Ree minerals in carbonatite, alkaline and hydrothermal. Carbonatites may be confused with marble and may require geochemical verification. Origin of carbonatites by liquid immiscibility nature. This dyke has a fluidal texture and carries xenoliths of ultramafic rocks that can be up to 35 cm in size.
Another potential source of confusion is the use of liquid compositions in. Carbonatites carbonatites of the world, explored deposits of nb and ree. Carbonatites are igneous rocks composed of more than 50% carbonate minerals, usually spatially and temporally associated with alkaline silicate magmas, and have somewhat contentious origins. The relationship of rock types involved in carbonatite complexes has provoked much debate 14. Carbonate melts and carbonatites mineralogical society of america. Carbonatites are primarily composed of calcite or dolomite of igneous origin. Carbonatites of the world, explored deposits of nb and ree. Carbonatites article about carbonatites by the free dictionary. The formation of nacarbonatites from carich parent melts is thought to be prohibited by. The peralkaline silicate melt and the nacarbonatite liquid are immiscible at pressures of 1 kbar. Carbonatites are primarily composed of calcite or dolomite of igneous origin and silicate mineral are also present. It may thus provide an alternative perspective on the origin of deep volatilerich magmas e. Monazite dominates more than 30 carbonatiterelated ree deposits around the world, including currently exploited mineralization at bayan obo and mount weld. Glimmerites near the outer edges of the body can be nearly carbonate free, yet still contain oregrade amounts of apatite.
Carbonatite article about carbonatite by the free dictionary. Please redirect your searches to the new ads modern form or the classic form. Carbonatite and silicate magmas at dicker willem, southern namibia. Carbonation of peridotite by c02 can cause the generation of nearsolidus carbonatitic liquid from mantle peridotite at depths greater. The experimental data reported by wyllie and tuttle 1960a, b confirm that melts with a variety of compositions can precipitate calcite through a wide pressure range and through a wide temperature interval, and that these melts persist down to temperatures of the order of 600c, which agrees reasonably well with temperatures inferred for the emplacement of natural carbonatites. It was however the 1960 eruption of ol doinyo lengai in tanzania that led to geological investigations that finally confirmed the view that carbonatite is derived from magma. Carbonatite is part of wikiproject geology, an attempt at creating a standardized, informative, comprehensive and easytouse geology resource. Kempe the spatial and temporal distribution of carbonatites, a. If you would like to participate, you can choose to edit this article, or visit the project page for more information. They also have elevated concentration of strontium 700 ppm, barium 250 ppm and vanadium 20 ppm 6. Geochemistry of monazite within carbonatite related ree deposits.
The term carbonatite was introduced by the norwegian petrographer w. Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rees long and others, 2010. Origin of unusual hreemorich carbonatites in the qinling. Geological society, london, special publications, 4631, 7169. Pdf carbonatites are redefi ned using a mineralogicalgenetic. The origin of carbonatites and related rocks from the igaliko dyke. Minerals free fulltext aillikites and alkali ultramafic. Information on carbonatite deposits containing niobium and rare earth elements from around the world with grade and tonnage models, geologic setting, mineralogy, with data allowing locations of these deposits to be plotted using gis. Mattsson1 1department of earth sciences, eth zurich, clausiusstrasse 25. Most carbonatites occur close to intrusions of alkaline igneous rocks those rich in potassium or sodium relative to their silica contents or to the ultramafic igneous rocks rocks with silica contents below approximately 50 percent by weight known as kimberlites and lamproites. As one of the largest alkaline carbonatite provinces on earth fig. Essene department of geological sciences, the university of michigan, ann arbor mi 48109, usa abstract. The geology and chemistry of this rock is also unusual in comparison to carbonatite rocks worldwide.
