Rory McNeill Reference No. 20148384_7407-012-LR-RevA_DRAFT OceanaGold Corporation 08 September 2021 3 Based on the feedback above from OceanaGold about the various tunnel alignment options, Golder has evaluated the geological and geotechnical conditions of tunnel alignment Option 2 and Option 4. 3.0 AVAILABLE GEOLOGICAL DATA 3.1 Geological Setting The Coromandel Peninsula, south as far as Te Aroha, and including the area around and north of Waihi, is dominated by volcanic rocks of the Coromandel Group comprising andesite, dacite and rhyolite of Miocene Age2,3 (refer Figure 2). The geological map, Figure 2, shows that Portal and Willows Connection are founded in the Waipupu Formation, which is a phyric andesite and dacite with minor tuff breccia, crystal tuff and lacustrine sediments, extensively hydrothermally altered. The alignment options then pass under valley floor alluvium consisting of pumiceous, rhyolitic and andesite sand, gravel and silts up to the Waihi Fault. The alignment may also encounter the Whiritoa Andesite which is lithologically similar to the Waipupu Formation, but is not extensively hydrothermally altered. Basement rock in the area comprises Jurassic Age Manaia Hill Group Sandstone, siltstone and conglomerate at more than 1000 m depth below the tunnel alignment options. The Coromandel Peninsula is located on the western side of the Taupo Volcanic Zone, which is an extensional tectonic domain dominated by northeast trending normal faults of low activity. Figure 2: Waihi geological map with the proposed tunnel alignments outlined3 aw = Waipupu Formation, ah = Whiritoa Andesite and tm = alluvium, red lines = extensive hydrothermal alteration. 2 Edbrooke SW, 2001, Geology of the Auckland Area, Institute of Geological and Nuclear Sciences 1:2500,000 geological map 3. 1 Map Sheet and 74-page document. 3 Braithwaite RL, Christie AB, 1996: Geology of the Waihi area, scale 1;50,000. IGNS geological map 21. D R A F T
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