File:Ultrapotassic metasomatite (Squaw Gulch roadcut, Cripple Creek Mining District, Colorado, USA) 2.jpg
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English: Weathered ultrapotassic metasomatite in Colorado, USA.
This outcrop is at the western boundary of the Cripple Creek Diatreme, the root zone of an ancient, eroded volcanic center of Oligocene age. The diatreme is variably mineralized with a suite of gold-bearing minerals. The rock seen here is an ultrapotassic metasomatite with weathering stains. This site was visited during a 2007 Geological Society of America national conference field trip. There were many people and we were rushed - not much time to listen to the field trip leaders, take notes, take pictures, look at the rocks, and take samples. As a consequence, I didn't and still don't fully understand this particular material. "Metasomatite" refers to a rock that has been highly chemically altered. Metasomatism is a form of metamorphism. Most metamorphic rocks have been intensely altered by heat and/or pressure resulting from regional tectonic activity or deep burial. The original rock here may have been Precambrian granite (Cripple Creek Leucogranite, Mesoproterozoic, ~1.43 Ga) or Oligocene phonolite (Cripple Creek Diatreme, Early Oligocene, ~32 Ma). This cut is at the transition between diatreme and older country rocks - I'm not exactly sure which side of the boundary this is. Both the country rocks and diatreme rocks have been altered and covered with weathering stains. This locality no longer exists. Since 2007, the road has been diverted, the adjacent valley of Squaw Gulch has been filled in, and the area is now part of the mining operation. Locality: former Route 67 roadcut along the northern side of Squaw Gulch, Cripple Creek Mining District, southern Teller County, central Colorado, USA |
| Date | |
| Source | https://www.flickr.com/photos/47445767@N05/49245443321/ |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/49245443321. It was reviewed on 15 January 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 17:54, 15 January 2020 | | 3,008 × 2,000 (4.91 MB) | Ser Amantio di Nicolao (talk | contribs) | User created page with UploadWizard |
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