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

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.