Supercritical ore fluids migrated upward through the structure, reactivating Py1−1 via filtration; partial Py1−1 was cemented by Pb−rich fluids (Fig. a). Continuous fluid influx recrystallized Py1−1 into euhedral Au−rich Py1−2. Simultaneous precipitation formed euhedral Py1−2 and chalcopyrite (Fig. b). Fluid replenishment generated pyrite−chalcopyrite assemblages. Py2 shows zircon−like oscillatory zoning, reflecting periodic compositional changes during growth. This indicates fluid oscillations, with Au, Pb, Cu, Ag, and Sb enriched at zoning margins (Fig. c). Py2 contains higher Au concentrations than Py1−2. Py3−forming fluids were supplied before Py2 fluids were fully depleted. Sulfide precipitation depleted sulfur, lowering sulfur fugacity and raising Te/S fugacity ratios. Tellurium exists in sulfide lattices in the crust. Independent telluride formation requires low S fugacity, high Te fugacity, or high Te/S fugacity ratios. This explains the presence of calaverite and other tellurides in the Au−rich V1 orebody, where Au’s high Te affinity corresponds to visible gold in Py2/Py3 fractures (Fig. c). The mineralogy of the Au−rich V1 orebody suggests seafloor or near−seafloor formation. Continuous hydrothermal fluid supply in this setting drove metal mineral precipitation. The fine−grained, patchy distribution of native gold and calaverite in the V1 orebody reflects fluid mixing and unstable systems. Fluid evolution generated the Py3−chalcopyrite−sphalerite−galena assemblage. During volcanic quiescence, ore fluids ascended through tectonic structures via magmatic hydrothermal systems. Seafloor venting of these fluids, driven by temperature decline, caused sulfide and gold precipitation, forming Au−rich massive sulfide deposits. • Present micro-textures and in situ sulfur isotopic and elemental compositions of iron-sulfides from Dapingzhang deposit. • Invisible gold-bearing sulfides mainly comprise of and pyrite, and gold-bearing pyrite was formed in a metal − rich, low − temperature fluid environment. • Gold enrichment and hosting sulfides precipitation are controlled by episodic influx of magmatic hydrothermal fluids with variational temperature. The Dapingzhang Cu − Au polymetallic deposit is a large volcanogenic massive sulfide (VMS) deposit formed during the Proto − Tethyan stage in western Yunnan Province, SW China, and exhibits a stratified distribution with upper massive orebodies (V1) and lower veinlet orebodies (V2). Au − rich orebodies predominantly occur within the massive orebodies near the 16 # exploration line. This study investigates the microstructures, trace elemental, and sulfur isotopic compositions of pyrite, chalcopyrite, and sphalerite from the Au − rich orebodies at 1150 m and 1130 m levels to constrain the Au-bearing hydrothermal fluid sources, migration, and ore genesis. Four pyrite types were identified, representing three mineralization stages: (1) early-stage Py1 − 1 with sedimentary-formed strawberry − like textures; (2) late-stage Py1 − 2 formed through Py1 − 1 aggregation into irregular or euhedral crystals; and (3) Py2 (first-order zoning on Py1 − 2) and Py3 (second-order zoning on Py2). All Py1 − 2, Py2, and Py3 are hydrothermal in origin. Trace elemental composition reveals higher Sb concentrations in pyrite at the 1150 m level compared to those at the 1130 m level, with similar concentrating trends of Cu, Pb, Au, and Se. Evolutionary sequence analysis shows increasing Cu and Au concentrations but decreasing Co and Se concentrations in Py1 − 2, Py2, and Py3 across both the 1150 m and 1130 m levels. All pyrites are enriched in Au, Cu, Pb, Zn, and Sb but are depleted in Co, Ni, Tl, Se, Ti, and Sn. Sulfur isotope values (δ 34 S = − 2.63 to + 1.12‰) of pyrite, chalcopyrite, and sphalerite suggest a magmatic sulfur affinity. Gold mineralization is associated with E − W-trending ore-conducting faults. Au − rich fluids migrated upward through fractures, leaching Py1 − 1 to form inclusion textures and causing localized recrystallization that produced Au − enriched Py1 − 2. Continuous fluid replenishment generated Au − rich Py2. Since Py2 − forming fluids were not fully consumed, Py3 − forming fluids added more Au, reaching supersaturation and precipitating native gold and calaverite within Py2 − Py3 intergrowths and fractures. Sustained fluid supply ultimately formed the Au − rich orebodies.
Ru et al. (Tue,) studied this question.