Tectonic And Thermal Evolution Of Late-stage Exhumation Of Diancangshan Metamorphic Complex,yunnan,China

The large-scale Ailaoshan-Red River strike-slip fault zone?ASRR-SSF?,as the eastern boundary of the Indochina block,plays an important role in the Indian-Eurasia plate collision and post-collision evolution.Along the ASRR strike-slip fault zone,the four narrowed and oritented high-grade metamorphic complexes are exposed,and Diancangshan metamorphic complex is one of the four metamorphic complexes developed along the ASRR fault zone,Yunnan,China.Based on the previous research and geological field work,we carried out the relevant research on deformation and metamorphism,and exhumation of deep metamorphic rocks within the Diancangshan metamorphic complex.With the combinated experimental techniques of optical microscope?OM?,cathodoluminescence?CL?,electron backscatter diffraction?EBSD?,electron probe microscopy analyzer?EMPA?,fourier transformation infrared spectrometer?FTIR?and ⁴⁰Ar-³⁹Ar dating,our contribution reports the micro-and sub-microstructure,lattice preferred orientations?LPOs?and identification of mineral phase,temperature and pressure estimation of retrogression mylonites,analysis of water content of retrogression mylonites and the exhumation and cooling history of the Diancangshan metamorphic complex.All these results indicate that:?1?Diancangshan deep metamorphic rocks have experienced four stages of metamorphism and deformation since the Cenozoic,including early high-temperature peak-metamorphism?M1?and left-lateral high-temperature ductil shearing?M2?and subsequent low temperature retrogression metamorphism and deformation?M3?,which is accompanied by extension and rapid exhumation of Diancangshan metamorphic complex;and the latest stage of brittle deformation?M4?;?2?the superposition of low-temperature deformation and metamorphism occurs at the ductile-brittle transition zone,which is under the conditions of frictional-viscous transition of K-feldspar?450??;?3?the fluid is quite active during the syn-tectonic shearing overprinted low-temperature deformation and metamorphism.The low-temperature dynamic recrystallization and/or fractures to micro-fractures resulted in the strongly fine grains of the main minerals,and present strain localization in microdomains which leads to the transformation of rheological weakening,such as the development of the micro-shear zone.It is often accompanied by the decrease of rock strength and finally influences the rheology of the whole rock during progressive deformation and exhumation of the Diancangshan metamorphic complex;and?4?late extensively superimposed of low-temperature metamorphism and deformation occurs in ductile and britle transition zone which is accompanied by the decrease of temperature and compressure during the rapid exhumation of Diancangshan metamorphic complex since 10.24±0.14Ma,and it is consistent with differential rotation and extension of Indian plate and Indochina block.