Old Man Diorite

Prospect in Alaska, United States with commodities Silver, Gold, Molybdenum, Arsenic, Barium-Barite

Geologic information

Identification information

Deposit ID 10003501
MRDS ID A106259
Record type Site
Current site name Old Man Diorite

Geographic coordinates

Geographic coordinates: -152.32277, 61.9095 (WGS84)
Relative position Alaska Department of Natural Resources claim records show the prospect located approximately 3000 to 3500 feet in elevation on the south side of Old Man Creek, about five miles up stream from the confluence of Old Man Creek and the Skwentna River in Section 13, T. 21 N., R. 17 W.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Molybdenum Primary
Arsenic Secondary
Barium-Barite Secondary

Comments on the commodity information

  • Gangue = Carbonate

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Gold Ore
Molybdenite Ore
Pyrite Ore
Pyrrhotite Ore
Sphalerite Ore
Chlorite Gangue
Quartz Gangue

Alteration

  • (Local) Carbonate, pyrite, sericite, quartz

Host and associated rocks

  • Host or associated Host
    Stratigraphic age (youngest) Early Miocene
    Stratigraphic age (oldest) Early Cretaceous

Nearby scientific data

(1) -152.32277, 61.9095

Comments on the geologic information

  • Geologic Description = At this locality a Late Cretaceous/Early Tertiary(?) diorite is cut by shallow (10-30 degree) veins less than 1 foot to 5 foot thick, and poorly developed stockwork veins. Mineralization consists of varying amounts of quartz, chlorite, arsenopyrite, pyrite, pyrrhotite, molybdenite, and carbonate. The best gold grades are associated with zones of sub-parallel veins. Gold ranges from ten's of ppb to 0.122 oz/ton (Cominco American Incorporated, unpublished reports, 1986-1987). The diorite is probably one of the late Cretaceous/Early Tertiary Kichatna plutons (TKk) described by Reed and Nelson (1980) in the Talkeetna quadrangle to the north. A K-Ar age of 67.4 +/-2 m.y. suggests that these plutons may be slightly older than the 65-km belt of composite plutons to the west. The veins may be related to the diorite intrusion.
  • Age = The host rock is late Cretaceous/Early Tertiarydiorite; the veins may be related to the diorite intrusion.
  • Age = Host rock is Paleogene - Late Cretaceous.

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 silt and rock chip geochemical sampling, mapping, and diamond drilling. The property is steep and technical climbers with Dihedral Exploration were employed to conduct geologic and geochemical surveys.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A106259
USGS Alaska Resource Data File ARDF TY026

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 = Polymetallic veins

Reporter information

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