Zachary Bay

Prospect, Active

Alternative names

Unga

Commodities and mineralogy

Main commodities Ag; Pb; Zn
Other commodities Cu
Ore minerals chalcopyrite; galena; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PM
Quadrangle map, 1:63,360-scale B-2
Latitude 55.2729
Longitude -160.6628
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Zachary Bay is prospect is is about 2.0 miles south of the south end of Zachary Bay and about 4.9 miles northwest of the seaplane anchorage at Squaw Harbor on Baralof Bay. It is near the center of section 3, T. 57 S., R. 74 W. The location is probably accurate to within a half mile.

Geologic setting

Geologic description

The rocks around the Zachary Bay prospect are part of the Eocene to Oligocene, Popof volcanic unit (Wilson and others, 1995). The deposit is in the northeast section of the Aquila-Shumagin fault system, which strikes northeast across Unga Island.
Rock-chip samples taken at the surface in 1974 across 46 meters averaged 0.36 percent copper and 0.550 gram of gold per tonne (Redstar Gold Corp., 2012, January 18]; 2012 [March 20]) . Four holes less than 20 meters deep drilled in 1975 by Quintana Minerals Corp. and Duval Corp. cut disseminated copper-gold mineralization in intrusive rocks. The deepest hole, 17 meters deep, was mineralized over its entire length; 10.7 meters averaged 0.11 percent copper and 0.280 gram of gold per tonne.
The core was reanalyzed and reexamined by Resource Associates of Alaska in 1981. They also located a 50-foot-wide zone of brecciated, silicified, pyritic andesite that may be a breccia pipe (Trujillo and others, 1981). The breccia fragments are filled in by a matrix of chalcopyrite, sphalerite, and galena over a 35-foot width of the zone. One sample of mineralized rock assayed 1.09 ounces of silver per ton, 2.07 percent zinc, and 0.58 percent lead.
In 2011, Redstar Gold Corp. (2012, January 18]; 2012 [March 20]) began work in the area in a joint venture with Full Metal Minerals Inc. on land they were purchasing and land leased from the Aleut Native Corporation. They proposed that the deposit is a classic porphyry copper-gold deposit with abundant disseminated hydrothermal biotite, magnetite and chalcopyrite in a quartz-diorite porphyry with pink potassium feldspar phenocrysts.
Geologic map unit (-160.664840959124, 55.2720697711769)
Mineral deposit model Copper-gold porphyry (Cox and Singer, 1986, model 20c).
Mineral deposit model number 20c
Age of mineralization Eocene or younger based on the age of the host rock.
Alteration of deposit The mineralization is accompanied by strong silicification and hydrothermal biotite.

Production and reserves

Workings or exploration
Surface rock-chip samples were taken in 1974 and four holes less than 20 meters deep were drilled in 1975 by Quintana Minerals Corp. and Duval Corp. The core was reanalyzed and reexamined by Resource Associates of Alaska in 1981 and they sampled the surface. In 2011, Redstar Gold Corp. (2012, January 18]; 2012 [March 20]) began work in the area in a joint venture with Full Metal Minerals Inc.
Redstar Gold Corp. conducted two phases of exploration in 2016 on their Unga project, which includes the Shumagin (PM064), Apollo (PM079; PM084), Centennial, Orange Mountain (PM067), Zachary Bay (PM054), Amethyst (PM092), and Aquila (PM086) epithermal gold-silver prospects. The Shumagin trend parallels the historically mined Apollo–Sitka vein system (PM079; PM084; PM076), which between 1886 and 1922 produced approximately 150,000 ounces of gold at a grade of approximately 0.292 ounce of gold per ton (Athey and Werdon, 2017).
In June 2016, Redstar Gold Corp.’s Phase I surface program included classifying alteration assemblages and conducting other geologic work to identify drill targets. From October through November, Phase II’s drilling program tested the down-dip and along-strike expansion potential of high-grade vein/breccia mineralization within the Shumigan Gold Zone (PM064). A total of 1,505 meters were drilled in 7 holes spaced over ~750 meters of strike length. All drill holes intersected the target structure, which includes multi-generational phreatomagmatic breccias, hydrothermal breccias, and late breccias and veins with colloform-crustiform- to cockade-textured quartz-adularia-carbonate (± rhodochrosite, ± green clay). Select intervals from drill holes 16SH019 and 16SH020 include 0.9 meter at 14.95 grams of gold per tonne and 1.15 meters at 11.3 grams of gold per tonne; release of full assay results is planned for late January 2017 (Athey and Werdon, 2017).
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

The land belongs to the Aleut Native Corporation; in early 2012, the property was being explored under lease by a joint venture of Redstar Gold Corp. and Full Metals Inc.

References

MRDS Number 10308127

References

Peterson, R.J., Handverger, P., Rosenkrans, D., Bartels, E, and Woolston, D., 1983, Shumagin Islands precious metal exploration program southwest Alaska: UNC Teton Exploration Drilling Company report, 61 p. (Report held by the Aleut Corporation, Anchorage, Alaska).
Redstar Gold Corp., 2012, Growth through discovery: http://www.redstargold.com/in/pdf/RGC-Presentation.pdf (corporate presentation current as as of March 20, 2012).
Redstar Gold Corp., 2012, Redstar identified new high-grade gold vein system with 94.7 g/t and 1840 g/t Ag at surface, Unga project, Alaska: http://www.redstargold.com/s/NewsReleases.asp?ReportID=502474 (News release, January 18, 2012).
Trujillo, R.S., Andersen, G.D., MacLeod, T., Hendrick, K., Farnham, S., Peterson, J., 1981. Exploration and evaluation of the Unga-Popof-Korovan Islands portion of lands leased from Aleut Native Corporation: Resource Associates of Alaska report, 70 p., 38 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Reporters S.H. Pilcher (Anchorage, Alaska); D.J. Grybeck (Contractor, USGS); M.B. Werdon (DGGS)
Last report date 8/26/2017