A large number of exhalative sedimentary Pb- Zn deposits occur in the Xunyang basin in the southern Qinling region. These deposits are hosted in the Silurian Meiziya Formation and the Shuanghezhen Formation with bedded or lenticular orebodies. The Silurian organic- rich black shales are intensively exposed in the Xunyang basin. To better understand the black shales contribution to the zinc and lead mineralization, we conducted the H- O- S- Pb isotopic study of the Nanshagou and Guanzigou Pb- Zn deposits, which are representative SEDEX type deposits in the Xunyang basin. The δ D V- SMOW values of quartz that coexist with sulfides in the Nanshagou and Guanzigou are between -139‰~-94‰ and -129‰~-103‰, respectively, significantly lower than that of chert in the mining area, indicating that basin brine fluids that originally generated from seawater have been significantly influenced by organic matter. Sphalerite and galena have δ 34S values ranging from 4. 5‰ to 10. 7‰ (average 7. 2‰) and 2. 7‰ to 9. 5‰ (average 6. 1‰), respectively. Sulfur in sulfides was jointly contributed by bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) processes in the Nanshagou and Guanzigou deposits. The lead isotope contains significantly highly radioactive components and is in good agreement with the host rock but distinguishable with the crystalline basement, indicating that Pb in ore minerals was mainly derived from country rocks. During Silurian, seafloor hydrothermal activity may have been intensive, and seawater- generated basin brine fluids circulated and leached ore- forming materials from the host black shales. Overall, the Silurian organic matter- rich black shales played a critical role during the mineralization in the Xunyang basin in the southern Qinling region.