Cyanides, Arsenic, and Noble Metals in Abandoned Gold Ore Cyanidation Tailings and Surface Waters in a Permafrost Region (Transbaikal Territory, Russia)
Geochemical and geophysical investigations were performed in an area of the Darasun ore cyanidation tailings impoundment, which is located in a permafrost region. The tailings contain up to 40 wt% pyrite and 5.7 wt% arsenopyrite. The purpose of this work was to determine the composition and mechanisms of transformation of the tailings and species of As, Au, Ag, Be, and Tl in drainage waters and the Darasun River before and after mixing with technogenic flows from the mining area. When the waste is oxidized because of the repeated seasonal freezing and thawing of water, three groups of chemical elements are leached: typical ore metals and impurity elements (Pb-Co-Ni-Zn-Cd and Fe-Al-Tl-Be-In), noble metals, metalloids (Au-Ag-Cu-As-Sb-Se), and post-transition metals and metalloids (Bi-Sn-Te). Drainage waters with salinities up to 5 g/L form, with concentrations of sulfate ions up to 2 g/L and cyanide up to 4 g/L, high concentrations of Au (up to 130 mu g/L), Ag (3.8 mu g/L), As (up to 350 mu g/L), and Sb (up to 1100 mu g/L), and impurity elements (Tl, In, Be, and Bi). The drainage water flows into the Darasun River, resulting in hydrochemical anomalies tens of kilometers downstream.
