EGL Ref: 9049 23 June 2022 Page 8 File: WAI-985-000-REP-LC-0050-Rev0.docx This report shall only be read in its entirety. The Black Hill Dacite is present on the east side of Gladstone Open Pit, outcropping as Black Hill. The rhyolite lava flows and tuff associated with the Ruahorehore Rhyolite are too far to the east beneath the tailings storage facilities to be of interest for this study, however, are mentioned as there are rhyolitic lava flows and pyroclastic units also at WUG. The Waipupu Formation andesite rocks (lower quartz andesite and upper andesite on Figure 18) around Waihi are extensively modified in places by weathering and hydrothermal alteration. An almost continuous cap of low permeability, highly weathered and altered material is present on the surface of the andesites around Waihi township. The andesites are overlain by a series of younger volcanic deposits (post mineralisation) which are highly variable in thickness and composition. The younger volcanic deposits consist of rhyolitic tephras and ignimbrites in the form of flows, breccias and tuffs. On the sections (Figure 6 to Figure 17) these are shown as: • Rhyolitic tuffs • Sandy ignimbrites • Welded ignimbrites These younger volcanic deposits are exposed in the east and south walls of Martha Open Pit (Figure 38), however, blanket much of lower areas around Waihi, including Waihi East, Waihi South, lower slopes of Gladstone Hill, and the area over Favona Underground where the Wharekirauponga Access Tunnel decline is proposed. Occasionally, paleosols (buried soils) and sedimentary deposits such as alluvium and boulder alluvium are present at the top of successive eruption sequences. The younger volcanic deposits underlie much of Waihi township to the east and south of the Martha Pit (Figure 5). They also overlie Favona Underground and the west and south of Gladstone Open Pit around the Ohinemuri River, however in a lesser thickness. A layer, up to approximately 8 m thick, of geological young ash soils, alluvium and completely weathered rhyolitic tephras blankets much of the younger volcanic deposits. The younger volcanic deposits have some layers which are more compressible than the underlying andesite which means they have the potential to settle more when subjected to the same increase in stress. There are also some layers of welded ignimbrite which are very stiff which minimise tilt effects at the surface. The combined profile of the younger volcanic beneath Waihi township are up to 140 m deep in the Waihi East area. 3.3. Gladstone Open Pit Gladstone Open Pit is centred over the Gladstone Hill and partially over the adjoining Winner Hill to the south. Gladstone Open Pit will intersect the veins within the andesite which extend to the Ohinemuri River to the south (Ref. 26, 37, and 40). It is possible that the veins do extend beneath the Ohinemuri River towards Heath Road. Surrounding Gladstone Hill are younger volcanic ignimbrite deposits (Ref. 26, 37, and 40). Ignimbrites are present along the reach of the Ohinemuri River passing to the south of Gladstone Hill. In borehole GLD004D they are 16m deep. The andesite is
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