Old Man Breccia

Prospect, Active

Commodities and mineralogy

Main commodities Au; Cu
Other commodities Fe
Ore minerals chalcopyrite; gold; pyrite; pyrrhotite
Gangue minerals carbonate; quartz

Geographic location

Quadrangle map, 1:250,000-scale TY
Quadrangle map, 1:63,360-scale D-7
Latitude 61.9398
Longitude -152.3248
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Old Man Breccia prospect is about 3.8 miles west-southwest of the junction of Old Man Creek and Happy River. It is about 0.5 mile west of the center of section 1, T. 21 N., R. 17 W. The location is accurate.

Geologic setting

Geologic description

In early 2010, the Old Man Breccia prospect was part of the Whistler project of Kiska Metals Corporation and was is actively being explored (Kiska Metals Corporation, 2010a). Cominco Alaska began mineral exploration in the area in 1986; they found the deposit but ended their work in 1989. From 2004 to 2006 Kennecott Exploration Company carried out major exploration in the area, including geologic mapping; soil, stream sediment, and rock geochemistry; and geophysical surveys. They staked several large blocks of ground that included the Old Man Breccia prospect. In 2005, Geoinformatics Exploration Inc. acquired the property from Kennecott, and in 2009, Kiska Metals Corporation was formed by a merger of Geoinformatics and Rimfire Minerals Corporation.
A float sample of quartz with pyrrhotite, chalcopyrite, and pyrite, that assayed contained several ounces of gold per ton led to the discovery of the deposit. It consists of breccia in siltstone of Upper Jurassic and Lower Cretaceous flysch (KJs) of the Kahiltna terrane (Cominco American Incorporated, unpublished reports, 1986-1988; Wilson and others, 2009). The breccia is exposed over an area approximately 105 feet by 90 feet. It consists of angular clasts of argillite from less than one inch to a few inches cemented by milky quartz and lesser carbonate. The quartz-argillite breccia forms sinuous, sub-vertical zones around large argillite blocks. Sulfides in the breccia are sparse (generally less than 1 percent) and consist of pyrrhotite, pyrite, chalcopyrite, and rare coarse-grained arsenopyrite. Quartz veins with pyrrhotite, pyrite, and chalcopyrite that crosscut the breccia zone vary from a few inches to 2 feet thick; they contain occasional specks of visible gold. There is no obvious alteration.
In 2009, three trenches showed substantial gold values in an area of breccia about 30 meters in diameter (Kiska Metals Corporation, 2010b). Channel samples included: 0.74 gram of gold per tonne along 16 meters; 1.94 grams of gold per tonne along 24 meters; 3.34 grams of gold per tonne along 28 meters; and 7.12 grams of gold per tonne along 10 meters. Only small sections of the trenches had gold values below 0.30 gram of gold per tonne.
Geologic map unit (-152.327024136427, 61.9392270333529)
Mineral deposit model Gold-bearing sulfide breccia.
Age of mineralization The breccia is younger than the Jurassic-Cretaceous host rock.
Alteration of deposit Iron-oxide.

Production and reserves

Workings or exploration Discovered by Cominco in the early 1980s. Exploration work included mapping, rock chip geochemistry, soil sampling, magnetic and VLF geophysical surveys, and diamond drilling. Kennecott Exploration Company probably did some work from 2004 to 2006. Trenched and sampled by Kiska Metals Exploration in 2009.
Indication of production None
Reserve estimates None.
Production notes None.


MRDS Number A106260


Kiska Metals Corporation, 2010a, Whistler project overview; http://www.kiskametals.com/s/Whistler.asp?ReportID=370036 (as of February 26, 2010)
Kiska Metals Corporation, 2010b, Old Man Breccia returns 28 meters of 23.34 g/t gold i channel sampling at Whistler project, Alaska: http://www.kiskametals.com/s/Kiska_News.asp?ReportID=380655 (News release dated January 14, 2010)
Reporters Madelyn A. Millholland (Anchorage); D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010