Features of noble metals at Pioneer gold deposit

The purpose of the present study is to evaluate the mass fractions of the group of noble metals (gold, silver, platinum, ruthenium, osmium, palladium, iridium, rhodium) in the ores and host rocks of the Pioneer deposit (the Upper Amur Region, Russia) and to determine their migration activity and hydrochemical classification of ore metals by sizes. The object of the study is primary and oxidized ores, as well as rocks hosting this mineralization. The study employs the method of quantitative chemical analysis, micro assay melting with an error of correctness, accuracy and reproducibility of the results of ≤30 %. Pioneer is a near surface hydrothermal deposit with oxidized and sulfide types of ores, which are processed both by the open method of alkaline heap cyanide leaching, and by the closed pressure method, respectively. A gold concentration plant was built to implement these processing methods. The main recoverable component of this technology is gold, whereas silver and platinum group metals are present in industrial products as impurities. The technology is highly profitable, which allows cost-effective processing of ores with the mass fractions of 1–4 ppm of gold. The performed hydrochemical classification of the sizes of native gold minerals has showed that the bulk of the nuggets (74– 78 %) of primary, sulfide, and oxidized ores accounts for the fraction with the sizes of 160–1000 μm and 11–13 % account for the fraction with sizes of 16–40 μm. Fine gold of the deposit provides its complete dissolution during the cyanidation process.