SHRIMP zircon U-Pb dating of gneisses in the Mayin Obo fault belt, northern Xinjiang, and its significance

Abstract：There is a long dispute over the age of medium- and high-grade metamorphic rocks in the Altay area, including gneiss in Qinghe. Li Tiande et al. assign medium- and high-grade metamorphic rocks in the Chonghuer-Altay-Qinghe area on the southern margin of the Altay Mountains, Kuwei-Wuqiagou area of Fuyun County and seat of Fuyun County to the Paleo- and Mesoproterozoic Kemuqi Group and Neoproterozoic Fuyun Group, which has attracted wide attention and debate, especially disputes over the age of gneiss in the Mayin Obo fault belt southwest of the seat of Qinghe County. The authors have performed zircon U-Pb SHRIMP dating of the gneiss. Although they failed to obtain concordia ages, the data of ages in different time intervals still have certain geological significance. The abundant age information of Precambrian zircons affirms the possibility of the occurrence of Precambrian strata in the Altay region and determines that the gneiss should form earlier than the Late Paleozoic.