Unnamed

Occurrence in Alaska, United States with commodities Copper, Nickel, Arsenic

Geologic information

Identification information

Deposit ID 10000889
MRDS ID A011543
Record type Site
Current site name Unnamed

Geographic coordinates

Geographic coordinates: -152.41477, 62.53451 (WGS84)
Relative position C.C. Hawley and Associates, Inc. (1978, localities A and B, Fig. 4.1-C(3)) show this occurrence in the northwest quarter of Section 10, T. 28 N., R., 17 W., of the Seward Meridian along a tributary on the north side of the west fork of the Yentna River at about 4600 feet within Denali National Park and Preserve.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Copper Primary
Nickel Primary
Arsenic Secondary

Comments on the commodity information

  • Ore Material = unknown platinoid
  • Ore Material = nickel arsenide

Materials information

Materials Type of material
Chalcopyrite Ore
Pyrrhotite Ore

Alteration

  • (Local) Hydrothermally bleached conglomerate and local zones of tactite are described by C.C. Hawley and Associates, Inc. (1978).

Mineral occurrence model information

Model code 59
USGS model code 18b
Deposit model name Skarn Cu
Mark3 model number 8

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock > Gabbro
    Stratigraphic age (youngest) Pliocene
    Stratigraphic age (youngest) Pennsylvanian
    Stratigraphic age (youngest) Pennsylvanian
  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Granite
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Conglomerate
    Rock unit name Dall Conglomerate
    Rock description Dall Conglomerate

Nearby scientific data

(1) -152.41477, 62.53451

Comments on the geologic information

  • Geologic Description = C.C. Hawley and Associates, Inc. (1978) shown this occurrence at the west end of the Dall tactite region. Mineralization is associated with the early Tertiary Upper Yentna pluton, which consists of syenite, monzonite, lamprophyric peridotite and alkali gabbro dikes, that cuts the Permian Conglomerate of Mt. Dall (Reed and Nelson, 1980; Foley and others, 1997). Two types of mineralization have been noted. C.C. Hawley and Associates, Inc. (1978) describe small pods of sulfides consisting of pyrite, chalcopyrite, and possibly nickel arsenide within local zones of tactite and hydrothermally bleached conglomerate. Rock samples contain up to 1,200 ppm copper, 10,000 ppm nickel, and greater than 10,000 ppm arsenic; nickel and chromium are reported to be anomalous in some samples associated with the gabbro phase of the intrusive (C.C. Hawley and Associates, Inc., 1978). Foley and others (1997) describe very- fine- grained pyrrhotite and chalcopyrite abundantly disseminated in the lamprophyric peridotite and alkali gabbro dikes of the Upper Yentna pluton. These contain up to 0.14% combined copper and nickel, 928 ppm arsenic, 125 ppb gold, 22 ppb platinum and 11 ppb palladium along the northeastern margin of the pluton.? the Upper Yentna pluton, one of the nine composite plutons (Tcp) described by Reed and Nelson (1980), sutures the fault contact between Mesozoic marine sedimentary rocks (KJs) and Paleozoic sedimentary rocks (Pzsu) (Reed and Nelson, 1980). Anomalous gold, platinum-group elements, copper, chrome, nickel and arsenic are reported from these plutons (Reed and others, 1978; Reed and Nelson, 1980; Nelson and others 1992). Gold and platinum group element placers have been worked at sites downstream from these bodies (Mertie, 1919; Cobb, 1973). Also see TL020, TL023, TL052, and TL053.
  • Age = Late Cretaceous/early Tertiary; mineralization is interpreted to be linked to the Upper Yentna pluton, one of the Tertiary composite plutons mapped by Reed and Nelson (1980).

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Yentna

Comments on the workings information

  • Workings / Exploration = Reconnaissance mapping, stream silt and rock sampling are all that have been done here. Rock samples contain up to 1,200 ppm copper, 10,000 ppm nickel, and greater than 10,000 ppm arsenic; nickel and chromium are reported to be anomalous in some samples associated with the gabbro phase of the intrusive (C.C. Hawley and Associates, Inc., 1978). Foley and others (1997) describe very- fine- grained pyrrhotite and chalcopyrite abundantly disseminated in the lamprophyric peridotite and alkali gabbro dikes of the Upper Yentna pluton. These contain up to 0.14% combined copper and nickel, 928 ppm arsenic, 125 ppb gold, 22 ppb platinum and 11 ppb palladium along the northeastern margin of the pluton.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A011543
USGS Alaska Resource Data File ARDF TL019

Bibliographic references

  • Deposit

    Cobb, E.H., 1973, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 p.

  • Deposit

    C.C. Hawley and Associates, Inc., 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska: U.S. Bureau of Mines Open-File Report 24-78, 275 p., 7 plates.

  • Deposit

    Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, scale 1:250,000.

  • Deposit

    Fechner, S.A., Burleigh, R.E.., Foley, J.Y., and Lear, K.G., 1993, Results of the 1991-92 U.S. Bureau of Mines site-specific mineral investigations project in Alaska: U.S. Bureau of Mines Open-File Report 100-93, 127 p.

  • Deposit

    Foley, J.Y., Light, T.D., Nelson, S.W., and Harris, R.A., 1997, Mineral occurrences associated with mafic-ultramafic and related alkaline complexes in Alaska: Economic Geology, Monograph 9, p. 396-449.

  • Deposit

    Mertie, J.B., Jr., 1919, Platinum-bearing gold placers of the Kahiltna Valley: U.S. Geological Survey Bulletin 692-D, p. 233-264.

Comments on the references

  • Primary Reference = Hawley, C.C.and Associates, Inc., 1978; Foley and others, 1997

General comments

Subject category Comment text
Deposit Model Name = Cu skarn deposits (Cox and Singer, 1986; model 18b).
Deposit Other Comments = This site is located within Denali National Park and Preserve.

Reporter information

Type Date Name Affiliation Comment
Reporter 10-AUG-1998 Madelyn A. Millholland Millholland & Associates