Johnson

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As
Ore minerals arsenopyrite; gold; pyrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale C-7
Latitude 60.6279
Longitude -149.5515
Nearby scientific data Find additional scientific data near this location
Location and accuracy The prospect is located in the NW1/4 section 12, T. 6 N., R. 2 W., of the Seward Meridian, at elevations between 2.600 and 4,300 feet. The prospect is situated on the north side of Summit Creek, one mile west of the Seward Highway. The prospect is about 0.75 mile west of its indicated position (Johnson Mine) on the 1994 U.S. Geological Survey Seward C-7 topographic map. This location is accurate to within 300 feet. This is location 30 of Cobb and Richter (1972), location 35 of MacKevett and Holloway (1977), location 50 of Cobb and Tysdal (1980), and location S-258 of Jansons and others (1984).

Geologic setting

Geologic description

The deposit at the Johnson prospect consists of quartz-calcite stringers that heal fractures in a 4- to 8-foot-wide felsic dike. The stringers are 4 to 6 inches wide and contain sparse arsenopyrite and pyrite and a little gold. The dike is apparently an extension of the Gilpatrick dike of Eocene age, which at this site strikes N12E and dips vertically. The dike intrudes Valdez Group rocks of Late Cretaceous age (Cobb and Tysdal, 1980).
Geologic map unit (-149.553648871838, 60.6273252281231)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Eocene or younger; the veins are in an Eocene dike.

Production and reserves

Workings or exploration
Workings consist of a 40-foot adit at an elevation of 2,800 feet and open cuts at 3,500 feet and 4,300 feet (Tuck, 1933). In the 1930s, a half-mile-long trail led to the workings from the Oracle mine (SR142).
A sample collected in the 40-foot adit across a 4.5-foot width assayed at 0.03 ounce of gold and 0.1 ounce of silver per ton (Tuck, 1933).
Indication of production None

References

MRDS Number A010418

References

Hoekzema, R.P., and Sherman, G.E., 1983, Mineral investigations in the Chugach National Forest, Alaska (Peninsula study area): U.S. Bureau of Mines in-house report; held at U.S. Bureau of Land Management Alaska State Office, Anchorage, 524 p.
Reporters Jeff A. Huber (Anchorage)
Last report date 1/12/2000