Red Shale

Occurrence in Alaska, United States with commodities Lead, Zinc, Copper

Geologic information

Identification information

Deposit ID 10307828
Record type Site
Current site name Red Shale

Geographic coordinates

Geographic coordinates: -154.77888, 62.51546 (WGS84)
Relative position 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.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Lead Primary
Zinc Primary
Copper Secondary

Materials information

Materials Type of material
Calcite Gangue
Quartz Gangue

Alteration

  • (Local) Strong ferricrete replacement of earlier sulfides.

Mineral occurrence model information

Model code 224
USGS model code 32a
BC deposit profile E12
Deposit model name Mississippi Valley, S.E. Missouri Pb-Zn
Mark3 model number 42
Model code 208
USGS model code 31a
BC deposit profile E14
Deposit model name Sedimentary exhalative Zn-Pb
Mark3 model number 13

Nearby scientific data

(1) -154.77888, 62.51546

Comments on the geologic information

  • 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.
  • Ore Material = Ferricrete oxide
  • Age = Late Proterozoic or Cambrian if mineralization is syngenetic.

Economic information

Economic information about the deposit and operations

Development status Occurrence

Comments on exploration

  • Status = Inactive

Mining district

District name McGrath

Comments on the workings information

  • Workings / 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).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF MG011

Bibliographic references

  • Deposit

    Babcock, L.E., Blodgett, R.B., and St. John, James, 1994, New Late(?) Proterozoic age formations in the vicinity of Lone Mountain, McGrath quadrangle, Alaska, in Till, A.B., and Moore, T.E., eds., Geological studies in Alaska by the U.S. Geological Survey, 1993: U.S. Geological Survey 2107, p. 143-156.

  • Deposit

    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: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G-1, p. 285-310.

  • Deposit

    Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of central (interior) Alaska: U.S. Geological Survey Open-File Report 98-133, 17 p., 2 sheetsm, scale 1:500,000.

Comments on the references

  • Primary Reference = This description

General comments

Subject category Comment text
Deposit Model Name = Uncertain; either Southeast Missouri Pb-Zn (?) or sedimentary exhalitive lead-zinc (Cox and Singer, 1986; model 32a or 31a).

Reporter information

Type Date Name Affiliation Comment
Reporter 15-NOV-98 T.K. Bundtzen Pacific Rim Geological Consulting