age weighted average of 1283 ± 9 Ma (n = 22, MSWD = 0.58, 95 % confidence) was calculated from analyses which lie along a linear array. One older analysis from a monazite grain located in the matrix was excluded from the weighted average.

5.1.4. Sample 115638 (garnet−sillimanite gneiss, Connaughton Terrane)

Monazite grains are ~20–150 µm in size and show internal morphologies in BSE imagery that range from no visible zoning,

zoning with either darker or lighter cores, and concentric zoning. Th and Y elemental maps of representative monazite grains show monazite grains commonly contain a Th enriched core and do not show appreciable Y zoning. Th-poor rims were too narrow to be analysed using LA–ICP–MS. Eighteen analyses were obtained from monazite grains located within the matrix and as inclusions in garnet grains. Sixteen analyses yield results within 100 ± 5 % concordance. These concordant analyses were included in the linearised probability diagram and lie on a linear array (Fig. 8a, b). The above concordant analyses are interpreted to comprise one age population and yield Pb207/Pb206 age weighted average of 1307 ± 12 Ma (n = 16, MSWD = 0.87, 95 % confidence).

5.1.5. Sample 115669 (kyanite−sillimanite quartzite, Connaughton Terrane)

Monazite grains vary in size from 20 to 200 µm and exhibit internal morphologies that vary from no visible zoning, patchy/irregular zoning to darker or lighter cores under BSE. Nineteen analyses were obtained on monazite

114

Chapter 4 Mesoproterozoic metamorphism in the Rudall ProvinceTa

ble

2. R

epre

sent

ativ

e m

iner

al c

ompo

sitio

ns fo

r sam

ples

115

866

and

1130

19Sa

mpl

e11

5866

1158

6611

5866

1158

6611

5866

1158

6611

5866

1158

6611

5866

1130

1911

3019

1130

1911

3019

1130

1911

3019

1130

19M

iner

alG

rt- m

atrix

Grt-

Cor

ona

Opx

PlKf

sQ

tzM

agIlm

BtG

rt-rim

Grt-

core

Di

Hbl

PlTt

nQ

tzID

num

ber

5491

8627

3022

8397

133

1999

3410

337

36

SiO₂

38.3

137

.59

45.1

360

.00

65.3

597

.45

0.04

0.05

39.4

438

.47

38.0

851

.85

41.3

862

.67

30.4

296

.53

TiO₂

0.04

0.03

0.24

0.04

0.03

0.07

0.04

49.0

72.

030.

030.

140.

191.

160.

0037

.02

0.00

Al2O

₃21

.37

20.9

89.

8924

.50

19.7

70.

160.

270.

0215

.15

20.8

520

.62

4.11

11.9

523

.43

1.17

0.02

Cr2

O₃

0.03

0.01

0.02

0.00

0.01

0.02

0.10

0.01

0.00

0.04

0.01

0.05

0.03

0.06

0.01

0.00

FeO

25.8

526

.96

23.0

70.

060.

040.

0587

.96

45.9

29.

6925

.05

24.6

110

.42

17.5

50.

080.

570.

52M

nO2.

312.

490.

640.

010.

000.

000.

080.

760.

081.

040.

820.

100.

110.

010.

010.

00M

gO10

.02

9.30

19.0

40.

000.

000.

010.

000.

7019

.76

3.18

3.45

11.1

410

.35

0.00

0.00

0.00

ZnO

0.00

0.05

0.00

0.04

0.00

0.00

0.04

0.09

0.00

0.00

0.00

0.01

0.05

0.00

0.00

0.00

CaO

0.85

0.81

0.05

6.36

0.89

0.00

0.02

0.02

0.01

11.6

812

.35

19.8

510

.63

4.77

29.0

50.

05N

a₂O

0.01

0.00

0.02

8.06

2.62

0.00

0.02

0.01

0.04

0.00

0.00

2.02

2.19

8.86

0.01

0.00

K₂O

0.00

0.01

0.00

0.14

11.6

60.

040.

000.

019.

370.

000.

010.

000.

220.

050.

000.

00To

tal

98.7

898

.24

98.1

199

.21

100.

3797

.80

88.5

796

.65

95.5

710

0.34

100.

1099

.74

95.6

299

.91

98.2

697

.12

No.

Oxy

gens

1212

68

82

43

1112

126

238

52

Si2.

992.

971.

702.

692.

961.

000.

000.

002.

853.

023.

001.

946.

362.

781.

011.

00Ti

0.00

0.00

0.01

0.00

0.00

0.00

0.00

0.96

0.11

0.00

0.01

0.01

0.13

0.00

0.93

0.00

Al1.

961.

950.

451.

301.

050.

000.

010.

001.

291.

931.

910.

182.

171.

220.

050.

00C

r0.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

00Fe

³+0.

131.

980.

080.

09Fe

²+1.

691.

780.

600.

000.

000.

001.

000.

910.

581.

641.

620.

332.

260.

000.

020.

00M

n²+

0.15

0.17

0.02

0.00

0.00

0.00

0.00

0.02

0.00

0.07

0.05

0.00

0.01

0.00

0.00

0.00

Mg

1.16

1.10

1.08

0.00

0.00

0.00

0.00

0.03

2.13

0.37

0.40

0.62

2.37

0.00

0.00

0.00

Zn0.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

000.

010.

000.

000.

00C

a0.

070.

070.

000.

310.

040.

000.

000.

000.

000.

981.

040.

801.

750.

231.

040.

00N

a0.

000.

000.

000.

700.

230.

000.

000.

000.

010.

000.

000.

150.

650.

760.

000.

00K

0.00

0.00

0.00

0.01

0.67

0.00

0.00

0.00

0.86

0.00

0.00

0.00

0.04

0.00

0.00

0.00

Tota

l Cat

ions

(S)

88

45

51

32

88

84

165

31

XM

g =

(Mg/

(Fe+

Mg)

)0.

410.

380.

640.

030.

780.

180.

200.

660.

51X

Mg

= (M

g/(M

g+Zn

+Fe²

+ +Mn)

0.03

X(A

lm)

0.55

0.57

0.54

0.52

X(P

y)0.

380.

350.

120.

13X

(Grs

)0.

020.

020.

320.

33X

(Sps

s)0.

050.

050.

020.

02X

(An)

= (C

a/(C

a+N

a+K)

0.30

0.05

0.23

X(O

r) =

(K/(N

a+C

a+K)

0.01

0.71

0.00

115


M06b1276 ± 24 Ma104 % conc.

b.a) b)

d) e)

g) h)

j) k)

m) n)

p) q)

96 %

±

M03c1337 ± 24 Ma100 % conc.

M03a1362 ± 25 Ma98 % conc.

M03b1362 ± 24 Ma97 % conc.

M03g1360 ± 25 Ma97 % conc.

M03g1280 ± 26 Ma102 % conc.

M03h1393 ± 26 Ma97 % conc.

M03d1337 ± 25 Ma98 % conc.

M03e1354 ± 26 Ma96 % conc.

M01a1334 ± 25 Ma101 % conc.

M01b1414 ± 24 Ma96 % conc.

M06d1338 ± 25 Ma98 % conc.

M06a1340 ± 25 Ma100 % conc.

M06b1354 ± 25 Ma98 % conc.

M05a1319 ± 24 Ma101 % conc.

M05b1285 ± 25 Ma99 % conc.

M061279 ± 24 Ma103 % conc.

M161309 ± 27 Ma100 % conc.

c)

f)

i)

l)

o)

r)

Figure 5

M06c1356 ± 25 Ma96 % conc.

Fig. 5. Th and Y EPMA maps, and BSE images of monazite grains from samples 115866 (a−i) and 115638 (j−r) with location of LA-ICP-MS spot and 207Pb/206Pb ages shown.

grains from the matrix. Seventeen analyses yield results within 100 ± 5 % concordancy and plot on a linear array (Fig. 8c, d). These analyses are considered to be one population and yield a Pb207/Pb206 age weighted average of 1295 ± 11 Ma (n = 17, MSWD = 0.63, 95 % confidence).

5.1.6. Sample 115866 (garnet−orthopyroxene gneiss, Connaughton Terrane)

Monazite grains are ~50 to 1000 µm in size and show internal morphologies in BSE imagery that vary from no visible zoning, lighter cores to irregular zoning. Th and Y

116


m06

m04

m14

a)a b

c d

M06-2 1271 ± 23 Ma102 % conc.

M04-2 1264 ± 23 Ma101 % conc.

M21-2 1721 ± 23 Ma95 % conc.

M25a-2 1688 ± 21 Ma 101 % conc.

M25b-2 1668 ± 21 Ma100 % conc.

M18-1 1573 ± 28 Ma103 % conc.

M22-1 1277 ± 23 Ma98 % conc.

M17b 1306 ± 22 Ma99 % conc.

M17b 1306 ± 22 Ma99 % conc.

M17a 1295 ± 21 Ma105 % conc.

M14 1320 ± 21 Ma 100 % conc.

Z03-2

1361 ± 52 Ma

94 % conc.

Z17-1

1323 ± 98 Ma

102 % conc.

Z27-1

1347 ±

47 Ma

95 % conc.

50 μm

e

Fig. 6. BSE images of monazite grains from a) sample 103603D, b) sample 103617, c) sample 103618, and d) 115669. Cath-odoluminescence images of zircon from sample 113019 (e).

elemental maps for representative monazite grains show zoning in Th, with higher Th in cores for some grains, and at grain boundaries for other grains (Fig. 5a–i). Y zoning in monazite grains are limited to patchy domains of higher or lower Y or some increase in Y at the edges of grains. There is no consistent correspondence between Th or Y and age. Thirty-three analyses were obtained from grains located in the matrix; in contact with quartz and feldspar with some grains also in contact with magnetite and/or spinel or fine grained biotite. Thirty-one analyses are within 100 ± 5 % concordance and of these analyses all but one are considered to be one population using a linearised probability plot (Fig. 8e, f). The age population yields a calculated Pb207/Pb206 age weighted average of 1341 ± 10 Ma (n = 30, MSWD = 1.13, 95 % confidence).

No correspondence between age and internal morphology or textural location was observed.

