Unnamed (on southern Chilkat Peninsula)

Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Zn
Other commodities As; Pb; W
Ore minerals chalcopyrite; malachite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SK
Quadrangle map, 1:63,360-scale A-1
Latitude 59.12
Longitude -135.32
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at the head of a small bay on the eastern shore of the Chilkat Peninsula about 2.3 miles north of its southern tip. It is about 0.9 miles, S60E from VABM 1450 'Kal'. It is shown as number 41 on sheet 1 of Still and others (1991).

Geologic setting

Geologic description

Still and others (1991) indicate that this occurrence is located in metabasalt along a north-northwest-striking lineament that is likely a splay off the fault that runs through Flat Bay. Brecciated sphalerite-bearing basalt boulders up to 1 foot by 2 foot in size contained up to 6.23 ppm gold, 13 ppm silver, 27% zinc, 2,600 ppm copper, 13 ppm tungsten, and 50 ppm arsenic. Iron-stained metabasalt rubble crop with chalcopyrite, pyrite, and malachite in a quartz knot contained 0.446 ppm gold, 220 ppm zinc, and 8,400 ppm copper. A stream sediment sample 0.8 miles north of this site and along the same lineament contained 0.024 ppm gold, 1.5 ppm silver, 3,000 ppm zinc, 1,150 ppm copper, and 590 ppm lead. Plafker, Hudson, and Silberling (1979) and Plafker and Hudson (1980) note that metabasalts on the Chilkat Peninsula 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 nearby 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 (-135.321826250658, 59.1196735673692)
Mineral deposit model Base and precious metal mineralization localized along a lineament (shear zone?) in metabasalt. The metals have probably been derived from the host metabasalts.
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 localize 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).

Production and reserves

Indication of production None

Additional comments

This occurrence is within the Chilkat State Park.

References

MRDS Number 10308235

References

Lanphere, M.A., 1978, Displacement history of the Denali fault system, Alaska and Canada: Canadian Journal of Earth Sciences, v. 15, p. 817-822
Plafker, George, and Hudson, T., 1980, Regional implications of Upper Triassic metavolcanic and metasedimentary rocks on the Chilkat Peninsula, southeastern Alaska: Canadian Journal of Earth Sciences, v. 17, p. 681-689.
Reporters T.C. Crafford (T. Crafford & Associates, Anchorage)
Last report date 2/4/2001