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Shellabarger Pass

Prospect in Alaska, United States with commodities Silver, Gold, Barium-Barite, Copper, Lead, Zinc
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Geologic information

Identification information

Deposit ID 10000903
MRDS ID A011558
Record type Site
Current site name Shellabarger Pass
Alternate or previous names Shellebarger Pass

Geographic coordinates

Geographic coordinates: -152.78978, 62.55256 (WGS84)
Relative position Reed and others (1978, locality 14) show these occurrences two miles north of Shellabarger Pass in the southwest quarter of Section 35, T.2 N. R. 19 W., of the Seward Meridian. Several massive sulfide bodies lie within 1/2 mile radius of this location.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Barium-Barite Primary
Copper Primary
Lead Primary
Zinc Primary

Materials information

Materials Type of material
Barite Ore
Chalcopyrite Ore
Galena Ore
Marcasite Ore
Pyrite Ore
Pyrrhotite Ore
Sphalerite Ore
Calcite Gangue
Dolomite Gangue
Quartz Gangue
Siderite Gangue

Alteration

  • (Local) Hydrothermal alteration (mineralogy unspecified) is extensive in the footwall but is rare to absent in hanging wall (Reed and Eberlein, 1972).

Mineral occurrence model information

Model code 91
USGS model code 24b
Deposit model name Massive sulfide, Besshi (Japanese deposits)
Mark3 model number 30

Host and associated rocks

  • Host or associated Associated
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Sedimentary Breccia
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Siltstone

Nearby scientific data

(1) -152.78978, 62.55256
ListMap

Comments on the geologic information

  • Geologic Description = Several massive sulfide bodies lie within 1/2 mile radius of this location. According to Reed and Eberlein (1972), the Shellabarger Pass volcanogenic massive sulfide (VMS) deposits are comprised of at least six individual bodies. The massive sulfide bodies are lenticular deposits with exposed dimensions on the order of 50 to 100 feet by 17 to 27 feet, composed of 60% sulfides in a very fine grained mixture of pyrite, marcasite, sphalerite, chalcopyrite, galena and pyrrhotite. Sphalerite, chalcopyrite and galena make up about 15% of total sulfides. Some areas of heavily disseminated sulfides are localized along shear zones. Sulfide minerals are intergrown with the gangue minerals siderite, calcite, quartz, and dolomite. Sulfides and gangue occur in massive, lenticular sulfide bodies, as replacements of carbonate-rich beds, and as fracture fillings, mainly in chert and siltstone. Main sulfide bodies may be proximal to basaltic flow fronts. Regionally the basalt has high background copper values of 200 to 300 ppm. ? the grade of the massive bodies averages 1 to 1.5% copper, 0.8 to 1.7% zinc, 0.9 to 2.4 oz/ton silver and less than 0.5% lead. Gold content varies from 0.0006 to 0.15 oz/ton. The sulfide bodies tend to be zoned, with highest chalcopyrite concentrations in basal parts and minor sphalerite in or near hanging walls (Reed and Eberlein, 1972; Nokleberg and others, 1994). ? Hydrothermal alteration is extensive in the footwall but is rare to absent in hanging wall (Reed and Eberlein, 1972).? Indicated tonnage of known bodies is on the order of 50,000 tonnes (Reed and Eberlein, 1972). Nokleberg and others (1994) report an estimated several hundred thousand tonnes of unknown grade.? the host rocks are interpreted to be part of the Mystic terrane, a displaced fragment of the late Paleozoic and early Mesozoic North American Cordillera continental margin (Reed and Nelson, 1980; Decker and others, 1994; Nokleberg and others, 1994). The deposits occur in a north-trending structural trough of Triassic to Jurassic marine sediments and mafic volcanics (hypersthene normative tholeiites that includes pillow basalt, agglomerate, and breccia) in a eugeoclinal sequence which rests unconformably over Paleozoic sedimentary rocks consisting of interbedded chert, dolomite, siltstone, shale, volcanic graywacke, and basaltic aquagene tuff (Bundtzen and Gilbert, 1983; Reed and Nelson, 1980). ? It is unclear whether the deposits are hosted in Paleozoic or Mesozoic rocks. There is evidence to suggest the volcanic host rocks are either upper Triassic (Norian?) or latest Devonian-earliest Mississippian. Bundtzen and Gilbert (1983) suggest that the host rocks to the Shellabarger VMS deposits could be Late Triassic. Bundtzen and others (1997) report Late Triassic fossils in from a sedimentary/basalt sequence in the Mystic terrane to the north and east in the adjacent McGrath quadrangle. Reed and Nelson (1980) consider the basalts to be post-Late Devonian age (possibly Mississippian), indicated by distinctive spherical concretions of fluoroapatite present in sedimentary breccia and conglomerate that apparently underly the pillow basalt at Shellabarger Pass. The source of the concretions is considered to be a phosphatic chert unit that overlies the Middle and Upper Devonian limestone. A nearby pillow basalt occurs in a chaotic sequence of sedimentary rocks that contains fossils of late Middle Devonian(?) (Reed and Nelson, 1980).
  • Age = Triassic or Jurassic (Nokleberg and others, 1987, p. 48; Nokleberg and others,1994, p. 877) or latest Devonian-earliest Mississippian (Reed and Nelson, 1980).

