Evolution of Alpine eclogites in the Eastern Alps: Implications for Alpine geodynamics |
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| Institution: | 1. Institute of Mineralogy, University of Münster, 48149 Münster, Germany;2. School of Earth and Space Sciences, USTC, Hefei, Anhui 230026, China;1. Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, 128 ul. Lermontova 128, Irkutsk, 664033, Russia;2. Far Eastern Federal University, ul. Sukhanova 8, Vladivostok, 690091, Russia;3. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, 664033, Irkutsk, Russia;4. Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakhyanovoi 6a, Ulan-Ude, 670047, Russia;5. V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia;1. Department of Mineralogy Herman Ottó Museum, Kossuth u. 13, H-3525 Miskolc, Hungary;2. Department of Petrology and Geochemistry, Eötvös Loránd University, Péter Pázmány sétány 1/c, H-1117 Budapest, Hungary;3. Centre for Energy Research, Hungarian Academy of Sciences, PO Box 49, H-1525 Budapest 114, Hungary;4. Department of Mineralogy and Petrology, University of Miskolc, Miskolc-Egyetemváros, H-3515 Miskolc, Hungary;5. Department of Mineralogy and Geology, University of Debrecen, Egyetem tér 1, H-4001 Debrecen, Hungary |
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| Abstract: | In the Eastern Alps Alpine eclogites are generally associated with rocks of continental lithosphere, while eclogites that are associated with oceanic assemblages are restricted to minor exposures. Such eclogites are exposed both in the Penninic unit of the Tauern Window and in the Austroalpine nappe complex. (1) In the central southern part of the Tauern Window (Eclogite Zone) eclogites and associated high pressure metasediments of a distal continental margin are intercalated between Penninic basement units. A mylonitic eclogitic foliation and stretching lineation are contemporaneous to the high pressure metamorphism and are related to the subduction of distal Penninic continental margin sequences. Continuous subduction of cool lithosphere resulted in blueschist facies overprint of the whole Penninic nappe pile. (2) Within the Middle-AustroAlpine Koralm/Saualm region most eclogites are eclogitic mylonites documenting plastic deformation of omphacite and garnet. The meso- and macroscale structures indicate an overall extensional regime possibly related to a large-scale SE-directed ductile low-angle normal shear zone. The eclogites are associated with migmatite-like structures and are intruded by pegmatites. This indicates decreasing pressure, but isothermal or even increasing temperature conditions during exhumation.These relationships argue for the subduction of Penninic continental lithosphere in the foot-wall of the Austroalpine unit at the time of exhumation of the Koralm/Saualm eclogites. Formation of the Austroalpine eclogites is explained by subduction of continental lithosphere, and subsequent, rapid exhumation in an upper plate tectonic position within an extensional regime. |
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