INTRODUCTION Dronning Maud Land (DML) is located in the Weddell Sea sector of East Antarctica. It covers an area of ~5 Mio km 2 and is divided by large glacial drainage systems into an eastern, a central and a western part. The Proterozoic metamorphic base- ment of DML is exposed in remnants of an intensely dissected highly elevated plateau that are bound by steep escarpments, aligned parallel to the coast. The most significant outcrop massifs are the Orvinfjella–Wohlthatmassiv of central DML and Sør Rondane to the east (Fig. 1). The petrological composition and the structural inventory of these rock massifs have been studied during recent decades by Soviet, Indian and German expeditions (e.g. RAVICH & KRYLOV 1964, RAVICH & SOLOV`EV 1969, RAVICH & KAMENEV 1972, VERMA et al. 1987, P AECH 2004, 2005b). In contrast, little attention has been given to a series of poorly exposed nunataks and moraines in the southern part of DML. The QueenMET (Queen Maud Land Meteorites) expedition during the Austral summer 2007/2008 provided an opportunity to study one of these areas for the first time. Participants in QueenMET were the physicist G. Delisle and the geophysicist U. Barckhausen from the German Federal Institute for Geo- sciences and Natural Resources (BGR) Hannover, the minera- logist J. Schlüter from the University of Hamburg, and the mountain guide J. Gessler from Basel. The aim of the expedi- tion was the first search for meteorites in DML inspired by the large number of meteorites recovered by Japanese and American scientists from blue ice fields in other Antarctic regions (e.g. Sør Rondane, Yamato Icefield, Allan Hills, Elephant Moraine). Besides the successful QueenMET search for meteorites, the scientists also devoted some time and effort to the exploration of a small group of previously undescribed nunataks at Stein- garden, located southeast of Wohlthatmassiv, Weyprechtberge, and Payergruppe (Figs. 1, 2). The investigated area stretches from about 72°12’S – 72°22°’S and 15°59’E –16°10’E and is located approx. 2000 km from the South Pole. The average elevation of the area is 2400 m above sea level. Its rock inven- tory is of great interest because the Steingarden region covers an area which is located in a possible continuation of the still undiscovered suture between East and West Gondwana (MOYES et al. 1993, GRUNOW et al. 1996, SHIRAISHI et al. 1994, JACOBS et al. 1998) (Fig. 3). Until now, no information on the 161 Abstract: Rock samples from previously undescribed nunataks and moraines of the Steingarden area, southeasternmost central Dronning Maud Land, Antarctica, were petrographically studied. The nunatak rocks comprise banded felsic and mafic gneisses and amphibo- lites with some minor marbles. They underwent granulite-facies peak meta- morphism. Moraine rocks, which were sourced from ice-covered occurrences in the south, comprise garnet-biotite gneisses, kyanite-staurolite-sillimanite gneisses, amphibolites, late-tectonic and post-tectonic igneous rocks as well as an assemblage of conspicuous dark graphite-bearing and pyrite-bearing schists with related vanadium-green muscovite bearing lithologies. The dark schists represent greenschist-facies to amphibolite-facies grade metamor- phosed black-shale-type sediments. The nunatak rocks and parts of the moraine rocks are comparable to litholo- gies in central Dronning Maud Land. The dark graphite-bearing and pyrite- bearing schists and related vanadium-green muscovite bearing lithologies have higher-grade metamorphosed equivalents in central Sør Rondane. These rocks indicate the existence of a tectonic boundary south of Steingarden, which may represent the Pan-African suture between West and East Gond- wana. Zusammenfassung: Gesteinsproben bisher nicht untersuchter Nunataks und Moränen der Steingarden Region im südöstlichsten Teil des zentralen Dron- ning Maud Landes, Antarktis, wurden petrographisch bearbeitet. Die Nunatak-Gesteine umfassen gebänderte felsische und mafische Gneise, Amphibolite und untergeordnet Marmore, die granulitfazielle Bedingungen erreicht haben. Moränen-Gesteine, welche von eisbedeckten Vorkommen im Süden stammen, umfassen Granat-Biotit-Gneise, Disthen-Staurolith-Silli- manit-Gneise, Amphibolite, spät- und post-tektonische magmatische Gesteine sowie eine Ansammlung auffälliger dunkler Graphit und Pyrit führender Schiefer und Lithologien mit vanadiumgrünem Muskovit. Die dunklen Schiefer repräsentieren Sedimente vom Schwarzschiefer-Typ, die eine grün- schieferfazielle bis amphibolitfazielle Metamorphose erfahren haben. Die Nunatak-Gesteine und ein Teil der Moränen-Gesteine sind mit den Litho- logien des zentralen Dronning Maud Landes vergleichbar. Die dunklen Graphit und Pyrit führenden Schiefer und die assoziierten, vanadiumgrünen Muskovit enthaltenden Lithologien haben hochgradig metamorphe Äquiva- lente im zentralen Gebiet von Sør Rondane. Diese Gesteine deuten die Existenz einer tektonischen Grenze südlich der Steingarden Region an, bei der es sich um die Pan-Afrikanische Sutur zwischen West- und Ost-Gondwana handeln könnte. ____________ 1 Universität Hamburg, Mineralogisches Museum, Grindelallee 48, 20146 Hamburg, Germany. 2 Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Stilleweg 2, 30655 Hanno- ver, Germany. 3 Universität Bremen, FB 5 - Geowissenschaften, Klagenfurter Str. 2, 28359 Bremen, Germany. * communicating author: <[email protected]> Manuscript received 02 March 2011, accepted in revised form 31 May 2011. Polarforschung 80 (3), 161 – 172, 2010 (erschienen 2011) First Petrographical Description of Rock Occurrences in the Steingarden Area, Dronning Maud Land, East Antarctica by Jochen Schlüter 1 , Solveig Estrada 2* , Frank Lisker 3 , Andreas Läufer 2 , Rebecca Kühn 3 , Kai Nils Nitzsche 3 and Cornelia Spiegel 3 Umbruch 28.10.2011 21:21 Uhr Seite 161
First Petrographical Description of Rock Occurrences in the Steingarden Area, Dronning Maud Land, East Antarctica
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