POW

Prospect, Active

Alternative names

Chisna Ridge

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Pb; Zn
Ore minerals bornite; chalcopyrite; galena; gold; magnetite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-2
Latitude 63.1441
Longitude -144.8069
Nearby scientific data Find additional scientific data near this location
Location and accuracy The POW prospect is one of several in the area that have been repeatedly covered by large blocks of claims south of Chisna Pass and Slate Creek, that have repeatedly been explored by a succession of companies. The coordinates for this record are at the site of the 2010 Corvus Gold drilling. It is about 1.0 mile north of the junction of the Chisna River and Powell Gulch, near the northeast corner of section 35, T. 16 N., R. 14 E. The location is accurate.

Geologic setting

Geologic description

This record specifically describes mineralization at this site as reported by Taylor (2010) and Bittenbender and others (2007). However, there has been a succession of large claim groups over this prospect and extensive work in the area that not only covers it but several other nearby ARDF sites, notably MH380 and MH300. Those records may include data that applies to this site.
C.W. Monroe prospected in the area from 1964 to at least 1973 and staked more than 142 lode claims that covered this site and several square miles south of Chisna Pass (Bittenbender and others, 2007). Paul Glavinovich staked at least 36 claims in the area that may have covered this site. Resource Associates of Alaska (RAA) staked a large block of claims in the late 1970s and early 1980s that covered this prospect and drilled three holes in 1980 that cannot now be accurately located. AMAX Exploration was apparently active in the area in about 1990 and Cominco Alaska Exploration explored in the early 90s. From 2006 to 2008, International Tower Hills Inc. (ITH) staked a large block of claims south of Chisna Pass and Slate Creek that covered this prospect and did considerable mapping and sampling, and carried out extensive geochemical and geophysical surveys. Corvus Gold Inc. (who spun off from ITH) drilled 3 holes in 2010 to test a breccia zone and did more geologic mapping, sampling, and geochemical and geophysical surveys. The prospect has also been examined and sampled by several several state and federal agencies.
There have been several descriptions of the mineralization here. As described by Nokleberg and others (1991), the mineralization consists of disseminated sulfides and local massive to semi-massive sulfides in the Permian (?) meta-andesite and meta-dacite. A prominent zone of sulfidized rock that strikes northwest crops out in a gully near the northeast corner of section 35, T. 20 S., R. 15 E. (Randy Moore and C. C. Hawley, written communication, 1996). One sample of semi-massive pyrite, chalcopyrite, and possibly bornite assayed 0.488 ounce of gold per ton and more than 1 percent copper. Other samples from the mineralized area collected by Moore and Hawley contained less than 500 parts per million (ppm) copper.
As described by Taylor (2010), the POW deposit consists of a structurally-controlled chalcopyrite-bearing breccia several meters wide in a 200-foot-wide, silica-pyrite alteration envelope. The host rocks are porphyritic andesite and dacite of the Devonian or Lower Carboniferous Chisna Formation, and flysch, chert, and limestone of the Pennsylvanian to Permian Mankomen Group. These rocks are cut by many porphyry dikes and by stocks of diorite and monzonite. A large stock of gabbro notable for its magnetic anomaly is about 2 miles to the northwest at peak 5850.
Nokleberg and others (1991) report altered rocks with disseminated galena and sphalerite. Samples contained up to 28.4 parts per million (ppm) silver, 1,235 ppm arsenic, 2,690 ppm lead, and 1,560 ppm zinc. A sample, probably of massive sulfides assayed 2 ppm gold, 70 ppm silver, 2 percent copper, 1,500 ppm arsenic, 30 ppm tin, and 530 ppm zinc. They suggest that the deposit may be a distal porphyry copper deposit, possibly of Permian age.
Bittenbender and others (2007) examined and sampled the prospect. Samples of highly oxidized volcanic rocks from a small trench on what was probably the site of one of the 1980 holes RAA drilled contained up to 23.4 ppm gold, 53.9 ppm silver, and 3.2 percent copper. They also found skarn mineralization here or nearby. They suggest that the mineralization is related to a nearby 300.4 +/- 1.4 Ma (Pennsylvanian) quartz monzonite.
Although the three holes that were drilled by RAA in 1980 cannot be located exactly, it is known that their best intercept was 2 feet with 3.4 percent copper, 0.9 ounce of gold per ton, and 0.25 ounce of silver per ton (Taylor, 2010). An intercept 68 feet long averaged 0.676 percent copper, 0.306 ounce of silver per ton, and 0.0416 ounce of gold per ton. The holes indicated a complicated geologic structure. The best intercepts in the 2010 Corvus drilling was 0.35 meter with 3.69 grams of gold per tonne and 8.71 grams of silver per tonne; 1.98 meters with 0.26 percent copper, 1.58 grams of gold per tonne, and 4.67 grams of silver per tonne; and 23 meters with 0.38 percent copper, 0.43 gram of gold per tonne, and 7.5 grams of silver per tonne.
The preceding information is specific in location and geology to the immediate area around the Corvus 2010 POW drilling. However, their claims and their work covered an area at least 2 kilometers wide and 5,5 kilometers long oriented generally northwest of their POW drill site. Many of their samples in this broad contained 0.1 to 13.7 percent copper. ARDF sites MH380, MH290, MH314, and MH315 are in this area and further work will probably be necessary to fully understand the extent and continuity of the mineralization. Taylor (2010), for instance, notes that magnetite-breccia pipes are associated with porphyry dikes in the western half of the claim block.
In April 2016, Corvus Gold Inc. announced that its wholly owned Alaskan subsidiary, Raven Gold Alaska Inc. signed an agreement with Millrock Resources Inc. on the Chisna project in south-central Alaska (Athey and Werdon, 2017). The purchase included a proprietary exploration database covering the claims and the surrounding district. The data represents an estimated US$11 million worth of exploration work to date in the Chisna project area.
Geologic map unit (-144.809126892324, 63.1437029329311)
Mineral deposit model Variously interpreted as a structurally controlled, copper-gold breccia zone; as disseminated, copper-gold massive and semi-massive sulfides in Paleozoic volcaniclastic rocks; as being a distal porphyry copper deposit, and as having skarn affinities.
Age of mineralization Conflicting or uncertain assignments from several companies and agencies; Pennsylvanian and Permian ages have been suggested.
Alteration of deposit Strong silica-pyrite alteration zones.

