巴音戈壁盆地巴北凹陷G4井火山岩锆石U-Pb年代学及其地质意义OACSTPCD

Babei sag is a secondary structural unit in the western Guaizihu Depression of the Bayingobi Basin.In recent years,certain achievements have been made in uranium exploration within the sag.However,the overall research level is relatively low in the sag and there is a significant controversy in the division and comparison of strata,no chronological study was conducted in the deep volcanic rocks,and the geological age is still unclear.In order to accurately divide the sedimentary cover layer within the depression and clarify the target layer for uranium exploration.In this study,the G4 line section in the northern part of the sag was selected for detailed dissection,and samples were systematically taken for petrological and zircon U-Pb dating studies so as to provide evidence for the above issues.The analysis results indicate that there are two sets of zircon ages measured by drilling deep volcanic rocks,namely(126±4.2)Ma and(243.5±1.7)Ma.Both sets of zircons are magmatic zircons,and the younger age represents the formation age of the set of volcanic rocks,that is,the middle Early Cretaceous.The second set of ages represents the age of early magmatic zircons captured by volcanic activity.The formation age of basalt effectively constrains the formation age of the strata,indicating that the formation of this layer of basalt is located in the lower member of the Lower Cretaceous Suhongtu Formation.Based on the verified volcanic rock age,the sedimentary cover layers in the area have been finely divided and the stratigraphic classification criteria have been summarized.Based on comprehensive analysis of sedimentary system and uranium content in the strata,the Lower Cretaceous Yingen Formation has been determined as the main uranium exploration target layer.