The Geological Characteristics And Geotectonic Significance Of Shuangbaotang Formation Of Lower Permian In Northern Alax Area, Inner Mongolia

The study area is located in Yingen-Ejinaqi Basin,which is fringed by the south China plate and by the tarim plate in the west and by the Siberian plate in the north,which is in the south of the Paleo-Asian Ocean western part.And is the important part to discuss the tectonic evolution of the Paleo –Asian ocean.This article uses the theory of sedimentary,paleobiology,petrological geochemical and other methods to analyze the characteristics of Shuangbaotang Formation of Lower Permian in Northern Alex,Inner Mongolia.The Engelwusu suture zone has divided the palaeozoic erathem into two parts: Tarim-Nanjiang stratigraphic region to the northwest part and North China stratigraphic region to the southeast part.The Shuangbaotang formation of lower Permian is in Tarim-Nanjiang stratigraphic region,which is outcrops in the north and south of the study area,both of them are spreaded as NEE orientation.This article have defined the date of Shuangbaotang Formation in the south part of the study area to the early stage of Lower Permian on the basis of the evidence of the fossil and detrital zircon U-Pb age date,and the formation age in the north part of Shuangbaotang Formation havn't been defined.It is found that Shuangbaotang Formation in north and south of the study area also shows great differences with their geological characteristics.This article compared their lithological characteristic,Metamorphic and tectonic characteristic and geochemiocal Parameters,the results showed that they were formed in different continental margin,so we infered them who might formed in different geotectonics position.The south of Shuangbaotang Formation is divided into shallow water carbonate plate facies and non-barrier coast faces,and the north of Shuangbaotang Formation is littoral facies and neritic facies.Late Carboniferous-Early Permian,There was a back-arc basin formed in Hangwula area with the subduction of the ocean in the north of the Huhetaoergai intra-oceanic arc.The Huhetaoergai intra-oceanic arc had finished the transformation process from oceanic crust to continental crust in the late of the early paleozoic,the formation in Hariaoribuge was formed in continental island arc zone to the north of Huhetaoergai intra-oceanic arc.