Unnamed Occurrence (ARDF - ID148; near hill 2380 south of summit of Granite Mountain), Iditarod District, Yukon-Koyukuk Borough, Alaska, USA

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Location: This occurrence is about 650 feet east of hill 2380 on a southern side of Granite Mountain. The occurrence is at an elevation of about 2,100 feet, about 0.4 mile west of the center of section 33, T. 26 N., R. 40 W., of the Seward Meridian. The location is accurate.
Geology: This occurrence is a irregular zone of tourmaline-rich quartz monzonite in the border phase of the 62.6 Ma, Granite Mountain pluton (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005). The size and orientation of the mineralized body is uncertain. One grab sample contained 1,500 parts per billion (ppb) silver, 200 parts per million (ppm) lead, 15 ppm tin, 12 ppm antimony, and more than 2,000 ppm boron McGimsey and others, 1988).
Workings: Samples were collected by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in 1984 (McGimsey and others, 1988).
Age: Unknown; possibly related to the nearby Granite Mountain pluton that has a 40K/40Ar age of 62.6 Ma (Miller and Bundtzen, 1994).
Alteration: Tourmaline in quartz monzonite.

Commodities (Major) - Ag, Pb; (Minor) - B, Sb, Sn
Development Status: None
Deposit Model: Sn-polymetallic deposit (Cox and Singer, 1986; model 20b).

References

McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet.

Mineral List

'Tourmaline'

1 entry listed.