Deformation Kinematics of Main Central Thrust Zone(MCTZ)in the Western Himalayas  

作　　者：Mohsin Ahmad Ahanger Ghulam Jeelani 

机构地区：[1]Department of Earth Sciences,University of Kashmir,Srinagar 190006,India

出　　处：《Journal of Earth Science》2022年第2期452-461,共10页地球科学学刊（英文版）

基　　金：the Council of Scientific and Industrial Research(CSIR)New Delhi for supporting this research work by providing the financial assistance in the form of Senior Research Fellowship。

摘　　要：The main central thrust(MCT)is one of the major thrusts in Himalayas.In central Himalaya,MCT was defined as a contact between underlying Lesser Himalayan Sequence(LHS)and overlying higher Himalayan crystallines(HHC).However,in the Kashmir Himalayas,the main central thrust zone(MCTZ),shear zone associated with MCT,is overlain by Kashmir Tethyan Sequence suggesting that the MCTZ has been deformed through a mechanism different than the mechanism responsible for MCTZ evolution in other parts of the Himalayas.In the present study we used structural,microfabric and kinematic analyses to investigate the deformation kinematics of MCTZ.Microstructural investigation revealed that the quartz in orthogneiss mylonites of MCTZ was dynamically recrystallized by grain boundary migration(GBM)and sub-grain rotation recrystallisation(SGR)with top-toSW sense of shear.The mean kinematic vorticity number(W;)just above the thrust ranges from 0.72to 0.84(40%–52%pure shear component)decreasing upwards to 0.65–0.71(35%–50%pure shear component).Deformation in the MCTZ is characterized by Rxzstrain ratio varying from 2.7 to 8.The present study suggested that the MCTZ suffered 3%–40%vertical shortening and 3%–66%transportparallel elongation.The results suggested that the HHC’s were not completely exhumed to the topographic surfaces in the Kashmir Himalayas.Along the basal decollement,i.e.,the main Himalayan thrust(MHT),the deformation continued until MCTZ reached the brittle-ductile transition where deformation mechanism changed to the brittle and the MCTZ rocks were transported to the surface through slip on brittle MCT.

关 键 词：KINEMATICS MYLONITES finite strain mean kinematic vorticity number(Wm) general shear TECTONICS 

分 类 号：P542[天文地球—构造地质学]