Mineralogical Characteristics and Metallogenic Indication of Gold−Bearing Sulfides in the Jinpenliang Gold Deposit, Zhashui−Shanyang Ore Cluster Area, South Qinling

The Jinpenliang gold deposit is located in the northern part of the Zhashui−Shanyang ore cluster area, South Qinling. The E−W trending main orebodies, occurring in sedimentary rocks of the Upper Devonian Tongyusi Formation, are strictly controlled by the left−lateral ductile faults. To date, there is still insufficient understanding of the ore mineralogy and gold mineralization processes. In this paper, we obtain data from a variety of experimental methods, such as petrographic identification, Back−Scattered Electron imaging (BSE), Energy Dispersive Spectrometry (EDS), and Electron Probe Micro−Analysis (EPMA), to determine the mineralogical characteristics of gold−bearing sulfides (arsenopyrite, pyrite, stibnite, and marcasite), and discuss the chemical states of Au and physicochemical conditions for gold mineralization. The results show that the micro−disseminated gold mineralization in hydrothermal period can be divided into three stages: pyrite−arsenopyrite−silicification stage (Ⅰ), quartz−stibnite−marcasite±antimony oxides stage (Ⅱ), and calcite−quartz stage (Ⅲ). The occurrence states of “invisible gold” vary greatly among different gold−bearing sulfides, from Au⁺ in arsenopyrite to Au⁺ and Au⁰ in early generation pyrite (Py-1), then to Au⁰ in late generation pyrite (Py-2) and marcasite. The metal mineral assemblage changes from arsenopyrite−pyrite to stibnite−marcasite, while the ore−forming fluid gradually evolves from relatively high−temperature solutions unsaturated with respect to native gold to low−temperature solutions saturated with respect to native gold. The Jinpenliang gold deposit is a Carlin−type gold deposit, which was formed in a medium−high temperature and shallow−moderate depth with logf(S₂) ranging from −8.5 to −4.5.