SHRIMP U-Pb zircon dating of tuff in the Shuangqiaoshan and Heshangzhen groups in South China—constraints on the evolution of the Jiangnan Neoproterozoic orogenic belt

A large number of zircons were obtained from three samples of bentonite in the Hengyong and Anleling formations of the Shuanqishan Group and Heshangzhen Group. They yielded weighted mean 206Pb/238U ages of 831 ± 5 Ma for the Hengyong Formation, 829 ± 5 Ma for the Anleling Formation and 767 ± 5 Ma for the Shangshu Formation of the Heshangzhen Group by the sensitive high-resolution ion microprobe at the SHRIMP center, Curtin University, Western Australia. These ages show that the widespread Shuangqiaoshan and Heshangzhen groups should be assigned to the Neoproterozoic and provide accurate chronostratigraphic evidence for the determination of the location of the Shuanqishan Group in the stratigraphic column.