Abstract
The ability to accurately quantify the effective neutralization potential (NP) of tailings is critical for designing mine waste management systems. However, there is a lack of literature on the effective NP of samples containing naturally occurring barium carbonates. In this study, fifteen samples from the Macmillan Pass zinc-lead-silver deposits and the Mactung tungsten skarn deposit were analysed using chemical and mineralogical acid-base accounting methods. Chemical methods included the modified Sobek and Net-Acid Generation (NAG) tests. Mineralogical methods included the use of automated mineralogy by scanning electron microscope (SEM) and electron microprobe (EMP) analysis. The Macmillan Pass samples contained average carbonate concentrations of 16 wt.% siderite (FeCO3) and 1.3 wt.% cerussite (PbCO3), neither of which contribute to NP, and 1.1 wt.% barytocalcite (BaCa(CO3)2), 1 wt.% witherite (BaCO3) and less than 0.5 wt.% ankerite (Ca(Mg0.7Fe0.3)(CO3)2), calcite (CaCO3), and norsethite (BaMg(CO3)2). Calcite was the sole contributor to NP in the Mactung samples with an average concentration of 6.5 wt.%. The average modified Sobek NP was 18 and 64 kg CaCO3 eq t-1 for Macmillan Pass and Mactung, respectively. The average mineralogical NP was 16 and 65 kg CaCO3 eq t-1 for Macmillan Pass and Mactung, respectively. Barytocalcite and witherite provided averages of 7.5 and 4.8 kg CaCO3 eq t-1 of neutralization capacity, respectively, for Macmillan Pass. The mineralogical NP was also compared to the NAG capacity in units of kg H2SO4 t-1. The comparison of chemical and mineralogical NP showed that barium carbonates do contribute to NP in Macmillan Pass samples.