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Topic: Dunite

Related Topics

Ultramafic

Igneous rock

Obduction

Gabbro

Peridotite

Mafic

Ophiolites

Phonolite

Andesite

Trachyte

Rhyolite

Pegmatite

Olivine

Biotite

List of rocks

	Olympus Microscopy Resource Center: Polarized Light Microscopy Gallery - Dunite
		Dunite is an intrusive igneous rock that dominantly consists of coarse grains of the pale green mineral olivine.
		Originally found in the Dun Mountain of New Zealand, dunite was given its moniker by the geologist Christian Gottlieb von Hochstetter in 1859.
		The formation of the rock, which is a common component of the oceanic lithosphere, is generally believed to arise from the effect of gravity and other forces on accumulations of dense olivine grains.
	www.olympusmicro.com /galleries/polarizedlight/pages/dunitesmall.html (249 words)

	Dunite - Wikipedia, the free encyclopedia
		Dunite (IPA: /ˈduːnʌɪt, ˈdʌnʌɪt/) is an igneous, plutonic rock, of ultramafic composition, with coarse grained or phaneritic texture.
		Dunite is rarely found within continental rocks, but where it is found, it typically occurs at the base of ophiolite sequences where slabs of mantle rock from a subduction zone have been thrust into continental crust by obduction during continental or island arc collisions (orogeny).
		Dunite typically undergoes retrograde metamorphism in near surface environments and is altered to serpentinite.
	en.wikipedia.org /wiki/Dunite (241 words)

	The platiniferous dunite pipes in the eastern limb of the Bushveld Complex: Review and comparison with unmineralized ...
		dunite and iron-rich wehrlite (average composition is Fo intermingled with barren magnesian dunite.
		the magnesian dunite pipes and the iron-rich ultramafic pegmatite,
		dunite is ascribed to flowage differentiation of new injections
	sajg.geoscienceworld.org /cgi/content/abstract/107/4/505 (649 words)

	Dunite distribution in the Oman Ophiolite: Implications for melt flux through porous dunite conduits
		Dunites in the mantle section of the Oman ophiolite represent conduits for chemically isolated melt transport through the shallow mantle beneath oceanic spreading centers.
		Dunites, measured from one-dimensional lithologic sections and digital image mosaics at a variety of length scales, range in width from ∼3 mm to ∼100 m and follow a power law with a slope of ∼1.1.
		Using the observed size/frequency relationship, the assumption that dunites form a coalescing network and the requirement that flux is conserved where dunites merge, we estimate the total flux through a porous dunite network and the fraction of that flux that remains chemically isolated.
	www.agu.org /pubs/crossref/2002/2001GC000289.shtml (431 words)

	Dunite (Site not responding. Last check: 2007-10-21)
		Dunite granular, green igneous rock composed of coarse grains of olivine, is the source of the world's supply of chromium.
		Some dunites are rich in chromite, magnetite, ilmenite, or pyrrhotite; they may also contain a small amount of pyroxene.
		It probably forms from the accumulation of dense, early crystallizing grains of olivine that sink to the bottom of low silica magma.
	ist-socrates.berkeley.edu /~eps2/wisc/dunite.html (94 words)

	Our_Work_PGE
		It is generally accepted that PGE concentration in chromitites results from the accumulation of platinum-rich alloys that segregated directly from the melt at an early stage in the evolution of the complex, followed by metasomatic replacement and remobilisation of primary platinum alloys.
		Two dunite bodies are known in the Kachkanar massif, though apparently tectonically disconnected from the magnetite-bearing gabbro: the northern, Veressovoborsky, and southern, Svetloborsky, ones both were the source of placer and eluvial platinum concentrations.
		The cavities in the consolidated part of the dunite body were created by a magma injection in the system, according to a model largely inspired from the ophiolite podiform chromitite.
	minurals.brgm.fr /texte/ourwork_PGE.htm (1846 words)

	ESS 301 - Lecture Key Points
		To the west, there are a number indicators of deep thrust (reverse) faulting associated with the plate convergence that accompanied the arrival and docking of Wrangellia, 100 million years ago.
		One indicator of extremely deep faulting (reverse faulting) is the appearance of the Twin Sisters Dunite in the North Cascades.
		This dunite is an ultramafic mantle rock that is more than 90% olivine.
	faculty.washington.edu /sechern/ess301/key/060424.html (382 words)

	CVO Website - Olivine, Peridote, Dunite (Site not responding. Last check: 2007-10-21)
		Peridotite has two varieties -- harzburgite (a rock that contains more olivine than pyroxene) and dunite (a rock consisting almost entirely of olivine).
		Peridotite typically displays a coarse crystalline texture and is both very dark and very dense.
		In harzburgite and dunite, the olivine is brown, greenish brown to fl and has a more glassy texture than the pyroxene.
	vulcan.wr.usgs.gov /LivingWith/VolcanicPast/Notes/olivine.html (375 words)

