Salt Chuck

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Zn
Ore minerals chalcopyrite; galena; pyrite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale PE
Quadrangle map, 1:63,360-scale D-4
Latitude 56.8408
Longitude -133.3226
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is near the center of the peninsula that separates North Arm from Towers Arm at the head of Duncan Canal. It is near the center of section 17, T. 58 S., R 77 E. The location is accurate.

Geologic setting

Geologic description

The Salt Chuck prospect was found in late 1978 when Amoco Minerals Co. carried out a major exploration program at the head of Duncan Canal that included aerial and ground geophysics, geologic mapping, soil and stream sediment geochemistry, and diamond core drilling over many hundreds of claims (AMOCO Mineral Company, 1979; Zelinska, 1979).
At Salt Chuck, airborne electromagnetic anomalies followed ground electromagnetic and soil geochemistry surveys. The prospect is tied to an 8,000-foot-long anomaly defined by airborne and ground geophysics and by five diamond drill holes that were drilled to test this anomaly. The holes were drilled to a depth of 600 to 1,000 feet along about 5,000 feet of the anomaly. Several massive-sulfide bands were cut in the drilling but they were thin, discontinuous and generally low grade. The best intersections were one that was 1.7 feet long and averaged 1.86 percent copper and another that was 10 feet long and averaged 0.877 percent copper.
The rocks in the vicinity of the Salt Chuck prospect are Devonian phyllite, schist, and greenstone (Karl and others, 1999).
Amoco geologists also located several outcrops of mineralization in this area (AMOCO Mineral Company, 1979; Zelinska, 1979). The westernmost is about 3 miles north of the tip of the peninsula between Towers Arm and North Arm and 0.6 mile inland from North Arm. The mineralization there is an outcrop 10 feet long by 5 feet wide that consists of a band of chalcopyrite-rich massive sulfides in rhyolite. Samples averaged 6.3 percent copper, 0.02 percent zinc, and 0.32 ounce of silver per ton. Another mineralized zone is about 2,000 feet to the east where three sulfide bands, each less than 6 inches thick, are exposed along the beach. The bands consist of chalcopyrite, sphalerite, and galena, in rhyolite. Samples contain 0.01 to 0.13 percent copper, 0.10 to 25.3 percent lead, 0.15 to 7.8 percent zinc, and 0.2 to 13.62 ounces of silver per ton. These outcrops of mineralization were examined and sampled by Still and others (2002); their analyses were generally similar to those done by Amoco. They also suggested that the prospects were likely to be replacement deposits rather than volcanogenic massive sulfide deposits.
Geologic map unit (-133.32433310857, 56.8404617790987)
Mineral deposit model Volcanogenic massive sulfide deposit? Replacement deposits?
Age of mineralization Devonian or later based on the age of the host rocks.

Production and reserves

Workings or exploration The Salt Chuck prospect was found in the late 1978 when Amoco Mineral Company Company carried out a major exploration program at the head of Duncan Canal that included aerial and ground geophysics, geologic mapping, soil and stream sediment geochemistry, and diamond core drilling over many hundreds of claims. At the Salt Chuck prospect, airborne electromagnetic anomalies were followed by ground electromagnetic and soil geochemistry surveys. The prospect is tied to an 8,000-foot-long anomaly defined by airborne and ground geophysics and by five diamond drill holes that were drilled to test this anomaly. The holes were drilled to a depth of 600 to 1,000 feet along about 5,000 feet of the anomaly.
Indication of production None

Additional comments

This prospect is now within the Petersburg Creek-Duncan Salt Chuck Wilderness which is closed to mineral exploration and mining.

References

References

Amoco Mineral Company, 1979, Behm Canal project D-77-37, geology and geophysics map: Unpublished map by Amoco Minerals Company, 1 sheet, scale 1:24,000. (Copy in the files of the Bureau of Land Management, Minerals Information Center, Juneau Alaska.)
Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002, Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p.
Zelinski, W., 1979, Termination report, Behm Canal project (D-77-36), southeastern Alaska: Unpublished report by Amoco Minerals Company, 5 p. (Copy in the files of the Bureau of Land Management, Minerals Information Center, Juneau Alaska.)
Reporters D.J. Grybeck (Port Ludlow, WA)
Last report date 4/8/2007