Zircon U–Pb geochronology of the Mesozoic metamorphic rocks and granitoids in the coastal tectonic zone of SE China: Constraints on the timing of Late Mesozoic orogeny |
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| Institution: | 1. Chinese Academy of Geological Sciences, Beijing 100037, China;2. China Deep Exploration Center-SinoProbe Center, China Geological Survey & Chinese Academy of Geological Sciences, Beijing 100037, China;3. Stake Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;2. School of Earth and Ocean Sciences, University of Victoria, PO Box 1700, STN CSC, Victoria, BC V8W 2Y2, Canada;1. Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan 430074, China;2. Shenzhen Branch of the China National Offshore Oil Corporation, Shenzhen 518000, China;3. Fault Analysis Group, School of Earth Sciences, University College Dublin, Dublin, Ireland |
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| Abstract: | The coastal Changle-Nan’ao tectonic zone of SE China contains important geological records of the Late Mesozoic orogeny and post-orogenic extension in this part of the Asian continent. The folded and metamorphosed T3–J1 sedimentary rocks are unconformably overlain by Early Cretaceous volcanic rocks or occur as amphibolite facies enclaves in late Jurassic to early Cretaceous gneissic granites. Moreover, all the metamorphic and/or deformed rocks are intruded by Cretaceous fine-grained granitic plutons or dykes. In order to understand the orogenic development, we undertook a comprehensive zircon U–Pb geochronology on a variety of rock types, including paragneiss, migmatitic gneiss, gneissic granite, leucogranite, and fine-grained granitoids. Zircon U–Pb dating on gneissic granites, migmatitic gneisses, and leucogranite dyke yielded a similar age range of 147–135 Ma. Meanwhile, protoliths of some gneissic granites and migmatitic gneisses are found to be late Jurassic magmatic rocks (ca. 165–150 Ma). The little deformed and unmetamorphosed Cretaceous plutons or dykes were dated at 132–117 Ma. These new age data indicate that the orogeny lasted from late Jurassic (ca. 165 Ma) to early Cretaceous (ca. 135 Ma). The tectonic transition from the syn-kinematic magmatism and migmatization (147–136 Ma) to the post-kinematic plutonism (132–117 Ma) occurred at 136–132 Ma. |
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