Fort Hamlin Hills pluton

Occurrence, Inactive

Commodities and mineralogy

Main commodities Rb; Sn
Other commodities Ta; W
Ore minerals pyrite
Gangue minerals hematite; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale BV
Quadrangle map, 1:63,360-scale A-6
Latitude 66.01
Longitude -149.92
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is located about 24 miles west of Stevens Village along a high (approximately 2500-foot level) ridge in the Fort Hamlin Hills (sec. 29, T. 14 N., R. 11 W., of the Fairbanks Meridian). Location is accurate within a 1-mile radius.

Geologic setting

Geologic description

This occurrence consists of a sample from a 5- to 8-ft.-wide tourmaline- and pyrite-bearing altered leucocratic, felsic dike which cuts biotite granite (Barker and Foley, 1986). The dike is variably stained brick-red and green and exposed for 50 feet along a north-trending strike. Alteration extends several feet into the granite, and secondary minerals in the dike and host granite include minor chlorite, sericite, tourmaline, hematite, and pyrite.
Geologic map unit (-149.922588294129, 66.0095440806314)
Mineral deposit model Sn veins? (Cox and Singer, 1986; model 15b?).
Mineral deposit model number 15b?
Age of mineralization The host dike cuts (and is probably related to) a biotite granite of the Fort Hamlin Hills pluton. The Fort Hamlin Hills pluton has not been dated, but its age is likely Cretaceous, based on ages of several compositionally similar plutons in the area which have ages ranging from 106 to 112 Ma (Barker, 1991).
Alteration of deposit Secondary chlorite, sericite, tourmaline, hematite and pyrite.

Production and reserves

Indication of production None

Additional comments

Occurrence consists of a single strongly anomalous sample. Sample number 181 (Barker and Foley, 1986) contained 308 ppm Sn, 1,102 ppm Rb, 29 ppm Ta, and 16 ppm W.