Falck

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu; Zn
Other commodities Ag
Ore minerals chalcopyrite; pyrite; pyrrhotite; native cu; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-7
Latitude 60.866
Longitude -146.569
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Falck prospect is at an elevation of about 2400 ft., about 0.5 mile east of Copper Mountain. It is in S1/2 sec. 36, T. 11 S., R. 8 W., of the Copper River Meridian. The location is accurate to within 1000 ft. This prospect is shown as #12 in Cobb (1972: MF-392) and as C-78 in Jansons and others (1984).

Geologic setting

Geologic description

The country rocks at this prospect are mafic volcanic rocks and sedimentary rocks of the Tertiary Orca Group (Nelson and others, 1985). The deposit consists of sulfide minerals and native copper in veinlets and as disseminations in a northwest-striking, steeply-dipping shear zone in the volcanic and sedimentary rocks (Capps and Johnson, 1915). The sulfides are chalcopyrite, pyrite, pyrrhotite, and sphalerite.
Analyses of chip samples contained 0.11percent to 7.5 0.11percent Cu, 240 parts per million (ppm) to 0.68 0.11percent Zn, and 0.7 ppm to 18.3 ppm Ag (Jansons and others, 1984).
A 2014 grab sample collect near the Falck prospect contained 0.034 ppm Au, 0.11 ppm Ag, 112 ppm Cu, and 100 ppm Zn. Another grab sample collected roughly 1000 ft to the east of the Falck prospect coordinates contained 0.04 ppm Ag, 122.5 ppm Cu, and 94 ppm Zn (Angel, 2014).
Geologic map unit (-146.570997843057, 60.8654526543219)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986; model 24a)
Mineral deposit model number 24a
Age of mineralization Probably Tertiary based on the age of the host rocks.
Alteration of deposit Oxidation of copper minerals (Angel, 2014).

Production and reserves

Workings or exploration
Capps and Johnson (1915) report a 25 ft. adit and a 15 ft. adit, along with minor surface cuts. In the 1980s only the 25 ft. adit was still accessible (Jansons and others, 1984). Analyses of chip samples contained 0.11percent to 7.5 0.11percent Cu, 240 parts per million (ppm) to 0.68 0.11percent Zn, and 0.7 ppm to 18.3 ppm Ag (Jansons and others, 1984).
Field work including sampling was performed in 2014. A 2014 grab sample collect near the Falck prospect contained 0.034 ppm Au, 0.11 ppm Ag, 112 ppm Cu, and 100 ppm Zn. Another grab sample collected roughly 1000 ft to the east of the Falck prospect coordinates contained 0.04 ppm Ag, 122.5 ppm Cu, and 94 ppm Zn (Angel, 2014).
Indication of production None
Reserve estimates Inferred reserves of 200 tons at 2.03 percent Cu, 0.23 percent Zn, 13 ppm Ag (Jansons and others, 1984).
Production notes None.

Additional comments

Nelson and others (1985) interpret the country rocks as accreted ocean crust. 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.

References

MRDS Number A010422

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 9/9/2014