Summary:
Cripple Creek & Victor is an epithermal alkalic deposit.
The Cripple Creek and Victor Gold Mine lies within an alkaline diatreme, or a volcanic pipe formed by an a gas explosion, that measures approximately 18 square kilometers, or 7 square miles (Thompson et al., 1985, Kelly et al., 1998, and Leichliter and Larson, 2011). The basement units are granodiorite, gneisss, monzonite, and granite. Inside the diatreme, there are many different lithologies: breccia, phonolites (porphyritic and aphanitic), phonotephrite, tephriphonolite, syenite, and lamprophyres (Thompson, 1992, Jensen, 2003, Jensen and Barton, 2007, and Leichliter and Larson, 2011). The main rock type in the diatreme is the breccia, which is composed of pieces of both the basement and intrusive rocks.
The upper portion of the ore body is oxidized (jarosite, goethite, hematite, limonite, and other iron and manganese oxides) (Leichliter and Larson, 2011). As mining progresses downward, the ore body becomes less oxidized and more sulfidic. Pyrite is the most common sulfide, but molybdenite, chalcopyrite, chalcocite, sphalerite, and galena are present (Leichliter and Larson, 2011).
The gold mineralization occurs in every rock type and is mostly controlled by structure. It can occur as native gold, electrum, gold tellurides, gold-silver tellurides, and with sulfides (Leichliter and Larson, 2011). Silver is also present, but to a lesser degree than gold. There are also many different types of tellurides in the district, beside the gold and silver (Leichliter and Larson, 2011).
The gold mineralization is related to potassic alteration (potassic feldspar (adularia), pyrite (sulfide) and quartz). There are minor amounts of argillic alteration (sericite, illite, kaolinite, smectite, and montmorillonite). Gold is mainly located in the veins (1- 10 cm wide) or in the potassic alteration halo of those veins. The veins usually contain quartz, sulfides, and/or tellurides and fluorite. When altered, these veins contain gold, oxides, and clay. The small, fine-grained gold is widespread with the sulfides (Leichliter and Larson, 2011).