|Quadrangle map, 1:250,000-scale||BN|
|Quadrangle map, 1:63,360-scale||A-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Ophir Creek is a north tributary to Niukluk River. Its headwaters are along the south flank of the Bendeleben Mountains, just west of the terminal moraine complex of the Pargon River valley. It flows south and crosses from the Bendeleben to the Solomon quadrangle about 6 miles upstream from its mouth. The entire creek -- channel, flood plain, and benches -- has been placer mined downstream from the mouth of Crooked Creek. The main part of Ophir Creek in the Bendeleben quadrangle that has been placer mined is the 7,500 feet downstream from the mouth of Crooked Creek. This is locality 78 and 79 of Cobb (1972; MF 417; 1975; OFR 75-429).|
Geologic descriptionOphir Creek is the most important producer of placer gold in the Council district. The majority of the 707,000 ounces of gold production recorded for the Council district probably came from Ophir Creek (Hudson and DeYoung, 1978). Placer gold was discovered here in 1897 and extensive mining, especially dredging, has taken place over its entire length downstream from the mouth of Crooked Creek (Cobb, 1975). Dredging of the entire floodplain, in places almost 1,000 feet wide, took place along the 7,500 feet of the drainage downstream from Crooked Creek. Benches have been mined here and there along the drainage and at the mouth of Crooked Creek. Terrace gravels at the mouth of Crooked Creek were 5 to 6 feet deep and covered by 2 to 3 feet of overburden. The pay streak at the mouth of Crooked Creek was 250 feet wide, 6 feet thick, and contained 0.22 ounces Au per cubic yard (Smith and Eakin, 1911). Below Crooked Creek , Ophir Creek is at elevations less than 250 feet. This low elevation suggest the possiblity that the character of Ophir Creek placer deposits was influenced by Quaternary sea level fluctuations. The presence of terrace gravels and bench placer deposits indicates that two or more cycles of placer deposit development have occurred. However, there are gold-bearing localities in Lower Paleozoic metasedimentary bedrock (schist and marble; Till and others, 1986) near the mouth of Ophir Creek (Smith and Eakin, 1911), the mouth of Crooked Creek (BN100), and the headwaters of Crooked Creek (BN104). Gold-bearing bedrock is most commonly described as areas with small quartz or quartz-carbonate veins in schist or schistose limestone.
|Geologic map unit||(-163.664622963284, 64.9992746084591)|
|Mineral deposit model||Placer Au-PGE (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||Quaternary; the presence of terrace gravels and bench placer deposits indicates that two or more cycles of placer formation have occurred. Below Crooked Creek, Ophir Creek is at elevations less than 250 feet. This low elevation proximal to the Niukluk River coastal area suggest the possiblity that Quaternary sea level fluctuations influenced the character of Ophir Creek placer deposits.|
|Workings or exploration||Dredging of the entire floodplain, in places almost 1,000 feet wide, took place over the 7,500 feet of the drainage downstream from Crooked Creek. Benches have been mined here and there along the drainage and at the mouth of Crooked Creek. Some dredging took place as recently as the 1980s.|
|Indication of production||Yes; medium|
|Production notes||The majority of the 707,000 ounces of gold production recorded for the Council district (Hudson and DeYoung, 1978) probably came from Ophir Creek. About 50,000 ounces ($1,000,000) were estimated to have been produced in 1901 alone (Brooks, 1903).|
Brooks, A.H., 1903, Placer gold mining in Alaska in 1902: U.S. Geological Survey Bulletin 213, p. 41-48.
Cobb, E.H., 1972, Metallic mineral resources map of the Bendeleben quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-417, 1 sheet, scale 1:250,000.
Cobb, E.H., 1975, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Bendeleben quadrangle, Alaska: U.S. Geological Survey Open-File Report 75-429, 123 p.
Hudson, T.L., and DeYoung, J. H., Jr., 1978, Map and tables describing areas of mineral resource potential, Seward Peninsula, Alaska: U.S. Geological Suvey Open-File Report 78-1-C, 62 p., 1 sheet, scale 1:1,000,000.
Smith, P.S., and Eakin, H.M., 1911, A geologic reconnaissance in southeastern Seward Peninsula, and the Norton Bay-Nulato region, Alaska: U.S. Geological Survey Bulletin 449, 146 p.
|Reporters||Travis L. Hudson (Applied Geology)|
|Last report date||3/15/1999|