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and Koschmann (1935) described the sedimentary rocks in the Cameron and School Section <br />Mines and, in 1939, Koschmann collected samples from calcareous shales /siltstones and marls <br />(limey sediments) in the area. Recent drilling has confirmed that the calcareous sediments cover <br />much of the footprint of the ECOSA, with thicknesses that range from 5 to 25 feet. <br />Underlying the Tertiary volcanics in the ECOSA area are Precambrian granite, schist, and gneiss. <br />These rocks form a relatively impermeable containment for the diatremal rocks. The upper <br />surface of the Precambrian rocks slopes to the southwest under the ECOSA at approximately 8 °, <br />directing subsurface flow of infiltrating precipitation towards the main diatreme, that eventually <br />reached the regional ground water system as interested by the Carlton Tunnel. <br />Mineralization in the northwest portion of the District falls into the North Cresson Mine area and <br />includes Globe Hill, Schist Island, and the SGOSA. The geology is dominated by a large, <br />northwest - trending, elongate, Precambrian ridge of schist that is surrounded by diatremal <br />breccia. Both the schist and breccia are oxidized on the surface and display moderate to strong <br />potassic alteration and weak argillic alteration. This area has been intruded by scattered and <br />discontinuous lamprophyre and phonolitic dikes as well as a small plug of porphyritic phonolite. <br />The dominant structural trends in this area display a north - northwest and northeast- trending <br />fabric. <br />The Globe Hill area is underlain by breccia and phonolitic country rock that was intruded by <br />late -stage hydrothermal breccia pipes. These breccia pipes hosted most of the gold <br />mineralization in the area and are characterized by strong argillic alteration as well as the <br />presence of sulfate (gypsum and anhydrite), carbonate (calcite and rhodochrosite), and quartz <br />veining. The breccia pipe bodies are generally less than 500 feet in diameter and occur at the <br />intersection of northeast- and north- northwest- trending structural zones. <br />Based on the field mapping conducted during construction of the existing AGVLF, three rock <br />types compose the bedrock geology beneath the Phase I -IV AGVLF (Asch and Harris, 1994). <br />The diatreme /granodiorite contact occurs beneath the Phase 5 AGVLF. <br />The predominant unit in the footprint of the existing Phase I -IV of the AGVLF area is <br />undifferentiated Precambrian (Proterozoic) granodiorite. This unit is primarily a pinkish gray, <br />medium to coarse grained, biotite -rich granodiorite. Locally, this basement rock is a biotite <br />schist, or augen gneiss. The granodiorite is often cut by feldspar pegmatites or aplite dikes. In <br />the southern part of the AGVLF Phase I -IV, several Precambrian diabase dikes and sills were <br />exposed. <br />Cripple Creek & Victor Gold Mining Company <br />Cresson Project Mine Life Extension 2 <br />4 -4 <br />