New evidence for the opening time of the Neoproterozoic Kangdian rift basin， western Yangtze Block， South China

The Suxiong Formation is the product of volcanic eruption in the early period of the Neoproterozoic Kangdian Rift Basin on the western margin of the Yangtze Block,South China, and its forming time can provide new evidence to restrict the opening time of the Kangdian Rift Basin. Based on LA-ICP-MS, zircon U-Th-Pb dating of the rhyolite from the Neoproterozoic Suxiong Formation in Jiuxiang, Hanyuan in western Sichuan Province was carried out. The testing result shows that the zircon U-Pb concordant age is 853 ±2 Ma (N=13;MSWD=3.1) and the zircon U-Pb weighted mean age is 853 ±4 Ma (N=13;MSWD=2.2). These new age data indicate that the bottom age of the Suxiong Formation should be descended to ca.850 Ma and the opening time of the Neoproterozoic Kangdian Rift Basin on western Yangtze Block, South China should be innovated to ca.850 Ma, which is basically simultaneous with the upwelling of the super mantle plume and the breaking-up of the Rodinia supercontinent.