Chronology and geological significance of spillite-keratophyre in Pingshui Formation, northwest Zhejiang Province

This paper reports LA-ICP-MS zircon U-Pb ages of spillite-keratophyre in Pingshui Formation, northwest Zhejiang Province. The Th/U ratios in the range of 0.42-2.28 show that the zircon is a typical magmatic mineral. Analytical results show that the weighted mean ,²⁰⁶Pb/²³⁸U age of the spillite is (952±5) Ma (n=18, MSWD=0.19), and that of the keratophyre is (954±8) Ma (n=15, MSWD=0.51). Combined with previous studies and geological facts, the authors hold that the diagenetic epoch of the spillitekeratophyre in the Pingshui Formation was the Neoproterozoic (about 950 Ma). It is further suggested that the amalgamation between the Yangtze and Cathaysia Blocks in the eastern segment of the Jiangnan orogen was completed between 1.0 Ga and 0.9 Ga. It can be inferred that the Pingshui area and even Qin-Hang metallogenic belt have the potential in search for VMS deposits.