From Polymetallic Ores to Mine Tailings: Integrated Environmental and Resource Assessment in the Leninogorsk Ore District, Eastern Kazakhstan

Mine tailings from polymetallic ore processing may retain substantial inventories of valuable metals and therefore represent both a legacy environmental concern and a potential secondary mineral resource. This study evaluates three tailings storage facilities (TSFs) of different ages and operational histories—Talovskoye, Chashinskoye, and Starooye—in the Leninogorsk mining district, Rudny Altai, Eastern Kazakhstan. An integrated approach combining bulk geochemistry, the geoaccumulation index (Igeo), acid–base accounting, pH-dependent element mobility tests, and Landsat-derived NDVI for 2002–2026 was used to assess residual metal enrichment, geochemical stability, and the potential relevance of the tailings for future reprocessing. The tailings retain a distinct polymetallic signature dominated by Zn, Pb, and Cu, together with Cd, In, Ge, Te, Se, Au, Ag, and other associated elements. Their distribution varies considerably among the three facilities, indicating that potentially valuable components remain in materials produced during different stages of beneficiation history. The active Talovskoye TSF has the highest acid potential (128.75 kg CaCO3/t), a positive net acid-producing potential (NAPP = +17.50 kg CaCO3/t), an NPR of 0.86, the highest maximum element mobility (34.07%), and the lowest mean NDVI (0.029). In contrast, the older Chashinskoye and Starooye TSFs have negative NAPP values, substantially greater neutralization capacities, lower maximum mobility, and more developed vegetation cover. Starooye is of particular interest because a relatively stable vegetated surface and high neutralization capacity coexist with strong residual enrichment in several ore-related and associated elements. Thus, surface stabilization does not necessarily indicate either geochemical depletion or the absence of secondary-resource potential. The results show that residual metal inventories, element mobility, acid–base properties, and surface conditions need to be considered together when evaluating historical tailings. This approach provides a basis for identifying tailings that merit further mineralogical and metallurgical investigation before their technical and economic suitability for reprocessing can be established.