Protolith age and exhumation history of metagranites from the Dabie UHP metamorphic belt in east-central China; a multi-chronological study

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Authors:Wang Ru-Cheng; Xu Shi-Jin; Fang Zhong; Shieh, Yuch-Ning; Li Hui-Min; Li Da-Ming; Wan Jing-Lin; Wu Wei-Ping
Author Affiliations:Primary:
Nanjing University, Department of Earth Sciences, Nanjing, China
Other:
Purdue University, United States
Tianjin Institute of Geology and Mineral Resources, China
China Seismological Bureau, China
Anhui Institute of Geology, China
Volume Title:Geochemical Journal
Source:Geochemical Journal, 38(4), p.345-362. Publisher: Geochemical Society of Japan, Nagoya, Japan. ISSN: 0016-7002
Publication Date:2004
Note:In English. 89 refs.; illus., incl. geol. sketch maps, 5 tables, anals.
Summary:Metagranites (granitic orthogneisses) constitute one of the important lithologic units in the Dabie ultrahigh pressure metamorphic belt. They often display direct contact with paragneisses and eclogites. TIMS zircon U-Pb dating on the metagranites reveal that their protolith was crystallized as granitoids in Neoproterozoic ages of 755 to 611 Ma and thus correspond to rift magmatism associated with breakup of the Rodinia supercontinent in the northern margin of the Yangtze Block. Zircon U-Pb age and Ar-Ar ages of amphibole and biotite indicate that the granitoids experienced eclogite-facies metamorphism in Early Mesozoic with rapid exhumation at cooling rates of 8.7 to 10.2°C/Ma from 225±6 to 181±3 Ma in response to amphibolite-facies retrogression. Fission track ages of sphene, zircon and apatite indicate that the metagranites experienced slow exhumation with cooling rates of 0.88 to 1.25°C/Ma in Late Mesozoic. It is possible that in the first period of exhumation, the metagranites were uplifted from the mantle depth to lower crustal level at ca. 225 Ma, then rapidly reached middle to upper crustal levels between 204 Ma and 180 Ma. After the intensive magmatism in Early Cretaceous, the Dabie terrane was uplifted at the slow rate in response to unroofing. Either the rapid exhumation in the Early Mesozoic or the slow uplift in the Late Mesozoic in the Dabie terrane were contemporaneous with two rapid subsidence and sedimentation of the Hefei Basin in Early Jurassic and Paleogene, respectively. This suggests that the orogeny and basin-forming events were closely related to each other rather than independently separated.
Sections:Age determination
Subjects:Absolute age; Amphibole group; Amphibolite facies; Apatite; Ar/Ar; Basins; Biotite; Cenozoic; Chain silicates; Chemical composition; Chronology; Crust; Dates; Eclogite facies; Electron probe data; Exhumation; Facies; Fission tracks; Gneisses; Ion probe data; Isotope dilution; Magmatism; Major elements; Mantle; Mass spectra; Mesozoic; Metagranite; Metaigneous rocks; Metals; Metamorphic rocks; Metamorphism; Metasedimentary rocks; Mica group; Neoproterozoic; Nesosilicates; Orogeny; Orthogneiss; Orthosilicates; Paleogene; Paleozoic; Paragneiss; Phosphates; Plate tectonics; Precambrian; Pressure; Proterozoic; Protoliths; Rare earths; Relative age; Retrograde metamorphism; Rifting; Rodinia; Sedimentation; Sheet silicates; Silicates; Spectra; Subsidence; Terranes; Tertiary; Thermal history; Titanite; Titanite group; Trace elements; U/Pb; Ultrahigh pressure; Uplifts; Upper Mesozoic; Upper Precambrian; Yangtze Plate; Zircon group; Anhui China; Asia; China; Dabie Mountains; Far East; Bixiling China; Dabie Terrane; Hefei Basin; Huangzhen China; Shuanghe China; Xindian China
Coordinates:N302000 N304500 E1163000 E1160000
Abstract Numbers:07M/225
Record ID:2006002212
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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