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Publication

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Neubauer, Franz ; Hoinkes, Georg ; Sassi, F. P. ; Handler, Robert ; Höck, Volker ; Koller, Friedrich ; Frank, Wolfgang

Paperwork

1999

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UBS-NW: Zs 20

Schweizerische mineralogische und petrographische Mitteilungen <Zürich>, 79(1): p 41-62 Basement successions are exposed within three different domains constituting the Eastern Alps, i.e. the Penninc, Austroalpine and Southalpine units. These were variably overprintd by a variety of metamorphic facies ranging from medium-pressure greenschist-facies to migmatite conditions, and to high-pressure eclogite facies metamorphic conditions during various tectonothermal events including the Late Cadomian, Caledonian and Variscan orogenies. The Penninic basement exposed within the Tauern window is largely overprinted by Variscan amphibolite facies metamorphism associated with intrusions of Variscan granites. Silurian eclogites predate migmatite formation. The Austroalpine basement units vary in metamorphic grade and their timing of metamorphism. Lower Austroalpine units along the eastern margins of the Alps record 1) Devonian high-pressure metamorphism overprinted by Variscan greenschist metamorphic condition in the Wechsel unit, and 2) early Variscan amphibolite facies metamorphic conditions later locally overprinted by granulite facies conditions within the Kirchberg-Stuhleck unit. Middle Austroalpine units are polymetamorphic and were largely overprinted by amphibolite facies metamorphic conditions during Variscan orogeny subsequent to distinct earlier metamorphic events. Early Variscan eclogites were locally recorded from the Ötztal basement. Silurian to Devonian medium-grade metamorphism is also locally reported from northeastern Upper Austroalpine Units. The Upper Austroalpine unit and Lower Austroalpine Quartzphyllite units generally record late Variscan greenschist metamorphic overprint similar to that recorded in Southalpine units. The different timing and the different features of the pre-Alpine metamorphic evolution are interpreted to result from accretion of various units to the active Laurasian continental margin. ...