Moth Bay

Prospect in Alaska, United States with commodities Lead, Zinc, Silver, Gold, Copper

Geologic information

Identification information

Deposit ID 10001583
MRDS ID A012336
Record type Site
Current site name Moth Bay
Alternate or previous names Black Jack, Bonanza King, Lone Jack, Sulphide, Youzinka
Related records 10234290

Geographic coordinates

Geographic coordinates: -131.34482, 55.29586 (WGS84)
Relative position The Moth Bay prospect is at an elevation of 300-350 feet, 0.55 mile north of the head of Moth Bay. The site is in section 7, T. 76 S., R. 93 E., of the Copper River Meridian. It corresponds to loc. 83 in Elliott and others (1978), and to loc. 307 in Maas and others (1995). The location is accurate within a few hundred feet.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Lead Primary
Zinc Primary
Silver Secondary
Gold Secondary
Copper Secondary

Materials information

Materials Type of material
Bornite Ore
Chalcopyrite Ore
Covellite Ore
Galena Ore
Pyrite Ore
Pyrrhotite Ore
Sphalerite Ore
Calcite Gangue
Quartz Gangue

Mineral occurrence model information

Model code 208
USGS model code 31a
BC deposit profile E14
Deposit model name Sedimentary exhalative Zn-Pb
Mark3 model number 13

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite
  • Host or associated Host
    Rock type Metamorphic Rock > Schist

Nearby scientific data

(1) -131.34482, 55.29586

Comments on the geologic information

  • Geologic Description = The principal country rock in this part of Revillagigedo Island is a stock of Cretaceous quartz diorite (Berg and others, 1988). On the north and south, the stock intrudes diverse metamorphosed Mesozoic or Paleozoic sedimentary, volcanic, and intrusive rocks. In part, the southern boundary of the stock also is a moderately northeast-dipping thrust fault and blastomylonite zone (Berg, 1982). The outcrop area of the stock includes roof pendants and inclusions of dioritic metaplutonic rocks and pelitic metasedimentary rocks. Berg and others (1988) assigned these rocks a Mesozoic or Paleozoic premetamorphic age. One such pelitic roof pendant, 0.5 mile long and 0.25 mile wide, hosts the Moth Bay deposit.? the Moth Bay deposit consists of layers of biotite schist and underlying muscovite schist that are partly replaced by pyrite, pyrrhotite, sphalerite, chalcopyrite, galena, and minor bornite and covellite, accompanied by interstitial quartz and calcite (Robinson and Twenhofel, 1953, p. 59-71). Locally, the sulfide minerals form isolated, podlike masses of ore. The deposit crops out in an area at least 1500 feet long and 700 feet wide. The ore beds are as much as 15 feet thick, but generally no more than 5 feet thick. The principal ore bed ranges from 2-17 feet thick; it has been traced on the surface for 600 feet and in underground workings for 440 feet. The orebody has a vertical extent of 200 feet and a downdip length of 140 feet. A second ore bed averages 4 feet thick for a length of 80 feet. A third ore bed of unknown length is up to 3 feet thick and occurs on the crest of a southeast-plunging anticlinal drag fold in the schist hostrock. The order of abundance of the sulfide minerals is: 25% pyrite, up to 10% pyrrhotite, 3-15% sphalerite, 1-5% chalcopyrite, and trace galena. Gold and silver have been reported only in some assays of the ore.? the deposit was explored between about 1911 and 1931 by trenches, pits, and about 900 feet of underground workings, including an 800-foot adit and short crosscuts, and a 75-foot adit and 100-foot inclined winze (Robinson and Twenhofel, 1953; Maas and others, 1995, p. 221). The deposit was drilled by the U.S. Bureau of Mines in 1950 (see Reserves).

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Ketchikan

Comments on the production information

  • Production Notes = Despite fairly extensive underground workings, there is no public record of any ore shipments from the Moth Bay prospect.

Reserves and resources

  • Type In-situ
    Estimate year 1953
    Remarks Entry carried over from Old MRDS or added later (i.e. it did not originate in ARDF)
    Commodity Subtype Grade units Group Importance Year
    Zinc Zn 7.5 wt-pct Zinc Major 1953
    Copper Cu 1 wt-pct Copper Major 1953
  • Type In-situ
    Estimate year 1953
    Remarks Entry carried over from Old MRDS or added later (i.e. it did not originate in ARDF)
    Commodity Subtype Grade units Group Importance Year
    Zinc Zn 2 wt-pct Zinc Major 1953
    Copper Cu 0.5 wt-pct Copper Major 1953

Comments on the reserve resource information

  • Reserves = Drilling of the Moth Bay deposit by the U.S. Bureau of Mines in 1950 indicated: (1) about 100,000 tons of ore containing 7.5% Zn, 1% Cu, and 0.02 ounce of Au and 0.20 ounce of Ag per ton; (2) 10,000 tons of ore containing 3% Cu; and (3) an additional 100,000 tons of lower-grade ore (Robinson and Twenhofel, 1953; Cobb and Elliott, 1980, p. 77; Maas and others, 1995, p. 221).

Comments on the workings information

  • Workings / Exploration = The deposit was explored between about 1911 and 1931 by trenches, pits, and about 900 feet of underground workings, including an 800-foot adit and short crosscuts, and a 75-foot adit and 100-foot inclined winze (Robinson and Twenhofel, 1953; Maas and others, 1995, p. 221). The deposit was drilled by the U.S. Bureau of Mines in 1950 (see Reserves).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012336
USGS Alaska Resource Data File ARDF KC086

Bibliographic references

  • Deposit

    Robinson, G.D., and Twenhofel, W.S., 1953, Some lead-zinc and zinc-copper deposits of the Ketchikan and Wales districts, Alaska: U.S. Geological Survey Bulletin 998-C, p. 59-84.

  • Deposit

    Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 p., scale 1:250,000.

  • Deposit

    Cobb, E.H., and Elliott, R.L., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1053, 154 p.

  • Deposit

    Berg, H.C., 1982, The Alaska Mineral Resource Assessment Program; guide to information about the geology and mineral resources of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Circular 855, 24 p.

  • Deposit

    Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

  • Deposit

    Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.

Comments on the references

  • Primary Reference = Robinson and Twenhofel, 1953

General comments

Subject category Comment text
Deposit Model Name = Stratiform massive sulfide replacement body. Possibly sedimentary exhalative Zn-Pb (Cox and Singer, 1986; model 31a)
Deposit Other Comments = Robinson and Twenhofel (1953) provide detailed drill core and assay data for this deposit. At various times, the property has been called Black Jack, Bonanza King, Lone Jack, Sulphide, and Youzinka (Cobb and Elliott, 1980, p. 144-146).

Reporter information

Type Date Name Affiliation Comment
Reporter 03-JUL-99 H.C. Berg U.S. Geological Survey