Unnamed (near the north end of Shikosi Island)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Cu; Zn
Other commodities Au
Ore minerals chalcopyrite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale A-1
Latitude 59.04
Longitude -135.27
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is about 0.15 miles south of the narrow northern tip of Shikosi Island.

Geologic setting

Geologic description

Still and others (1991) describe this occurrence as, 'A narrow epidotized and silicified shear zone that contains chalcopyrite and chalcopyrite hosted in metabasalt.' Samples contained up to 0.05 ppm gold, 6.7 ppm silver, 3,000 ppm zinc, and 2.74% copper. This zone is similar to the unnamed occurrence (SK001) to the south on Kataguni Island. Plafker, Hudson, and Silberling (1979) and Plafker and Hudson (1980) note that on the Chilkat Peninsula the same metabasalts are vesicular and/or amygdaloidal and that well-developed pillow textures are locally present. Based in part on fossil evidence that supports a Late Triassic (Karnian) age, they suggest that the metavolcanics and carbonates may correlate with similar rocks of the Wrangellia terrane. The age of the mineralization is not well established, but can be no older than the Late Triassic age of the host rocks. If the structure that localizes the mineralization is related to the Chilkat Fault, then the age of the mineralization is probably Tertiary or younger as most movement on the Chilkat Fault has been post-Mesozoic (Lanphere, 1978).
Geologic map unit (-135.271826954501, 59.0396722327485)
Mineral deposit model Very little information. Base and precious metal mineralization localized along a shear zone in metabasalt.
Age of mineralization The age of this occurrence is not well established, but can be no older than the Late Triassic age of the host rocks (Plafker, Hudson and Silberling, 1979; Plafker and Hudson, 1980). If the structure that localizes the mineralization is related to the Chatham Strait Fault, then the age of the mineralization is probably Tertiary or younger as most movement on the Chilkat Fault has been post-Mesozoic (Lanphere, 1978).
Alteration of deposit Epidotization, silicification.

Production and reserves

Indication of production None

Additional comments

This occurrence is within the Chilkat Islands, State Marine Park.

References