Pioneer

Prospects, Active

Alternative names

Grubstake East

Commodities and mineralogy

Main commodities As; Au
Ore minerals arsenopyrite; gold

Geographic location

Quadrangle map, 1:250,000-scale CH
Quadrangle map, 1:63,360-scale C-3
Latitude 67.5562
Longitude -148.1442
Nearby scientific data Find additional scientific data near this location
Location and accuracy The several Pioneer prospects are centered about 0.1 mile southwest of Crystal Peak at an elevation of about 4,000 feet, about 0.2 mile northeast of the center of section 35, T. 32 N., R. 3 W. The location is accurate.

Geologic setting

Geologic description

Placer gold was discovered in the Chandalar area on Little Squaw Creek (CH039) in 1902 (Barker, and Bundtzen, 2004; Barker, 2007; Barker and others, 2009). By 1909, four quartz veins including the Mikado vein had been discovered and many more were located prior to WWI. Most of the important properties in the district were consolidated by William Sulzer from 1909 to 1941; the Mikado Mine was one of the prominent deposits of the Chandalar area and was included. Those properties were taken over in 1946 to form the Little Squaw Mining Company in 1959, which in turn became the Little Squaw Gold Mining Company in 1968. From 1967 to 1999, Little Squaw Gold Mining Company leased some of their Chandalar lode and placer ground for mining and/or exploration to a succession of companies, notably the Chandalar Gold Mining and Milling Company (1967-1971), Noranda Mining (1974-1976), the Chandalar Development Corporation (1980-1983), and Gold Dust Mines (1989-1999). There was some earlier small lode production from the district but the first documented gold produced from the lodes was 870 ounces produced from 1967 to 1971 from the Mikado and Summit mines by the Chandalar Gold Mining and Milling Company. Subsequently, Chandalar Development produced 8,169 ounces of lode gold from the Mikado and Summit Mines but recovery was poor. In 2003, Little Squaw Gold Mining Company and its direct descendent Goldrich Mining Company began an aggressive exploration program for lode and placer deposits over a large block of land that covers almost all of the known deposits in the Chandalar area and as of early 2010, that effort continued (Goldrich Mining Company, 2010).
The geology of the Chandalar area is dominated by a system of west-northwest-trending regional faults including a prominent thrust fault in the southern part of the district and a series of major high-angle faults through the center of the area (Bundtzen and Laird, 2009a, 2009b). These faults separate the rocks into two principal units, a west-northwest-trending Upper Plate unit about 3 miles wide in the center of the area and a Lower Plate unit to the north and south. The contact of the two units is a thrust fault on the south side of the Upper Plate rocks and a high-angle fault on the north side. Most of the Upper Plate rocks consist of Devonian upper-greenschist-facies metamorphic rocks, mainly carbonaceous schist; quartz-chlorite-muscovite schist, schist and phyllite derived from turbidites that comprise the Mikado Phyllite, metamorphosed calcareous sandstone, and quartz-muscovite schist. The Lower Plate rocks consist of Devonian, upper-greenschist-facies metamorphic rocks, mainly metamorphosed volcanic agglomerate, chlorite-rich tuffaceous schist, quartz-mica schist derived from mudstone, mica-quartz schist, and quartzite. Both the Upper and Lower Plate rocks are cut by irregular masses, dikes and sills of greenstone, metagabbro, and metadiorite of unknown age. Most of the mineral deposits in the Chandalar area are in the Upper Plate rocks and the deposits often are along the regional, steep-to-vertical, west-northwest-trending faults. There is an additional conjugate set of north-northeast-trending faults that offset the Upper Plate rocks and at least some of the mineralization may be localized at the intersections of the regional west-northwest-trending faults and the conjugate faults.
Several veins are exposed in trenches and pits on the ridge just southwest of Crystal Peak (Barker and Bundtzen, 2004; Barker, 2006, 2007; Barker and others, 2009). The veins are aligned along or a component of the Pioneer Fault zone which can be traced for almost 6 miles and is probably the most continuous structural feature in the Chandalar district; it trends about N65-75W. At least two veins are exposed in the Pioneer workings; they consist of discontinuous lenses of shattered quartz, sericite, and clay from a few inches to three feet thick, generally in the footwall of the Pioneer fault. The host rocks are quartz-muscovite schist of the Upper Plate unit. Float and outcrop samples contained up to 7.54 ounces of gold per ton (Strandberg, 1990). However, systematic channel samples across the veins assayed 0.02 to 2.523 ounces of gold per ton (Swanson and Ashworth, 1981).
The Pioneer fault continues northwest across Little Squaw Creek to the Grubstake East and Prospector East (CH111) prospects. The Grubstake East prospect is about 0.8 mile northwest of the Pioneer prospects in the valley of Little Squaw Creek. There is no outcrop at the Grubstake East prospect nor up the hillside to the Pioneer prospects. There is a small caved adit at the Grubstake East prospect and several prospect trenches. A single float sample of scorodite-stained quartz contained 5.18 parts per million gold.
The gold veins in the Chandalar district are considered mesothermal (Barker and others, 2004) by comparison similar deposits elsewhere and in consideration of fluid inclusion and oxygen and lead isotope studies of the Chandalar mineralization (Ashworth, 1983; Rose and others, 1988; Gacetta and Church, 1989).
Geologic map unit (-148.146934812719, 67.5558192251326)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Possibly Middle Cretaceous based on the assertion of Dillon (1982) that the gold-quartz veins of the central Brooks Range are that age. However, there is no definitive data for the age of the veins of the Chandalar area.
Alteration of deposit Not specifically noted.

