Reagan

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; electrum; galena; pyrite; silver; sphalerite; tetrahedrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale B-1
Latitude 58.2752
Longitude -134.2835
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Reagan prospect is at an elevation of approximately 1,100 feet,on the north side of Sheep Creek. It is 3/4 mile east-southeast of Portal Camp and 1.5 miles southeast of Sheep Mountain, in the NW1/4NW1/4 section 34, T. 41 S., R. 68 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Reagan prospect was discovered in 1894 and has a 250-foot adit, 3 additional adits, a 42-foot winze, and a 40-foot shaft. Echo Bay Mines Ltd. explored the property in 1988. The deposit consists of 2 quartz veins in a shear zone along the contact between black phyllite and green phyllite. The veins dip southwest and are 1 to 3 feet thick. They contain arsenopyrite, chalcopyrite, electrum, galena, native silver, pyrite, sphalerite, and tetrahedrite. U.S. Bureau of Mines samples contained up to 52.2 ppm gold, 4,612.0 ppm silver, 1.71 percent zinc, and 0.97 percent lead. The U.S. Bureau of Mines has estimated a resource of 82,000 tons of ore of uncertain grade (Redman and others, 1989).
This prospect is in the Juneau Gold Belt, which consists of more than 200 gold-quartz-vein deposits that have produced nearly 7 million ounces of gold. These gold-bearing mesothermal quartz vein systems form a zone 160 km long by 5 to 8 km wide along the western margin of the Coast Mountains. The vein systems are in or near shear zones adjacent to west-verging, mid-Cretaceous thrust faults. The veins are hosted by diverse, variably metamorphosed, sedimentary, volcanic, and intrusive rocks. From the Coast Mountains batholith westward, the host rocks include mixed metasedimentary and metavolcanic sequences of Carboniferous and older, Permian and Triassic, and Jurassic-Cretaceous age. The sequences are juxtaposed along mid-Cretaceous thrust faults (Miller and others, 1994). The sequences are intruded by mid-Cretaceous to middle Eocene plutons, mainly diorite, tonalite, granodiorite, quartz monzonite, and granite. Sheetlike tonalite plutons emplaced just east of the Juneau Gold Belt and undeformed granite and granodiorite bodies that are emplaced farther to the east are between 55 and 48 Ma (Gehrels and others, 1991). The structural grain of the belt is defined by northwest-striking, moderately to steeply northeast-dipping, penetrative foliation that developed between Cretaceous and Eocene time (Miller and others, 1994). The majority of the veins in the Juneau Gold Belt strike northwest. Isotopic dates indicate that the auriferous veins in the Juneau Gold Belt formed between 56 and 55 Ma (Miller and others, 1994; Goldfarb and others, 1997).
Geologic map unit (-134.285264755303, 58.2748729226309)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Isotopic dates indicate that the auriferous veins in the Juneau Gold Belt formed between 56 and 55 Ma (Miller and others, 1994; Goldfarb and others, 1997).

Production and reserves

Workings or exploration The Reagan prospect was discovered in 1894 and has a 250-foot adit, 3 additional adits, a 42-foot winze, and a 40-foot shaft. Echo Bay Mines Ltd. explored the property in 1988.
Indication of production None
Reserve estimates The U.S. Bureau of Mines has estimated a resource of 82,000 tons of material with an uncertain grade.

References

MRDS Number A012040

References

Gehrels, G.E., McClelland, W.C., Samson, S.D., and Patchett, P.J., 1991, U-Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska: Canadian Journal of Earth Sciences, v. 28, no. 8, p.1285-1300.
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Miller, L.D., Goldfarb, R.J., Gehrels, G,E., and Snee, L.W., 1994, Genetic links among fluid cycling, vein formation, regional deformation, and plutonism in the Juneau gold belt, southeastern Alaska: Geology, v. 22, p. 203-206
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date 12/15/2001