Geochemical criteria for gold content of primary and oxidized ores of the Sokhatin deposit (North-East Russia)

Abstract

Introduction: the Sokhatin gold deposit is localized in the Proterozoic metamorphic strata of one of the blocks of the Prikolyma terrane, where until recently gold was mined only from placers. The development of primary deposits has begun in recent years, and many issues of their genesis and criteria for predicting mineralization have not been fully resolved. In addition, the Sokhatinoye deposit differs from analogous objects in the region in the composition of ore-hosting rocks, ore mineralogy, their geochemical characteristics and the degree of preservation of weathering crusts, which determines the need to develop criteria for the gold content of primary and oxidized ores.

Methodology: multielement inductively coupled plasma mass spectrometry (ICP-MS) and silicate analysis using inductively coupled plasma emission spectrometry (ICP-OES) were used to study the composition of ores and host rocks. The composition of primary and oxidized ore minerals was studied using a TESCAN VEGA 3 electron microscope with an Oxford energy dispersive attachment. To study the mineralogy of primary and oxidized ores, a RIGAKU ULTIMA IV X-ray diffractometer was used. To assess the degree of sulfide oxidation, a phase analysis of total sulfur and sulfate sulfur was performed.

Results and discussion: as a result of the studies, a complex of indicator elements associated with gold mineralization was established, including Ag, Bi, Te, Pb, As, Cu, Se, W, Mo, Sb, Cd, Zn, Sn, Tl. Ores formed from muscovite-quartz and quartz-epidote-chlorite schists differ significantly in the contents of Pb, Zn, Cu, V, Mn, P, Co, Ni, Fe. During the oxidation of ores, Al₂O₃, P₂O₅, TiO₂, Pb, Zn, Cd, As, Sb, Sn accumulate and S, Cr are removed. In the hypergenesis zone, the dispersion of Au contents increases, the average sample of native gold increases from 744 ‰ to 858 ‰.

Conclusions: indicator elements of gold mineralization form zonally constructed anomalous geochemical fields with concentrations of Au, Ag, As, Bi, and Mo in ore bodies against the background of more extensive complex anomalies of Pb, Cu, Te, Se, and W associated with beresite zones. The outer contour of the ore zones is marked by the Be, Sb, Tl association.