Готові списки джерел за темами / Carbonatiite

Добірка наукової літератури з теми "Carbonatiite"

Автор: Grafiati
Опубліковано: 10 грудня 2022
Оновлено: 29 січня 2023

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Статті в журналах з теми "Carbonatiite"

1

de Ignacio, C., M. Muñoz, and J. Sagredo. "Carbonatites and associated nephelinites from São Vicente, Cape Verde Islands." Mineralogical Magazine 76, no. 2 (April 2012): 311–55. http://dx.doi.org/10.1180/minmag.2012.076.2.05.

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Анотація:
AbstractThe island of São Vicente has the most abundant carbonatite outcrops in the Cape Verde Islands. A field survey of the main outcrops has shown that they consist of extrusive carbonatites, carbonatite dykes and small apophyses of intrusive carbonatite. These outcrops are spatially related to nephelinites. The compositions of the extrusive carbonatites and dykes plot close to, and within, the magnesiocarbonatite field. In contrast, the intrusive carbonatites are calciocarbonatites, with similar average strontium contents to those of extrusive carbonatites and dykes (around 4000 ppm), but remarkably low barium, niobium and total rare earth element concentrations. Whole-rock geochemistry indicates a strong affinity between the nephelinites and intrusive carbonatites, such that the latter could represent fractionation products of the same parental magma. This is in agreement with radiogenic isotope geochemistry, which shows a very restricted range of compositions in the Sr, Nd and Pb systems. Fractionation from a common parental magma occurred in two main steps: high-temperature nephelinite crystallization and high-temperature carbonatite immiscibility. The carbonatitic melts crystallized in two different environments, as follows: (1) a shallow intrusive environment, giving rise to the early calciocarbonatite cumulates; and (2) a vapour-dominated, extrusive environment, producing the later magnesiocarbonatites.
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2

Rampilova, Maria, Anna Doroshkevich, Shrinivas Viladkar, and Elizaveta Zubakova. "Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India." Minerals 11, no. 4 (March 29, 2021): 355. http://dx.doi.org/10.3390/min11040355.

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The main mass of the Sevathur carbonatite complex (Tamil Nadu, India) consists of dolomite carbonatite with a small number of ankerite carbonatite dikes. Calcite carbonatite occurs in a very minor amount as thin veins within the dolomite carbonatite. The age (207Pb/204Pb) of the Sevathur carbonatites is 801 ± 11 Ma, they are emplaced within the Precambrian granulite terrains along NE–SW trending fault systems. Minor minerals in dolomite carbonatite are fluorapatite, phlogopite (with a kinoshitalite component), amphibole and magnetite. Pyrochlore (rich in UO2), monazite-Ce, and barite are accessory minerals. Dolomite carbonatite at the Sevathur complex contains norsethite, calcioburbankite, and benstonite as inclusions in primary calcite and are interpreted as primary minerals. They are indicative of Na, Sr, Mg, Ba, and LREE enrichment in their parental carbonatitic magma. Norsethite, calcioburbankite, and benstonite have not been previously known at Sevathur. The hydrothermal processes at the Sevathur carbonatites lead to alteration of pyrochlore into hydropyrochlore, and Ba-enrichment. Also, it leads to formation of monazite-(Ce) and barite-II.
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3

FORMOSO, MILTON LUIZ LAQUINTINIE, EGYDIO MENEGOTTO, and VITOR PAULA PEREIRA. "Brazilian Carbonatites: Studies of the Fazenda Varela (SC) and Catalão I (GO) Carbonatites and their Alteration Products." Pesquisas em Geociências 26, no. 2 (December 31, 1999): 21. http://dx.doi.org/10.22456/1807-9806.21122.

