Unnamed

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu
Ore minerals chalcopyrite; pyrite
Gangue minerals magnetite

Geographic location

Quadrangle map, 1:250,000-scale UN
Quadrangle map, 1:63,360-scale B-3
Latitude 53.7033
Longitude -166.9833
Nearby scientific data Find additional scientific data near this location
Location and accuracy West side of head of creek flowing north to Makushin Bay, midway between Tarasof Point and USCGS Point Mist, roughly 2 km inland. Anomaly no. 1 of Christie (1974). Location accurate to within 1 km.

Geologic setting

Geologic description

Occurrence is a 1,000 by 5,000 ft (300 by 500 m) color anomaly in granodiorite or diorite that intrudes rocks of the Unalaska Formation (see Drewes and others, 1961). A small but well-mineralized breccia-pipe is located nearby, possibly within the area of the color anomaly. The color anomaly is oriented N 30√łE, 200-500 ppm copper defined a zone containing more than 2 percent pyrite. Chirstie (1974) reports that areas showing 200-500 ppm copper are confined to zones having quartz veinlets which occur almost exclusively in the dike-like granodiorite to diorite porphyry. The color anomaly is covered to the northeast. Gold potential was not considered during the Quintana reconnaissance evaluation conducted by Chritie.
Geologic map unit (-166.985175281064, 53.7024439554402)
Mineral deposit model Porphyry Cu (Cox and Singer, 1986; model 17) or Epithermal veins (Cox and Singer, 1986; model 25c?).
Mineral deposit model number 17 or 25c?
Age of mineralization Miocene or younger
Alteration of deposit Alteration of the porphyry consists of chloritized mafic minerals, chalky feldspar, and minor disseminated pyrite. In zones outward from the contact with the porphyry the Unalaska Formation displays pervasive sericitic alteration and contains minor quartz veinlets and pyrite. Peripheral to this the rocks contain sericite and pyrite in fractures which grades to pervasively developed chlorite (propylitic alteration) and pyrite limited to fractures; and finally pervasive epidote and disseminated pyrite. Christie (1974) reports partial leaching, complete in the breccia, however the leached phase is not identified.

Production and reserves

Workings or exploration Brief reconnaissance mapping and rock, stream, and soil sampling was reported by Christie (1974). Copper anomalies to 2,400 ppm, molybdenum to 10 ppm, and gold to 0.34 ppm from very limited sampling.
Indication of production None

Additional comments

According to Christie (1974), the mineralized zone goes under cover to the northeast of the exposure and in his interpretation, if their silt sample W-7 and soil sample W-25 had been strongly anomalous, (which they weren't) a soil survey should have been done. Otherwise, he thought the apparent grade and size were of academic interest only. The goal was a copper porphyry system, hence sampling may not have been appropriate to evaluate gold potential

References

MRDS Number A106015

References

Christie, J.S., 1974, Aleut-Quintana-Duval 1974 joint venture, final report: Unpublished Quintana Minerals Corporation report, 24 p., 3 appendices, 2 maps. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Reporters Damon Bickerstaff, F.H. Wilson
Last report date 5/13/1996