Goss Gulch

Prospect, Active

Commodities and mineralogy

Main commodities Au; Sb
Other commodities Ag; As
Ore minerals arsenopyrite; pyrite; stibnite
Gangue minerals biotite; quartz

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale D-1
Latitude 62.98582
Longitude -156.36256
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Goss Gulch prospect is on a high level terrace at an elevation of 1,500 feet, about 1.5 kilometers southeast of the Yankee Creek 'placer mine' shown on the USGS 1:63,360-scale topographic The prospect is about 0.4 mile west of the northeast corner of section 6, T. 33N., R. 37W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

The Goss Gulch prospect is in a mineralized quartz-feldspar dike or sill that intrudes sandstone and shale of the Upper Cretaceous Kuskokwim Group and chert of the Late Paleozoic to Mesozoic, Innoko Terrane (Bundtzen and Laird, 1983; Miller and Bundtzen, 1994). The mineralized intrusion is about 160 feet thick. A 800-foot -thick, fine-grained, biotite quartz monzonite sill cuts the sediments about 650 feet southeast of southeast of Goss Gulch. This intrusion has a 40Ar/39Ar age of 71.3 Ma (Bundtzen, unpublished data, 1999). The Goss Gulch prospect lies directly over the trace of the Ganes-Yankee Creek fault zone (Bundtzen and Miller, 1997).
At the prospect, fault-controlled lensoid veins of nearly pure stibnite from 0.4 to 8 inches thick can be traced in rubble crop for 100 feet. The veins are oriented in two planes. One has a strike of N 70 E and a vertical dip; the other strikes N 10-15 E strike and dips 80 SE. Samples of the vein contained as much as 35.0 percent antimony, 2.40 parts per million (ppm) gold, and 1,500 ppm arsenic (Bundtzen and others, 2000). Despite the conspicuous presence of stibnite, the correlation coefficient between gold and antimony is only 44; the coefficient between gold and arsenic is about 92 (Bundtzen and others, 2000; T.K. Bundtzen, unpublished data, 2002).
In 2001, two reconnaissance diamond drill holes totaling 1,214 feet were completed at the prospect (EMEX Corporation press release, February 14, 2002). Drill Hole GG01-01 did not penetrate significant mineralization. Drill hole GG-01-02 intersected three auriferous zones. Core from 277.6 to 279.9 feet contained 1,045 parts per billion (ppb) gold, 2,020 parts per million (ppb) arsenic, and 55 ppm antimony; core from 282.5 to 285.4 feet contained 750 ppb gold, 2,180 ppm arsenic, and 75 ppm antimony; and core from 650.0 to 665.0 feet contained 4,100 ppb gold, 1,000 ppb silver, 220 ppm arsenic, and 60 ppm antimony. The upper auriferous intercepts are in dike rock; the lower gold-bearing intercept is at the contact between quartz porphyry and quartz-veined sedimentary rocks.
Geologic map unit (-156.364920813386, 62.9851878477171)
Mineral deposit model Low sulfide gold-quartz vein or Simple antimony vein; (Cox and Singer, 1986; models 36a and 27d); or the peraluminous granite porphyry gold-polymetallic type deposit of Bundtzen and Miller (1997).
Mineral deposit model number 36a or 27d
Age of mineralization Quartz monzonite on nearby French Joe Mountain (ID040) has a 40Ar/39Ar age of 71.3 Ma (T.K. Bundtzen, unpublished data, 1999).
Alteration of deposit Phyllic alteration in sedimentary rocks; potassic alteration with secondary biotite in quartz monzonite.

Production and reserves

Workings or exploration The prospect was discovered in 1998 during a soil and rock-chip geochemical survey for North Star Exploration, Inc. on land optioned from Doyon Limited (Hinderman and others, 1999). In 2001, two reconnaissance diamond drill holes totaling 1,214 feet were completed at the prospect (Galey and others, 2002; EMEX Corporation press release, February 14, 2002).
Indication of production None



Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Bundtzen, T.K., Bouley, B.A., Noyes, H.J., and Nokleberg, W.J., 2000, Regional metallogenesis of central Alaska: Society of Mining, Metallurgy, and Exploration Annual Meeting, Salt Lake City, Utah, February 28-March 1, 2000, p.1-29.
Galey, J., Retherford, R., Ellis, W., Harris, R., Deane, S., and Hinderman, T., 2002, 2001 Annual report, Takotna village block: Lakewood, Colorado, North Star Exploration, Inc., AR-01-Takotna, to Doyon Limited: 29 p. 9 sheets and 4 appendices.
Hinderman, T., Retherford, R., Bull, K.F., Vanderpool, T., and Bundtzen, T.K., 1999, 1998 annual report, Takotna village block: Lakewood, Colorado, North Star Exploration, Inc., AR-98-Takotna, to Doyon Limited, 57 pages, 4 sheets and 3 appendices.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date 5/16/2003