喜马拉雅造山带东段错那裂谷的地壳结构  

Crustal structure of the Cona rift,eastern Himalaya

作　　者：吴佳杰 徐啸 郭晓玉 卢占武[3] 吴优 向波 于洋 李春森 余嘉豪 仝霄飞 罗旭聪 WU Jiajie;XU Xiao;GUO Xiaoyu;LU Zhanwu;WU You;XIANG Bo;YU Yang;LI Chunsen;YU Jiahao;TONG Xiaofei;LUO Xucong(School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037,China)

机构地区：[1]中山大学地球科学与工程学院,广东珠海519082 [2]南方海洋科学与工程广东省实验室(珠海),广东珠海519082 [3]中国地质科学院地质研究所,北京100037

出　　处：《地学前缘》2022年第4期221-230,共10页Earth Science Frontiers

基　　金：国家自然科学基金项目(41974097,41874102,U1901214);科学技术部第二次青藏高原综合科学考察研究项目(2019QZKK0701);国家重点研发计划合作研究课题(2016YFC0600301);广东省引进人才创新创业团队“深部地球探测与资源环境团队项目(2017ZT07Z066)”。

摘　　要：喜马拉雅造山带由印度与欧亚大陆板块的陆陆碰撞而形成。为何在挤压造山的碰撞前缘形成代表垮塌的藏南裂谷系存在巨大的争议。回答这个问题需要对裂谷的地壳结构有一个全面的认识。各裂谷带的起始活动年代自西向东逐渐年轻。本研究选取喜马拉雅东部较为年轻的错那裂谷,利用密集台阵接收的远震数据,通过P波接收函数方法,揭示错那裂谷的精细地壳结构,进而通过地壳结构分析裂谷的形成。结果显示错那裂谷为全地壳尺度结构,裂谷下方莫霍面发生明显错断,且壳内结构侧向不连续发育显著。本研究表明裂谷的形成可能关联更大尺度的区域构造运动,单一的重力垮塌是否能形成地壳尺度的裂谷需要进一步研究。综合前人对藏南裂谷系区域的超钾岩和埃达克岩研究以及深部地球物理观测结果,推断因俯冲的印度板片撕裂导致软流圈物质上涌弱化了错那裂谷区域下地壳,并且结合研究区内喜马拉雅淡色花岗岩研究显示中上地壳也存在弱化现象。因此,结合本研究结果推测全地壳尺度裂谷的形成需要不同深度的地壳弱化。The Himalayan mountain range is the result of continental-continental collision between the Indian and Eurasian plates.It has been under great debate as to why the rifts of southern Tibet are formed at the front of the collision zone.To answer this question,it is necessary to understand the crustal structure of the rifts.The age of each rift zone tends to be younger from west to east.In this study,we revealed the crustal structure of the Cona rift,a relatively young continental rift,using the P-wave receiver function calculated from teleseismic data received by a dense array across the rift,and analyzed the rift formation process based on the crustal structure.We showed that the Cona rift is a crustal-scale rift,where Moho offsets beneath the rift and significant lateral variations develops.We suggest that the formation of the rifts may be associated with regional tectonic activities,and further studies are needed to ascertain whether a single gravity collapse can form crustal-scale rifts.Based on the previous studies of magmatic rocks and geophysical observations,we infer that the asthenospheric upwelling caused by tearing of the subducting Indian plate weakened the lower crust of the Cona rift region where the middle and upper crust is also weakened as shown by the study of Himalayan leucogranites.Considering all the study results,we hypothesize that the formation of crustal-scale rift requires crustal weakening at different depths.

关 键 词：错那裂谷 短周期密集台阵 接收函数 地壳弱化 

分 类 号：P315.2[天文地球—地震学]