Red Shale

Occurrence, Inactive

Commodities and mineralogy

Main commodities Pb; Zn
Other commodities Cu
Ore minerals ferricrete oxide
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale C-4
Latitude 62.516
Longitude -154.776
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Red Shale occurrence is located in a low saddle along a north-south ridgeline about 3 kilometers west of VABM Lone; it is at an elevation of 1,475 feet (450 m) in the NE1/4 sec. 14, T. 28 N., R. 30 W., of the Seward Meridian. The reporter visited the site in 1982, 1992, and 1997.

Geologic setting

Geologic description

The Red Shale occurrence is a stratiform, ferricrete gossan interbedded with quartzite, algal limestone, and dolomite of probable Cambrian or Late Proterozoic (?) age (Wilson and others, 1998). The section is exposed near the axis of an upright anticline that is structurally uplifted in a horst. The ferricrete zone occurs mainly as rubble crop and talus in a poorly exposed, shallow water, dolomite-carbonate dominant sequence that is interpreted to be the oldest exposed part of the Nixon Fork subterrane in the McGrath quadrangle (Babcock and others, 1994; Decker and others, 1994).
The mineralized gossan strikes N15E, dips approximately 8E, ranges from 10 centimeters to 40 centimeters thick, and can be traced for about 140 meters along strike. Vegetation conceals the extensions of the mineralized area in both directions. Although poorly exposed, the mineralization is parallel to bedding. Minor late calcite incrustations were found in the ferricrete gossan.
Three chip-channel samples (82BT219, 82BT221, 82BT222) taken at equally-spaced intervals along the exposed strike of the gossan zone contain up to 62.60 percent iron, 231 ppm copper, 485 ppm lead, 169 ppm nickel, and 2,250 ppm zinc (T.K. Bundtzen, written communication, 1983). No sulfides were recognized.
Geologic map unit (-154.778275429633, 62.5153695767934)
Mineral deposit model Either Southeast Missouri Pb-Zn? or sedimentary exhalative lead-zinc? (Cox and Singer, 1986; model 32a or 31a).
Mineral deposit model number 32a or 31a
Age of mineralization Late Proterozoic or Cambrian if mineralization is syngenetic.
Alteration of deposit Strong ferricrete replacement of earlier sulfides.

Production and reserves

Workings or exploration Three chip-channel samples (82BT219, 82BT221, 82BT222) taken at equally spaced intervals along the exposed strike of the gossan zone contain up to 62.60 percent iron, 231 ppm copper, 485 ppm lead, 169 ppm nickel, and 2,250 ppm zinc (T.K. Bundtzen, written communication, 1983).
Indication of production None
Reserve estimates None.

References

MRDS Number 10307828

References

Decker, J., Bergman, S.C., Blodgett, R.B., Box, S.E., Bundtzen, T.K., Clough, J.G., Coonrad, W.L., Gilbert, W.G., Miller, M.L., Murphy, J.M., Robinson, M.S., and Wallace, W.K., 1994, Geology of southwestern Alaska, in Plafker, G. and Berg, H.C., eds., The Geology of Alaska: Geological Society of America DNAG, The Geology of North America, v. G-1, p. 285-310.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting)
Last report date 11/15/1998