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Topic: Peridotite


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In the News (Sun 21 Jul 19)

  
  Peridotite - LoveToKnow 1911
In some peridotites these form segregations or irregular masses which are of importance as sources of the ores of chromium.
In Skye the pyroxenebearing peridotites usually contain green chrome-diopside (a variety of augite distinguished by its pale colour and the presence of a small amount of chromium).
The dunites are peridotites, similar to the rock of Dun Mountain, New Zealand, composed essentially of olivine in a finely granular condition.
www.1911encyclopedia.org /Peridotite   (2088 words)

  
 Reference.com/Encyclopedia/Peridotite
Peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene.
Peridotite is derived from the Earth's mantle, either as solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle.
Peridotites have two primary modes of origin, as mantle rocks formed during the accretion and differentiation of the Earth, or as cumulate rocks formed by precipitation of olivine ± pyroxenes from basaltic or ultramafic magmas; these magmas are ultimately derived from the upper mantle by partial melting of mantle peridotites.
www.reference.com /browse/wiki/Peridotite   (1405 words)

  
 Peridotite
Peridotite is the source of all chromium ore and naturally occurring diamonds, and of nearly all chrysotile asbestos.
Nearly all peridotite is more or less altered to serpentine (hydrous phases are present) In warm, humid climates peridotite and serpentine have weathered to soils worked on a relatively small scale for iron, nickel, cobalt, and chromium.
Based on the observed samples, peridotite with about 50 percent olivine, 30 percent pyroxene, and 15 percent garnet is considered to be the dominant rock of the upper mantle.
geology.csupomona.edu /alert/igneous/peridotite.htm   (291 words)

  
  Peridotite Summary
Peridotite is a dense, coarse-grained rock, consisting mostly of the minerals olivine and pyroxene.
Peridotite is derived from the mantle of the earth, either as solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle.
The rocks of the peridotite family are uncommon at the surface and are highly unstable, because olivine reacts quickly with water at typical temperatures of the upper crust and at the Earth's surface.
www.bookrags.com /Peridotite   (798 words)

  
  The Dispatch - Serving the Lexington, NC - News
Peridotite is a dense, coarse-grained rock, consisting mostly of the minerals olivine and pyroxene.
Peridotite is derived from the Earth's mantle, either as solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle.
Peridotites have two primary modes of origin, as mantle rocks formed during the accretion and differentiation of the Earth, or as cumulate rocks formed by precipitation of olivine ± pyroxenes from basaltic or ultramafic magmas; these magmas are ultimately derived from the upper mantle by partial melting of mantle peridotites.
www.the-dispatch.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=peridotite   (1368 words)

  
 Peridotite
Peridotite is a dense, coarse grained ultrabasic rock, consisting mainly of the minerals olivine and pyroxene.
Peridotite is also a group of mantle derived igneous rocks.
The rocks of the peridotite family are uncommon at the surface and are highly unstable.
www.xasa.com /wiki/en/wikipedia/p/pe/peridotite.html   (253 words)

  
 ALPINE-TYPE GARNET PERIDOTITE IN THE CARIBBEAN
Alpine-type garnet peridotite is known from only two places in the Americas, (1) an occurrence in the Seward Peninsula, Alaska, and (2) a recently discovered occurrence in northern Dominican Republic on the Caribbean island of Hispaniola.
The garnet peridotite (forsterite + diopside + enstatite + garnet + spinel + late magnesiohornblende + late serpentine) is associated with hornblende gneiss and schist (hornblende + plagioclase + quartz + rutile +/- garnet +/- biotite +/- epidote), and retrograded eclogite (hornblende + symplectic diopside-plagioclase + garnet + quartz +/- epidote).
Elsewhere eduction of garnet peridotite took place at ocean-continent convergent boundaries, where eduction was apparently assisted by the buoying effect of the less dense continental crust.
gsa.confex.com /gsa/2001AM/finalprogram/abstract_22415.htm   (447 words)

  
 Diamonds | American Museum of Natural History
The 2 most common types of xenoliths are peridotites and eclogites.
Peridotite is the main constituent of the mantle beneath the crust and consists primarily of olivine -- the gem variety is peridot.
Eclogite, consisting primarily of garnet and a green pyroxene, is formed by plate tectonics when basalt of the ocean crust founders into the mantle.
www.amnh.org /exhibitions/diamonds/xenoliths.html   (143 words)

