Research On Ductile Shear Zone In Siziwangqi Inner Mongolia

Indicate on research, Siziwangqi ductile shear zone lies in middle-west segment of the north margin of Huabei platform, This shear zone is borderline of the north margin of Huabei platform and late Proterozoic Baiyunebo passive continental margin, the in north and south side of which suffer completeness difference course of tectonic evolvement.which take on NEE through the north of Siziwangqi, extend about 100 kilometer, width about 6⁸ kilometer. Mylonitic plane attitude of the ductile shear zone is quite stabilization, the most direction of tilt is south, the less is north, obliquity of which is 50⁸0 degree, direction of strike of stretching lineation is Northeast orientation, obliquity of which is commonly upon sixty degree. From north to south, the whole ductile shear zone show alternate strong-light deformable zone. Observation from the whole zone, the northern deformable zone is strong, the southern deformable zone is light, middle is the most strongest, that show inside structural character of the shear zone.The rock of the shear zone is commonly mylonization-ultramylonite, there are some structural character in the shear zone, such as badinages,the shape of"σ"rotary fragment, the shape of"a"direct folding,"domino-style"structure,"mica fish", quartz stripped structure, mechanical twinning, strain shadow. The ductile shear zone show left-lateral shear on macrocosm and microcosm, therefore, it is the type of thrust ductile shear zone, viz. diagonal thrust from SW to NE.In the dynamics, we account some stress in the shear zone, the orientation of principal stress is near south-north. We reckon differential stress by subgrain, which is 50.56 Mp, we obtain average strain velocity by creep equation, which is 1.56×10⁽-110 s^-1. According to character of deformation and mineral association, we think the ductile that formed 11²2 kilometer the earth's crust, so, we conclude this shear zone attribute to low-greenschist facies, it's temperature of formation is less than 500℃.According as time of magma , characteristic of deformation , relation of incision and characteristic of lithogeochemistry, combined tectogenesis of region, we think this shear zone that formed in Mesoproterozoic and Neoproterozoic.