SRHIMP zircon U-Pb dating of metamorphic tuff from the Precambrian Cangxi Complex-Group in northeastern Hunan

This paper reports a SHRIMP U-Pb age (855 Ma ± 5 Ma) of metamorphic tuff from the Fengzichong Complex-Formation. Although zircons have different forms, their CL images show typical magmatic oscillatory zoning. The zircons have relatively high content of U and Th, with Th/U ratios vary in the range of 0.32~0.87. Therefore, they are of magmatic origin. The new data change the traditional stratigraphic correlation of the Cangxi Complex-Group in northeastern Hunan. Therefore, the SHRIMP U-Pb dating of the metamorphic tuff from the Fengzichong Complex-Formation at the bottom of the Cangxi Complex-Group is of great significance in understanding of the tectonic framework of the “Jiangnan Orogenic Belt” in Hunan.