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Анотація:
This paper presents some Brazilian carbonatites case studies: the Fazenda Varela (SC) and the Catalão I (Go) carbonatites. The mineralogical composition of the Fazenda Varela carbonatite is ankerite, Fe-dolomite, dolomite, synchysite and barite. Apatite and monazite are very rare accessories. The rock presents high amounts of REE, Ba, Ca, Sr, CO2 and SO3, significant Th and U, and small amounts of P, Nb and Ta. The weathering dissolves the carbonates, forms goethite and maintains barite in a saprolite facies. The laterite facies is probably related to the tertiary climate. The weathering promote Fe enrichment, followed by Mn, Th and U in the oxide phase. Ba, REE and P are fixed in the younger weathering (saprolite phase) and lost in the older weathering (laterite phase). In Catalão I Massif five hidrotermal events and the following magmatic events were identified: (1) Phoscorite and pyroxenite; (2) Banded carbonatite with alternated calcite and dolomite layers with apatite, magnetite and pyrite; (3) Magnesium carbonatite with pyrite, rare niobozirconolite and strontiamite. Catalão I carbonatites are poor in Al, Mn, Na and K. Cr, Ni, Co, Cu, Li and Zr-richer samples do occur anomalously. Nb content in carbonatitic veins is very low and suggests that these rocks are not the source for the economic concentration of this element. In both calcite and dolomite, Ba content is smaller than Sr content. Sr, Fe and Mn are mostly associated with dolomite carbonatites. The banded carbonatite is relatively REE-poor, but the magnesium carbonatite bands are REE richer than the associated calcium carbonatite bands, which are extremely poor in all REE. The REE signatures of the distinct carbonatites didn’t show anomalies.
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4

Sitnikova, Maria A., Vicky Do Cabo, Frances Wall, and Simon Goldmann. "Burbankite and pseudomorphs from the Main Intrusion calcite carbonatite, Lofdal, Namibia: association, mineral composition, Raman spectroscopy." Mineralogical Magazine 85, no. 4 (July 1, 2021): 496–513. http://dx.doi.org/10.1180/mgm.2021.56.

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AbstractThe Neoproterozoic Lofdal alkaline carbonatite complex consists of a swarm of carbonatite dykes and two plugs of calcite carbonatite known as the ‘Main’ and ‘Emanya’ carbonatite intrusions, with associated dykes and plugs of phonolite, syenite, rare gabbro, anorthosite and quartz-feldspar porphyry. In the unaltered Main Intrusion calcite carbonatite the principal rare-earth host is burbankite. As burbankite typically forms in a magmatic environment, close to the carbohydrothermal transition, this has considerable petrogenetic significance. Compositional and textural features of Lofdal calcite carbonatites indicate that burbankite formed syngenetically with the host calcite at the magmatic stage of carbonatite evolution. The early crystallisation of burbankite provides evidence that the carbonatitic magma was enriched in Na, Sr, Ba and light rare earth elements. In common with other carbonatites, the Lofdal burbankite was variably affected by alteration to produce a complex secondary mineral assemblage. Different stages of burbankite alteration are observed, from completely fresh blebs and hexagonal crystals through to complete pseudomorphs, consisting of carbocernaite, ancylite, cordylite, strontianite, celestine, parisite and baryte. Although most research and exploration at Lofdal has focused on xenotime-bearing carbonatite dykes and wall-rock alteration, this complex also contains a more typical calcite carbonatite enriched in light rare earth elements and their alteration products.
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5

Cooper, Alan F., Lorraine A. Paterson, and David L. Reid. "Lithium in carbonatites — consequence of an enriched mantle source?" Mineralogical Magazine 59, no. 396 (September 1995): 401–8. http://dx.doi.org/10.1180/minmag.1995.059.396.03.

