Copper Bullion

Prospect, Inactive

Alternative names

Rua Cove
Iron Bullion Nos. 1-3
Bullion Nos. 1-16

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Zn
Ore minerals chalcopyrite; pyrrhotite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale B-2
Latitude 60.3524
Longitude -147.6498
Nearby scientific data Find additional scientific data near this location
Location and accuracy The prospect is located on the north side of an unnamed creek that drains into Rua Cove. There are workings present from an elevation of 170 feet to an elevation of 1,200 feet. The prospect is in the NW1/4 section 13, T. 3 N., R. 10 E., of the Seward Meridian. This is location 213 of Cobb and Tysdal (1980) and location S-67 of Jansons and others (1984). This location is accurate to within 300 feet. The mine symbol on the 1:63,360-scale B-2 topographic map is this prospect.

Geologic setting

Geologic description

Bedrock at this prospect is greenstone surrounded by shale and graywacke; all these rocks are part of the Orca Group of early Tertiary age (Cobb and Tysdal, 1980). The greenstones are cut by a N 15 E-trending shear zone that dips from 60 W to 80 E but in most places is vertical to 80 W (Stefansson and Moxham, 1946). Massive sulfide bodies consisting of pyrrhotite and chalcopyrite occur within the zone and along the walls. Within the zone, greenstone contains disseminated sulfides with lenses of massive sulfides (Stefansson and Moxham, 1946). Most of the largest sulfide lens is 30 to 50 feet wide, and parts of it reach 100 feet wide. The strike length of the largest sulfide lens is about 400 feet. Its down-dip extension determined by drilling is more than 500 feet (Stefansson and Moxham, 1946). A magnetic survey indicated that there are two large unexplored anomalies, one to the north and one to the south (Richter, 1965). Both bodies are on strike with the deposit.
Bedrock exposed in the workings consists of three distinct types of greenstone. The results of a thin-section study by Stefansson and Moxham (1946) indicated that probably the most abundant type is fine-grained, greenish to black rock. That rock originally consisted of feldspar microlites, small grains of augite, and perhaps some ilmenite. These minerals have been altered to chlorite, prehnite, clinozoisite, and leucoxene. The second type is a blocky dark-gray porphyritic rock that locally shows pillow structures. In thin section this greenstone consists of large phenocrysts of labradorite in a groundmass of altered glass (palagonite). The rims of the pillows are glassy. The third type of greenstone is a medium-grained, gray-green rock with a composition of quartz diorite. Euhedral augite is distributed in a groundmass of labradorite or andesite and quartz.
Geologic map unit (-147.651772537427, 60.3517778627368)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986; model 24a)
Mineral deposit model number 24a
Age of mineralization Tertiary or younger; the occurrence is in rocks of the Orca Group of Tertiary age.
Alteration of deposit Basalt is altered to greenstone.

Production and reserves

Workings or exploration
Development on the prospect consists of two adits. The main adit at an elevation of 320 feet has a total of 2,420 feet of drifts and crosscuts. The second adit is 600 feet southeast of the main adit at an elevation of 170 feet; it is 590 feet long.
Several buildings were built on the site over the years, but only one is still standing (Kurtak and Jeske, 1986). Power was generated onsite by both a water-powered generator and by diesel generators (Kurtak and Jeske, 1986).
The property was explored by drilling in 1929-30, 1948-49, 1972-73, and 1976. Some drill core remains on the site (Kurtak and Jeske, 1986). Geophysical exploration in 1964 by the U.S. Bureau of Mines delineated two untested anomalies (Kurtak and Jeske, 1986). Geochemical surveys were done by Texasgulf in 1976-77. Sampling and drill results indicated a resource of 1,988,000 tons of ore with a grade of 0.57 percent copper, 42.4 percent iron, 0.005 ounce of gold per ton, and 0.1 ounce of silver per ton (Kurtak and Jeske, 1986). Production consisted of 1,000 pounds of ore shipped for testing in 1909.
Indication of production None
Reserve estimates Stefansson and Moxham (1946) reported measured reserves are 25,000 tons of 1.25 percent copper and indicated and inferred resources of 1.3 million tons of ore at a grade of 1.25 percent copper. Rutledge (1953) calculated indicated and inferred resource of 592,000 tons at 1.24 percent copper or 1,988,000 tons of ore with a grade of 0.57 percent copper. Additional commodities include 42.4 percent iron, 0.005 ounce of gold per ton, and 0.1 ounce of silver per ton (Kurtak and Jeske, 1986). Rogers and Hoyt (1999) estimate a reserve for the prospect of 1,320,000 tons of ore containing 1.2 percent copper and 132,000 ounces of silver.
Production notes Grant and Higgins (1909) reported 1,000 pounds of ore shipped for testing. The test shipment contained 1.68 percent copper, 47.9 percent iron, 31.5 percent sulfur, and 15 percent SiO2 (Grant and Higgins, 1909).

Additional comments

This prospect is owned by Chugach Alaska Corporation.

References

MRDS Number A010374

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.
Reporters Jeff A. Huber and Carol S. Huber (Anchorage)
Last report date 1/3/2002