Gossan Ridge

Prospect, Undetermined

Commodities and mineralogy

Main commodities Ag; As; Au; Bi; Sb; Te; W
Other commodities Mo
Ore minerals arsenopyrite; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale BH
Quadrangle map, 1:63,360-scale A-2
Latitude 60.2301
Longitude -159.3963
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Gossan Ridge prospect probably is on the north side of the ridge south of (unnamed) lake 1541 (which is about 3 miles northeast of Gold Lake. It is probably about 1.3 mile south of the northeast corner of lake 1541, about 0.3 mile south of the center of section 29, T. 2 N., R. 58 W., of the Seward Meridian. However, the location is uncertain and the prospect may be a mile or more distant.

Geologic setting

Geologic description

The Gossan Ridge prospect was first identified in the late 1980s by following up highly anomaly gold, arsenic, and antimony values in panned concentrates. The anomalous values covered an area at least 1,500 meters long and 330 meters wide that coincides with a conspicuous rusty-orange color anomaly (Gold Crest Mines Inc., 2011 [summary]). Samples collected by Gold Crest in an area about 450 meters long by 200 meters wide averaged over 0.1 gram of gold per ton and contained up to 0.2 ounce of gold per ton. The mineralization is related to a series of feldspar breccias, porphyry dikes and altered country rock. Numerous epithermal arsenopyrite-stibnite-quartz veins and replacement zones occur along faults and dike margins. The intrusive rocks show pervasive biotite and sericite alteration. The rocks outside the mineralized area are Upper Jurassic or Lower Cretaceous argillite and tuffaceous chert (Box and others, 2003).
The prospect was restaked and reexamined by Gold Crest in 2006 (Gold Crest Mines Inc., 2011 [summary]). They collected 39 rock samples; all had detectable gold. The highest value was 4.8 grams of gold per tonne and the samples contained up to 140 parts per million (ppm) bismuth, 25 ppm silver, 60 ppm molybdenum, 1,000 ppm antimony, 35 ppm tungsten, and 12 ppm tellurium (Gold Crest Mines Inc., 2011 [geochemistry]. Several detailed ground geophysical surveys in 2007 suggest that the prospect is the mineralized cap of a buried intrusion (Gold Crest, 2011 [aeromagnetic]).
Geologic map unit (-159.398547556192, 60.2293630204962)
Mineral deposit model Vein and disseminated mineralization in breccias, dikes, and altered country rock.
Age of mineralization Jurassic or younger based on the age of the host rocks.
Alteration of deposit The intrusive rocks associated with the mineralization show pervasive biotite and sericite alteration; the country rock is also altered.

Production and reserves

Workings or exploration Sampled and mapped in the late 80s(?) and sampled and mapped in 2006 and 2007 by Gold Crest Mines Inc. Covered by extensive geochemical and ground and aerial geophysical surveys.
Indication of production None

References

References

Gold Crest Mines Inc. 2011, Gossan Ridge target [summary]: http://www.goldcrestminesinc.com/projects/alaska/gl-gossan-ridge.asp (as of Feb. 11, 2011)
Reporters D.J. Grybeck (Contractor, USGS)
Last report date 2/28/2011