内蒙古化德地区三面井组沉积地质特征OA

The Huade area in Inner Mongolia is located at the southern extremity of the central segment of Xing'an-Mongolia Orogenic Belt.The Permian marine strata exposed in this area serve as ideal repositories for studying the tectonic evolution of Paleo-Asian Ocean.In this study,multiple methods including paleontology,zircon U-Pb geochronology and sandstone framework grain analysis were employed to investigate the Sanmianjing Formation in Huade area.The results show that the Sanmianjing Formation represents a transgressive succession deposited in littoral to neritic environments,containing Early-Middle Permian fusulinid fossils.The youngest detrital zircon age from the sandstones is 274±6 Ma,defining the minimum depositional age of Sanmianjing Formation.The detrital zircons exhibit three main age populations:274-338 Ma,1 567-2 193 Ma,and 2 310-2 656 Ma,indicating a mixed provenance of a magmatic arc related to the subduction of Paleo-Asian Ocean and the basement of North China Craton.The framework grain compositions and mineral assemblages of the sandstones further show that the tectonic affinity of the provenance includes both a magmatic arc and a stable craton or uplifted basement.Integrated with regional geological data,these results reveal that the Sanmianjing Formation was deposited during the Early Permian and originated in a back-arc basin,further suggesting that during the Early Permian,the Paleo-Asian Ocean was still subducting southward beneath the North China Block.These findings provide new foundational data for understanding the tectonic evolution of Xing'an-Mongolia orogenic belt.