Crustal structure across the Altyn Tagh Range at the northern margin of the Tibetan Plateau and tectonic implications |
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| Institution: | 1. Institute of Geology, China Earthquake Administration, Beijing 100029, China;2. College of Energy Resources, China University of Geosciences, Beijing 100083, China;3. School of Earth and Space Science, Peking University, Beijing 100871, China;4. The Department of Geosciences, National Taiwan University, Taipei 10617, ROC;1. Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences, South China Sea Institute of Oceanology, Guangzhou 510301, China;2. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China;3. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China;1. School of Earth Sciences, Zhejiang University, Hangzhou 310027, China;2. Research Center for Structures in Oil and Gas Bearing Basins, Ministry of Education, Hangzhou 310027, China;3. School of Agriculture and Environment, The University of Western Australia, Crawley, Western Australia 6009, Australia;4. Key Laboratory of Submarine Geoscience, Second Institute of Oceanography, State Ocean Administration, Hangzhou 310012, China |
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| Abstract: | We present new seismic refraction/wide-angle-reflection data across the Altyn Tagh Range and its adjacent basins. We find that the crustal velocity structure, and by inference, the composition of the crust changes abruptly beneath the Cherchen fault, i.e., ～100 km north of the northern margin of the Tibetan plateau. North of the Cherchen fault, beneath the Tarim basin, a platform-type crust is evident. In contrast, south the Cherchen fault the crust is characterized by a missing high-velocity lower-crustal layer. Our seismic model indicates that the high topography (～3 km) of the Altyn Tagh Range is supported by a wedge-shaped region with a seismic velocity of 7.6–7.8 km/s that we interpret as a zone of crust–mantle mix. We infer that the Altyn Tagh Range formed by crustal-scale strike-slip motion along the North Altyn Tagh fault and northeast–southwest contraction over the range. The contraction is accommodated by (1) crustal thickening via upper-crustal thrusting and lower-crustal flow (i.e., creep), and (2) slip-parallel (SW-directed) underthrusting of only the lower crust and mantle of the eastern Tarim basin beneath the Altyn Tagh Range. |
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