A

B

INTRODUCTION

CONCLUSIONSFIELD RELATIONS FRACTIONATION

REFERENCES

P-T Conditions during pegmatite formation

AGE DATA

B ) M o d e l m e l t i n g reactions in the Qtz-sa tura ted CKNASH s y s t e m i n v o l v i n g reaction curve position beside the one for the dehydration melting of muscovite (H2O) depend on the availability of H2O and XH2O in the fluid phase. This is indicated by the displacement of reactions (L) and (Ms) for XH2O = 0.7. Solid lines are valid for pure H2O-fluid in excess. Dashed lines are valid for a fluid of composition XH2O = 0.7.Abbreviations: alumino-silicate = Als; muscovite = Ms; plagioclase = Pl; K-feldspar = Kfs; melt = L ; q u a r t z = Q t z . C o m p i l e d f r o m THOMPSON & ALGOR (1977) and KERRICK (1972). Stability fields of Li phases according to LONDON (1984).

Figure 3 (right). P-T diagrams. A) KNASH-equilibrium phase diagram for common high-Al metapelites, showing the relationships between white micas and feldspars. Note that most of the equilibria shown on the right hand side of the H2O-saturated granite solidus become metastable in the presence of melt. Calculations for the diagram were made using Theriak/Domino software (DE CAPITANI & PETRAKAKIS, 2010) for the bulk composition shown above of the figure. Abbreviations: kaolinite = Kln; pyrophyllite = Prl; white mica = WM; feldspar = Fsp; quartz = Qtz; kyanite = Ky; andalusite = And; sillimanite = Sil; aluminosilicate = Als. Dashed lines indicate prograde Permian P-T paths for rocks of the sillimanite zone (black) and andalusite zone (grey) (modified from SCHUSTER at al., 2001).

New sight on Li-rich Pegmatites within the Austroalpine unit (Eastern Alps) and their evidence for an anatectic origin

In parts of the Austroalpine units, pegmatites with the incidence of Li-pyroxene spodumene (LiAl[Si2O6]) appear heterogeniously distributed over a distance of more than 400 km (Fig. 1, 2).

There are two general views on the genesis of these pegmatites. On one hand tht Li-bearing pegmatites belong to the Rare Element class of pegmatites, which is thought to develop exclusively through fractionation of granitic parent plutons. On the other hand the associated barren pegmatites are considered as products of anatexis of metapelitic country rocks.

Through the last years a new understanding of the geodynamic evolution of the Austroalpine basement could be revealed and field mapping results showed that in parts of the Austroalpine units migmatitic mica schists with interlayered barren pegmatites occur. In order to that in structural higher levels there are areas with enriched pegmatites like spodumene bearing pegmatites.

ČERNÝ, P., & ERCIT, T. S. (2005): The classification of granitic pegmatites revisited. Can. Mineral., 43/6: 2005-2026.

DE CAPITANI, C. & PETRAKAKIS, K. (2010): The computation of equilibrium assemblage diagrams with Theriak/Domino software. Am. Mineral., 95:1006-1016.

ERTL, A., MALI, H., SCHUSTER, R., KÖRNER, W., HUGHES, J.M., BRANDSTÄTTER, F. & TILLMANNS, E. (2010): Li-bearing, disordered Mg-rich tourmalines from the pegmatite-marble contact from the Austroalpine basement units (Styria,Austria). Miner. Petrol., 99/1-2: 89-104.

GASSNER, M.(2001): Geochemische und petrologische Untersuchungen an ausgewählten steirischen Pegmatiten (Koralpe, Stubalpe, Kristallin von St. Radegund, Anger-Kristallin). Unveröff. Dipl. Arb., Leoben, 176 S.

GÖD, R. (1989): The spodumene deposit at “Weinebene”, Koralpe, Austria. Miner. Deposita, 24: 270–278.KERRICK, D.M. (1972): Experimental detemination of muscovite+quartz stability with PH2O <Ptotal. Am.

J. Sci., 271: 946-958.LONDON, D. (1984): Experimental phase equilibria in the system LiAlSiOn-SiOr-H2O: a petrogenetic grid

for lithium-rich pegmatites. Am. Mineral., 69: 995-1005.LONDON, D. (2008): Pegmatites. Can. Mineral., Special Publication 10: 347 S.MALI, H. (2004): Die Spodumenpegmatite von Brettstein und Pusterwald (Wölzer Tauern, Steiermark,

Österreich). Joannea - Mineralogie, 2: 5-53.SCHUSTER, R., & STÜWE, K., (2008): The Permian Metamorphic Event in the Alps. Geology, 36/8:303-

306.SIMMONS W.M.B., FOORD, E., & FALSTER A. (1996): Anatectic origin of granitic pegmatites, western

