TRACE ELEMENT GEOCHEMISTRY AND METAL MOBILITY OF OXIDE MINERALIZATION AT THE PRAIRIE CREEK ZINC-LEAD-SILVER DEPOSIT, NWT
Results include the identification of previously unknown minor phases, including cinnabar (HgS), acanthite (Ag2S), bindheimite (Pb2Sb2O6(O,OH)), and multiple metal arsenate minerals. Anglesite (PbSO4) may also be present in greater proportions than is suggested by previous work. Smithsonite consistently contains elevated concentrations of Pb, Cd, Cu, Fe, and Mn, while cerussite (expected to be removed as Pb concentrate) regularly hosts Zn, Cu and Cd. Variable concentrations of Fe, As, Sb, Hg, Ag, and Se are present in both, in approximately decreasing order. A significant proportion of the trace metals may also be attenuated by other secondary minerals. Processing into tailings will remove significant sources for these elements; however, smithsonite will subsequently remain as the major source for most of them. Significant Hg and Ag could remain in tailings from cinnabar and acanthite that is trapped within smithsonite grains.
In a mine waste setting, near-neutral pH will encourage precipitation and attenuation of trace metals. Regardless, oxidation, dissolution and mobilization is expected to continue at a slow rate, which may be slowed by saturated conditions, or accelerated by localized flow paths and acidification of isolated, sulphide-rich pore spaces.