Oceana Gold Project Quattro Project Quattro Geochemical Assessment – Tailings and Overburden, Treatment and Mitigation \\na.aecomnet.com\lfs\APAC\Christchurch-NZCHC1\Legacy\Projects\605X\60544823\6. Draft Docs\6.1 Reports\Waihi North\App D - Kinetic and Column Testing\WNP Draft v6_App D (Kinetic Column Testing)_20220504.docx Revision 5 – 07-Aug-2020 Prepared for – Anderson Lloyd – Co No.: 5719274 Appendix D – Overburden Kinetic and Column Testing D1 Introduction Kinetic and column testing of overburden samples has been undertaken to further refine the assessment of potentially acid generating materials, as well as to characterise the influence of reaction rates. At the time of kinetic and column test initiation, available overburden was confined to exploratory and / or resource-delineation cores drilled by OGNZL within the vicinity of the projected Gladstone pits. Overburden was selected with the intention of obtaining samples representative of the overburden material to be excavated from the Gladstone pit. To achieve this, AECOM reviewed the following information provided by OGNZL; lithological drill logs, intercept depths (depth each core entered and exited the future pits’ projected boundaries), models of the projected pits’ geology, and photos of drill cores. Final material selected for the kinetic and column geochemical testing is outlined in the following sections and focusses on overburden both within and in the area adjoining the proposed Gladstone Pit. D2 Kinetic Testing D2.1 Methodology Kinetic testing of six overburden samples (representative of the Gladstone vent breccias) was undertaken to support findings of the static testing. This was to aid in characterising the acid generating potential, investigate trace element leaching, and to assess the potential rates of acidification in the overburden. Kinetic tests were undertaken using the humidity cell method in general accordance with ASTM:D5744-13e1.Standard Test Method for Laboratory Weathering of Solid Materials Using a Humidity Cell. Approximately 1 kg of sample material was required for each humidity cell. This material was selected based on lithology, extent of alteration, static testing results (net acid generating (NAG) and acid base accounting), and total element analyses. Samples were limited to hydrothermal vent breccias representative of the breccia overburden material within the Gladstone Pit (which compromises approximately 17% of the projected overburden material). The breccia material is the focus of the kinetic tests as it has previously not been widely encountered in existing mining operations. Sample selection was based on the selection of hydrothermal breccia material which represented a range of the pits’ potential chemical variability. To achieve this, only hydrothermal breccia intervals with returned Sulphur, NAG, and ANC data at the time of sample selection were considered. Core intervals from each sample conforming to the selection criteria listed below were plotted on a NPR/NAG pH diagram. Samples spanning the range of the PAF classification were selected and are shown in Figure D1. The following additional criteria were used where possible to guide selection of kinetic material: • Core intervals were selected from cores spatially distributed across the projected pits’ volume where possible; • Core intervals with ore-grade concentrations of gold (where existing data was available) and veins or highly silicified zones were excluded; • Core intervals logged as not having an ‘Argillic’ or strong clay alteration were excluded; • Core intervals logged as not having visible Pyrite were excluded; and • Core intervals logged as weathered or, displaying obvious, pervasive oxidation were excluded.
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