Studies of mineralized intrusive complexes in north-central Montana

Alkalic-type epithermal gold deposit model

“…The Kendall deposit in Montana is dominantly hosted in carbonate rocks adjacent to syenite. The gold mineralized zone at Kendall is characterized by a geochemical association (As, Hg, Sb) that suggests similarities between Kendall and Carlin-type deposits in Nevada (Lindsey, 1985). However, the presence of abundant disseminated fluorite and high concentrations of vanadium in the gold ore zones are characteristics of alkalic-type epithermal gold deposits.…”

“…These breccias were then intruded by alkaline igneous rocks, and the associated ores may be fine grained and disseminated or form coarse-grained accumulations within vugs and pockets (Lindgren and Ransome, 1906;others, 1996, 1997;Jensen and Barton, 2000). Carbonate or carbonaceous sedimentary rocks are the dominant host rocks at the Kendall deposit (Lindsey, 1985), and in some cases (for example, Porgera), both igneous and sedimentary rocks host mineralization.…”

“…A number of other deposit types are either spatially, temporally, or genetically related to alkalic-type epithermal gold deposits. The most common types of associated deposits include (1) copper, iron, gold, and zinc-rich skarns, such as those in New Mexico (McLemore, 1996), deposits near Galore Creek (Enns and others, 1995), and many in Montana (Woodward and Giles, 1993); (2) polymetallic replacement deposits (Ag, Pb, Zn, Cu, Au), the best example of which is the Kendall deposit in Montana (Lindsey, 1985); (3) fluorspar vein and breccia deposits and tungsten-bearing veins, exemplified by deposits in Boulder County (Kelly and Goddard, 1969;Nash and Cunningham, 1973); and (4) local carbonatites (REE, Nb), for example in New Mexico (McLemore, 2010). The presence of these deposits does not necessarily indicate the existence of nearby alkalic-type epithermal deposits, nor does their absence preclude the occurrence of nearby alkalic-type epithermal gold deposits.…”