Indian plate blocked by the thickened Eurasian crust in the middle of the continental collision zone of southern Tibet  

作　　者：Gaochun Wang Xiaobo Tian Yibing Li Tao Xu Bo Wan Yi Chen Shitan Nie Xusong Yang Sicheng Zuo Jianli Zhang 

机构地区：[1]State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China [2]Geothermal and Ecological Geology Research Center,School of Ecology and Environment,Zhengzhou University,Zhengzhou,450001,China [3]Innovation Academy for Earth Science,CAS,Beijing,100029,China [4]Frontiers Science Center for Deep Ocean Multispheres and Earth System,Institute for Advanced Ocean Study,Ocean University of China,Qingdao,266100,China [5]Laboratory for Marine Mineral Resources,Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao,266237,China

出　　处：《Earthquake Research Advances》2023年第3期42-52,共11页地震研究进展（英文）

基　　金：supported by the National Key R&D Program of China (Grant No. 2016YFC0600301);the National Natural Science Foundation of China (Grant 42030308, 41974053, and 41888101)

摘　　要：The relationship of the crustal contact between the Indian and Eurasian plates is a key issue in understanding crustal thickening and the subduction of the Indian lithosphere beneath the Qinghai-Tibetan Plateau. Across the middle of the Yarlung-Zangbo Suture(YZS), we deployed an ~450-km-long SN-trending wide-angle reflection/refraction profile to observe the P-wave velocity(vP) structure beneath the northern Himalaya and the southern plateau. Our results show that, 1. the high vP(~7.1 km/s) indicates that the Indian lower crust extends no more than 50 km north of the YZS. 2. The lower crust beneath the southern part of the plateau features an extremely low vP(<6.7 ± 0.2 km/s). 3. Compared with the velocities of several typical crustal lithologies in different temperature regimes, the low vPin the lower crust can be explained by felsic-intermediate granulite, which has prevented the lower crust from further eclogitization. We propose that the dip angle of the Indian lithospheric slab beneath the YZS is partly controlled by the composition of the lower crust of the plateau. In the northern middle YZS, the crust of the southern plateau is too thick and blocks the northward advancement of the Indian lower crust, resulting in the subduction of the Indian lithospheric slab into the upper mantle. The lower crust in western and eastern Lhasa is dominated by a mafic composition, and it was delaminated after eclogitization before the Miocene. The void zone generated by delamination favors the flattening and underthrusting of the Indian lower crust.

关 键 词：Qinghai-Tibetan Plateau Indian lithospheric slab Wide-angle reflection/refraction Crustal P-wave velocity structure Crustal thickening 

分 类 号：P542[天文地球—构造地质学]