  
 PERIDOTITE - Online Information article about PERIDOTITE
common in some peridotites, especially those which have undergone pressure or shearing: these aggregates are known as pilite.
The great majority of stony or lithoidal meteorites (aerolites) are rich in olivine and present many analogies to the terrestrial peridotites.
Although many peridotites are known in which the constituent minerals are excellently preserved, the majority show more or less advanced decomposition.
encyclopedia.jrank.org /PAS_PER/PERIDOTITE.html   (1253 words)

  
 AlistosMexico
The decline in gold-nickel values away from the peridotite mass also suggests that the source of the ore was the basic igneous stock.
This is suggested because peridotite magmas are thought to be low in water content (8), and no acid igneous rock younger than the peridotite occurs in the immediate area of the Alistos deposit.
End-stage solutions from the peridotite magma, perhaps mixed with circulating ground waters, removed nickel and probably gold from the peridotite and deposited them in the latite as veins of nickel arsenides and sulphides, and native gold.
www.minsocam.org /msa/collectors_corner/arc/alistosmex.htm   (4838 words)

  
 Tablelands: Newfoundland and Labrador Heritage
It is thought to originate in the earth's mantle and was forced up from the depths during a plate collision several hundred million years ago.
Peridotite lacks the usual nutrients required to sustain most plant life, hence its barren appearance.
Peridotite is also high in iron, which accounts for its brownish colour.
www.heritage.nf.ca /environment/table.html   (119 words)

  
 ODP Leg 176: Where is the peridotite?
Peridotites have been dredged from all over the nearby fracture zone, named after the Woods Hole vessel, Atlantis II, and from many others along the Indian Ocean ridges.
The kink in the travel paths of seismic waves is the clue to identification of the mantle, beneath both the continents and ocean basins, as peridotite.
Adding water to peridotite involves as much as a 30% expansion of the mineral crystal lattices within it, which of course reduces the density of the rock.
www-odp.tamu.edu /public/life/176/natland3.html   (3056 words)

  
 Ronda Peridotite - A
The Ronda peridotite: Garnet-, spinel-, and plagioclase-lherzolite facies and the P-T trajectories of a high-temperature mantle intrusion.
Xonotlite in rodingite assemblages from the Ronda peridotites, Betic Cordilleras, southern Spain.
Obata, M. The Ronda peridotite: Garnet-, spinel-, and plagioclase-lherzolite facies and the P-T trajectories of a high-temperature mantle intrusion.
www.schweich.com /rpA.html   (817 words)

  
 Mantle solidus: Experimental constraints and the effects of peridotite composition
Consideration of experimental constraints on the peridotite solidus and of a theoretical model of melting in a simple analogue system suggests that a key variable affecting peridotite solidus temperature is the near-solidus liquid alkali concentration.
Thus small bulk concentrations of K can have a significant influence on the peridotite solidus, and the effect of Na diminishes with increasing pressure, as it becomes more compatible in the solidus residua.
As a consequence, experiments performed on a range of peridotite compositions may not reflect the likely effect of variable mantle composition on solidus temperature if they do not match the appropriate correlation between alkali content and clinopyroxene mode.
www.agu.org /pubs/crossref/2000/2000GC000070.shtml   (414 words)

  
 Olympus Microscopy Resource Center: Polarized Light Microscopy Gallery - Peridotite
Peridotite is generally believed to be the most common rock found in the upper mantle of the Earth.
When weathered, peridotite often exhibits a brownish appearance due to the formation of iron oxides, but the rock is more familiar in its fresh, green form.
The typical coloration of peridotite is indicative of its mineralogical content, which is comprised of at least 10 percent of the yellowish-green mineral olivine.
www.olympusmicro.com /galleries/polarizedlight/pages/peridotitesmall.html   (241 words)

  
 Reference Library - RedOrbit   (Site not responding. Last check: )
Peridotite is a dense, coarse grained ultrabasic rock, consisting mainly of the minerals olivine and pyroxene.
Peridotite is also a group of mantle derived igneous rocks.
The rocks of the peridotite family are uncommon at the surface and are highly unstable.
www.redorbit.com /education/reference_library?article_id=405   (262 words)

  
 Petrology of Peridotite and Pyroxenite Xenoliths from the Jericho Kimberlite: Implications for the Thermal State of the ...   (Site not responding. Last check: )
More than half of the Jericho peridotitic garnets show Y concentrations exceeding 10 ppm and one-third of peridotitic garnets demonstrate high Zr (>30 ppm); such elevated levels of Y and Zr are usually taken as evidence of relatively `high-temperature' and `low-temperature' metasomatic enrichment, respectively (Griffin and Ryan, 1995; Griffin et al.
Equilibrium pressure-temperature estimates for the Jericho peridotites and pyroxenites according to (a) Finnerty and Boyd, (1987) and MacGregor, (1974), (b) O'Neill and Wood, (1979) and MacGregor, (1974), and (c) Brey and Köhler, (1990).
Finnerty, A. and Boyd, J. Thermobarometry for garnet peridotites: basis for the determination of thermal and compositional structure of the upper mantle.
library.iem.ac.ru /j-petr/1-4099/html/egc006_gml.html   (10923 words)

