Abstract：In order to investigate the composition and deformation characteristics of the Hongshishan-Baiheshan-Pengboshan Paleozoic tectonic belt (ophiolite belt), using the digital geological mapping, the authors have carried out the 1:50 000 regional geological survey in Dahongshan of Beishan Area, Inner Mongolia. Through the survey, a suit of metamorphic basement was found in the south of Dahongshan, and its main rock assemblage is marine fine clastic rock with intermediate-basic volcanic rock and magnetite quartzite rock, which is characterized by ferrosilicic formation and metamorphic basic volcanic rock. The rock assemblage without bottom and top, has intensive metamorphism and deformation, and its sequences can’t be separated. So the rock assemblage is named as Xiaohongshan formation. The low and medium grade metamorphic rock indicates that the metamorphism reaches high green schist facies to low amphibolite facies. The north of the formation is covered by the angular unconformity of Upper Carboniferous Baishan Formation, and the south is intruded by the Early Devonian and Late Carboniferous intrusive rock. The outcropping area of the formation is about 140 km2 in the study area, and the thickness is about 2 890 m. There are four obvious deformations. The former three are ductile deformation, which form penetrative foliation S1, large-scale folds and ductile shear zone. The last deformation is characterized by brittle deformation and forms some large-scale faults. The multi-stage metamorphism and deformation of Xiaohongshan formation proves that the Hongshishan-Baiheshan-Pengboshan Paleozoic tectonic belt (ophiolite belt) existed and went through multi-stage metamorphism and deformation.
2018, Vol. 5 
