GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 73 . The NRS site is located west of the Golden Valley fault (and a smaller conjugate fault), through which the Ruahorehore Rhyolite has intruded to the surface. The proposed rock stack is located within an alluvial gully, which is underlain predominantly by Black Hill Dacite (unit iu). Dacite outcrops across the site, present up to 300 m in thickness (to 800 mRL), with the Ruahorehore rhyolite (mnr) overlying the dacite along its eastern edge. Where present, ignimbrite overlies the dacite unit and has a thickness of up to 30 m in the west of the existing northern storage area (EGL bore WG5). The regional andesite rock (aw) underlies the site at depth and has been confirmed from sterilisation drilling to have no mineralisation at this location. The shallow geology is summarised as follows: – A discontinuous ignimbrite flow is located in a paleo-channel that runs north to south across the site, roughly aligned with an existing tributary flowing north to the Ohinemuri River (Tributary TB1, located between surface water monitoring locations TB1a and TB1f on Figure 4.1). The ignimbrite is occasionally underlain by clastsupported boulder and cobble alluvium, which is likely to be related to the erosional surface of the dacite. – A paleo-channel in the southern section of the site appears to be aligned with the location of the tributary prior to construction of the existing northern storage site (EGL bore MW5S/D), with the historical channel location inferred from original site topography (EGL, 2019a Figure 3). – Ohinemuri River alluvium (organic clay to fine/medium gravels) overlie the ignimbrite and dacite across the majority of the NRS site. A discontinuous volcanic ash layer overlies the uppermost units. Figure 4.3 NRS geological cross-section (B-B’ of Figure 2.4) (OGNZL, 2017)
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