Structure Of The Crust And Upper Mantle Along The NS Profile In The Eastern Section Of The Yarlung Zangbo Suture Zone

The continuous collision between the Indian plate and the Eurasian plate creates the world's largest and highest plateau—the Tibetan Plateau.The Yarlung Zangbo suture zone is a long and narrow front joint along the Yarlung Zangbo Valley.It has undergone intense deformation and metamorphism during the collision between the Indian plate and the Asian plate.It is considered as the relic of the Neo-Tetyan main ocean basin.The Yajiang suture zone is regarded as a natural laboratory for the study of deep tectonics in the continental collision.A great amount of studys have been carried out in this area by researchers from all over the world.However,there are still controversies as what does the crust and upper mantle look like,what's the Indian mantle lithosphere subduction pattern,what is the metallogenic model in the shallow and so on.Thus we still need a lot of observation and interpretation to obtain a better understanding of the Tibetan plateau and make a good use of it.This article aims to explore the underground geologic structure beneath the East-ern Section of the Yarlung Zangbo suture zone,in where a 200 km long seismic profile was located by Jilin University.20 broadband stations were set up for 1.5 years,and the distance between the stations is 10 km.The main goal of the project is solving four sci-entific questions:(1)What does the crustal structure beneath the Yarlung Zangbo suture zone look like?(2)Dose the Indian plate lithosphere which subducted into the hinter-land of the plateau reach the mantle transition zone? Dose it still maintain a whole?Is there some kind of pattern such as tearing apart?(3)Are there great differences in lithospheric structure between the south and the north block of the Yarlung Zangbo suture zone?(4)What is the deep geological structure for the origin of the Gangdise metallogenic belt?Receiver functions analysis and teleseismic tomography technique are conducted using seismic data recorded by the stations.P receiver functions and S receiver func-tions are calculated.The crustal structure in a high resolution and clear Moho interface are obtained by Common Conversion-point Stacking(CCP)profile of P receiver func-tions.S-wave velocity structure is also obtained by the join inversion of P receiver functions and surface wave including phase and group velocity dispersion data.CCP profile of P receiver functions also displays interfaces in the depth of 410 km and 660 km.Lithosphere Asthenosphere Boundary(LAB)can be clearly seen on the profile of S receiver functions' CCP profile.The velocity anomalies beneath the profile are obtained by teleseismic wave tomography.The study finally yielded five insights:(1)The Indian continental crust dose not underthrust into the Lhasa crust,but is blocked by Lhasa terrane and stopped near the Yajiang suture zone.(2)Low-velocity zone is widely distributed in the middle and up-per crust with continuous but inconsistent thickness.(3)There are high-speed interfaces along the Moho,the southern part is interpreted as the main Himalayan thrust(MHT)whereas the northern part is interpreted as the juvenile lower crust formed by the up-welling of mantle magma.(4)The Indian lithosphere is partially torn while subducting,leading to the upwelling of hot materials belonging to the deep asthenosphere,which may be the main source of ore-forming magma in the Gangdese metallogenic belt.(5)Parts of the Indian lithosphere are delaminated,the delaminated mantle lithosphere and some of the torn plates may have entered the mantle transition zone and caused its ab-normal thickening.