Old Man Breccia

Prospect in Alaska, United States with commodities Gold, Copper, Iron

Geologic information

Identification information

Deposit ID 10003502
MRDS ID A106260
Record type Site
Current site name Old Man Breccia

Geographic coordinates

Geographic coordinates: -152.32277, 61.9395 (WGS84)
Relative position Alaska Department of Natural Resources claim records show the prospect in a stream bed of a northern tributary to Old Man Creek, four to five miles up stream from the confluence of Old Man Creek with the Skwentna River in Sections 1 and 2, T. 21 N., R. 17 W.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Copper Primary
Iron Secondary

Comments on the commodity information

  • Gangue = Carbonate

Materials information

Materials Type of material
Chalcopyrite Ore
Gold Ore
Pyrite Ore
Pyrrhotite Ore
Quartz Gangue

Alteration

  • (Local) Iron-oxide

Nearby scientific data

(1) -152.32277, 61.9395

Comments on the geologic information

  • Geologic Description = A float sample of pyrrhotite-chalcopyrite-quartz-pyrite, that contained several ounces of gold, lead to the discovery of a breccia in siltstone, part of Upper Jurassic and Lower Cretaceous flysch (KJs) of the Kahiltna terrane. The breccia is exposed over an area approximately 105 feet x 90 feet. Within the breccia angular clasts of argillite from less than one inch up to a few inches long occur in a matrix of well-healed milky quartz and lesser carbonate. The quartz-argillite breccia forms sinuous, sub-vertical zones around large argillite blocks. Sulfides in breccia are sparse (generally less than 1% total) and consist of pyrrhotite pods +/- pyrite and chalcopyrite, and rare coarse-grained arsenopyrite. Veins of quartz-pyrrhotite-pyrite-chalcopyrite crosscut the breccia zone and vary from a few inches to 2 feet in thickness and contain occasional specks of visible gold. No obvious alteration occurs in the hanging wall (Cominco American Incorporated, unpublished reports,1986-1988).

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Yentna

Comments on the workings information

  • Workings / Exploration = Exploration work included mapping, rock chip geochemistry, grid soil sampling, grid magnetic and VLF geophysical surveys, and diamond drilling. ??

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A106260
USGS Alaska Resource Data File ARDF TY025

Bibliographic references

  • Deposit

    Reed, B.L., and Elliot, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 plates, scale 1:250,000.

  • Deposit

    Reed, B.L., and Elliott, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 sheets, scale 1:250,000.

Comments on the references

  • Primary Reference = Reed and Elliott, 1970

General comments

Subject category Comment text
Deposit Model Name = Gold-bearing, sulfide breccia

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JUN-1998 Madelyn A. Millholland Millholland & Associates