Zircon LA-ICP-MS U-Pb dating and geological significance of Bashierxi granite in the eastern Kunlun area, China

The Bashierxi pluton is located in the western segment of the eastern Kunlun, between Baiganhu fault and Aerjin fault, this pluton mainly consists of monzonitic granite and K-feldspar granite, and the monzonitic granite is closely related with the ore-forming process of the Baiganhu tungsten-tin deposit. The internal structures, cathodeluminescence (CL) images and Th/U ratios of the zircon grains from the monzonitic granite reveal that these zircon grains have typical characteristics of magmatic zircon. The LA-ICP-MS analyses show that the zircon grains from the monzonitic granite have concordant U-Pb ages of (458.0±9.0)Ma, on the other hand, the zircon grains from the K-feldspar granite have U-Pb ages of (432.3±0.8)Ma, these data indicated that the Bashierxi pluton is a intrusion formed from Late Ordovician to Early Silurian. Major and trace element data of the monzonitic granite show that Bashierxi granite is weakly metaluminous or peraluminous A-type granite. These rocks were considered as melts derived from crustal source during back-arc basin extension in eastern Kunlun, and the early Baiganhu tungsten-tin deposit era is represented by the ages of monzonitic granite.