Structural Characteristics And Tectonic Evolution Of The Luoza-Lakang Area,Tibet

The study area is located in the area from Luoza County to Lakang Town,Shannan City,Tibet,which is in the northern part of the Himalayan block.Under the influence of the continuous collision and subduction of the Indian plate towards the Eurasian continent,intense extrusion and disassembly occur in this area,resulting in complex regional geological and tectonic features.Therefore,the investigation and analysis of the tectonic characteristics and Cenozoic tectonic evolution in this region can provide strong evidence for the study of the Himalayan block.Based on the theory of tectonic geology and petrology,the development of strata,rocks and structures in the study area has been ascertained through field geological survey.The study area mainly involves a secondary geotectonic unit in the Himalayan block.The overall tectonic deformation is manifested as the ductile shear of the northern dome and strong deformation.Brittle normal fault and wide gentle syncline with weak deformation and metamorphism in the middle;South ductile shear deformation.In the research area,the deformation is mainly reflected in the northern strong deformable ductile shear zone and the southern ductile shear zone,which is mainly attributed to the wedge extrusion of the basement complex of the High Himalayas under the continuous extrusion effect,and the separation effect on the north side,forming a large scale north-dipping ductile shear zone in the research area.In the ductile shear deformation zone,rotating broken spots,S-C fabric,flow folds and so on can be seen.Under the influence of disengagement,some thrust faults change into normal faults,and the closer to the ductile disengagement zone and dome,the stronger the deformation becomes.Central tectonic deformation in the study area is relatively weak,mainly for the uplift in the process,and above the earth's crust in the extrusion drape shallow tensile conditions,the study area of nearly east-west brittle normal faults and the north-south normal fault is formed under the action of transverse tension.In addition,the use of electron spin resonance(ESR),the interpretation of the light(OSL)dating methods,such as,quartz morphology,and combined with the existing zircon U-Pb isotope dating as a result,the fracture structure in the latest activity times are analyzed,the results show that the study area in the south of normal fault activity time focused on the latest Pleistocene period,the northern fault the latest activity times concentrated in the early middle Pleistocene.Based on the previous research results,the Cenozoic tectonic activity in the study area is preliminarily divided into three stages: colliding orogenic stage,disengaging and extending stage,and plateau uplifting rift stage.