Cenozoic Deformation Characteristics And Regional Tectonic Thermal Evolution Discussion Of Yaoshan Metanorphic Complex In The West Of Yunnan

Yaoshan metamorphic complex located in western Yunnan of the Honghe-Ailaoshan southernmost shear zone,which sandwiched between the Red River fault zone and Song Chay fault zone,extending in NW-SE direction.Yaoshan metamorphic complex is experienced a deep metamorphic rocks of amphibolite facies metamorphism,which suffered a multi-phase deformation,metamorphism and migmatization,and preserves the evidence of strike-slip shear deformation,the latter suffered a dextral shear movement.This paper mainly through Yaoshan group as the research object,on the basis of the previous data and observations by outcrop,combine with the indoor microstructural analysis,fission track dating techniques to research the composition of its rocks,metamorphic deformation characteristics,as well as deformation and metamorphism and tectonic evolution relationship.The writer thought Yaoshan metamorphic complex is not a simple large anticline in the shape,but a top closure,arched sides of the anticline,the northern end of a narrow,southward gradually open,high metamorphic grade core of outward gradually reduced the dome body,by a number of regional tectonic deformation tape.Yaoshan metamorphic complex's lineation overall for the Northwest-Southeast,plunging nearly horizontal angle,indicating it was undergoing a early horizontal shear movement southward movement of the plate,and in the course of the movement,the rock began to cool and uplift.The starting age in the process of the shear may represent the start of cooling age.The regional tectonic evolution can be roughly divided into three stages.The first stage,occur in the middle and lower crustal levels,Yaoshan group in the high temperature phase to achieve high overall experienced early amphibolite facies metamorphism.In the second stage,rock mass occurred nearly horizontal shear movement,forming a series of A-type folds and asymmetric porphyroclastic etc during the period.In the shearing process,Yaoshan metamorphic complex began to uplift and exhumation,and the fission track geochronology data indicates it has the tilted exhumation features.The core is the first uplift,southwest and north east side of the side slightly early uplift,while rock uplift rate in the core is faster than the wings and the northern section is rising more quickly than the southern section,reflecting the exhumation in the longitudinal inhomogeneity.The cooling history at least starting at 30Ma,and before 30Ma it was slowly exhumation,but in the 29-26Ma,25-22Ma,Yaoshan metamorphic complex is experienced two periods of rapid cooling process.At the same deformation process,different levels of deformed metamorphic rocks have different performance,while at the same level during the exhumation and there will be progressive rock deformation performance.In the third stage,since about 13Ma,RRFZ start dextral strike-slip normal faulting events,and formed a small granite dextral ductile shear zones in Yaoshan group,and intrusive within shear zones and fracture zones formed in the local position,the overall deformation process is under low greenschist facies conditions.