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  3. Mineral Resource Data System (MRDS)

Unnamed (near Helen Todd Lake)

Occurrence in Alaska, United States with commodity Gold
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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. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10307681
Record type Site
Current site name Unnamed (near Helen Todd Lake)

Geographic coordinates

Geographic coordinates: -131.49876, 55.22274 (WGS84)
Relative position This site represents two occurrences about 0.3 mile apart on the east shore of the unnamed lake immediately north of Helen Todd Lake. The occurrences are in section 2, T. 77 S., R. 92 E., of the Copper River Meridian. The map site is at the midpoint between these occurrences. The site corresponds to loc. 13 in Berg (1972 [I 684]), and loc. 9 in Karl (1992). The location is accurate within 0.15 mile.

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
Gold Primary

Materials information

Materials Type of material
Pyrite Ore
Quartz Gangue

Alteration

  • (Local) Pyritization of tuffaceous phyllite country rock. Intermittent zones of iron staining for several hundred yards along shoreline of lake.

Mineral occurrence model information

Model code 273
USGS model code 36a
Deposit model name Low-sulfide Au-quartz vein
Mark3 model number 27

Nearby scientific data

(1) -131.49876, 55.22274
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The country rocks in the area of this site are Upper Jurassic or Cretaceous flyschlike metasedimentary rocks that are gradationally interbedded with andesitic or basaltic metatuff (Berg, 1972; Berg and others, 1988; Karl, 1992). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The occurrences consist of pyrite-bearing, vuggy quartz veins and ribbon-quartz veins up to 10 feet thick that cut gray phyllite, or form the matrix of phyllite breccia (Berg, 1972, loc. 13). A sample of ribbon quartz containing pyrite cubes assayed 4 ppm Au (Karl, 1992, loc. 9).
  • Age = Probably Late Cretaceous or younger.

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 ribbon quartz containing pyrite cubes assayed 4 ppm Au (Karl, 1992, loc. 9).

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 = Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

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.