Characterization of polymetamorphism in the Austroalpine basement east of the Tauern Window using garnet isopleth thermobarometry |
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Authors: | F GAIDIES R ABART C DE CAPITANI R SCHUSTER J A D CONNOLLY E REUSSER |
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Institution: | Department of Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel, Switzerland (); Institute of Geological Sciences, Free University of Berlin, Malteserstrasse 74-100, D-12249 Berlin, Germany; Geological Survey of Austria, Neulinggasse 38, A-1031 Vienna, Austria; Earth Sciences Department, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland |
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Abstract: | Garnet in metapelites from the Wölz and Rappold Complexes of the Austroalpine basement east of the Tauern Window typically shows two distinct growth zones. A first garnet generation usually forms the cores of garnet porphyroblasts and is separated by a prominent microstructural and chemical discontinuity from a second garnet generation, which forms rims of variable width. Whereas the rims were formed during the Eo-Alpine metamorphic overprint, the garnet cores represent remnants of at least two pre-Eo-Alpine metamorphic events. The pressure and temperature estimates obtained from garnet isopleth thermobarometry applied to the first growth increments of the pre-Eo-Alpine garnet cores from the Wölz and Rappold Complexes cluster into two distinct domains: (i) in the Wölz Complex, incipient growth of the first-generation garnet occurred at 4 ± 0.5 kbar and 535 ± 20 °C, (ii) in the Rappold Complex, incipient growth of the oldest garnet cores took place at 5.3 ± 0.3 kbar and 525 ± 15 °C. The Eo-Alpine garnet generation started to grow at 6.5 ± 0.5 kbar and 540 ± 10 °C. According to radiometric dating, the low-pressure garnet from the Wölz complex was formed during a Permian metamorphic event. The first-generation garnet of the Rappold Complex is probably of Variscan age. |
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Keywords: | Austroalpine basement garnet metapelite Rappold Complex Wölz Complex |
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