Unnamed (on tributary to Tin Creek)

Site Name

Primary: Unnamed (on tributary to Tin Creek)

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Commodity

Primary: Zinc
Primary: Copper
Primary: Silver
Primary: Lead
Secondary: Cobalt
Secondary: Cadmium
Secondary: Bismuth

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Location

State: Alaska
District: McGrath

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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: Occurrence
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Skarn Zn-Pb

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Extensive diopside(?) replacement.

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Rocks

Role: Associated
Age Type: Associated Rock
Age in Years: 27.500000+-2.500000
Age Young: Oligocene

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Analytical Data

Not available

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Materials

Ore: Marmatite
Ore: Chalcopyrite
Ore: Galena
Ore: Malachite
Ore: Pyrite
Ore: Sphalerite
Ore: Arsenopyrite
Gangue: Diopside
Gangue: Epidote
Gangue: Garnet
Gangue: Magnetite

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Comments

Comment (Reference): Primary Reference = Bundtzen and others, 1982

Comment (Workings): Workings / Exploration = The Tin Creek Occurrence was first described by Bundtzen, Kline, and Clough (1982) and later by Smith and Albanese (1985). The former reference reported that chip-channel samples contained up to 2.30 percent copper, 0.30 percent lead, 6.20 percent zinc, 110 grams/tonne silver, 500 ppm cadmium, 100 ppm bismuth, and 100 ppm cobalt. Smith and Albanese (1985) reported that a single grab sample contained 5,890 ppm copper, 229 ppm lead, 6,690 ppm zinc, 74 ppm cadmium, and 37.5 grams/tonne silver.

Comment (Geology): Geologic Description = The unnamed occurrence is a well exposed sulfide skarn typical of many silver-base metal-bearing skarns in the Farewell Mineral Belt (Bundtzen, Harris, and Gilbert, 1997; Newberry and others, 1997). Host lithologies are mainly a highly folded and sheared, mid-Silurian, argillaceous limestone of the Terra Cotta Mountains Sandstone, a unit of the Dillinger subterrane (Bundtzen, Harris, and Gilbert, 1997). The metasedimentary rocks are intruded by a N10W-trending, vertically dipping, 20 meter thick, granodiorite dike. Thinner, anastomosing dikes, which occur throughout the limestone, do not appear to alter the limestone (Smith and Albanese, 1985). . Mineralization consists of a 2 meter by 6 meter zone containing disseminated to semi-massive arsenopyrite, chalcopyrite, pyrite, iron-rich sphalerite (marmatite), galena, and pyrite encased in diopside(?)-garnet gangue minerals. The sulfide mineralization is encrusted with a thin but conspicuous malachite rind. The mineralization is parallel to bedding in host limestone, and begins at the contact of a hornblende granodiorite dike. Although mineralization is spatially related to the dike, no thermal alteration of the limestone was identified. Gangue minerals that accompany the sulfides include magnetite, diopside, and garnet. Bundtzen, Kline, and Clough (1982) reported that chip-channel samples contained up to 2.30 percent copper, 0.30 percent lead, 6.20 percent zinc, 110 grams/tonne silver, 500 ppm cadmium, 100 ppm bismuth, and 100 ppm cobalt. Smith and Albanese (1985) reported that one sample from the mineral zone contained 5,890 ppm copper, 229 ppm lead, 6,690 ppm zinc, 74 ppm cadmium, and 37.5 grams/tonne silver.

Comment (Exploration): Status = Inactive

Comment (Deposit): Other Comments = See Tin Creek-Midway deposit (MG043).

Comment (Geology): Age = Chronological age is for granodiorite dike swarm in area .

Comment (Deposit): Model Name = Low-temperature lead-zinc skarn (Cox and Singer, 1986; model 18c).

Comment (Geology): Age = Unknown; thought to be related to the 25 to 30 Ma granodiorite dike swarm in area (Solie and others, 1991; Szumigala, 1987).

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References

Reference (Deposit): Solie, D.N., Bundtzen, T.K., and Gilbert, W.G., 1991, K-Ar ages of igneous rocks in the McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File Report 160, 17 pages, one sheet, 1:250,000 scale.

Reference (Deposit): Bundtzen, T.K., Harris, E.E., and Gilbert, W.G., 1997, Geologic Map of the eastern McGrath quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 97-14, 34 pages, one sheet, scale 1:125,000.

Reference (Deposit): Szumigala, D.J., 1987, Geology of the lead-zinc skarn deposits at Tin Creek area, McGrath B-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 87-5, 21 pages, one sheet, 1:10,000 scale.

Reference (Deposit): Newberry, R.J., Allegro, G.L., Cutler, S.E., Hagen-Levelle, D.D., Adams, D.D., Nicholson, L.C., Weglarz, T.B., Bakke, A.A., Clautice, K.H., Coulter, G.A., Ford, M.J., Myers, G.L., and Szumigala, D.J., 1997, Skarn deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 355-395.

Reference (Deposit): Bundtzen, T.K., Kline, J.T., and Clough, J.G., 1982, Preliminary geologic map of the McGrath B-2 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File report 149, 22 pages, one sheet, scale 1:63,360.

Reference (Deposit): Smith, T.E., and Albanese, M.D., 1985, Preliminary prospect examinations in the McGrath B-2, A-3, and A-4 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File 85-54, 19 pages.

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