Silver geochemistry and isotope systematics in Ag-rich mine tailings from Namibia

Inthis study, wepresent adetailed geochemical characterisation and stable isotope systematics ofsilver(Ag) inamining waste facility atthe Namib Lead & Zinc mine inNamibia (Africa). Weexamined aseries offlotation tailings and ore minerals toaddress two principal questions: (1) the distribution, chemical form and leachability ofAg, and (2)the local Ag isotopic signature(s) and its variability inrelation toAg speciation inthe solid phase, aswell asthe fate ofstable Ag isotopes. Our findings reveal asignificant correlation between Ag and Pb concentrations, indicating that galena isthe primary Ag carrier. Most importantly, all mild extractions mobilised only aminimal amount ofAg (≤ 1wt.% ofthe total amount). This suggests that most Ag isassociated with geochemically stable phases, specifically sulphides, which are not subjected toleaching and/or intensive weathering. Unlike other isotope studies, the present research demonstrates ahomogeneous Ag isotopic signal inthe tailings and individual ore samples with anaverage δ109Ag value of ~ 0‰ (± 0.1, 2SD). Therefore, this study provides new knowledge and clearly supports the use of Ag isotopic data to track primary Ag sources globally, not only in Africa.