Amount of Asian lithospheric mantle subducted during the India/Asia collision |
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| Institution: | 1. China Earthquake Networks Center, Beijng, China;2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China;3. Department of Mathematics and Geosciences, University of Trieste, Italy;4. Institute of Geophysics, China Earthquake Administration, Beijing, China;5. International Centre for Theoretical Physics, SAND Group, Trieste, Italy;6. International Seismic Safety Organization, ISSO, Arsita, Italy;1. State Key Laboratory of Biogeology and Environmental Geology, Research Center for Tibetan Plateau Geology, China University of Geosciences (Beijing), Beijing 100083, China;2. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China;3. Department of Earth and Planetary Sciences and Institute of Geophysics and Planetary Physics, University of California, Santa Cruz, CA 95064, USA;4. Department of Geological and Environmental Sciences, Stanford University, CA 94305-2115, USA;5. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China;1. Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095-1567, USA;2. Structural Geology Group, China University of Geosciences (Beijing), Beijing 10085, China;1. Laboratory for Mineralogy and Petrology, Department of Geology, Ghent University, Krijgslaan 281 S8, 9000 Ghent, Belgium;2. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, Sichuan, China;3. Department of Earth Sciences, School of Physical Sciences, The University of Adelaide, SA 5005, Australia;4. Department of Geosciences, University of Arizona, Tucson, AZ, USA |
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| Abstract: | Body wave seismic tomography is a successful technique for mapping lithospheric material sinking into the mantle. Focusing on the India/Asia collision zone, we postulate the existence of several Asian continental slabs, based on seismic global tomography. We observe a lower mantle positive anomaly between 1100 and 900 km depths, that we interpret as the signature of a past subduction process of Asian lithosphere, based on the anomaly position relative to positive anomalies related to Indian continental slab. We propose that this anomaly provides evidence for south dipping subduction of North Tibet lithospheric mantle, occurring along 3000 km parallel to the Southern Asian margin, and beginning soon after the 45 Ma break-off that detached the Tethys oceanic slab from the Indian continent. We estimate the maximum length of the slab related to the anomaly to be 400 km. Adding 200 km of presently Asian subducting slab beneath Central Tibet, the amount of Asian lithospheric mantle absorbed by continental subduction during the collision is at most 600 km. Using global seismic tomography to resolve the geometry of Asian continent at the onset of collision, we estimate that the convergence absorbed by Asia during the indentation process is ~ 1300 km. We conclude that Asian continental subduction could accommodate at most 45% of the Asian convergence. The rest of the convergence could have been accommodated by a combination of extrusion and shallow subduction/underthrusting processes. Continental subduction is therefore a major lithospheric process involved in intraplate tectonics of a supercontinent like Eurasia. |
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