Distribution, occurrence and enrichment mechanism of key metals of selenium, tellurium and cobalt in Wushan copper deposit, Jiurui ore concentration area, Jiangxi Province

The Wushan copper deposit is a typical stratiform-contact skarn-type copper polymetallic deposit in the Jiurui ore cluster of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt. The copper reserves of the deposit are large, along side the presence of essential metal minerals including selenium, tellurium, cobalt, gallium, and thallium, suggesting promising opportunities for the comprehensive utilization of mineral resources. Nevertheless, there remains a dearth of research regarding the distribution patterns, occurrence states, and enrichment mechanisms of these key metals within the deposit. In this study, representative rocks and ore samples were collected from three exploration lines (W3-2, S4-2, N6-1) of the contact zone skarn-type ore body in the southern mining area, three exploration lines (E9-2, E2-1, W4-1) of the stratiform sulfide -type ore body and one exploration line ( E7-3) of the stratiform skarn-type ore body in the northern mining area. The spatial distribution patterns and occurrence states of selenium, tellurium, cobalt and other key metals in the deposit were investigated by using optical microscopy, scanning electron microscopy, whole -rock chemical analysis, and in -situ LA-ICP-MS trace element testing. Additionally, the migration and precipitation mechanisms of selenium, tellurium and cobalt were preliminarily discussed. The results showed that the estimated resource reserves of selenium, tellurium and cobalt in the deposit amounting to 5513t, 611t and 9597t, respectively, all reaching large to medium scales. The Wushan deposit has the highest selenium content and the largest selenium potential resource among the metal deposits in the metallogenic belt. Furthermore, the Se, Te and Co contents in the northern ore bodies, where significantly higher than that in the southern mining area, increased regularly from the central mineralization center towards the east and west ends of the northern mining area. Meanwhile, a strong positive correlation was observed between the concentrations of Se, Te, and Co in the ore and the S content, with the sulfide content serving as the primary controlling factor for the abundance of key metals in the ore. Besides, selenium and cobalt were predominantly concentrated in chalcopyrite-type, copper-bearing skarn-type (high sulfur) and copper-bearing dolomite -type ores. Tellurium, on the other hand, was mainly enriched in chalcopyrite-type and copper-bearing dolomite -type ores. Selenium and tellurium were mainly present in the form of isomorphic substitution in independent minerals and sulfides, whereas cobalt mainly incorporated into the lattice of pyrite minerals in the form of Coe + isomorphic substitution. Selenium and tellurium gradually precipitated and enriched as the temperature of the mineralizing fluid decreased, the sulfur fugacity increased, the oxygen fugacity decreased, and the pH value increased, while cobalt mainly enriched within pyrrhotite through sulfides precipitate.