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Earth Science Frontiers. 2021, (05) Core

Deepseismic reflection evidence on the deep processes of tectonic construction of the Tibetan PlateauEnglish Full TextEnglish Full Text (MT)

GAO Rui;ZHOU Hui;GUO Xiaoyu;LU Zhanwu;LI Wenhui;WANG Haiyan;LI Hongqiang;XIONG Xiaosong;HUANG Xingfu;XU Xiao;School of Earth Sciences and Engineering,Sun Yat-sen University;Institute of Geology,Chinese Academy of Geological Sciences;Chinese Academy of Geological Sciences;School of Earth Exploration Science and Technology,Jilin University;College of Earth Sciences,Guilin University of Technology;

Abstract: The collision between the Indian and Asian plates uplifted the Himalayan-Tibetan Plateau,thickening and expanding the crust.It is a scientific mystery of global concern as how the two continents collide and how the continent-continent collision deforms the continent.Deep seismic reflection profile detection is one of the most effective ways to unlock this scientific mystery.For more than 20 years using this technology,we have detected fine structures of the thick crust of the Tibetan plateau after overcoming technical bottlenecks to access the lower crust and Moho thus revealing the continental collision processes.This paper systematically summarizes the deep behaviors of the India-Asia collision and subduction beneath the Tibetan Plateau,from south to north,east to west and further into the hinterland of the plateau.The Indian crust undergoes underthrusting beneath the Himalayan orogenic belt on the southern margin of the plateau.Meanwhile,the lithosphere of the Alxa block in the Asian plate subducts southward beneath the Qilian Mountain in the north of the plateau,driving the northward overthrusting of the Qilian crust.Additionally,the Tarim and West Kunlun blocks undergo face-to-face collision in the northwestern margin of the plateau.In the easternmost part of the plateau,the Longriba fault,instead of the Longmen Shan fault zone,marks the western margin of the Yangtze block.It is also seismically evidenced that the Moho geometry in the plateaus hinterland appears thin and flat,indicating lithospheric collapse and extrusion.Multiple deep reflection profiles revealed the collisional behavior under the Yalung-Zangbo suture zone and longitudinal variation in subducting geometry of the Indian crust from west to the east.In the middle of the suture zone,it shows a decoupling between the upper and lower crusts of the Indian plate,where the upper crust undergoes a northward overthrusting while the lower one experiences a northward underthrusting.It is also seismically evidenced a down-and southward crustal duplexing of the subducting Indian crust thickening the northern Himalayas,leaving over a thinning subducting lower crust of the Indian slab.The subduction front of the Indian crust collides with the lower crust of the Asian plate at the mantle depth.A near-vertical collision boundary is seen between the Gangdese batholith and the Tethyan Himalayas,where the Gangdese batholith shows almost transparent weak reflections in the lower crust with localized bright spot reflection that indicates partial melting.Additionally,the near-flat Moho geometry implies an extensional tectonic environment of the southern margin of the Asian plate.
Keywords：

Himalayan-Tibetan Plateau; continent-continent collision; continental underthrusting; deep processes; deep seismic reflection profile;

  • DOI：

    10.13745/j.esf.sf.2021.8.10

  • Series：

    (A) Mathematics/ Physics/ Mechanics/ Astronomy

  • Subject：

    Geology

  • Classification Code：

    P542

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