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AbstractThe rare Li-mica taeniolite is described from the Dicker Willem carbonatite complex, Namibia, and from the Alpine carbonatitic lamprophyre dyke swarm at Haast River, New Zealand. At Haast River, taeniolite occurs in sodic and ultrasodic fenites derived from quartzo-feldspathic schists and rarely in metabasites, adjacent to dykes of tinguaite, trachyte and a spectrum of carbonatites ranging from Ca- to Fe- rich types. In Namibia, taeniolite is present in potassic fenites derived from quartz-feldspathic gneisses and granitoids at the margin of an early sövite phase of the complex and in a radial sövite dyke emanating from this centre.The occurrence of taeniolite in these totally disparate carbonatite complexes, together with examples of lithian mica from other carbonatite complexes worldwide, raises the question of the status of Li as a ‘carbonatitic element’. We argue that lithium is not a consequence of crustal assimilation or interaction, but reflects the geochemical character of the magmatic source. Li, an overlooked and little-analysed element, may be an integral part of metasomatic enrichment in the mantle, and of magmas derived by partial melting of such a source.
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6

Amores-Casals, Melgarejo, Bambi, Gonçalves, Morais, Manuel, Neto, Costanzo, and Molist. "Lamprophyre-Carbonatite Magma Mingling and Subsolidus Processes as Key Controls on Critical Element Concentration in Carbonatites—The Bonga Complex (Angola)." Minerals 9, no. 10 (September 30, 2019): 601. http://dx.doi.org/10.3390/min9100601.

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The Bonga complex is composed of a central carbonatite plug (with a ferrocarbonatite core) surrounded by carbonatite cone sheets and igneous breccias of carbonatitic, fenitic, phoscoritic and lamprophyric xenoliths set in a carbonatitic, lamprophyric or mingled mesostase. To reconstruct the dynamics of the complex, the pyrochlore composition and distribution have been used as a proxy of magmatic-hydrothermal evolution of the complex. An early Na-, F-rich pyrochlore is disseminated throughout the carbonatite plug and in some concentric dykes. Crystal accumulation led to enrichment of pyrochlore crystals in the plug margins, phoscoritic units producing high-grade concentric dykes. Degassing of the carbonatite magma and fenitization reduced F and Na activity, leading to the crystallization of magmatic Na-, F- poor pyrochlore but progressively enriched in LILE and HFSE. Mingling of lamprophyric and carbonatite magmas produced explosive processes and the formation of carbonatite breccia. Pyrochlore is the main Nb carrier in mingled carbonatites and phoscorites, whereas Nb is concentrated in perovskite within mingled lamprophyres. During subsolidus processes, hydrothermal fluids produced dolomitization, ankeritization and silicification. At least three pyrochlore generations are associated with late processes, progressively enriched in HFSE, LILE and REE. In the lamprophyric units, perovskite is replaced by secondary Nb-rich perovskite and Nb-rich rutile. REE-bearing carbonates and phosphates formed only in subsolidus stages, along with late quartz; they may have been deposited due to the release of the REE from magmatic carbonates during the hydrothermal processes.
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7

Giebel, R. J., A. Parsapoor, B. F. Walter, S. Braunger, M. A. W. Marks, T. Wenzel, and G. Markl. "Evidence for Magma–Wall Rock Interaction in Carbonatites from the Kaiserstuhl Volcanic Complex (Southwest Germany)." Journal of Petrology 60, no. 6 (May 14, 2019): 1163–94. http://dx.doi.org/10.1093/petrology/egz028.