	Brown University
		In the presence of porous melt flow, such reaction often produces elongated, interconnected high porosity dunite channels in the melt migration region of the mantle.
		At moderate pressures, reaction between a lherzolite and a basalt produces a reactive boundary layer that consists of a pyroxene-free dunite and a clinopyroxene-free harzburgite (Figure 1).
		These systematic variations in grain size, mineralogy, and mineral chemistry are consistent with a model that involves preferential dissolution of pyroxene and precipitation or re-precipitation of olivine.
	www.geo.brown.edu /Faculty/YLkineticsofmeltrock.htm (556 words)

	Geology 200A - Lab 2 (Ophiolites) (Site not responding. Last check: 2007-10-21)
		Vocabulary: talc serpentine olivine bronzite clinopyroxene spinel chromite magnetite plagioclase amphibole epidote chlorite lherzolite harzburgite dunite wehrlite websterite anorthosite troctolite gabbro trondhjemite gabbro basalt chert cumulate intercumulus tectonite segregation pegmatite breccia pillow veins xenocryst restite foliation honeycomb effusive aphyric microlites phenocryst lythophysae variolites chilled.
		005 2-2d: orange/brown weathering, smooth surfaced, serpentinized (matte fl) dunite with fl grains of chromite; the rock, in as much as it is composed of olivine and chromite only, represents the residue remaining from the high temperature melting removal of all clino- and ortho-pyroxene from the primitive mantle lherzolite represented by sample 2-2c;.
		014 2-5-1-b: serpentinized layered harzburgite cumulates composed of dunite and orthopyroxenite layers; ultramafic cumulate rock.
	instruct.uwo.ca /earth-sci/200a-001/200lab2.htm (902 words)

	Ekojoki
		Most primitive dunitic olivine cumulates are found in the centre of the intrusion, pyroxenites at the contact to the migmatised mica gneisses and peridotites in between the dunites and pyroxenites.[4]
		The orbicules are surrounded by a chromite rim.
		Mineralised dunite is about 50 x 125 meters and extends to the depth of 150 meters.
	www.gsf.fi /explor/nickel/ekojoki.htm (495 words)

	SITE SUMMARIES
		Strikingly, the proportion of peridotite (harzburgite + dunite) to gabbroic rocks is the same as the proportion of gabbro to peridotite (6 peridotites/2 gabbros) collected during Shinkai Dive 427, and the proportion of peridotite to gabbro in all dredge and dive samples along the Mid-Atlantic Ridge south of the 15°20
		The low Mg# in dunite could be due to metasomatic changes in Fe/Mg during hydrothermal metasomatism, olivine crystal fractionation, or reaction of migrating melt with residual mantle peridotites.
		Similar relationships are seen in dunites from the crust–mantle transition zone in the Oman ophiolite (Godard et al., 2000; Koga et al., 2001; Korenaga and Kelemen, 1997).
	www-odp.tamu.edu /publications/209_IR/chap_01/c1_8.htm (11072 words)

	Abstracts of Results from the 1997 REU Summer Program presented at the 1998 GSA Southeastern GSA Meeting, Charleston ...
		The average dunite is 40.8wt% SiO2 44.2wt% MgO and 11.3wt% Fe2O3*.
		Metatroctolites are interlayered and chemically, mineralogically, and structurally gradational with dunite and hornblende amphibolite.
		As well, amphibolite outcrops within the dunite (analyzed as part of the REU program) are included, along with samples previously collected by Tenthorey (1994) and Willse and Ryan (1995) All are dominantly amph (hornblende)+plag, with minor mag/ilm+neph+spin(?), and local cpx and opx.
	chuma.cas.usf.edu /~ryan/REUabs.html (2208 words)

	Abstracts of Results from the 1998 REU Summer Program presented at the 1998 GSA Annual Meeting, Toronto, CA, and the ...
		Troctolite - dunite and troctolite - amphibolite are interlayered at cm to meter scales, and transitional rocks are common.
		Assemblages in the EMS rocks indicate peak P-T conditions of >11 kbar and 700-850 C. EMS, dunites and amphibolites on the western side of the complex, near the Chunky Gal Fault, preserve a prominent retrograde signature of ~525 C and 4-6 kbar.
		The dunite bodies of the Buck Creek mafic-ultramafic complex (BC) enclose metatroctolite lenses + exposures of anothosite and clinopyroxenite, and are enclosed within hbld amphibolites (metagabbro).
	chuma.cas.usf.edu /~ryan/REUabs2.html (1689 words)

	Newport Exploration Ltd. - Projects - Sat Oct 28, 2006
		Mulga Tank is a significant target for a large dunite hosted nickel sulphide deposit located approximately 250km northeast of Kalgoorlie in the Northeast Goldfields of Western Australia, an area that contains some of the world's largest nickel deposits.
		This anomaly has the characteristics for a major dunite hosted nickel sulphide deposit such as Mt. Keith, which is also located in the Northeast Goldfields area of Western Australia.
		The dunite forms part of a dominantly unexposed greenstone sequence, near the eastern exposed edge of the Yilgarn Block.
	www.newport-exploration.com /s/Projects.asp (480 words)

