Role of Secondary Sulfate Minerals on Metal Recycling in an Abandoned Copper Deposit: Kuvarshan (Artvin), Northeastern Turkey

Mine tailings left at abandoned sulfide mine sites can seriously threaten surrounding ecosystems and cause soil and water pollution. This study focused on determining the geochemical processes and mineral phases controlling metal cycling in an abandoned copper mine site (Kuvarshan, Artvin, northeastern Turkey). Geochemical and mineralogical characterization studies were conducted to determine the chemical and mineral compositions of the tailings, leachates, and AMD products. In addition, kinetic tests and geochemical modeling studies were performed on the tailings to evaluate the rates and mechanisms of metal release. Oxidation of pyrite in the tailings played an important role in the formation of acidic mine drainages (pH ≈ 2.7–3.1) with high sulfate and metal contents. Sequestration of Fe and As in the AMD was controlled by jarosite precipitation. A large fraction of the total Fe (73%) and As (98%) remained in the suspended phase in the acidic water. Furthermore, the local precipitation of aragonite from alkaline mine leachates also removed zinc, copper, arsenic, and lead ions from the solution, and minimized the release of these metals into the environment. On the other hand, dissolution of secondary sulfate mineral precipitates (i.e. chalcoalumite, chalcocyanite, goslarite, coquimbite, and rozenite) contributed to the enrichment of Al, Cu, Fe, Zn, As, and Pb in the mine leachates and metal loading into a nearby stream during the wet period.