Gold in Porphyry Copper Deposits

This study examines the geochemical insights into the mineralogical forms of gold in porphyry copper and Carlin-type deposits, which are integral to a significant portion of global gold production. The objective is to investigate the traditional assumptions regarding gold precipitation in these deposits, primarily focusing on whether gold appears as native gold or electrum. Through a review of existing literature and experimental data involving the Cu-Fe-S-Au system, the methodology includes assessing mineral associations and gold-hosting capacities of common sulphide minerals like bornite and chalcopyrite. The results illustrate that a large portion of gold may actually exist in solid solution within sulphide minerals, challenging previous assumptions. Additionally, it was found that bornite can host significantly more gold than chalcopyrite at varying temperatures, providing a clearer understanding of geological factors that could lead to the discovery of new deposits. This research contributes to a refined comprehension of gold geochemistry during the formation of porphyry copper deposits, suggesting that the visible gold often associated with artisanal mining operations may not reflect the primary occurrences in these complex mineral environments.