- Usage in publication:
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- Chubbuck Porphyry*
- Modifications:
-
- Named
- Geochronologic dating
- Dominant lithology:
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- Monzogranite
- Granodiorite gneiss
- AAPG geologic province:
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- Mojave basin
Summary:
Unit is named the Chubbuck Porphyry for the abandoned railroad siding of Chubbuck in the northern Kilbeck Hills in the northeastern quadrant of the Chubbuck 7.5' quad, San Bernardino Co., CA. These rocks were formerly mapped as porphyritic granite gneiss by Howard and others (1989). Underlies small areas of the Kilbeck Hills. Consists of biotite monzogranite and granodiorite gneiss. Phenocryst augen of alkali feldspar 1 cm long are in a dark, medium- to very fine-grained foliated matrix. Contains mafic enclaves 2 cm across. Intrudes as sheets into Paleozoic strata. Intrudes the quartz diorite of Kilbeck Hills unit. Intrusive isotopic age (U-Pb; zircon) is tentatively regarded as about 150 Ma.
Source: GNU records (USGS DDS-6; Menlo 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 ([ ]).