5.2 Zircon U−Pb Geochronology

In cathodoluminescence imagery, zircon grains typically show moderately luminescent irregular/patchy zoning that in some grains overprint faint linear or concentric zoning or surround a small (<20 µm), strongly luminescent core. Fir-tree zoning in some grains is similar to those of zircons that have grown or recrystallized during high-grade metamorphism (Fig. 5e; Corfu et al., 2003). Sixty-six analyses were obtained from homogeneous, patchy/irregular and fir-tree zoned domains. Rims and highly luminescent cores were too narrow or small to be analysed via LA−ICP−MS. Zircon analyses commonly

117


.1 5 20

50

80

95

99.9

1500

1580

1660

1740

Probability

Age (

Ma)

.1 5 20

50

80

95

99.9

1210

1250

1290

1330

Probability

Age (

Ma)

b) Sample 103603D

d) Sample 103617

.1 5 20

50

80

95

99.9

950

1150

1350

1550

Probability

Age (

Ma)

f) Sample 103618

0.14

0.18

0.22

0.26

1.4 1.8 2.2 2.6 3.0

950

1050

11501250

1350

1450a) Sample 103603D

207Pb/235U

20

6P

b/2

38U

Wtd. avg: 1275 ± 11 Ma(95 % conf.) n = 17MSWD = 0.30

0.23

0.27

0.31

0.35

2.6 3.0 3.4 3.8 4.2 4.6 5.0

1400

1500

16001700

1800

c) Sample 103617

Wtd. avg:1666

± 8 Ma(95 % conf.) n = 25MSWD = 0.73

0.18

0.22

0.26

0.30

2.0 2.4 2.8 3.2 3.6 4.0 4.4

1200

1300

1400

15001600

1700e) Sample 103618

Wtd. avg: 1283

± 9 Ma(95 % conf.) n = 22MSWD = 0.93

Figure 7

20

6P

b/2

38U

20

6P

b/2

38U

207Pb/235U

207Pb/235U

Fig. 7. Monazite age data for the Talbot Terrane showing 207Pb/206Pb age weighted averages, concordia and linearised proba-bility diagrams for samples. Black ellipses indicate 100 ± 5 % concordant analyses that form along a straight line in linearised probability density diagrams, and are used to calculate age weighted averages. Light grey ellipses indicate >5 % discordant analyses that are not included in either weighted average calculations or the linearised probability diagrams. Medium grey el-lipses indicate analyses indicate analyses that are within 100 ± 5 % concordancy but do not lie on a straight line in the linearised probability plots (shown as analyses with crosses), and are not included in weighted average calculations.

yielded low 206Pb, 207Pb, 208Pb and 238U cps, and analyses with noisy isotopic signals were not included in calculations (full dataset is provided in Appendix 2). Thirty analyses are displayed in Figure 8g−h. Nineteen analyses are within 100 ± 10 % concordance and yield a 207Pb/206Pb age range between 1433 and 1323 Ma. A 207Pb/206Pb weighted average age for the

above < 10 % discordant analyses of 1377 ± 26 Ma was calculated (n = 19, MSWD = 0.35, 95 % confidence).

118


.1 5 20 50 80 95 99.91220

1260

1300

1340

1380

Probability

Age

(Ma)

.1 5 20 50 80 95 99 99.9

1230

1270

1310

1350

Probability

Age

(Ma)

.1 5 20 50 80 95

99.9

1220

1300

1380

1460

Probability

Age

(Ma)

b) Sample 115638

d) Sample 115669

f) Sample 115866

0.21

0.22

0.23

0.24

0.25

2.4 2.5 2.6 2.7 2.8 2.9 3.0

1260

13001340

1380

a) Sample 115638

Wtd. avg: 1307

± 12 Ma(95 % conf.) n = 16MSWD = 0.87

0.21

0.22

0.23

0.24

0.25

2.4 2.5 2.6 2.7 2.8 2.9

12601300

1340

1380

c) Sample 115669Wtd. avg: 1295

± 11 Ma(95 % conf.) n = 17MSWD = 0.63

0.21

0.22

0.23

0.24

0.25

0.26

2.4 2.6 2.8 3.0

1280

13201360 1400

e) Sample 115866

Wtd. avg: 1341 ± 10 Ma(95 % conf.) n = 30MSWD = 1.13

206 P

b/23

8 U20

6 Pb/

238 U

206 P

b/23

8 U

207Pb/235U

207Pb/235U

207Pb/235U

0.19

0.21

0.23

0.25

1200

1280

1360

1440

<10 % discordant dataMean = 1377

± 26 Ma (95 % conf.) n = 19, MSWD = 0.35

Zircon- Sample 113019

g)

1.8 2.6 3.4 4.2 5.0

.1 5 20 50 80 95 99.9

1180

1260

1340

1420

1500

Probability207Pb/235U

h) Sample 113019

206 P

b/23

8 U

Age

(Ma)

119

Chapter 4 Mesoproterozoic metamorphism in the Rudall ProvinceFig. 8 (previous page), a−f) monazite age data for the Connaughton Terrane showing 207Pb/206Pb age weighted averages, concordia and linearised probability diagrams. See Figure 7 caption for monazite concordia ellipse shading explanation, g−h) zircon age data for sample 113019 showing 207Pb/206Pb age weighted average, concordia and linearised probability diagrams. Black ellipses are 100 ± 10% concordant analyses used in calculation of 207Pb/206Pb age weighted average. Light grey ellipses are analyses are >10% discordant.

5.3 Zircon and garnet trace element characteristics

Representative trace-element chemistry for garnet and zircon grains from sample 113019 is provided in Appendix 2 and chondrite normalised REE patterns are shown in Fig. 9. Trace element abundances in garnet were measured by LA–ICP–MS spot analyses across two garnet grains ~1500 µm in diameter. Both garnet grains contain inclusion-rich cores and inclusion-poor rims. Chondrite-normalized REE patterns for garnet show variable but more enriched and steeper HREE within the cores of garnet (LuN/GdN = 12.64–72.96; LuN = 60–373) relative to garnet rims (LuN/GdN = 1.71–5.07; LuN = 13–34). 100 ± 10% concordant zircon grains have HREE patterns are enriched relative to chondrite and show patterns that vary from shallow to steep (LuN = 24–557; LuN/GdN = 1.66–11.35). Core analysis 06 contains two orders of magnitude higher concentration of Zr, and is considered likely to be contaminated by very fine (~5 µm) inclusion(s) of zircon present in garnet grains (Appendix 2, not plotted in Figure 9). Eu anomalies were not able to be calculated for some garnet analyses due to Sm concentrations below detection limit. However, for analyses where the Eu anomaly was able to be calculated, the garnet 1 core lacks a pronounced Eu anomaly (Eu/Eu* = 1.04), whereas the garnet 1 rim has a negative Eu anomaly (Eu/Eu* = 0.63). For zircon analyses where the Eu anomaly was able to be calculated, zircon has a positive Eu anomaly (Eu/Eu* = 1.18−1.55).

5.4 P–T phase diagram modelling

5.4.1. Sample 103618 (staurolite−biotite-bearing pelite, Talbot Terrane)

The calculated P−T pseudosection for sample 103618 based on the geochemical whole rock analysis is presented in Figure 10a. The peak assemblage for sample 103618 is interpreted as staurolite−biotite−chlorite−plagioclase−quartz−ilmenite−magnetite and

is interpreted to have formed under subsolidus conditions. H2O was set to excess and for simplicity is assumed to have been part of the peak assemblage. The stability field corresponding to the peak P−T assemblage occurs at ~5.5−8.5 kbar, 600−650 °C (70−120 °C kbar-1), which is taken as the best estimate for peak P−T conditions.

5.4.2. Sample 113019 (garnet−diopside bearing amphibolite, Connaughton Terrane)

A P–T pseudosection calculated for sample 113019 is presented in Fig. 10b. The stability field corresponding to the interpreted peak assemblage garnet–diopside–plagioclase–hornblende–quartz–titanite(sphene)−H2O (outlined in bold), occurs at ~8–11 kbar, ~620–650 °C, and corresponds to apparent thermal gradients of ~60−80 °C.kbar-1. The post-peak evolution is interpreted to involve a relative decrease in garnet and diopside abundance, and relative increase in plagioclase and hornblende abundance. Using relative modal proportion trends for garnet, diopside, hornblende and plagioclase, the post-peak evolution is inferred to have involved a decrease in P and T. This P−T evolution is similar to that inferred by Smithies and Bagas (1997).

6. Discussion

6.1 Garnet and zircon chemistry

Trace element analyses from garnet-bearing amphibolite (sample 113019) in the Rudall Province show enriched, positive sloping normalized HREE trends for garnet cores, and typically show enriched, shallowly positive sloping to negatively sloping normalized HREE trends for garnet rims (Fig. 9), suggesting that during the growth of garnet rims, garnet may have been competing with another phase for HREE (cf. Rubatto, 2002). Zircon REE analyses show positive sloping HREE trends, suggesting that zircon grains may have grown at a time where chemical communication with a HREE reservoir

120


occurred (Fig. 9; cf. Rubatto et al., 2013). Titanite can also incorporate Zr and REEs (e.g. Storkey et al., 2005; Hayden et al., 2008), and it is therefore possible that the positive HREE slope in zircon reflects zircon growth while either titanite or garnet was decreasing in abundance. Mid to heavy REE distribution coefficients of zircon/garnet (REEDzir/gt) are close to 1 (Fig. 9), which is similar to empirical REEDzir/gt values obtained where zircon and

garnet are interpreted to have co-existed together (e.g. Whitehouse and Platt, 2003; Taylor et al., 2014). The zircon U–Pb age data from diopside–garnet bearing amphibolite sample 113019 is therefore considered to record the timing of moderate-thermal gradient, medium to high-P metamorphism (weighted average of 1377 ± 26 Ma).

Figure 9

Zircon

0.1

1

10

100

1000

Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Grt core

Grt core-rim transitionGrt rim

Sam

ple/

REE

cho

ndrit

e

Fig. 9. Chondrite normalised garnet and zircon REE data for sample 113019.

P (k

bar)

550 600 650 7002

3

4

5

6

7

8

9

7

SilAnd

KySil

Crd And Bt Ilm Mag Pl (v = 4)

+ Qtz H2O

Crd Kfs Bt Ilm Mag Pl (v = 4)

Bt Chl St Pa IlmMag Pl (v = 3)

Bt Chl St IlmMag Pl (v = 4)

Bt Chl Pa IlmMag Pl (v = 4)

Bt Chl Pa IlmMag Ep Pl

(v = 3)

Bt Chl Pa IlmMag Ep (v = 4)

1

1. Bt Chl Pa Ilm Mag Hem Ep (v = 3)2. Bt Chl Sil Ilm Mag Pl (v = 4)3. Crd Sil Bt Pl Mag (v = 5)4. Crd Bt St Pl Ilm Mag (v = 4)5. Bt Chl Pa Sil Ilm Mag Pl (v = 3)

2

Crd Sil Bt St Pl Ilm Mag (v = 3)

Crd Sil Grt Bt Pl Mag Ilm(v = 3)

3

Grt Ky Bt Mag Pl Ilm (v = 4)

Grt StBt MagPl Ilm (v = 4)

Grt Bt Chl St Pa Ilm Mag Pl (v = 2)

10

4

5

6

7

T °C

8

SiO Al O CaO MgO FeO K O Na O TiO O

Solidus

222322

75.99 8.58 0.49 4.61 5.93 1.23 1.99 0.60 0.609

a) Sample 103618

6. Bt Chl Pa Ms Ilm Mag Pl (v = 3)7. Pa Crd And Bt Ilm Mag Pl (v = 3)8. Bt Chl St Sil Pa Ilm Mag Pl (v = 2) 9. Grt Bt St Pa Ilm Mag Pl (v = 3)10. Grt Bt Chl Pa Ilm Mag Ep Pl (v = 2)11. Sil Bt Chl St Pl Ilm Mag (v = 3)

