Mineral and geochemical characteristics of soils and bottom sediments in the area affected by mining dumps (a case study of the Sibay ore deposit)

Abstract

The article focuses on the chemical composition of hydrosulfates formed in bottom sediments and soils as a consequence of sulfide minerals oxidation in mining waste rock dumps. An alkaline geochemical barrier formed under the dumps reduces pollution of natural-territorial complexes. High concentrations of Zn up to 1.29%, Cu-0.74%, and Cd-27.3 mg/kg are found in the hydrosulfates formed in the river bottom and in the soils. The percentages of exchangeable copper, zinc and cadmium in their total content are 33%, 28% and 22%, respectively. Metals are actively involved in lateral and radial migration, which is regulated by alkaline and evaporation geochemical barriers. The hydrosulfates’ mineralogical composition was studied using microscopy and thermodynamic modeling. Among the secondary minerals, gypsum and iron oxyhydroxides are of primary importance, and to a lesser extent barite, epsomite, and jarosite. Secondary minerals of Cu and Zn in scattering halos are not found, which indicates the leading role of adsorption processes in their phase transitions.