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Duke Island Ultramafic Complex

Occurrence in Alaska, United States with commodities Iron, Chromium, Platinum, Nickel, Copper
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Geologic information

Identification information

Deposit ID 10001637
MRDS ID A012405
Record type Site
Current site name Duke Island Ultramafic Complex
Alternate or previous names Ditto ? Prospect

Geographic coordinates

Geographic coordinates: -131.3598, 54.92557 (WGS84)
Location accuracy 2000(meters)
Relative position APPROX. CENTER OF AREA WITH NUMEROUS FE (CR) PROSPECTS
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Geographic areas

Country State
United States Alaska

Comments on the location information

  • PROSPECT IN AREA OF WIDESPREAD IRON MINERALIZATION IN LARGE ULTRAMAFIC COMPLEX, USGS OFR 78-73B, LOCS. 159-174; SEPARATE ENTRIES FOR EACH LOCATION LAND STATUS VALUE CALCULATED 6-94 USING GIS OVERLAY ANALYSIS WITH BLM 1:2,500,000 SCALE OWNERSHIP STATUS MAP (1991).

Commodities

Commodity Importance
Iron Primary
Chromium Secondary
Platinum Tertiary
Nickel Tertiary
Copper Tertiary

Comments on the commodity information

  • ANALYSIS OF 22 SAMPLES: AVE. CONCENTRATIONS OF 0.037 PPM PT IN 10 SAMPLES, 0.033 PPM PD IN 16 SAMPLES, 0.010 PPM RH IN 6 SAMPLES, AND NO IR, USGS PP 800-C, P. C159

Materials information

Materials Type of material
Chromite Ore
Pyrite Gangue
Pyrrhotite Gangue
Chalcopyrite Unknown
Pentlandite Unknown

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Hornblendite
    Rock unit name Duke Island Ultramafic Complex;Duke Island Ultramafic Complex
    Rock description Duke Island Ultramafic Complex;Duke Island Ultramafic Complex
  • Host or associated Host
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Hornblendite
    Rock unit name Duke Island Ultramafic Complex;Duke Island Ultramafic Complex;Duke Island Ultramafic Complex
    Rock description Duke Island Ultramafic Complex;Duke Island Ultramafic Complex;Duke Island Ultramafic Complex

Nearby scientific data

(1) -131.3598, 54.92557
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Comments on the geologic information

  • HORNBLENDE PYROXENITE FORMS PARTIAL TO COMPLETE ENVELOPES AROUND UM BODIES COMPOSED OF GRADED LAYERS OF OLIVINE PYROXENITE AND DUNITE INTRUDED INTO LARGE MASS OF GABBRO; GRADED LAYERING OF PYROXENE AND TITANIFEROUS MAGNETITE OCCURS LOCALLY IN HORNBLENDE PYROXENITE; GABBRO IS ALTERED TO HORNBLENDE GABBRO NEAR CONTACTS WITH ULTRAMAFIC MASSES; LARGER BODIES ARE CONCENTRICALLY ZONED FROM DUNITE CORE TO PYROXENITE RIM

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic
Deposit size Small
Significant No

Mining district

District name Ketchikan

Comments on the reserve resource information

  • "AT LEAST ONE POTENTIALLY SIGNIFICANT DEPOSIT OF TITANIFEROUS MAGNETITE OCCURS IN THE PYROXENITE ZONE OF THE DUKE ISLAND ULTRAMAFIC COMPLEX," USGS OFR 78-73M, P. 27

Comments on the workings information

  • DRILLED BY PRIVATE INTERESTS; NO EXTENSIVE DEVELOPMENT

Comments on development

  • DIAMOND DRILLED BY PRIVATE MINING INTERESTS; DETAILED GEOLOGICAL , GEOPHYSICAL AND GEOCHEMICAL WORK HAS BEEN DONE

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012405

Bibliographic references

  • Deposit

    USGS OFR 78-73B, LOC. 166

  • Deposit

    IRVINE, T.N., 1959, THE ULTRAMAFIC COMPLEX AND RELATED ROCKS OF DUKE ISLAND, SOUTHEASTERN ALASKA: CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, PH.D. THESIS

  • Deposit

    TAYLOR, H.P. AND NOBLE, J.A., 1960, ORIGIN OF THE ULTRAMAFIC COMPLEXES IN SOUTHEASTERN ALASKA: INTERNAT. GEOL. CONG., 21ST, COPENHAGEN, REPT., PT. 13, P. 178-180

  • Deposit

    USGS OFR 78-73M, P. 24-25, 27

  • Deposit

    USGS PP 800-C, P. C159

  • Deposit

    USGS BULL 1246, P. 183

  • Other Database

    BAG-OFR-78-73B-166

General comments

Subject category Comment text
Deposit DATA APPLIES TO DEPOSIT NOS. PR-159 THROUGH PR-174; NUMEROUS PROSPECTS ABOUT WHICH LITTLE IS KNOWN OTHER THAN COMMODITY (FE OR CR) AND LOCATION; IT IS ASSUMED THAT THEY ARE RELATED TO THE ULTRAMAFIC BODIES THAT ARE KNOWN TO OCCUR ON DUKE ISLAND ; INFO.SRC : 1 PUB LIT; 2 UNPUB REPT
Deposit TITANIFEROUS MAGNETITE DISSEMINATED IN RHYTHMICALLY LAYERED HORNBLENDE PYROXENITE; RARE SPECKS OF PYRRHOTITE, PYRITE, PENTLANDITE AND CHALCOPYRITE WIDELY DISSEMINATED IN HORNBLENDE PYROXENITE; CHROMITE OCCURS IN DUNITE AND PERIDOTITE AS DISSEMINATED EUHEDRA AND GRAINS AND AS SMALL MASSIVE VEINS AND CLOTS

Reporter information

Type Date Name Affiliation Comment
Reporter 01-OCT-1986 Leonard, Kenneth R. (Elliott, R. L.) U.S. Geological Survey
Editor 02-SEP-1994 Mosier, Dan U.S. Geological Survey PARSED OUT HOST ROCK AND ASSOCIATED ROCK TYPES, AGES, UNIT NAMES, AND UNIT AGES.