Characteristics Of Cenozoic Tectonic Deformation And Its Tectonic Significance In Jiangzi-Qusongarea,Southern Tibet

The Tethys Himalayan belt records the process of the expansion and reduction of the Tethys ocean,the collision of the Indian Eurasian plate and the uplift of the plateau since the Late Triassic.However,the study on the characteristics of tectonic deformation and the process of crustal shortening in this belt is relatively low,which directly affects the accurate understanding of the history and mechanism of the whole plateau uplift.In order to solve the relationship between the tectonic framework and deformation characteristics,deformation time and plateau uplift of the Tethys Himalayan belt,this paper takes the middle and eastern parts of the Tethys Himalayan belt as the research object,and conducts detailed structural route survey in the middle part of the Tethys Himalayan belt in gyangzi area and the Eastern part of the Tethys Himalayan belt in Qusong area,The crustal shortening in the middle and eastern part of the Tethys Himalayan belt is estimated by using the balanced section technique.Based on the combination type,distribution,landmark faults and fault cutting relationship of the identified structural systems in the East and west study areas,this paper identifies the structural framework and deformation characteristics of the middle and East segments of the Tethys Himalayan belt,and makes a comparative analysis of the two segments,and then combines the calculation results of crustal shortening in the middle and East segments of the Tethys Himalayan belt,To discuss the influence of different tectonic events on the formation and evolution of the Tethys Himalayan fold and thrust belt,and the relationship between the deformation process and the plateau uplift.The main achievements are as follows(1)The results of field geological survey and structural deformation analysis show that folds and faults are well developed in the middle and eastern parts of the Tethys Himalayan belt.The folds are mainly large oblique inverted folds,accompanied by multiple secondary folds;The fault is characterized by thrust nappe structure from north to south.These folds and thrust faults constitute the fold thrust system and control the structural deformation of the whole structural belt.(2)The recovery of equilibrium section shows that the shortening of the middle Tethyan Himalayan belt is 70 km,with a shortening rate of 53%.Since Cenozoic,the eastern segment of the Tethys Himalayan belt has been shortened by 73 km,with a shortening rate of 49%.These large-scale crustal shortening are caused by the continuous convergence of the Indo Eurasian plate,and lead to the crustal thickening and surface uplift in this area.