11

8. Ep Sph Hbl Pl (v = 5)9. Di Ep Sph Hbl Pl (v = 4)10. Di Ep Sph Hbl (v = 5)11. Hbl Ilm Sph Pl (v = 5)12. Di Hbl Ilm Sph Pl (v = 4)13. Grt Di Hbl Pl Ilm Sph (v = 3)14. Grt Di Hbl Sph Rt Pl (v = 3)

15. Di Opx Pl Ilm Mag (v = 4)16. Di Opx Hb Pl Ilm Mag (v = 3)17. Di Hbl Pl Ilm Mag (v = 4)18. Grt Di Ep Sph Hbl (v = 4)19. Grt Di Sph Hb (v = 5)

800600 650 700 7505

6

7

8

9

10

11

12

13

Grt Di Hbl Rt Pl (v = 4)

+ H O + Qtz NCFMASHTO

2

Grt Di Hbl Rt Pl Ilm (v = 3)

Grt Di Hbl Pl Ilm (v = 4)

Di Hb Pl Ilm (v = 5)

Hbl Pl Ilm (v = 6)1

2

3

Grt Bi Hbl Rt(v = 5)Grt Bi Hbl

Rt Ep(v = 4)

4

5

67

89

10

11

12

13

14

Di0.01

Di 0.03

Di 0

.05

FeO Na2O TiO2 O 13.07 2.24 1.34 0.65

T °C

Hbl 0.2

Hbl 0.3Pl 0.12

Pl 0.08

Pl 0.04

Grt 0.02

Grt 0.06

Grt 0.1

1. Hbl Pl Ilm Mag (v = 5)2. Di Opx Hbl Pl Ilm (v = 4)3. Grt Di Opx Hbl Pl Ilm (v = 3) 4. Grt Di Sph Hbl Rt (v = 4)5. Grt Ep Sph Hbl (v = 5)6. Grt Di Sph Hbl Pl (v = 4)7. Ep Sph Hbl (v = 6)

15

16

17

1819

Hbl 0.1

Hbl 0.35

SiO2 Al2O3 CaO MgO

52.68 9.02 12.15 10.17

b) Sample 113019

P (k

bar)

NCKFMASHTO

Fig. 10. P–T pseudosections for a) sample 103618, peak stability field biotite–chlorite–staurolite–plagioclase–ilmenite–mag-netite–quartz–H2O (v = 4) is shown in bold, and b) P–T pseudosection for sample 113019. Peak stability field garnet–di-opside–plagioclase–sphene–hornblende–quartz–H2O (v = 4) is shown in bold. Modal abundance contours are shown for hornblende (Hbl), plagioclase (Pl) and diopside (Di).

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6.2 Timing of regional metamorphism in the Rudall Province

The Rudall Province is interpreted to have undergone multiple phases of deformation during the Paleoproterozoic to late Neoproterozoic (e.g. Smithies and Bagas, 1997; Bagas et al., 2000; Bagas, 2004). The earliest identified metamorphic event, the M1–D1 phase of the Yapungku Orogeny, produced layer parallel schistosity and is interpreted to have developed poorly preserved andalusite bearing assemblages (Hickman and Bagas, 1999). These rare M1 assemblages have not been dated directly, but have been inferred to be c. 1800 Ma, based on a recently reinterpreted intrusive age of the protolith to a banded orthogneiss (c. 1801 Ma; Kirkland et al., 2013) that is interpreted to have intruded pre or early D1, and the c. 1800–1760 Ma ages of post-D1 intrusives of the Kalkan Supersuite (Nelson, 1995; Hickman and Bagas, 1998). Andalusite bearing assemblages could reflect contact metamorphism associated with the intrusion of the Kalkan Supersuite.

The timing of the D2−M2 phase of the Yapungku Orogeny was previously interpreted to be c. 1800–1765 Ma based on intrusive protolith ages of the variably deformed Kalkan Supersuite, which is considered to have intruded throughout the Yapungku Orogeny (e.g. Nelson, 1995, 1996; Hickman and Bagas, 1998; Bagas et al., 2000; Bagas, 2004). The minimum age for the Yapunkgu Orogeny was constrained at 1778 ± 16 Ma using zircon U−Pb age data from an aplite dyke that is inferred to have intruded a syn-D2 serpentinised ultramafic rock (Nelson, 1995; Bagas, 2004). However, Maidment (2014) recognised that aplite dykes in the Rudall Province are variably overprinted by S2 and therefore may only provide a maximum age constraint for the D2 Yapungku Orogeny. In this study, zircon and in situ monazite U–Pb age data were collected from samples from the Talbot and Connaughton Terranes in order to provide further direct age constraints on metasedimentary-derived rocks. The samples have previously been inferred to contain: 1) S1 inclusion trails in garnet (sample 113019), 2) an S2 fabric (samples 103603D, 103617, 103618, 113019, 115638, 115669); and 3)

inferred to be late to post S2 (sample 115866; garnet in sample 115638; sillimanite in sample 115669; results summarised in Table 3; structural characteristics from Smithies and Bagas, 1997; Bagas and Smithies, 1998; Clarke pers. comm). Metamorphic zircon age data combined with zircon and garnet trace element chemistry from sample 113019 is suggestive of moderate thermal gradient, high grade metamorphism occurring at c. 1377 Ma. The zircon U–Pb age data from sample 113019, although imprecise does not show more than one age population. This may indicate that if the inclusion trails in garnet do indeed represent an earlier fabric than the main S2 fabric of the rock (e.g. Bagas and Smithies, 1998), both fabrics developed in a shorter time span than the resolution of the LA–ICP–MS data, or the analysed zircon does not record or preserve the development of both fabrics.

A number of workers have argued that monazite growth or recrystallisation can occur under a variety of conditions during subsolidus metamorphism (e.g. Pyle and Spear, 2003; Kohn and Malloy, 2004; Rubatto et al., 2006; Corrie and Kohn, 2008; Spear and Pyle, 2010; Gasser et al., 2012), high-grade metamorphism and/or along the retrograde path during high-grade metamorphism in rocks that have melted (e.g. Rubatto, 2002; Rubatto et al., 2006; Kelsey et al., 2007; Kelsey et al., 2008; Gasser et al., 2012; Korhonen et al., 2013; Rubatto et al., 2013; Clark et al., 2014; Yakymchuk and Brown, 2014), and diagenesis, hydrothermal mineralisation or fluid alteration/flow (e.g. Williams et al., 2011; Muhling et al., 2012; Halpin et al., 2014). Monazite U–Pb analyses from samples from the Connaughton Terrane together yield age populations between c. 1340−1295 Ma. This age range is somewhat younger than an imprecise U−Pb age weighted average of c. 1377 ± 26 Ma from metamorphic zircons obtained from a garnet-bearing amphibolite (sample 113019). Whereas as an absence of leucosomes in sample 115669 (quartz-rich, kyanite−sillimanite−quartz metasediment) may suggest that partial melting was limited or did not occur, samples 115638 and 115866 contain leucosomes that are interpreted as a record of partial melting. For rocks that have melted for a typical metapelitic or greywacke composition, it has

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been suggested based on thermobarometric modelling that monazite is likely to record an age along the retrograde metamorphic P–T path (Kelsey et al., 2008; Yakymchuk and Brown, 2014). The monazite grains in these samples are interpreted to have grown on the high-T retrograde part of the P–T path and may record the crossing of the elevated solidus at c. 1341–1307 Ma (e.g. Korhonen et al., 2013). Sample 115669 (kyanite−sillimanite bearing quartzite) is younger outside of uncertainty of sample 115866. As some of the kyanite grains appear to be partially recrystallised parallel to the foliation, it is possible that the high strain foliation development in sample 115669 occurred locally (e.g. close to shear zones) and/or that tectonism during the Mesoproterozoic may be diachronous or involve multiple phases (discussed below).

In the Talbot Terrane, two monazite U–Pb age brackets are obvious in the dataset from this study, at c. 1665 Ma and c. 1285–1275 Ma. The c. 1665 Ma age population was obtained from a single sample (sample 130617; staurolite-bearing schist), whereas the c. 1285–1275 Ma age populations were obtained from a staurolite-bearing schist (sample 103618), which is interpreted to contain a S−C fabric defined by chlorite, biotite and staurolite, and a retrogressed kyanite-bearing metapelite (sample 103603D). Some monazite grains in all three samples occur at silicate mineral grain boundaries, in contact with retrograde chlorite or sericite or contain very fine grained inclusions. It is therefore possible that some grains may have grown or recrystallised after peak metamorphism (e.g. during retrogression in sample kyanite bearing sample 103603D). However, the U–Pb ages obtained from the above monazite grains (i.e. silicate grain boundaries) are instinguishable from the remainder of monazite ages from each sample and from the Talbot Terrane are therefore considered to comprise single population in each sample.

The results do not support the contention that the regional peak metamorphism in the Rudall Province was synchronous with the emplacement of the c. 1800−1760 Ma Kalkan Supersuite. Instead, the age data suggests that the Rudall Province underwent its main

episodes of metamorphism and associated deformation well after the emplacement of the Kalkan Supersuite in the Mesoproterozoic. We consider that the c. 1665 Ma monazite age population obtained from a single metapelite in the Talbot Terrane possibly records a poorly preserved tectonothermal event that reached amphibolite facies in the Talbot Terrane. However, it however remains unclear whether the rocks in the Connaughton Terrane also experienced this event.

6.3 Characterising physical and thermal conditions of metamorphism in the Rudall Province

P–T pseudosections were calculated for staurolite-bearing sample 103618 from the Talbot Terrane, and garnet–diopside bearing amphibolite sample 113019 from the Connaughton Terrane to investigate the physical conditions of metamorphism. Existing metamorphic work from the Rudall Province has focused on the elucidation of the Yapungku Orogeny (D2–M2) in both the Talbot and Connaughton Terranes assuming the age is c. 1800−1760 Ma (Clarke, 1991; Smithies and Bagas, 1997). Rocks in the Talbot and Connaughton Terrane have been interpreted to have experienced moderate-thermal gradient conditions, followed by a steeply decompressive post-peak P–T evolution during the Yapungku Orogeny (Smithies and Bagas, 1997).

