New zircon U-Pb chronology of the Neoproterozoic rift basin evolution in the western Yangtze Block and its geological significance

The Kangdian rift on the western margin of the Yangtze Plateau is one of the main components of the Neoproterozoic rift system in South China, which is of great significance for understanding the response between the evolution of the Neoproterozoic rift basin in South China and the breakup of the Rodinia supercontinent. The Chengjiang Formation is the most typical filling sequence in the Kangdian rift, and the accurate definition of its sedimentary age is an important prerequisite for the interpretation of the basin evolution in the context of the breakup of the Rodinia supercontinent. LA-ICP-MS zircon U-Pb dating of the volcanic rocks of the Chengjiang Formation in the Qiaojiaweigu area, northeastern Yunnan, yielded an age of 806.4±6.7 Ma for the basalt at the bottom of the Chengjiang Formation and an age of 788.4±5.9 Ma for the tuff at the bottom. Combined with the available age data, the sedimentary age of the Chengjiang Formation is accurately defined as 800~720 Ma, which is a contemporaneous heterogeneous product with the Kaijianqiao Formation and the upper part of the Luliang Formation. The evolution of the three secondary basins in the Kangdian rift is basically synchronous, and they all began to receive full sedimentation at ~ 800 Ma, in response to the breakup of the Rodinia supercontinent.