Production and reserves

Workings or exploration The work includes trenches, several prospect pits, and considerable surface sampling and examination over many years in several episodes of work by industry. In early 2010, this is one of the sites that was being studied by Goldrich Mining Company during their intensive exploration of the Chandalar area.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Ashworth, K.K., 1983, Genesis of gold deposits at the Little Squaw mines, Chandalar mining district, Alaska: Bellingham, Western Washington University, M.Sc. thesis, 98 p.
Ashworth, (Lamal) Kate, 1984, Fluid inclusion study of the Eneveloe Vein, Chandalar Mining District: Private Report, Chandalar Development Associates, 8 pages (in files of the Goldrich Mining Company).
Barker, J.C., 2006, Chandalar Mining District, a report of findings and recommendations, 2005: Unpublished report for Little Squaw Gold Mining Company, 93 p. (on the Internet at http://www.goldrichmining.com/Files/corporate/2005AnnualReport011906.pdf, as of February 14, 2010)
Barker, J.C., 2007, Chandalar Mining District, Annual Report of findings for 2006; Unpublished report for Little Squaw Gold Mining Company, 124 p. (On the Internet at http://www.goldrichmining.com/Files/chandalar/chandalar_barker_rpt_2007.pdf, as of February 14, 2010).
Barker, J.C., and Bundtzen, T.K., 2004, Gold deposits of the Chandalar Mining District, Northern Alaska: An information review and recommendations: Unpublished report for the Little Squaw Gold Mining Company, 165 p. (in the files of the Goldrich Mining Company).
Barker, J.C., Murray, R.B., Keener, J.O., and Martin, P.L., 2009, Evaluation of the Chandalar mining property: Unpublished report prepared for Goldrich Mining Company, 165 p. (on the Internet at http://www.goldrichmining.com/Files/chandalar/Chandalar_tech_rept_4_15_09.pdf as of February 14, 2010
Goldrich Mining Company, 2010, Chandalar, Alaska; Project overview: http://www.goldrichmining.com/pages/prop_chan_over.htm (as of February 16, 2010).
Strandberg E.O. Jr., 1990, Description of Properties, Chandalar Mining District, Alaska: Unpublished company report, 143 p. 14 plates.
Reporters D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010