2008-04-15_REVISION - M1980244 (325)

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8 Site description 2.3 Geological summary The District lies near the southern end of the Colorado Front Range, on the southwestern flank, of Pikes Peak. Much of the country rock in the District is Precambrian gneiss that was subsequently intruded by Pikes Peak Granite during emplacement of the Pikes Peak batholith. Approximately 32 million years ago, in the Tertiary Period, volcanic activity resulted in emplacement of a complex alkaline diatreme, which was subsequently intruded by successive sequences of fluids and molten rock to form plugs, flow domes, small stocks, and late-stage diatrema pipes and alkaline igneous dikes. Most of the gold deposits in the District occurred in the mass of volcanic rocks, though minor mineralization also occurs in the surrounding granitic rocks. The volcanic rocks, primarily phonolites and volcanic breccias, occupy the diatreme which has the general aspect of asteep-walled crater. The site-wide geology, specifically with regard to the diatreme .complex, has been thoroughly studied and is described in separate reports (Adrian Brown Consultants, 1998 and Adrian Brown, 2008). The main project area is underlain predominantly by the main body of the volcanic diatreme. The Grassy Valley drainage is underlain by the Grassy Valley feeder of the diatreme, and Precambrian granite and granodiorite (granites). Site data suggest that this portion of diatreme is distinct from the main body of the diatreme, as discussed in detail in the Cresson Project Hydrogeochemical Evaluation report (Adrian Brown, 2008). As described in more detail in Section 4.0, hydrogeologic data from wells in the Grassy Valley feeder of the diatreme indicate that this area appears to be less transmissive than the main diatreme, possibly due to the influence of the underlying and intervening granites and compartmentalization within the diatreme. • 2736 Cripple Creek & Victor Gold Mining Company Water Management Consultants