  
 Ocean Drilling Program: Leg 209 Preliminary Report
This result is not consistent with previous inferences, based on the composition of dredged peridotite samples, that the degree of depletion of mantle peridotites decreases from south to north across the 15°20' Fracture Zone from 14°40' to 15°40'N along the Mid-Atlantic Ridge.
Peridotite outcrops along the flanks of the Mid-Atlantic rift valley are commonly interpreted to be footwall exposures that were originally overlain by normal fault surfaces.
Half-core measurements and discrete peridotite samples all have positive inclinations that are presumable of normal polarity, although the mean inclination (13°) is significantly shallower than the expected dipole inclination at the site (28°), indicating that the rocks are normally polarized.
www-odp.tamu.edu /publications/prelim/209_prel/prel17.html   (3514 words)

  
 Rogue River - Siskiyou National Forest - Recreational Activities
Peridotite is an igneous rock with a coarse crystalline texture.
Peridotite is the deepest rock layer of an ophiolite.
Peridotite consists of rock from the earth’s mantle, which is usually 5-8 kilometers below the ocean floor (see cross section of earth).
www.fs.fed.us /r6/rogue-siskiyou/recreation/geology/photos-desc-rock-types.shtml   (803 words)

  
 The Dynamic Earth @ National Museum of Natural History
The large egg-shaped peridotite is a single xenolith, one of the largest ever found.
The basaltic lava is chock-full of green and dark reddish-brown peridotite xenoliths.
Peridotite, the upper mantle's most abundant rock, is named for peridot — the gem variety of olivine.
www.mnh.si.edu /earth/text/4_1_5_0.html   (1276 words)

  
 Journal Contents -Intracrustal tectonic evolution of large lithosphere mantle slabs
The Ronda and Rif peridotites interlayered with crustal rocks in the western Alboran Domain are a good example of a large volume of very deep rocks exhumed in an unlikely tectonic context.
Throughout the Miocene, the peridotite bodies were dispersed and exhumed as passive elements of the Alboran Domain during its collision with the south-Iberian and Magrebian margins.
We propose that all the Alboran peridotite bodies were emplaced as a single slab, probably farther east from their present position.
www.virtualexplorer.com.au /journal/2002/08/sanchez   (581 words)

  
 8th INTERNATIONAL KIMBERLITE CONFERENCE (8IKC)   (Site not responding. Last check: )
Gt-Sp peridotites are developed in interval from near 60 km, where garnetization of the most Al-enriched peridotites begin, up to 170 km, where granatization of the most depleted peridotites with maximal values of Cr/(Cr+Al) ratio (over 70%) have completed; maximal amount of Gt-Sp peridotites is corresponded with depths of 90-100 km.
Origin of studied peridotites is complex and cannot be explained by simple models of subduction of oceanic peridotites or partial melting processes of primitive mantle.
ii) Sheared peridotites are porphyroclastic, not as coarse grained (1 to 2 mm) as the granular peridotites and are not silicified.
www.venuewest.com /8IKC/s6post.htm   (8483 words)

  
 Polybaric Petrogenesis of Mafic Layers in the Horoman Peridotite Complex, Japan   (Site not responding. Last check: )
Upper-mantle peridotites exposed in the Earth's crust are commonly interlayered by `mafic layers' such as pyroxenites and olivine gabbros (mafic granulites), which may parallel or cross-cut the foliation of the host peridotite (e.g.
Similarly the Horoman peridotite, a fault-bounded 8 km*10 km *3 km mass of upper mantle exposed in Hokkaido, Japan (Niida, 1974) contains two dominant types of mafic rock, which were referred to as Gabbro I (Al-Ti augite type) and Gabbro II (Cr-diopside type) by Niida, (1984).
Consistent with this inference, at 2·5 GPa, between 1400°C and 1375°C, the equilibrium assemblage for a plagioclase-garnet clinopyroxenite from the Ronda peridotite, sample R127, is garnet, clinopyroxene and a liquid (Obata and Dickey, 1976).
library.iem.ac.ru /j-petr/12-4099/html/egc085_gml.html   (10174 words)

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