The metallogenic epoch and ore-forming material source of the Tang-bian Pb-Zn deposit in Tongren, Guizhou Province:Evidence from Rb-Sr dating of sphalerites and S-Pb isotope

Rb-Sr dating of sphalerite, sulfur and lead isotopes of sulfides was analyzed to confirm the age of mineralization and to de-termine the origin of the ore-forming material.The Rb-Sr dating of sphalerite from the Tangbian deposit yielded an isochron age of 477±5Ma (MSWD=1.2), which is in agreement with the isochron age of 486±6Ma from the Bukouchang deposit in the range of er-ror, suggesting that the mineralization of Pb-Zn occurred in the early Ordouician.δ³⁴S values of pyrite, galena and sphalerite range from+25.2‰ to+36.1‰, similar to data obtained by previous studies of other sediments-hosted Pb-Zn deposits in eastern Guizhou and western Hu'nan.It is held that the sulfur of the Tangbian Pb-Zn deposit originated from marine sulfates and/or underlying star-ta.Lead isotope analysis of galena and sphalerite yielded ²⁰⁸Pb/²⁰⁴Pb ratios varying from 38.389 to 38.584, ²⁰⁷Pb/²⁰⁴Pb ratios varying from 15.737 to 15.790, and ²⁰⁶Pb/²⁰⁴Pb ratios varying from 18.181 to 18.217, with relative high μ values from 9.75 to 9.86.The re-sults suggest that the source of lead was mainly derived from the upper crust.Besides, some data of lead isotope point to magmatic source, which probably resulted from the extraction of lead by the ore-forming fluids from magmatic rocks.