Duke

Mine, Inactive

Alternative names

Reynolds Alaska
Banta Shaft
Iron Mountain No. 6
Iron Mountain No. 4

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au
Ore minerals chalcopyrite; gold; pyrite; pyrrhotite; silver
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale A-3
Latitude 60.0149
Longitude -147.9244
Nearby scientific data Find additional scientific data near this location
Location and accuracy This mine is located in the SW1/4 section 9, T. 2 S., R. 9 E., of the Seward Meridian. It is about 0.5 mile southeast of Horseshoe Bay at an elevation of 125 feet. This is location 259 of Cobb and Tysdal (1980) and location S-3 of Jansons and others (1984). This location is accurate to within 300 feet.

Geologic setting

Geologic description

The deposit at the Duke mine consists of massive sulfide lenses in northeast-striking, interbedded slate and graywacke of the Orca Group of early Tertiary age (Kurtak and Jeske, 1986). The lenses vary from 4 to 27 feet wide and have a strike length of as much as 151 feet. The deposit occurs on the northwest limb of a shallowly northeast-plunging antiform (Stejer, 1956). The sulfide minerals are mostly pyrite with minor amounts of chalcopyrite and pyrrhotite (Stejer, 1956). The typical mineralization consists of a disseminated halo of pyrite surrounding massive pyrite with some chalcopyrite (Stejer, 1956). The footwall of the massive sulfide lenses is in many places a slate bed, and the highest grade of copper mineralization is under the footwall (Kurtak and Jeske, 1986).
Within or near the massive sulfide lenses, the country rock shows varied degrees of silicification, sericitization, and kaolinization (Stejer, 1956). Some faulting occurs that is generally parallel to bedding. Surface outcrops located about 100 feet from the shaft indicate that the mineralized belt has a width of 200 to 250 feet. It appears to be on the same trend as the Duchess (SR302) mineralized zone, which lies 2,400 feet north of this deposit (Kurtak and Jeske, 1986).
Geologic map unit (-147.926415186677, 60.0142473065429)
Mineral deposit model Besshi massive sulfide (Cox and Singer, 1986; model 24b)
Mineral deposit model number 24b
Age of mineralization Tertiary or younger; the mineralization is in rocks of the Orca Group of Tertiary age.
Alteration of deposit There is strong asymmetric sericite-chlorite alteration associated with the massive sulfide mineralization (Rogers and Hoyt, 1999).

Production and reserves

Workings or exploration The initial claims were staked in 1898, and by 1907, a two-compartment shaft had been sunk on the property. In 1908, the shaft was deepened to 110 feet, but the site abandoned when the shaft flooded. In 1918, the shaft was pumped out, and a total of 311 feet of crosscuts and drifts was completed. The property was abandoned until 1970, when Northwest Exploration drilled several core holes (Kurtak and Jeske, 1986).
Indication of production Yes; small
Reserve estimates There are measured reserves of 68,800 tons of ore containing 1.32 percent copper, 0.06 ounce of gold per ton, and 0.05 ounce of silver per ton (Kurtak and Jeske, 1986). Indicated reserves are 200,000 tons of ore containing 1.32percent copper, 0.06 ounce of gold per ton and 0.06 ounce of silver per ton (Rogers and Hoyt, 1999).
Production notes An unspecified amount, believed to be small, of production was reported in 1907 (Kurtak and Jeske, 1986).

Additional comments

This mine is known as the Reynolds-Alaska Development Co. in Cobb and Tysdal (1980 [MF-880-A]).

References

References

Rogers, R., and Hoyt, M., 1999, Mineral prospects on Chugach Alaska Corporation lands: Chugach Alaska Corporation in-house report, 10 p., 1 table, 10 maps.
Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1916: U.S. Bureau of Mines Bulletin 153, 89 p.
Reporters Jeff A. Huber and Carol S. Huber (Anchorage)
Last report date 10/15/2001