The more than 500 fossil ca carbonatite occurrences on earth are at odds with the only active east african rift carbonatite volcano, oldoinyo lengai tanzania, which produces na carbonatite magmas. One favoured theory of origin involves the immiscible separation of carbonateand silicaterich liquids to produce the bimodal distribution of rock types typical of many complexes. Examples of concentrating and transporting agents are groundwater, seawater, and magma. Apatite is often an essential mineral and a variety of exotic minerals, such as pyrochlore, perovskite, bastnaesite, etc. A free vapor phase is present in all clinopyroxene saturation experiments and the amount of bubbles or void. Monazite dominates more than 30 carbonatite related ree deposits around the world, including currently exploited mineralization at bayan obo and mount weld. Keller carbonatite magma properties and processes, a. Naturevolume 279, pages5254 1979 download citation. Geology and petrology the eureka carbonatite dykes are located close to.
Although carbonatites make up a vanishingly small proportion of the earths crust, they account for a large number of the world. The origin and genetic relationships of the oldoinyo lengai natrocarbonatite cannot be unambiguously determined, although these rocks are regarded as a distinct variety of primary carbonatite. A common origin of carbonatite magmas daniel weidendorfer 1,2, max w. Thus it is difficult to divorce the origin of one from the origin of the other. The origin and genetic relationships of the oldoinyo lengai.
Threeliquid immiscibility and the origin of carbonatites. Nov 18, 2016 here we present observations on primary hree minerals and mocontaining fluid inclusions in the nq carbonatites, and mg isotope systematic, obtained in order to constrain carbonatite origin. Carbonatites at kola are widespread, occur in many forms, and almost all are associated with a wide. Open access article aillikites and alkali ultramafic lamprophyres of the beloziminsky alkaline ultrabasiccarbonatite massif. Between carbonatite and lamproitediamondiferous torngat. Ree minerals in carbonatite, alkaline and hydrothermal rocks. Quartzofeldspathic wall rocks are typically converted to quartz free rocks composed of alkali feldspar, aegirine and other sodic pyroxenes, and subordinate alkali amphibole. The intimate association of kimberlite and carbonatite on a small scale illustrates links in the processes.
Origin of carbonatite magma during the evolution of. Mineral deposits form because some medium serves as a concentrating and transporting agent for the ore minerals, and some process subsequently causes the transporting agent to precipitate, or deposit, the minerals. The homogenization of the silicate and carbonate material of the inclusions with the complete dissolution of daughter crystalline. The case of the carbonatitelike dyke of the madenska. Before discussing the relationship of dolomitic to calcitic carbonatite magmas and their possible means of 12 journal of african earth sciences the origin of dolomitic carbonatites. Chilwa island, lake chilwa, malawi, southeastern africa 1 25833642803.
Mineral deposit mineral deposit formation of mineral deposits. We suggest that the carbonatitelike dyke is not a normal carbonatite, but instead represents melted carbonates, which can be associated with an unexposed, deepseated, causative magmatic body. Pyrochlore grains in magnetitedolomite carbonatite and in other carbonatite. This is an early access version, the complete pdf, html, and xml versions will be available soon. Information on carbonatite deposits containing niobium and rare earth elements from around the world with grade and tonnage models, geologic setting, mineralogy, with data allowing locations of. Petrological and geochemical evidence has been presented for the eruption of primary carbonatite magmas directly from the mantle e. Carbonatite rock types do not and cannot, with rare exceptions, represent the liquid from which they crystallised. New evidence from a calcitedolomite carbonatite dyke for. Thus petrologists who favour the hypothesis of liquid immiscibility for carbonatites start with an alkalirich carbonatite magma which must lose. Carbonatites article about carbonatites by the free. A sedimentary rock that is composed of at least 80% calcium or magnesium explanation of carbonatite. Jul 11, 2008 clinopyroxene phenocrysts in fergusite from a diatreme in the dunkeldyk potassic alkaline complex in the southeastern pamirs, tajikistan, and from carbonate veinlets cutting across this rock contain syngenetic carbonate, silicate, and complex melt inclusions. Silicatecarbonate systems with bearing on the origin and.
