Canwell Ridge Prospect, Delta River District, Southeast Fairbanks Borough, Alaska, USA

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Location: The prospect is at an elevation of 4,700 feet on the southwest valley wall of lower Canwell Glacier. It is in the NW1/4NW1/4 section 26, T. 18 S., R. 11 E., Fairbanks Meridian. Access to the property is by a 3-mile-long trail from the end of a dirt road (not shown on the 1984 topographic map) on the east side of the Richardson Highway at mile 213.5 approximately 1 mile south of Millers Roadhouse.
Geology: At this prospect segregations of disseminated pyrrhotite, chalcopyrite, and pentlandite occur in oxidized iron-, copper-, and nickel-stained mafic gabbro at the base of the Canwell mafic-ultramafic intrusive complex of Late Triassic age. The gabbro is in contact with quartz monzonite (W.T. Ellis, oral communication, 1998). The complex is a 2.5-mile-long by 0.5-mile-wide southwest-dipping sill that is intruded by a Cretaceous or Tertiary quartz diorite to quartz monzonite stock (Barker, 1988). The complex consists of a dunite core that grades outward into wehrlite, feldspathic peridotite, and mafic gabbro (W.T. Ellis, oral communication, 1998). The Canwell Ridge prospect was discovered by American Copper and Nickel Company (ACNC) in 1995. ACNC chip samples from a 10-foot-long hand-dug trench contained 0.59 percent nickel, 0.64 percent copper, 232 parts per billion (ppb) gold, 687 ppb palladium, and 687 ppb platinum. A high-grade grab sample from the same trench contained 8.6 percent nickel, 0.86 percent copper, 0.2 percent cobalt, 466 ppb gold, 3,160 ppb palladium, and 1,860 ppb platinum (A.T. MacGibbon, written communications, 1997-2001). ACNC drilled one hole to intersect the basal zone of the sill at depth, but it intersected the quartz monzonite at the 700-foot target depth.
Workings: Exploration in the area of this prospect has been by American Copper and Nickel Company (ACNC) working with Fort Knox Gold Resources Inc. Exploration from 1994 through 2001 included rock sampling, hand trenching, airborne and ground geophysical surveys, and completion of five diamond drill holes. The Canwell Ridge prospect is at the east end of a 3,000-foot-long electromagnetic conductor detected by a large-loop survey completed by ACNC in 1998 (W.T. Ellis, oral communication, 1998). ACNC chip samples from a 10-foot-long hand-dug trench contained 0.59 percent nickel, 0.64 percent copper, 232 parts per billion (ppb) gold, 687 ppb palladium, and 687 ppb platinum. A high-grade grab sample from the same trench contained 8.6 percent nickel, 0.86 percent copper, 0.2 percent cobalt, 466 ppb gold, 3,160 ppb palladium, and 1,860 ppb platinum (A.T. MacGibbon, written communications, 1997-2001). ACNC drilled one hole to intersect the basal zone of the sill at depth, but it intersected the quartz monzonite at the 700-foot target depth. The prospect is on active claims of Fort Knox Gold Resources.
Age: Late Triassic.
Alteration: The mafic gabbro is moderately silicified and serpentinized; copper, iron, and nickel minerals are oxidized.

Commodities (Major) - Au, Co, Cu, Ni, Pd, Pt
Development Status: None
Deposit Model: Ni-Cu-PGE in differentiated mafic-ultramafic sill.

References

Barker, J.C., 1988, Distribution of platinum-group elements in an ultramafic complex near Rainbow Mountain, east-central Alaska Range, IN Vassilou, A.H., Hausen, D.M., and Carson, D.J.T, eds, Process Mineralogy VII, Applications to mineral beneficiation: Proceedings of the Metal Society SME/AIME Joint [Annual] Meeting, Denver, Colo., p. 197-220.

Mineral List

Chalcopyrite 'Garnierite'

Malachite Pentlandite

Pyrrhotite

5 entries listed. 4 valid minerals.