Geochronological evidence for two-stage metamorphism of metagranitoids in the Dabie ultrahigh pressure metamorphic belt and exhumation of the orogenic zone

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Authors:Fang Zhong; Xu Shijin; Wang Rucheng
Author Affiliations:Primary:
Nanjing University, Department of Earth Sciences, Nanjing, China
Volume Title:Kuangwu Yanshi Diqiuhuaxue Tongbao Bulletin of the Chinese Society of Mineralogy, Petrology and Geochemistry
Source:Kuangwu Yanshi Diqiuhuaxue Tongbao = Bulletin of the Chinese Society of Mineralogy, Petrology and Geochemistry, 20(4), p.256-258. Publisher: Academica Sinica, Institute of Geochemistry, Guiyang, China. ISSN: 1007-2802
Publication Date:2001
Note:In Chinese with English summary
Summary:Metagranitoids in the Dabie ultrahigh pressure metamorphic belt are often associated with coesite-bearing eclogites. TIMS zircon U-Pb dating of the rocks shows that their protoliths were late Proterozoic (755-714 Ma) granitoids; they were then strongly metamorphosed in two periods during the Paleozoic (384-284 Ma) and Early Mesozoic (224.5-97 Ma). Ar/Ar ages of amphibole, muscovite and biotite and fission track (FT) ages of sphene, zircon and apatite indicate the metagranitoids formed and developed during the first rapid exhumation process after early Mesozoic deep-subduction metamorphism from 224.5 Ma to 180.8 Ma. The corresponding cooling rates of the rocks were 10.2 °/Ma (Shuanghe block) and 26.6 °/Ma (Bixiling block), respectively. The second rapid uplift movement, which started from 53.4 Ma (Shuanghe block) and 57 Ma (Bixiling block) to 50 Ma and 53.6 Ma, was more rapid than the first; cooling rates were 28.2 °/Ma and 32.39 °/Ma, respectively. The modern orographic shape of the Dabie orogenic belt appeared in an embryonic form as early as 50 Ma. [J.F.]
Subjects:Absolute age; Ar/Ar; Dates; Exhumation; Lower Mesozoic; Mesozoic; Metagranite; Metaigneous rocks; Metamorphic belts; Metamorphic rocks; Metamorphism; Neoproterozoic; Orogenic belts; Paleozoic; Polymetamorphism; Precambrian; Pressure; Proterozoic; Tectonics; U/Pb; Ultrahigh pressure; Upper Paleozoic; Upper Precambrian; Asia; China; Dabie Mountains; Far East; Bixiling Block; Shuanghe Block
Coordinates:N283000 N320000 E1172000 E1140000
Abstract Numbers:02M/2828
Record ID:2005052311
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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