Clifton

Site Name

Primary: Clifton

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Commodity

Primary: Molybdenum

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Location

State: Alaska
District: Juneau (Skagway subdistrict)

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Not available

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: None is specifically referenced in the geologic descriptions in Smith (1942) but Herbert and Race (1965) suggest bleaching and possibly, silicification.

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Rocks

Role: Host
Age Type: Associated Rock
Age in Years: 48.800000+-1.000000
Dating Method: U-Pb (zircon)
Material Analyzed: Zircon
Age Young: Middle Eocene
Age Old: Early Eocene

Role: Host
Age Type: Associated Rock
Age in Years: 48.000000+-2.000000
Dating Method: U-Pb (zircon)
Material Analyzed: Zircon
Age Young: Middle Eocene
Age Old: Early Eocene

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Analytical Data

Not available

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Materials

Ore: Molybdenite
Gangue: Quartz

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Comments

Comment (Workings): Workings / Exploration = Brooks (1918) reported a 10-foot shaft and a 25-foot adit in 1916. In 1917, the prospect was examined by J.B. Mertie, Jr. who reported a 15-foot deep shaft on east side of railroad track about 1,000 north of Clifton. About 80 feet south of the shaft on the west side of the track, an approximately 30-foot tunnel was driven S55E along a prominent joint plane (Smith, 1942). Herbert and Race (1965) also refer to the shaft and short tunnel. They note that although scattered grains of molybdenum can be found over a large area on the well-exposed slopes in the vicinity of Clifton, there is no evidence of other underground workings or surface trenching.

Comment (Deposit): Model Name = Disseminated molybdenite in granitic rocks, possibly related to a fracture zone.

Comment (Geology): Age = U-Pb zircon age dates for the Clifton pluton of 48.8 +/- 1.0 m.y. (Gehrels and others, 1991) and 48 +/- 2 m.y. (Barker and others, 1986) establish a likely age for the Clifton prospect.

Comment (Geology): Age = Chron age is for the Clifton pluton.

Comment (Exploration): Status = Inactive

Comment (Geology): Geologic Description = According to Herbert and Race (1965), sparse molybdenite occurs in an aplite dike at a shallow shaft northeast of Clifton. The aplite dike occurs within a quartz monzonite that contains strong horizontal sheeting, vertical joints, and generally horizontal silicified bands with very sparse molybdenite. The molybdenum mineralization may be associated with a N60E fracture zone. Five stream sediment samples collected over an interval of approximately 4,000 feet along the railway to the southwest of Clifton contained 13 to 120 ppm molybdenum. Smith (1942) summarizes the description of J.B. Mertie, Jr. who visited the site in 1917. According to Mertie, the molybdenite appears to occur in a rock that varies from alaskite to granite and contains no mafic minerals. The molybdenite is distributed in patches throughout the granitic rock and was estimated to constitute about 1% of the rock. The granite was described as being extensively sheeted horizontally and cut by prominent joint planes that strike N50W and dip 72 degrees to the southwest.? the Clifton prospect occurs within the Clifton granite of Gilbert and others (1990) who note the presence of widespread molybdenite mineralization in the granite and attribute it to the high level of emplacement and rapid cooling of the granite. Clough (1991 [BOM, v. 2, sec C]) observed that the Clifton granite contains miarolitic cavities and that it is the youngest granite in the region. U-Pb zircon age dates for the Clifton granite of 48.8 +/- 1.0 m.y. (Gehrels and others, 1991) and 48 +/- 2 m.y. (Barker and others, 1986) establish a likely age for the Clifton prospect.

Comment (Reference): Primary Reference = Smith, 1942

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References

Reference (Deposit): Herbert, C.F., and Race, W.H., 1965, Geochemical investigations of selected areas in southeastern Alaska, 1964 and 1965: Alaska Division of Mines and Minerals Geochemical Report 6, 75 p., 4 sheets, scale 1:63,360.

Reference (Deposit): Herbert, C.F., and Race, W.H., 1964, Geochemical investigations of selected areas in southeastern Alaska, 1964: Alaska Division of Mines and Minerals Geochemical Report 1, 75 p.

Reference (Deposit): Barker, Fred, 1952, The coast range batholith between Haines, Alaska and Bennett Lake, British Columbia: Alaska Territorial Department of Mines Miscellaneous Report 109-3, 48 p., 2 sheets, scale 1:126,720.

Reference (Deposit): Barker, Fred, Arth, J.G., and Stern, T.W., 1986, Evolution of the Coast batholith along the Skagway traverse, Alaska and British Columbia: American Mineralogist, v. 71, p. 632-643.

Reference (Deposit): Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska: U.S. Geological Survey Open-file Report 84-572, 298 p., 1 plate, scale approx. 1:600,000.

Reference (Deposit): Gehrels, G.E., McClelland, W.C., Samson, S.D., Patchett, P.J., and Jackson, J.L., 1990, Ancient continental margin assemblage in the northern Coast Mountains, southeast Alaska and northwest Canada: Geology, v. 18, p. 208-211.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Skagway quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-424, 1 sheet, scale 1:250,000.

Reference (Deposit): Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mt. Fairweather and Skagway quadrangles, Alaska: U.S. Geological Survey Open-File Report 78-316, 123 p.

Reference (Deposit): Berg, H.C., and Cobb, E.H., 1967, Metalliferous Lode Deposits of Alaska. U.S. Geological Survey Bulletin 1246, 254 p.

Reference (Deposit): Clough, A.H., 1991?, Bureau of Mines mineral investigations in the Juneau mining district, Alaska, 1984-1988, v. 2, Detailed mine, prospect, and mineral occurrence descriptions, section E, Coast Range subarea: U.S. Bureau of Mines of Mines Special Publication, 44 p.

Reference (Deposit): Gehrels, G.E., McClelland, W.C., Samson, S.D., Patchett, P.J., and Brew. D.A., 1991, U-Pb geochronology and tectonic significance of Late Cretaceous-early Tertiary plutons in the northern Coast Mountains batholith: Canadian Journal of Earth Sciences, v. 28, p. 899-911.

Reference (Deposit): Smith, P.S., 1942, Occurrences of molybdenum in Alaska: U.S. Geological Survey Bulletin 926-C, p. 161-210.

Reference (Deposit): Brew, D.A., and Ford, A.B., 1994, The coast mountains plutonic-metamorphic complex and related rocks between Haines, Alaska, and Fraser, British Columbia q tectonic and geologic sketches and Klondike Highway road log: U.S. Geological Survey Open-File Report 94-268, 25 p.

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