Genesis and mineral exploration of the Daqishan Lead-Zinc Deposit, Beishan orogenic Belt, NW China: Constraints from In-Situ trace element compositions of Sphalerite, Pyrite, and Chalcopyrite

Abstract

The Daqishan deposit is located in the Beishan orogenic belt, with a Pb + Zn metal reserve of 108 kilotons, qualifying it as a medium-sized deposit. Through the field investigations and microscopic observations, this study divides the Daqishan deposit’s ore-forming process into three stages: (I) Quartz-pyrite stage; (II) Quartz + calcite + sphalerite + galena + pyrite stage; (III) Quartz + chalcopyrite + cassiterite + silver minerals stage. To explore the distribution and substitution mechanisms of trace elements in key minerals and clarify the deposit’s genesis, LA-ICP-MS was employed for in situ analysis of trace element compositions in sphalerite, pyrite, and chalcopyrite from different stages. In sphalerite, trace elements including Fe, Mn, Cd, Co, In, and Ag are mainly integrated into the mineral lattice through isomorphism. In pyrite, Co and Ni are primarily incorporated via coupled substitution, while in chalcopyrite, In, Ag, and Sn are predominantly integrated through coupled substitution. The Co/Ni ratio and As content in pyrite suggest the mineral formed in a medium- to low-temperature environment, with temperatures decreasing as mineralization advanced. The Ga/In and Zn/Cd ratios in sphalerite indicate its formation under medium- to low-temperature conditions, with higher temperatures during the main mineralization stage. Collectively, the mineralization of the Daqishan Pb-Zn deposit is inferred to result from multiple episodes of pulsed mineralization by ore-forming fluids, there remains potential for discovering copper-tin mineralization at depth and in peripheral areas of the deposit. Based on trace element characteristics of sphalerite and pyrite, the Daqishan deposit is classified as an epithermal deposit.