File:Serpentinite (East Dover Ultramafic Body, Ordovician; Adams Brook, east of East Dover, Vermont, USA) 14.jpg
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Summary[edit]
DescriptionSerpentinite (East Dover Ultramafic Body, Ordovician; Adams Brook, east of East Dover, Vermont, USA) 14.jpg |
English: (~6.9 centimeters across at its widest)
Metamorphic rocks result from intense alteration of any previously existing rocks by heat and/or pressure and/or chemical change. This can happen as a result of regional metamorphism (large-scale tectonic events, such as continental collision or subduction), burial metamorphism (super-deep burial), contact metamorphism (by the heat & chemicals from nearby magma or lava), hydrothermal metamorphism (by superheated groundwater), shear metamorphism (in or near a fault zone), or shock metamorphism (by an impact event). Other categories include thermal metamorphism, kinetic metamorphism, and nuclear metamorphism. Many metamorphic rocks have a foliated texture, but some are crystalline or glassy. Serpentinite is a low- to high-grade metamorphic rock formed by alteration of olivine-rich peridotites (dunites - ultramafic, phaneritic, intrusive igneous rocks). Metamorphism of olivine in the presence of water results in the formation of the mineral serpentine (Mg3Si2O5(OH)4). A metamorphic rock composed principally of serpentine is thus a serpentinite. Serpentinite has a mottled greenish color, often has the look & feel of hard candle wax, and ranges in texture from crystalline to “foliated”. Many serpentinites have a foliated look to them, but it’s really not due to an planar alignment of crystals. The appearance of “foliated” serpentinites is really the result of extensive development of slickenlined surfaces. Many serpentinites also have a small component of magnetite that is usually significant enough to feel a slight tug when a magnet is placed next to the rock. Some serpentinites have "veins" of white asbestos (= chrysotile serpentine). Many Precambrian greenstone belts have significant occurrences of serpentinites. Slices of dunitic mantle caught up in orogenic belts by obduction (= ophiolites) are often serpentinized. Sometimes, mantle peridotite masses that were caught up in rising magmas have been serpentinized (for example, in kimberlites & lamproites). The sample seen here is serpentinite from the Appalachian Mountains of New England. The rock comes from the East Dover Ultramafic Body in the Green Mountains of Vermont. This unit is part of the North American Ultramafic Belt, an ophiolite that was originally dunitic mantle material tectonically emplaced during the Taconic Orogeny in the late Middle Ordovician (sensu traditio), about 460 million years ago. Locality: loose piece from Adams Brook, north of Dover Hill Road (= East Dover Road), just east of the town of East Dover, southwestern Newfane Township, central Windham County, Green Mountains, southern Vermont, USA |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/50503836308/ |
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@N05/50503836308. It was reviewed on 18 November 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
18 November 2020
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 15:42, 18 November 2020 | 2,867 × 1,727 (4.14 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/50503836308/ with UploadWizard |
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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/11 |
ISO speed rating | 80 |
Date and time of data generation | 21:05, 18 October 2020 |
Lens focal length | 11.614 mm |
Width | 4,000 px |
Height | 3,000 px |
Bits per component |
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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 18.0 (Macintosh) |
File change date and time | 01:21, 19 October 2020 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 21:05, 18 October 2020 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.90625 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 4 APEX (f/4) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 16,460.905349794 |
Focal plane Y resolution | 16,483.516483516 |
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 | Standard |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 21:21, 18 October 2020 |
Unique ID of original document | C870D209F010F5B071D3357064595D27 |
IIM version | 24,576 |