Amaknak Island

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au
Ore minerals gold; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale UN
Quadrangle map, 1:63,360-scale D-2
Latitude 53.885
Longitude -166.5483
Nearby scientific data Find additional scientific data near this location
Location and accuracy Locality is 1.6 km south of Dutch Harbor airport on Amaknak Island and corresponds to locality 1 of Cobb (1972, MF-446); it is accurate to about 400 m. It also is anomaly no. 27 of Christie (1974).

Geologic setting

Geologic description

Christie (1974) reported a color anomaly caused by the oxidation of disseminated pyrite in volcanic breccia of the Unalaska Formation (see Drewes and others, 1961) cut by small swarms of feldspar porphyry andesite and hornblende-biotite porphyry basalt (lamprophyre) dikes. Dikes are oriented 010ø dipping 80ø E. The dikes are weakly mineralized, however small vuggy quartz veins occur adjacent to some dikes. Fracturing in the area varies from moderate to intense. At least one of these quartz veins was gold-bearing on the basis of a report in Drewes and others (1961).
Geologic map unit (-166.550192424572, 53.8841361191469)
Mineral deposit model Epithermal gold vein
Mineral deposit model number 25
Age of mineralization Miocene or younger
Alteration of deposit Rocks are regionally propylitically altered or metamorphosed to low-grade. Area of locality is highly iron-stained. Christie (1974) reported the alteration assemblage of epidote-chlorite-kaolinite-pyrite accompanied by moderate to intense leaching.

Production and reserves

Workings or exploration Brief reconnaissance mapping and sampling reported by Christie (1974); however, in 1992 the entire ridge was being quarried for riprap and fill and being removed for commercial port development (F.H. Wilson, unpublished data, 1992).
Indication of production None

Additional comments

This and other undescribed occurrences were apparently reported to Drewes (Drewes and others, 1961) by someone named Eakle on the basis of local reports.

References