Gold (Au) as a by-product of porphyry copper deposit mining

Au (Gold) is an important by-product of porphyry copper deposits (PCDs) that adds to the overall economic potential of large copper mining projects. PCDs, which develop in subduction zone magmatic-hydrothermal systems, host gold in predominantly sulfide minerals, including chalcopyrite, bornite, and pyrite. Gold grades in PCDs are highly heterogeneous but typically vary from 0.2 to 1.0 g/t. Although gold is largely mined as a by-product, some porphyry systems, like Grasberg in Indonesia and Cadia-Ridgeway in Australia, contain high enough gold grades to qualify as gold-rich deposits. Gold in these deposits is recovered by flotation, smelting, and refining, with cyanide leaching occasionally to recover the remaining gold from tailings. The largest producers of porphyry copper systems in the world are China, Australia, and Russia. Gold is an important component of global trade, industry, and investment, finding uses in electronics, medical technologies, and monetary reserves. Its price varies according to economic performance, geopolitical stability, and supply-demand relations. This paper discusses the geological occurrence, mining, processing, water use, social and environmental effects, waste disposal, and regulatory aspects of gold production from porphyry copper ores and evaluates its viability as a by-product source to satisfy worldwide demand.