Lithospheric Electrical Structure Of The Southwestern Margin Of The Tibetan Plateau And Its Dynamic Significance

The Tibetan Plateau located at the southern tip of the Asian continent.Because of its unique topography,topographic features,complex geological structure environment and evolution history,it has attracted the attention of the world's earth science community.The traffic and natural environmental conditions in the middle and east of the Tibetan Plateau are slightly better than those in the west.Therefore,more exploration and research work have been carried out in the past,and there have been a large number of research results.However,the western part of the plateau is a region with intense evolutionary activities,little research has been done.This thesis uses the magnetotelluric sounding method to analyze and study the southwestern part of the Tibetan Plateau(29°N-33°N,80°E-85°E).The data mainly come from the data of the International Deep Profiling of The Tibetan and The Himalayas and the project of Deep Exploration Technology and Experimentation(Sino Probe-01).The phase tensor,impedance tensor and magnetic induction vector of the data are analyzed,and it is considered that the two-dimensional structure is mainly in the study area,and the structural direction is roughly SE110°.There is a three-dimensional effect in the local area of the study area,and the three-dimensionality near the Yarlung Zangbo River suture zone is relatively strongAccording to the structural strike angle obtained by data analysis,two 2D MT profiles were constructed,which were subjected to 2D inversion using Win Glink software.Considering the existence of the three-dimensional influence,the threedimensional inversion of the whole area data was carried out,and the reliability of the obtained electrical model was verified.The study of regional electrical structure model shows that the electrical structure of the southwestern margin of the Tibetan Plateau is characterized by vertical stratification,Generally has the layering characteristics of high resistance-low resistance-high resistance,The shallow electrical structure is mainly characterized by high resistance,which is considered to be the electrical reflection of a large amount of granite in the shallow.The middle and lower crust have obvious low-resistance characteristics and are scattered in a sporadic shape,which is considered to be the result of the partial fusion and salty fluid.After analysis and discussion,the deep high-resistance layer is considered to be the electrical response of The Indian lithosphere.The morphology of the deep high-resistance body was studied and analyzed,and the inconsistency of the morphology of the east-west high-resistivity body in the deep part was obtained,presumably the position of the leading edge of the Indian plate subduction.The high-resistivity body is unevenly distributed from east to west,and the morphological difference reflects the east-west difference of the Indian plate subduction front.From the resistivity model,the high-resistivity body on the south side of the Yarlung Zangbo River suture zone in the central part of the study area is gently inclined to the north,and the subduction distance is large.It is believed that the Indian plates in the study area were relatively gentle and far away from the subduction at 83°E,and crossed the Yarlung Zangbo River suture zone to the north and entered the lower part of the Gangdese-Lhasa block.The high-resistivity bodies in the west of the southwestern margin and the south side of the Yarlung Zangbo River suture zone in the east are steeply inclined to the north,reflecting the greater subduction angle and smaller subduction distance of the Indian plate.81°E and 84°E north-south depth slices show that the leading edge of the high-resistivity body is near the Yarlung Zangbo River suture zone.This difference in subduction may result in the tearing of the Indian plate.