Dunite


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dunite

[′dü‚nīt]
(petrology)
An ultrabasic rock consisting almost solely of a magnesium-rich olivine with some chromite and picotite; an important source of chromium.

Dunite

 

(named after Mount Dün, New Zealand), a magmatic rock that is ultrabasic and black, dark-green, or light-green in color; it consists of 85 to 100 percent olivine and contains chromite as an admixture, sometimes together with magnetite. Dunite is very rich in magnesium and contains little silica. It is rarely found in an unchanged state; it is usually more or less serpentinized and even totally transformed into serpentine. Dunite is linked by gradual transitions with several gabbros and pyroxenites. Dunites are widespread; they usually form sills, parallel lenses, and intersecting pipes; more seldom they form large intrusive bodies (for example, the dunite belts along the entire Urals and the Mugodzhary). It is thought that dunites are chunks of the upper mantle that were tectonically introduced into the young rocks of the upper part of the earth’s crust. Deposits of various minerals (including chromites, platinum, nickel, cobalt, talc, and chrysotile-asbestos) are associated with dunite. Dunite is used for the manufacture of fire-resistant materials.

References in periodicals archive ?
The crustal section of the Muslim Bagh ophiolite consists of bands of dunite wehrlite pyroxenite at the base overlain by the layered and foliated gabbro.
Nickel, copper and platinum group element mineralization is hosted in dunite and herzolite within the Tonsina Ultramafic Complex.
I) the main ultrabasic-basic sequence, the Puerto Nuevo Sequence (harzburgite, dunite, cyclic units of dunite, pyroxenite and gabbro) of the Vizcaino Peninsula, is not an obducted slab of oceanic lithosphere; it is instead a part of a layered complex, the Vizcaino Layered Complex, which also includes, upwards, isotropic gabbros, diorites (La Pintada Sequence);
Rodingites are associated with dunite and serpentinite.
El Picacho Metagabbros show greenschist-- to lower-amphibolite-facies parageneses, conspicuous mylonitic structure, no relation to metasediments, and spatial association to the Medellin Dunite.
4:15 Metamorphism of Dark Ridge Dunite, North Carolina.
Dunite and peridotite comprise about 1,200 m of the 1,800 m thickness of the layered series.
Melts moving by porous flow in the interiors of such large dunites are separated from residual peridotite by many meters of dunite and thus escape chemical interaction with residual peridotite even though the melts are moving slowly.
Olivine occurs in an ultra-basic igneous rock called dunite.
The alluvial deposits on Dime Creek are composed of mostly volcanic andesite and basalt sand and gravel with occasional cobbles of intrusive olivine dunite.
7) By contrast, his fellow Dunite George Blais was a reported evangelical nudist sun worshipper, whose strict vegan diet and fantastically good health brought him a widespread following of eager new disciples well into his sixties.
Tenders are invited for Supply Of 1400 Mt Of Dunite (1-4 Mm) To Sru Bhiali