The Research Of Xilinhot Fault Zone,Inner Mongolia

Xilinhot fault zone is a large-scale, long-lived fault, which plays a significant role in controlling and Dividing the Paleo-Asiatic tectonic domain. Although it has always been focused by geologist, the research degree is low. This article depended on the geological survey project titled "1:50000Scale Regional Geological Mapping in Bayinhushuo, Xilinhot. Xilinhot copper smelter Taolintala etc. region, Inner Mongolia"(poject number:1212010811005), we systematic study on the spatial distribution,fracture stage, geometry, kinematics of the fault zone, in addition, combine with the comprehensive research on stratigraphic, magmatic activity and other aspects, we discuss the tectonic attribute of the Xilinhot fault zone. The results obtained are as follows:Based on the results of this study, through the summary of the regional geological data, we demonstrate the presence of Xilinhot fault and identify the spatial distribution of it. Then we give the definition of Xilinhot fault zone:Xilinhot fault zone sprawls from Suolun mountain in the west, by Sunidzuoqi, Honger, Xilinhot Buhate quarry, Shihuiyao-Xiamachang, since the Baiyinchagan transfers north east into Keqi coal mine-Zhunbumutai-Daolundaba Sumu in West ujimqin, it may also be extend to east and west two directions, the total length is more than310km, which is a far extend, large-scale, multi-stage, structure-complex and long evolution history regional deep fractures.Through the research on the cross-cut relationship between the fault and fault, fault and different era geological body, the Xilinhaote fault zone is mainly the product of two stages of tectonic action:Caledonian and Hercynian-Indosinian. Caledonian ductile shear zone cutting through the latest geological unit is the middle Silurian, and it also intrusive by Carboniferous granite (324.4±2.4Ma),what is more, the Devonian to Early Carboniferous is the stabilization period of geological activity in study area, so this period does not provide the tectonic environment condition to form the ductile shear zone. The above discussion provides a floor and the upper limit of the age of the Caledonian formation:middle Silurian to Early Devonian. Hercynian-Indosinian fault cut along with all the Mesozoic Geological Body, the mylonitized granodiorite weighted mean age is275.4±5.5Ma (U-Pb),it is the lower age limit for dynamic metamorphism events. Moreover, the hornblende from strongly deformed plagioclase amphibolite samples in Xilinhot group shows40Ar/39Ar plateau ages of263.11±2.3Ma、263.69±1.4Ma, All this shows that Xilinhot fault zone is still active in the Indosinian.Affected by the Caledonian orogeny, the study area is in strongly compressed environment, Xilinhot fault performances as a series of north dipping south lodging imbricate thrust faults. From late Permian to Early Triassic period, crust suffered by North West-South East extrusion, it moved into a new period of tectonic evolution. Hercynian-Indosinian fracture is often inherited or small-angle miters the Caledonian orientation, constitute the NEF reverse fault system.In Caledonian deformation period, the nature of the Xilinhot fault is right-oblique filling ductile deformation zone. Therefore, the fault was characterised by the development of brittle-ductile shear deformation belt. This reflects the two different levels of deformation characteristics.Through the analysis of the characteristics of the stratigraphic and magmatic activity in same period, we identified the the tectonic attribute of the Xilinhot fault zone. It controlled the formation and development of early Paleozoic continental margin arc In the Caledonian; Then in Hercynian-Indosinian, it experienced the cracking and shutdown procedures of the regenerated small ocean basin.Combined with existing data of Xar Moron River fault zone in the south, we believe that Xingmeng orogenic belt’s final converge position is in the area between Xilinhot fault and Xilamulun fault, we named it Suolun-Linxi junction belt. The time of two plates for the final convergence is early-middle Triassic. And the XingMeng orogenic belt is a cycle orogenic bell, compared with other orogenic belts around the world, it has a weak orogeny, and the convergence pattern of two plates is the junction with low energy.