Montezuma (Threeman Mining Co.)

Prospect, Inactive

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-7
Latitude 60.862
Longitude -146.568
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Montezuma prospect is at an elevation of about 1500 feet, about 0.5 mile southeast of Copper Mountain. It is in the N1/2 sec. 1, T. 12 S., R. 8 W., of the Copper River Meridian. The site location is accurate to within 1000 ft. This prospect is shown as site C-76 in Jansons and others (1984) and as site #13 in Cobb (1972: MF-392).

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 irregular lenses of quartz, chalcopyrite, pyrite, and pyrrhotite in several highly mineralized shear zones in the volcanic rocks (Mihelich and Wells, 1957).
A sample from a quartz-filled shear zone one foot wide in volcanic rocks contained 0.5 percent Cu, 0.08 oz. Ag/ton, and 0.18 oz. Au/ton (Mihelich and Wells, 1957). Jansons and others (1984) report that chip samples contained 0.74 percent to 3.2 percent Cu, 3.2 parts per million (ppm) to 20 ppm Ag, and grab samples contained 125 ppm to 0.75 percent Cu, and 0.92 ppm to 10 ppm Ag.
A 2014 stream sediment sample collected below the workings contained 0.008 ppm Au, 0.23 ppm Ag, 804 ppm Cu, and 207 ppm Zn (Angel, 2014).
Geologic map unit (-146.569998110366, 60.861452619304)
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 Oxidation of copper minerals (Angel, 2014).

Production and reserves

Workings or exploration
Mihelich and Wells (1957) report more than 300 feet of underground workings and 900 feet of surface stripping. A sample from a quartz-filled shear zone one foot wide in volcanic rocks contained 0.5 percent Cu, 0.08 oz. Ag/ton, and 0.18 oz. Au/ton (Mihelich and Wells, 1957). Jansons and others (1984) report that chip samples contained 0.74 percent to 3.2 percent Cu, 3.2 parts per million (ppm) to 20 ppm Ag, and grab samples contained 125 ppm to 0.75 percent Cu, and 0.92 ppm to 10 ppm Ag.
Field work including sampling was performed in 2014. A 2014 stream sediment sample collected below the workings contained 0.008 ppm Au, 0.23 ppm Ag, 804 ppm Cu, and 207 ppm Zn (Angel, 2014).
Indication of production None
Reserve estimates Inferred reserves of 200 tons at 1.67 percent Cu and 9.88 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 A010421

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