Proposed Limpopo West Mine Concept Study ... - SRK Consulting

Calcium+Magnesium to Sulfate RatioSRK Consulting: 447493: Limpopo West Geochem Page 29The leach data have been used to plot pH versus the ratio of Ca+Mg: SO 4 in milli-equivalent/l. Thisratio is plotted to provide an indication as to whether pH is controlled by the dissolution of carbonatesor by acidity generated from the oxidation of sulfides. Generally a ratio above 1 indicates thatcarbonate dissolution is controlling pH, while a ratio below 1 indicates that sulfide oxidation iscontrolling the pH.9.08.07.06.05.04.03.02.01.00.04.0 5.0 6.0 7.0 8.0 9.0 10.0pHGroenfontein Grootwater Geelbekpan Ringbult Welgelegen Linear (Series6)Figure 5-5: Ratio of the sum of Calcium and Magnesium to Sulfate as meq/lFor the material sampled by IGS, which is assumed to be composite of the various materials, it isevident that some of the sampled materials (58%) have the ratio of Ca + Mg to SO 4 above 1, whichindicates that carbonates are controlling the pH and not pyrite oxidation. The rest of the samples(42%) have ratios of less than 1 indicating that sulfide oxidation controls the pH of these sampleswhich might potentially be attributed to the presence of coal associated lithologies. This supports thepaste pH values, however, the ABA findings indicate that a significant portion of the sample haveuncertain acid generating potential.The sum of the metal concentrations were plotted against the deionised leach pH in a Ficklindiagram to assess whether these samples have the potential to mobilise metals at concentrationsthat could impact groundwater and surface water. The Ficklin diagram is presented in Figure 5-6.GOGP/LAKJ Report_April2013_19April2013 (1)_Final_Ludi_22052013 April 2013