西藏高原上地幔的精细结构与构造——地震层析成像给出的启示  

FINE VELOCITY STRUCTURE OF THE UPPER MANTLE BENEATH THE XIZANG PLATEAU FROM TOMOGRAPHY AND ITS GEOLOGICAL INTERPRETATIONS

作　　者：赵文津[1] 薛光琦[2] 吴珍汉[3] 赵逊[1] 刘葵[3] 史大年[2] J.Mechie D.Nelson L.Brown T.Hearn 

机构地区：[1]中国地质科学院 [2]中国地质科学院矿产资源研究所 [3]中国地质科学院地质力学研究所 [4]GeoForchungs Zentrum(GFZ),Potsdam14473,Germany [5]Department of Earth Sciences,Syracuse University,Syracuse,NewYork13244,USA [6]Department of Geological Sciences,Cornell University,Ithaca,NewYork14853,USA [7]Department of Physics,New Mexico State University,LasCruces,NM88003,USA

出　　处：《地球物理学报》2004年第3期449-455,共7页Chinese Journal of Geophysics

基　　金：原地质矿产部;国土资源部基金项目 (950 1 2 0 7) ;美国国家科学基金会资助项目 (grantEAR 961 4 61 6) ;德国研究协会 ;德国地学研究中心的资助项目

摘　　要：利用布置在亚东—格尔木的 1 6 4个流动地震台站记录的 92 6个远震事件的 2 4 2 4 1条射线 ,进行远震P波层析成像处理 ,高分辨率的西藏高原上地幔的速度结构图 ,显示了印度巨厚地幔岩石圈在向高原之下推进的过程中 ,在高喜马拉雅之下拆分成上、下两层 ,这是发生的第一次拆沉 .下层从高喜马拉雅以下约以 2 2°的角度向高原北部插入到 35 0km深 ;而其上层则向北伸展直到雁石坪 ,并构成了高原薄的地幔岩石圈 .在雁石坪北 (33.7°N) ,当其与亚洲大陆岩石圈地幔相遇后发生断离并下沉 .再次证实了五道梁 (35 .2 7°N)深部低速体的存在 ,本区内地壳内低速物质可能与上述运动有联系 。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 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 India 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 Tibetan 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.

关 键 词：西藏高原 上地幔 精细结构 构造 地震层析成像 

分 类 号：P542.5[天文地球—构造地质学]