Analysis Of Structural Deformation Characteristics In The Northern Himalayan Block

In the northern part of the Himalayan block,continental-continental collision and extrusion and extensive dismantlement occurred under the continuous compressive force caused by plate subduction,which resulted in the complex and diverse geological conditions in this area.Based on the theory of plate tectonics and the theory of geological tectonics,sedimentary petrology and magmatic petrology,this paper combines the field geological survey results with the previous research results to study and sort out the geological tectonic deformation characteristics of the first-line area from Lacan Town to Zhangda Township in the northern part of the Himalayas Block,and on this basis,makes further comparative analysis of the area.The differences of tectonic levels in different regions are discussed,and the evolution of the present tectonic framework is discussed and analyzed based on the development and evolution of the Yarlung Zangbo Yangtze Ocean by synthesizing the development of the geological structure,sedimentation,magmatism and metamorphism in the study area.The study further deepened the study of the northern part of the Himalayan block,and provided more reference data from the basic geology,in order to provide a basis for understanding the geological tectonic evolution of the New Tethys and Gangdise.Influenced by the subduction and collision of the Indian block and Eurasia continent,the structural characteristics of the thrust nappe in the northern part of the Himalayan block are obvious,forming a series of fold-thrust structures parallel to the strike of the orogenic belt.The main folds and large faults are nearly EW-trending,while the secondary folds and faults are mostly NW-SE-trending.Continuous subduction makes the tectonic deformation in the study area more intense.With the formation of the Himalayan orogenic belt and the emergence and development of the southern Tibetan detachment system,a large number of high-angle normal faults have been bred,and some faults have been transformed from the original thrusting nature to the fault nature,gradually forming the structural deformation characteristics of the south-deep-north-shallow in the study area.The tectonic level and the southern middle-deep tectonic level may be related to the formation of the Himalayan orogenic belt.Based on the comparison of the previous research results,this paper considers that the folds in the northern part of the study area are linear folds,and no coaxial superimposed folds have been found in the detailed field work.In the southern part of the study area,the evidence of individual small faults divided by the former is insufficient,and further research is needed.On this basis,the tectonic evolution history of the study area can be divided into four stages: the extinction stage of the Yarlung Zangbo Ocean,the collision orogeny stage,the extrusion and disintegration stage and the uplift and rift stage of the plateau.The results of previous studies on the evolution of the Yarlung Zangbo River and the Himalayan uplift can be mutually confirmed.