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Unnamed (southwest Gilbert Peninsula)

Occurrence in Alaska, United States with commodities Copper, Molybdenum, Silver, Bismuth, Zinc
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Economic information about the deposit and operations
  12. Mining district
  13. Links to other databases
  14. Bibliographic references
  15. General comments
  16. Reporter information

Geologic information

Identification information

Deposit ID 10002265
MRDS ID A013168
Record type Site
Current site name Unnamed (southwest Gilbert Peninsula)

Geographic coordinates

Geographic coordinates: -136.56321, 58.77472 (WGS84)
Relative position Numerous occurrences of copper and molybdenum minerals are near the southwest tip of Gilbert Peninsula and on an unnamed island south of the southwest tip of the peninsula. The coordinates are the approximate center of these occurrences on the southwest part of Gilbert Peninsula at an elevation of about 100 feet. The location includes location numbers 44 and 45 of MacKevett and others (1971) amd locations 35 and 36 of Cobb (1972-MF-436), and location number 54 of Kimball and others (1978). Kimball and others also reported nearby occurrences (locations 53 and 55) respectively across Hugh Miller Inlet (on Gilbert Peninsula) and across Scidmore Inlet.

Site location context

Political divisions (FIPS codes)

Hoonah-Angoon(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Mount Fairweather D-2(quadrangle 1:63,360 scale)

Mount Fairweather NE(quadrangle 1:100,000 scale)

Mount Fairweather(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Glacier Bay(hydrologic unit)

Northern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Glacier Bay National Park(National Park)

National Park NPS(Type of land area)

NPS(Federal land areas administered by NPS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Copper Primary
Molybdenum Primary
Silver Secondary
Bismuth Critical Secondary
Zinc Critical Secondary

Comments on the commodity information

  • Gangue = alteration products of quartz diorite
  • Gangue = alaskite

Materials information

Materials Type of material
Chalcopyrite Ore
Molybdenite Ore
Pyrite Ore
Sphalerite Ore
Quartz Gangue

Alteration

  • (Local) Silicification in stockwork zones.

Mineral occurrence model information

Model code 79
USGS model code 21a
Deposit model name Porphyry Cu-Mo
Mark3 model number 2

Host and associated rocks

  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite

Nearby scientific data

(1) -136.56321, 58.77472
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = Southern Gilbert Peninsula and nearby areas are mainly underlain by granitic rock of Cretceous age containing local inliers of metamorphosed hornfels and marble of Paleozoic age (Brew and others, 1978). On the southwest tip of Gilbert Peninsula,stockworks of quartz veins in altered quartz diorite--cut by light colored aplite (alaskitic) dikes--occur in a silicified zone at least 50 feet wide and several hundred feet long. The quartz veins contain minor amounts of chalcopyrite and molybdenite close to vein selvages. The mineralogy and intrusive setting suggests a porphyry copper-molybdenum model. Pyritic stockworks and somewhat younger crosscutting pyritic veins also occur to the east across Hugh Miller Inlet and west across Scidmore Inlet. Selected vein samples from location 45 contained as much as 10 ppm silver, 7000 ppm copper and 2000 ppm molybdenum (MacKevett and others, 1971); chip samples collected across 52- and 100-foot long lines were nearly barren. Samples collected in pyritic stockwork vein areas on the west side of Scidmore Inlet contained a trace of molybdenum and as much as 70 ppm bismuth, and 1500 ppm zinc (Kimball and others, 1978, location 55).
  • Age = Tertiary.

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Juneau

Comments on the workings information

  • Workings / Exploration = The mineralized area was described briefly by Rossman (1963, B 1121-K) and investigated in 1966 in conjunction with the Geological Survey's study of Glacier Bay (MacKevett and others, 1971). There are no mine workings. A 0.5 foot quartz vein collected on the southwest tip of Gilbert Peninsula contained 1000 ppm copper; a selected high-grade piece of quartz float contained 10 ppm silver, 7000 ppm copper and 2000 ppm molybdenum (MacKevett and others, 1971, p. 50-51, table 9). To the west, across Scidmore Inlet, a selected sample contained 1500 ppm zinc and 70 ppb bismuth. The average grade of exposed materials is very low, as long chip samples contained only near background amounts of valuable metals.

Reference information

Bibliographic references

  • Deposit

    Rossman, Darwin, 1963, Geology of the eastern part of the Mount Fairweather quadrangle, Glacier Bay, Alaska: U.S. Geological Survey Bulletin 1121-K, p. K1-K57.

  • Deposit

    MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1971, Mineral resources of Glacier Bay National Monument, Alaska: U.S. Geological Survey Professional Paper 632, 90 p., 12 plates, scale 1:250,000.

  • Deposit

    Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p.

  • Deposit

    Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources, in Brew, D. A., and others, Mineral resources of the Glacier Bay National Monument wilderness study area, Alaska: U.S. Geological Survey Open-File Report 78-494, p. C1-C375.

  • Deposit

    Cobb, E.H., 1972, Metallic mineral resources map of the Mount Fairweather quadrangle, AK: U.S. Geological Survey Miscellaneous Field Study Map MF-436, 1 sheet, scale 1:250,000.

Comments on the references

  • Primary Reference = MacKevett and others, 1971

General comments

Subject category Comment text
Deposit Model Name = Porphyry copper-molybdenum (Cox and Singer, 1986; model 21a).
Deposit Other Comments = Fairly large but very low grade quartz vein and stockwork system. It is in Glacier Bay National Park and Preserve.

Reporter information

Type Date Name Affiliation Comment
Reporter 09-APR-99 Hawley, C.C. Hawley Resource Group

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Alaska resources

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