Production and reserves

Workings or exploration C.W. Monroe prospected in the area from 1964 to at least 1973 and staked more than 142 lode claims that covered this site and several square miles south of Chisna Pass (Bittenbender and others, 2007). Paul Glavinovich staked at least 36 claims in the area that may have covered this site. Resource Associates of Alaska (RAA)staked a large block of claims in the late 1970s and early 1980s that covered this prospect and drilled three holes in 1980 that cannot now be accurately located. AMAX Exploration was apparently active in the area in about 1990 and Cominco Alaska Exploration explored in the early 90s. From 2006 to 2008, International Tower Hills Inc. (ITH) staked a large block of claims south of Chisna Pass and Slate Creek that covered this prospect and did considerable mapping and sampling, and carried out extensive geochemical and geophysical surveys. Corvus Gold Inc. (who spun off from ITH) drilled 3 holes in 2010 to test a breccia zone and did more geologic mapping, sampling, and geochemical and geophysical surveys. The prospect has also been examined and sampled by several several state and federal agencies.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Bittenbender, P.E., Bean, K.W., Kurtak, J.M., and Deininger, James Jr., 2007, Mineral assessment of the Delta River Mining District area, east-central, Alaska: U.S. Bureau of Land Management, Alaska Technical Report 57, 675 p.
Corvus Gold Inc., 2010 Corvus Gold Inc. intersects copper and gold mineralization in first drill holes in the POW target, Chisna project, Alaska: http://www.corvusgold.com/news/index.php?&content_id=36 (News release, Sept. 30, 2010)
Taylor, Chris, 2010, Technical report on the Chisna copper gold project, Chistochina mining district, south-central Alaska: Unpublished technical report for International Tower Hill Mines Ltd., 107 p. (posted on www.sedar.com, July 15, 2010).
Reporters D.J. Grybeck (Contractor, USGS); M.B. Werdon (DGGS)
Last report date 8/26/2017