The Feature Of Tectonic-Magna Belt Of Datan-Siziwangqi-Zhaohe Temple In Middle Area, Inner Mongolia

Field geological study shows that the nearly east-to-west tectonic magma belt of Datan—Siziwangqi—Zhaohe-Temple is composed of the Seerteng Moutain rock-group and the granitic intrusions metamorphosed in the Archeozoic Era. The general geometric feature is schistosity strike nearly east-west. According to the plastid distribution of the tectonic belt and the shear deformation, this tectonic magma belt can be divided as follows: the north zone, the middle zone and the south zone, each of which is characterized by dextral movement. In the south zone, the plane tilts to the north, with an angle of 30—45°. Its lineation strike is approximately identical with that of shear plane, with its dip angle less than 200, and it has the kinematic feature of dextral thrusting. In the middle zone there exists relatively weak deformation and the plane is nearly vertical. The shear plane in the north zone tilts mainly to the south and some parts to the north, with dip angle 50-80°.。Its lineation strike is identical with that of plane,with dip angle less than 300. The inclination of stretching lineation is approximate to that of plane,and the dip angle is more than 600.,with the kinematic characteristics of dextral and oblique falling.Lithologic study shows that the rock group of Seerteng Mountain was formed in island arc, while the granitic intrusive rocks are the syntactic granites intruded in the syntectonic phase, with the crust-mantle contamination characteristics. Seerteng Group and the intrusions together constitute the granite greenstone belt on the northern margin of North China, which mainly experienced greenschist—amphibolite~facies metamorphic role. Its major tectonic deformation can be divided into folding action of two periods and the late ductile shear deformation. In the metamorphic process, the tectonic belt became up-gravity and the landmasses on the northern margin of North China became concreted and proliferated. It lays the foundation for the early Precambrian structural framework of the landmasses on the northern margin of North China.Microstructural study shows that the deformed minerals are mainly feldspar, quartz and mica. There are two types of feldspar: K-feldspar and plagioclase. These minerals are generally formed in the shape of tiny augen-porphyroblast or lense. The direction of its long lexis is parallel to that of mylonitic plane and the tiny porphyroblast group which shows the shape of"σ"and has the function of orientation are formed after rotation. Feldspar lens and quartz particles have a"domino-style"structure. Therefore, the bending of feldspar twin and the deformation of feldspar porphyritic crystals leads to the formation of conjugate----the same directional micro-cracks. Based on the porphyroblasts of feldspar, aggregates, synkinematic augen , rectangular quartz stripped structure, wavy extinction and the long axis orientation distribution, S-plane is formed and it is grouped with shear plane structure S-C. Mica minerals constitute a picture of"mica fish". Part of the K-feldspar presents myrmekitic quartz texture, and this microstructural feature is equivalent to greenschist of Scholz model with that depth of crust being 11-22km T=300-4500C.