GHD | Oceana Gold (New Zealand) Limited | 12537997 | Gladstone Pit TSF 8 – Andesite Host Rock primarily consists of fine to medium porphyritic andesite flows with varying degrees of clay alteration and silification. Also included within this category are volcanic ash and tephra deposits stratified within the main body of the andesite host rock. This host rock is prevalent throughout the wider area. The andesite rock is of medium rock strength (typically R2 to R3), although the strength is variable ranging from R1 to R4. Fractured and brecciated zones are common throughout the unit, with defects commonly clay infilled. The presence of clay tends to decrease with depth which results in increased Rock Quality Designation (RQD). – Quartz Andesite which is the dominant host lithology for the Martha Vein system and in the Union Hill epithermal vein system. Generally described as a quartz-feldspar phyric andesite lava. – Hydrothermal Vent Breccia is found at shallow levels (above RL 1000 m) in funnel shaped vents comprising of clay to quartz altered breccias. The unit is blueish grey, brown and light grey/white. It is generally gravelly, clayey and silty with angular to subrounded clasts up to 70 mm. The strength of the unit varies between a stiff soil and very low rock strength (R1) with variable RQD. Young volcanics, ignimbrite, dacite, volcanic ash, and alluvial sediments overlie the andesite (the basement rock). The geology and mineralogy of the GOP is expected to be generally consistent with that encountered in the existing Martha, Favona, Trio, and Correnso mines. However, the geology in the vicinity of GOP is notable for the weathered breccia and deposition of young volcanics (dacite), particularly on the eastern and southern sides of Gladstone Hill. Figure 2 shows the geological makeup of the final pit walls. Figure 2 Geological setting of the GOP (PSM 2021)
RkJQdWJsaXNoZXIy MjE2NDg3