Unnamed (on western Tigalda Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Pb; Zn
Ore minerals gold; pyrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale UM
Quadrangle map, 1:63,360-scale A-4
Latitude 54.11
Longitude -165.14
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents several color anomalies on the west end of the island between Derbin and Kelp Bays. Site location is accurate to within 1 mile.

Geologic setting

Geologic description

This occurrence consists of several color anomalies along a northwest-trending fault which crosses the island between Derkin and Kelp Bays. Rocks in these areas are mostly Tertiary andesites and dacite porphyries which have been intruded by diorite 'bodies' and basalt dikes (Butherus and others, 1979). Within the color anomalies the andesite and diorite are fractured, pyritized, and moderately argillically altered. Quartz-calcite veins, some up to 2 feet thick, are common in the altered and fractured areas.
A sample of quartz-calcite vein material collected by Resource Associates of Alaska contained values of up to 85 ppm copper, 1.2 ppm gold, 96 ppm lead, 18.1 ppm silver, and 176 ppm zinc (Butherus and others, 1979). They also reported values to 8700 ppm arsenic, 250 ppm copper, and 7 ppm mercury from an unknown location on the south side of the island. Kennecott collected 15 samples of vein material in 1985 (Simpson, 1986). They reported gold in quantities up to 4.6 ppm.
Geologic map unit (-165.141968657261, 54.1090920314815)
Mineral deposit model Epithermal gold veins or Creede epithermal veins? (Cox and Singer, 1986; model 25b?).
Mineral deposit model number 25b?
Age of mineralization Tertiary.
Alteration of deposit Country rocks are propylitized, pyritized, and locally argillized.

Production and reserves

Workings or exploration Sampling by Resource Associates of Alaska of one vein returned metal values of 85 ppm copper, 1.2 ppm gold, 96 ppm lead, 18.1 ppm silver, and 176 ppm zinc (Butherus and others, 1979). Kennecott collected 15 samples of vein material and reported gold values up to 4.6 ppm (Simpson, 1986).
Indication of production None

Additional comments

This site is on lands selected by the Aleut Native Corporation.

References

MRDS Number 10308479

References

Butherus, D.L, Gressitt, E.E., Pray, J., Corner, N.G., Lindberg, P.H., and Fankhauser, R.E., 1979, Exploration and evaluation of the Aleut Native Corporation lands; Volume III: Resource Associates of Alaska, 69 p. 90 sheets, various sacales. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)
Randolph, D.B., 1990, Unalaska, 1990 final report: Battle Mountain Exploration Company, 72 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska).
Simpson, D.F., 1986, Aleutian Islands project, 1985 final report: Kennecott Alaska Exploration Company, 54 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)
Reporters S.H. Pilcher (Anchorage)
Last report date 1/27/2000