Occurrence Characteristics and Enrichment Mechanism of Au in Shuiyindong Gold Deposit in Southwestern Guizhou Province, <scp>Southwest</scp> China

ABSTRACT This paper aims to address the controversy surrounding the occurrence state, enrichment and precipitation mechanism of gold in the Shuiyindong gold deposit, which has been extensively discussed by several authors. To this end, pyrite and arsenopyrite in the high‐grade ores of the deposit were considered as the research objects. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were used to determine the morphology and elemental content of the growth zonal of pyrite and arsenopyrite–pyrite aggregates. The occurrence and distribution of Au was analysed, and its enrichment and precipitation mechanisms are discussed herein. The findings of this paper indicate that gold mainly occurs in the growth annulus of pyrite and arsenopyrite of the pyrite–arsenopyrite aggregate. Furthermore, the emergence of ‘giant grains’ (200 μm) of ‘native gold’ was observed. Gold primarily participates in the lattice structure of pyrite and arsenopyrite in the form of Au + , but also occurs less commonly as Au 0 . Moreover, ‘giant grains’ of natural gold were observed in host rocks exhibiting dolomitisation and/or calcilisation, and in quartz veinlets. Notably, Au + mainly replaces the S of pyrite and arsenopyrite by isomorphism in a relatively closed environment, whereas Au 0 and native gold form by the rapid precipitation of Au‐rich saturated and supersaturated hydrothermal fluids in a relatively open environment.