Fine Velocity Structure of the Upper Mantle Beneath the Xizang Plateau from Tomography and Its Geological Interpretations

Abstract

Abstract We use 24241 rays from 926 distant events recorded at 164 portable stations along the line Yadong‐Golmud to perform teleseismic P wave tomography. Our aim is to obtain the velocity structure of the upper mantle beneath the Xizang Plateau with a high resolution. Our result shows that the thick lithospheric mantle of the India plate is divided into two layers beneath the High Himalayas during the underthrusting of the India plate below the plateau, representing the first time of its delamination. The lower layer underthrusts beneath the High Himalayas at a about 22‐ angle northward to depth 350km and the upper layer extends northward to Yanshiping, forming the thin lithospheric mantle below the plateau. North to Yanshiping (33.7‐N), the upper layer of the Xizang mantle fractures and sinks when it meets the lithosphere of the Asia continent. Our result also confirms the existence of a deep low‐velocity body beneath Wudaoliang (35.27‐N). We suggest that this low‐velocity body in the crust may be associated with upwelling of hot materials at depth.