Black Mountain

Site Name

Primary: Black Mountain

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Commodity

Primary: Tin

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Location

State: Alaska
District: Port Clarence

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

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

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Physiography

Not available

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Mineral Deposit Model

Model Name: Sn skarn

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Text: Calc-silicate hornfels and tactite development is common; late quartz-fluorite +/- tourmaline veining and alteration is present along faults and fractures

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Cassiterite
Ore: Galena
Ore: Sphalerite
Gangue: Tourmaline
Gangue: Quartz
Gangue: Plagioclase
Gangue: Idocrase
Gangue: Garnet
Gangue: Fluorite
Gangue: Epidote
Gangue: Diopside
Gangue: Wollastonite

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Comments

Comment (Geology): Age = Late Cretaceous; the Black Mountain biotite granite, interpreted to be linked to alteration and mineralization in this area, has been determined to be 79.1 +/- 2.9 my old by the K/Ar method (Hudson and Arth, 1983, p. 769).

Comment (Exploration): Status = Inactive

Comment (Deposit): Model Name = Tin skarn (Cox and Singer, 1986; model 14b).

Comment (Workings): Workings / Exploration = Some reconnaissance rock geochemistry and traverse geology, regional gravity and aeromagnetic surveys, and some onsite magnetic character and susceptability determinations have been completed (Hudson, 1984; McDermott, 1983a; 1983b; Reed and others, 1989).

Comment (Geology): Geologic Description = The upland including Black Mountain is an area of hornfels, calc-silicate hornfels, and tactite intruded by a locally exposed biotite granite. The metasedimentary rocks, fine-grained metapelitic and metacarbonate rocks, are of unknown but probable Paleozoic age. The Late Cretaceous (79.1 +/- 2.9 my, Hudson and Arth, 1983, p. 769) biotiote granite, medium-grained and equigranular, is exposed in a small area on the southern flanks of the upland and is interpreted to be part of an early precurser granite phase rather than an mineralyzing granite phase (Hudson and Arth, 1983, p. 784; Hudson and Reed, 1997, figure 3). The wide distribution of thermally metamorposed rocks and the results of gravity and aeromagnetic surveys (McDermott, 1983a) indicate that most of the Black Mountain area is underlain by granite at depth. The area is transected by many normal faults and related fractures. Sainsbury and Hamilton (1967, p. B23) noted the presence of quartz-topaz greisen with cassiterite, pyrite, pyrrhotite, sphalerite, and galena in the northeast part of the exposed granite body but most of the mineralization and alteration in the area is associated with calc-silicate rocks. Calc-silicate rocks contain garnet, idocrase, tourmaline, wollastonite, and epidote. Cross-cutting veins and alteration along normal faults and fractures include quartz, tourmaline, fluorite, and sulfide minerals (pyrite, sphalerite, arsenopyrite, and probably others). Cassiterite and wolframite have not been conclusively identified in the calc-silicate rocks. Only reconnaissance geochemistry for a few rock samples is available (Sainsbury and Hamilton, 1967, p. B24; Hudson, 1984, p. 20). Tin is weakly anomalous in most tactite samples but one garnet-epidote-idocrase rock contained 1,800 ppm tin. Weak base metal, silver, and gold (60 and 100 ppb) and strong arsenic (400 ppm), fluorine (over 20,000 ppm), and boron (2,230 ppm) anomalies are present in some rocks.

Comment (Reference): Primary Reference = Sainsbury and Hamilton, 1967; McDermott, 1983 (1982 geophysical report); Hudson, 1984

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References

Reference (Deposit): Sainsbury, C.L., 1969, Geology and ore deposits of the central York Mountains, western Seward Peninsula, Alaska: U.S. Geological Survey Bulletin 1287, 101 p.

Reference (Deposit): McDermott, M.M., 1983, Seward Peninsula reconnaissance 1982 geophysical report: Anchorage, Anaconda Minerals Company internal report, 29 p. (Report held by Cook Inlet Region, Inc., Anchorage, Alaska.)

Reference (Deposit): McDermott, M.M., 1983, Investigation of the magnetic contact aureoles of the Khotol and Black Mountain granites, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska).

Reference (Deposit): Hudson, T.L., 1984, Tin systems of Seward Peninsula, Alaska: Anchorage, Anaconda Minerals Company internal report, 51 p. (Report held by Cook Inlet Region Inc., Anchorage, Alaska)

Reference (Deposit): U.S. Geological Survey, 1964, Geological Survey research 1964: U.S. Geological Survey Professional Paper 501-A. p. A1-A367.

Reference (Deposit): Reed, B.L., Menzie, W.D., McDermott, M., Root, H., Scott. W., and Drew, L. J., 1989, Undiscovered lode tin resources of the Seward Peninsula, Alaska: Economic Geology, v. 84, p. 1936-1947.

Reference (Deposit): McDermott, M.M., 1983, Seward Peninsula reconnaissance 1982 geophysical report: Anchorage, Anaconda Minerals Company internal report. 29 p. (Report held by Cook Inlet Region, Inc., Anchorage, Alaska.)

Reference (Deposit): Hudson, T.L., and Arth, J. G., 1983, Tin-granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.

Reference (Deposit): U.S. Geological Survey, 1967, Geological Survey research 1967: U.S. Geological Survey Professional Paper 575-A, p. A1-A377.

Reference (Deposit): Sainsbury, C.L., and Hamilton, J. C., 1967, Mineralized veins at Black Mountain, western Seward Peninsula, Alaska: U.S. Geological Survey Professional Paper 575-B, p. B21-B25.

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