Isotopic geochemistry of the Nanjiaohe silver polymetallic ore deposit in Yunnan

The study of isotopic geochemistry of the minerals from the Nanjiaohe silver polymetallic ore deposit in Yunnan shows that the quartz inclusions have the homogenization temperatures ranging from 100 to 148℃, δD_H2O values ranging from -91.9 to -69.0‰, δ¹⁸O values ranging from -15.60 to -5.66‰. The ore-forming fluids are derived chiefly from fossil meteoric water, with a small amount of magmatic water. The ores have the δ³⁴S values ranging from -2.18 to 5.95‰, with an average of 2.15‰, that is deviated from the fields of meteoritic sulphur but closer to those of the sulphur in basic rocks. The sulphur in the ores is originated from deep-seated hydrothermal fluids. The study of lead isotopic compositions indicates that the Lincang granite masses consist of the upper and lower crust and upper mantle material. The lead isotopic compositions in the ores fall mostly into or near the fields of the orogenic zones indicated by the model from Zartman and Doe, suggesting a mixed crust-mantle origin of lead.