|Quadrangle map, 1:250,000-scale||BD|
|Quadrangle map, 1:63,360-scale||B-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||This placer deposit is near the middle of a creek that is not named on the USGS topographic maps but has been known locally and in mining literature since at least 1905 as First Chance Creek. It is about 9.9 miles north-northwest of Richardson on the Richardson Highway. It is about 2.4 miles northeast of the junction of Redmond Creek and Shamrock Creek, and about 0.6 mile northwest of the center of section 1, T. 6 S., R. 6 E., of the Fairbanks Meridian. The location is accurate.|
The Richardson District is characterized by gentle slopes and broad, alluvium-filled valleys (Prindle and Katz, 1913). The area is unglaciated and largely overlain by windblown silt, sand, and loess, locally up to 50 meters thick (Foster and others, 1979). The rocks consist of three structure-bounded units (Weber and others, 1978; Swainbank and others, 1984; Noyes and others, 2006; Freeman, 2011). There is a core that consists mainly of biotite-hornblende-feldspar-quartz gneiss and lesser amphibolite, quartzite, marble and calc-silicate hornfels. The core is bounded on the north and south by amphibolite-grade pelitic schist. The contacts between the units are probably low-angle faults; north-trending vertical faults occur widely. Weber and others (1978) assign the pre-metamorphic age of the rocks to the Precambrian or Paleozoic. They were metamorphosed in the Middle to Late Devonian and recrystallized in the Early Cretaceous (Dusel-Bacon and others, 2004; Freeman, 2011). The metamorphic rocks are intruded by 90 Ma, felsic to intermediate dikes and plugs, notable the quartz-feldspar porphyry dike at the nearby Democrat Mine (BD014).
Olson and others (1985) report mining on First Chance Creek in 1905 but there is little hard evidence of mining in subsequent years. Based on an old newspaper article, Mitchell (1989) noted that prospecting on First Chance Creek at some uncertain time found auriferous gravel with 0.25 ounce of gold per pan at a depth of 80 feet. Mitchell located old dumps next to by shafts on First Chance Creek but they were too small to indicate significant production. A 1906 newspaper article reported as much as 5 ounces of gold per cubic yard from from gravel in shafts 40 to 90 feet deep on First Chance Creek; the gold was said to be accompanied by cassiterite, cinnabar, scheelite, and molybdenite. Freeman (2011) questions that location and there is no documentation of the amount of gold produced from First Chance Creek from 1905 to 2011.
In 2003, the Tri-Valley Corporation drilled 44 reverse-circulation holes on the placer in lower First Chance Creek. The holes averaged 18.6 meters deep and the deepest was 28.5 meters (Vardanyan and others, 2003; Freeman, 2011). The drilling indicated a 60-meter-wide zone of old drift mining on the lower part of First Chance Creek that verifies that there was some early mining. Samples collected in 1999 by Placer Dome (USA) and by TSNIGRI working with the Tri-Valley Corporation found visible gold 0.1 to 3.0 millimeters in size as well as cassiterite, scheelite, cinnabar, and molybdenite in the heavy sand fraction.The 2003 drilling defined two pay streaks that extend for more than 3 kilometers along the creek. An upper auriferous channel was covered by aeolian silt; the lower auriferous channel was on bedrock The gravel in the upper channel was about 2.8 meters thick beneath 4.6 meters of overburden; the gravel averaged 0.38 gram of gold per cubic meter. The gravel in the lower channel was about 2.6 meters thick under about 16.8 meters of overburden; the gravel averaged 0.86 gram of gold per cubic meter. Vartanyan and others (2003) estimated that lower First Chance Creek has a total resource of 37,871 ounces of gold in 1,661,000 cubic yards of gravel overlain by 7,100,000 yards of overburden.
|Geologic map unit||(-146.483267274081, 64.4264889848877)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a).|
|Mineral deposit model number||39a|
|Age of mineralization||Quaternary.|
|Workings or exploration||There are indications of mining in 1905 and perhaps for a few more years but little evidence of when and how much gold was produced. Placer drilling in 2003 identified a 60-meter-wide zone of old drift mining on the lower part of First Chance Creek that verifies that there was some early mining. In 2003, the Tri-Valley Corporation drilled 44 reverse-circulation holes on lower First Chance Creek that identified a measurable placer gold resource.|
|Indication of production||Yes; small|
|Reserve estimates||As defined by 44 holes drilled in 2003, Vartanyan and others (2003) estimated that lower First Chance Creek has a total resource of 37,871 ounces of gold in two channels of auriferous gravel that total 1,661,000 cubic yards of material. The auriferous gravel is overlain by 7,100,000 yards of overburden.|
|Production notes||There is no documentation of placer production on First Chance Creek, but there was mining at least in 1905. Drilling in 2003 identified a 60-meter-wide zone of old drift mining of uncertain age but may date to before WWI.|
Dusel-Bacon, C., Wooden, J.L. and Layer, P.W., 2004, A Cretaceous Ion-Microprobe U-Pb zircon Age for the West Point Orthogneiss: Evidence for another Gneiss Dome in the Yukon-Tanana Upland in Galloway, J.P., ed., 2004, Studies by the U.S. Geological Survey in Alaska, 2001: U.S. Geological Survey Professional Paper 1678, p. 41 - 60.
Foster, H. L.; Albert, N. R. D.; Griscom, A.; Hessin, T. D.; Menzie, W. D.; Turner, D. L. and Wilson, F. H., 1979, Alaskan Mineral Resource Assessment Program: Background Information to Accompany folio of Geologic and mineral resource maps of the Big Delta Quadrangle, Alaska: U.S. Geol. Survey. Circ. 783, 19 p.
Mitchell, J.R., 1989, Exploration update, Richardson prospect, Alaska: Internal report prepared for Tri-Valley Corporation, 22 p.
Olson, B.G., Burton, J., Wolff, E.N., and Swainbank, D., 1985, Mining and minerals in the golden heart of Alaska: Fairbanks North Star Borough Publication, 80 p.
Vartanyan, S. S., Volchkov, A. G., and Kutorgin, V., 2003, The First Chance Creek gold placer exploration project: Private report prepared for Tri-Valley Corporation, 24 p.
|Reporters||D.J. Grybeck (Contractor, USGS)|
|Last report date||4/1/2012|