Bonanza Creek

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Ore minerals gold
Gangue minerals not applicable

Geographic location

Quadrangle map, 1:250,000-scale LC
Quadrangle map, 1:63,360-scale C-5
Latitude 60.717
Longitude -154.695
Nearby scientific data Find additional scientific data near this location
Location and accuracy Near intersection of Bonanza Creek and Little Bonanza Creek. Placer deposits extend from 'Gill's camp' at least 6 km upstream to above Cabin (or Cash) Creek and about 6 km downstream to Caribou Creek (Alaska Division of Mines and Minerals, 1961). This is locality 7 of Nelson and others (1985), localities 1 and 5 of MacKevett and Holloway (1977), and localities 1 and 6 of Cobb (1972). Locality of 'Gill's camp' accurate within 100 m.

Geologic setting

Geologic description

Bonanza Creek is both placer gold deposit and gold-quartz vein occurrence. Jasper (1961) reported: evidence indicates that glacial scouring was not an important erosional factor in this area, it is believed that pre-glacial alluvials were undisturbed, and that placer gold concentrations remain more or less as originally deposited along Bonanza Creek . The valley surface width varies from 300 to 700 feet with an average width of 400 feet. The valley alluvials are mostly uniform gravels with some boulders, interpreted as reworked glacial deposits. Stream gradient is 1 to 1.5 percent. The near-surface ground water level suggests a fairly loose gravel due to lack of sufficient sediment to 'tighten' the ground. Under these circumstances, the greater gold concentrations (if any) may be on or near bedrock (Jasper, 1961).
Bedrock is shale, argillite, and graywacke cut by porphyritic granitic dikes. The sediments strike N 40 to 45 E, and dip varies from 60 to 75 SW. Many quartz veins were noted by Jasper (1961) but only one was closely examined. The 12-foot-wide mineralized shear zone contains quartz veins with 5 to 6 percent pyrite, minor arsenopyrite, and some free gold. The shear zone stikes E, and dips 45 to 50 N. The shear zone extends 150 feet up slope. The quartz occurs in more or less continuous stringer from a few inches to 10 or 12 inches in width. One pan sample taken accross 18 inches of outcrop showed 3 fine gold colors. The sample was not crushed to free possible gold included in quartz fragments (Jasper, 1961).
Geologic map unit (-154.697258030216, 60.7163229279471)
Mineral deposit model Placer Au and Au-quartz veins or Polymetallic veins? (Cox and Singer, 1986; model 39a and 36a or 22c?)
Mineral deposit model number 39a, 36a, or 22c
Age of mineralization Quaternary.
Alteration of deposit Not applicable

Production and reserves

Workings or exploration
Brooks (1913) reported first encouraging prospects from benches of Bonanza Creek. By 1914, hand drills were in use to test placer ground in the Bonanza Creek drainage (Brooks, 1915; Jasper, 1961).
Jasper (1961) described the historic activity at Bonanza Creek: O.B. Millet was one of the original locators and spent 5 years prospecting his claims. He first sunk a 14 foot shaft which had to be abandoned because his hand pump could not handle the amount of water. Millet did not reach bedrock but he reported finding pay. He next got $400 (including nuggets up to $1.50 - with gold at $20.67/oz) from 100 cubic yards of material from a narrow channel 80 feet above the 14 foot shaft. In the mid-1920s, Millet brought a 4-inch hand drill and a hand pump to test the valley alluvials. Six holes were drilled - three holes 6 miles below Gill camp and three holes 1.75 miles below Gill camp. The gold values were too low to warrant a mining operation. During the 1930s, a 4-inch drill was brought to the area overland from Nondalton. Enroute several holes were drilled on Dummy and Chilikadrotna Creeks with discouraging results. No holes were put down on Bonanza Creek due to lack of funds and the venture was abandoned.
Cobb (1973) indicated that there has been extensive prospecting, but total production, including from tributaries, was less than 150 oz. The valley might be capable of supporting a small dredge or a dragline operation.
Indication of production Yes; small
Reserve estimates The near-surface ground water level suggests a fairly loose gravel due to lack of sufficient sediment to 'tighten' the ground. Under these circumstances, the greater gold concentrations (if any) may be on or near bedrock. However, Millet reported finding 'fair' pay in his 14-foot shaft; this makes it a reasonable expectation that appreciable gold values may be found at a number of horizons from surface to bedrock (Jasper, 1961).
Production notes Principal site of prospecting in Mulchatna basin; total gold production since 1912 of the area probably less than 3,000 oz (Nelson and others, 1985).

References

MRDS Number A013003

References

Reporters M.L. Miller (USGS); D.P. Bickerstaff (USGS)
Last report date 6/15/1998