Chichagof Prosperity

Prospect, Undetermined

Commodities and mineralogy

Main commodities Au
Ore minerals gold
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale C-7
Latitude 57.6875
Longitude -136.1225
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Chichagof Prosperity prospect is at about sea level at the northwest foot of Doolth Mountain. The prospect is 0.2 mile west-northwest of the southeast corner of sec. 23, T. 48 S., R. 57 E. It is location P-63 of Bittenbender and others (1999), location 26 of Cobb (21972, 1978), and MAS no. 0021140024 (U.S. Bureau of Land Management, 2002). The location is accurate.

Geologic setting

Geologic description

Johnson and Karl (1985) map the rocks in the area of this prospect as Cretaceous graywacke and argillite with sparse, lenticular beds of basalt. The rocks are cut by numerous high-angle, mainly northwest-striking faults. They include the extensions of the faults at the Hirst (SI087) and Chichagof (SI093) mines, which control the mineralization there and straddle this prospect.
Reed and Coats (1941) describe the prospect as auriferous quartz veins up to 3 feet thick in graywacke. The veins are mainly localized along major faults and splits from them that strike northwest and dip steeply southwest, about the same as the bedding in the graywacke. At the time of Reed and Coats' visit, the underground workings included a 45-foot tunnel and a crosscut about 150 feet long with a flooded winze of unknown depth. Surface workings included several pits and trenches. Reed and Coats provide no assay or production figures, but the extent of the workings suggests that some gold may have been produced. Bittenbender and others (1999), citing Still and Weir (1981), report that samples across a 0.2- to 2.8-foot-thick vein contained up to 0.695 ounce of gold per ton.
Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler, 1995; Goldfarb, 1997; Goldfarb and others, 1997). ARDF record SI087 provides an overview of the geology of auriferous quartz veins in the Chichagof Mining District.
Geologic map unit (-136.124327423966, 57.6871265130929)
Mineral deposit model Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler and others, 1995; Goldfarb, 1997; Goldfarb and others, 1997).

Production and reserves

Workings or exploration At the time of Reed and Coats' visit, the underground workings included a 45-foot tunnel and a crosscut about 150 feet long, with a flooded winze of unknown depth. Surface workings included several pits and trenches.
Indication of production Undetermined
Production notes There is no record of production, but the extent of the workings suggests that some gold may have been produced.

Additional comments

The prospect is in West Chichagof-Yakobi Wilderness.

References

MRDS Number A013264

References

Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p.
Goldfarb, R J., 1997, Metallogenic evolution of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 4-34.
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.
Haeussler, P J., Bradley, D., Goldfarb, R., Snee, L., and Taylor, C., 1995, Link between ridge subduction and gold mineralization in southern Alaska: Geology, v. 23, no. 11, p. 995-998.
U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]
Reporters H.C. Berg (U.S. Geological Survey)
Last report date 10/16/2004