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  • Usage in publication:
    • Grayling Lake Granite*
  • Modifications:
    • Named
  • Dominant lithology:
    • Granite
  • AAPG geologic province:
    • Montana folded belt
Publication:

Zen, E-an, 1988, Bedrock geology of the Vipond Park 15-minute, Stine Mountain 7 1/2-minute, and Maurice Mountain 7 1/2-minute quadrangles, Pioneer Mountains, Beaverhead County, Montana: U.S. Geological Survey Bulletin, 1625, 49 p., (incl. geologic map, scale 1:48,000)


Summary:

Named for Grayling Lake, Stine Mountain and Vipond Park quads, Beaverhead Co, MT in Montana folded belt province. Exposures near Grayling Lake are the type locality. Is a medium to coarse, pinkish-gray granite to granodiorite. Cuts Keokirk Quartz Diorite (named), Trapper Tonalite (named), and porphyritic border phase. Contact where exposed is a chilled zone a few cm wide. Is one of five plutonic units of Pioneer batholith. Has a biotite K-Ar age of 72 m.y. Assigned to the Late Cretaceous.

Source: GNU records (USGS DDS-6; Denver GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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