Mineralogical characteristics of gold-bearing pyrite and gold occurrence regularity of the Jiadi gold deposit in southwestern Guizhou Province

Southwestern Guizhou is one of the main producing areas of Carlin-type gold deposits in China. The Jiadi gold deposit is a newly discovered Carlin-type one hosted in basalt in southwestern Guizhou in recent years, and the occurrence state of gold has long been the focus of attention. Previous studies have shown that arsenic-bearing pyrite is the main gold-bearing mineral in the Jiadi gold deposit. However, there has been a lack of in-depth research on the gold-bearing pyrite and the gold occurrence law in the Jiadi gold deposit. Based on the field investigation and indoor microlithographic observation, the pyrites in the mine were divided into different phases first; then, the electronic probe analysis method was used to study the pyrites of different phases. The results show that S and As of pyrite have an obvious negative correlation, and Au and As have a certain positive correlation. Ore-predating pyrite, ore-forming pyrite and post-ore pyrite share similarity of high contents of S, Fe and low contents of As, Au. The ring of the ore-forming pyrite has the characteristics of high As and Au, different that of the post-ore pyrite (high As without Au), indicating that two types of pyrites belong to different hydrothermal events. The crystallization sequence of the gold-bearing pyrite in the mine is summarized as follows: Strawberry-like acyclic pyrite of low-arsenic→arsenic, ringing pyrite (containing gold) and homogeneous apyrite fine-grained pyrite→high-arsenic ring pyrite (without gold). This conclusion has certain directive significance for the prospecting and exploration in the Jiadi gold deposit.