Gold mineralization processes of the Huayagou gold deposit, West Qinling Orogen: Constraints from textures, in-situ sulfur isotopes and trace element compositions of pyrite

• Primary gold mineralization resulted from fluid boiling. • High-grade ores generated from superimposed mineralization by magmatic-derived fluid. • A genetic model is proposed for gold deposits in the West Qinling post-collisional extensional event. The Huayagou gold deposit, a newly discovered large-scale gold deposit (2023) in the West Qinling Orogen, hosts estimated resource of ∼ 20 t Au with an average grade of ∼ 1.69 g/t. This study investigates the ore-forming processes linked to quartz-sericite-pyrite veinlets. The combined methods of geological observations, backscattered electron (BSE) imaging, in-situ trace element and sulfur isotopes of pyrite were carried out. Four distinct pyrite generations are identified. Py1 exhibits distinctive core-rim textures and elevated concentrations of Co and Ni, indicating direct crystallization from metallogenic hydrothermal fluids. The repeated bright rims show dissolution-reprecipitation structures, suggesting reaction with later hydrothermal fluids. Py2 displays porous texture and abundant arsenopyrite inclusions, with high trace element concentrations (Ag, Cu, Au, Pb, Zn, As). This implies gold supersaturation triggered by rapid fluid boiling. Py3 preserves external dimensions of Py2 but sharp boundaries and cluster inclusion, formed via replacement through dissolution-reprecipitation of pre-existing pyrite. Trace elements (Au, As, Pb, Cu, Zn, Sb, Bi, Te) decrease from Py2 to Py3, reflecting remobilization during coupled dissolution-reprecipitation (CDR). Py4 is overgrowing on Py3 with high Co, Ni, and As concentrations, alongside diverse mineral assemblages, indicating Au mineralization triggered by fluid mixing. The sulfur isotopes of pyrite consistently range between 12.15‰ and 15.28‰, but decrease subsequently in Py4, indicating fluid superimposition in open space. A genetic model is proposed here for gold mineralization process, and thus benefits the regional gold exploration.