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	Carbonatite - Wikipedia, the free encyclopedia
		Carbonatites are usually intrusions with central plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins.
		Recognition of carbonatites may be difficult, especially as their mineralogy and texture may not differ much from marble save for the presence of igneous minerals.
		Carbonatites are typically associated with undersaturated igneous rocks that are miaskitic (nearly peralkaline) rather than agpaitic (peralkaline).
	en.wikipedia.org /wiki/Carbonatite (596 words)

	Carbonatite Minerals,Carbonatite Deposits,Carbonatite Information,Carbonatite Exporters
		Carbonatites are composed of calcite (or dolomite) of the igneous origin.
		Carbonatites are rare, and is formed by unusual processes and from unusual source rocks.
		In past, it was thought that carbonatites are formed by melting of limestone or marble by the intrusion of magma, however geochemical and mineralogical data discount this.
	www.mineralszone.com /minerals/carbonatite.html (317 words)

	Isotope and Trace Element Geochemistry of Cretaceous Damaraland Lamprophyres and Carbonatites, Northwestern Namibia: ...
		The carbonatites are primarily sövites and Fe-rich beforsites emplaced as plugs and dykes.
		1) and consists of a central carbonatite plug of equigranular grey sövite with micaceous- and apatite-rich portions and ankeritic veins (Prins, 1981), and is surrounded by fenitized intrusions of nepheline syenite and syenite.
		The Okorusu lamprophyre and carbonatite magmas and the Okenyenya lamprophyres all have Pb isotope compositions broadly similar to the calculated composition of the Tristan plume at 124 Ma (assuming a plume µ = 15 and [kappa] = 4; Fig.
	library.iem.ac.ru /j-petr/6-3998/html/egb027_gml.html (9460 words)

	[No title] (Site not responding. Last check: 2007-10-31)
		Carbonatites were first reported from West-Central Arkansas in 1888;however, they were long considered to be altered lamprophyres (Croneis and Billings, 1930a,b).
		The bulk mineralogy of the carbonatites is calcite, mica (biotite, phlogopite and vermiculite alteration) and fluorapatite.
		Large biotite xenocrysts are characteristic of the carbonatites and indeed, where weathered, may be the only component visible in the field that causes recognition of the bodies as igneous.
	tsulearn.net /~barwood/carbabst.htm (548 words)

	[No title]
		Carbonatites are derived from the Earth's mantle, but there is mounting evidence that the carbon that they contain came from the crust, and had been recycled deep into the mantle during subduction.
		Carbonatite magmas differ from silicate magmas in many ways, but one of the most important is that an essential ingredient, carbonate, is not everywhere present in the mantle.
		The Rawda carbonatites are asocciated with large volumes of alkaline volcanic rocks, mainly ankaramites but with local trachytes and nephelinites, belonging to the Haybi Complex, which were partly interpreted on the basis of geochronological and geochemical data as Triassic and as within-plate magmas that erupted on volcanic islands or seamounts (Searle et al., 1980).
	www.angelfire.com /ms/snasir/CARB.htm (5550 words)

	Mineralogical Society Book Series: Publications: Mineralogical Society
		Calcite carbonatites and phoscorites are intimately associated on a metre scale, and they exhibit similar mineralogies.At the larger scale of the intrusive complex, variations in mineral assemblage delineate a broad concentric structure, with three main groups of calcite carbonatites and associated phoscorites evolving towards later REE-depleted dolomite carbonatites and.
		The differentiation, within each association, into carbonatites and phoscorites is considered to result mainly, in the early stage, from an efficient separation between coeval cumulate products, while, in later stages, the phoscorites consist mainly of pegmatitic accumulations and replacement rocks produced by fluids related to the crystallization of the associated carbonatites.
		The carbonatites are considered to be polygenetic in origin: calcite, dolomite and ankerite carbonatites are magmatic, siderite carbonatite precipitated from carbo-hydrothermal fluid and magnesite-bearing carbonatites are of hydrothermal-metasomatic origin.
	www.minersoc.org /pages/publications/phoscorites.html (2883 words)

	Carbonate-associated Deposits: Magmatic, Replacement and Residual - Mineral Deposit Profiles, B.C. Geological Survey
		Only intrusive carbonatites (in some cases further enriched by weathering) are associated with mineralization in economic concentrations which occur as primary igneous minerals, replacement deposits (intra-intrusive veins or zones of small veins, extra-intrusive fenites or veins) or residual weathering accumulations from either igneous or replacement protores.
		TECTONIC SETTING: Carbonatites occur mainly in a continental environment; rarely in oceanic environments (Canary Islands) and are generally related to large-scale, intra-plate fractures, grabens or rifts that correlate with periods of extension and may be associated with a broad zones of epeirogenic uplift.
		Carbonatite lava flows and pyroclastic rocks are not known to contain economic mineralization.
	www.em.gov.bc.ca /Mining/Geolsurv/MetallicMinerals/MineralDepositProfiles/profiles/n01.htm (1754 words)