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Abstract The mineralogy and mineral chemistry of the four major sövite bodies (Badberg, Degenmatt, Haselschacher Buck and Orberg), calcite foidolite/nosean syenite xenoliths (enclosed in the Badberg sövite only) and rare extrusive carbonatites of the Kaiserstuhl Volcanic Complex in Southern Germany provide evidence for contamination processes in the carbonatitic magma system of the Kaiserstuhl. Based on textures and composition, garnet and clinopyroxene in extrusive carbonatites represent xenocrysts entrained from the associated silicate rocks. In contrast, forsterite, monticellite and mica in sövites from Degenmatt, Haselschacher Buck and Orberg probably crystallized from the carbonatitic magma. Clinopyroxene and abundant mica crystallization in the Badberg sövite, however, was induced by the interaction between calcite foidolite xenoliths and the carbonatite melt. Apatite and micas in the various sövite bodies reveal clear compositional differences: apatite from Badberg is higher in REE, Si and Sr than apatite from the other sövite bodies. Mica from Badberg is biotite- and comparatively Fe2+-rich (Mg# = 72–88). Mica from the other sövites, however, is phlogopite (Mg# up to 97), as is typical of carbonatites in general. The typical enrichment of Ba due to the kinoshitalite substitution is observed in all sövites, although it is subordinate in the Badberg samples. Instead, Badberg biotites are strongly enriched in IVAl (eastonite substitution) which is less important in the other sövites. The compositional variations of apatite and mica within and between the different sövite bodies reflect the combined effects of fractional crystallization and carbonatite-wall rock interaction during emplacement. The latter process is especially important for the Badberg sövites, where metasomatic interaction released significant amounts of K, Fe, Ti, Al and Si from earlier crystallized nosean syenites. This resulted in a number of mineral reactions that transformed these rocks into calcite foidolites. Moreover, this triggered the crystallization of compositionally distinct mica and clinopyroxene crystals around the xenoliths and within the Badberg sövite itself. Thus, the presence and composition of clinopyroxene and mica in carbonatites may be useful indicators for contamination processes during their emplacement. Moreover, the local increase of silica activity during contamination enabled strong REE enrichment in apatite via a coupled substitution involving Si, which demonstrates the influence of contamination on REE mineralization in carbonatites.
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8

Downes, H., F. Wall, A. Demény, and Cs Szabó. "Continuing the Carbonatite Controversy Preface." Mineralogical Magazine 76, no. 2 (April 2012): 255–57. http://dx.doi.org/10.1180/minmag.2012.076.2.01.

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Анотація:
Carbonatites have always been controversial (Mitchell, 2005). Their magmatic origin was disputed in the early days of the last century, regardless of the fact that experiments clearly demonstrated the crystallization of magmatic calcite (Wyllie and Tuttle, 1960). The observation of the eruption of natrocarbonatite lava in Oldoinyo Lengai (Dawson 1962) finally convinced petrologists that they were dealing with the products of magmatic carbonate liquids. Since that time, further controversies have emerged, especially regarding the ultimate origin of carbonatite magmas, for which there are two ‘endmember’ hypotheses. The generally accepted hypothesis is based on isotopic evidence and suggests that carbonatites are from deep asthenospheric sources, such as mantle plumes (Bell, 2001; Bell et al., 2004). This fails to explain why carbonatites are essentially confined to the continental lithosphere and are extremely rare in the ocean basins (Woolley and Kjarsgaard, 2008; Woolley and Bailey, this issue), and leads to the alternative hypothesis of lithosphere-generated carbonatitic magmatism. It may be that this is simply because we have not yet understood how to identify carbonatites in oceanic regions (Bailey and Kearns, this volume), or there may be some more profound reason why carbonatites cannot form within or erupt through oceanic lithosphere.
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9

Buckley, H. A., and A. R. Woolley. "Carbonates of the magnesite–siderite series from four carbonatite complexes." Mineralogical Magazine 54, no. 376 (September 1990): 413–18. http://dx.doi.org/10.1180/minmag.1990.054.376.06.

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AbstractCarbonates of the magnesite-siderite series have been found and analysed in carbonatites from the Lueshe, Newania, Kangankunde, and Chipman Lake complexes. This series has been represented until now only by a few X-ray identifications of magnesite and three published analyses of siderite and breunnerite (magnesian siderite). Most of the siderite identified in carbonatites in the past has proved to be ankerite, but the new data define the complete solid-solution series from magnesite to siderite. They occur together with dolomite and ankerite and in one rock with calcite. The magnesites, ferroan magnesites and some magnesian siderites may be metasomatic/hydrothermal in origin but magnesian siderite from Chipman Lake appears to have crystallized in the two-phase calcite + siderite field in the subsolidus CaCO3-MgCO3-FeCO3 system. Textural evidence in Newania carbonatites indicates that ferroan magnesite, which co-exists with ankerite, is a primary liquidus phase and it is proposed that the Newania carbonatite evolved directly from a Ca-poor, Mg-rich carbonatitic liquid generated by partial melting of phlogopite-carbonate peridotite in the mantle at pressures >32 kbar.
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10

