Deformation And Uplift-Denudation History Of Ganju Lake Area,North Qiangtang Terrane

Qiangtang Basin located in the north of the Tibet Plateau,is located in the north of the Lhasa terrane and the south of the Bayan Hara terrane.Qiangtang Basin has been affected by many tectonic events since Paleozoic,the collision between the Lhasa-Qiangtang block at the end of Mesozoic and the India-Eurasia collision since Cenozoic,have produced a great transformation effect on Qiangtang Basin.However internal tectonic deformation and uplift and denudation history research still exist many disputes currently.According to the above problem,this paper through to the north Qiangtang basin GanJu lake area field geological investigation,divide the tectonic units and study the tectonic deformation characteristics.At the same time using field first-hand information recover the shortening of Jurassic tectonosphere.By means of thermochronology recover the uplift and denudation history of north Qiangtang basin,discuss the relationship between deformation process and plateau uplift.The study area can be subdivided into three tectonic units according to the stratigraphic distribution law,surface fault,fold structure characteristics and combination mode.They are Changhu-Xuelianhu fault-fold belt?Baitanhu-Yanzi hu fault-fold belt?Donghuhu-Chibu fault-fold belt.The faults are mainly EW and NWW thrust faults.Folds occur mostly in Jurassic structures,most are wide-upright fold.By stereographic projection,the stress direction in the study area is mainly NS direction and NEE direction,which is mainly subjected to the extrusion pressure in the north-south direction.According to the first data in the field,the equilibrium section of Jurassic structure in the study area was restored.The Jurassic structure in the north Qiangtang hinterland is shortened by 34 KM and 14.2%.It can be used as the lowest limit of crustal shortening.Apatite fission track shows that the north Qiangtang experienced three uplift processes:60-100Ma?30-40Ma?0-10 Ma.The rate of uplift is also calculated based on the simulation results.The previous two uplift processes were related to the collision between the Lhasa-Qiangtang block at the end of the Mesozoic and the India-Eurasia collision since the Cenozoic.After the second uplift,the Original Tibet Plateau initially reached the same height as today,The third uplift shows that the Tibet Plateau is still in the process of uplift.