Threeman Mining Co.

Prospect, Inactive

Alternative names

Billygoat Mountain

Commodities and mineralogy

Main commodities Cu; Zn
Other commodities Ag
Ore minerals chalcopyrite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-7
Latitude 60.8281
Longitude -146.5133
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at an elevation of about 1750 feet, about 0.1 mile east of the summit of Billygoat Mountain. It is in the SW1/4 sec. 17, T. 12 S., R. 7 W., of the Copper River Meridian. The location of the site is accurate to within 100 ft. This prospect was located in the field in 2014. This prospect is shown as site C-68 by Janson and others (1984) and as #18 by Cobb (1972: MF-392).

Geologic setting

Geologic description

This prospect consists of two sulfide-bearing shear zones in mafic volcanic rocks of the Tertiary Orca Group (Nelson and others, 1985). The zones range in width from a few inches to five feet and contain lenses and stringer zones of chalcopyrite, pyrite, and pyrrhotite. Samples grade up to 6 percent Cu (Capps and Johnson, 1913).
Capps and Johnson (1913) reported adits at 1150 ft. and 1750 ft. elevation. The lower adit was 30 ft. long and the upper adit was 70 ft. long. Jansons and others (1984) reported that a grab sample from the 70 ft. adit contained 3.8 percent Cu, 0.2 percent Zn, and 7.5 parts per million (ppm) Ag. Gossan from the area contained 1.55 percent Cu, 0.4 percent Zn, and 13 ppm Ag.
A 2014 grab sample from below the upper 1750 ft adit contained 0.04 percent Cu, 0.01 percent Zn and a trace of Ag at 0.006 ppm. A stream sediment sample collected approximately 1000 ft east of the 1750 ft adit contained 0.024 ppm Au, 0.17 ppm Ag, 0.02 percent Cu, and 0.0082 percent Zn (Angel, 2014).
Geologic map unit (-146.518989111279, 60.8254490677747)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986; model 24a)
Mineral deposit model number 24a
Age of mineralization Tertiary based on the age of the host rocks.
Alteration of deposit Local oxidation of sulfide minerals.

Production and reserves

Workings or exploration
Capps and Johnson (1913) reported adits at 1150 ft. and 1750 ft. elevation. The lower adit was 30 ft. long and the upper adit was 70 ft. long. Jansons and others (1984) reported that a grab sample from the 70 ft. adit contained 3.8 percent Cu, 0.2 percent Zn, and 7.5 ppm Ag. Gossan from the area contained 1.55 percent Cu, 0.4 percent Zn, and 13 ppm Ag.
A 2014 grab sample from below the upper 1750 ft adit contained 0.04 percent Cu, 0.01 percent Zn and a trace of Ag at 0.006 ppm. A stream sediment sample collected approximately 1000 ft east of the 1750ft adit contained 0.024 ppm Au, 0.17 ppm Ag, 0.02 percent Cu, and 0.0082 percent Zn (Angel, 2014).
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

Crowe and others (1992; 1993) and Sainsbury (1993) discuss the genesis of the volcanogenic massive sulfide deposits in this area.
Chugach Alaska Corporation, Anchorage, Alaska has control of these lands.
In 2014 the coordinate location was updated and is accurate for the upper 1750 ft adit. The lower adit couldn't be located (Angel, 2014).

References

MRDS Number 10307360

References

Angel, A.K., 2014, Mineral Assessment of Chugach Alaska Lands, Unpublished Report, 21p. (Report held by Chugach Alaska Corporation, Anchorage, Alaska).
Sainsbury, C.L., 1993, Geology and geochemistry of volcanogenic massive sulfide deposits and related igneous rocks, Prince William Sound, south-central Alaska, A discussion: Economic Geology, v. 88, p. 1284-1285.
Reporters S.W. Nelson, Anchorage, AK; A.K. Angel (Alaska Earth Sciences, Inc.)
Last report date 9/4/2014