Frenchie

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

Geologic information

Identification information

Deposit ID 10096765
MRDS ID A010320
Record type Site
Current site name Frenchie
Alternate or previous names BP Adit

Geographic coordinates

Geographic coordinates: -132.95492, 56.41863 (WGS84)
Relative position Prospect is at an elevation of less than 100 feet on the south bank of an unnamed creek on NW Zarembo Island, about one-half mile south of the head of St. John Harbor. Location of prospect known to within 100 yards in the SE1/4, section 8, T. 63 S., R. 80 E. Localities 59 and 60 of Grybeck, Berg, and Karl (1984).
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Geographic areas

Country State
United States Alaska

Commodities

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

Materials information

Materials Type of material
Galena Ore
Pyrite Ore
Sphalerite Ore

Alteration

  • (Local) Host Rock Is Rhyolite Tuff (?) Altered To Phyllite And Schist

Mineral occurrence model information

Model code 184
USGS model code 28a
Deposit model name Massive sulfide, kuroko
Mark3 model number 93
Model code 187
USGS model code 28a.1
Deposit model name Massive sulfide, Sierran kuroko
Mark3 model number 44

Host and associated rocks

  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Intermediate Volcanic Rock > Andesite
    Stratigraphic age (youngest) Pliocene
  • Host or associated Host
    Rock type Sedimentary Rock > Carbonate > Limestone

Nearby scientific data

(1) -132.95492, 56.41863

Comments on the geologic information

  • Geologic Description = Although first described as a gold prospect by Buddington in 1923, this prospect remained largely unrecognized as a volcanogenic massive-sulfide deposit until work by the USGS in the early 1980's relocated the prominent outcrop along the creek bank that consists mainly of thick layers of pyrite (Berg and Grybeck, 1980; Berg, 1981; Grybeck, Berg, and Karl, 1984). The pyrite zone has an aggregate thickness of about 15 feet and extends for at least 600 feet along the creek bank. One layer about 4 feet thick consists of 50-75% massive sulfides in a siliceous matrix. The sulfides are chiefly pyrite, accompanied by minor sphalerite, chalcopyrite, and galena that form lenses, bands, and knots in the massive pyrite. Grab samples of the massive pyrite layer show 0.20 to 5.50 ppm Au, up to 2% Cu, 1% Zn, 1% Pb, 20 ppm Ag, and more than 5000 ppm Ba. The massive pyrite layers are interbedded with reddish and greenish gray siliceous metavolcanic rocks. The footwall is muscovite phyllite and minor black limestone; the hanging wall is light greenish gray phyllitic to schistose rhyolite tuff(?). All are intruded by Tertiary(?) andesite dikes. Interpreted by Berg and Grybeck (1980) and Berg (1981) as a Triassic volcanogenic massive-sulfide deposit, one of several in a belt that extends along Duncan Canal to Zarembo Island. ? Regional mapping by Brew (1997 [OF 97-156-E]) and more recent mapping by Karl (oral communications, 1998) confirm that the prospect is in rocks of the Triassic Hyd Group that contain the volcanogenic massive sulfide deposits of the Duncan-Zarembo mineral belt.
  • Age = Late Triassic as part of the Duncan-Zarembo mineral belt defined by Berg and Grybeck (1980) and Berg (1981).

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Active

Mining district

District name Petersburg

Comments on the production information

  • Production Notes = None

Comments on the workings information

  • Workings / Exploration = Although first described in 1923, it was largely forgotten prior to 1980. Since then, the property has repeatedly been staked and drilled by industry. A block of 34 claims roughly centered on the prospect staked in 1978; these claims were active through at least 1982, and these or other claim blocks probably have been active since. The property has been drilled several times since then, most recently by Westmin Resources in 1996.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A010320
USGS Alaska Resource Data File ARDF PE058

Bibliographic references

  • Deposit

    Buddington, A.F., 1923, Mineral deposits of the Wrangell district; U.S. Geological Survey Bulletin 739, p. 51-75.

  • Deposit

    Berg, H. C., and Grybeck, Donald, 1980, Upper Triassic volcanogenic Zn-Pb-Ag (-Cu-Au) mineral deposits near Petersburg, Alaska: U.S. Geological Survey Open-File Report 80-527, 11 p., 1 oversize sheet.

  • Deposit

    Berg, H.C., 1981, Upper Triassic volcanogenic massive sulfide metallogenic province identified in southeastern Alaska, in Albert, N.R.D., and Hudson, T.L., eds., The United States Geological Survey in Alaska: accomplishments during 1979: U.S. Geological Survey Circular 823-B, p. B104-B108.

  • Deposit

    Grybeck, D.J., Berg, H.C., and Karl, S.M., 1984, Map and description of the mineral deposits in the Petersburg and eastern Port Alexander quadrangles: U.S. Geological Survey Open-File Report 84-837, 86 p., 1 sheet, scale 1:250,000.

  • Deposit

    Brew, D.A., 1997, Reconnaissance geologic map of the Petersburg B-3 quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-E, 21 p., 1 sheet, scale 1:63,360.

Comments on the references

  • Primary Reference = Grybeck, Berg, and Karl, 1984

General comments

Subject category Comment text
Deposit Model Name = Kuroko volcanogenic massive sulfide deposit (Singer and Cox, 1986; model 28a ), or Sierran Kuroko volcanogenic massive sulfide deposit (Bliss, 1992; model 28a1)

Reporter information

Type Date Name Affiliation Comment
Reporter 01-NOV-1998 H.C. Berg U.S. Geological Survey
Reporter 01-NOV-1998 D.J. Grybeck U.S. Geological Survey