Baby George

Site Name

Primary: Baby George

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Commodity

Primary: Gold

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Location

State: Alaska
District: Ketchikan

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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: Low-sulfide Au-quartz vein

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Most of the principal veins in the Sea Level mine area are bordered by a hydrothermally altered zone up to three feet thick, characterized by generally fine-grain, light-gray to bluish-gray, massive, carbonate- and sericite-bearing rock that commonly contains cubic pyrite crystals up to an inch across (Maas and others, 1995, p. 215). Maas and others (1995) interpret this zone as hydrothermally altered mafic metavolcanic rock. Early miners called this altered rock 'blue porphyry,' which they interpreted as crosscutting altered dikes that predate the quartz veins, but are closely associated with some of the orebodies (Brooks, 1902, p. 65; Wright and Wright, 1908, p. 143). Gold content of these pyritic altered zones is high adjacent to the quartz veins and diminishes away from them. Weathered altered rocks have a reddish-brown, oxidized rind up to three inches thick.

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Pyrite
Gangue: Quartz

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Comments

Comment (Reference): Primary Reference = Wright and Wright, 1908; Maas and others, 1995

Comment (Deposit): Model Name = Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)

Comment (Workings): Workings / Exploration = The deposit was explored by a short prospect tunnel in the early 1900s.

Comment (Geology): Age = Maas and others (1995, p. 215) note that the quartz in the veins in the Sea Level mine area is not recrystallized; the veins thus are probably younger than most or all of the Late Cretaceous regional metamorphism.

Comment (Geology): Geologic Description = The country rocks in this part of Revillagigedo Island are marine, interbedded, andesitic and basaltic metavolcanic rocks and subordinate pelitic metasedimentary rocks that are intruded by stocks, sills, and dikes of Cretaceous feldspar-porphyritic granodiorite (Berg and others, 1988). The strata and some of the granodiorite were regionally metamorphosed to greenschist grade in Late Cretaceous time. These regionally metamorphosed rocks subsequently were locally remetamorphosed to hornblende hornfels near the contacts of Cretaceous granodiorite plutons that were emplaced after the regional metamorphism. The premetamorphic age of the strata is uncertain. Berg and others (1988) assign them a Mesozoic or (late) Paleozoic age. Berg (1982) and Crawford and others (in press) assign them to the Gravina belt, of Late Jurassic or Cretaceous age, or to the Taku terrane, of late Paleozoic to Late Triassic age. The metamorphic and intrusive rocks locally are overlain by basalt and andesite lava flows of Quaternary or Tertiary age.? According to Wright and Wright (1908, p. 147) the Baby George deposit is a quartz [fissure] vein about 10 feet thick in argillaceous and metavolcanic (greenstone) schist. The vein was prospected in the early 1900s by a short tunnel. The Wrights' description, although scant, suggests that the Baby George vein is similar in character and geologic setting to other auriferous quartz fissure veins in the Sea Level mine area (see KC095-098).? Maas and others (1995, p. 215) note that the quartz in the veins in the Sea Level mine area is not recrystallized; the veins thus are probably younger than most or all of the Late Cretaceous regional metamorphism.

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References

Reference (Deposit): Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.

Reference (Deposit): Wright, F.E., and Wright, C.W., 1908, The Ketchikan and Wrangell mining districts, Alaska: U.S. Geological Survey Bulletin 347, 210 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): 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): 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): 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): 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.?

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