Zircon U-Pb age and tectonic thermal event of the volcanic rocks from the Paleoproterozoic Yimen Group Luowadie Formation in Yimen area, Central Yunnan

Yimen Group is the Palaeoproterozoic weakly metamorphic strata determined by the latest "Yunnan Province Regional Geology"(second edition of revision) project, which integrates the latest field geological data and isotope chronology data of Yuanjiang Cuoke, Yimen Tongchang and Dongchuan Yinmin. It records a series of major geological events in the early stages of the Earth's evolution, such as the Early Paleoproterozoic Huron Ice Age event and the following mantle plume events, the first appearance of simple multicellular organisms, the narrow Lomagundi carbon isotope positive drift event, and hypoxic selenium-rich deposits after the collapse of oxygen-rich atmosphere. The LA-ICP-MS zircon dating method was used to date the Luowadie microcrystalline tuff and the dacite tuff in the Yimen Group of Yimen area. The zircon U-Pb dating yielded a weighted average age of 2241±16 Ma(MSWD=0.64, n=14), 2252±14 Ma(MSWD=0.71, n=13). The zircon Th/U ratio of the two samples is 0.2~1.0, both of which have a clear oscillating ring structure, indicating the zircon of magmatic origin. The study indicates that the sedimentary time of the Luowadie Formation in the Yimen area of the Yime area is Middle Paleoproterozoic, which can be compared with the mantle plume tectonic combination of the Yuanjiang Couke and the tuff in the Luowadie Formation of Dongchuan Yinmin. The sedimentary time of the Luowadie Formation may represent the response of Kenorland supercontinent splitting in Yangtze.