Glacier

Mine, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; native gold; pyrargyrite; pyrite; pyrrhotite; silver; sphalerite; stibnite; tetrahedrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale B-1
Latitude 58.2826
Longitude -134.3099
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Glacier Mine is at an elevation of approximately 1,500 feet on the north side of Sheep Creek. It is 1/4 mile northwest of Portal Camp and 3/4 mile southwest of Sheep Mountain in about the center of the SW1/4 section 28, T. 41 S., R. 68 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Glacier mine was discovered in 1887 and operated intermittently until 1911. The mine has 3,200 feet of workings, 1,200 feet of connecting raises, and 5 adits. The Glacier and the geologically similar, Silver Queen (JU175) mines were connected in 1903 (Spencer, 1906). By 1891, the combined production from the Glacier and Silver Queen mines was 19,300 ounces of silver and 41 ounces of gold. The U.S. Bureau of Mines estimated that the two mines produced nearly $500,000 worth of silver and gold at 1903 prices (Redman and others, 1989). The deposit consists of three, boudinaged, concordant quartz-calcite veins along the contact between black phyllite and green phyllite (Buddington and Chapin, 1929). The veins vary from individual veins up to 12 feet thick to stringers. The veins contain arsenopyrite, chalcopyrite, galena, native gold, native silver, pyrargyrite, pyrite, pyrrhotite, sphalerite, tetrahedrite, and rare stibnite. The veins in the Glacier Mine were mined for as much as 700 feet down dip. U.S. Bureau of Mines samples contained up to 479.9 ppm silver, 2.9 ppm gold, 0.71 percent lead, and 0.11 percent zinc (Redman and others, 1989).
This mine is in the Juneau Gold Belt, which consists of more than 200 gold-quartz-vein deposits that have produced nearly 7 million ounces of gold. These gold-bearing mesothermal quartz vein systems form a zone 160 km long by 5 to 8 km wide along the western margin of the Coast Mountains. The vein systems are in or near shear zones adjacent to west-verging, mid-Cretaceous thrust faults. The veins are hosted by diverse, variably metamorphosed, sedimentary, volcanic, and intrusive rocks. From the Coast Mountains batholith westward, the host rocks include mixed metasedimentary and metavolcanic sequences of Carboniferous and older, Permian and Triassic, and Jurassic-Cretaceous age. The sequences are juxtaposed along mid-Cretaceous thrust faults (Miller and others, 1994). The sequences are intruded by mid-Cretaceous to middle Eocene plutons, mainly diorite, tonalite, granodiorite, quartz monzonite, and granite. Sheetlike tonalite plutons emplaced just east of the Juneau Gold Belt and undeformed granite and granodiorite bodies that are emplaced farther to the east are between 55 and 48 Ma (Gehrels and others, 1991). The structural grain of the belt is defined by northwest-striking, moderately to steeply northeast-dipping, penetrative foliation that developed between Cretaceous and Eocene time (Miller and others, 1994). The majority of the veins in the Juneau Gold Belt strike northwest. Isotopic dates indicate that the auriferous veins in the Juneau Gold Belt formed between 56 and 55 Ma (Miller and others, 1994; Goldfarb and others, 1997).
Geologic map unit (-134.311665834082, 58.2822728482868)
Mineral deposit model Silver-gold vein with sulfides
Age of mineralization Isotopic dates indicate that the auriferous veins in the Juneau Gold Belt formed between 56 and 55 Ma (Miller and others, 1994; Goldfarb and others, 1997).

Production and reserves

Workings or exploration The deposit at the Glacier mine was discovered in 1887 and operated intermittently until 1911. The mine has 3,200 feet of workings, 1,200 feet of connecting raises, and 5 adits. The Glacier and the geologically similar, Silver Queen (JU175) mines were connected in 1903 (Spencer, 1906).
Indication of production Yes; small
Production notes By 1891 the combined production from the Glacier and Silver Queen mines was 19,300 ounces of silver and 41 ounces of gold. The U.S. Bureau of Mines estimated that the two mines produced nearly $500,000 worth of silver and gold at 1903 prices (Redman and others, 1989). Veins in the Glacier Mine were mined for as much as 700 feet down dip.

References

References

Gehrels, G.E., McClelland, W.C., Samson, S.D., and Patchett, P.J., 1991, U-Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska: Canadian Journal of Earth Sciences, v. 28, no. 8, p.1285-1300.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Miller, L.D., Goldfarb, R.J., Gehrels, G,E., and Snee, L.W., 1994, Genetic links among fluid cycling, vein formation, regional deformation, and plutonism in the Juneau gold belt, southeastern Alaska: Geology, v. 22, p. 203-206
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date 12/15/2001