Lichen

Prospect, Active

Alternative names

Rush

Commodities and mineralogy

Main commodities Ag; Au; Cu
Ore minerals bornite; chalcopyrite; covellite; digenite; malachite
Gangue minerals epidote; feldspar; quartz

Geographic location

Quadrangle map, 1:250,000-scale TK
Quadrangle map, 1:63,360-scale D-1
Latitude 62.8893
Longitude -147.3355
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Lichen prospect is at an elevation of about 3,150 feet, about 6 miles west of the Susitna River and 4.0 miles southeast of the center of Coal Lake. The prospect is about 0.15 mile west of the center of sec. 2, T. 32 N., R. 11 E., Seward Meridian. The location is accurate.

Geologic setting

Geologic description

The Lichen prospect is a stratabound copper deposit in Triassic(?) metavolcanic rocks. Veins and disseminated sulfides occur in a mafic, volcanic flow (Smith and others, 1975; Schmidt and others, 2002). The ore minerals are confined to a single flow, and consist of disseminations and veinlets of bornite, chalcopyrite, covellite, digenite, and malachite. The veinlets average less than 0.4 inch thick and contain quartz, feldspar, and epidote as well as sulfides. The mineralized zone is about 6 feet wide and 3,000 feet long. it strikes N60W and dips nearly vertically. The host rock has undergone greenschist-grade regional metamorphism and is coated with secondary iron and copper minerals. Samples of mineralized rock contained up to 4.5 percent copper, 16 parts per million (ppm) gold, and 68 ppm silver (Smith and others, 1975).
The prospect was explored in the 1970s by Cities Service Minerals using soil geochemical sampling, ground magnetic and EM surveys, and excavation of 2 trenches. Seraphim Engineering and Cities Service Minerals Company staked 145 claims in 1975-1976. The Amphitheater 1-25 claims were staked by Cominco American in 1988.
Alaska Ventures, Inc. (Bundtzen, 2008) began work on the Lichen deposit in 2005. They describe the prospect as a basaltic copper deposit that consists mainly of bornite and chalcopyrite in quartz veinlets in weakly metamorphosed, sub-alkaline basalt of Permian or Carboniferous age. The quartz veinlets are associated with epidote flooding in the basalt; other base metals are lacking although samples contain significant gold and silver values. In addition to the original discovery, work in 2007 located at least 6 other occurrences of similar mineralization spread over an area of several square miles. In the discovery zone, they defined an area about 360 meters long by 160 meters wide where the average value for the sulfide-quartz veinlets is about 1.75 percent copper, 30.5 grams of silver per tonne and 0.475 gram of gold per ton. Placer gold, probably of local origin, can be panned from most of the streams that drain the ridge on which the mineralization occurs. A soil geochemical survey outlined three, northwest-trending copper-silver-gold anomalies, the best of which coincided with the Lichen discovery but several were in areas covered by thick glacial cover. A ground IP survey covered an area about 1,600 meters by 2,600 meters in size and outlined several anomalies that suggest mineralization. The sampling and the geophysical and geochemical surveys indicate that the mineralization is along a northwest-striking zone about 4.0 kilometers long and 200 meters wide.
Geologic map unit (-147.337733601137, 62.8888482533001)
Mineral deposit model Basaltic copper (Cox and Singer, 1986; model 23).
Mineral deposit model number 23
Age of mineralization Early work suggests the deposit occurs in Triassic(?) metabasalt; later work suggests the basalt is Permian to Carboniferous.
Alteration of deposit The volcanic host rock is altered to chlorite and epidote and stained with secondary iron and copper minerals.

Production and reserves

Workings or exploration The prospect was explored in the 1970s by Cities Service Minerals using soil geochemical sampling, ground magnetic and EM surveys, and excavation of 2 trenches. Seraphim Engineering and Cities Service Minerals Company staked 145 claims in 1975-1976. The Amphitheater 1-25 claims were staked by Cominco American in 1988. As of January 1, 2000 a large block of state mining claims and prospecting sites covered the prospect (Northern Associates Inc., written communication, 2001). In 2005-2007, Alaska Ventures, Inc. explored the deposit by surface sampling, soil geochemistry, and ground IP geophysical surveys.
Indication of production None

Additional comments

MAS/MILS number 20700053.

References

MRDS Number A012199

References

Bundtzen, T.K., 2008, Lichen--a promising copper-silver-gold project ready for drill-testing in 2008: Unpublished report for Alaska Ventures, Inc. by Pacific Rim Geological Consulting, Inc., Fairbanks, Alaska, 10 pages.
Reporters R.K. Rogers (U. S. Geological Survey contractor); D.J. Grybeck (Port Ludlow, WA)
Last report date 6/5/2008