Dennison Fork

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities W
Ore minerals gold; scheelite

Geographic location

Quadrangle map, 1:250,000-scale EA
Quadrangle map, 1:63,360-scale A-2
Latitude 64.0537
Longitude -141.9113
Nearby scientific data Find additional scientific data near this location
Location and accuracy Dennison Fork is a tributary of the South Fork of the Fortymile River; its mouth is about 1.6 miles south-southeast of Chicken. Prospecting and drilling took place near the confluence of Dennison Fork with Mosquito Fork and South Fork. The coordinates are an arbitrarily point near the mouth of Dennison Fork,in section 8, T. 26 N., R. 18 E., of the Copper River Meridian. This site is locality 84 of Burleigh and Lear (1994), locality 21 of Eberlein and others (1977), and locality 53 of Cobb (1972 [MF-393]).

Geologic setting

Geologic description

The rocks in the lower part of the Dennison Fork valley consist predominantly of the Triassic granodiorite of the Taylor Mountain batholith (Foster, 1976). A rubidium/strontium date on biotite from granodiorite of the batholith gives an age of approximately 190 Ma (Wasserberg and others, 1963). The granodiorite has been intruded by minor Tertiary gabbro. Quaternary alluvium, colluvium, and terrace deposits are extensive in the Dennison Fork drainage.
Considerable prospecting and drilling has been carried out near the mouth of Dennison Fork, but there is no record of actual placer mining. A ditch was dug in 1911 to work the bench gravels (Porter, 1912); despite completion of the ditch, no mining occurred (Ellsworth and Davenport, 1913). Gold near the mouth of Dennison Fork is very fine grained. In 1918, there was extensive prospecting of high benches near the mouth of Dennison Fork ,and plans were made to build a 21-mile-long ditch (Martin, 1920). Additional systematic prospecting of a large body of gravel occurred in 1920 (Brooks, 1922). A sample from the foot of the bluff at the junction of Dennison and Mosquito Forks contained trace scheelite (White and others, 1963).
Geologic map unit (-141.913577991553, 64.0533723892271)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Quaternary.

Production and reserves

Workings or exploration Considerable prospecting and drilling has been carried out near the mouth of Dennison Fork, but there is no record of actual placer mining. A ditch was dug in 1911 to work the bench gravels (Porter, 1912); despite completion of the ditch, no mining occurred (Ellsworth and Davenport, 1913). Gold near the mouth of Dennison Fork is very fine grained. In 1918, there was extensive prospecting of high benches near the mouth of Dennison Fork ,and plans were made to build a 21-mile-long ditch (Martin, 1920). Additional systematic prospecting of a large body of gravel occurred in 1920 (Brooks, 1922). A sample from the foot of the bluff at the junction of Dennison and Mosquito Forks contained trace scheelite (White and others, 1963).
Indication of production None

References

MRDS Number A015158

References

Wasserberg, G.J., Eberlein, G.D., and Lanphere, M.A., 1963, Age of Birch Creek Schist and some batholithic intrusion in Alaska [abs.]: Geological Society of America Special Paper 73, p. 258-259.
Reporters M.B. Werdon
Last report date 5/1/2002