SECTION 3 Site Investigations & Results C:\D Data\GWS C Drive\GWS\Client Files\1344 OGL - WKP\4 Deliverables\WKP Final Draft Report\June Report\WAI-985-000-REP-LC-0030. Final_Rev_0.docx 27 The geology of the Wharekirauponga deposit has been well characterised from exploration drilling and resource definition. Based on its structure it is geomorphically similar to the neighbouring Golden Cross deposit having a westward dipping main vein structure (feeder zone) with a stockwork vein system present on the hangingwall. The feeder zone contains significant quartz veining with some calcite replacement together with altered country rock. The stockwork zone also contains substantial quartz veining, but the veining is less well developed than the feeder zone, with a large proportion of the stockwork being altered country rock. The alteration in the country rock is quartz adularia with an argillic and advanced argillic clay alteration halo surrounding this. Over much of the site post mineralisation Rhyolite pyroclastic’s and Andesite overlie the veins and host rock and is commonly observed to be highly weathered. A thick soil Regolith is present on the surface of these geologic units. Shallow, perched groundwater is present in the soil Regolith and this is recharged from rainfall. The Regolith water drains laterally as interflow and discharges into the stream. A permanent water table is present within the post mineralisation volcanics ranging from 7 to 35 m below ground level and a downward hydraulic gradient is observed into the host country rock. The host rock has a clay weathered/altered zone on its paleosurface resulting in attenuated vertical drainage and a higher hydraulic gradient. The host rock has a generally low rockmass permeability whereas the veins are more permeable. Inspection of the core indicates fractures within the host rock are commonly tight or clay infilled and, as such, the country rock is not expected to transmit water freely. For the purpose of this assessment aquifer hydraulic parameters have been adopted from the site investigations to enable a quantitative assessment of effects to be undertaken. Table 7 provides a summary of the values adopted. Table 7 Adopted Aquifer Hydraulic Parameters Geologic Unit Permeability (m/s) Storage Permeability Source Alluvium / Regolith 1x10-6 0.3 to 0.1 Waihi Weathered Andesite 5x10-9 0.3 to 0.1 Waihi observations Andesite Flow 1x10-8 0.05 to 0.001 Waihi observations Weathered Rhyolite 8x10-8 0.3 to 0.1 WKP observations Ignimbrite Pyroclastics 1x10-8 to 1x10-9 0.1 to 0.05 WKP observations Rhyolite Flow (host) 5x10-8 0.05 to 0.01 WKP observations Vein 1x10-5 0.02 WKP observations 3.10 Conceptual Groundwater Model The following preliminary Conceptual Groundwater Model (CGM) has been developed to allow a better understanding of how the groundwater system and surface waters interact in the Wharekirauponga catchment such that effects associated with mine dewatering can be evaluated. The CGM is described below and depicted in Figures 26 and 27. The general conceptual model for the Wharekirauponga site is that of steeply dipping, parallel vein structures that are connected via dilatational vein sets. The veins are considered to also be hydraulically connected via the stockwork and later phase veins. Due to the catchment
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