Atoll

Prospect, Inactive

Commodities and mineralogy

Main commodities Zn
Other commodities Pb
Ore minerals smithsonite
Gangue minerals dolomite; ferricrete minerals

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale B-3
Latitude 63.417
Longitude -154.367
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Atoll prospect is situated at about 2,000 feet in elevation on the northwest slope of a ridge approximately 2.5 miles (4 km) northwest of Reef Ridge, in Section 11, T. 24 S., R. 23 E., of the Kateel River Meridian. Location is precisely known to within 100 feet (30 m).

Geologic setting

Geologic description

At the Atoll prospect, smithsonite-bearing, iron-oxide gossan covers an area of 300 feet by 50 feet (91 m by 15 m) in tectonized dolomite and micritic limestone; unit probably equivalent to the Paradise Fork Formation of Dutro and Patton (1982). Mineralized rubble constitutes about one percent of float on the hillslope. Host unit is Late-Ordovician based on fossils (Dutro and Patton, 1982). Age of mineralization is not known.
A large composite, chip-channel sample of 50 samples taken across the mineralized zone averaged 1.0 percent zinc and 395 ppm lead. A high-graded sample of 10 pieces of mineralized float contained 7.95 percent zinc but no lead. A strong zinc soil anomaly (1,900 to 4,000 ppm) covers a 1,000 feet by 4,000 feet (300 m by 122 m) area below the Atoll prospect (Andrews and Rishel, 1982).
Geologic map unit (-154.369331463561, 63.4164043079354)
Mineral deposit model Southeast Missouri Pb-Zn, (Cox and Singer, 1986; model 32a).
Mineral deposit model number 32a
Age of mineralization Host unit is Late-Ordovician based on fossils (Dutro and Patton, 1982). Age of mineralization is not known.
Alteration of deposit Secondary dolomite.

Production and reserves

Workings or exploration The Atoll prospect was discovered by WGM Inc. and Patino Ltd. during exploration for base metals in the late 1970s on lands selected by Doyon Ltd. (Andrews and Rishel, 1982). A large composite, chip-channel sample of 50 samples taken across the mineralized zone averaged 1.0 percent zinc and 395 ppm lead. A high-graded sample of 10 pieces of mineralized float yielded 7.95 percent zinc but no lead. A strong zinc soil anomaly (1,900 to 4,000 ppm) covers a 1,000 feet by 4,00 feet (300 m by 122 m) area below the Atoll prospect.
Indication of production None
Reserve estimates None.

Additional comments

See Reef Ridge (MD055), Midway (MD046), Beaver Creek (MD048) ,and other Mississippi Valley Type prospects in Medfra quadrangle. The Atoll prospect is on land selected or conveyed to Doyon Ltd. For further information, contact Doyon Ltd. at 210 1st Ave., Fairbanks, Alaska, 99701.

References

MRDS Number 10307797

References

Andrews, Tom, and Rishel, John, 1982, Annual Report for 1981, Reef Ridge I-to-XIII Project Areas, Kuskokwim Block, Alaska: Anchorage, Alaska, WGM Inc., Project Report 4, 45 p., 2 sheets, scales 1:63,360 and 1:20,000. (Report held by Doyon, Limited, Fairbanks, Alaska.)
Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.
Reporters Bundtzen, T.K. (Pacific Rim Geological Consulting)
Last report date 6/2/1998