In this study, amphibolite sample 113019 of the Connaughton Terrane is interpreted to have reached peak P−T conditions of ~8–11 kbar, 620–650 °C (apparent thermal gradients of ~60−80 °C kbar-1), followed by a clockwise post-peak evolution. The inferred clockwise post-peak evolution for amphibolite sample is similar to the steeply decompressive post peak P–T evolution inferred by Smithies and Bagas (1997), yet the peak temperature obtained in this study is somewhat lower than those obtained by Smithies and Bagas (1997) for the same garnet-bearing amphibolite lithology (up to ~12 kbar, ~770 °C in Smithies and Bagas, 1997). This may be a result of a difference in methodology (conventional thermobarometry compared to P–T pseudosection, see Powell

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and Holland, 2008). It is possible that the discrepancy in temperature estimates may be partly related to the modelled stability of ilmenite and titanite in the pseudosection for sample 113019. In Fig. 10b, the stability field for the peak assemblage is bounded at the high-T side by the introduction of ilmenite stability, which is not present in the sample. In the adjacent higher-T stability field containing ilmenite (field 13), modelled ilmenite is present in small modal proportions (<0.02). It is possible that the modelled stability of titanite and ilmenite in P–T space may be sensitive to small differences in the modelled bulk rock composition compared to the true bulk composition (e.g. small differences in Fe3+ or Ti). As a result, we consider Smithies and Bagas (1997) temperature estimates of ~770 °C as the upper limit for the estimated temperature experienced by the garnet-bearing amphibolite during the D2 Yapungku Orogeny. P−T constraints from staurolite-bearing sample 103618 from the Talbot Terrane in this study implies a moderate to high thermal-gradient regime during Mesoproterozoic metamorphism (~75−110 °C kbar-1), and is comparable to qualitative P–T estimates obtained by Clarke (1991). Due to a lack of reaction microstructures in sample 103618 (Talbot Terrane), the post-peak evolution could not be constrained.

Smithies and Bagas (1997) describe a ~400 m2 garnet−orthopyroxene bearing outcrop (‘charnockite’ unit in Bagas and Smithies, 1998), from which they obtained very high-thermal gradient P–T conditions (~2–4 kbar, ~800 ºC), and interpreted the unit to have been metamorphosed after D2–M2, resulting from possible higher crustal level, post- D2 granitoids. Garnet–orthopyroxene sample 115866 comes from the same locality and is petrographically identical to the garnet-orthopyroxene sample of Smithies and Bagas (1997). The inferred P−T evolution of the garnet–orthopyroxene bearing rock (Smithies and Bagas, 1997) contrasts with: a) the constrained lower-thermal gradient regime calculated for the mafic-amphibolites from the Connaughton Terrane, and b) the decompressional post-peak P−T evolution inferred for M2−D2 (Smithies and Bagas, 1997; this study). Within the Connaughton Terrane,

a post-D2 garnet microgneiss and pegmatite yield U−Pb zircon crystallisation ages of c. 1222 and c. 1291 Ma respectively (Nelson, 1995, 1996), with a zircon analysis of c. 1200 Ma from the garnet microgneiss recently reinterpreted as metamorphic (Kirkland et al., 2013). These constraints suggest that late partial melts probably accompanied Mesoproterozoic metamorphism in the Rudall Province. It is possible that the orthopyroxene-garnet gneiss underwent metamorphism proximal and related to as yet unidentified c. 1340 Ma magmatism.

6.4 Implications for the assembly of the NAC and WAC

The Yapungku Orogeny has been interpreted to reflect the collision of the NAC and WAC, which has been used as a basic element of most models that describe the assembly and development of Proterozoic Australia (e.g. Betts and Giles, 2006; Cawood and Korsch, 2008; Payne et al., 2009). The metamorphic record of the Yapungku Orogeny has been interpreted to record thrust stacking and crustal thickening, leading to amphibolite and granulite facies metamorphism (e.g. Smithies and Bagas, 1997; Bagas, 2004).

Mesoproterozoic monazite U–Pb age populations obtained in this study range from c. 1340–1275 Ma, and zircon U–Pb age data from amphibolite sample 113019 yielded an age population of c.1377 Ma. We consider that both the moderate- to high thermal gradient Yapungku Orogeny (M2–D2) and localised high-thermal gradient metamorphism in the Rudall Province are most likely to be Mesoproterozoic-aged, based on the Mesoproterozoic-aged monazite and zircon obtained in this study. Together the zircon and monazite ages span ~100 M.y. (Fig. 11; Table 3). It is possible that this age range reflects: a) monazite and zircon from moderate thermal gradient rocks growing along different stages of the P–T evolution (e.g. possibly zircon growth on the prograde path, monazite recrystallisation in sample 103603D and 103618 post-dating peak metamorphism), b) diachroneity in metamorphism/deformation between terranes and some magmatically-driven metamorphism at least on a local scale,

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Meso to Neoproterozoic sedimentary rocksPhanerozoic and Fault

Thrust

Monazite sample locality

122°00’ 123°00’

22°3

0’23

°00’

0 20km

N

103618

1156381307 ± 12 Ma

1156691295 ± 11 Ma

1158661341 ± 10 Ma

Tabletop Terrane

Connaughton Terrane

Tabot TerraneZircon sample locality

103603D1275 ± 11 Ma

103617:1666 ± 8 Ma

1283 ± 9 Ma~5.5−8.5 kbar, 600−650 °C

1130191377 ± 26 Ma~8–11 kbar, minimum620–650 °C

Fig. 11. Simplified map of the Rudall Province showing spatial distribution of zircon and monazite age data and P−T con-straints from this study.

Table 3. Summary of U–Pb monazite and zircon age data, and P–T estimates obtained in this study

Terrane SampleEasting (m

E)Northing (m

N) Mineralogy Fabric^Monazite Age (Ma, 95 % conf.) P–T estimates (kbar, °C)

Talbot 103603D 404733 7511111 Ky-Pl-Rt-Ilm (+Chl-Ms-Ser) bearing metapelite S2 1275 ± 11

Talbot 103617 405958 7511738 St-Bt-Pl-Ilm-Mag-Qtz, (+Chl) metapelite S2 1666 ± 8

Talbot 103618 405958 7511738 St-Bt-Pl-Ilm-Qtz-Chl-Mag metapelite S2 1283 ± 9 ~5.5−8.5, 600−650

Connaughton 115638 466506 7489683 Grt-Sil-Pl-Kfs-Qtz-Rt-Ilm metasedimentS2, late-post S2? 1307 ± 12

Connaughton 115669 469624 7485385 Ky-Sil-Qtz-Ilm-Mag (+Ms, Ctd) metasedimentS2, sillimanite late-post S2? 1295 ± 11

Connaughton 115866 485181 7472585 Opx-Grt-Mag-Ilm-Pl-Kfs-Qtz (+ Bt-Chl) gneiss post-S2 1341 ± 10

Connaughton 113019 457200 7467600 Di-Grt-Pl-Qtz-Hb-Ttn mafic amphibolite S1(?)/S2 1377 ± 26~8–11, 620–650, decreasing P–T post-peak evolution

^ From Smithies and Bagas (1997); Bagas and Smithies (1998) or Clarke (pers. comm)

Co-ordinates in UTM, GDA 94, Zone 51K, approximate from aerial photography

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c) a long-lived metamorphic/tectonic event, or d) different metamorphic events. Of these alternatives, we tentatively suggest that the range of metamorphic ages is best explained through a stage-wise development of the Rudall Province that involved the accretion of ‘ribbons’ that were previously derived from the margin of the WAC (cf. Kirkland et al., 2013). In the above proposed tectonic scenario, both moderate thermal gradient and high thermal gradient metamorphic conditions could be attained via accretion (or reattachment) and subsequent outboard migration of subduction, placing accreted the ribbon(s) in a back-arc/arc setting. In this proposed scenario, the final closure of the system probably occurred at c. 1300−1280 Ma, or later, marked by the collision of the NAC with ribbons that accreted with the WAC. In this model, the suture between the NAC and accretionary edge to the WAC would lie to the northeast of the Rudall Province, consistent with Kirkland et al. (2013) who showed that the rocks of the Rudall Province have affinities to the WAC.

In the step-wise Mesoproterozoic accretion hypothesis outlined previously, the Yapungku Orogeny is not a single event. Instead, we envisage it to be an accretionary system marked by episodes of thermally contrasting metamorphism that record either the accretion of ribbons or inter-accretionary extension during the Mesoproterozoic. It is not clear to what extent the Rudall Province records the complete amalgamation of the WAC and NAC. The arrangement of rock units and Mesoproterozoic age domains within the Rudall Province have been complicated by later reworking, most notably during the Miles Orogeny and the late Neoproterozoic to Cambrian Paterson Orogeny, the latter involving a substantial amount of strike-slip movement (e.g. Hickman and Bagas, 1999; Bagas, 2004).

The Mesoproterozoic-aged medium-P metamorphism in the Rudall Province broadly coincides with the timing of major phases of tectonism in the Musgrave and Albany Fraser Orogens (e.g. Myers et al., 1996; Giles et al., 2004; Betts and Giles, 2006; Cawood and Korsch, 2008; Wade et al., 2008; Aitken and Betts, 2009; Spaggiari et al., 2009; Smithies et

al., 2011). Stage I of the Albany Fraser Orogeny (c. 1340–1260 Ma) has been interpreted to be a response to the collision of the WAC with the SAC/Mawson Continent (e.g. Clark et al., 2000) and/or alternatively reflect the closure of a marginal ocean basin and accretion of the Loongana Magmatic Arc to the WAC, prior to the final convergence of the WAC and SAC/Mawson Continent (Spaggiari et al., 2014). In the western Musgrave Province, the tectonic setting of the c. 1345–1292 Ma Mount West Orogeny remains uncertain. However, the Mount West Orogeny involved the emplacement of metaluminous, calc to calc-alkaline granitoids of the Wankanki Supersuite, which are geochemically similar to those that occur in modern day continental-arc settings (Smithies et al., 2010; Smithies et al., 2011).

The temporal similarities of Mesoproterozoic tectonism in the Albany-Fraser Orogen, Musgrave and Rudall Provinces and the spatial occurrence of these three provinces/orogens either on the margin of, or between, older Archean–Paleoproterozoic cratonic elements suggests that Mesoproterozoic tectonism may reflect the protracted amalgamation of the WAC, NAC and SAC between c. 1375 and 1150 Ma (e.g. Myers et al., 1996; Smits et al., 2014).

6.5 Implications for supercontinent Nuna re-constructions

Globally, the c. 1400−1300 Ma time-line corresponds to the interpreted initiation of the breakup of supercontinent Nuna (Pis-arevsky et al., 2014a; Pisarevsky et al., 2014b). An implication for the proposed Mesopro-terozoic assembly of Proterozoic Australia is that the need for the components of Australia to be connected during supercontinent Nuna is no longer required. Recent paleomagnetic constraints from the WAC indicate Australia and Laurentia were widely separated by c. 1210 Ma (Pisarevsky et al., 2014b). We sug-gest that following the accretion of the NAC to Laurentia at c. 1550−1500 Ma in either a modified SWEAT (South West U.S.-East Ant-arctic; Moores, 1991) or AUSWUS (Austra-lia-Western U.S.; Karlstrom et al., 1999) style

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configuration (Fig. 12a), the NAC migrated as a ribbon away from Laurentia at c. 1450 Ma (e.g. Medig et al., 2014) and collided with the WAC at c. 1300 Ma (Fig. 12b). In Laurentia, removal of the NAC ribbon coincided with the formation of the rift Belt Superbasin system. The Mawson Continent (SAC and east Ant-arctica) collided with the NAC−WAC between c. 1250−1150 Ma (e.g. Smits et al., 2014). If correct, Laurentia and Australia have been disconnected since the late Mesoproterozoic and a Neoproterozoic SWEAT connection is not likely. In our preferred model, a Meso-proterozoic AUSWUS-style connection by c. 1250 Ma (Fig. 12c) allows the transcontinen-tal Musgrave-Albany Fraser orogen (Smits et al., 2014) to directly connect with the Gren-villian super-orogen (cf. Van Kranendonk and Kirkland, 2013).

