Sulfur isotopic composition of the Tianqiao Pb-Zn ore deposit, Northwest Guizhou Province, China: Implications for the source of sulfur in the ore-forming fluids

The Tianqiao Pb-Zn ore deposit of Guizhou Province, China, is located in the mid-east of the Sichuan-Yunnan-Guizhou Pb-Zn-Ag multi-metallic mineralization area, which is representative of the Pb-Zn ore deposits in this area. It consists of three main orebodies, whose Pb+Zn reserves are more than 0.2 million ton. This paper analyzes the sulfur isotopic composition of these orebodies. The data show that the ore minerals (galena, sphalerite, pyrite) in these orebodies are enriched in heavy sulfur, with δ 34 S V-CDT values varying between 8.35‰ and 14.44‰, i.e. the δ 34 S V-CDT values of pyrite are between 12.81‰ and 14.44‰, the mean value is 13.40‰; the δ 34 S V-CDT values of sphalerite are range from 10.87‰ to 14.00‰, the mean value is 12.53‰; the δ 34 S V-CDT values of galena are range from 8.35‰ to 9.83‰, the mean value is 8.84‰, and they have the feature of δ 34 S pyrite >δ 34 S sphalerite >δ 34 S galena , which indicates the sulfur isotope in ore-forming fluids has attained equilibrium. The δ 34 S V-CDT values of the deposit are close to those of sulfates from carbonate strata of different ages in the ore-field (15‰), which suggests that the sulfur in the ore-forming fluids should be derived from the thermo-chemical sulfate reduction of sulfates from the sedimentary strata.