The Research Of Structural Characteristics Of The Ductile Shear Zone In Langshan Area, Inner Mongolia

Lang Shan tectonic zone of Inner Mongolia located in the northern margin of the North in China Craton, It is one of the important areas of studying super deposit of chinese,and also a key areas of interaction of China plate and Siberia plate.Lang Shan tectonic belt has a different structure form, and ductile shear zone is one of the main tectonic types, and is a reflection of the deep crust structure. According to the ductile shear zone in the mylonite zone and the regularity of distribution, Lang Shan tectonic belt can be divided into three large scale ductile shear belt and a number of secondary ductile shear zone. According to the regularity of distribution of Mylonite in the ductile shear zone, Lang Shan tectonic belt can be divided into three large scale ductile shear belt and a number of secondary ductile shear zone. The method of this dissertation by the macro and micro structure, on the basis of previous studies, according to the systematic research, including geometry, kinematics, dynamics, geochemistry, and deformation age, made the following new ideas:1. By the study of the geometry of the ductile shear zone,founding out that the ductile shear zone have a different types of mylonite rock or tectonic schist, foliations direction of mylonite parallel to the Lang Shan Mountain, and mylonite foliation only developed a set of the mineral stretching lineation, lineation to NE or SW direction.2. By the study of the macro structural features of Lang Shan,revealed the presence of tectonic lens, rotating Porphyroclasts, Omega shaped sheath folds, Shi sausage mylonite in the ductile shear zone, and these macro structure indicates the shear sense of ductile shear zone is the left.3. By the systematic study of micro structural features of Lang Shan ductile shear belt,through the oriented slice under microscope, microstructural has core mantle structure, wavy extinction, mainly quartz microstructure of recrystallization, sub grain or mechanical twinning, mica kink band structure, and by the microstructure,such as rotational porphyroclast, asymmetric pressure shadow, S-C fabrics, mica fish, indicate the shear direction to the left lateral, and consistent with the field to determine the shear direction.4. Through the structural analysis of Lang Shan ductile shear zone, illustrates the quartz of ductile shear belt Ⅰ,Ⅱ has a cylindrical sliding and basal slip slid mechanism,during the shearing process, the effect of the ductile shear zone with high temperature and medium high temperature in cylinder <c> slip - cylindrical <a> mainly slipping, characteristics of the Ⅱ ductile shear zone is high temperature and low temperature in cylinder <a> bottom <a> slip, the characteristics of the quartz structural analysis in the two ductile shear zone shows the direction of shear is left, consistent with the direction of field and microscope.5. By the relationship between microstructure characteristic of Lang Shan ductile shear zone and strain, using the method of quartz grain recrystallization and the creep equation calculated the paleo differential stress value of Lang Shan ductile shear zone was 72-94Mp stress, average strain rate of 5.8x10-13 s-.6. In geochemistry, obvious plastic flow characteristic of Lang Shan Ⅱ ductile shear zone with siliceous banded limestone has been study by the analysis of rare earth elements,trace elements,and major elements, the results showed the difference between different deformation strength of siliceous banded limestones and protolith composition. Most major elements and trace elements of banded limestone rocks are enrichment of elements, and with the deformation increase, the REE distribution patter of various tectonic rock and original rock is consistent, also shows that the rare earth elements have certain relative stability and homology in the shearing process.7.For the 40Ar/39Ar dating of Lang Shan ductile shear zone in Ⅱ,Ⅲ, shear zone, the test results show that the Ⅱ,Ⅲ, ductile shear zone of Lang Shan were formed in the late Devonian, and illustrates the Lang Shan tectonic belt has a striking tectonic activity in Late Devonian to Early Carboniferous.