7. Conclusions

The age of the Yapungku Orogeny in the Rudall Province has long been interpreted to be Paleoproterozoic. However, monazite age data from metasedimentary rocks of the Connaughton and Talbot Terrane indicate the Yapungku Orogeny (D2−M2) is Mesoproterozoic-aged. We propose that medium-P metamorphism with moderate to high-thermal gradients reflects

the amalgamation of the WAC and NAC during the Mesoproterozoic rather than Paleoproterozoic via a stage-wise evolution. If this is correct, a Mesoproterozoic timeline for the amalgamation of the major cratonic elements of Proterozoic Australia is supported, which feasibly occurred during the breakup stages of supercontinent Nuna.

ReferencesAitken, A.R.A., Betts, P.G., 2009. Constraints on the Proterozoic supercontinent cycle from the structural evolution of the south-central Musgrave Province, central Australia. Precambrian Research 168, 284-300.Bagas, L., 2004. Proterozoic evolution and tectonic setting of the northwest Paterson Orogen, Western Australia. Precam brian Research 128, 475-496.Bagas, L., Smithies, R.H., 1998. Geology of the Connaughton 1:100 000 Sheet, 1:100 000 Geological Series Explanatory Notes. Geological Survey of Western Australia, Perth, p. 38.Bagas, L., Williams, I.R., Hickman, A.H., 2000. Rudall, 1:250 000 Geological Series Explanatory Notes, 2 ed. Western Australia Geological Survey, Perth, p. 50.Betts, P.G., Giles, D., 2006. The 1800-1100 Ma tectonic evolution of Australia. Precambrian Research 144, 92-125.Betts, P.G., Giles, D., Lister, G.S., Frick, L.R., 2002. Evolution of the Australian Lithosphere. Australian Journal of Earth Sciences 49, 661-695.Betts, P.G., Giles, D., Mark, G., Lister, G.S., Goleby, B.R., Ailleres, L., 2006. Synthesis of the proterozoic evolution of the Mt Isa Inlier. Australian Journal of Earth Sciences 53, 187- 211.Brown, M., 2007. Metamorphic conditions in orogenic belts: a re cord of secular change. International Geology Review 49, 193-234.Camacho, A., McDougall, I., 2000. Intracratonic, strike-slip parti tioned transpression and the formation and exhumation of eclogite facies rocks: An example from the Musgrave Block, central Australia. Tectonics 19, 978-996.Cawood, P.A., Korsch, R.J., 2008. Assembling Australia: Proterozo

Fig. 12. Simplified schematic tectonic model of Proterozoic Australia and Laurentia at c. 1600−1550 Ma− arc extending from Laurentia to the WAC. Also shown are possible modified AUSWUS (NAC1; after Karlstrom et al., 1999) and SWEAT-like configurations (NAC2; after Moores, 1991). B: 1400−1300 Ma− NAC extracted from western Laurentia at around 1450 Ma, associated with development of Belt Supergroup rift system, docking of the WAC to NAC reflected by the Yapungku Oroge-ny in the Rudall Province (star), and commencement of Stage I of the Albany Fraser Orogeny (AFO) at c. 1330 Ma in modi-fied AUSWUS style configuration. C: 1250−1150 Ma− final convergence of major cratonic elements of Proterozoic Australia (reconstruction following Li and Evans, 2011). BSG = Belt Supergroup and equivalents (Medig et al., 2014), L = Laurentia, E ANT = E Antarctica, SAC = South Australian Craton, NAC = North Australian Craton, WAC = West Australian Craton.

B 1400-1300 Ma C 1250-1150 Ma

A

Fig3_Anderson.pdf

Mawson E ANT

SAC

WAC

L Laurentia

Mawson

Mawson

SAC

L

SAC

E ANT

NAC 2

MI LNAC 1

WAC-NACamalgamation

Nuna Breakup

1600-1550 Ma

BSG

Mawson

E ANT

NACWAC

SAC

L

NAC NAC

SAC-(WAC-NAC)amalgamation

WAC

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Supporting Information

Appendix 1: Mineral chemistryGarnet In sample 115866, fine-grained garnet grains located in the matrix typically have XAlm values that increase from core to rim (~0.54–0.62), XPy values that decrease from core to rim (~0.38–0.32), XGrs values of ~0.02 and XSpss values of ~0.05. Garnet occurring as coronas on magnetite or ilmenite, or within quartz-garnet intergrowths have XAlm values of 0.57–0.64, XPy values of ~0.27–0.35, XGrs values of ~0.02 and XSpss values of 0.05–0.06.PyroxeneOrthopyroxene is present in sample 115866 and has XMg values of ~0.59−0.60, with Al2O3 content of ~9.70−10.1 wt. %. Orthopyroxene has 4.05–4.35 wt. % Fe2O3 using the stoichiometric calculation method of Droop (1987). Calculated y(opx)1 values are 0.18−0.18 without Fe2O3 recalculation and 0.15−0.16 recalculated with Fe2O3, (y(opx)1 = CSi, total (opx) + CAl,total (opx – 2), where Ci is cations of i). Orthopyroxene has 4.05–4.35 wt.% Fe2O3.FeldsparAlkali feldspar in sample 115866 has XOr values of ~0.66–0.84 and XAn values of ~0.01–0.07.In sample 103617 and 103618, plagioclase is albite, with XNa (= Na/(Na+Ca)) values of 0.98−0.99 and 0.96−0.97 respectively. Plagioclase in sample 115866 has XAn (=Ca/(Na+Ca+K)) values of ~0.43–0.44 and XOr values of ~0.01 (=K/(Na+Ca+K)).StauroliteIn sample 103617, staurolite has XMg values of 0.19−0.22 and ZnO wt. % values of 0.02−0.13. In sample 103618, staurolite has XMg values of 0.18−0.20 and ZnO wt. % values of 0.03−0.12.BiotiteIn sample 115866, biotite has XMg values of 0.66−0.78 and 2.0−4.5 wt. % TiO2. Biotite in sample 103617 has XMg values of 0.59−0.60 and wt. % TiO2 content of 1.12−1.33. Biotite in sample 103618 has XMg values of ~0.56 and wt. % TiO2 content of 1.16−1.42.

ChloriteChlorite has XMg values of 0.63−0.64 in sample 103617 and XMg values of 0.59−0.61 in 103618.IlmeniteIlmenite in sample 115866 has 1.87–4.47 wt. % Fe2O3 calculated using the method of Droop (1987)x, 0.12−0.70 wt. % MgO and 1.74−2.91 wt. % MnO.Magnetite-SpinelIn sample 115866, magnetite usually occurs with spinel and/or corundum and has Al2O3 wt. % content of 0.19−0.26. Spinel occurs with magnetite and/or corundum and has ZnO content of ~9.2 wt. %, MgO content of ~3.7 wt. % and Cr2O3 values of 0.10 wt. %. In sample 103617, magnetite has Al2O3 wt. % content of 0.08−0.15, and in sample 103618, magnetite has Al2O3 wt. % content of 0.46−0.47.

131


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0.07

80.

0011

20.

1659

10.

0022

91.

7823

10.

0293

70.

8376

107

86.2

811

46.8

28.3

898

9.5

12.6

410

3910

.72

055

559

4396

4451

05M

120.

0827

10.

0011

30.

2281

80.

0038

2.60

059

0.04

768

0.90

8325

8310

4.96

1262

.426

.32

1325

19.9

613

00.8

13.4

50

9723

382

4569

5816

M13

-20.

0829

40.

0010

90.

2206

80.

0029

62.

5226

80.

0385

30.

8781

9688

101.

4012

67.7

25.3

512

85.5

15.6

412

78.6

11.1

19

1078

4990

9563

9376

†Disc

arde

d du

e to

noi

sy is

otop

ic sig

nal o

r bla

sted

thro

ugh

grai

nAl

l indi

vidua

l iso

topi

c abu

ndan

cesa

re in

cps

132


Appe

ndix

2. U

-Pb

isoto

pic

age

data

for m

onaz

ite a

naly

ses

Sam

ple

1036

17

Spot

207 Pb

/206 Pb

1 σ

206 Pb

/238 U

1 σ

207 Pb

/235 U

1 σ

rho

Conc

. (%

)20

7 Pb/20

6 Pb a

ge1

σ20

6 Pb/23

8 U a

ge1

σ20

7 Pb/23

5 U a

ge1

σ20

4 Pb20

6 Pb20

7 Pb23

8 Pb

M02

0.08

833

0.00

107

0.25

912

0.00

367

3.15

515

0.04

810.

9290

5209

106.

8913

89.6

23.0

314

85.3

18.7

914

46.3

11.7

530

1762

9115

868

9474

86M

030.

0991

0.00

119

0.29

852

0.00

415

4.07

870.

0607

80.

9329

0137

104.

7716

07.3

22.2

616

8420

.61

1650

.112

.15

1595

639

9668

4369

79M

050.

1018

40.

0012

40.

2848

50.

0040

73.

9996

30.

0613

10.

9321

0897

97.4

516

5822

.46

1615

.720

.41

1634

.112

.45

044

006

4561

2157

51M

09A

0.10

081

0.00

121

0.29

228

0.00

414.

0622

30.

0606

70.

9392

3717

100.

8516

3922

.03

1652

.920

.45

1646

.812

.17

055

744

5739

2623

09M

09B

0.10

144

0.00

117

0.29

146

0.00

408

4.07

596

0.05

995

0.95

1747

999

.89

1650

.621

.26

1648

.820

.36

1649

.511

.99

179

107

8174

3744

04M

09C

0.09

736

0.00

107

0.29

640.

0041

53.

9781

50.

0574

0.97

0374

0210

6.31

1574

.120

.47

1673

.420

.65

1629

.711

.71

1316

7945

1667

578

7037

M10

0.09

962

0.00

107

0.29

222

0.00

414.

0115

90.

0573

50.

9814

2482

102.

2016

1719

.85

1652

.620

.47

1636

.511

.62

913

1794

1334

962

9009

M10

0.10

170.

0012

10.

302

0.00

434.

2339

20.

0638

90.

9435

638

102.

7716

55.4

21.8

817

01.2

21.2

816

80.6

12.3

914

3600

537

3516

6461

M13

0.10

278

0.00

115

0.29

627

0.00

417

4.19

771

0.06

124

0.96

4774

0899

.87

1675

20.5

216

72.8

20.7

216

73.6

11.9

629

1666

5817

457

7834

17M

140.

1003

10.

0010

90.

3003

20.

0042

24.

1513

60.

0596

90.

