Tectonic Deformation Of The Xuniwusu Thrusting Tectonic Systems In Inner Mongolia

The study area is located in the middle part of Inner Mongolia, and its geotectonicposition lies in the northern margin of North China Plate, where closes to the realm of thecollision belt of Siberian Block and North China Plate. According to Xuniwusu fault, thestudy area is divided into north China stratigraphic province and northernXinjiang-Xing’an stratigraphic province. At the same time, the fault which is alsoconsidered geosynclines-platform boundary, the southern part belongs to geosynclinal areaand the northern part belongs to platform region. Outcropped strata in the study area aremainly Seerteng Group of the Early Archaeozoic, Bayan Obo Group of theNeoproterozoic, Ondor Sum Group and Bainaimiao Group of Cambrian-Ordovician,Xijingzi Formation of Lower cambrian, Wudaowan Formation of Lower-MiddleOrdovician, Xuniwusu Formation and Xibiehe Formation of Silurian, Benbatu Formationand Amushan Formation of Lower Carboniferous, Sanmianjing Formation and ElituFormation of Lower permian, and a small amount of strata of Mesozoic and Cenozoic.According field observation and previous research, a lot of thrust outcroppes in thestudy area, it’s found that the Bayan Obo Group coverres on the Paleozoic strata. Thestrata trends along the Xuniwusu Fault, and its trending length is about160km, it is called"Xuniwusu Thrusting Tectonic belt". In this study, for the first time to systematically studythe various features which include distribution, zoning characteristics, structuraldeformation, thrusting direction and distance of the thrusting tectonic. This studycomplements the previous research on the shortage of the middle part of the Xuniwusu Thrusting Tectonic belt. Combined with the nature of the Xuniwusu fault, we reasonablyconclude that the Xuniwusu fault is not the geosynclines-platform boundary.According to its distribution and structural features, the belt is divided into thrustingtectonic frontal zone and thrusting tectonic central zone. The frontal zone distributes alongthe Bulitai-Xuniwusu-Bainai miao-Borihe-Zhangmaowusu-north of Huade. At the sametime the central zone distributes along the Dongxiwusu-Aiguocun-Zhanggaiying-Xijingzi,characterizing in developping a large number of different sizes and configurationswindows and klippen, fault breccia development and nappe structure interface beingwrinkled. This study failed to identify the root zone which is likely to have been destroyedby the magmatism and tectonic movement in the later stage.The Xuniwusu thrusting tectonic can be divided into two stages: the large-scalehorizontal movement is the feature in the first stage, at the same time the feature of thesecond stage is extrusion deformation. From the occurrence data analysis that wasmeasured in the study area, roughly determines that the thrusting tectonic was mainlyaffected by the role of the regional north-south squeeze. From the strata and the instrusiverock which associated with the thrusting tectonic, the time of the thrusting tectonic wasdefined in last stage of the Early Permian.Through this study, we conclude that the Xuniwusu fault belt is not thegeosynclines-platform boundary, due to the fault is a series of reverse faults combinationand the dip angle is small. We conclude that the real geosynclines-platform boundary liesthe south of the fault at about10-20km.Combined with the regional tectonic evolution backgroud, suggesting that thisthrusting tectonic is related to collision with the North China Plate and Siberian Plate andclosure of the Paleo-Asian Ocean in Permian.