青藏高原东部地块的属性与演化  

Attributes and evolution of the eastern massif in the Qinghai Tibetan Plateau

作　　者：刘晓宇 杨文采 陈召曦[1] 瞿辰[3] 于常青[3] LIU Xiaoyu;YANG Wencai;CHEN Zhaoxi;QU Chen;YU Changqing(School of Geophysics and Information Technology,China University of Geosciences(Beijing),Beijing 100083,China;School of Earth Sciences,Zhejiang University,Hangzhou 310058,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质大学(北京)地球物理与信息技术学院,北京100083 [2]浙江大学地球科学学院,浙江杭州310058 [3]中国地质科学院地质研究所,北京100037

出　　处：《地学前缘》2023年第3期233-241,共9页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(12120113093800)。

摘　　要：利用大量地方地震台站的数据获得了青藏高原地壳上地幔0.5°×0.5°×10 km的高精度三维速度结构,揭示了青藏高原地壳上地幔结构的大量细节,为了解大陆碰撞与高原演化的动力学作用提供了新的证据。根据地震层析成像三维波速数据,计算取得了青藏高原岩石圈底界面深度的三维图,由此发现青藏高原东、西两部属性有本质区别:东部以高波速、较高电阻率和密度的厚岩石圈为主,厚度在150~180 km范围变化;西部以低波速、较低电阻率和密度的薄岩石圈为主,厚度在130~155 km范围变化。上述表明高原东部没有大规模软流圈上涌,而西部发生了大规模软流圈上涌,上涌幅度在20~30 km左右。高原东西部分界线的两个端点坐标分别为(85°E,20°N)和(98°E,40°N)。结合古地磁数据可知,青藏高原东部地块在空间上是40 Ma以来西部陆陆俯冲作用与东南亚洋陆俯冲作用之间的作用力转变的过渡带。Using high-quality seismic data collected from a large number of local seismic stations,we have achieved high-resolution imaging of the three-dimensional velocity structure of the crust and upper mantle in the Qinghai Tibetan Plateau with an accuracy of 0.5°×0.5°×10 km,which revealed in great detail the crustal and upper mantle structure of the Qinghai Tibetan Plateau and provided new evidence for understanding the dynamics of continental collision and plateau evolution.Then,based on the 3D seismic P-wave velocity data,a 3D depth map of the lithosphere-asthenosphere boundary beneath the Qinghai Tibetan Plateau is obtained.It is found that there are fundamental differences in geological attributes between the eastern and western parts of the plateau:The eastern part is dominated by thick lithosphere with high wave velocity,high resistivity and density,and a thickness range of 150180 km;whereas the west is dominated by thin lithosphere with low wave velocity,low resistivity and density,and thickness ranging between 130155 km.Furthermore,there is no large-scale asthenospheric upwelling in the eastern part whereas~2030 km upwelling has occurred in the west.The coordinates of the two endpoints of the east-west boundary are(20°N,85°E)and(40°N,98°E)respectively.According to the paleomagnetic data,the eastern massif in the Qinghai Tibetan Plateau is a stress transition zone situated between the western continent-continent subduction zone and Southeast Asia ocean-continent subduction zone since 40 Ma.

关 键 词：青藏高原 东部地块 地震层析成像 岩石圈底界面 属性演化 

分 类 号：P313.1[天文地球—固体地球物理学]