Genesis of the Nanyangtian W deposit in southeastern Yunnan: Evidences from in situ analyses of trace element and sulfur isotope in sulfides

<p indent="0mm"> The Nanyangtian W deposit, located in the Laojunshan Sn-W polymetallic ore district, is the largest W deposit in Yunnan Province. Whether the deposit has the multi-stage superimposed mineralization governed by the Yanshanian magmatic-hydrothermal activity and Indosinian regional metamorphism is a key scientific problem to be resolved urgently. The material sources of multiple types of mineralization and the variations in metallogenic physical and chemical conditions for the Nanyangtian W deposit have been identified in this work by using <italic>in-situ</italic> analyses of trace elements and sulfur isotopes of primary sulfides of different types of mineralization in the deposit. The consistent S isotopic compositions of sulfides (with δ³⁴S values mainly between 4~10‰) and the general relatively high Se/S values of pyrites suggest that ore-forming materials of both the hydrothermal quartz-vein-type mineralization and skarn-type mineralization was sourced from magma. The relatively low Co/Ni (&lt;1) ratios of sulfides indicate that the fluid was contaminated by materials of strata in the upward migration process of fluid. Pyrites and pyrrhotites in ores of different mineralization types have obvious different compositions of trace elements, indicating that the ore-forming fluid of the quartz vein-type mineralization has relatively low temperature, salinity, and relatively high oxygen fugacity than that of the skarn mineralization, this is probably attributed to the involvement of meteoric water in the mineralization process of the deposit. The skarn mineralization and quartz vein–type mineralization could represent different mineralization stages of the same magmatic–hydrothermal system.