Characteristics of sulfides and S-Pb isotope composition in the Tiantang Cu-Pb-Zn polymetallic deposit of Guangdong Province and their Geological implications

Abstract：The Tiantang Cu-Pb-Zn polymetallic deposit of Guangdong Province occurs at the northeast edge of Yangchun basin, which is located in the Qinzhou-Hangzhou metallogenic belt. On the basis of geological field observations, the authors selected main sulfides in the deposit as the object to study the mineralogical characteristics, and analyzed the S-Pb isotopic composition so as to trace and discuss the sources of ore-forming metal materials. Representative results 1 of electron microprobe analysis show that Fe and S content and atomic ratios of S/Fe in pyrite are higher than theoretical values, there exist Cu, Sb and As, and the ratios of Co/Ni are between 0.21 and 2.28, usually higher than 1, suggesting a hydrothermal environment of relatively high sulfur fugacity; in sphalerite the Zn content is lower than theoretical values while the atomic ratios of S/Zn and the S content are higher than theoretical values, with the existence of some Pb, Fe, Co and Se; some elements in galena, chalcopyrite and other sulfides occur in isomorphism. δ34S values of the main ore minerals of this deposit have a narrow range of -2.1‰~2.6‰,with peaks at -0.8‰~0.4‰, showing tower-shaped distribution effect and features of magmatic sulfur. Lead isotopic compositions of ores are basically coincident, and 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios of ores vary from 38.765 to 39.137, 15.523 to 15.751 and 18.450 to 18.667, respectively. These lead compositions indicate that the ore-forming materials not only had features of the lower crust or the upper mantlebut also had characteristics of the upper crust, indicating that there should have been several sources for ore-forming materials in the Tiantang deposit, belonging to crust-mantle mixture, and the ore deposit was formed due to lithospheric extension in southern China since the Late Mesozoic.