Cache Creek Area, including Spruce Creek

Mine, Undetermined

Alternative names

Short Creek
Rambler Creek
Lucky Creek
Pineo Bar
Bradley
Cache Creek Dredging Company
Cache Creek Mining Company
Erickson
Gold
Ltd.
Morgan
Murray
Murray And Harper
Obermiller And Eaglehorn
Peterson
Taraski
Tesmer And Beidermann
Wetherall
Yenta Dredging Co.

Commodities and mineralogy

Main commodities Au
Other commodities As; Pt; Sn; Th; U; W
Ore minerals arsenopyrite; cassiterite; copper; gold; ilmenite; magnetite; platinoids; platinum; pyrite; scheelite; uranothorianite
Gangue minerals garnet; monazite; quartz; rutile; zircon

Geographic location

Quadrangle map, 1:250,000-scale TL
Quadrangle map, 1:63,360-scale B-2
Latitude 62.49
Longitude -150.984
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The Cache Creek area, in the Yentna District, is a productive placer area covering approximately 50 square miles, including streams draining the northwest flank of Peters Hills and the southeast flank of Dutch Hills, as well as tributaries to Cache Creek.
Reference coordinates are the approximate center of the most productive area on Cache Creek in the northwest quarter of Section 29, T. 28 N., R. 9 W., of the Seward Meridian. Dredging operations mined stream placers from Windy Creek to Nugget Creek, tributaries to Cache Creek. Mining claims extend, or have extended, from the headwaters to below Spruce Creek (C.C. Hawley and Associates, Inc., 1978, Fig. 4.2-B(3)).

Geologic setting

Geologic description

The Cache Creek area is a productive placer area in the Yentna District encompassing approximately 50 square miles including streams draining the northwest flank of Peters Hills and the southeast flank of Dutch Hills, as well as tributaries to Cache Creek. Dredging operations mined stream placers from Windy Creek to Nugget Creek, tributaries to Cache Creek. Mining claims extend, or have extended, from the headwaters to below Spruce Creek (C.C. Hawley and Associates, Inc., 1978, Fig. 4.2-B(3)).
Collectively the placer mines in the Yentna district have produced over 3.58 million grams of gold from 1906 to the present (Cobb and Reed, 1980; Nokleberg and others, 1994) with most of the area's production from dredging on Cache and Peters Creeks. The largest operation used two floating dredges supported by three backhoes.
This huge region contains many placer prospects and mines in Pleistocene stream and bench deposits of well-washed gravels derived from glacial debris, transitional with deposits of glaciofluvial origin (Clark and Hawley, 1968). Pleistocene sediments are deposited on Mesozoic marine slates and graywackes (KJs), although areas underlain by continentally derived Tertiary sediments of the Kenai group also occur (Reed and Nelson, 1980). Mesozoic rocks are cut by small granite bodies, diabase, and felsic dikes presumed to be early Tertiary in age (Clark and Hawley, 1968; Reed and Nelson, 1980).
C.C. Hawley and Associates, Inc. (1978) describe shallow stream gravels, 3 to 10 feet deep, average 4.5 feet, with well-defined, discontinuous pay streaks 150 to 300 feet wide and bench placers 7 to 35 feet deep with gold throughout, but mostly concentrated on bedrock of Mesozoic graywacke and argillite.
Cobb and Reed (1980) report arsenopyrite, cassiterite, copper, ilmenite, magnetite, unknown platinoids, platinum, pyrite, scheelite, uranothorianite, garnet, monazite, rutile, quartz, and zircon in the concentrates. Grades in the more productive parts of pay streaks mined during productive periods were $2 to $3 per bedrock foot or $1.50 per cubic yard when gold was valued at $20.67 an ounce (Capps, 1913, p. 57). In 1919 Martin (p. 247) reported platinum contents equal to about 0.003% of gold by weight. Concentrate samples contain 0.07 percent U and 0.035 percent ThO2 with eU content of 0.19 percent (Robinson and others, 1955, p. 2). The average fineness of the gold from Cache Creek is 866, with a range of 850.75 to 871 (Smith, 1941; Clark and Hawley ,1968).
In their 1978 report C.C. Hawley and Associates, Inc. indicate that probably more than half of the gold in Cache Creek has been mined. Ground down to about 10 cents per bedrock foot has been mined profitably in both Cache and lower Falls Creek in the 1970s.
This record refers to the Cache Creek region generally, and encompasses many specific occurrences and former producers. Mining claims on Cache Creek extend, or have extended, from its headwaters to below Spruce Creek. Placer mining took place on the following secondary drainages to Cache Creek: Spruce Creek, Dollar Creek, Windy Creek, Short Creek, Cheechako Gulch, Falls Creek, Thunder Creek, Rambler Creek, Lucky Creek, Nugget Creek, and Gold Creek (C.C. Hawley and Associates, Inc., 1978, Fig. 4.2-B(3)).
Geologic map unit (-150.98628377593, 62.4894771658019)
Mineral deposit model Placer Au-PGE (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Pleistocene and Tertiary (?) (Clark and Hawley, 1968).

Production and reserves

Workings or exploration Sluice box-CAT or dredge methods for almost 10 miles. Large volume, low grade and the overall coarseness of the gold favor large-scale, high capacity operations such as dredging (C.C. Hawley and Associates, Inc., 1978).
Indication of production Yes
Reserve estimates C.C. Hawley and Associates, Inc. (1978) indicate that probably more than half of the gold in Cache Creek has been mined.
Production notes
Large volume, low grade and the overall coarseness of the gold favor large-scale, high capacity operations such as dredging. Most of area's production from dredging on Cache & Peters Creeks. Ground down to about 10 cents per bedrock foot has been mined profitably in both Cache and lower Falls Creek in the 1970s (C.C. Hawley and Associates, Inc., 1978.
Grades in the more productive parts of pay streaks mined during productive periods were $2 to $3 per bedrock foot or $1.50 per cubic yard when gold was valued at $20.67 an ounce (Capps, 1913, p. 57). Platinum content is equal to about 0.003% of gold by weight (Martin, 1919, p. 247). Concentrate sample contained 0.07% U and 0.035% ThO2 with eU content of 0.119% (Robinson and others, 1955, p.2). Clark and Hawley (1968) report the average fineness of the gold from Cache Creek is 866, with a range of 850.75 to 871.

Additional comments

This record refers to the Cache Creek region generally, and encompasses many specific occurrences and former producers.

References

MRDS Number A010730; A011580; M045401

References

Nokleberg, W.J., and (seven) others, 1994, Metallogeny and major mineral deposits of Alaska and Metallogenic map of significant metalliferous lode deposits and placer districts of Alaska, in Plafker, G. and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol.. G1, p. 855-904, Plate 11, scale 1:2,500,000.
Reporters Madelyn A. Millholland (Millholland & Associates)
Last report date 8/10/1998