Alpha

Mine, Inactive

Commodities and mineralogy

Main commodities Ag
Other commodities Au; Cu; Pb; Sb; Zn
Ore minerals arsenopyrite; boulangerite; chalcopyrite; galena; jamesonite; limonite; pyrite; sphalerite; stibnite; tetrahedrite
Gangue minerals quartz; siderite

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-3
Latitude 63.5229
Longitude -151.0107
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Alpha mine (Cobb, 1980 [OFR 80-363]) is on the south flank of Alpha Ridge above Eldorado Creek. It is about 4000 feet due west of Iron Dome. The mine workings are at an elevation of about 3000 feet and are in the SW1/4SE1/4 sec. 15, T. 16 S., R. 18 W., Fairbanks Meridian. The location is accurate within 500 feet. The mine is location 9 of Bundtzen, Smith, and Tosdal (1976) and Bundtzen (1981), 14 and 15 of Thornsberry, McKee, and Salisbury (1984), D of Hawley and Associates (1978), and 3 of Cobb (1972 [MF 366]) and MacKevett and Holloway (1977).

Geologic setting

Geologic description

The fault-controlled Alpha vein system strikes NE and dips steeply. It cuts tan-weathering quartz-mica schist of Birch Creek type (Bundtzen, 1981). The fault can be traced southwest along strike for about 1000 feet. It appears to continue about 1500 feet east-northeast. The fault may be the continuation of a fault which offsets a calcareous schist unit about 500 feet (Hawley and Associates, 1978, fig. 4.1-A(1)).
The fault zone is as much as 25 feet wide and individual veins are up to 10 or more feet thick. In about 1922, a shallow shaft exposed an eight- or nine-foot-thick zone containing three quartz veins, each about a foot thick. A representative sample of hand-cobbed material assayed 266.3 ounces of silver per ton (Davis, 1923, p. 131). The workings were largely caved when Wells visited the property in 1931; he reported that a foot-thick galena-rich vein assayed 0.01 ounce of gold per ton, 346 ounces of silver per ton and 5.46 percent lead (Wells, 1933, p. 375-376).
The mineralogy is typical of quartz-siderite polymetallic veins in the Kantishna Hills area (MM091). The veins mainly comprise arsenopyrite, pyrite, galena, jamesonite, stibnite, and sphalerite, along with lesser amounts of boulangerite and tetrahedrite, in a siderite-rich quartz gangue. Extensive near-surface limonite appears to be derived from siderite as well as from the sulfide minerals. The veins are probably Eocene, roughly contemporaneous with the eruption of the Teklanika Volcanics in the Mt. McKinley area (Gilbert, Ferrill, and Turner, 1976).
Geologic map unit (-151.012985875132, 63.5223919372373)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization The veins are probably Eocene, about contemporaneous with eruption of the Teklanika volcanics of the Mt. McKinley area (Gilbert, Ferrill, and Turner, 1976), (also see record MM091).
Alteration of deposit Silicification; iron-oxide alteration.

Production and reserves

Workings or exploration
The Alpha mine was developed before 1923 by a 120-foot-long drift adit and a 20-foot shaft (Davis, 1923). About 10 tons of selected, high-grade ore was shipped in 1921; ore was also shipped in 1923. Although the ore was rich, the mine was not profitable, owing to high shipping costs (Brooks, 1925). The mine was inactive when visited by Wells in 1931 (Wells, 1933). Sometime later, a bulldozer trail was cut to the mine and there was some bulldozer trenching. Claims were never patented; in 1983, they were held as the Virginia City 1 and 2 by James Fuksa.
Samples collected in the 1970s and 1980s tend to confirm the high-grade nature of the vein. A sample collected by Bundtzen (1981, table 9) assayed about 83 ounces of silver per ton, about 18 percent lead and nearly 3 percent zinc. Samples collected by McKee (Thornsberry, McKee, and Salisbury, 1984, v. 2, location 14) assayed as much as 48 ounces of silver per ton and 15 percent or more combined lead and zinc. Antimony content locally exceeded 9 percent. Samples collected by Bundtzen contained up to 75 ppm tungsten, and one contained 20 ppm uranium. Soil samples collected as much as 1000 feet southwest of the mine workings were significantly enriched in lead, zinc, and silver (Hawley and Associates, 1978, samples nos. 47-49, table 4.1-1(A)).
Indication of production Yes; small
Production notes Probably a total of about 25 tons, including 10 tons of ore shipped in 1921 that assayed more than 200 ounces of silver per ton.

Additional comments

The Alpha mine is in Denali National Park and Preserve.

References

MRDS Number A011201

References

Bundtzen, T.K., 1981, Geology and mineral deposits of the Kantishna Hills, Mt. McKinley quadrangle, Alaska: M. S. Thesis, University of Alaska, College, Alaska, 238 p.
Reporters C.C. Hawley
Last report date 2/11/2000