Big Boulder

The Big Boulder is a gold 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: Big Boulder

Commodity

Primary: Gold

Location

State: Alaska
District: Juneau (Skagway subdistrict)

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

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

Physiography

Not available

Mineral Deposit Model

Model Name: Polymetallic veins

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Gold
Gangue: Quartz

Comments

Comment (Workings): Workings / Exploration = Still and others (1991) report a shallow adit that, '..was likely driven about 80 years ago.'

Comment (Reference): Primary Reference = Still and others, 1991

Comment (Geology): Age = Probably Cretaceous or younger based on the age of nearby intrusives (MacKevett and others, 1974; Gilbert and others, 1987).

Comment (Exploration): Status = Probably inactive

Comment (Geology): Geologic Description = Wright (1904 [B 225 and B 236]) describes this occurrence as a quartz ledge. The brief description of Still and others (1991) is a little unclear, but the prospect appears to be quartz segregations and veins in felsic dikes within slate. The dikes strike north-northwest, dip steeply, are up to 1.3 feet thick, and crop out for up to 60 feet along strike. An adit was driven through a felsic dike for 18 feet where is cuts a quartz band for about 5 feet. None of the samples of quartz and dike rock contained anomalous gold, but they had up to 1.8 ppm silver, 308 ppm lead, 100 ppm tin, 500 ppm arsenic, 700 ppm bismuth, and 900 ppm antimony. Bedded rocks in the area are metasediments and metavolcanics of the Cheetdeekahyu Group of Redman and others (1985). Their metamorphic grade and average grain size increases to the north and northeast towards Four Winds Mountain. They have been included in the Four Winds metamorphic complex (Forbes and others, 1987; Gilbert and others, 1987). The probable Devonian or Late Triassic age of the Cheetdeekahyu Group (Gilbert and others, 1987) establishes a maximum age for the veins at this prospect. However, if the dike is Cretaceous as are nearby intrusives, then the veins are Cretaceous or younger in age.

Comment (Deposit): Model Name = Auriferous quartz vein (Cox and Singer, 1986; model 22c or 36a).

References

Reference (Deposit): Forbes, R.B., Gilbert, W.G., and Redman, E.C., 1987, The Four Winds Complex; a newly recognized Paleozoic metamorphic terrane in southeastern Alaska [abs.]: Geological Society of America, Abstracts with Program, v. 19, no. 6, p. 378.

Reference (Deposit): Still, J.C., Gilbert, W.G., and Forbes, R.B., 1987, Final report of stream sediment, float, and bedrock sampling in the Porcupine mining area, southeast Alaska, 1983-1985: U.S. Bureau of Mines Open-File Report 36-87, 35 p., 8 sheets.

Reference (Deposit): Gilbert, W.G., Burns, L.E., Redman, E.C., and Forbes, R.B., 1987, Preliminary bedrock geology and geochemistry of the Skagway B-3 Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 87-2, 2 sheets, scale 1:36,200.

Reference (Deposit): Still, J.C., Hoekzema, R.B., Bundtzen, T.K., Gilbert, W.G., Wier, K.R., Burns, L.E., and Fechner, S.A., 1991, Economic geology of Haines-Klukwan-Porcupine area, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 91-4, 156 p., 5 sheets, scale 1:63,360.

Reference (Deposit): Still, J.C., 1991, Bureau of Mines mineral investigations in the Juneau mining district, Alaska, 1984 - 1988, v. 2, Detailed mine, prospect, and mineral occurrence descriptions, section A, Haines-Klukwan-Porcupine subarea: U.S. Bureau of Mines of Mines Special Publication, 214 p.

Reference (Deposit): Gilbert, W.G., and Redman, E.C., 1989, Lode deposits, prospects, and occurrences of the Porcupine mining area, southeast Alaska: U.S. Bureau of Mines Open-File Report 17-89, 1 sheet, scale 1:39,600.

Reference (Deposit): Redman, E.C., Gilbert, W.G., Jones, B.K., Rosenkrans, D.S., and Hickok, B.D., 1985, Preliminary bedrock-geologic map of the Skagway B-4 Quadrangle: Alaska Division of Geological and Geophysical Surveys Report of Investigations 85-6, 1 sheet, scale 1:40,000.

Reference (Deposit): MacKevett, E.M., Jr., Robertson, E.C., and Winkler, G.R., 1974, Geology of the Skagway B-3 and B-4 quadrangles, southern Alaska: U.S. Geological Survey Professional Paper 832, 33 p.

Reference (Deposit): Wright, C.W., 1904, The Porcupine placer mining district, Alaska in Emmons, S.F., and Hayes, C.W., eds., Contributions to economic geology 1903: U.S. Geological Survey Bulletin 225, p.60-63.

Reference (Deposit): Wright, C.W., 1904, The Porcupine district, Alaska: U.S. Geological Survey Bulletin 236, 35 p.

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