| Polymetamorphism of the Variscan Basement of the Moldanubian Black Forest （Germany） Documented in Zircon and Garnet Minerals from Gneisses |
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| 引用本文： | 陈福坤.Polymetamorphism of the Variscan Basement of the Moldanubian Black Forest （Germany） Documented in Zircon and Garnet Minerals from Gneisses[J].中国地球化学学报,2002,21(2):107-119. |
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| 作者姓名： | 陈福坤 |
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| 作者单位： | InstitutfuerMineralogie,PetrologieundGeochemie,UniversitaetTuebingen |
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| 摘 要： | High-grade metamorphic Variscan basement is exposed in the Moldanubian zone of the Black Forest (BF), being the internal zone of the European Variscan belt. Zircon grains from K-rich felsic orthogneisses and an anatectic paragneiss in the Moldanubian Black Forest demonstrate a multi-stage crystallization at ～ 600 Ma, ～ 480 Ma, ～ 400 - 380 Ma, and ～350 Ma. The last three stages of crystallization probably represent metamorphic overprint during pre-Variscan and Variscan metamorphism.Using stepwise leaching procedures, garnet minerals from felsic orthogneisses as well as paragneisses in the Moldanubian Black Forest yielded Early Carboniferous Sm-Nd ages (～ 330- 340 Ma), which are consistent with the well-constrained Variscan HT metamorphic event,and Early Palaeozoic ( ～480 Ma) to Devonian ( ～400 - 370 Ma) Pb-Pb ages. The coincidence of growth time for zircon and garnet minerals at Early Palaeozoic is interpreted as dating a metamorphic event. These garnet data demonstrate that the Moldanubian BF basement underwent at least two metamorphic events during the Early Palaeozoic and Early Carboniferous.During the Variscan HT metamorphism, the Sm-Nd system of garnet was disturbed, but not the U-Pb system, implying the peak metamorphic temperature was lower than ～800℃.
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| 关 键 词： | 铅同位素定年 锆石 石榴石 变质作用 德国 |
| 收稿时间： | 20 February 2003 |
Polymetamorphism of the Variscan basement of the Moldanubian Black Forest (Germany) documented in zircon and garnet minerals from gneisses |
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| Chen Fukum.Polymetamorphism of the Variscan basement of the Moldanubian Black Forest (Germany) documented in zircon and garnet minerals from gneisses[J].Chinese Journal of Geochemistry,2002,21(2):107-119. |
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| Authors: | Chen Fukum |
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| Institution: | 1. Institut für Mineralogie, Petrologie und Geochemie, Universit?t Tübingen, Wilhelmstrasse 56, 72074, Tübingen, Germany
2. Institute of Geology and Geophysics, Chinese Academy of Sciences, 100029, Beijing, China
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| Abstract: | High-grade metamorphic Variscan basement is exposed in the Moldanubian zone of the Black Forest (BF), being the internal zone
of the European Variscan belt. Zircon grains from K-rich felsic orthogneisses and an anatectic paragneiss in the Moldanubian
Black Forest demonstrate a multi-stage crystallization at ∼600 Ma, ∼480 Ma, ∼400–380 Ma, and ∼350 Ma. The last three stages
of crystallization probably represent metamorphic overprint during pre-Variscan and Variscan metamorphism.
Using stepwise leaching procedures, garnet minerals from felsic orthogneisses as well as paragneisses in the Moldanubian Black
Forest yielded Early Carboniferous Sm-Nd ages (∼330–340 Ma), which are consistent with the well-constrained Variscan HT metamorphic
event, and Early Palaeozoic (∼480 Ma) to Devonian (∼400–370 Ma) Pb-Pb ages. The coincidence of growth time for zircon and
garnet minerals at Early Palaeozoic is interpreted as dating a metamorphic event. These garnet data demonstrate that the Moldanubian
BF basement underwent at least two metamorphic events during the Early Palaeozoic and Early Carboniferous. During the Variscan
HT metamorphism, the Sm-Nd system of garnet was disturbed, but not the U-Pb system, implying the peak metamorphic temperature
was lower than ∼800°C.
This study was supported by the Deutsche Forschungsgemeinschaft (DFG) within the priority program “Orogene Prozesse”. |
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| Keywords: | Variscan Moldanubian Black Forest zircon and garnet ages metamorphism |
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