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Both metallic and non-metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Yentna

Comments on the reserve resource information

  • Reserves = Indicated tonnage of known bodies is on the order of 50,000 tonnes (Reed and Eberlein, 1972). Nokleberg and others (1994) report an estimated several hundred thousand tonnes of unknown grade.

Comments on the workings information

  • Workings / Exploration = Reconnaissance mapping, stream silt and rock sampling are all that has been published on this property. Private concerns have held the property at various times in the past and may have completed a more detailed evaluation, the results of which are not publicly available.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A011558
USGS Alaska Resource Data File ARDF TL018

Bibliographic references

  • Deposit

    Reed, B.L. and Eberlein, G.D., 1972, Massive sulfide deposits near Shellabarger Pass, southern Alaska Range, Alaska: U.S. Geological Survey Bulletin 1342, 43 p.

  • Deposit

    MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000.

  • Deposit

    C.C. Hawley and Associates, Inc., 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska: U.S. Bureau of Mines Open-File Report 24-78, 275 p., 7 plates.

  • Deposit

    Reed, B.L., Nelson, S.W., Curtin, G.C., and Singer, D.A., 1978, Mineral resources map of the Talkeetna Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-870-D, 1 sheet, scale 1:250,000.

  • Deposit

    Cobb, E.H., and Reed, B.L., 1980, Summaries of data and lists of reference to metallic and selected nonmetallic mineral deposits in the Talkeetna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-884, 106 p.

  • Deposit

    Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, scale 1:250,000.

  • Deposit

    Bundtzen, T.K., and Gilbert, W.G., 1983, Outline of geology and mineral resource of upper Kuskokwim region, Alaska: Alaska Geological Society 1982 Symposium on Western Alaska, v. 3, p. 101-117.

  • Deposit

    Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p.

  • 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

    Nokleberg, W.J., and others, 1994, Metallogeny and major mineral deposits of Alaska and Metallogenic map of significant metalliferous lode deposits and placer districts of 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. G1, p. 855-904 and v. G1, Plate 11, scale 1:2,500,000.

  • Deposit

    Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 pages, one sheet, scale 1:125,000.

  • Deposit

    Clark, A.L., and Cobb, E.H., 1972, Metallic mineral resources map of the Talkeetna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-369, 1 sheet, scale 1:250,000.

Comments on the references

  • Primary Reference = Reed and Eberlein, 1972

General comments

Subject category Comment text
Deposit Model Name = Besshi massive sulfide (Cox and Singer, 1986; model 24b).
Deposit Other Comments = In the past over 300 mining claims have been held in this area.

Reporter information

Type Date Name Affiliation Comment
Reporter 10-AUG-1998 Madelyn A. Millholland Millholland & Associates