Tailings dust characterization and impacts on surface water chemistry at an abandoned Zn-Pb-Cu-Au-Ag deposit

Highlights: • Dust from weathered tailings contains primary and secondary metal hosting minerals. • Most minerals of interest are undersaturated in pH-neutral simulated surface waters. • Sphalerite, chalcopyrite and cerussite are likely the main sources of Zn, Cu and Pb. The increased potential for dust mobilization as a result of climate change indicates a need to better understand interactions between dust and water. This research investigates the geochemical effects of tailings dust on surface waters near Stirling mine, Nova Scotia. Tailings were sieved to 3), chalcopyrite (CuFeS₂), Pb–Mn phases (possibly cesàrolite (PbMn₃O₆(OH)₂)), smithsonite (ZnCO₃), goethite (FeO(OH), aurichalcite ((Zn,Cu)₅(CO₃)₂(OH)₆), hydrohetaerolite (ZnMn₂O₄·H₂O), tennantite (Cu₆(Cu₄Zn₂)As₄S₁₂S), and galena (PbS). Shake flask tests were conducted in simulated stream waters (pH = 7) using sieved tailings and passive dry deposition collector filters to investigate the solubility of metal-hosting mineral phases within dust. Results indicate metal leaching at near neutral pH conditions. Sphalerite, cerussite and chalcopyrite are likely the main sources of Zn, Pb, and Cu in the shake flask leachate, based on calculated saturated indices and mass balance. Analyses of stream waters indicate similar conditions (pH, ORP, saturation indices, etc.) compared to the results of the shake flask tests, suggesting they provide reasonable insight about processes occurring in the field. Tailings dust generated at the site is therefore a potential source of metals to surface waters.