File:Serpentinite (East Dover Ultramafic Body, Ordovician; roadcut east of East Dover, Vermont, USA) 7.jpg
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Summary
DescriptionSerpentinite (East Dover Ultramafic Body, Ordovician; roadcut east of East Dover, Vermont, USA) 7.jpg |
English: 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 serpentinite outcrop seen here is in New England. This is part of the East Dover Ultramafic Body in the Green Mountains of Vermont. The unit is part of the extensive 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. At this site, the rocks are somewhat weathered, partly serpentinized dunites (antigorite partially replacing forsterite olivine + some chromite). Locality: roadcut on the northern side of Dover Hill Road, just east of the town of East Dover, southern Vermont, USA (vicinity of 42° 57' 00.70" North latitude, 72° 45' 44.33" West longitude) |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/49648149408/ |
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@N05/49648149408. It was reviewed on 12 March 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
12 March 2020
Captions
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8 September 2006
0.008 second
48 millimetre
200
image/jpeg
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 01:10, 12 March 2020 | ![]() | 3,008 × 2,000 (4.83 MB) | Ser Amantio di Nicolao | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/49648149408/ with UploadWizard |
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Camera manufacturer | NIKON CORPORATION |
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Camera model | NIKON D70s |
Exposure time | 1/125 sec (0.008) |
F-number | f/9 |
ISO speed rating | 200 |
Date and time of data generation | 11:03, 8 September 2006 |
Lens focal length | 48 mm |
Width | 3,008 px |
Height | 2,000 px |
Bits per component |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop Elements 16.0 (Macintosh) |
File change date and time | 13:25, 11 March 2020 |
Y and C positioning | Co-sited |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 11:03, 8 September 2006 |
Meaning of each component |
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Image compression mode | 4 |
Shutter speed | 6.965784 |
APEX aperture | 6.33985 |
Exposure bias | 0 |
Maximum land aperture | 4.3 APEX (f/4.44) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash did not fire, compulsory flash suppression |
DateTime subseconds | 10 |
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DateTimeDigitized subseconds | 10 |
Supported Flashpix version | 1 |
Color space | sRGB |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Scene type | A directly photographed image |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Focal length in 35 mm film | 72 mm |
Scene capture type | Landscape |
Scene control | None |
Contrast | Normal |
Saturation | Normal |
Sharpness | Hard |
Subject distance range | Unknown |
Serial number of camera | 1004a0cc |
Lens used | 18.0-70.0 mm f/3.5-4.5 |
Date metadata was last modified | 09:25, 11 March 2020 |
Unique ID of original document | EC034870D3158A78BCCC08D4DB5F766D |