Late Carboniferous seismic and volcanic record in the northwestern margin of the Junggar Basin: Implication for the tectonic setting of the West Junggar |
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| Institution: | 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. Chengdu Centre, China Geological Survey, Chengdu 610081, China;2. Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China;3. Southwest Petroleum University, School of Geoscience and Technology, Chengdu 610500, China;4. Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Department of Geology, School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China;5. China Deep Exploration Center, Chinese Academy of Geological Sciences, Beijing 100037, China;1. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China;2. Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China;3. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, China;4. School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China;5. Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;6. CAS Center for Excellence in Tibetan Plateau Earth Sciences, The Chinese Academy of Sciences, Guangzhou 510640, China;1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. Xinjiang Research Center for Mineral Resources, Chinese Academy of Sciences, Urumqi 830011, China;3. Xinjiang Bureau of Geology and Mineral Resources, Urumqi, Xinjiang 830000, China;1. Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation, Ministry of Land and Resources, Chengdu University of Technology, Chengdu, Sichuan, China;2. School of Earth Sciences, China University of Geosciences, Wuhan, Hubei, China;3. Geological Survey of Western Australia, Perth, Western Australia, Australia;4. Centre for Exploration Targeting, University of Western Australia, Perth, Western Australia, Australia |
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| Abstract: | The northwestern margin of the Junggar Basin is a transition zone between the Zaire-Hala'alate mountains and the Junggar Basin in West Junggar, which developed a large amount of volcanic rocks in the late Carboniferous. An investigation of the tectonic evolution of this area will be helpful for understanding the accretionary process of West Junggar. Here, we selected well-preserved drill core samples of andesite and andesitic tuff for detailed petrogenesis and geochemical studies, while high-quality seismic and resistivity prospecting cross-sections were also used to reveal the tectonic setting. Zircon U-Pb dating results of three andesite and andesitic tuff samples show that these rocks were erupted at ca. 312 Ma. The results of the geochemical and isotopic analyses of seven samples are characterized by relatively high MgO (1.84–5.52 wt%), Cr (26.19–246.61 ppm), Ni (16.53–82.85 ppm) contents, Ba/La (14.19–218.48) ratios, and high positive ?Hf(t) (+4.8 to +14.2) values, but low TiO2 (0.68–1.25 wt%) contents, FeOT/MgO (1.18–2.81), Sr/Y (5.63–27.40), and Th/Yb (0.19–2.18) ratios, which are similar to the Bieluagaxi sanukitoids of West Junggar. LREEs are enriched in all samples, while Nb and Ta are significantly depleted. All the evidence suggests the volcanics were most likely derived from partial melting of oceanic slab that was contaminated by the overlying mantle wedge during the magma ascent. The seismic and resistivity cross-sections show apparent southeastward-vergent imbricate thrust fault systems, implying northwestward subduction in the late Carboniferous. Together with previous studies and our geochemical and geophysical data, we suggest that the formation of these late Carboniferous volcanic rocks is probably related to a northwestward ridge subduction process. |
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