Late Triassic crustal growth in southern Tibet: Evidence from the Gangdese magmatic belt |
| |
| Institution: | 1. State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Department of Earth Sciences, University of Adelaide, SA 5005, Australia;3. School of Earth Sciences and Resources, China University of Geosciences (Beijing), 29 Xueyuan Road, Beijing 100083, China;4. Faculty of Science, Kochi University, Akebono-cho 2-51, Kochi 780-8520, Japan;5. State Key Laboratory Breeding Base of Nuclear Resources and Environment, East China Institute of Technology, Nanchang 330013, China;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Department of Earth and Environmental Sciences, Università di Milano-Bicocca, 20126 Milan, Italy;3. State Key Laboratory of Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;4. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China;1. School of Earth Sciences, Gansu Key Laboratory of Mineral Resources in Western China, Lanzhou University, Lanzhou 730000, PR China;2. Chengdu Institute of Geology and Mineral Resources, Chinese Geological Survey, Chengdu 610081, PR China;3. Institute of Multipurpose Utilization of Mineral Resources, Chinese Academy of Geological Sciences, Chengdu 610041, PR China;1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100082, PR China;2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China;3. Laboratory of Department of Thermal Engineering, Tsinghua University, Beijing 100084, PR China;1. College of Earth Sciences, Jilin University, Changchun, 130061, China;2. Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China, Changchun 130061, China |
| |
| Abstract: | The Gangdese magmatic belt, located in the southern margin of the Lhasa terrane and carrying significant copper and polymetallic mineralization, preserves important information relating to the tectonics associated with Indian–Eurasian collision and the crustal growth of southern Tibet. Here we investigate the Quxu batholith in the central domain of the Gangdese magmatic belt and report the occurrence of hornblende gabbros for the first time. We present petrologic, zircon U–Pb–Hf isotopic and bulk-rock chemistry data on these rocks. The hornblende gabbros display sub-alkaline features, and correspond to tholeiite composition. They also show medium K calc-alkaline to low K affinity. The rocks show enrichment in LILEs and LREEs, but are depleted in HFSEs, indicating a subduction-related active continental margin setting for the magma genesis. Our computations show that the gabbroic pluton was emplaced in the middle-lower crustal depth of ca. 18 km. Zircons from the hornblende gabbros yield crystallization age of ca. 210 Ma, revealing a late Triassic magmatic event. Combined with available data from the Gangdese magmatic belt, our study suggests that the northward subduction of the Neo-Tethys oceanic crust beneath the southern margin of the Lhasa terrane might have been initiated not later than the Norian period of Triassic. Zircons from the hornblende gabbro show positive εHf(t) values of 9.56 to 14.75 (mean value 12.44), corresponding to single stage model ages (TDM1) in the range of 256 Ma to 459 Ma, attesting to crustal growth in the southern Lhasa terrane associated with the subduction of the Neo-Tethys oceanic crust. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
