- Usage in publication:
-
- Brady Butte Granodiorite*
- Modifications:
-
- Named
- Dominant lithology:
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- Granodiorite
- AAPG geologic province:
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- Southwestern Basin-and-Range region
Summary:
Named for section in canyon of Wolf Creek immediately northeast of Brady Butte at north end of ridge about 15 mi southeast of Prescott and 6 mi southwest of Mayer, Yavapai Co, AZ in the Southwestern Basin-and-Range region. No type locality designated. Is unconformably below the Yavapai Series. Unconformity marked by a coarse basal conglomerate that contains large subangular blocks of gneiss indistinguishable from Brady Butte. Clasts of chert, argillite, siltstone, and quartzite are abundant, commonly flattened or elongated. Matrix is poorly sorted arkosic sandstone with angular to subround quartz, plagioclase, and microcline grains. Contact with overlying Texas Gulch Formation of Alder Group is a series of steeply dipping, north-northeast-trending faults. Is truncated by large plutons which are intrusive into the Alder Group. Is a granodiorite that is gneissic with a medium- to coarse-grained hypidiomorphic-granular texture, characterized by fine-grained granular biotite and turbid plagioclase. Is older than 1,700 m.y., or Precambrian age. Geologic map.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Brady Butte Granodiorite*
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Southwestern Basin-and-Range region
Summary:
Has a gneissic and porphyritic facies in Prescott-Jerome area, Yavapai Co, AZ, in Southwestern Basin-and-Range region. Porphyritic facies intrudes Spud Mountain Volcanics of Big Bug Group (new). Unconformably underlies Texas Gulch Formation at its type locality. Has the same age as an unnamed porphyritic granodiorite of 1,770 +/-10 m.y., or Precambrian. Geologic map. Columnar sections.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Brady Butte Granodiorite*
- Modifications:
-
- Age modified
- Overview
- AAPG geologic province:
-
- Southwestern Basin-and-Range region
Summary:
Assigned to suite one (of 4) in the Prescott area (Yavapai County, Arizona, Southwestern Basin-and-Range region). Suite one, consisting of pre-tectonic, equigranular, medium-grained biotite granodiorite and leucocratic granodiorite and granite plutons, includes the 1,750 +/-10 Ma Brady Butte Granodiorite, granodiorite of Minnehaha, granodiorite of Big Bug Creek, Crooks Canyon Granodiorite, granodiorite of Lane Mountain, and granite of Rich Hill. The plutons are moderately peraluminous, have very low magnetite concentrations, low to average strontium, and are concentrated in the central part of the area. Brady Butte intrudes a metavolcanic terrane. Is unconformably overlain by the Texas Gulch Formation. The granodiorite of Minnehaha is southwestern extension of Brady Butte, but is more mafic and calcic. Granodiorite of Big Bug Creek is megascopically identical to Brady Butte. Age is refined from Proterozoic X to Early Proterozoic. Is the oldest dated pluton in central Arizona. Report includes geochemical analyses.
Source: Modified from 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 ([ ]).