Unnamed (Billings Glacier)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Mo
Other commodities Cu; W
Ore minerals chalcopyrite; molybdenite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale D-5
Latitude 60.848
Longitude -148.5817
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is consists of two sites near the terminus of Billings Glacier, about a mile and a half north of Passage Canal. They are in the N1/2 sections 28 and 29, T. 9 N., R. 5 E., of the Seward Meridian. One is on the east side of Billings Glacier between 400 and 1,150 feet elevation; the other is along the west side of the glacier between 600 and 750 feet elevation. Due to the steep terrain and glacial ice, the sites are fairly inaccessible. This is location S-169 of Jansons and others (1984). This location is accurate to within half a mile.

Geologic setting

Geologic description

The country rock in the area of this occurrence is Valdez Group sedimentary strata of Late Cretaceous age that has been thermally silicified at and near the contact with a biotite quartz monzonite stock of probable mid-Tertiary age (Hoekzema and Sherman, 1983; Nelson and others, 1985). The stock is locally exposed over an area measuring roughly 2,000 by 2,500 feet but much of the area is covered by ice. Its age has not been determined, but it probably correlates with the nearby Passage Canal pluton, which has been dated at 36.6 +/- 1 million years (Hoekzema and Sherman, 1983). Some of the metamorphosed strata are stretched, boudinaged, and brecciated.
Alteration in the stocks associated with the mineralization consists of an increased quartz content, sericitization of potassic feldspar, destruction of biotite, and a lighter color and coarser texture (Hoekzema and Sherman, 1983). Sulfide minerals found to date are restricted to the southern side of the stock within 300 feet of the contact and between 400 and 1,500 feet elevation.
Pyrite, molybdenite, and chalcopyrite are the most abundant sulfides. Molybdenite occurs as disseminated masses as much as 1 inch across in stockwork veins, as disseminated grains within the stock, and as a fracture coating on joints near the contact. Pyrite and chalcopyrite mostly form veinlets and disseminated grains in the quartz monzonite (Hoekzema and Sherman, 1983).
The U.S. Bureau of Mines discovered this occurrence in 1981; they collected 28 chip and grab samples (Hoekzema and Sherman, 1983). Molybdenite values ranged from less than 2 ppm to 2,000 ppm; the highest values were in visibly altered granite (2,000 ppm) and in otherwise undescribed granite (1,450 ppm). Copper values ranged from 0 to 150 ppm; the highest values were in quartz veins in granite. Other anomalous metal values included 8,600 ppm arsenic in a pegmatite dike and 1,416 ppm tungsten in granite (Hoekzema and Sherman, 1983).
Geologic map unit (-148.583815171853, 60.8474122538012)
Mineral deposit model Porphyry Mo (Cox and Singer, 1986; model 21b)
Mineral deposit model number 21b
Age of mineralization Probably mid-Tertiary, based on presumed correlation with a nearby isotopically dated (36.6+/- million years) pluton.
Alteration of deposit Alteration of the host rock results in a lighter hue, due to increased quartz content, seriticization of potassic feldspar, destruction of biotite, and generally coarser texture (Hoekzema and Sherman, 1983).

Production and reserves

Workings or exploration No workings are present. The U.S. Bureau of Mines discovered this deposit in 1981 and collected 28 samples (Hoekzema and Sherman, 1983). Molybdenite values ranged from less than 2 ppm to 2,000 ppm; the highest values were in visibly altered granite (2,000 ppm) and otherwise undescribed granite (1,450 ppm). Copper values ranged from 0 to 150 ppm; the highest values were in quartz veins in granite. Other anomalous metal values included 8,600 ppm arsenic in a pegmatite dike and 1,416 ppm tungsten in granite.
Indication of production None
Reserve estimates The U.S. Bureau of Mines estimated a resource of 37,500,000 tons of ore containing less than 0.1percent molybdenum (Hoekzema and Sherman, 1983).

References

References

Hoekzema, R.P., and Sherman, G.E., 1983, Mineral investigations in the Chugach National Forest, Alaska (Peninsula study area): U.S. Bureau of Mines in-house report; held at U.S. Bureau of Land Management Alaska State Office, Anchorage, 524 p.
Reporters Jeff A. Huber (Anchorage)
Last report date 1/12/2000