Ferareearth elements ree ore bodies in the study area occur within carbonatite dikes composed mostly of fedolomite. New evidence from a calcitedolomite carbonatite dyke for the. New data on sr and nd isotope composition and major and trace element distribution in dolomitecalcite carbonatite dykes at bayan obo are provided, and a midproterozoic age is deduced. Aillikites and alkali ultramafic lamprophyres of the beloziminsky alkaline ultrabasiccarbonatite massif. Carbonatites are all rich in light rare earth elements 500 ppm. A discreet pulse of reduced, ironrich carbonatite magma is proposed as the origin for the magnetitedolomite carbonatite. Chemistry and origin of monazites from carbonatite dikes.
Media in category carbonatite the following 47 files are in this category, out of 47 total. The more than 500 fossil cacarbonatite occurrences on earth are at odds with the only active east african rift carbonatite volcano, oldoinyo lengai tanzania, which produces nacarbonatite magmas. Na carbonatite lavas predominantly consist of nyerereite na 2 caco 3 2 and gregoryite na, ca x, k 2x co 3 phenocrysts embedded in a heterogeneously quenched matrix of barich nyerereite, gregoryite, nasylvite, fluorite, and quenched bacasrna carbonate solid solutions gittins and jago, 1998. Clinopyroxene phenocrysts in fergusite from a diatreme in the dunkeldyk potassic alkaline complex in the southeastern pamirs, tajikistan, and from carbonate veinlets cutting across this rock contain syngenetic carbonate, silicate, and complex melt inclusions. The case of the carbonatitelike dyke of the madenska river. Jan 23, 2007 new data on sr and nd isotope composition and major and trace element distribution in dolomitecalcite carbonatite dykes at bayan obo are provided, and a midproterozoic age is deduced. Carbonatite definition and meaning collins english. Carbonatites nomenclature, average chemical compositions and element distribution, a.
This carbonatite lava is the lowest temperature origin of carbonatites by liquid immiscibility. Start this article has been rated as startclass on the projects quality scale. A number of distinct carbonatitesilicate rock associations occur that include melilititesovite, nephelinitesovite, pyroxenitesovite, and olivinerich ultrabasitesdolomitic carbonatite hornigkjarsgaard, this volume. Calcitecarbonatite sovite from alno island, sweden. This carbonatite lava is the lowest temperature pdf, html, and xml versions will be available soon. Intrusive carbonate rock associated with alkaline igneous intrusive activity. Carbonatite and alkaline intrusi onrelated rare earth. Pdf origin of unusual hreemorich carbonatites in the. Mineral deposit formation of mineral deposits britannica. Bakhchisaraitsevite occurs in cavities as free standing fanshaped aggregates with perfect cleavage or as flattened crystals of 0. Here we present observations on primary hree minerals and mocontaining fluid inclusions in the nq carbonatites, and mg isotope systematic, obtained in.
Moreover, italy seems ano malous to find carbonatitic rocks, and their presence can. As one of the largest alkalinecarbonatite provinces on earth fig. Petrogenesis of carbonatite magmas from mantle to crust. Silicate minerals such as phlogopite and sodic pyroxenes are variably present. The existence of carbonatite magmas has been generally accepted 1, but their origin remains uncertain. Carbonatites at kola are widespread, occur in many forms, and almost all are associated with a wide variety of silicate rocks. The existence of carbonatite magmas has been generally accepted1, but their origin remains uncertain. A common origin of carbonatite magmas geoscienceworld. Introduction na carbonatite lavas predominantly consist of nyerereite na 2 caco 3 2 and gregoryite na, ca x, k 2x co 3 phenocrysts embedded in a heterogeneously quenched matrix of barich nyerereite, gregoryite, nasylvite, fluorite, and quenched bacasrna carbonate solid. Approximately 50% of global rare earth element ree resources are hosted by carbonatite related deposits, of which monazite is one of the most important ree minerals. Origin of the amba dongar carbonatite complex, india and its possible linkage with the deccan large igneous province. Geochemistry of monazite within carbonatite related ree. He also proposed that calcite carbonatites be called sovites, dolomite carbonatites be called rauhaugites, biotitedolomite veined carbonatites be called beforsites, and redcolored carbonatites in which the carbonate is partially replaced by iron.
