Oxide Ridge

Prospect, Active

Commodities and mineralogy

Main commodities Au; Cu; Mo
Other commodities As
Ore minerals arsenopyrite; chalcopyrite; gold; molybdenite; pyrite

Geographic location

Quadrangle map, 1:250,000-scale TL
Quadrangle map, 1:63,360-scale A-6
Latitude 62.0112
Longitude -152.9043
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Oxide Ridge prospect is about 3.3 miles northeast of Portage Pass and about 0.5 mile west of the center of section 11, T. 22 N., R. 20 W., of the Seward Meridian. The location is accurate to within 100 feet to the center of the prospect.

Geologic setting

Geologic description

The rocks in the area are Jurassic and Cretaceous marine sedimentary rocks that are intruded by the 65-66 Ma granodiorite of Mount Estelle (Reed and Nelson, 1980). The granodiorite at this prospect has a leucocratic equigranular phase and a porphyritic phase with potassium feldspar phenocrysts up to 10 millimeters in size (Cominco American Incorporated, unpublished report).
As described by Cominco American, chalcopyrite, pyrrhotite, arsenopyrite, molybdenite and pyrite occur as joint coatings, in veins, and as disseminations adjacent to northwest-striking mineralized joint sets. Sulfide-bearing rock samples from this site contain from 60 parts per billion (ppb) gold to more than 1 ounce of gold per ton. Silver is generally below the detection limit of 0.4 parts per million (ppm) but some samples contain as much as 11 ppm silver.
Altered granodiorite float about 2 miles to the southwest contains gold-bearing veinlets of arsenopyrite and pyrite (TL063). Curtin and others (1978) report panned-concentrate samples with visible gold from Quaternary gravels about one mile downstream from this locality (TL052).
In 2011, Millrock Resources Inc. on behalf of Teck America Inc. drilled a 457.9-meter hole. The entire hole was invariably-altered, fractured intrusive rocks cut by porphyritic dikes. The mineralization occurs in quartz veins and stockworks; gold is associated with arsenopyrite and chalcopyrite. Over 350 meters of the hole averaged 0.43 gram of gold per tonne. Some notable intercepts were: 15.73 meters that contained 0.98 gram of gold per tonne; 31.03 meters that contained 0.79 gram of gold per tonne; and 4.48 meters that contained 0.84 gram of gold per tonne.
In 2012, Millrock Resources Inc. drilled one drill hole. Mineralized intercepts include 10.7 meters of 0.51 gram of gold per tonne, and 7.6 meters of 0.75 gram of gold per tonne (Millrock Resources Inc., 2012).
Geologic map unit (-152.906544828598, 62.0106100053831)
Mineral deposit model Intrusion-related gold (Millrock Resources Inc., 2011).
Age of mineralization Late Cretaceous/early Tertiary?; mineralization in the area is thought to be related to the 65-66 Ma, granodiorite of Mount Estelle (Cominco American Incorporated, unpublished report).
Alteration of deposit Most of the 2011 hole was in variably-altered intrusive rocks (Millrock Resources Inc., 2011).

Production and reserves

Workings or exploration Cominco American Inc. mapped and collected rock-chip samples in the late 1980s. A 457.8-meter hole was drilled by Millrock Resources Inc. in 2011. Another hole was drilled in 2012. Mineralized intercepts include 10.7 meters of 0.51 gram of gold per tonne, and 7.6 meters of 0.75 gram of gold per tonne (Millrock Resources Inc., 2012).
Indication of production None
Reserve estimates None.
Production notes None.

References

MRDS Number 10308453

References

Millrock Resource Inc., 2012, Millrock Discovers New Gold Zone at Estelle Project, Alaska: http://www.millrockresources.com/news/millrock-discovers-new-gold-zone-at-estelle-project-alaska (News release, September 10, 2012, as of September 20, 2014).
Millrock Resources Inc., 2011, Millrock intersects intrusion-related gold system at Estelle project, Alaska: http://www.millrockresources.com/news/millrock-intersects-intrusion-related-gold-system-at-estelle-project-alaska (News release, November 9, 2011, as of December 2, 2014).
Reporters Madelyn A. Millholland (Millholland & Associates); D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 12/2/2014