The Geochronological Relationship between the Shaojiwa Formation and the Xingzi Complex Group inNorthwestern Jiangxi and the Constraints on Zircon SHRIMP U-Pb Age
庐山筲箕洼组与星子岩群年代地层关系及SHRIMP锆石U-Pb年龄的制约

Ages of (840±6) Ma (MSWD=1.3), (833±4) Ma (MSWD=1.4) and (831±3) Ma (MSWD =1.47) were obtained for spilite and rhyolite from the Shaojiwa Formation. The Xingzi Complex Group has the age of 206Pb/238U (825±5) Ma (MSWD =0.46). In combination of the SHRIMP U-Pb dating of the spilite and rhyolite of the Shaojiwa Formation in the Jiangnan oregen, the authors have determined for the first time that the Xingzi Complex Group is of Neoproterozoic period and lies below the Shaojiwa Formation. These isotopic data from the Shaojiwa Formation are very important for regional correlation of the strata of the corresponding period and tectonic evolution. The zircon U-Pb ages mentioned above determine that Neoproterozoic strata around the age of 820 Ma are developed in northwestern Jiangxi Province. These data contribute to the stratigraphic subdivision and correlation of the metamorphosed rocks in whole Jiangnan old land and help geologists investigate the geological background and ore-forming conditions of the Jiangnan Orogen.