2008-04-15_REVISION - M1980244 (309)

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Based on the field mapping conducted during construction of the existing VLF, three rock types compose the bedrock geology of the existing VLF (Asch and Harris, 1994). The diatreme/granodiorite contact occurs beneath the AGOSA The predominant unit in the footprint of the existing VLF area is undifferentiated Precambrian (Proterozoic) granodiorite. This unit is primarily a pinkish gray, medium to coarse grained biotite-rich granodiorite. Locally, this basement rock is a biotite schist, or augen gneiss. The granodiorite is often cut by feldspar pegmatites or aplite dikes. In the southern part of the existing VLF, several Precambrian diabase dikes and sills were exposed. The second rock type in the existing VLF area is Tertiary aphanitic phonolite, most frequently occurring as narrow, often discontinuous dikes intruding the granodiorite in a northeasterly direction. Phonolite dikes generally are blue-gray in color (depending on degree of alteration) and porphyritic (with low percentages of K-feldspar phenocrysts set in an aphanitic groundmass) and may range from massive to fissile in character. Dikes typically range in width from 0.5 feet to 10 feet. Phonolite also occurs as an intrusive • plug that forms Beacon Hill. At the surface, the plug measures approximately 2,000 feet long in a north-northeasterly direction and 1,200 feet wide. It is interpreted to taper considerably downward below the 8,400 foot elevation and is much the same as the dikes described above in terms of composition and texture. The third rock type in the existing VLF area is the lapilli breccia. Based on the geotechnical investigations performed on the breccia occurring on Beacon Hill, it is weathered to an average of about three feet below the ground surface. More specifically, the slopes of Arequa Gulch are covered with a thin layer of colluvium and soil. Bedrock outcrops at the surface have been noted but are not dominant. No notable alluvial deposits are present within the footprint of Phase 5. Mapping in the Arequa Gulch area for the existing VLF indicated the existence of four important structural orientations. The strongest trend is about N20E and is in the central portion of Arequa Gulch. These linear features are small faults or shears consisting of narrow clay gouge seams (0.1 to 1.0 feet in width), surrounded by five- to eight-foot wide envelopes of highly fractured, oxidized, and weakly clay-altered granodiorite. A less strong lineation trends N70E primarily along the northern portion of the Arequa Gulch • site. These lineations are schistose shear zones and range up to five feet in width. The Cripple Creek & Victor Gold Mining Company Cresson Project Mine Life Extension 4-5