The Characteristic Of Deformation,Metamorphism And Geochronology In The South Segment Of Ailao Shan-red River Shear Zone

The process of regional Indian-Eurasian collision and shortening,extrusion of the Indochina along Ailaoshan-Redriver shear zone,and rotation of the eastern Tibet blocks have been payed attention and researched by scientist.research emphasis is metamorphic rock inside of Ailaoshan group,syn-kinematic granite and left-lateral strike-slip shear fabrics by which would make clear the significance of Ailao Shan-Red River shear zone in the process of geological evolution.Based on analyzing attitude of metamorphic rock inside of Ailaoshan group and granite and microtectonics of three section in the south of Ailao Shan-Yuanyang-Xinjie section,Yuanyang-Xiaoxinjie-Fengchuling section and Jinping-Manhao section,there are two event happening,including ductile left-lateral strike-slip shear fabrics and high tenmperature-pure shear.Using EBSD technique,analyse quartz c-axis fabric of 8 samples,which have obviously deformation characteristics.The test result shows that there are high temperature ductile shear fabrics and medium-lower temperature left-lateral simple shear fabrics.Base on identifying Grt+Amp+P1+Qz that is metamorphic minerals combination of High amphibolite facies and Czo+Act+Cld+Ab+Qz that is metamorphic minerals combination of low green schist facies under the microscope,there are multi-period happening in the metamorphic rocks.Using garnet-biotite thermometer,garnet-biotite-plagioclase-quartz piezometer and plagioclase-hornblende thermobarometer,the result shows that peak metamorphic temperature of low amphibolite facies is 600? after early above 660? peak metamorphic temperature of high amphibolite facies.In Ailao Shan-Red River shear zone,there is granite and pegmatite(vein)intruding deep metamorphic strata widespreadly.Base on connected relation of granite and wall rock and result from predecessor,it reveals that there are two shear fabrics in Ailao Shan-Red River shear zone:(1)high temperature shear fabrics happened before 30 Ma;(2)medium-low left-lateral simple shear fabrics happened between 27-21 Ma.Combining 40Ar/39Ar thermoluminescent dating,it happened high grade metamorphism and high temperature pure shear fabrics before 30 Ma.At the same time Ailao Shan deep metamorphic block was in deep crust,when Indian-Eurasian was in the process of collision and shortening.At about 27 Ma,Ailao Shan deep metamorphic block was in medium crust with uplifting and denudating rapidly,when left-lateral ductile simple shear fabrics was beginning.When shear fabrics was over at 21Ma,Ailao Shan deep metamorphic block had been in shallow crust.