Glacier Mine, Juneau District, Juneau Borough, Alaska, USA
|Latitude & Longitude (WGS84):||58° 16' 57'' North , 134° 18' 36'' West|
|Latitude & Longitude (decimal):||58.28250,-134.31000|
|Köppen climate type:||Dfc : Subarctic climate|
Location: 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.
Geology: 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).
Workings: 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).
Age: 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: 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.
Commodities (Major) - Ag, Au; (Minor) - Cu, Pb, Zn
Development Status: Yes; small
Deposit Model: Silver-gold vein with sulfides
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
13 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Paleozoic - Triassic|
|Metasedimentary and minor metavolcanic rocks along the west side of the Coast plutonic complex of Brew and Morrell (1979b)|
Age: Early Triassic (252.17 Ma)
Description: MAINLAND BELT: METAMORPHIC ROCKS OF COAST PLUTONIC-METAMORPHIC COMPLEX: Dominantly well foliated and commonly lineated dark gray very fine to fine grained phyllite with minor thin dark gray semischist interlayers, weathers medium to dark gray; some extensive areas of interlayered green phyllite that weathers light green; the former are probably derived from a fine grained clastic section; the latter from either tuffs or fine grained volcanogenic sediments; metamorphic grade generally increases from prehnite pumpellyite/low greenschist facies in the southwest to upper greenschist facies in the northeast. Host rock for the A-J gold quartz stringer lode deposits.
Reference: Wilson, F.H., Hults, C.P., Mull, C.G, and Karl, S.M. (compilers). Geologic map of Alaska. doi: 10.3133/sim3340. U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196. 
|Permian - Devonian|
252.17 - 419.2 Ma
|Paleozoic sedimentary rocks|
Age: Paleozoic (252.17 - 419.2 Ma)
Lithology: Sedimentary rocks
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529.