Unnamed (west of the Middle Fork Chandalar River)

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

Geologic information

Identification information

Deposit ID 10001726
MRDS ID A012510
Record type Site
Current site name Unnamed (west of the Middle Fork Chandalar River)

Geographic coordinates

Geographic coordinates: -147.81335, 68.04976 (WGS84)
Relative position Site is at an elevation of about 3,800 ft. in the upper part of a small drainage approximately 2 miles west of the Middle Fork Chandalar River and about 6 miles south of the confluence of Beaucoup Creek and Middle Fork Chandalar River (SE1/4 sec. 18, T. 16 S., R. 19 E., of the Umiat Meridian). Location accurate within 1/4-mile radius.
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Geographic areas

Country State
United States Alaska


Commodity Importance
Lead Primary
Zinc Primary
Silver Secondary
Copper Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Galena Ore
Pyrite Ore
Sphalerite Ore
Tetrahedrite Ore
Quartz Gangue

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

Host and associated rocks

  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Pyroclastic Rock > Volcanic Breccia (Agglomerate)
    Rock unit name Skajit Limestone;Beaucoup Formation; Brown Shale Member
    Rock description Skajit Limestone;Beaucoup Formation; Brown Shale Member

Nearby scientific data

(1) -147.81335, 68.04976

Comments on the geologic information

  • Geologic Description = One of two mineralized areas with small outcrops within which lead-zinc-silver-(copper?) mineralization is found (Detra, 1977). Sphalerite, galena and pyrite are found in crosscutting veins in a chert breccia with quartz veins. Samples from the veins are reported to contain galena, sphalerite and chalcopyrite as well as iron sulfides. An analysis of mineralized material returned a value of 34 percent Zn and 70 ppm Ag (Detra, 1977). Exposures of mineralization are less than 3 meters in length and not much wider than the streams (approximately 1 to 2 meters) in which they are exposed. The mineralization is described as occurring in a chert cap at an unconformable paleokarst surface at the top of the Devonian Skajit Limestone at the base of a 1,200-meter-thick Frasnian fine clastic marine sequence (Dutro, 1978). This marine sequence grades upward from basal black shales and dark laminated limestones through cycles of fine clastics and into reef limestones. The clastics contain volcaniclastics and mafic volcanic rocks. The overlying clastics are yellow-weathering phyllitic shales and sandstones, which in turn are overlain by black shales of the Hunt Fork Shale. This is purportedly the only carbonate-hosted prospect in Alaska genetically linked to a karst or paleokarst event (Schmidt, 1997). The surrounding area is mapped as Devonian shale, sandstone and conglomerate with scattered bodies of mafic rocks of uncertain age.

Economic information

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Chandalar

Comments on the workings information

  • Workings / Exploration = Two blocks of claims staked in 1977 (19 by Noranda, 6 by RAA). Semi-quantitative spectrographic data for sample 76ARR46 (Detra, 1977, Table 1): Ag (70 ppm), Cu (1,000 ppm), Pb (3,000 ppm), Sb (700 ppm), Zn (greater than 20,000 ppm); Zn by wet chemical analysis (340,000 ppm).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012510
USGS Alaska Resource Data File ARDF PS006

Bibliographic references

  • Deposit

    Cathrall, J.B., Cooley, E.F., Detra, D.E., and O'Leary, R.M., 1977, A listing and statistical summary of spectrographic and chemical analysis of stream-sediment and rock samples from the Philip Smith Mountains quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-244, 79 p.

  • Deposit

    Detra, D.E., 1977, Delineation of an anomalous lead-zinc area in the Philip Smith Mountains A-2 quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-223, 11 p.

  • Deposit

    Barker, J.C., 1978, Mineral Investigations of certain lands in the eastern Brooks Range: a summary report: US Bureau of Mines Open-File No. 63-78

  • Deposit

    Dutro, J.T., Jr., 1978, Potential stratabound lead-zinc mineralization, Philip Smith Mountains quadrangle, Alaska, in Johnson, K. M., ed., The United States Geological Survey in Alaska, Accomplishments during 1977: U.S. Geological Survey Circular 772-B, p. B9-B11.

  • Deposit

    Menzie, W.D., Reiser, H.N., Brosgi, W.P., and Detterman, R.L., 1985, Map showing distribution of mineral resources (excepting oil and gas) in the Philip Smith Mountains quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Investigations Map MF-879-C, 2 sheets, scale 1:250,000.

  • Deposit

    Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.

  • Deposit

    Maas, K.M., 1987, Availability of land for Mineral exploration and development in northern Alaska, 1986: U.S. Bureau of Mines Special Publication, 34 p., 33 sheets.

Comments on the references

  • Primary Reference = Detra, 1977

General comments

Subject category Comment text
Deposit Model Name = Mississippi Valley Zn-Pb (?) (Cox and Singer, 1986; model 32a).
Deposit Other Comments = See also locations PS007 and PS008. Area has potential for stratabound lead-zinc deposits.

Reporter information

Type Date Name Affiliation Comment
Reporter 17-NOV-1999 J.M. Britton U.S. Geological Survey