Material Composition And Tectonic Evolution Of The Erqis Tectonic Mixed Zone In The Altai Xibodu Area,Xinjiang

The Ertzis tectonic mixed belt is located at the boundary between the Junggar plate and the Siberian plate.And it is an important part of the Central Asian orogenic belt.Based on field surveys and collection of related data on the Ertzis tectonic mixed zone in the Tikeniket,this article focuses on the material composition,structural structure,and evolution process of the mixed rock zone by useing other theoretical foundations such as petrology,rock geochemistry,and isotope chronology.The material composition in Erzis tectonic mixed zone is mainly divided into rock block and matrix.Based on the combination of rock block characteristics,deformation characteristics,and contact relationships,the rock blocks are further subdivided into five types of rock blocks,namely,diabase rock blocks,metamorphic basalt rock blocks,siliceous rock blocks,gneiss rock blocks and oblique long-angle dischist block.The matrix is mainly composed of metamorphic sandstone,metagranite and schist.The matrix is distributed around the rock blocks,showing "net-like" features of varying scales,in which the rock blocks are mainly distributed in the form of lenses.The diabase rocks in the Erzis tectonic mixed zone show the environmental characteristics of volcanic island arcs during subduction.The original rock of the schist schist block was restored to basalt,and its geochemical characteristics are similar to those of island arc volcanic rocks.The original rock of the gneiss block is restored to a medium acid rock,which reflects the environmental characteristics of the volcanic arc-co-collision structure.The age of the diabase is 368.4 ± 2.9Ma,and the formation age of the gneiss is 381.9 ± 2.5Ma.It is speculated that the tectonic mixed zone in the study area was formed during the Middle Devonian to Early Carboniferous.In this study,phase 4 tectonic deformation was identified in the Ertzis tectonic mixed zone.They are early ductile deformation,left ductile shear deformation,right ductile shear deformation,and late shallow brittle deformation.The Ertzis tectonic mixed zone first experienced early subduction,collage and collision during its formation,followed by extensional strike-slip motion,and finally experienced superimposition and transformation in the later stage.The Erzis tectonic mixed zone should be the product of long-term subduction of the Late Paleozoic plate.The geological development history of the study area across the entire region has gone through the following five stages.The first stage is the stage from the Cambrian to Ordovician passive continental margin basins.The second stage is the stage of the formation of continental margins of Devonian activity.The third stage is the stage of the Carboniferous plate subduction and the development of continental marginal orogens.The fourth stage is the stage of Permian intracontinental evolution.The fifth stage is the stage of stable intracontinental development of Meso-Cenozoic.