- Usage in publication:
-
- Pando porphyry*
- Modifications:
-
- Named
- Dominant lithology:
-
- Porphyry
- AAPG geologic province:
-
- Eagle basin
Summary:
[Named probably for Pando, Eagle Co., CO in Eagle basin]. Is a quartz latite porphyry composed of scattered quartz and plagioclase phenocrysts and ragged grains of altered biotite in a light-gray or buff, dense groundmass. Is oldest of four porphyries in Pando area. Is persistent for several miles along upper Eagle River, from East Fork northward beyond Gilman, and crops out on slope east of Pando where it overlies silicified Leadville limestone. Assigned to early Paleocene.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Pando Porphyry*
- Modifications:
-
- Geochronologic dating
- AAPG geologic province:
-
- Eagle basin
Summary:
Is the oldest and most widespread of all the porphyries in the Leadville area. Has a K-Ar date on biotite of 70 m.y. Considered to be Late Cretaceous in age in the Eagle basin. Includes rocks known as White Porphyry and Mount Zion Porphyry [of the Gray Porphyry Group.]
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 ([ ]).