Alaska-Washington

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Zn
Ore minerals arsenopyrite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale C-3
Latitude 58.5831
Longitude -134.8531
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Alaska-Washington prospect is at an elevation of about 2,200 feet near the ridge crest between at the head of Bessie Creek. It is about one-quarter of a mile north of the center of section 16, T. 38 S., R. 64 E. of the Copper River Meridian. The prospect is marked by mine and prospect symbols on the Juneau C-3 topographic map. The location is accurate.

Geologic setting

Geologic description

The Alaska-Washington deposit consists of a series of parallel quartz veins in metamorphosed volcanic conglomerate (Knopf, 1912). The veins strike east-west, dip steeply to the south, and can be traced discontinuously for 1,500 feet along strike. The veins display slickensides and shearing along their margins, and the wallrock is altered and bleached. The veins are up to 6 feet thick, average 1.4 feet thick, and contain arsenopyrite, pyrite, and minor sphalerite. The deposit was discovered in 1897 and developed by a 30 foot shaft and four adits totaling 500 feet. U.S. Bureau of Mines samples contained up to 0.147 ounce of gold per ton (Redman and others, 1989). The area was explored by Noranda in 1981 and by Monument Resources in 1988 (Barnett, 1988).
This prospect is in the Juneau Gold Belt, which consists of more than 200 auriferous quartz vein deposits that have produced nearly 7 million ounces of gold. These gold-bearing mesothermal quartz vein systems form a 160-km-long by 5- to 8-km-wide zone 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 (-134.854892324449, 58.582775042914)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
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).
Alteration of deposit The wallrocks of veins are altered and bleached.

Production and reserves

Workings or exploration The deposit was discovered in 1897 and developed by a 30 foot shaft and four adits totaling 500 feet. The area was explored by Noranda in 1981 and by Monument Resources in 1988 (Barnett, 1988).
Indication of production None

References

MRDS Number A012065

References

Barnett, J.C., 1988, 1988 Summary report, Bessie gold project: Unpublished report for Monument Resources, Ltd., 35 p.
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