9772

755

103.

8716

29.8

20.0

216

92.9

20.9

216

64.5

11.7

60

9638

498

0544

7326

M14

0.10

187

0.00

117

0.27

578

0.00

391

3.87

293

0.05

750.

9549

6135

94.6

716

58.5

21.0

515

70.1

19.7

816

08.1

11.9

83

7819

081

2339

7418

M15

0.10

132

0.00

112

0.29

760.

0041

94.

1550

70.

0603

40.

9695

1411

101.

8916

48.3

20.3

916

79.4

20.8

316

65.2

11.8

914

6513

666

9630

5053

M16

0.09

803

0.00

115

0.31

761

0.00

449

4.29

185

0.06

444

0.94

1545

2111

2.04

1587

21.7

917

78.1

21.9

816

91.8

12.3

613

1300

0712

973

5709

73M

20A

0.10

350.

0012

40.

2996

0.00

421

4.27

554

0.06

412

0.93

6996

0210

0.08

1687

.921

.99

1689

.320

.87

1688

.712

.34

374

146

7838

3411

14M

20B

0.10

287

0.00

119

0.29

920.

0042

44.

2435

90.

0633

90.

9486

7386

100.

6416

76.5

21.3

116

87.3

21.0

116

82.5

12.2

712

6345

466

0829

5997

M21

0.10

539

0.00

137

0.28

874

0.00

407

4.19

573

0.06

598

0.89

6360

4495

.01

1721

.123

.75

1635

.220

.35

1673

.212

.89

1610

2977

1103

948

9332

M22

0.09

911

0.00

113

0.29

538

0.00

414

4.03

632

0.05

931

0.95

3843

0510

3.79

1607

.421

.02

1668

.420

.61

1641

.511

.96

922

1001

2220

910

3872

1M

240.

0943

50.

0011

30.

2710

10.

0037

83.

5255

90.

0528

20.

9309

7902

102.

0315

15.2

22.4

315

45.9

19.1

715

3311

.85

826

5715

2554

713

4754

0M

250.

1030

60.

0011

70.

2984

60.

0041

84.

2387

30.

0619

20.

9587

2699

100.

2216

8020

.75

1683

.720

.77

1681

.612

1189

373

9346

4145

88M

25A

0.10

350.

0012

0.30

156

0.00

426

4.30

347

0.06

416

0.94

7524

1510

0.66

1687

.921

.18

1699

.121

.12

1694

12.2

80

8568

189

8239

6832

M25

B0.

1024

0.00

117

0.29

424

0.00

417

4.15

431

0.06

184

0.95

2058

7899

.68

1668

.121

.04

1662

.720

.76

1665

.112

.18

1215

6692

1626

674

6395

M26

0.10

227

0.00

112

0.29

848

0.00

424.

2066

40.

0610

90.

9689

4534

101.

0816

65.8

20.2

116

83.8

20.8

516

75.3

11.9

116

1196

6612

375

5594

38M

260.

1039

0.00

122

0.29

821

0.00

423

4.27

215

0.06

420.

9439

0792

99.2

616

9521

.44

1682

.420

.99

1688

12.3

60

9291

097

9343

5863

M27

0.10

402

0.00

117

0.31

149

0.00

444.

4650

30.

0654

70.

9633

6443

103.

0116

9720

.52

1748

21.6

117

24.5

12.1

66

7506

778

9933

6333

M28

†0.

0866

50.

0011

70.

2824

90.

0041

3.37

246

0.05

186

0.94

3832

8211

8.56

1352

.825

.83

1603

.920

.614

9812

.04

018

6639

1917

592

1340

M29

0.10

265

0.00

147

0.31

50.

0044

64.

4581

40.

0747

30.

8446

6213

105.

5416

72.6

26.2

317

65.3

21.8

517

23.2

13.9

2151

3981

5328

422

3739

3M

290.

1032

90.

0011

60.

2933

60.

0041

44.

1758

40.

0614

70.

9586

9416

98.4

716

84.1

20.5

416

58.3

20.6

516

69.3

12.0

61

1887

0319

672

9004

03M

30†

0.09

957

0.00

141

0.29

234

0.00

424.

0093

10.

0673

50.

8552

510

2.30

1616

.126

.16

1653

.220

.94

1636

.113

.65

022

5107

2262

310

7040

7M

310.

1030

60.

0012

50.

3008

20.

0042

74.

2746

20.

0655

70.

9253

6591

100.

9216

8022

.31

1695

.421

.15

1688

.512

.62

078

296

8158

3631

43M

31†

0.11

059

0.00

150.

2912

40.

0041

54.

4372

70.

072

0.87

8173

7191

.08

1809

.124

.41

1647

.720

.71

1719

.313

.45

152

1367

4115

311

6490

41M

330.

1007

50.

0012

20.

3010

30.

0042

44.

1794

90.

0630

80.

9332

2783

103.

5716

37.9

22.3

216

96.4

21.0

116

7012

.37

068

391

7022

3136

01M

340.

102

0.00

124

0.30

359

0.00

427

4.26

710.

0644

60.

9310

7128

102.

9116

60.8

22.2

817

09.1

21.1

316

8712

.43

061

841

6411

2808

77M

350.

1019

10.

0011

60.

2976

70.

0042

4.18

074

0.06

161

0.95

7450

1510

1.24

1659

.320

.97

1679

.820

.85

1670

.312

.07

859

158

6113

2765

23M

370.

1025

90.

0013

0.29

599

0.00

417

4.18

449

0.06

461

0.91

2434

7399

.99

1671

.523

.19

1671

.420

.77

1671

12.6

57

1034

9710

850

4816

17M

38A

0.10

174

0.00

122

0.30

973

0.00

436

4.34

289

0.06

527

0.93

6630

810

5.02

1656

.222

.04

1739

.421

.44

1701

.512

.417

1038

4610

776

4634

86M

39A

0.10

225

0.00

132

0.30

20.

0042

84.

2555

90.

0666

90.

9043

4864

102.

1516

65.4

23.7

817

01.2

21.1

716

84.8

12.8

89

7124

674

3932

4946

M39

B0.

1012

70.

0012

60.

3055

20.

0043

14.

2639

80.

0653

90.

9199

0175

104.

3116

47.6

22.9

717

18.6

21.2

716

86.4

12.6

132

5667

758

4825

5532

M39

C0.

1013

30.

0013

90.

3107

0.00

445

4.33

852

0.07

050.

8813

9634

105.

8016

48.6

25.2

317

44.2

21.8

917

00.7

13.4

10

3928

640

6817

4482

133


Appe

ndix

2. U

-Pb

isoto

pic

age

data

for m

onaz

ite a

naly

ses

Sam

ple

1036

18

Spot

207 Pb

/206 Pb

1 σ

206 Pb

/238 U

1 σ

207 Pb

/235 U

1 σ

rho

Conc

. (%

)20

7 Pb/20

6 Pb

age

1 σ

206 Pb

/238 U

ag

e1

σ20

7 Pb/23

5 U

age

1 σ

204 Pb

206 Pb

207 Pb

238 Pb

Sess

ion

M05

†0.

0816

10.

0011

20.

2204

0.00

322

2.47

859

0.04

087

0.88

6022

103.

8712

36.2

26.7

912

8417

1265

.811

.93

098

269

8371

6312

421

M01

0.08

345

0.00

097

0.23

575

0.00

335

2.71

139

0.04

033

0.95

5338

106.

6412

79.5

22.5

1364

.517

.48

1331

.611

.03

914

1522

1216

984

2220

1M

060.

0833

30.

0009

30.

2385

20.

0033

62.

7400

70.

0398

30.

9690

9410

8.02

1276

.621

.66

1379

17.5

1339

.410

.81

018

9990

1626

611

1281

81

M04

†0.

0834

80.

0011

80.

2213

60.

0032

42.

5463

70.

0427

10.

8726

4510

0.70

1280

.227

.27

1289

.117

.112

85.4

12.2

314

9604

782

8161

4151

1M

03A

0.08

274

0.00

092

0.21

816

0.00

308

2.48

843

0.03

613

0.97

2373

100.

7312

6321

.46

1272

.216

.29

1268

.710

.52

088

150

7504

5643

511

M03

B0.

0836

0.00

092

0.21

846

0.00

308

2.51

781

0.03

643

0.97

4412

99.2

812

8321

.41

1273

.716

.312

77.2

10.5

10

8657

074

3255

3906

1M

070.

0845

50.

001

0.21

90.

0031

2.55

253

0.03

837

0.94

1665

97.8

213

05.1

22.9

212

76.6

16.4

1287

.210

.97

1316

7333

1454

910

6628

41

M09

A0.

0825

40.

0009

40.

2153

10.

0030

52.

4501

90.

0361

50.

9601

2499

.90

1258

.421

.96

1257

.116

.19

1257

.510

.64

986

028

7301

5598

081

M09

B0.

0823

10.

0009

30.

2151

30.

0030

52.

4414

70.

0359

40.

9631

0210

0.25

1253

21.8

212

56.1

16.1

712

54.9

10.6

010

1262

8564

6596

471

M10

0.08

459

0.00

110.

2316

0.00

332

2.70

075

0.04

277

0.90

5210

2.82

1306

.124

.99

1342

.917

.35

1328

.711

.74

613

5627

1181

981

9309

1M

120.

0837

0.00

095

0.21

607

0.00

302

2.49

333

0.03

633

0.95

9239

98.1

212

85.3

21.9

412

61.1

16.0

312

70.1

10.5

66

1120

1495

8771

8104

1M

150.

0833

70.

0010

20.

2250

10.

0031

62.

5864

50.

0391

90.

9268

610

2.39

1277

.723

.66

1308

.316

.63

1296

.811

.10

1381

6311

769

8477

771

M16

A0.

0837

10.

0009

60.

2154

20.

0030

12.

4863

80.

0364

90.

9520

8197

.81

1285

.722

.32

1257

.615

.97

1268

.110

.63

811

0848

9487

7107

121

M16

B0.

0839

30.

0009

60.

2161

70.

0030

22.

5014

60.

0365

90.

9550

8697

.75

1290

.722

.05

1261

.616

1272

.510

.61

210

2221

8735

6532

641

M18

0.09

729

0.00

145

0.28

653

0.00

415

3.84

091

0.06

537

0.85

1008

103.

2715

72.8

27.6

616

24.2

20.7

816

01.4

13.7

110

6401

265

1030

9019

1M

190.

0830

50.

0011

20.

2217

70.

0031

32.

5398

60.

0407

50.

8796

7810

1.63

1270

.526

.03

1291

.216

.51

1283

.511

.69

912

6780

1076

578

5603

1M

210.

0833

60.

001

0.21

271

0.00

296

2.44

482

0.03

656

0.93

056

97.3

212

77.5

23.4

112

43.2

15.7

612

55.9

10.7

80

1314

6511

217

8481

231

M22

0.08

333

0.00

101

0.21

447

0.00

299

2.46

407

0.03

674

0.93

5015

98.1

012

76.8

23.4

512

52.6

15.8

512

61.6

10.7

72

1279

7210

987

8179

521

M01

0.08

379

0.00

091

0.22

363

0.00

321

2.58

316

0.03

794

0.97

7302

101.

