Composition and Ligand Microstructure of Arsenopyrite from Gold Ore Deposits of the Yenisei Ridge (Eastern Siberia, Russia)

Abstract

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.

Synthesis and characterization of nanoscale composite particles formed by 2D layers of Cu-Fe sulfide and Mg-based hydroxide

“…Isomer shifts (IS) are given relative to α-iron at room temperature. Probabilities P of quadrupole splitting P(QS) and magnetic hyperfine fields P(H) were first determined from the experimental spectra and were used to generate a model spectrum and then to fit the results by varying the complete set of parameters [54].…”

Gold in the Oxidized Ores of the Olympiada Deposit (Eastern Siberia, Russia)

“…The share of such gold can reach 40-60%, and its extraction is carried out by JSC Polyus Krasnoyarsk using its own bio-oxidation technology BIONORD ® [36]. "Invisible" gold is confined to sulfide minerals of the deposit, first of all, to needle-like arsenopyrite of the early association, in which its concentrations range from 0.0n to 2298 ppm [37,38]. According to modern ideas, "invisible" gold in arsenopyrite is present in the form of nanosized Au 0 inclusions and in a structurally bound form [38][39][40].…”

“…"Invisible" gold is confined to sulfide minerals of the deposit, first of all, to needle-like arsenopyrite of the early association, in which its concentrations range from 0.0n to 2298 ppm [37,38]. According to modern ideas, "invisible" gold in arsenopyrite is present in the form of nanosized Au 0 inclusions and in a structurally bound form [38][39][40]. Earlier Mössbauer studies on 197 Au atoms for gold-bearing arsenopyrite of the Olympiada deposit showed that the content of structurally bound and nanosized metallic gold varies between 3 and 45% and 55 and 97%, respectively [37].…”

Editorial for Special Issue: “Mineralogy of Noble Metals and “Invisible” Speciations of These Elements in Natural Systems”

“…The third part of the issue contains two articles on Au-bearing arsenopyrite and pyrite [17,18]. A significant number of studies are devoted to Au and other noble metals in these minerals.…”

“…Sazonov and coauthors [17] used the Mössbauer spectroscopy method to study the ligand microstructure of natural arsenopyrites from the ores of major gold deposits of the Yenisei Ridge (Eastern Siberia, Russia). The elevated gold concentrations typical of arsenopyrites occur with an elevated content of sulfur or arsenic and correlate with the increase in the occupation degree of configurations {5S1As}, {4S2As}, {1S5As}, the reduction in the share of {3S3As}, and the amount of iron in tetrahedral cavities.…”