Oceana Gold Waihi North Project Waihi North Project Geochemical Assessment – Geochemistry of Tailings and Overburden, Treatment and Mitigation Revision 9 – 17-Jun-2022 Prepared for – Oceana Gold (New Zealand) Limited – Co No.: 2274246 A-5 AECOM The 4-acid digestion method allows a more complete digestion of the rock sample, liberating a greater proportion of elements from minerals more resistant to digestion. For selected core intervals, samples were analysed using both the 2-acid (Nitric Acid and Hydrochloric Acid) and the 4-acid (Nitric Acid, Perchloric Acid, Hydrofluoric Acid and Hydrochloric Acid) digestion method. This allowed for a direct comparison of results between methods. A comprehensive set of samples were analysed using the 2-acid digestion method. A subset of 157 samples were analysed utilising the 4-acid digestion method. Distributions of the corresponding 2-acid data and 4-acid data were compared using the Wilcoxon Mann-Whitney (WMW) test and the results are summarised in Table 30. Results for a number of elements analysed following 2-acid digestion were found to be statistically different than their 4-acid counterpart. Bivariate linear regression plots were produced for these elements to determine the relationship (if any) between 2-acid and 4-acid test data. Where a strong linear relationship (R2 value >0.9) could be demonstrated between variables, a correction factor was applied to the 2-acid data (elements included manganese, molybdenum, lead and selenium). Where a weak relationship was observed (aluminium, magnesium, potassium, antimony, barium, chromium and vanadium), 4-acid data was used. Due to the limited sample size of the 4-acid data for each element (nmax = 157), data are presented together (i.e. data is not split across geology or rock/ore). Figure 17 Sample Locations within Gladstone Open Pit
RkJQdWJsaXNoZXIy MjE2NDg3