Genesis and mineralization implications of dissolution-regrowth pyrite in the large Qukulekedong Au-Sb deposit, East Kunlun, NW China

The Qukulekedong deposit is a recently discovered large Au-Sb deposit in the western part of the East Kunlun Orogenic Belt, NW China. Pyrite with a characteristic dissolution-regrowth texture has developed in the high-grade Au ore of the deposit. In this study, information on the mineralogical properties, elements distribution, and in situ S isotopic composition of the dissolution-regrowth pyrite was used to interpret its genesis and relationship to Au concentration. The pyrite grains are composed of a core, mantle, and rim. The core consists of pyrite with delta 34S values ranging from 1.02 %o to 1.99 %o, indicating a neutral pH, medium-oxygen fugacity environment. The mantle consists of sphalerite, sericite, quartz, and ankerite with dissolution texture, indicating pyrite dissolution and replacement in a neutral pH, high-oxygen fugacity environment. The rim consists of pyrite with fine arsenopyrite inclusions and recovers the crystal shape of the pyrite, which have delta 34S values ranging from 1.60 %o to 2.67 %o. This indicates that the rim was formed via regrowth in a neutral pH, low-oxygen fugacity environment. The dissolution of the mantle and regrowth of the rim represent an oxygen fugacity increa-sing-decreasing process in the formation of pyrite. The increase in oxygen fugacity could remobilize Au from dissolved pyrite, forming a highly Au-concentrated hydrothermal fluid. The decrease in oxygen fugacity trig-gered the supersaturation and precipitation of Au, forming an Au-rich rim. Combining geological characteristics, the pyrite likely had a magmatic sulfur origin and formed via a dissolution-regrowth process caused by the depressurization-oxidation associated with rock fractures. The dissolution-regrowth pyrite can be used as a mineralogical indicator for regional Au exploration.