Copper City

Mine, Active?

Commodities and mineralogy

Main commodities Ag; Au; Cu; Fe; Zn
Other commodities Ba; Pb
Ore minerals chalcopyrite; hematite; magnetite; pyrite; pyrrhotite; sphalerite
Gangue minerals calcite; epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale A-2
Latitude 55.13598
Longitude -132.60854
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Copper City Mine is shown on the USGS 1:63,360-scale topographic map in section 4, T. 78 S., R. 85 E.

Geologic setting

Geologic description

The Copper City Mine was discovered in 1898 and began production in 1910; it produced intermittently until 1910, when it flooded through a drill hole (Wright and Wright, 1908; Herreid and others, 1978; Roppel, 1991; Maas and others, 1991, 1995; Hedderly-Smith, 1999 [Inventory]). The total production was 85 tons of copper, 4,730 ounces of silver, and 341 ounces of gold (Maas and others, 1995). It was mined from an inclined, 300-foot shaft with several levels. The deposit was stoped to the surface and the main stope is exposed at the surface for about 300 feet just above the shoreline. In 1992, the deposit was leased to the American Copper and Nickel Company; they drilled one hole about 1,200 feet southwest of the old workings but did not encounter mineralization.
The rocks in the vicinity of the Copper City Mine are tuffaceous greenschist, pyroclastic breccia, and metabasite of the Wales Group of Late Proterozoic or Cambrian age (Herreid and others, 1978). In the older literature, the deposit is described as a quartz vein that trends about N25-40E and dips 40-60 NW (Wright and Wright, 1908; Wright, 1915). The modern interpretation is that it is a remobilized, volcanogenic massive-sulfide deposit in the Wales Group (Herreid and others, 1978; Maas and others, 1991, 1995; Hedderly-Smith, 1999 [Inventory]). The deposit is in a sequence of metakeratophyre, metaspilite, and distinctive grayish-red quartz-sericite schist (Herreid and others, 1978). The rocks and veins are locally folded and faulted and cut by several diabase dikes. The deposit consists of mineralized epidote-calcite-quartz veins that locally have high concentrations of chalcopyrite, pyrite, pyrrhotite, magnetite, hematite, and sphalerite; the wallrock adjacent to the veins commonly is bleached and contains talc. Recent detailed geochemical and isotopic work by Slack and others (2002) confirm that the deposit is of Late Proterozoic or Cambrian age. The deposit has been sampled several times with varying results depending on the selectivity of the sampling. Maas and others (1991), for example, collected a chip sample across about 10 inches of banded mineralization that contained 8.5 percent copper, 7.30 percent zinc, 2.5 ounces of silver per ton, 0.05 ounce of gold per ton, 570 parts per million (ppm) lead, and 7,000 ppm barium. Hedderly-Smith (1999 [Inventory]) collected a composite high-grade sample from the dumps that contained 8.17 percent copper, 10.31 percent zinc, 3.41 ounces of silver per ton, and 0.185 ounce of gold per ton. A sample across 3 inches of massive sulfide in place contained 10.77 percent copper, 5.58 percent zinc, 1.82 ounces of silver per ton, and 0.171 ounce of gold per ton.
Geologic map unit (-132.610198452572, 55.1356276900268)
Mineral deposit model Volcanogenic Cu-Fe-Zn massive sulfide deposit (Cox and Singer, model 28a).
Mineral deposit model number 28a
Age of mineralization A remobilized Late Proterozoic or Cambrian volcanogenic massive sulfide deposit.
Alteration of deposit The wallrock adjacent to the veins commonly is bleached and contains talc.

Production and reserves

Workings or exploration The Copper City Mine was discovered in 1898 and began production in 1910; it produced intermittently until 1910, when it flooded through a drill hole. It was mined from an inclined, 300-foot shaft with several levels. The deposit was stoped to the surface and the main stope is exposed at the surface for about 300 feet just above the shoreline. In 1992, the deposit was leased to the American Copper and Nickel Company; they drilled one hole about 1,200 feet southwest of the old workings but did not encounter ore.
Indication of production Yes; small
Reserve estimates Probably none.
Production notes Total production from 1902 to 1910 was 85 tons of copper, 4,730 ounces of silver, and 341 ounces of gold (Maas and others, 1995).

Additional comments

The Copper City Mine is on or surrounded by land that has been conveyed to the Sealaska Corporation, who hold the surface and subsurface rights, or the land is under application for transfer to them.

References

MRDS Number A010075

References

Hedderly-Smith, D.A., 1990, Report of the 1989 field season - Sealaska Mineral Reconnaissance Project: Sealaska Corporation, 58 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1991, Report of the 1990 field season-Sealaska Mineral Reconnaissance Project: Sealaska Corporation: Sealaska Corporation, 2 vols., 180 p., 13 plates. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1992, Report of the 1991 field season - Sealaska Mineral Reconnaissance Project: Sealaska Corporation, 2 vols., 225 p. 23 plates. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska).
Roppel, Patricia, 1991, Fortunes from the earth: Manhattan, Kansas, Sunflower University Press, 139 p.
Slack, J.F., Shanks, W.C. III, Karl, S.M., Ridley, W.I., and Bittenbender, P.E., 2002, Geochemical and sulfur isotope compositions of Late Proterezoic and early Paleozoic volcanogenic massive sulfide deposits, Prince of Wales Island and vicinity, southeastern Alaska (abs.): Geological Society of America, Abstracts with Programs, v. 34 (6), p. 113.
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004