1. Mineral Resources
  2. Online Spatial Data
  3. Mineral Resource Data System (MRDS)

Unnamed (near Helen Todd Lake)

Occurrence in Alaska, United States with commodity Lead
Map
XML
JSON
KML
D

Geologic information

Identification information

Deposit ID 10307696
Record type Site
Current site name Unnamed (near Helen Todd Lake)

Geographic coordinates

Geographic coordinates: -131.52476, 55.20374 (WGS84)
Relative position This site represents two occurrences at 1000 feet elevation on the hillside west and southwest of Helen Todd Lake. The occurrences are in sections 10 and 11, T. 77 S., R. 92 E., of the Copper River Meridian. They are about 0.4 mile apart, along an unmapped logging road parallel to, and just below, the crestline of a northeast-trending ridge. The map site is approximately midway between the two occurrences. The site corresponds to locs. 28 and 29 in Berg (1972 [I 684]), and to loc. 15a, b in Karl (1992). The location is accurate within about 0.1 mile.
(click for info)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Lead Primary

Materials information

Materials Type of material
Galena Ore
Magnetite Ore
Pyrite Ore
Calcite Gangue

Alteration

  • (Local) The trondhjemite hostrock is sericitized and contains disseminated sulfide minerals.

Nearby scientific data

(1) -131.52476, 55.20374
ListMap

Comments on the geologic information

  • Geologic Description = The country rocks in the area of the site are undivided, metamorphosed Silurian and Ordovician volcanic, sedimentary, and intrusive rocks; and Silurian trondhjemite that intrudes the Silurian and Ordovician rocks (Berg, 1972; Berg and others, 1988). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The occurrences are in foliated, sericitized, trondhjemite, and consist of pyrite, magnetite, and galena in sparse calcite veinlets up to 0.25 inch thick and 2-3 inches long (Berg, 1972, locs. 28, 29; Karl, 1992, loc. 15a, b) the sulfide minerals are also widely disseminated in the trondhjemite.
  • Age = the veins probably are Late Cretaceous or younger.

Economic information

Economic information about the deposit and operations

Development status Occurrence

Mining district

District name Ketchikan

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF KC181

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 and oxide mineralization of undetermined origin.

Reporter information

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