Carbonatite definition and meaning collins english dictionary. The hongcheonjaeun district is an important precambrian iron mineralization zone in korea. Carbonatitecontaining complexes are typically surrounded by an aureole of metasomatized rock that is characteristically moderately to intensely fenitized. A free vapor phase is present in all clinopyroxene saturation experiments and the amount of bubbles or void space increases with temperature. This carbonatite lava is the lowest temperature jun 18, 2017 carbonatite was introduced by the norwegian petrographer w.
Keller, 1981, 1989, and for an origin by liquid immiscibility of the only observed carbonatite lava flows, the natrocarbonatites of oldoinyo. Ol doinyo lengai had an impressive explosive eruption in 2008 see below that produced an ash plume and throughout its recent history, carbonatite ash falls and tephra are found. Pdf carbonatites and carbonatites and carbonatites researchgate. The relationship of carbonatite magma to the other magma types in this area is. The carbonatite intrusion consists of a magmatic carbonatite core, which is surrounded by a metacarbonatite and a wide fenite aureole, altogether about 9 km in diameter. The high melting temperature of calcite and the dissociation of calcite and dolomite at low pressures was long argued as evidence against a magmatic origin for carbonatites. Experimental approaches attempt to determine the routes by which crustal carbonatite magmas can be derived from c02bearing peridotite at high pressures. Carbonatite may strongly resemble marble, but chemical analysis will easily solve the question. Although not strictly zoned, generally the volume of carbonatite is greatest near the center of the intrusion, which is cut by numerous subvertical carbonatite veins fig. These deposits are widely distributed across all continents, except. Carbonatites rocks of magmatic or metasomatic origin, composed primarily of carbonates calcite, dolomite, ankerite and spatially related to complexes of ultrabasicalkalic composition. Pdf a common origin of carbonatite magmas researchgate.
Liquid immiscibility and the origin of alkalipoor carbonatites. Nacarbonatite lavas predominantly consist of nyerereite na 2 caco 3 2 and gregoryite na, ca x, k 2x co 3 phenocrysts embedded in a heterogeneously quenched matrix of barich nyerereite, gregoryite, nasylvite, fluorite, and quenched bacasrna carbonate solid solutions gittins and jago, 1998. The dykes and the neighbouring massive dolomite h8 body have similar geochemical characteristics, interpreted to indicate a carbonatitic magmatic origin. A common origin of carbonatite magmas geology geoscienceworld. A periclasedolomitecalcite carbonatite from the oka complex, quebec, and its calculated volatile composition allan h. The xenolith free carbonatites are subdivided into a finegrained calcitic to dolomitic silico carbonatite dikes, b sijvite and rauhaug. Barker extrusive carbonatites and their significance, j. Ankeritic carbonatite chilwa alkaline province, early cretaceous, 126 ma. A detailed reinvestigation of the occurrence by dunai 1989 led to the present srisotope study to assess a possible magmatic origin of the eureka carbonatite dykes. A periclasedolomitecalcite carbonatite from the oka. Carbonatitesinto the twentyfirst century journal of. Pdf the more than 500 fossil cacarbonatite occurrences on earth are at odds with. Carbonatites are igneous rocks that consist largely of the carbonate minerals calcite and dolomite.
1454 414 1342 838 576 1513 827 1369 1262 1148 1009 1106 1402 7 1102 55 355 73 807 170 1445 158 538 510 693 1346 1376 226 676 775 1432 257 1295 1272 985 397