	Carbonatites
		Carbonatites are primarily composed of calcite (or dolomite) of igneous origin.
		Geochemistry and Mantle Source(s) of Carbonatitic and Potassic Lavas from SW Uganda
		Carbonatite clearly played an important role in the Katwe-Kikorongo magmatism and it is suggested that carbonatite magma evolved from carbonate-bearing melilitite.
	faculty.uml.edu /Nelson_Eby/Research/Carbonatites/carbonatites.htm (2379 words)

	intas 94-2621 (Site not responding. Last check: 2007-10-31)
		Carbonatites are magmatic rocks that mostly occur on the continents.
		The relations between these carbonatites and the inclusions (pyroxenite, hornblendite) they sometimes contain, as well as their relations with the associated alkaline silicate rocks (pyroxenites, nepheline syenites), will also be examined.
		The Kovdor calcite- and/or dolomite-bearing carbonatites have lower REE abundance’s than the average carbonatite worldwide; this is interpreted as resulting from the fractionation of apatite and other REE-rich accessory minerals in the phoscorites.
	www.intas.be /catalog/94-2621.htm (853 words)

	Abstact LXXII, 2003
		The remaining carbonatites are considered to have been generated by differentiation (separation) from magmas represented by the associated silicate rocks that are the result of partial melting in a metasomatised lithosphere.
		Carbonatites and phoscorites (apatite-forsterite-magnetite rocks) are genetically linked; the latter correspond to cumulates of silicate and oxide minerals crystallised from a carbonatitic magma.
		At the liquidus temperature and low pressure of melilitite stability, carbonatite is not a miscible phase and may have erupted as mechanically separated, fine sprays of droplets and ash fragments that now form the matrix of the tuffs, as well as discrete porphyritic carbonatite lapilli.
	tetide.geo.uniroma1.it /riviste/permin/abstract03-1.htm (4468 words)

	Research in carbonatites and alkaline rocks by D.L. Reid
		Carbonatites from a complex in southwestern Namibia retain features such as flow-aligned phenocrysts of calcite or dolomite enclosed in a granular or spinifex-textured calcite groundmass, comb layering, and gravity layering.
		Carbonatites are grouped into: (1) coarse-grained sovites and associated silicate-oxide-phosphate-rich cumulates; (2) finer-grained alvikite intrusions, showing porphyritic and spinifex textures, comb layering and gravity-settled layers; (3) late-stage dykes, pipe breccias, veins and druses.
		In Namibia, taeniolite is present in potassic fenites derived from quartz- feldspathic gneisses and granitoids at the margin of an early sovite phase of the complex and in a radial sovite dyke emanating from this centre.
	web.uct.ac.za /depts/geolsci/dlr/carb.html (1351 words)

	Carbonatite
		Carbonatites are unusual igneous rocks that contain more than 50% carbonate minerals.
		Most carbonatites are intrusive igneous rocks that occur as volcanic plugs, dykes and cone sheets.
		This means that it is possible to get close to carbonatite lava flows and lava lakes to sample, photograph or observe them without protective clothing or other apparatus.
	it.stlawu.edu /~cnya/lenweb3b.htm (1015 words)

	Ralf Halama - Research Associate
		Because carbonatites occur almost entirely on continents, carbonatites provide useful information about one of the major problems still outstanding in mantle geochemistry, namely the nature of the subcontinental mantle.
		Carbonatites and their associated rocks also offer an opportunity to study the fundamental processes controlling fractionation in the Li stable isotope system in the temperature range typical for carbonatite crystallization (400-900° C).
		For the formation of carbonatites, liquid immiscibility is often assumed to play an important role.
	www.geol.umd.edu /~mcdonoug/halamainfo.htm (221 words)

	Geology and geochemistry of newly discovered Tertiary carbonatite occurrences near Villa Ahumada area, Basin and Range ...
		The carbonatite compositional types recognized based on major element data, in the sequence of least to most highly differentiated, are (1) magnesio-, (2) calcio- and (3) ferrocarbonatites.
		Carbonatites are associated with up to 20000 times enrichment of lanthanum and cerium with respect to chondrite.
		Finally, the Mariana carbonatite breccia is associated with about 7,928,550 short tons of rock with a grade of 0.14% ΣREE, and primitive mantle normalized trace element plots of carbonatites indicate a mantle origin of their parental melts.
	digitalcommons.utep.edu /dissertations/AAI9970437 (421 words)

	Earlham College - Geology 211 - Ol Doinyo Lengai
		Carbonatites are quite uncommon in the geologic record, and even less common at the surface as a liquid.
		Carbonatites are usually found as intrusive dikes, volcanic plugs, or cone sheets (Nyamweru, 2001).
		Essentially, this theory states that carbonatite volcanoes form where there is carbonate-rich rock that is melted to form lava.
	www.earlham.edu /~graveti/oldoinyolengai.htm (1126 words)

