Unnamed (north of mouth of Castle River)

Occurrence, Active

Commodities and mineralogy

Main commodities Ag; Ba; Cu; Pb; Zn
Ore minerals pyrite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale PE
Quadrangle map, 1:63,360-scale C-4
Latitude 56.6664
Longitude -133.2596
Nearby scientific data Find additional scientific data near this location
Location and accuracy The coordinates are at the center of an area of mineralized outcrops that occur discontinuously just above the high tide line for about a half mile along the west shore of the large shallow bay at the mouth of the Castle River. The site is locality 29 of Grybeck, Berg, and Karl (1984) and this may be a continuation of the mineral occurrence at PE025 just to the northeast.

Geologic setting

Geologic description

Outcrops of phyllitic, light greenish gray to cream, felsic metatuff intercalated with muscovite-rich siliceous phyllite occur discontinuously just above the high tide line for about a half mile along the edge of a large shallow bay. The metatuff locally contains massive-sulfide layers up to 6 feet thick with abundant pyrite and sparse sphalerite(?) (Grybeck, Karl, and Berg, 1984). Grab samples of the massive sulfide layers and felsic metatuff show up to 700 parts per million (ppm) lead, 350 ppm zinc, 10 ppm silver, and 2,000 ppm barium. These outcrops may be a continuation of the mineralized occurrence at PE025 just to the northeast. This is probably the locality noted by Buddington (1923) that he described as a pyrite layer about 4 feet wide exposed for 50 feet. Recent mapping by Karl and others (1999) indicates that these outcrops are part of the Hyd Group of Triassic age.
This occurrence was covered by a large block of claims staked by Pacific Alaska Resources Co in the late 1980s and early 1990s; the company planned to drill to test several geochemical anomalies in copper, zinc, and silver but apparently did not follow through. Still and others (2002) sampled several of these lenses; their samples contained up to 31.8 ppm silver, 1,304 ppm lead, 1.7 percent zinc, and 1,268 ppm arsenic.
Geologic map unit (-133.261334854749, 56.6660592279908)
Mineral deposit model Kuroko massive-sulfide deposit model (Cox and Singer, 1986, model 28a); alternately a Sierran Kuroko deposit (Bliss, 1992; 28a.1).
Mineral deposit model number 28a or 28a.1
Age of mineralization Late Triassic based on the age of the host rock.

Production and reserves

Workings or exploration In 1979, nine lode claims were staked in the area that probably covered this deposit. By 1995, a considerable block of ground several square miles in area was staked on and northwest of this site and PE025. Informal discussions with industry geologists who worked in the area indicate that they found several to numerous additional occurrences of similar deposits on these claims (D.J. Grybeck, oral communication, 1996). An aerial examination of the area in 1996 indicated no obvious signs of surface exploration. In 1998, there was renewed interest in the area encouraged by the geophysical surveys the State of Alaska had flown over the area.
Indication of production None

References

References

Reporters D.J. Grybeck (Port Ludlow, WA)
Last report date 4/8/2007