Alamo

The Alamo is a silver, copper, and zinc 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: Alamo
Secondary: Glacier

Commodity

Primary: Silver
Primary: Copper
Primary: Zinc

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: Massive sulfide, Besshi (Japanese deposits)

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Locally conspicuous iron-staining.

Rocks

Name: Diorite
Role: Associated
Age Type: Associated Rock
Age Young: Pliocene

Analytical Data

Not available

Materials

Ore: Chalcopyrite
Ore: Pyrite
Ore: Pyrrhotite
Ore: Sphalerite
Gangue: Quartz

Comments

Comment (Reference): Primary Reference = Berg and others, 1977

Comment (Workings): Workings / Exploration = The deposit was located as the Glacier prospect in 1954 and explored by a small amount of trenching and some core drilling (Berg and others, 1977, p. 116-117). It was restaked in 1969 by another locator as the Alamo group of six claims. Exploration since the restaking included some stripping, several shallow trenches, and 5 diamond drill holes. Four of the holes reportedly were 180 feet long and one was 90 feet long. Two additional claims were located in 1973, but at that time no assay values or logs had yet been released for any of the drill holes. Although results of this private exploration have not been made public, sample values were unofficially reported to range from 0.25%-1.3% Cu in the limited areas sampled. Other unofficial reports described several drill-hole intersections of 18- to 27-foot-long zones containing more than 1% Cu (Berg and others, 1977, p. 120). Continuity of these intersections between holes is uncertain.? Twenty-six channel samples at several places along the deposit were collected by the U.S. Bureau of Mines in 1972 (Berg and others, 1977, p. 117-120). Assays of these samples showed up to 10% Cu and 2.1% Zn, along with as much as 75 ppm Pb, 50 ppm Ag, 15 ppm Mo, and, in one sample, 0.2 ppm Au. The results of this sampling indicate a large body of sulfide-bearing paragneiss containing 0.2%-0.7% Cu.

Comment (Deposit): Model Name = Metamorphosed Besshi massive sulfide? (Cox and Singer, 1986; model 24b)

Comment (Deposit): Other Comments = Prospect is in Misty Fiords National Monument Wilderness.

Comment (Geology): Geologic Description = The area of the Alamo prospect is underlain by a sequence of pelitic and quartzofeldspathic paragneiss, and minor dolomite marble that is part of a large metamorphic roof pendant in Tertiary or Cretaceous foliated granodiorite and quartz diorite of the Coast Range batholith (Berg and others, 1977, p. 117; Berg and others, 1988). The metamorphic sequence represents marine strata that underwent high-grade regional metamorphism in Cretaceous or Tertiary time. The premetamorphic age of the strata is uncertain, but they probably are mainly Paleozoic and may be as old as Precambrian (Berg and others, 1988, p. 26; Gehrels and others, 1990; Crawford and others, in press).? the deposit is a 75-foot-wide sulfide-bearing zone in paragneiss near the contact of foliated granodiorite (Berg and others, 1977, p. 117-120). The zone strikes northwest and dips northeast, parallel to the regional foliation of the country rocks. At an elevation of about 870 feet, the paragneiss contains a layer of dolomite marble about 18 feet thick. From 0-18 feet above the marble, the paragneiss contains small amounts of pyrite and subordinate chalcopyrite. The next nine feet contain sparse pyrite and a trace of chalcopyrite. The marble appears to be barren. Other parts of the deposit contain seams, patches, and disseminated grains of chalcopyrite and pyrrhotite. The richest material sampled by the U.S. Bureau of Mines in 1972 was a small lens of massive chalcopyrite and other sulfides, accompanied by some quartz and breccia, about 15 inches thick and 30 inches long (Berg and others, 1977, p. 120 and table 11, no. 2P025). Atomic absorption assays of this material showed 10% Cu, 0.2% Zn, 50 ppm Ag, and 0.2 ppm Au. The zinc content in this sample, and the zinc content in several samples collected elsewhere in the deposit, indicate that sphalerite also is present. Twenty-six channel samples at several places along the deposit were collected by the Bureau in 1972 (Berg and others, 1977, p. 117-120). Assays of these samples showed up to 10% Cu and 2.1% Zn, along with as much as 75 ppm Pb, 50 ppm Ag, 15 ppm Mo, and, in one sample, 0.2 ppm Au. The results of this sampling indicate a large body of sulfide-bearing paragneiss containing 0.2%-0.7% Cu.

References

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): Gehrels, G.E., McClelland, W.C., Samson, S.D., Patchett, P.J., and Jackson, J.L., 1990, Ancient continental margin assemblage in the northern Coast Mountains, southeast Alaska and northwest Canada: Geology, v. 18, p. 208-211.

Reference (Deposit): Crawford, M.L., Crawford, W.A., and Gehrels, G.E., 2000, Terrane assembly and structural relationships in the eastern Prince Rupert quadrangle, British Columbia, in H.H. Stowell and W.C.McClelland, eds., Tectonics of the Coast Mountains, southeastern Alaska and British Columbia: Boulder, Colorado, Geological Society of America Special Paper 343, p. 1-21.?

Reference (Deposit): Berg, H.C., Elliott, R.L., Smith, J.G., Pittman, T.L., and Kimball, A. L., 1977, Mineral resources of the Granite Fiords wilderness study area, Alaska, with a section on aeromagnetic data by Andrew Griscom: U.S. Geological Survey Bulletin 1403, 151 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.

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