Yankee Boy

Prospect, Active

Alternative names

Yankee

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As
Ore minerals arsenopyrite; gold; pyrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale D-4
Latitude 58.829
Longitude -135.0017
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Yankee prospect is at an elevation of 570 feet,on the north valley wall of Johnson Creek. It is 1 mile northwest of Berners Bay, in the SW1/4 section 13, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

Note: Beginning in the 1990s, this and other old mines and prospects in the vicinity were consolidated by Coeur-Alaska into a single property (Birak, 2006). They have carried out major new drilling and underground exploration that better defines the mineralization, largely blurs the geologic distinction among the old deposits, and extends the ore bodies greatly. They have developed a coherent modern interpretation of the mineralization as a single deposit which Coeur-Alaska intends to mine as a unit. This deposit is described separately in ARDF as the Jualin (Coeur-Alaska) deposit (JU262). For geologic reference purposes and for their historic value, the pre-Coeur-Alaska data for this and the other old mines and prospects that Coeur-Alaska consolidated are retained in ARDF.
The Yankee Boy vein was discovered about 1911 and explored by a 136-foot adit and 4 open cuts (Redman and others, 1989). The Yankee Boy deposit consists of a single quartz vein in Jualin Diorite that is traceable for 3,000 feet northwest from the Yankee adit. The vein strikes N41W and dips steeply south. The thickness varies from a few inches to five feet and averages two feet. Roehm (1938) describes the vein as banded quartz with a darker, bluish core. The outer bands are nearly barren of sulfides and vary from milky white to glassy. Sulfide minerals are confined mainly to the central bluish band, which varies in width from a few inches to 18 inches but averages less than 12 inches. Pyrite and a little arsenopyrite are the only sulfides in the vein. The vein represents two generations of quartz: a milky white to glassy rim, and grayish blue core (Roehm, 1938). Roehm reports that samples of the vein contained up to 1.6 ounces of gold per ton and 1.0 ounce of silver per ton. In 1988, Curator International Resources Ltd. collected samples of the Yankee vein; one, two-foot chip sample assayed 1.35 ounces of gold per ton (Barnett, 1989).
Geologic map unit (-135.003506949918, 58.828674776851)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Hydrothermal muscovite from veins in the Jualin mine are 53.2 Ma to 55.5 Ma (Miller and others, 1994). This coincides with the 55 Ma age of the other mesothermal gold veins in the Juneau Gold Belt (Goldfarb and others, 1997).

Production and reserves

Workings or exploration The Yankee prospect was discovered about 1911 and explored by a 136-foot adit and 4 open cuts (Redman and others, 1989). Limited exploration was conducted by International Curator Resources Ltd. in 1988 (Barnett, 1989).
Indication of production None

References

References

Barnett, J.C., 1989, Jualin gold project, 1988 progress report, Berners Bay District: Unpublished report for International Curator Resources, Ltd., 75 p.
Birak, D.J., 2006, Kensington gold project: Unpublished Technical Report for Cour d'Alene Mines, 116 p. (posted on www/.sedar.com, April 20, 2006).
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Miller, L.D., Goldfarb, R.J., Snee, L.W., Gent, C.A., and Kirkham, R.A., 1995, Structural geology, age, and mechanisms of gold vein formation at the Kensington and Jualin deposits, Berners Bay district, southeast Alaska: Economic Geology, v. 90, p. 343-368.
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska ); D.J. Grybeck (Port Ludlow, WA)
Last report date 6/5/2008