	Rocks of Cyprus
		As a result of Africa's movement northward the island has been pushed up from from the depths of the Mediterranean and subsequent erosion has exposed a complete cross-section of the ocean crust and portions of the mantle.
		Above the Dunite in the Mt Olympus area is a rock very familiar to those who walk the landscape of Marin, Serpentinite.
		Eventually the Dunite plays out and the other lighter minerals take their place in the stratified mantle, eventually giving way to the lighter portions of what we call the crust.
	www.marin.cc.ca.us /~jim/photos/cyprus/rocks.htm (1013 words)

	The petrogenesis and tectonic setting of ultramafic rocks from Iti and Kallidromon Mountains, continental central ...
		The dunite is considered to have been formed by assimilation of clinopyroxene and orthopyroxene, and replacement of Al-rich spinel by Cr-rich spinel, when locally ponded boninitic melts reacted with the host lherzolite.
		In both the harzburgite and dunite, subsequent differentiation of magma resulted in the formation of compositional areas poorer in Cr in the spinel grains.
		O in the formation of the harzburgite and dunite, along with mineralogical evidence, particularly Fo- and Cr-rich olivine in the dunite and high-Cr spinel in both the dunite and harzburgite, suggest a subduction-related regime for the origin of the Iti and Kallidromon ophiolites.
	pubs.nrc-cnrc.gc.ca /mineral/tcm-26744-1.html (739 words)

	REE and PGE Geochemical Constraints on the Formation of Dunites in the Luobusa Ophiolite, Southern Tibet -- ZHOU et al. ...
		REE and PGE Geochemical Constraints on the Formation of Dunites in the Luobusa Ophiolite, Southern Tibet -- ZHOU et al.
		REE and PGE Geochemical Constraints on the Formation of Dunites in the Luobusa Ophiolite, Southern Tibet
		of the dunites in the ophiolite have a similar mineralogy, comprising
	petrology.oxfordjournals.org /cgi/content/abstract/46/3/615 (427 words)

	www.mineweb.net \| co_releases Nevada Star (Site not responding. Last check: 2007-10-21)
		The focus of the program was the Fish Lake and Dunite Hill intrusions, which together comprise 150 square miles of the 271 square mile MAN Alaska project area.
		The MAN Alaska Project, which consists of five distinct project areas: Canwell, Rainy/ Eureka, Summit Hill, Dunite Hill/Fish Lake, and Broxson, is supported by a solid infrastructure: it is accessible from two paved highways and borders the Alaska Pipeline.
		The Dunite Hill/Fish Lake section (Area 1) of the MAN Alaska property is now under joint venture with Anglo American Exploration (USA), Inc. (AAEUS), who is performing its exploration program pursuant to the agreement with Nevada Star.
	www.mineweb.net /co_releases/461264.htm (725 words)

	USGS Certificate of Analysis Dunite, DTS-2 (Geochemical Reference Standards) (Site not responding. Last check: 2007-10-21)
		Material used in the preparation of this reference material was collected from a quarry located in Twin Sisters Range, approximately 20-due-miles east of Bellingham, Washington.
		The Twin Sisters dunite is composed of virtually unaltered, coarse grained enstatite bearing dunite with accessory amounts of chromite and chromium diopside (Ragan, D.M., 1963).
		Ragan, D.M., 1963, Emplacement of the Twin Sisters Dunite, Washington, American Journal of Science, 261:549-565
	minerals.cr.usgs.gov /geo_chem_stand/dunitedts2.html (405 words)

	Igneous Rock Identification
		As mentioned above, the composition of most igneous rocks can be identified using this system, formally known as the Color Index.
		The two most notable are obsidian and dunite.
		Dunite is composed almost entirely of the mineral olivine which usually contains both iron and magnesium.
	facweb.bhc.edu /academics/science/harwoodr/Geol101/labs/igneous (532 words)

	Botanical Electronic News - BEN #246
		In areas where decomposed dunite and organic material accumulate, the vegetation is a mosaic of bare dunite rock, alpine meadows and heaths.
		The plants were relatively easy to see, since their deep green fronds contrasted sharply with the orange dunite rock.
		Nearly all of the plants grew in vertical cracks on exposed dunite faces and were rooted in loamy sand derived from decomposed dunite.
	www.ou.edu /cas/botany-micro/ben/ben246.html (1712 words)

	Hydrocode simulations of impacts (Site not responding. Last check: 2007-10-21)
		A slab of dunite impacts a block composed of dunite and quartzite.
		A slab of dunite impacts a dunite block with a rectangular quartzite inclusion.
		All simulations using second-order node-coupling, artificial viscosity = 3.0 in units of the programme.
	www.maths.bris.ac.uk /~mazjmh/Work/Shock (271 words)

	PRESS RELEASE Bright Star Expands Platinum Zone to 862 Meters and Drops Mineral Claims in Alaska (Site not responding. Last check: 2007-10-21)
		A 3-D inversion model of the airborne magnetic data has identified deep-seated structural features associated with the mineralization.
		Platinum mineralization associated with a well-defined northwest trending lineament within the dunite has now been traced for 862 meters and remains open to the northwest.
		Platinum values are also associated with two distinctive 200-meter diameter circular magnetic low features characterized by highly serpentinized chromitiferous dunite.
	www.marketwire.com /mw/release_html_b1?release_id=60539 (429 words)

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