- Usage in publication:
-
- Sacramento porphyry*
- Modifications:
-
- Named
- Dominant lithology:
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- Porphyry
- AAPG geologic province:
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- Eagle basin
Summary:
Named for typical occurrence at head of Sacramento Gulches in vicinity of Leadville, Lake Co, CO in the Eagle basin. No type locality designated. Differs from Lincoln porphyry in that it has no large feldspar crystals. Contains some large rosy quartz grains, two feldspars, biotite and hornblende. Mapped with other porphyries on geologic map. Age not clearly stated. [Is probably a Tertiary porphyry.]
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Sacramento Porphyry*
- Modifications:
-
- Overview
- Geochronologic dating
- AAPG geologic province:
-
- Eagle basin
Summary:
Has a 43.9 Ma fission-track date on zircon and apatite. Shown as Tertiary age on a geologic map, as younger than the Paleocene Lincoln Porphyry, as the same age as the Tertiary Evans Gulch Porphyry, and as older than the Tertiary Johnson Gulch Porphyry. Occurs as a 200 m thick sill east of the main Leadville district and near crest of Mosquito Range, Lake Co, CO in the Eagle basin. [The one date from one sample is not conclusive enough to be used to assign a more specific age than Tertiary to the entire Sacramento Porphyry according to Thompson, 2/2/89, oral communication.]
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 ([ ]).