	IngentaConnect Carbonatites and lamprophyres of the Gardar Province - a window t... (Site not responding. Last check: 2007-10-31)
		Carbonatite magmas are considered to be ultimately derived from mantle sources, which may include lithospheric and asthenospheric reservoirs.
		Isotopic studies of carbonatite magmatism around the globe have typically suggested that more than one source needs to be invoked for generation of the parental melts to carbonatites, often involving the interaction of asthenosphere and lithosphere.
		C and O isotope data are also consistent with a mantle derivation for the carbonatite magmas, and support the theory of a cogenetic origin for the carbonatites and the lamprophyres.
	www.ingentaconnect.com /content/minsoc/mag/2003/00000067/00000005/art00003 (446 words)

	PRACTICAL ASPECTS OF CATHODOLUMINESCENCE PETROGRAPHY
		Carbonatites are represented by the Magnet Cove igneous complex, the Potash Sulfur Springs intrusive, the
		Crystals of apatite are common in the carbonatites and range from yellow luminescing grains in the Arkansas River carbonatites (fig.
		The Arkansas River Valley carbonatite apatites are frequently zoned and often have a rim of violet luminescence from rare earth enrichment.
	spectrum.troy.edu /~barwood/Cathodoluminescence.htm (2048 words)

	Petrology and Petrogenesis - Natural History Museum
		Carbonatite volcanoes are rare, with just one, at Oldoinyo Lengai in Tanzania, ever seen to erupt and about 40 more in the geological record.
		Extrusive carbonatites can give us new information on the nature of carbonate-bearing material brought to the Earth's surface from the mantle and the transport mechanisms that bring from the mantle to the crust and surface.
		We have been studying rocks from recently discovered new carbonatite localities in Italy and from the Le Bas Collection of material associated with classic locations in the African Rift Valley in western Kenya.
	www.nhm.ac.uk /research-curation/departments/mineralogy/research-groups/petrology-petrogenesis/extrusive-carbonatities.html (271 words)

	Directory of open access journals
		The petrographic study of 130 borehole samples indicates that the complex is basically made up by two rock-types, carbonatites and mica-rich rocks, and subordinately by a third unit of hybrid composition.
		Chemical data indicate that the carbonatites are strongly enriched in REE and have lower contents of Nb, Zr, V, Cr, Ni and Rb compared to the mica-rich rocks.
		Similar REE patterns for carbonatites and mica-rich rocks seem to suggest that they are related to a single parental magma, possibly of ijolitic composition.
	www.doaj.org /abstract?id=9295&toc=y (303 words)

	The origins of carbonatites and related rocks from the Gronnedal-Ika nepheline syenite complex, South Greenland; C-O-Sr ...
		The Gronnedal-Ika ring complex (1299+ or -17 Ma) in the Gardar province, South Greenland is composed of a range of layered nepheline syenites which were intruded at a late stage by xenolithic syenite and a plug of carbonatite.
		Sr isotope ratios (typically 0.703) suggest the syenites and carbonatites have not assimilated crustal rocks, and therefore the C and O isotope variation within each group is a result of isotopic evolution during fractional crystallisation.
		Despite geochemical evidence which suggests a genetic link between nepheline syenites and carbonatites, C and O isotopic evidence shows that they are not related directly by liquid immiscibility.
	minmag.geoscienceworld.org /cgi/content/abstract/61/4/515 (519 words)

	Department of Geological Sciences Colloquium (Site not responding. Last check: 2007-10-31)
		Kimberlites and carbonatites are believed to crystallize from magmas derived by low-degree partial melting of metasomatically enriched mantle peridotites.
		The world’s oldest extrusive carbonatites occur in the Kontozero paleocaldera, Kola Peninsula.
		This caldera is intruded by a diatreme composed of intimately associated carbonatites and kimberlite-like rocks.
	www.umanitoba.ca /geoscience/grads/colloquium/20022003/macbride.htm (516 words)

	General Types of Gold Deposits
		The late hydrothermal stage is commonly marked by sulfide mineralization that occupies late fractured and faulted parts of the rocks of all zones.
		Carbonatites and carbonatite-related bodies (e.g., carbonate-barite-fluorite-sulfide veins, dykes, and disseminations) are characterized by a distinctive suite of elements that includes Na, K, Fe, Ba, Sr, rare earths, Ti, Zr, Hf, Nb, Ta, U, Th, Cu, Zn, P, S, F, and more rarely Li, Be, and Pb.
		Most of the rocks comprising carbonatites are low in gold and silver (0.005 ppm Au and 0.1 ppm Ag).
	www.minelinks.com /alluvial/goldDeposits1.html (955 words)

	LIGHT PALEOPROTEROZOIC MANTLE CARBON: EVIDENCE FROM FENNOSCANDIAN CARBONATITES
		The carbonatite dike at Halpanen is 10 m wide and up to 1.5 km long, crosscutting the surrounding 1.9 Ga Svecofennian gneisses.
		In total, 10 narrow carbonatite dikes have been observed in an area of 100 square kilometers.
		Similarly to Halpanen, the carbonatites of the Petäiskoski dike swarm are highly enriched in SrO, BaO and REE, with concentrations reaching 2.3, 3.9 and 10.0 %, respectively.
	gsa.confex.com /gsa/2004AM/finalprogram/abstract_74940.htm (468 words)

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