|Quadrangle map, 1:250,000-scale||HE|
|Quadrangle map, 1:63,360-scale||A-1|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This site represents an area of placer gold mining on lower Valdez Creek and on adjacent parts of some of its tributaries. The map site is on the northbank of lower Valdez Creek, at the northeast end of the historic mining town of Denali. The site is in the SE1/4 of sec. 13, T. 20 S., R 1 E., of the Fairbanks Meridian. This location is accurate to within a quarter mile.|
The following description inpart duplicates, and in part supplements, the information in record HE194.
Valdez Creek drains an area underlain by pelitic metasedimentary rocks of probable Jurassic age, and several small intrusions of intermediate composition (Smith, 1981). The sedimentary sequence was regionally metamorphosed during the Cretaceous pumpellyite-prehnite grade on the southeast, through greenschist grade, to amphibolite grade on the northwest. The metamorphic sequence appears to be telescoped, possibly by northward-dipping thrust faults. An east-trending strike-slip fault zone south of, and sub-parallel to, Valdez Creek forms a distinct topographic break from upper Timberline Creek, across the upper end of Rusty and White creeks, and on eastward along the east-west portion of the Pass Creek drainage. This zone is important to the distribution of the origin of the placer gold because it has controlled the emplacement of several of the intermediate composition intrusions as well of as quartz vein swarms, some of which are auriferous. None of the northern tributaries of Valdez Creek are significant sources of placer gold.
The genesis and distribution of the placer gold deposits are also linked to the complex glacial history of the drainage. Near the lower end of the valley, at least three superimposed, gold-bearing paleochannels were cut into bedrock (Reger and Bundtzen, 1990), probably during valley deglaciation. From youngest to oldest, the paleochannels are designated Tammany paleochannel, A paleochannel, and B paleochannel. Portions of other paleochannels were also identified by drilling. Each paleochannel is at a specific elevation and gradient, and the younger paleochannels cut the older paleochannels, thereby redistributing and reconcentrating the gold. Gold concentrations are highest in the lowest portions of the paleochannels. The gravels and cobbles in these channels indicate that the channels were a very high energy depositional environment. The paleochannels served as natural giant sluiceboxes to concentrate the gold. The cracks and crevices in the bedrock in the bottom of the paleochannel also collected gold to depths of at least five feet below the bedrock surface (D.L. Stevens, personal observation).
The paleochannels become less incised upstream and eventually are not found. The pay streaks merge into a large volume of lower grade auriferous gravel from the upper limit of mining by Valdez Creek Mining Company, apparently up into the White Creek drainage, and in Valdez Creek upstream from White Creek. These auriferous gravels are fluvial and glacial in origin.The fineness of the gold runs about 852 with only minor variations. The gold itself showed several different varieties. Most of the gold is 'oatmeal' sized and shaped; other varieties include well-polished and rounded grains, rough, angular, and quartz-rich grains, and rough, angular, and oxide-coated grains.
|Geologic map unit||(-147.462259934057, 63.1795505947333)|
|Mineral deposit model||Placer Au-PGE (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||Paleochannel A is probably Sangamon in age, the Tammany channel is probably mid-Wisconsin in age, and Paleochannel B was probably deposited during the late Illinoian interstade (Reger and Bundtzen, 1990). The pay streaks and low-grade gravels in the White Creek drainage and Lucky Gulch are probably younger.|
|Workings or exploration||
Lower Valdez Creek was mined by hand methods after discovery in 1903. The Tammany Channel was mined by underground methods for a distance of about 3,500 feet from the confluence of the channel with Valdez Creek. The lower portion of the Tammany Channel was hydraulicked. The Dry Creek Cut was mined by hand methods and then by hydraulick methods.From 1984 through 1994, Channels A and B were mined by large-scale, open-pit methods for a distance of several miles upstream after have been thoroughly explored by reverse-circulation drilling. During this period, this mine was the largest placer mine in North America. The highest single year's production was nearly 102,000 ounces of gold.
|Indication of production||Yes; large|
|Reserve estimates||The large volume of low-grade material upstream from the upper limit of mining by Valdez Creek Mining Company has been extensively drilled, but is not economic to mine at this time (1999). No definitive efforts have been made to classify this large resource.|
|Production notes||Recorded production for all of Valdez Creek exceeds 600,000 ounces.|
Mendenhall, W.C., 1905, Geology of the central Copper River region, Alaska: U.S. Geological Survey Professional Paper 41, 133 p., 4 sheets, scale 1:250,000.
Moffit, F.H., 1909, Mining in the Kotsina-Chitina, Chistochina, and Valdez Creek regions: U.S. Geological Survey Bulletin 379-D, p. 153-160.
Moffit, F.H., 1912, Headwater regions of Gulkana and Susitna Rivers, Alaska, with accounts of the Valdez Creek and Chistochina placer districts: U.S. Geological Survey Bulletin 498, 82 p.
Moffit, F.H., 1914, Preliminary report on the Broad Pass region: U.S. Geological Survey Bulletin 592-H, p. 301-305.
Reger, R.D., and Bundtzen, T.K., 1990, Multiple glaciation and gold-placer formation, Valdez Creek Valley, western Clearwater Mountains, Alaska: Alaska Division of Geological & Geophysical Surveys Professional Report 107, 34 p., 1 sheet, scale 1:63,360.
Ross, C.P., 1933, The Valdez Creek mining district, Alaska: U.S. Geological Survey Bulletin 849-H, p.425-468.
Smith, T.E., 1971, Geology, economic geochemistry, and placer gold resources of the western Clearwater Mountains, east-central Alaska: Reno, University of Nevada, Ph.D. dissertation, 440 p.
Smith, T.E., 1981, Geology of the Clearwater Mountains, southcentral Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 60, 72 p., 3 sheets, scale 1:63,360.
Tuck, Ralph, 1938, The Valdez Creek mining district, Alaska, in 1936: U.S. Geological Survey Bulletin 897-B, p. 109-131.
Wiltse, M.A., 1988, Preliminary litho-geochemistry of Gold Hill and Lucky Hill, Valdez Creek mining district, Healy A-1 quadrangle, southcentral Alaska: Alaska Division of Geological and Geophysical Surveys Public-Data File 88-41, 9 p., 1 sheet, scale 1:12,000.
|Reporters||D.L. Stevens (Stevens Exploration Management Corporation)|
|Last report date||4/7/2000|