Metallogenic model and deep ore prospecting direction of the Zhazixi Sb-W-Au deposit in Western Hunan, South China

The Zhazixi Sb-W-Au deposit is a typical quartz vein-type located in the Xuefeng curved metallogenic belt, Hunan Province. However, the genetic mechanism and metallogenic regularity of the deposit remain poorly understood, and the occurrence of gold is still unclear, which restricts the determination of deep prospecting directions. This study systematically investigates major and trace elements (including REEs), fluid inclusions and sulfur isotope analysis of ore and wall rocks from the Zhazixi deposit, in order to elucidate the source of ore-forming materials, to characterize the ore-forming fluids, and establish the metallogenic model and prospecting model of Sb-W-Au deposit in the area. The results show that gold primarily occurs in pyrite and arsenopyrite, and mainly as inclusion gold with high content. Elements closely associated with Au are As, Hg, Sb, and S. Additionally, gold mineralization is closely related to tungsten and antimony mineralization. The analyzed rocks exhibit significant depletion in Sr, Nd and Y, and enrichment in large ion lithophile elements (LILE, e.g., Rb, Th) and high field strength elements (HFSE, e.g., Zr, Hf). They are also characterized by enrichment of LREE and depletion of HREE, with a right-inclined chondrite-normalized distribution pattern. The δ ³⁴ S values range from 4.39‰ to 13.80‰. The ore-forming fluids are characterized by low to medium temperature, medium salinity, and low density. Fluid inclusions show homogenization temperature ranging from of 177–222℃, with salinities varying from 9.9 wt% and 24.8wt%. The estimated metallogenic pressure and depth range from 14.5 to 31.5 MPa, and 0.58 to 1.26 km, respectively. The obtained data from different analytical techniques is suggestive that the ore-forming materials of the Zhazixi deposit are derived from multiple sources. These findings suggest a mixed-source origin for both the ore-forming materials and fluids. The metals were derived from both the ore-bearing strata and deep-seated magmatic sources, implying a crust–mantle hybrid signature. The ore-forming fluids likely resulted from the mixing of magmatic fluids and meteoric water. Based on the integrated data, a tectono-metallogenic model is proposed in which regional metamorphism and associated thermal activity mobilized Sb, W, and Au from the “source bed,” facilitating their precipitation in structurally and lithologically traps. Deep magmatic activity played an indirect but significant role by contributing heat and supplementary ore components. Notably, the increasing Au grade at depth in the main ore veins indicates considerable potential for deep-targeted gold exploration.