Maine. USA GAC-MAC Ann. Mtng. Winnipeg, Abstr. Prog., 87 S.SENZENBERGER, D. (2001): Zonarbau und geochemische Charakteristik von Pegmatiten des Hohenwart

(Wölzer Tauern, Steiermark). Unveröff. Dipl. Arb., Leoben, 176 S.STÖCKHERT, B. (1987): Das Uttenheimer Pegmatitfeld (Ostalpines Altkristallin, Südtirol) Genese und

alpine Überprägung. Erlanger geol. Abh., 114: 83-106.THÖNI, M. & MILLER, CH. (2000): Permo-Triassic pegmatites in the eo-Alpine eclogite-facies Koralpe

complex, Austria: age and magma source constraints from mineral chemical, Rb-Sr and Sm-Nd isotopic data. Schweiz. Min. Petro. Mitt., 80:169-186.

Figure 5. Examples of Permian pegmatites from the Austroalpine unit: A) Spodumene bearing pegmatite with large spodumene crystals embedded in a quartz-rich matrix including feldspar and tourmaline (Mitterberg pegmatite, Übelbach valley, Styria). B) Comb structures with turmaline embedded in quartz and feldspar, reflecting the growth of tourmaline perpendicular to the wall rock. The deformation of the tourmaline is due to the Alpine overprint (Mitterberg pegmatite, Übelbach valley, Styria) C, D) Thin sections showing large spodumene crystals with overgrowths of myrmekite consisting of spodumene and quartz invading feldspar (Hohenwart, Niedere Tauern, Styria; width of image 11.5 and 3.5 mm respectively; crossed polarizers).

Figure 6. Thin sections of two different spodumene-pegmatites showing: A, B) Large Permian spodumene crystals within a recrystallised matrix of quartz and feldspar (Falkenberg, Judenburg, Styria; width of image 11.5 mm; parallel and crossed polarizers). C, D) Turmaline and garnet crystals in a fine grained, recrystallized quartz matrix (Hohenwart, Niedere Tauern, Styria; width of image 7.5 mm; parallel and crossed polarizers).

Figure 8. Age data from spodumene pegmatites: A) Hand picked garnet separate for Sm/Nd dating. B, C) Sm/Nd ages calculated from garnets and whole rocks of spodumene pegmatites. D) Rb/Sr age diagram calculated from spodumene, muscovite and feldspar. The Sm/Nd ages indicate crystallisation of the melts in Permian time at 265 Ma. The Rb/Sr ages determined from the same pegmatite as one of the Sm/Nd age diagrams yields also a Permian value. However, the ages calculated with muscovite and spodumene are slightly different. This might be due to incomplete equilibrium of the crystallizing minerals.

As source rocks for the pegmatitic melts we expect Al-rich metapelites derived from marine shales.

During the Permian event a temperature increase at more or less constant pressures caused melting of white mica, feldspar and quartz with additional H2O at 650-700 °C and 0.4–0.6 GPa, within the sillimanite stability field .

Breakdown of staurolite may have served as additional source for Li in the primary melts. Subsequent internal fractionation lead to further Li-enrichment and crystallization of spodumene from the most evolved melts, whereas less enriched/fractionated melts formed co-genetic barren pegmatites .

Further-looking the project should reveal the possibility of pegmatites with an anatectic origin through geochemical and geochronological investigation of spodumene-pegmatite, barren pegmatite and the surrounding metamorphic rocks of pegmatite fields within the Austroalpine unit.

Additionally the aspire results are suitable for the prospection of spodumene-pegmatites. New data on trace element contents (e.g. U, Th, Li, Cs, Zn, As, Cd) in meta-pelites is going to be part of the geochemical recording of Austroalpine metamorphic rocks.

Figure 4 (below). Panoramic view of the Hohenwart Region in the Niedere Tauern (Styria), one of the largest Spodumene-Pegmatite fields within the Austroalpine unit. The yellow arrow indicates a spodumene-pegmatite dike.

Figure 1. Overview map showing the paleogeographic origin of the main tectonic units of the Alps.

Figure 7. Chemical analysis of muscovites out of spodumene-pegmatites (blue) and barren pegmatites (red) taken from Koralpe, Gleinalpe, St. Radegund, Anger and Niedere Tauern (GASSNER, 2001, SENZENBERGER, 2001, MALI, 2004, and unpublished data). The data might reflect a continous fractionation trend from the barren to the spodumene pegmatites.

Figure 2. Overview map showing the distribution of barren and spodumene bearing pegmatites within the Austroalpine , according to FRIEDRICH unit(1951), MALI (2004), SCHUSTER & STÜWE (2008) and references therein. Also indicated are major Permian pegmatite fields.

