Mineralization of the Sawayaerdun gold deposit, South Tianshan, Northwest China: Insights from texture and geochemistry of multistage pyrite and arsenopyrite

Abstract The Sawayaerdun gold deposit (3.7 Moz at 1.38 g/t Au), located in the South Tianshan orogen, Northwest China, is distinguished by deformed quartz-sulfide veins and veinlets overprinted by extensive quartz-sulfide stockworks. The paragenesis is delineated into four distinct stages: (0) preore framboidal pyrite (Py0) within carbonaceous slate interlayers, (1) early-ore deformed, porous pyrite (Py1) and arsenopyrite aggregates (Apy1), (2) main-ore zoned pyrite (Py2) and rhombic arsenopyrite (Apy2), and (3) late-ore anhedral pyrite (Py3). Diagenetic Py0 is notably enriched in gold (mean of 4.62 ppm), As, Co, Ni, Ti, Ba, and W. Py1 formed during the brittle–ductile transition and exhibits reduced gold concentrations (mean = 0.35 ppm). Subsequent dissolution–reprecipitation processes introduced low invisible gold (mean of 0.66 ppm in Py2), along with elevated As, Co, W, Ti, and Ba contents. Py3 displays negligible or undetectable gold content. Almost all pyrite types exhibit low Co/Ni ratios (