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Trachsel

Occurrence in Alaska, United States with commodity Iron
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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 10093964
MRDS ID A010644
Record type Site
Current site name Trachsel
Alternate or previous names Snug Harbor

Geographic coordinates

Geographic coordinates: -152.85375, 60.24556 (WGS84)
Relative position Magnetic Island is at the mouth of Tuxedni River, which is on the west side of Cook Inlet, due west of Ninilchik. The island can be accessed by small boat or seaplane. However, the trip should only be attempted at high tide and under favorable weather conditions since most of Tuxedni Bay is dry at low tide. There are two magnetite occurrences on the island, one on the east and one on the west side. This is Cobb's (1972, MF-377) location 1 and is accurate to within 300 feet.

Site location context

Political divisions (FIPS codes)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Kenai A-8 NW(quadrangle 1:24,000 scale)

Kenai SW(quadrangle 1:100,000 scale)

Kenai(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Tuxedni-Kamishak Bays(hydrologic unit)

Western Cook Inlet(hydrologic accounting unit)

South Central Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Lake Clark 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
Iron Primary

Materials information

Materials Type of material
Magnetite Ore
Garnet Gangue
Pyroxene Gangue

Alteration

  • (Local) Hornfels and metasomatic alteration are present in this occurrence.

Mineral occurrence model information

Model code 62
USGS model code 18d
Deposit model name Skarn Fe

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Granite
    Rock unit name Aleution Range Batholith
    Rock description Aleution Range Batholith
  • Host or associated Host
    Rock type Metamorphic Rock > Metasedimentary Rock > Marble
    Rock unit name Talkeetna Formation;
    Rock description Talkeetna Formation;

Nearby scientific data

(1) -152.85375, 60.24556
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = Magnetite Island consists of metamorphosed volcanic rocks of Early Jurassic Talkeetna Formation and an Upper Triassic marble that has been subjected to contact metamorphism by Jurassic quartz diorite associated with the Alaska-Aleution Range batholith (Grantz, 1956). There are two magnetite occurrences on the island. The western occurrence consists of a single lens of magnetite garnet skarn. The skarn appears to be about 35 feet wide and is exposed for about 55 feet along strike. A reconnaissance dip -needle traverse indicated the total strike length of the body is about 110 feet. This exposed skarn strikes N40E and dips 40SE. The hanging wall of the skarn is a white medium grain marble of Upper Triassic age which has been recrystallized by contact metamorphism. The foot wall of this occurrence is hornfelsed siltstone and volcanic rock of the Talkeetna Formation. The contact between the marble and the hornfels is unclear but it may be a fault (Grantz, 1956). ? the eastern occurrence consists of magnetite disseminated in hornfels, probably derived from volcanic rocks. The magnetite occurs in two parallel zones. The upper zone is about 30 feet thick and is separated from the lower zone by 20 feet of hornfelsed volcanics. The lower zone is at least 10 feet thick but its base is not exposed. The mineralized zones strike approximately N35 to 45E and dip 45SE. The magnetite in the eastern zone is disseminated in a matrix of garnet, diopside, chlorite, and plagioclase. No zoning of the skarn minerals are reported. An assay from the upper zone contained 25.8% iron and 0.01% sulfur. However, about one-fifth of the iron may occur in silicate minerals (Grantz, 1956).
  • Age = Jurassic; hornfels related to Intrusion of Jurassic quartz diorite.

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Redoubt

Comments on the reserve resource information

  • Reserves = Up to several thousand tons in zones with 20 to 75% magnetite (Grantz, 1956).

Comments on the workings information

  • Workings / Exploration = Small excavation in sea cave at the western deposit contains 25% to 50% iron.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Grantz, 1956

General comments

Subject category Comment text
Deposit Model Name = Fe skarn (Cox and Singer, 1986; model 18d)

Reporter information

Type Date Name Affiliation Comment
Reporter 01-MAR-1999 Jeff A. Huber 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.