- Usage in publication:
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- Hoffman Park Granite*
- Modifications:
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- Named
- Geochronologic dating
- Dominant lithology:
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- Granite
- AAPG geologic province:
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- Eagle basin
Summary:
Named for Hoffman Park, the type locality, Chaffee Co, CO in the Eagle basin. Forms an oval 1.5 x 0.5 km stock near the margin of the Mount Princeton batholith. Previously mapped as part of the Mount Princeton Quartz Monzonite. Now thought to be a separate, slightly older, intrusion of the Mount Antero Granite and younger than the Mount Princeton and the Mount Aetna Quartz Monzonite Porphyry. Is a massive, medium-grained, pink to gray leucocratic granite with 5 mm long pink potassium feldspar, 2-3 mm rounded quartz grains, and dark biotite. In comparison with Mount Princeton, Hoffman Park is lighter in color, slightly finer in grain size, has no hornblende, less biotite or opaque minerals, and lacks sphene. Geologic map. Age of 33.20.7 m.y. K-Ar on biotite obtained. Oligocene age. Geologic maps.
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 ([ ]).