Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; As; Bi; Cu; Hg; Pb; Sb; Sn
Ore minerals arsenopyrite; gray sulfosalts
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale D-7
Latitude 61.76865
Longitude -158.49664
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on a isolated knob between two small lakes at the head of Getmuna Creek in the northern Horn Mountains. The prospect is at an elevation of about 2,400 feet near the center of the NE1/4 sec. 3, T. 19 N., R. 51 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

The Getmuna Creek prospect consists of two 2- to 4-inches-thick auriferous, quartz-arsenopyrite-sulfosalt veins in quartz syenite of the Horn Mountains pluton. The veins strike about N20W discontinuously for 1,300 feet across the upper glaciated valley of Getmuna Creek. Rubble exposures indicate the dip is steep to vertical. Mineralized zones, where identifiable in rubble are indicated by Fe-oxide, scorodite stains, and quartz vein float. Poor exposures generally prevent an accurate estimate of the size, extent, and grade of the auriferous veins, and the available data suggests that the veins are small and of limited extent. The wall rock on either side of the veins have thin potassic alteration rims about 8 inches thick, but the host rocks otherwise are not altered. The Getmuna Creek prospect is parallel to the mineralized structure exposed at the Saddle prospect (SM003).
Two exposures of the vein were sampled. The northwest zone is on the knob at the coordinates above. The southeast zone is in rubble-crop along the eastern side of the valley near the cirque headwall and about about 1,200 feet from the northwest zone. Four chip samples from the two zones contained 221 to 14,500 parts per billion (ppb) gold, 2.3 to 29.2 parts per million (ppm) silver, 56 to 219 ppm copper, 62 to 464 ppm lead, 98 to more than 2,000 ppm arsenic, 76 to more than 2,000 ppm antimony, 342 to 393 ppm chromium, 7 to 165 ppm bismuth, 10 to 41 ppm tin, and 2.7 to 11.1 ppm mercury (Bundtzen and others, 1998). This prospect, although limited in extent, contains the highest content of gold of any mineralized area in the Horn Mountains.
The Getmuna Creek prospect is in an area marked by anomalous stream sediment and panned concentrate sample sites (Gray and others, 1994; Theodorakos and others, 1992). Stream sediment samples in the area contained up to 1.7 ppm mercury, 120 ppm arsenic, and 7.0 ppm tungsten. One panned concentrate sample taken nearby contained 500 ppm gold, 20 ppm silver, and microscopically visible gold and cinnabar.
Geologic map unit (-158.499018696317, 61.7679453688553)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Undated; may be related to the nearby Horn Mountain pluton which has been dated at 68-69 Ma (Bundtzen and others, 1998).
Alteration of deposit Weak potassium- feldspar alteration adjacent to the veins.

Production and reserves

Workings or exploration Surface sampling was conducted by the Alaska Division of Geological and Geophysical Surveys in 1990 (Bundtzen and others, 1998).
Indication of production None