Naginak Cove

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Mo
Other commodities Zn
Ore minerals chalcopyrite; pyrite
Gangue minerals chlorite

Geographic location

Quadrangle map, 1:250,000-scale UN
Quadrangle map, 1:63,360-scale B-3
Latitude 53.67
Longitude -166.83
Nearby scientific data Find additional scientific data near this location
Location and accuracy West and northwest side of Naginak Cove, off Anderson Bay on Unalaska Island. Anomalies no. 23 and 24 of Christie (1974).

Geologic setting

Geologic description

This site corresponds to two color anomalies as reported by Christie (1974). The first color anomaly is 4,000 ft (1,200 m) by 2,000 ft (600 m) in size and located on a gossan that occurs along the contact between granodiorite of the Shaler batholith and hornfelsed volcanic rocks of the Unalaska Formation (see Drewes and others, 1961). Christie (1974) reported that alaskite and granodiorite (including some aplite) dikes associated with the Shaler batholith are common; five or six 10 ft to 30 ft (3 to 9 m) wide dikes of which were mapped within this anomaly area. A stockwork of intense pyrite veining occurs in the vicinity of the dikes as do some quartz veins having sericite-pyrite envelopes occur. A feldspar porphyry dike(?) is reported as showing weak propylitic alteration. Only copper (mineral) seen was in a single piece of float in creek, it had chalcopyrite as fracture filling and pyrite-chalcopyrite as disseminations in the adjacent wall rock.
In a second area to the south of the above color anomaly, a triangular color anomaly 3,000 ft (900 m) north-south by 1,500 ft (450 m) east-west shows a clear relationship between a sulfide system and a quartz-eye porphyry dike. The color anomaly is cut off on the east by the sea, where it is widest and most intense. The dike narrows is divided into a number of narrow stringers in the west and widens to the east where it may grade into a feldspar (+/- quartz-eyes) porphyry. Alteration are most intense and sulfides are most common where the dike is widest on east. Pyrite occurs within the dike and the immediately adjacent wall rock as veins having envelopes of quartz sericite alteration. Chalcopyrite, pyrite, and chlorite occur in veins and disseminations less than 50 ft (15 m) from the dike contact. Christie (1974 mentions a mineralized zone 200 ft by 800 ft (61 m by 244 m) in maximum size and that most of the rock in this zone contains no chalcopyrite. It is not clear what the relationship of this mineralized zone has to other parts of the described color anomaly.
Fracturing is moderately intense in both areas.
Geologic map unit (-166.831876312066, 53.6691466823738)
Mineral deposit model Copper porphyry, epithermal gold vein
Mineral deposit model number 17, 25
Age of mineralization Miocene or younger
Alteration of deposit Quartz-sericite-pyrite and weak propylitic (pyrite-chlorite +/- epidote) alteration around quartz veins. Leaching is slight to moderate.

Production and reserves

Workings or exploration Reconnaissance geologic mapping and limited soil sampling. Two samples reported by Christie (1974) had 7 and 16 ppm molybdenum, 146 and 175 ppm copper, 84 and 290 ppm zinc, 1.8 and 2.1 ppm silver, and 0.03 and 0.05 ppm gold. In the southern part of the area, samples had concentrations ranging up to 16 ppm molybdenum, 510 ppm copper, 680 ppm zinc, 2.0 ppm silver, and 0.03 ppm gold.
Indication of production None

Additional comments

The analytical data from very limited sampling indicate further of evaluation of this area for epithermal gold veins is probably warranted.

References

MRDS Number A106023

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 5/20/1996