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Unnamed (near Purple Lake)

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

Geologic information

Identification information

Deposit ID 10307694
Record type Site
Current site name Unnamed (near Purple Lake)

Geographic coordinates

Geographic coordinates: -131.53676, 55.09474 (WGS84)
Relative position This occurrence is at an elevation of about 500 feet, midway between the northeast head of Tamgas Harbor and the foot of Purple Lake. The site is in section 22 T. 78 S., R. 92 E., of the Copper River Meridian. It corresponds to loc. 45 in Karl (1972). The location, which is erroneously marked as a mine on the Ketchikan A-5 topographic map (1955 ed., revised 1962), is accurate to within about a hundred feet.

Site location context

Political divisions (FIPS codes)

Prince of Wales-Hyder(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Ketchikan A-5(quadrangle 1:63,360 scale)

Ketchikan SW(quadrangle 1:100,000 scale)

Ketchikan(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Ketchikan(hydrologic unit)

Southern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Annette Island Indian Reservation(American Indian Reservation)

American Indian Reservation BIA(Type of land area)

BIA(Federal land areas administered by BIA)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Copper Primary
Molybdenum Primary

Alteration

  • (Local) The trondhjemite locally is sericitized and permeated with hydrothermal hematite. The aplite dikes may postdate this alteration.

Nearby scientific data

(1) -131.53676, 55.09474
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The country rock at this site is Silurian trondhjemite (Berg, 1972 [I 684]; Berg and others, 1988). It was regionally metamorphosed to greenschist grade in Late Cretaceous time, and locally is intensely sheared, sericitized, and permeated with hydrothermal hematite. The occurrence consists of unspecified disseminated sulfide minerals in aplite dikes that cut altered trondhjemite. A sample of the sulfide-bearing aplite contained 0.25 ppm Au, 1.5 ppm Ag, 1000 ppm Cu, and 50 ppm Mo (Karl, 1992, loc. 45). If the aplite dikes postdate the Late Cretaceous regional metamorphism, the mineralization may be Tertiary in age.
  • Ore Material = Unspecified sulfides
  • Age = If the aplite dikes postdate the Late Cretaceous regional metamorphism, the mineralization may be Tertiary in age.

Economic information about the deposit and operations

Development status Occurrence

Mining district

District name Ketchikan

Comments on the workings information

  • Workings / Exploration = A sample of the sulfide-bearing aplite contained 0.25 ppm Au, 1.5 ppm Ag, 1000 ppm Cu, and 50 ppm Mo (Karl, 1992, loc. 45).

Reference information

Bibliographic references

  • Deposit

    Berg, H.C., 1972, Geologic map of Annette Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-684, 8 p., 1 sheet, scale 1:63,360,

  • Deposit

    Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

  • Deposit

    Karl, S.M., 1992, Map and table of mineral deposits on Annette Island, Alaska: U.S. Geological Survey Open-File Report 92-690, 57 p., 1 map, scale 1:63,360.

Comments on the references

  • Primary Reference = Karl, 1992

General comments

Subject category Comment text
Deposit Model Name = Disseminated sulfide mineralization of undetermined origin.

Reporter information

Type Date Name Affiliation Comment
Reporter 07-JUL-99 H.C. Berg U.S. Geological Survey

Beyond USGS

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

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.