基于短周期密集台阵接收函数揭示的藏南错那洞穹窿地壳结构  

Crustal structure beneath the Cuonadong dome in southern Tibet revealed by receiver functions from a short-period dense array

作　　者：蔡蔚 卢占武[1,3] 黄荣[2,4] 李文辉[1,3] 罗银河[2,4] 王光文[1] 穆青 程永志 陈司 王冠 陈子龙 CAI Wei;LU Zhanwu;HUANG Rong;LI Wenhui;LUO Yinhe;WANG Guangwen;MU Qing;CHENG Yongzhi;CHEN Si;WANG Guan;CHEN Zilong(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Geophysics and Geomatics,China University of Geosciences(Wuhan),Wuhan 430074,China;SinoProbe Laboratory of Ministry of Natural Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(Wuhan),Wuhan 430074,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学(武汉)地球物理与空间信息学院,湖北武汉430074 [3]中国地质科学院自然资源部深地科学与探测技术实验室,北京100037 [4]中国地质大学(武汉)地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《地学前缘》2024年第1期170-180,共11页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(DD20221647);自然资源部深地科学与探测技术实验室开放课题(Sinoprobe Lab:202206);国家自然科学基金项目(91962109,42174124);地质过程与矿产资源国家重点实验室科学技术部专项(MSFGPMR2022-4);湖北巴东地质灾害国家野外科学观测研究站开放基金项目(BNORSG-202214);湖北省自然科学基金联合基金重点项目(2023AFD211)。

摘　　要：位于印度-欧亚板块碰撞前缘的北喜马拉雅构造带,是研究陆陆碰撞过程中地壳增厚和深部岩浆活动的典型区域之一。北喜马拉雅穹窿带作为其中重要的伸展构造,其形成过程与造山运动引起的地壳增厚以及地壳深熔作用引起的地壳流动密切相关。本文以近年新发现的错那洞穹窿为例,利用短周期密集台阵观测,通过远震P波接收函数共转换叠加成像方法获取了错那洞穹窿区域地壳结构。结果表明:错那洞穹窿区域的地壳结构在东西方向上存在差异,壳内速度间断面存在多处不连续现象,局部区域甚至发生界面错断;而在错那裂谷和错那洞穹窿中、上地壳内存在低速区。综合前人研究,本文认为印度-欧亚板块持续碰撞使喜马拉雅东南缘岩石圈经历过地壳尺度拉伸变形。在地壳增厚及持续的高温变质作用下,中、上地壳随藏南拆离系伸展减压发生部分熔融,而熔融岩浆沿着藏南拆离系薄弱处不断上涌并在错那洞穹窿下方聚集,并使错那洞穹窿及错那裂谷中、上地壳弱化,促进区域东西向伸展,进而发生岩浆底辟形成错那洞穹窿。Located at the front edge of the subduction zone,the northern Himalayan tectonic zone is one of the typical regions to study crustal thickening and deep crustal magmatism during continental collision.The northern Himalayan gneiss domes(NHGD),as a critical extensional unit of the tectonic zone,have a formation process closely related to crustal thickening from orogenic movement and crustal flow due to partial melting.In this study,we used common-conversion-point stacking of teleseismic P-wave receiver functions to image the crustal structure beneath the recently discovered Cuonadong dome.We found large crustal structural variations from east to west of the Cuonadong dome with the occurrence of several discontinuous crustal interfaces,even crustal faulting.We also found a low velocity zone in the upper and middle crust beneath the Cona rifts and Cuonadong dome.Combining the above results and previous studies,we consider that the southeastern Himalayan lithosphere underwent crustal-scale tensional deformation as a result of continuing Indo-Eurasian collision.Under the long-term continental subduction,crustal thickening and continuous high-temperature metamorphism,the middle and upper crust underwent partial melting following the extension and decompression of the southern Tibet detachment(STD).The subsequent continuous magma upwelling along the weakened STD and magma accumulation beneath the dome region resulted in the weakened crustal zone,which promoted the east-west regional extension and then formed the Cuonadong dome through magmatic diapirism.

关 键 词：错那洞穹窿 短周期密集台阵 远震P波接收函数 共转换叠加成像 地壳结构 

分 类 号：P315.2[天文地球—地震学]