File:Metakomatiite (Diamond Springs Formation, Mesoarchean; South Pass, Wind River Range, Wyoming, USA) 2 (31036252770).jpg
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editDescriptionMetakomatiite (Diamond Springs Formation, Mesoarchean; South Pass, Wind River Range, Wyoming, USA) 2 (31036252770).jpg |
Metakomatiite (serpentinite) from the Precambrian of Wyoming, USA. (6.3 centimeters across at its widest) Komatiites are very rare, magnesium-rich, extrusive, ultramafic igneous rocks. They are named after the Komati River Valley in South Africa, the type locality. Komatiite is an exceedingly rare type of lava. No volcano on Earth erupts this material today. Komatiites are essentially restricted to the Archean (4.55 to 2.5 billion years ago). Experimental evidence has shown that komatiite lavas, when originally erupted, were considerably hotter (~1600º C) than any modern lava type on Earth. This indicates that Earth’s mantle was much hotter than now. Other geologic evidence also indicates that early Earth’s heat flux was much higher than today’s. Komatiite lava had a very low viscosity - it could flow like an ultradense gas. This property permitted the solidification of some individual lava flows that are only 1 cm thick. The classic texture of komatiites is spinifex texture, named after clumps of long, spiky (& painful!) grasses. Komatiites with spinifex texture have short to long blades or plates of olivine mixed with smaller-scale blades of pyroxene. All Archean komatiites are metamorphosed - the original igneous mineralogy (olivine, pyroxene, minor chromite, etc.) is gone to mostly gone. Such rocks are best termed metakomatiites, but the prefix “meta-” is usually not specified. Komatiites have economic significance, as many are closely associated with copper-nickel minerals (chalcopyrite & pentlandite), plus minor platinum-group elements, arsenides, bismuthides, and maybe a little gold and silver. Komatiites are a world-class source of nickel in Canada and Western Australia. The rock shown above is an unusual komatiite - it is not spinifex-textured and it is not extrusive. This is a metamorphosed (serpentinized), cumulate-textured, intrusive komatiite. It's MgO content is 26.6% to 38.1%. Stratigraphy: Diamond Springs Formation, Mesoarchean, >2.87 Ga Locality: low roadcut along old dirt road west of & uphill from power substation (Rocky Mountain Power, Atlantic City Switching Station), just west of Crest Road, northwestern side of Rt. 28, southwestern side of South Pass, Wind River Range, west-central Wyoming, USA (42° 31' 29.45" North latitude, 108° 45' 52.36" West longitude) |
Date | |
Source | Metakomatiite (Diamond Springs Formation, Mesoarchean; South Pass, Wind River Range, Wyoming, USA) 2 |
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@N05/31036252770 (archive). It was reviewed on 30 November 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
30 November 2019
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current | 17:08, 30 November 2019 | 3,177 × 2,454 (5.86 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/9 |
ISO speed rating | 80 |
Date and time of data generation | 23:21, 3 December 2016 |
Lens focal length | 8.295 mm |
Image title | |
Width | 4,000 px |
Height | 3,000 px |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 00:39, 4 December 2016 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 23:21, 3 December 2016 |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.34375 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 3.34375 APEX (f/3.19) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
Color space | sRGB |
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Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 19:39, 3 December 2016 |
Unique ID of original document | 1ABA013E3A4507D8E508D08F0BCB3707 |