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

Geologic information

Identification information

Deposit ID 10000276
MRDS ID A010319
Record type Site
Current site name Halobia

Geographic coordinates

Geographic coordinates: -133.25994, 56.67168 (WGS84)
Relative position The locality is in the intertidal zone at the mouth of a small creek that enters the northern of the large shallow bay at the mouth of the Castle River; the site is in the NE1/4 section 15, T. 60 S., R. 77E. The locality as seen in 1996 was about 250 feet downstream from a log jam at the high tide mark on the creek. Massive sulfide lenses occur in the center of the creek bed but they are not conspicuous. Location of prospect is to within a few yards. Locality 30 of Grybeck, Berg, and Karl (1984).
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Geographic areas

Country State
United States Alaska


Commodity Importance
Silver Primary
Lead Primary
Zinc Primary
Arsenic Secondary
Barium-Barite Secondary
Copper Secondary

Materials information

Materials Type of material
Galena Ore
Pyrite Ore
Sphalerite Ore


  • (Local) None.

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 Host
    Rock type Metamorphic Rock > Phyllite
    Stratigraphic age (youngest) Late Triassic

Nearby scientific data

(1) -133.25994, 56.67168

Comments on the geologic information

  • Geologic Description = Thin lenses of massive sulfides occur in siliceous phyllite that is intercalated with fossiliferous , Upper Triassic, black carbonaceous phyllite; locally garnet-bearing limestone; siltstone; and silvery dark gray muscovite- and quartz-rich phyllite (Berg and Grybeck, 1980; Berg, 1981). The carbonaceous phyllite contains abundant pyrite. The massive sulfide lenses are in several zones 10-12 feet wide and 80-100 feet long. Individual lenses within these zones are up to 1 foot wide and 3 feet long; they contain abundant pyrite and up to 5% galena and sphalerite. Analyses of grab samples show up to 100 ppm Cu, 100 ppm Ag, and 1000 ppm As. Several examples of the fossil Halobia collected in rocks interbedded with the sulfide lenses at the deposit unambiguously date the deposit as Late Triassic. Unpublished work by industry indicated more examples of similar deposits have been found in the claims staked northwest of this prospect (see 'Workings/Description' field ). The deposit is part of the Triassic Duncan Canal-Zarembo Canal belt of dismembered, volcanogenic massive-sulfide deposits described by Berg and Grybeck (1980) and Berg (1981).? Brew (1997 [OF 97-156-J]) indicates that the deposit is in a sliver of Triassic Hyd Group rocks that consist mainly of phyllite and slate with minor conglomerate, limestone and sandstone. However, the Hyd Group rocks are surrounded by a large, poorly-exposed area of undated phyllite, slate, and minor conglomerate, limestone, and quartzite to which Brew assigns a Mesozoic age. This unit is largely covered by vegetation and probably includes substantial additional Triassic Hyd Group rocks that may contain similar deposits. Recent mapping (Sue Karl, oral communication, 1998) indicates that Brew's Mesozoic unit also may include argillite and volcanic graywacke of the Mississippian and Permian Cannery Formation. Also see PE024 which is probably of similar origin if not a continuation of this site.
  • Age = Unambiguously Late Triassic as defined by the occurrence of the fossils of Halobia at the site.

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Active

Mining district

District name Kupreanof

Comments on the production information

  • Production Notes = None

Comments on the reserve resource information

  • Reserves = None

Comments on the workings information

  • Workings / Exploration = Originally found by the U. S. Geological Survey in 1979 (Berg and Grybeck, 1980). Nine lode claims staked on the deposit in 1979; by 1995, a considerable block of ground several square miles in area was staked on and northwest of the original discovery (Department of Natural Resources unpublished Kardex mining claim information system). Informal discussions with industry geologists who worked in the area indicate that they have identified several to numerous additional occurrences of similar deposits on these claims. (The latitude and longitude of this site are the location of the original discovery.) An aerial examination of the area in 1996 indicated no obvious signs of surface exploration in the vicinity. In 1998, there was renewed interest in the area encouraged by the geophysical surveys the State of Alaska flew over the area in 1997.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A010319
USGS Alaska Resource Data File ARDF PE025

Bibliographic references

  • 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 C-4 quadrangle, southeastern Alaska: U.S. Geological Survey Open-File Report 97-156-J, 21 p., 1 sheet, scale 1:63,360.

Comments on the references

  • Primary Reference = Berg and Grybeck, 1980; this description

General comments

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