Incremental emplacement and syn-tectonic deformation of Late Triassic granites in the Qinling Orogen: Structural and geochronological constraints |
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| Institution: | 1. Key Lab of Submarine Geosciences and Prospecting Techniques, MOE, Institute for Advanced Ocean Study, College of Marine Geosciences, Ocean University of China, Qingdao 266100, China;2. Laboratory for Marine Geology and Environment, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;3. State Key Laboratory of Continental Dynamics, Northwest University, Xi''an 710069, China;4. Tianjin North China Geological Exploration Bureau, Tianjin 300170, China;5. UCD School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland;1. Wuhan Center of Geological Survey, China Geological Survey, Wuhan 430205, China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Department of Earth and Environmental Sciences, University of Windsor, Ontario, Canada;4. State Key Lab of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;5. Key Laboratory of Marine Hydrocarbon Resources Environmental Geology, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;6. Key Laboratory of Depositional Mineralization & Sedimentary Minerals, Shandong University of Science and Technology, Qingdao 266590, China;7. School of Earth Sciences, China University of Geosciences Wuhan, Wuhan 430074, China;1. School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;3. Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Wuhan 430074, China;4. Tianjin Branch, China Petroleum Logging CO. LTD., Tianjin 300457, China;5. School of Ocean and Earth Science, Tongji University, Shanghai 200092, China;6. Wuxi Research Institute of Petroleum Geology, Petroleum Exploration and Development Research Institute, SINOPEC, Wuxi 214126, China;7. Research Institute of Exploration and Development, Xinjiang Oilfield Company, PetroChina, Urumqi 830013, China;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Northern Taibai Str. 229, Xi''an 710069, China;2. Department of Earth Science, Western University, 1151 Richmond Str., London, Ontario N6A 3K7, Canada;3. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China;4. College of Geosciences and Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450045, China;1. Shenyang Center of Geological Survey, China Geological Survey, Shenyang, Liaoning, China;2. College of Earth Sciences, Jilin University, Changchun, China;3. Key Lab of Submarine Geoscience and Prospecting Techniques, MOE, Institute for Advanced Ocean Study, College of Marine Geosciences, Ocean University of China, Qingdao, China;1. School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;2. Institut für Mineralogie und Kristallchemie, Universität Stuttgart, Stuttgart 70174, Germany |
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| Abstract: | Granitoids are important components of major orogenic belts, and provide important information about the regional geodynamic evolution. The emplacement mechanism of granite plutons and its relationship with regional tectonics has long been discussed, although it still remains debated. The Qinling Orogen within the Central China Orogen was marked by the emplacement of numerous Late Triassic granitic plutons. Although the petrology, geochemistry and geochronology of these intrusions have been addressed in various studies, their tectonic setting remains controversial, particularly since the structural aspects not been evaluated in detail. In this study, we attempt to reconstruct the emplacement process of the Late Triassic Dongjiangkou pluton in the South Qinling Belt. Field observations show extensive syn-plutonic deformations both in the pluton and its contact zones. Microstructural observations demonstrate that fabrics in the pluton were mainly acquired during submagmatic flow to high-T solid-state deformation. Zircon U–Pb ages reveal that the pluton is a composite intrusion which is composed of two juxtaposed small plutons with distinct ages (~210 Ma and ~200 Ma). Al-in-hornblende thermobarometer indicates that the pluton was formed at depths ranging from 4.7 km to 8.8 km, with an increasing depth trend from the inner unit to the outer unit. Distribution of the internal fabrics shows two concentric patterns which are concordant with pluton margins at the pluton scale and were probably induced by the regional sinistral transpression. Integrating these analyses, an incremental emplacement model is proposed for the syn-tectonic pluton. This model not only solves the ‘room problem’ but also accounts for the zoned petrological features of the pluton. Combined with previous studies, we suggest that the Late Triassic granite plutons in the Qinling Orogen were emplaced under a syn-collisional convergence setting, and that the granite magmatism was probably controlled by regional tectonics. Additionally, the incremental emplacement model may be a common mechanism for the Late Triassic granite plutons. |
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