Alpine metamorphism of low-grade schists from the Slavonian Mountains (Croatia): new P-T and geochronological constraints |
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| Authors: | Dra?en Balen Hans-Joachim Massonne Iva Lihter |
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| Institution: | 1. Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatiadrbalen@geol.pmf.hr;3. Institut für Mineralogie und Kristallchemie, Universit?t Stuttgart, Stuttgart, Germany;4. Department of Geology, Faculty of Science, University of Zagreb, Zagreb, Croatia;5. Earth and Environmental Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada |
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| Abstract: | Low-grade schists from the Slavonian Mountains (Tisia Mega-Unit, Mt Papuk, Croatia), previously assigned to Precambrian to Lower Palaeozoic metamorphism, have been subjected to geochemical investigations, P-T modelling, and in situ age dating of monazite. The studied fine-grained metasediments consist of chlorite (5–15 vol.%), K white-mica (40–55 vol.%), quartz (20–35 vol.%), feldspar (albite 15–20 vol.%), opaques (<2 vol.%), and accessory minerals. According to their whole-rock geochemistry, the detritus of the former sediments came from upper crustal felsic rocks as they occur, for instance, at Mt Papuk. The schists show a complex microtectonic fabric, including well-developed schistosity systems. P-T pseudosections in the system MnNCKFMASHTO, constructed for typical schists of the study area, resulted in peak P-T conditions of 445–465 °C and 4.6–6.0 kbar for a sample from Kutjevo (eastern part of the study area) and 450–460 °C and 5.2–6.0 for a Vranovo sample (western part). Electron microprobe (EMP) dating of monazite in the schists gave a weighted average age of 109.0 ± 13.1 Ma (2σ) eventually with three subgroups of ages at 225 ± 63 (two analyses), 114 ± 24 and 83 ± 22 Ma. We conclude that the metamorphism of the studied schists at depths of c. 20 km is due to an Alpine collisional event. |
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| Keywords: | Cretaceous low-grade metamorphism monazite Slavonian Mountains Tisia Mega-Unit |
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