Unnamed (head of Purple Lake)

Occurrence in Alaska, United States with commodity Copper

Geologic information

Identification information

Deposit ID 10001625
MRDS ID A012389
Record type Site
Current site name Unnamed (head of Purple Lake)

Geographic coordinates

Geographic coordinates: -131.44064, 55.1078 (WGS84)
Relative position This occurrence is on the north shore of an unnamed small lake that drains into the head of Purple Lake. The site is in section 17, T. 78 S., R. 93 E., of the Copper River Meridian. It corresponds to loc. 23 in Berg (1972 [I 684]), loc. 147 in Elliott and others (1978), and loc. 42 in Karl (1992). The location is accurate within 0.1 mile.
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Geographic areas

Country State
United States Alaska


Commodity Importance
Copper Primary

Materials information

Materials Type of material
Chalcopyrite Ore


  • (Local) Local sericitization of trondhjemite hostrock.

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Granite
    Rock unit name Annette Pluton
    Rock description Annette Pluton
    Stratigraphic age (youngest) Late Silurian
    Stratigraphic age (youngest) Late Silurian
  • Host or associated Host
    Rock type Plutonic Rock > Granitoid > Granite

Nearby scientific data

(1) -131.44064, 55.1078

Comments on the geologic information

  • Geologic Description = The country rock in the area of this site is Silurian trondhjemite (Berg, 1972). Locally, the trondhjemite is sheared and sericitized, probably owing to Late Cretaceous greenschist-grade regional metamorphism. The occurrence consists of small amounts of chalcopyrite disseminated in the trondhjemite.

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Mining district

District name Ketchikan

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012389
USGS Alaska Resource Data File ARDF KC151

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

    Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 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 Cu deposit of undetermined origin.

Reporter information

Type Date Name Affiliation Comment
Reporter 06-JUL-1999 H.C. Berg U.S. Geological Survey