|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||The Gold Run prospect is centered about 1.5 miles north-northeast of VABM 3026 'Buck'. It is about 8.0 miles north-northwest of Richardson on the Richardson Highway and about 0.7 mile northwest of the center of section 1. T. 6 S., R. 7 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).
The Gold Run prospect is associated with a coarse-grained, porphyritic quartz monzonite stock, the Gold Run intrusive (Swainbank and others, 1984; Rogers, 1999). The stock extends over an area about 1.8 by 2.3 kilometers in size. Only the top of the stock is exposed and the southern margin is bounded by a fault. The stock is rimmed by fine- to medium-grained equigranular granite, locally mixed with gneiss. Pegmatite dikes composed mainly of quartz, feldspar, muscovite, and biotite are common beyond the stock. Biotite from the stock has been dated as 92 Ma by Ar/Ar methods (Graham, 2002).Mineralization at the Gold Gun prospect was first suspected in 1991 from the presence of gold in rock and panned concentrate samples collected in a regional geochemical survey (Vartanyan and others, 1991). Placer Dome (USA) subsequently collected soil samples at the top of bedrock over the area on a 200-meter grid. That geochemical survey defined a bismuth anomaly about 0.5 kilometer wide by 1.2 kilometers long (Rogers and others, 1999). Rock samples contained from less than 5 to 40 parts per billion gold, and low arsenic and bismuth. Freeman (2011) suggests that the the prospect is an intrusion-related gold deposit.
|Geologic map unit||(-146.386565322041, 64.3996908914088)|
|Mineral deposit model||Intrusion-related gold.|
|Age of mineralization||Probably related to the 92 Ma stock that hosts the deposit.|
|Alteration of deposit||Not specifically noted.|
|Workings or exploration||Covered by geochemical surveys; the prospect has had only limited surface sampling and mapping.|
|Indication of production||None|
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.
Freeman, C.J., 2011, Geology and mineralization of the Richardson gold property, Richardson Mining District, Alaska: Geologic report for Select Resources Corp. Inc., http://tri-valleycorp.com/docs/NI_43-101_Report.pdf (as of February 24, 2012).
McCoy, D.T.; Newberry, R.J.; Layer, P., DiMarchi, J.; Bakke, A.; Masterman, J.S. and Minehane, D.L., 1997, Plutonic-related gold deposits of interior Alaska: in Economic Geology Monograph 9, p. 191-241.
Rogers, J. A., McCoy, D. T., Graham, G. and Nerup, M., 1999, Placer Dome-Tri-Valley Option Agreement, 1999 Annual Report, Richardson Project: Confidential Private Report, 46 p.
Vartanyan, S.S., Konstantinov, V.Y., Oreshin, V.Y., Rodionov, V.A., Pyatnitshy, V.A., Brovkin, V.A., Zagoskin, B.S. and Zelikson, B.S., 1991, Estimation of gold potential of the Richardson Mining District, Alaska: Internal TsNIGRI report to Tri-Valley Corporation, December, 1991, 40 p.
|Reporters||D.J. Grybeck (Contractor, USGS)|
|Last report date||4/1/2012|