0612

87.3

20.9

713

0116

.93

1295

.910

.75

021

2360

1808

513

5586

72

M02

A0.

0833

90.

0009

30.

2291

80.

0032

82.

6346

50.

0391

40.

9633

8410

4.09

1277

.921

.75

1330

.217

.22

1310

.410

.94

2520

1684

1709

012

4987

22

M02

B0.

0829

0.00

092

0.22

607

0.00

326

2.58

334

0.03

846

0.96

8606

103.

7412

66.5

21.4

213

13.9

17.1

112

95.9

10.9

118

0899

1523

011

4288

82

M03

0.08

461

0.00

097

0.21

755

0.00

313

2.53

730.

0382

90.

9533

9297

.14

1306

.322

.18

1268

.916

.58

1282

.810

.99

1218

1287

1557

011

8679

12

M08

0.08

546

0.00

097

0.21

857

0.00

315

2.57

474

0.03

870.

9588

3296

.13

1325

.621

.812

74.3

16.6

712

93.5

10.9

916

2391

0320

735

1562

628

2M

090.

0844

80.

0009

70.

2208

90.

0031

92.

5722

50.

0391

10.

9498

1798

.72

1303

.322

.23

1286

.616

.86

1292

.811

.12

1521

0256

1800

913

6188

22

M09

B0.

0834

80.

0009

60.

2261

0.00

329

2.60

166

0.03

974

0.95

2616

102.

6612

8022

.36

1314

17.2

813

01.1

11.2

719

7316

1669

712

5530

72

M10

†0.

0840

30.

0009

70.

2189

60.

0031

82.

5362

90.

0388

60.

9478

9198

.72

1292

.922

.36

1276

.416

.82

1282

.511

.16

1421

5173

1830

614

1265

02

M14

0.08

360.

0009

80.

2207

70.

0032

12.

5440

40.

0392

80.

9417

1110

0.26

1282

.722

.72

1286

16.9

712

84.7

11.2

55

1969

1616

651

1283

563

2M

150.

0833

20.

0009

80.

2147

50.

0031

42.

4663

60.

0382

40.

9430

5198

.27

1276

.222

.82

1254

.116

.64

1262

.211

.24

2349

6119

791

1579

914

2

134


Appe

ndix

2. U

-Pb

isoto

pic

age

data

for m

onaz

ite a

naly

ses

Sam

ple

1156

38

Spot

207 Pb

/206 Pb

1 σ

206 Pb

/238 U

1 σ

207 Pb

/235 U

1 σ

rho

Conc

. (%

)20

7 Pb/20

6 Pb a

ge1

σ20

6 Pb/23

8 U a

ge1

σ20

7 Pb/23

5 U a

ge1

σ20

4 Pb20

6 Pb20

7 Pb23

8 Pb

M01

†0.

1002

70.

0024

10.

2237

90.

0036

73.

0931

90.

0748

70.

6775

2317

79.9

016

29.2

44.0

913

01.8

19.3

214

3118

.57

5614

594

1511

8688

8M

05A

0.08

433

0.00

104

0.22

710.

0031

32.

6393

30.

0393

10.

9253

7519

101.

4713

00.2

23.8

1319

.316

.42

1311

.710

.97

035

709

3089

2112

96M

05B

0.08

369

0.00

109

0.21

839

0.00

302

2.51

875

0.03

876

0.89

8618

7899

.07

1285

.325

.24

1273

.416

1277

.511

.18

3131

708

2727

1947

47M

060.

0834

30.

0010

40.

2263

50.

0031

22.

6025

70.

0391

20.

9170

1759

102.

8312

79.2

24.2

813

15.4

16.4

313

01.4

11.0

311

2786

223

8816

5567

M06

B0.

0833

20.

0010

10.

2289

60.

0031

52.

6288

60.

0388

80.

9302

3385

104.

1312

76.4

23.6

613

29.1

16.5

113

08.7

10.8

820

2754

923

5416

1755

M08

0.08

248

0.00

104

0.23

277

0.00

322.

6455

90.

0398

60.

9124

482

107.

3412

56.8

24.2

813

4916

.75

1313

.411

.19

3731

931

6221

4924

M10

†0.

0851

30.

0011

60.

2233

80.

0031

2.62

046

0.04

149

0.87

6499

1798

.58

1318

.426

.35

1299

.716

.32

1306

.411

.64

025

733

2241

1537

14M

160.

0847

60.

0011

90.

2245

50.

0031

32.

6227

60.

0422

30.

8657

0265

99.6

913

09.9

2713

05.9

16.4

713

0711

.84

018

620

1613

1107

24M

16B†

0.08

459

0.00

127

0.22

449

0.00

315

2.61

683

0.04

421

0.83

0555

2999

.96

1306

.129

.01

1305

.616

.613

05.4

12.4

10

3732

532

3322

1656

M17

0.08

602

0.00

112

0.22

080.

0030

52.

6173

90.

0401

70.

9000

5154

96.0

813

38.6

24.9

512

86.1

16.1

113

05.5

11.2

77

1924

116

9811

6763

M18

0.08

602

0.00

102

0.22

608

0.00

309

2.67

984

0.03

903

0.93

8440

398

.15

1338

.722

.71

1313

.916

.27

1322

.910

.77

1644

510

3901

2646

36M

19A

0.08

436

0.00

10.

2289

60.

0031

32.

6615

60.

0387

60.

9387

2247

102.

1613

00.9

22.7

713

2916

.44

1317

.910

.75

734

636

2975

2034

31M

19B

0.08

280.

0009

80.

2254

90.

0031

2.57

270.

0376

40.

9396

6692

103.

6612

64.5

22.8

313

10.8

16.2

812

92.9

10.7

4739

804

3355

2380

75M

200.

0856

30.

0009

50.

2263

20.

0030

62.

6705

70.

0374

0.96

5452

3898

.90

1329

.821

.413

15.2

16.0

913

20.3

10.3

50

1634

8814

317

9676

83M

210.

0844

50.

0010

20.

2284

50.

0031

42.

6584

70.

0392

70.

9304

8494

101.

8113

02.8

23.2

613

26.4

16.4

813

1710

.90

3090

926

5518

2235

M22

0.08

510.

0010

80.

2283

80.

0031

72.

6780

90.

0408

10.

9108

7706

100.

6313

17.7

24.3

813

2616

.63

1322

.411

.27

220

585

1782

1218

31M

22B

0.08

510.

0011

0.22

90.

0031

92.

6853

60.

0414

40.

9026

8862

100.

8713

17.7

24.8

313

29.2

16.7

513

24.4

11.4

20

1848

716

0210

9343

M24

0.08

513

0.00

107

0.22

805

0.00

316

2.67

502

0.04

062

0.91

2523

6310

0.45

1318

.424

.23

1324

.316

.59

1321

.611

.22

028

125

2437

1666

97M

25†

0.08

473

0.00

136

0.22

898

0.00

328

2.67

310.

0478

10.

8008

8979

101.

5213

09.2

30.9

413

29.1

17.2

1321

13.2

20

4398

937

8625

8830

M26

0.08

505

0.00

104

0.23

286

0.00

323

2.72

927

0.04

094

0.92

4711

5710

2.50

1316

.623

.63

1349

.516

.913

36.5

11.1

50

3565

431

0020

8015

M28

0.08

512

0.00

116

0.23

612

0.00

333

2.76

984

0.04

458

0.87

6246

0610

3.66

1318

.326

.36

1366

.517

.39

1347

.412

.01

017

576

1524

1013

22M

290.

0834

30.

0010

60.

2344

20.

0032

42.

6957

10.

0411

30.

9058

6777

106.

1412

79.1

24.5

713

57.6

16.9

1327

.311

.30

1283

7210

951

7391

81

135


Appe

ndix

2. U

-Pb

isoto

pic

age

data

for m

onaz

ite a

naly

ses

Sam

ple

1156

69

Spot

207 Pb

/206 Pb

1 σ

206 Pb

/238 U

1 σ

207 Pb

/235 U

1 σ

rho

Conc

. (%

)20

7 Pb/20

6 Pb a

ge1

σ20

6 Pb/23

8 U a

ge1

σ20

7 Pb/23

5 U a

ge1

σ20

4 Pb20

6 Pb20

7 Pb23

8 Pb

M03

0.08

331

0.00

089

0.22

727

0.00

322.

6106

40.

0373

70.

9836

2998

103.

4412

76.3

20.7

413

20.2

16.8

213

03.6

10.5

120

4545

6238

546

2803

357

M06

0.08

322

0.00

092

0.23

220.

0032

62.

6644

20.

0386

50.

9678

5115

105.

6312

74.2

21.4

813

4617

.04

1318

.610

.71

2449

9619

4218

329

9615

0M

07A

0.08

404

0.00

094

0.22

485

0.00

315

2.60

544

0.03

789

0.96

3327

8910

1.09

1293

.421

.52

1307

.516

.58

1302

.210

.67

1941

0232

3505

325

3539

9M

07B

0.08

468

0.00

093

0.22

630.

0031

72.

6423

90.

0382

80.

9669

4038

100.

5313

08.2

21.2

913

15.1

16.6

913

12.5

10.6

716

4223

0636

384

2598

236

M08

0.08

379

0.00

098

0.23

387

0.00

329

2.70

224

0.04

046

0.93

9548

9710

5.23

1287

.522

.68

1354

.817

.16

1329

.111

.114

4838

4541

004

2872

836

M09

0.08

373

0.00

095

0.23

159

0.00

327

2.67

364

0.03

954

0.95

476

104.

4112

86.1

22.0

213

42.8

17.1

1321

.210

.93

2532

9310

2796

119

8717

6M

110.

0837

40.

0010

20.

2269

80.

0031

92.

6209

20.

0399

50.

9220

1943

102.

5212

86.3

23.4

913

18.7

16.7

613

06.5

11.2

1032

0244

2711

219

5482

5M

11B†

0.08

477

0.00

112

0.22

787

0.00

323

2.66

345

0.04

268

0.88

4576

7210

1.01

1310

.125

.42

1323

.316

.94

1318

.411

.83

1732

6375

2792

319

8417

2M

120.

0854

80.

0010

90.

2327

80.

0032

82.

7438

60.

0431

10.

8968

3408

101.

7013

26.4

24.5

913

4917

.15

1340

.411

.69

2546

4613

3998

027

6049

4M

130.

0852

60.

0010

50.

2261

50.

0031

92.

6590

10.

0408

20.

9188

4247

99.4

613

21.5

23.6

313

14.3

16.7

513

17.1

11.3

325

2534

5921

845

1554

854

M14

0.08

519

0.00

094

0.22

710.

0031

72.

6672

20.

0384

50.

9682

8816

99.9

513

19.9

21.2

913

19.3

16.6

513

19.4

10.6

416

2479

2821

495

1512

111

M15

0.08

463

0.00

093

0.23

132

0.00

324

2.69

874

0.03

890.

