Geology and gold deposits of the Cripple creek district,

The relation between Cu/Au ratio and formation depth of porphyry-style Cu–Au ± Mo deposits

“…However, the typical high Sr/Y ratio commonly associated with oreproducing magmas can also be explained by amphiboledominated and plagioclase-suppressed fractionation of normal subduction-zone magmas at high water fugacity in the upper mantle or lower crust (Kay and Mpodozis 2002;Richards 2003), which is favored by a compressional stress state of the converging lithospheric plates (Rohrlach and Loucks 2005;Sillitoe and Perelló 2005). K-rich calcalkaline magmatism does not seem to be essential for the formation of Au-rich porphyry deposits, even though some giant Au-(Te)-rich epithermal deposits are clearly associated with alkalic magmas (e.g., Cripple Creek: Lindgren and Ransome 1906;Porgera: Richards 1992). Among the Aurich porphyry-copper deposits, only 45% are associated with high-K calc-alkaline to shoshonitic suites (Sillitoe 1997), and some, particularly Au-rich porphyry deposits, are associated with distinctly low-K but sodic magmas (e.g., Batu Hijau: Garwin 2002).…”

Direct Associations Between Potassic Igneous Rocks and Gold-Copper Deposits in Volcanic Arcs

“…Low-grade deposits comprise disseminated pyrite with microcrystalline native gold and pervasive adularia alteration (Jensen and Barton 1997;Jensen 2003). Both mineralization styles are spatially associated with alkaline intrusions (Lindgren and Ransome 1906;Kelley and Ludington 2002), and 206 Pb/ 204 Pb compositions of vein galena almost entirely overlap those of phonolites suggesting a direct genetic relationship between alkaline magmatism and gold mineralization (Kelley et al 1998).…”

“…Two different styles of gold mineralization may be distinguished (Kelley et al 1998;Jensen 2003): (1) high-grade Au-Te veins that were the source of most of the historic gold production, and (2) low-grade, disseminated gold deposits that are currently being mined. The high-grade low-sulphidation epithermal Au-Te veins consist of early-stage quartz-K-feldspar-fluorite-pyrite assemblages followed by base-metal sulphides, and late-stage telluride mineralization, locally with roscoelite (Lindgren and Ransome 1906;Loughlin and Koschmann 1935;Thompson et al 1985). Low-grade deposits comprise disseminated pyrite with microcrystalline native gold and pervasive adularia alteration (Jensen and Barton 1997;Jensen 2003).…”

Mineral resource potential of National Forest RARE II and wilderness areas in Colorado

“…The nearest mining district is the Cripple Creek district southwest of the study area. Significant amounts of gold and silver were produced from breccia deposits formed in a subsiding volcanic depression in Precambrian crystalline rocks (Lindgren and Ransome, 1906;. These rocks do not extend into the study area.…”