Anderson

Prospects, Undetermined

Commodities and mineralogy

Main commodities Au
Ore minerals gold
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale C-7
Latitude 57.6342
Longitude -136.021
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Anderson prospects are just above sea level on the north shore of Sister Lake at the mouth of the passage leading to Lake Anna. The prospects are 0.4 mile east of the center of sec. 12, T. 49 S., R. 58 E. They are location P-83 of Bittenbender and others (1999), location 37 of Cobb (1972, 1978), and MAS no. 0021140007 (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 these prospects as Cretaceous melange cut by numerous steeply-dipping, mainly northwest-striking faults. Reed and Coats (1941) note that one of the prospects lies on a strong fault that on aerial photos appears to be the coalesced extensions of the faults at the Hirst (SI087) and Chichagof (SI093) mines which control the mineralization there. Bittenbender and others (1999) report that the prospects are on strike with the Chichagof Fault; and Johnson and Karl's (1985) map indicates that they are on the projected trace of the Hirst Fault.
Reed and Coats (1941) describe fault-controlled quartz veins in graywacke and some interbedded greenstone at these prospects. The country rocks strike N45-50W and dip 65-80SW, and the faults strike N12-25E and dip 72SW-88SE. The faults contain up to 2 feet of gouge and as much as 2 feet of vein quartz and minor calcite. Graphitic graywacke fragments in the quartz are silicified and sericitized. Workings include a 36-foot tunnel and one or more open cuts up to 40 feet long. Bittenbender and others (1999), citing Still and Weir (1981), report sample values up to 1.5 parts per million gold. There is no record of production.
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). ARDF record SI087 provides an overview of the geology of auriferous quartz veins in the Chichagof Mining District.
Geologic map unit (-136.022819808763, 57.6338324615774)
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).
Alteration of deposit Graphitic graywacke fragments in the quartz are silicified and sericitized.

Production and reserves

Workings or exploration Workings include a 36-foot tunnel and one or more open cuts up to 40 feet long.
Indication of production Undetermined
Production notes There is no record of production.

Additional comments

The prospects are in West Chichagof-Yakobi Wilderness.

References

MRDS Number A013281

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