9717

2477

102.

6413

06.9

21.3

613

41.4

16.9

413

28.1

10.6

825

1929

6816

626

1157

942

M15

B0.

0842

30.

0009

30.

2246

0.00

314

2.60

815

0.03

769

0.96

7445

0910

0.63

1297

.921

.33

1306

.116

.53

1302

.910

.61

1532

3889

2776

220

0114

3M

16A

0.08

411

0.00

093

0.23

376

0.00

327

2.71

074

0.03

912

0.96

9318

6610

4.56

1295

.121

.33

1354

.217

.113

31.4

10.7

15

3694

2831

746

2195

021

M17

B0.

0845

80.

0009

50.

2218

40.

0031

12.

5866

30.

0376

80.

9623

7415

98.9

113

05.8

21.6

812

91.6

16.4

1296

.910

.67

936

3556

3138

222

7579

1M

18A

0.08

357

0.00

097

0.22

922

0.00

321

2.64

122

0.03

910.

9459

7649

103.

7312

82.5

22.5

513

30.4

16.8

313

12.2

10.9

1637

9872

3237

722

9392

2M

18B†

0.09

204

0.00

127

0.23

533

0.00

335

2.98

719

0.04

912

0.86

5709

1492

.79

1468

.226

.14

1362

.417

.46

1404

.412

.51

139

2392

7322

363

1404

321

M23

0.08

292

0.00

10.

2288

20.

0032

22.

6161

10.

0396

50.

9284

8459

104.

8112

67.3

23.3

613

28.3

16.8

713

05.2

11.1

38

4059

3734

374

2456

670

M24

0.08

283

0.00

098

0.23

580.

0033

12.

6925

90.

0401

90.

9404

5153

107.

8712

65.2

22.6

913

64.8

17.2

913

26.4

11.0

50

3618

2230

652

2130

196

M26

A0.

0840

70.

0009

90.

2307

40.

0032

62.

6742

70.

0400

20.

9441

1061

103.

4212

94.1

22.6

613

38.4

17.0

713

21.4

11.0

67

1731

4414

892

1046

789

M26

B0.

0827

80.

0009

70.

2276

60.

0032

12.

5980

60.

0387

10.

9463

337

104.

6012

64.1

22.4

913

22.2

16.8

713

00.1

10.9

29

2801

8323

779

1716

076

136


Appe

ndix

2. U

-Pb

isoto

pic

age

data

for m

onaz

ite a

naly

ses

Sam

ple

1158

66

Spot

207 Pb

/206 Pb

1 σ

206 Pb

/238 U

1 σ

207 Pb

/235 U

1 σ

rho

Conc

. (%

)20

7 Pb/20

6 Pb a

ge1

σ20

6 Pb/23

8 U a

ge1

σ20

7 Pb/23

5 U a

ge1

σ20

4 Pb20

6 Pb20

7 Pb23

8 PbSe

ssio

n

M01

0.08

713

0.00

099

0.22

866

0.00

336

2.74

652

0.04

154

0.97

1550

4497

.37

1363

.321

.82

1327

.417

.61

1341

.111

.26

042

129

3788

2667

78a

M01

B0.

0856

80.

0009

90.

2297

50.

0033

72.

7139

50.

0411

80.

9666

9591

100.

1713

3122

.18

1333

.217

.66

1332

.311

.26

639

336

3476

2473

80a

M01

C0.

0842

60.

0009

80.

2319

50.

0033

82.

6946

10.

0409

0.96

0052

3910

3.56

1298

.522

.413

44.7

17.7

113

2711

.24

1539

950

3467

2475

93a

M01

D0.

0860

50.

0010

10.

2219

10.

0032

62.

6327

50.

0404

70.

9556

9022

96.4

513

39.4

22.6

512

91.9

17.2

113

09.8

11.3

114

3825

433

9324

9304

aM

01E

0.08

697

0.00

105

0.22

158

0.00

324

2.65

671

0.04

102

0.94

7028

2894

.89

1359

.723

.06

1290

.217

.08

1316

.511

.39

036

311

3253

2348

45a

M01

F0.

0866

30.

0010

60.

2303

40.

0033

72.

7508

90.

0427

90.

9405

7077

98.8

213

52.3

23.4

913

36.3

17.6

813

42.3

11.5

826

3594

132

2022

3541

aM

01G

0.09

120.

0011

10.

2258

50.

0032

82.

8386

0.04

381

0.94

0989

3290

.49

1450

.722

.97

1312

.717

.23

1365

.811

.59

2441

503

3889

2614

48a

M01

H0.

0890

40.

0010

80.

2226

0.00

322

2.73

157

0.04

212

0.93

8111

9892

.21

1405

22.9

612

95.6

1713

37.1

11.4

62

4606

441

9929

4408

aM

02A

0.08

406

0.00

093

0.22

301

0.00

328

2.58

476

0.03

863

0.98

4113

1210

0.29

1293

.921

.27

1297

.717

.28

1296

.310

.94

1014

8108

1288

096

7942

aM

02B†

0.09

450.

0010

80.

2190

90.

0032

22.

8548

40.

0432

10.

9710

2592

84.1

215

18.2

21.3

412

77.1

17.0

213

70.1

11.3

879

9912

096

8465

6253

aM

05A

0.08

699

0.00

123

0.22

964

0.00

341

2.75

399

0.04

672

0.87

5319

0297

.96

1360

.327

.05

1332

.617

.913

43.2

12.6

418

4070

036

2525

3702

aM

05B

0.08

537

0.00

113

0.22

279

0.00

327

2.62

223

0.04

282

0.89

8827

1497

.94

1323

.925

.56

1296

.617

.23

1306

.912

2358

715

5105

3760

38a

M06

0.08

814

0.00

122

0.22

858

0.00

338

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Elem

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142


Zirc

on tr

ace

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once

ntra

tions

nor

mal

ised

to ch

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ite.

Elem

ent

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270.

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0.00

019

0.00

277

00.

0031

70.

0203

0.53

10.

155

0.30

30.

531

0.00

613

0.00

926

0.19

4Si

291.

311.

251.

261.

151.

21.

161.

211.

431.

321.

821.

441.

670.

91.

21.

87Ti

490.

188

0.02

60

0.03

30

00

00

00

00

0.07

40

V51

0.43

50.

0033

00

00

00

0.23

10

00.

059

00.

0101

0Fe

570.

0098

90

0.00

007

00

00

00

00.

0010

10.

0010

10

0.00

013

0Y8

915

.28

17.6

523

.09

21.6

624

.53

26.0

714

.48

17.0

550

.97

47.0

921

.44

32.3

17.6

217

.24

55.7

Zr90

9688

3.01

1069

53.4

399

518.

0110

0232

.88

1022

71.1

898

110.

894

254.

8393

295.

1110

0427

.910

2357

.11

1012

51.3

595

953.

1490

989.

496

519.

6789

668.

88Nb

937.

317.

657.

137.

096.

926.

226.

356.

296.

696.

277.

875.

265.

357.

370

La13

90

00.

074

00

00

015

.66

03.

2111

.01

00

0Ce

140

0.30

90.

20.

049

0.19

70.

215

0.22

50.

526

1.36

50.

870.

7815

.93

0.29

60.

421

Pr14

10.

341

00

00

00

014

.08

00

12.3

70

0.37

6.83

Nd14

60.

155

00.

213

0.19

40

00

024

.90

012

.76

00

0Sm

147

00

0.88

0.56

00

00

11.6

40

014

.70

1.68

0Eu

153

1.12

0.98

02.

371.

651.

831.

330

16.6

30

08.

471.

310

0Gd

157

2.77

3.12

2.67

4.19

4.26

4.6

2.02

017

.18

10.0

40

21.5

42.

653.

760

Tb15

94.

45.

826.

776.

958.

58.

844.

696.

7217

.317

.22

8.74

11.1

55.

695.

910

Dy16

38.

89.

4911

.75

12.0

514

.16

14.4

98.

0110

.216

.99

24.9

914

.13

17.3

59.

698.

9824

.85

Ho16

512

.913

.72

17.7

618

.41

20.4

221

.56

11.1

310

.18

28.4

838

.54

15.7

924

.68

14.0

613

.04

46.3

9Er

166

14.6

317

.03

19.1

421

.15

23.3

528

.58

15.6

118

.33

26.4

347

.62

18.8

927

.316

.25

16.3

191

.2Tm

169

19.0

822

.85

25.7

426

.95

31.5

638

.84

21.6

428

.23

27.3

650

.74

26.1

329

.37

18.5

320

.57

189.

77Yb

172

26.5

234

.97

34.8

139

.02

41.1

52.6

629

.39

26.6

526

.966

.43

32.9

630

.37

23.1

327

.56

345.

78Lu

175

26.7

332

.65

30.2

935

.98

35.4

149

.79

32.3

32.3

128

.59

80.1

533

.75

42.7

623

.92

27.5

655

7.28

Hf17

861

524.

8864

470.

0765

017.

2362

916.

762

458.

1359

106.

0164

164.

0460

914.

2568

414.

3765

637.

8365

604.

1960

339.

6258

138.

1862

948.

4565

722.

61Ta

181

1.97

02.

852.

370

00

08.

590

00

3.36

00

Th23

213

.31

6.94

2.97

21.8

620

.23

9.09

14.4

217

.18

51.2

619

.39

20.0

313

.89

14.5

718

.24

658.

95U2

3810

60.7

399

3.56

277.

0296

9.01

742.

4510

00.9

340

0.27

479.

0793

6.25

821.

6553

9.16

261.

7148

7.84

440.

5742

07.6

1LR

EE (S

m/L

a)-

-11

.89

--

--

-0.

74-

0.00

1.34

--

-HR

EE (L

u/Gd

)9.

6510

.46

11.3

48.

598.

3110

.82

15.9

9-

1.66

7.98

-1.

999.

037.

33-

MHR

EE (L

u/Sm

)-

-34

.42

64.2

5-

--

-2.

46-

-2.

91-

16.4

0-

Eu/E

u*-

--

1.55

--

--

1.18

--

1.37

--

-

META

MO

RPHIC A

ND ISOTO

PIC CHA

RACTERISATIO

N

OF PROTERO

ZOIC BELTS AT TH

E MA

RGIN

S OF TH

E N

ORTH

AN

D WEST A

USTRALIA

N CRATO

NS

RECORD 2019/8

Anderson

This Record is published in digital format (PDF) and is available as a free download from the DMIRS website at <www.dmp.wa.gov.au/GSWApublications>.

Information Centre Department of Mines, Industry Regulation and Safety 100 Plain Street EAST PERTH WESTERN AUSTRALIA 6004 Phone: +61 8 9222 3459 Fax: +61 8 9222 3444 www.dmp.wa.gov.au/GSWApublications

Further details of geoscience products can be obtained by contacting:

metamorphic and isotopic characterisation of proterozoic belts at … · 2020-03-30 · anderson, j...

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