Montana Saddle

Prospect, Active

Commodities and mineralogy

Main commodities Au
Other commodities As; Hg; Sb
Ore minerals arsenopyrite; trace chalcopyrite
Gangue minerals feldspar; quartz

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale C-6
Latitude 63.557
Longitude -155.962
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Montana Saddle prospect is located in a broad saddle separating the Montana Creek and Colorado Creek drainage basins in the northern part of the Cripple Creek Mountains at an elevation of 1,900 feet (579 m) in Section 27, T. 22 S., R. 15 E., of the Kateel River Meridian. Location is precisely known; the reporter visited the prospect in 1996.

Geologic setting

Geologic description

The Montana Saddle prospect consists of an en echelon series of cox-comb quartz-arsenopyrite-chalcopyrite and quartz-feldspar veinlets ranging from 1 to 5 inches (2.5 to 13 cm) thick in a hornblende granite phase of the Cripple Creek Mountains stock. The vein spacing, which varies from 6 inches to 3 feet (15 cm to 0.9 m), trends in a consistent north 60 degrees east for a traceable strike distance of at least 450 feet (137 m) and for a width of at least 275 feet (84 m), before disappearing under tundra in all directions.
The Montana Saddle prospect is aligned along a north 40 degrees east trending fault mapped by Bundtzen and others (1997), which apparently controls the distribution of other metallic prospects, including the Wyoming (MD016), Neirod-East (MD020), and Moose Jaw (MD019) lodes. The coarse grained, hypidiomorphic, hornblende granite contains about 10 percent olive green hornblende, and contrasts with the biotite pyroxene monzonite phase, which is more typical of the Cripple Creek Mountains stock. Age of mineralization is inferred to be Late Cretaceous based on a 71.0 Ma age for the adjacent Cripple Creek Mountains pluton (Bundtzen and others, 1997).
Five chip-channel samples that aggregate about 45 feet (14 m) of vein width yielded an average assay of 465 ppb gold, 968 ppm arsenic, and 1,995 ppb mercury (Bundtzen and others, 1997). One sample contained 590 ppm antimony; however, the remaining samples contained only trace amounts of antimony.
Geologic map unit (-155.964375217461, 63.5563898400639)
Mineral deposit model Porphyry Cu-Au (Cox and Singer, 1986; model 20c).
Mineral deposit model number 20c
Age of mineralization A Late Cretaceous age is inferred based on a 71.0 Ma age for the adjacent Cripple Creek Mountains pluton (Bundtzen and others, 1997).
Alteration of deposit Ankerite alteration near quartz-sulide vein swarms.

Production and reserves

Workings or exploration The prospect area has been cut by four trenches of two distinct ages. One trench system is nearly completely overgrown with vegetation, whereas good rock exposures are still preserved in the two younger excavations. Five chip-channel samples of that aggregate about 45 feet (14 m) of vein width yielded an average assay of 465 ppb gold, 968 ppm arsenic, and 1,995 ppb mercury (Bundtzen and others, 1997). One sample contained 590 ppm antimony; however, the remaining samples contained only trace amounts. Placer Dome U.S., Inc. and Novagold Inc. sampled and trenched the prospect in 1997 and 1998 respectively.
Indication of production None
Reserve estimates None.

Additional comments

See Wyoming Lode (MD016), Neirod East (MD020), and Moose Jaw (MD019) prospects.

References