LA-ICP-MS zircon U-Pb dating of the Xinyang Neoproterozoic granitoid gneisses in the Tianshui area, western Qinling, and its geological significance

Abstract：The Xinyang Neoproterozoic granitoid gneiss, identified from the Paleoproterozoic Qinling Group complex on the northern margin of the western Qinling orogen, is located to the east of Xinyang town of the northwestern Tianshui. The internal CL images of zircons in granitoid gneiss show that the zircons have higher Th/U ratios and clear oscillatory zoning, indicating an igneous origin. The acquired LA-ICP-MS zircon U-Pb weighted average ages (938±4 Ma and 981±5 Ma) indicate that the granitoid gneiss was formed in the Neoproterozoic and that a tectono-thermal event (subduction and collision) occurred on the northern edge of the West Qinling during the Jinningian, which is presumed to be the response of the convergence of the supercontinent Rodinia in the West Qinling.