SHRIMP age of the lava from the Sibao Group in Guilin and its chronostratigraphic significance

The Sibao Group, outcropped in the north part of Guangxi and southeast part of Guizhou, is composed of over 5000 m thick succession of strongly-deformed, low-grade metamorphic volcanic rocks and terrigenous clastic rock, overlain unconformity by the Danzhou Group (Xiajiang Group). It is divided into three Formations:Jiuxiao Formation, Wentong Formation and Yuxi Formation. Sample A20140731-3 is lava, collected from the upper part of the Wentong Formation, and over 600 grains of zircon were sorted out from it. Fifteen of the zircons were analyzed with SHRIMP, and a weighed-mean U-Pb age of (860±13) Ma was obtained, which indicates that the volcanic rocks of the Sibao Group belong to Neoproterozoic. Based on this new zircon SHRIMP U-Pb age combined with the other high-quality ages obtained recently in the Jiangnan Orogen, the authors investigated the stratigraphic correlation between Sibao Group and the other main strata, such as Lengjiaxi Group, Shuangqiaoshan Group, and Fanjingshan Group.