Unnamed (near Bonanza Creek)

Prospect, Inactive

Alternative names

Downing

Commodities and mineralogy

Main commodities Au
Ore minerals arsenopyrite; gold
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale D-7
Latitude 60.8208
Longitude -149.5115
Nearby scientific data Find additional scientific data near this location
Location and accuracy This record describes an unnamed prospect in the Downing mine area (see additional comments). The map site is at an elevation of 2,700 feet, on the north valley wall of upper Bonanza Creek. It is in the SE1/4 section 31, T. 9 N., R. 1 W., of the Seward Meridian. The unnamed prospect is located east of the Francisco (SR017), Bonanza (SR018), and Whistler (SR020) prospects (also called Downing mine). This is location 18 of Cobb and Tysdal (1980). This location is accurate to within a quarter of a mile.

Geologic setting

Geologic description

The deposit at this prospect consists of auriferous, arsenopyrite-bearing quartz-calcite veins that heal fractures in a 5-foot-wide, Eocene(?) felsic dike locally called the Kenai Star dike. The dike strikes N30E and dips 45-60E (Tuck, 1933) and intrudes slate and sandstone of the Valdez Group of Late Cretaceous age (Nelson and others, 1985). Sericitic alteration envelopes, 0.4 to 0.8 inch wide, surround tiny fractures cutting the slate and sandstone country rock, but there is little alteration near the larger quartz veins in the dike (Mitchell, 1979).
Hoekzema and Sherman (1983) refer to this prospect briefly under the name Downing mine (SR017), as a fractured dike occurs nearby.
Geologic map unit (-149.513662762867, 60.8202313024007)
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 heal fractures in the dike.
Alteration of deposit Sericitic alteration envelopes 0.4 to 0.8 inch wide surround tiny fractures cutting slate and sandstone country rock, but little alteration is present near the larger quartz veins in the dike (Mitchell, 1979).

Production and reserves

Workings or exploration Tuck (1933) reported a 20-foot adit that exposed a 3-foot width of dike containing about 2 percent quartz veinlets carrying a small amount of arsenopyrite. A sample across the face contained only a trace of gold (Tuck, 1933). Mitchell (1979) visited the property in 1977 and reported 69 feet of workings. The U.S. Bureau of Mines visited the nearby Downing mine in 1982, but did not sample the prospect described in this record (Hoekzema and Sherman, 1983). Tuck (1933) wrote that nowhere on the Kenai Star dike was there observed anything that might be considered ore.
Indication of production Undetermined
Production notes The U.S. Bureau of Mines reported production of 150 ounces of gold from the Downing mine, which presumably included any production from the Francisco, Bonanza, and Whistler properties (Jansons and others, 1984). None of the production is believed to have come from the prospect described in this record.

Additional comments

In his description of this deposit, Tuck (1933) included references to the Francisco (SR017), Whistler (SR020), and Bonanza (SR018) properties on Bonanza Creek. This unnamed prospect is east of those properties that are collectively known as the Downing mine (Jansons and others, 1984).

References

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.
Mitchell, P.A., 1979, Geology of the Hope-Sunrise (gold) mining district, north-central Kenai Peninsula, Alaska: Stanford University Master of Science thesis, 123 p.
Reporters Jeff A. Huber (Anchorage)
Last report date 2/20/2000