The multi-stage tectonic evolution of the Xitieshan terrane,North Qaidam orogen,western China: From Grenville-age orogeny to early-Paleozoic ultrahigh-pressure metamorphism |
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| Institution: | 1. State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, School of Earth and Space Science, Peking University, Beijing 100871, China;3. Department of Earth Sciences, Structural Geology and Tectonics, Utrecht University, 3508 TA Utrecht, The Netherlands;1. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;3. Department of Geology, University of Huelva, Huelva 21071, Spain;4. Chang''an University, Xi''an 710054, China;1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, Tianhe District, Guangzhou, China;2. Chengdu Institute of Geology and Mineral Resources, China Geological Survey, Chengdu, Sichuan, China;3. College of Earth Sciences, Guilin University of Technology, Guilin, Guangxi, China;1. CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;2. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;3. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Beijing 100029, China;4. Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an, 710069, China;2. Department of Geology and Geophysics, School of Physical Sciences, The University of Adelaide, South Australia 5005, Australia |
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| Abstract: | The geodynamic evolution of the early Paleozoic ultrahigh-pressure metamorphic belt in North Qaidam, western China, is controversial due to ambiguous interpretations concerning the nature and ages of the eclogitic protoliths. Within this framework, we present new LA-ICP-MS U–Pb zircon ages from eclogites and their country rock gneisses from the Xitieshan terrane, located in the central part of the North Qaidam UHP metamorphic belt. Xitieshan terrane contains clearly different protolith characteristics of eclogites and as such provides a natural laboratory to investigate the geodynamic evolution of the North Qaidam UHP metamorphic terrane. LA-ICP-MS U–Pb zircon dating of three phengite-bearing eclogites and two country rock gneiss samples from the Xitieshan terrane yielded 424–427 Ma and 917–920 Ma ages, respectively. The age of 424–427 Ma from eclogite probably reflects continental lithosphere subduction post-dating oceanic lithosphere subduction at ~ 440–460 Ma. The 0.91–0.92 Ga metamorphic ages from gneiss and associated metamorphic mineral assemblages are interpreted as evidence for the occurrence of a Grenville-age orogeny in the North Qaidam UHPM belt. Using internal microstructure, geochemistry and U–Pb ages of zircon in this study, combined with the petrological and geochemical investigations on the eclogites of previous literature’s data, three types of eclogitic protoliths are identified in the Xitieshan terrane i.e. 1) Subducted early Paleozoic oceanic crust (440–460 Ma), 2) Neoproterozoic oceanic crust material emplaced onto micro-continental fragments ahead of the main, early Paleozoic, collision event (440–420 Ma) and 3) Neoproterozoic mafic dikes intruded in continental fragments (rifted away from the former supercontinent Rodinia). These results demonstrate that the basement rocks of the North Qaidam terrane formed part of the former supercontinent Rodinia, attached to the Yangtze Craton and/or the Qinling microcontinent, and recorded a complex tectono-metamorphic evolution that involved Neoproterozoic and Early Paleozoic orogenies. |
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