Zircon U-PbDating about Volcanic Rocks of Ganquan Formation in Dahulishan Area, Ejina Banner and Its Geological Implication

Volcanic and clastic rock members of Ganquan Formation within Yin'e basin hasoutcropped in Dahulishan area very well. The volcanic rock member is consists of basalt with crystal pyroclast and intermediate-acidic volcanic rocks, forming a bimodal volcanic rock assemblage.Through using LA-ICP-MS zircon U-Pb dating, the isotopic ages of (305.2±3.9)Ma(MSWD=7.9) for basalt with crystal pyroclast have been obtained in this paper, indicating the age for the strata of Ganquan Formation is Late Carboniferous. Combining with the contact relationships among these strata, it's determined that the age of Ganquan Formation is Late Carboniferous-Early Permian. This data has a great significance for analyzing the depression and filling evolution process of Hongshishan-Heiyingshan in the northern part of Yin'e basin. Thus, this Late Carboniferous basin belongs to the rift basin, developing a rapid cleavage and depositing a giant thick clastic rocks and volcanic rocks.