Alaska Chichagof

Mine, Undetermined

Commodities and mineralogy

Main commodities Ag; 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 57.6569
Longitude -136.1023
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Alaska Chichagof Mine is at an elevation of about 20 feet on the west side of Klag Bay, about 0.5 mile south of the ruins of the town of Chichagof. Figure 6 of Bittenbender and others (1999) shows the mine at the northwest corner of a patented block that Reed and Coats (1941, pl. 14) label a mill site. Bittenbender and others (fig. 6) also show an Alaska Chichagof adit at an elevation of 500 feet about 0.5 mile northwest of the mine. For this record, the site is plotted on the south boundary of sec. 36, 0.2 mile west of Klag Bay, in T. 48 S., R. 57 E. It is location P-71 of Bittenbender and others (1999), location 32 of Cobb (1972, 1978), and MAS no. 0021140005 (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 the Alaska Chichagof Mine as Cretaceous graywacke and argillite interbedded with sparse, lenticular beds of basalt. The rocks are cut by numerous high-angle, mainly northwest-striking faults. They include the extension of the fault at the , Chichagof Mine (SI-93), which controls the mineralization there and whose traces is about a mile northeast of this mine.
Reed and Coats (1941) describe the principal country rock at the Alaska Chichagof Mine as slaty graywacke that strikes northwest and dips steeply southwest. The graywacke is cut by auriferous quartz-bearing, north- to northwest-striking, steeply-dipping faults and splits from them, and by east-trending dikes. One of the the intersections of a dike with a fault apparently localizes an oreshoot. The quartz in the oreshoot is up to about 5 feet thick and the oreshoot was mined over a stope length of 10 to 35 feet, from a point 142 feet down the shaft to a point within 15 feet of the surface. Reed and Coats report a total of about 675 feet of tunnel, drifts, an inclined shaft, and a lower level; and that 302 tons of ore were stoped in 1936.
Bittenbender and others (1999), mainly citing Still and Weir (1981), report that the Alaska Chichagof deposit was discovered in 1928 and developed by an adit, 2 levels, a shaft, and stopes. Bittenbender and others (1999) state that 660 ounces of gold was produced in 1936 from 660 tons of ore, which reflects Still and Weir's (1981) report that the ore grade was nearly one ounce of gold per ton. Still and Weir's samples contained up to 36 parts per million (ppm) gold and 150 ppm silver. In the early 1980s, private interests attempted to reopen the workings; the results of that work have not been made public.
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 (-136.10412431263, 57.6565285133849)
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 Reed and Coats (1941) report a total of about 675 feet of underground workings, including a tunnel, drifts, inclined shaft, and a lower level. Bittenbender and others report that the Alaska Chichagof deposit was discovered in 1928 and developed by an adit, 2 levels, a shaft, and stopes.
Indication of production Yes; small
Production notes Reed and Coats report that 302 tons of ore were stoped in 1936. Bittenbender and others (1999) state that 660 ounces of gold was produced in 1936 from 660 tons of ore, which reflects Still and Weir's (1981) report that the ore grade was nearly one ounce of gold per ton. In the early 1980s, private interests attempted to reopen the workings; the results of that work have not been made public.

Additional comments

The mine is in West Chichagof-Yakobi Wilderness.

References

MRDS Number A013271

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