Seward

Prospect, Active

Alternative names

Thomas

Commodities and mineralogy

Main commodities Au
Ore minerals gold; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale D-4
Latitude 58.8536
Longitude -135.0664
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Seward prospect is at an elevation of about 2,600 feet, about 3 miles east of Pt. Sherman on Lynn Canal and 1.5 miles south-southwest of Lions Head Mountain in the Kakuhan Range. It is in the saddle above the Comet mine (JU036), in the NW1/4 section 10, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

Note: Beginning in the 1990s, this and other old mines and prospects in the vicinity were consolidated by Coeur-Alaska into a single property (Birak, 2006). They have carried out major new drilling and underground exploration that better defines the mineralization, largely blurs the geologic distinction among the old deposits, and extends the ore bodies greatly. They have developed a coherent modern interpretation of the mineralization as a single deposit which Coeur-Alaska intends to mine as a unit. This deposit is described separately in ARDF as the Kensington (Coeur-Alaska) deposit (JU261). For geologic reference purposes and for their historic value, the pre-Coeur-Alaska data for this and the other old mines and prospects that Coeur-Alaska consolidated are retained in ARDF.
The Seward prospect consists of a quartz vein in Jualin diorite. It is 5- to 12-feet thick, strikes N, dips E, and has been traced on the surface for approximately 1,100 feet. Samples collected before 1906 assayed up to 24 parts per million gold (Redman and others, 1989). The quartz contains free gold, but little or no sulfides (Kensington Mines, 1914). Workings include a 63-foot shaft with a 15-foot drift at the bottom, and 2 open cuts. The shaft and open cuts were completed during the 1890s.
Geologic map unit (-135.068215737469, 58.8532712367858)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization The age of mineralization in the Berners Bay district is about 55 Ma, the same as the other mesothermal gold-quartz-vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).
Alteration of deposit Hydrothermal alteration adjacent to the veins is characterized by reddish-brown ferroan dolomite alteration (Miller and others, 1995). Other alteration includes sericitization of plagioclase, chloritization and sulfidization of mafic minerals, and albitization of feldspars (Leveille, 1991).

Production and reserves

Workings or exploration Workings completed during the 1890s include a 63-foot shaft with a 15-foot drift at the bottom, and 2 open cuts. Placid Oil Co. drilled 3 core holes on the prospect in 1983; core samples assayed up to 0.7 ounce of gold per ton (Chris Croff, oral communication, 1987).
Indication of production None

References

References

Birak, D.J., 2006, Kensington gold project: Unpublished Technical Report for Cour d'Alene Mines, 116 p. (posted on www/.sedar.com, April 20, 2006).
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.
Leveille, R.A., 1991, Geology and gold deposits of the Jualin mine area, Berners Bay district, southeastern Alaska: Fairbanks, University of Alaska, M.S. thesis, 200 p.
Miller, L.D., Goldfarb, R.J., Snee, L.W., Gent, C.A., and Kirkham, R.A., 1995, Structural geology, age, and mechanisms of gold vein formation at the Kensington and Jualin deposits, Berners Bay district, southeast Alaska: Economic Geology, v. 90, p. 343-368.
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date 6/5/2008