Great Eastern

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Mo
Ore minerals pyrite

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale B-2
Latitude 58.2778
Longitude -134.4018
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Great Eastern prospect is at an elevation of approximately 100 feet on Douglas Island, immediately west of Douglas in Bear Creek and 1/2 mile southeast of Lawson Creek. It is in the NW1/4NE1/4 section 35, T. 41 S., R. 67 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Great Eastern prospect was discovered in 1888 when a portion of surface was ground-sluiced for gold. There is a 200-foot adit and a short shaft on the prospect. The deposit consists of black phyllite that has been intruded by a swarm of hydrothermally altered diorite sills (Redman and others, 1989). The sills vary from a few inches up to 20 feet thick. Alteration has destroyed most of the mafic minerals. The sills contain up to 3 percent disseminated pyrite. U.S. Bureau of Mines samples contained no significant gold values; they did, however, contain up to 164 ppm molybdenum (Redman and others, 1989).
The rocks in the general area are Upper Jurassic or Cretaceous marine argillite and graywacke, interbedded with andesite or basalt (Brew and Ford, 1985). The bedded rocks are regionally metamorphosed to prehnite-pumpellyite or greenschist grade, and cut by diorite or gabbro dikes and sills.
Geologic map unit (-134.403569497981, 58.2774716858749)
Alteration of deposit The diorite sills are hydrothermally altered. The alteration has destroyed most of the mafic minerals.

Production and reserves

Workings or exploration The deposit at the Great Eastern prospect was discovered in 1888 when a portion of surface was ground-sluiced for gold. There is a 200-foot adit and a short shaft on the prospect.
Indication of production None
Production notes The surface in the vicinity was ground sluiced for gold in 1888 but there is no record of the production.

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