Steep subduction of the Indian continental mantle lithosphere beneath the eastern Himalaya revealed by gravity anomalies  

作　　者：Shengxian LIANG Xuben WANG Zhengwei XU Yanpei DAI Yonghua WANG Jing GUO Yanjie JIAO Fu LI 

机构地区：[1]Key Laboratory of Earth Exploration and Information Technique,Chengdu University of Technology,Chengdu 610059,China [2]Chengdu Center,China Geological Survey,Chengdu 610081,China

出　　处：《Science China Earth Sciences》2023年第9期1994-2010,共17页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.91755215,42230311,41930112,41902068);the China Geological Survey Project(Grant No.DD20221661).

摘　　要：The geometry and deformation of the Indian continental mantle lithosphere(ICML)beneath the India-Eurasia collision zone are critical to understanding the accommodation of continent-continent convergence.In this paper,the distribution of residual gravity anomalies in the upper mantle of southern Tibet is estimated using the gravity data and seismic velocity models,and the heterogeneous density distribution of the upper-mantle is then recovered through three-dimensional gravity inversion.The results reveal a low-density anomaly(~300 km W-E and~100 km N-S)in the upper mantle under the eastern Himalaya,while there is no obvious density anomaly under the western Himalaya.The western boundary of the low-density anomaly coincides with the Yadong-Gulu Rift(YGR)on the surface(89°–90°E),and its southern boundary is located at~28°N,approximately 130 km southward from the Indus-Yarlung suture,probably representing the mantle suture at depth.This observation indicates that,in contrast to the western ICML which is probably underthrusting at a shallow angle,the eastern ICML be likely subducting steeply,accompanying asthenosphere upwelling.Such a laterally varying geometry suggests that a major tearing of the ICML may have taken place from the intersection of the mantle suture and the YGR in the upper mantle.The tearing and the steep subduction of the ICML might be associated with the magmatic and mineralization events in the eastern Himalaya-Gangdese and the formation of the YGR.

关 键 词：Indian continental mantle lithosphere Steep subduction Mantle suture Major tearing point Upper mantle density Himalaya 

分 类 号：P542.5[天文地球—构造地质学] P312[天文地球—地质学]