Exhumation of subducted continental crust along the arc region |
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| Institution: | 1. Czech Geological Survey, 11821 Praha 1, Czech Republic;2. Université de Strasbourg, CNRS, Institut de Physique du Globe de Strasbourg, UMR 7516, 67084 Strasbourg, France;3. Institute of Geophysics ASCR, v.v.i., Boční II/1401, Prague 4 14131, Czech Republic;4. Department of Earth Science, University of California, Santa Barbara, CA 93106, USA;1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 210023 Nanjing, China;2. Geological Institute Russian Academy of Sciences, Pyzhevskiy per. 7, Moscow, 119017, Russia;3. Geological Department Sankt Petersburg State University, University Embankment 7/9, Sankt-Petersburg, 199034, Russia;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China;2. College of Geoscience, China University of Petroleum, Beijing, China;3. Key Laboratory of Tectonics and Petroleum Resources of the Ministry of Education, School of Earth Resources, China University of Geosciences, Wuhan, China;4. Energy & Geoscience Institute, University of Utah, Salt Lake City, UT, USA;5. Unconventional Petroleum Research Institute, China University of Petroleum, Beijing, China;6. Centre for Earth Sciences, Indian Institute of Science, Bangalore, India;7. School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, China;8. Department of Earth Sciences, University of Adelaide, SA 50005, Australia;9. Earth Dynamics Research Group, TIGeR (The Institute of Geoscience Research), Department of Applied Geology, Curtin University, Perth, Australia;10. Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, USA;11. Department of Computer Science, University of Idaho, Moscow, ID, 83843, USA;1. Institute of Geological Sciences, Polish Academy of Sciences, Warsaw, Poland;2. Faculty of Earth Sciences, University of Silesia in Katowice, Sosnowiec, Poland;3. School of Earth and Planetary Sciences, Curtin University, Perth, Australia;4. Korea Basic Science Institute (KBSI), Ochang Campus, Republic of Korea |
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| Abstract: | The Kutná Hora crystalline complex (KHCC) in the Bohemian Massif is a HP/HT complex adjacent to the magmatic arc. It is dominated by migmatite, orthogneiss and granulite with bodies of eclogite and peridotite. The KHCC migmatite consists of K-feldspar, plagioclase, quartz, phengite, biotite, garnet and kyanite. Melting conditions were estimated at 780 °C and >16 kbar and inferred melt volume varies between 1 and 4 vol%. Peak temperature is 865 °C at 18–19 kbar followed by decompression in the presence of melt to 12–13 kbar and 770–800 °C. U-Pb monazite geochronology reveals a spread of ages between 550 Ma and 330 Ma. REE patterns show low Yb/Gd for 550–500 Ma, high Yb/Gd for ages at ~480 Ma, and decreasing Yb/Gd towards ~340 Ma. First monazite in equilibrium with garnet constrains the HP metamorphism to ~350 Ma, which is followed by recrystallization of monazite down to 325 Ma. U-Pb zircon geochronology displays an age range from ~670 Ma to ~430 Ma. The broad age range records a span of protolith crystallization and/or old metamorphism. The presence of HP ky + mu migmatite, their P–T path, protolith zircon and monazite metamorphic ages and whole-rock geochemistry are similar to HP migmatites in the Eger crystalline complex (ECC) in the Saxothuringian domain further in the west. We propose the following geodynamic scenario for subduction-relamination-exhumation mechanism: (i) subduction of the Saxothuringian continental lithosphere at 360 Ma related to early stage of trans-lithospheric diapirism triggered by arc-related magma weakening; (ii) large-scale emplacement of relaminant into the upper plate lithosphere at 350–340 Ma; and (iii) return flow of the relaminant along the subduction interface (the ECC) and emplacement of relaminant in the upper–middle crust in the rear part of the arc system (the KHCC) at 340–330 Ma. |
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