Electrochemical gold precipitation to explain extensive vertical and lateral mineralization in the world-class Poderosa-Pataz district, Peru

Gaboury D.; Oré Sanchez C. · Terra Nova (2020) · DOI: 10.1111/ter.12440

Resumen

The world-class Poderosa-Pataz district is famous for its gold endowment in vertically and laterally extensive quartz-sulphide veins. Precipitating mechanisms are investigated to determine why gold is so laterally and vertically distributed. Micro-XRF and LA-ICP-MS element mapping of pyrites surrounding gold grains reveals systematic enrichment of As around or near visible gold accumulations. These As-enriched zones define discordant rims and corridors overprinting pyrites. LA-ICP-MS spot analyses performed within and outside the As enrichment zones indicate that As is enriched on average by two orders of magnitude in association with gold. Secondary pyrite transformation by hydrothermal fluids with elevated As-Au induced a change in the semiconducting properties of pyrite grains, resulting in the precipitation of visible gold particles at the interfaces of As-enriched zones. The electrochemical precipitation mechanism acted as a filter to extract gold in solution regardless of variations in pressure and temperature, hence explaining the vertically and laterally extensive gold mineralization.