Native gold and its satellite minerals were studied throughout the 300 m section of oxidized ores of the Olympiada deposit (Eastern Siberia, Russia). Three zones are identified in the studied section: Upper Zone ~60 g/t Au; Middle Zone ~3 g/t Au; Lower Zone ~20 g/t Au. Supergene and hypogene native gold have been found in these zones. Supergene gold crystals (~1 μm), their aggregates and their globules (100 nm to 1 μm) predominate in the Upper and less in Middle Zone. Relic hypogene gold particles (flattened, fracture and irregular morphology) are sporadically distributed throughout the section. Spongiform gold occurs in the Lower Zone at the boundary with the bedrock, as well as in the bedrock. This gold formed in the process of oxidation of aurostibite, leaching of impurities and its further dissolution. Hypogene gold is commonly isolated but for supergene gold typically associated with ferric (hydr)oxides. New formation of gold occurred due to oxidation of sulfide ores and release of “invisible” gold, as well as dissolution, mobilization and re-deposition of metallic hypogene gold. A model for the formation of oxidized ores with the participation of meteoric and low-temperature hydrothermal waters has been proposed.

The Mössbauer spectroscopy method was used to study the ligand microstructure of natural arsenopyrite (31 specimens) from the ores of the major gold deposits of the Yenisei Ridge (Eastern Siberia, Russia). Arsenopyrite and native gold are paragenetic minerals in the ore; meanwhile, arsenopyrite is frequently a gold carrier. We detected iron positions with variable distribution of sulfur and arsenic anions at the vertexes of the coordination octahedron {6S}, {5S1As}, {4S2As}, {3S3As}, {2S4As}, {1S5As}, {6As} in the mineral structure. Iron atoms with reduced local symmetry in tetrahedral cavities, as well as iron in the high-spin condition with a high local symmetry of the first coordination sphere, were identified. The configuration {3S3As} typical for the stoichiometric arsenopyrite is the most occupied. The occupation degree of other configurations is not subordinated to the statistic distribution and varies within a wide range. The presence of configurations {6S}, {3S3As}, {6As} and their variable occupation degree indicate that natural arsenopyrites are solid pyrite {6S}, arsenopyrite {3S3As}, and loellingite {6As} solutions, with the thermodynamic preference to the formation of configurations in the arsenopyrite–pyrite–loellingite order. It is assumed that in the variations as part of the coordination octahedron, the iron output to the tetrahedral positions and the presence of high-spin Fe cations depend on the physical and chemical conditions of the mineral formation. It was identified that the increased gold concentrations are typical for arsenopyrites with an elevated content of sulfur or arsenic and correlate with the increase of the occupation degree of configurations {5S1As}, {4S2As}, {1S5As}, reduction of the share of {3S3As}, and the amount of iron in tetrahedral cavities.

40Ar/39Ar dates on the quartz–micaceous–sulfide, quartz–gold–arsenopyrite–pyrrhotite, and quartz–gold–stibium associations at the superlarge (>1000 t Au) Olimpiada gold deposit, the Yenisei...

The gold and platinum-group elements (PGE) mineralization of the Guli and Kresty intrusions was formed in the process of polyphase magmatism of the central type during the Permian and Triassic age. It is suggested that native osmium and iridium crystal nuclei were formed in the mantle at earlier high-temperature events of magma generation of the mantle substratum in the interval of 765–545 Ma and were brought by meimechite melts to the area of development of magmatic bodies. The pulsating magmatism of the later phases assisted in particle enlargement. Native gold was crystallized at a temperature of 415–200 °C at the hydrothermal-metasomatic stages of the meimechite, melilite, foidolite and carbonatite magmatism. The association of minerals of precious metals with oily, resinous and asphaltene bitumen testifies to the genetic relation of the mineralization to carbonaceous metasomatism. Identifying the carbonaceous gold and platinoid ore formation associated genetically with the parental formation of ultramafic, alkaline rocks and carbonatites is suggested.

Subsoil users take practical interest in tailings piles of gold mines. The composition the Olimpiada processing plant tailings was tested in order to determine feasibility of secondary gold recovery. Mineral associations of oxidized ore, primary ore and tailings are described. It is found that both ore and tailings have analogous qualitative composition of minerals. Supergene minerals of iron, arsenic, antimony and tungsten are widely spread over tailings ponds. Gold content is lower in tailings than in ore by an order of magnitude. Native gold is detected in the form of free particles in classes -0.07+0.045 and -0.045+0 mm after additional milling of tailings. Splintered grains of gold-bearing minerals—aurostibite and johnasonite—are also found in coarser size grades of tailings without pre-milling. As compared with ore, tailings contain mobile gold (water-soluble, adsorbed and ferri-form) of about 15–20%. It is recommended to carry out re-extraction of gold from tailings after pre-milling down to size grade -0.071 mm at the content up to 90%. It is possible that the precious metal accumulates in the water solution of the tailings ponds with time; for this reason, it is advised to undertake monitoring of gold content in the liquid phase of tailings ponds and to find efficient technologies of gold recovery. Images in Figs. 1 and 2 and mineral diagnostics accomplished in the mode of back-scattered electrons on the scanning electron microscope Hitachi S-3400N with the energy dispersion spectrometer Bruker XFlash 5010 by the Assistant–Operator S. S. Ilienok, Geoecology and Geochemistry Chair, Tomsk Polytechnic University.The study was supported in the framework of the state contract with the Ministry of Education and Science of the Russian Federation, Project No. 5.2352.2017/RSN.