Abbreviations: spodumene = Spd; b-spodumene = Bspd; eucryptite = Ecr; petalite = Pet; virgilite = Vrg. Dashed lines indicate expected cooling paths for pegmatites within their source areas (black) and for migrated fractionated pegmatites (grey).

1Geological Survey of Austria, Neulinggasse 38, A-1030 Wien, Austria

Tanja.Ilickovic@geologie.ac.at, Ralf.Schuster@geologie.ac.atAlbert.Schedl@geologie.ac.at

AustroalpinePegmatites

1 1 2 3 1Tanja ILICKOVIC , Ralf SCHUSTER , Heinrich MALI , Konstantin PETRAKAKIS , Albert SCHEDL

2Department für Angewandte Geowissenschaften und Geophysik, Montanuniversität Leoben A-8700 Leoben, Peter-Tunner-Straße 5, Austria,

heinrich.mali@unileoben.ac.at

3Departement of Geodynamics an Sedimentology,Althanstraße 14, A-1090 Wien, Austria

konstantin.petrakakis@univie.ac.at

Geologische Bundesanstalt

T [°C]

T [°C]

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GP

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P [

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200 300 400 500 600 700 800

KyAnd

2 F

sp1 F

sp

And

SilKy

SilAnd

Ky

And

KyAnd

Prl

3aQ

tz +

Ky

+ H

2O

Kln

+ 2

aQ

tzP

rl +

H2O

aQ

tzbQ

tz

2 W

M1

WM

2 F

sp1 F

sp

2 W

M +

Kln

2 W

M +

Prl

2 W

M +

And

2 WM + Ky

Fsp + Sil

WM

+ F

sp +

Als

WM

+ a

Qtz

Spd Qtz

PetSpd Qtz

PetSpdEcr Qtz

Ecr Q

tz

P

etBspd Qtz Pet

VrgBsp

H2O

-satu

rate

d g

ranite

solid

us

L

Kfs P

l Als

L

Kfs P

l Als

Ms

Pl

Als

Kfs

L

Ms

Pl K

fsp

LM

s P

lA

ls L

Ms Pl

Als K

fs

(L) (Ms)

(Als) (Kfs) (H2O)+ H2O+ Fluid

XH2O = 1.0XH2O = 0.7

H2O

-satu

rate

d g

ranite

solid

us ~ 40 °C

/km

KNASH-pelite: 0.55Als+0.20Ab+0.25Kfs

A B

C DSpd

Spd

FspQtz

Qtz

FspMsc

Fsp

Qtz Qtz

Grt

Spd

Tur Tur

Grt

Spd

Fsp

14R16spodumene pegmatite,Rappold Complex,Mitterberg, Übelbachvalley, Styria

0.508

0.512

0.516

0.520

0.524

0 2 4 6 8

04R45

WRIo = 0.51190 ± 1

spodumene pegmatite,Rappold ComplexHohenwart, Styria

264 ± 3 Ma

Nd

/

Nd

143 1

44

Sm/ Nd147 144

Grt

14R23

Sp-Fsp: Io = 0.629 ± 5

spodumene pegmatite Rappold ComplexMitterberg, Übelbachvalley, Styria

272 ± 3

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WR Io = 0.51188 ± 1

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Neogene and Quarternarysedimentary rocks

Nappes derived from the Neotethys ocean (Meliata zone, Vardar zone,Sava belt)

Adria derived units (e.g. Austro-alpine nappes, Southalpine Unit) Nappes derived from the Penninic (Alpine Tethys) oceanic realm (Penninic nappes)

Europe derived units (e.g. Helvetic nappes, Subpenninic nappes)

Mediterranean Sea

Wien

Maribor

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48°

46°

44°

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48°

46°

Genève

Wien

Zagreb

München

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Zürich

Maribor

AdriaticSea

11° 13° 15° 17°

Fig. 2

without Permian metamorphic imprint

Permian volcanic rocks

Permian and Triassic granites

Permian gabbros

with lower greenschist facies imprint

with upper greenschist facies imprint (garnet present)

with amphibolite facies imprint and Permian pegmaties

Late Paleogene to Neogene sediments and volcanic rocks

Permian to Paleogene sediments and magmatic rocks

faults and nappe boundariesUnits of pre-Permian (meta)sediments and magmatic rocks

Permian spodumene bearing pegmatites

Periadriatic fault

Adamello

Molasse basin

12°10° 11° 13° 14°15°

16°17°

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Hohenwartarea

Weinebene

St. Radegund

Millstattarea

Uttenheimpegmatite field

Übelbacharea

Garnet concentrate from the spodumene pegmatite at Hohenwart (sample 04R45, width of image 1 mm)

A B

C D

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C D

Spd

Fsp

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Cs [ppm] Tl [ppm]

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spodumene bearing zones

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barren pegmatites

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