Moth Bay

The Moth Bay is a zinc and lead mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Moth Bay
Secondary: Black Jack
Secondary: Bonanza King
Secondary: Lone Jack
Secondary: Sulphide
Secondary: Youzinka

Commodity

Primary: Zinc
Primary: Lead
Secondary: Copper
Secondary: Gold
Secondary: Silver

Location

State: Alaska
District: Ketchikan

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Sedimentary exhalative Zn-Pb

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Sphalerite
Ore: Pyrrhotite
Ore: Pyrite
Ore: Galena
Ore: Covellite
Ore: Chalcopyrite
Ore: Bornite
Gangue: Quartz
Gangue: Calcite

Comments

Comment (Deposit): Model Name = Stratiform massive sulfide replacement body. Possibly sedimentary exhalative Zn-Pb (Cox and Singer, 1986; model 31a)

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

Comment (Workings): 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).

Comment (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).

Comment (Reserve-Resource): 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).

Comment (Reference): Primary Reference = Robinson and Twenhofel, 1953

Comment (Geology): 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).

References

Reference (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.

Reference (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.

Reference (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.

Reference (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.

Reference (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.

Reference (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.

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