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Montana Saddle

Prospect in Alaska, United States with commodities Gold, Arsenic, Mercury, Antimony
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Geologic information

Identification information

Deposit ID 10307771
Record type Site
Current site name Montana Saddle

Geographic coordinates

Geographic coordinates: -155.96501, 63.55646 (WGS84)
Relative position 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.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Arsenic Secondary
Mercury Secondary
Antimony Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Feldspar Gangue
Quartz Gangue

Alteration

  • (Local) Ankerite alteration near quartz-sulide vein swarms.

Mineral occurrence model information

Model code 78
USGS model code 20c
Deposit model name Porphyry Cu-Au
Mark3 model number 34

Nearby scientific data

(1) -155.96501, 63.55646
ListMap

Comments on the geologic information

  • 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.
  • Age = A Late Cretaceous age is inferred based on a 71.0 Ma age for the adjacent Cripple Creek Mountains pluton (Bundtzen and others, 1997).

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Active

Mining district

District name Innoko

Comments on the workings information

  • Workings / 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.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF MD018

Bibliographic references

  • Deposit

    Patton, W.W., Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811-A, 1 sheet, scale l:250,000.

  • Deposit

    Bundtzen, T.K., Pinney, D.S., and Laird, G.M., 1997, Preliminary geologic map and descriptive data tables from the Ophir C-1 and western Medfra C-6 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File Report 97-46, 10 p., 1 sheet, scale 1:63,360.

Comments on the references

  • Primary Reference = Bundtzen and others, 1997

General comments

Subject category Comment text
Deposit Model Name = Porphyry Cu-Au (Cox and Singer, 1986; model no. 20c)
Deposit Other Comments = See Wyoming Lode (MD016), Neirod East (MD020), and Moose Jaw (MD019) prospects.

Reporter information

Type Date Name Affiliation Comment
Reporter 03-JUN-98 Bundtzen, T.K. Pacific Rim Geological Consulting