Prospect, Inactive

Commodities and mineralogy

Main commodities Mo
Ore minerals molybdenite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale C-1
Latitude 59.53
Longitude -135.22
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is marked by a shallow shaft about 1,000 feet northeast of Clifton. It is just east of the White Pass and Yukon Railroad track at an elevation of about 900 feet in the SW 1/4, section 16, T. 27 S., R. 60 E. of the Copper River Meridian. Clifton is an old station on the White Pass and Yukon Railroad that is essentially coincident with Bench Mark 855 ('BM 855'). Smith (1942) refers to the location of a 30-foot tunnel about 80 feet south of the shaft on the west side of the railroad track. Herbert and Race (1965), however, mention a short tunnel on the west side of the railroad track west of their map location 2 , which is plotted about 2,500 feet southwest of Clifton. This prospect is location 21 of Cobb (1972 [MF 424]).

Geologic setting

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 N 60 E 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 percent of the rock. The granite was described as being extensively sheeted horizontally and cut by prominent joint planes that strike N 50 W 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.
Geologic map unit (-135.221831683028, 59.529673082264)
Mineral deposit model Disseminated molybdenite in granitic rocks, possibly related to a fracture zone.
Age of mineralization 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.
Alteration of deposit None is specifically referenced in the geologic descriptions in Smith (1942) but Herbert and Race (1965) suggest bleaching and possibly, silicification.

Production and reserves

Workings or 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.
Indication of production None


MRDS Number A013111


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.
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.
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, no. 3, p. 208-211.
Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001