Nedosekova, I. L., V. A. Koroteev, T. B. Bayanova, P. A. Serov, V. I. Popova, and M. V. Chervyakovskaya. "On the age of pyrochlore carbonatites from the Ilmeno-Vishnevogorsky Alkaline Complex, the Southern Urals (insights from Rb-Sr and Sm-Nd isotopic data)." LITHOSPHERE (Russia) 20, no. 4 (August 31, 2020): 486–98. http://dx.doi.org/10.24930/1681-9004-2020-20-4-486-498.

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Research subject. In this research, we carried out Sm-Nd- и Rb-Sr-dating of pyrochlore carbonatite from the Vishnevogorsky niobium deposit, Ilmeno-Vishnevogorsky Alkaline Complex, Southern Urals. IVC is located in the Ural fold region and is a carbonatite complex of the linear type. Rare metal (Nb-Zr-TR) deposits and occurrences are related to IVC. The age and the duration of IVC deposits formation remains a matter of debate. To determine the age of IVC carbonatites and related niobium ore, we measured Sm-Nd and Rb-Sr isotopic compositions and concentrations of the elements in the minerals (pyrochlore, calcite, apatite, biotite) and bulk sample of pyrochlore carbonatite. Materials and methods. The Sm and Nd isotopic compositions and concentrations were determined on a Finnigan MAT-262L (RPQ) seven-collector mass spectrometer in the static regime at the Geological Institute of the Kola Scientific Center, Apatity, Russia. The Sr and Rb isotopic compositions and concentrations were determined on thermos-ionization mass spectrometer Triton Plus (“Geoanalitik”, IGG UD RAN, Ekaterinburg, Russia). Results. Age of pyrochlore carbonatites from ore zone 140 (Vishnevogorsky deposit, IVC) defined by Sm-Nd and Rb-Sr isotopic methods. Mineral Sm-Nd-isochron (5 points) indicated age 229 ± 16 Ma, mineral Rb-Sr-isochron (5 points) showed similar age 250.5 ± 1.2 Ma. Conclusions. Results Sm-Nd и Rb-Sr dating indicate that the pyrochlore сarbonatites of ore zone 140 crystallized ≈ 250 Ma ago, at the stage of the postcollisional extension, possibly, in connection with exhumation complex, which was accompanied by decompression, partial melting of rocks, involving fluids, dissolution and precipitation of Ordovician-Silurian alkaline-carbonatitе complex. Thus, the formation of the IVC carbonatites and related Nb-ore, which began in Silurian (S), continued in Permian (P) and Triassic (T1-2) and was associated with the post-collision stage of tectonic activity in the Ural Fold Belt.
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Дисертації з теми "Carbonatiite"

1

Church, Abigail Ann. "The petrology of the Kerimasi carbonatite volcano and the carbonatites of Oldoinyo Lengai with a review of other occurrences of extrusive carbonatites." Thesis, University College London (University of London), 1996. http://discovery.ucl.ac.uk/1349623/.

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Анотація:
Extrusive carbonatites are rare igneous rocks with just 37 known localities. The majority are calciocarbonatites, the principal exception being those of the active volcano, Oldoinyo Lengai, which are strongly alkaline. Unresolved questions concerning extrusive carbonatites include: 1. Why are extrusive carbonatites at Lengai chemically different from all others? 2. Could the extrusive calciocarbonatites originally have had alkaline compositions? In order to address these questions extrusive carbonatites from both Lengai and the adjacent volcano, Kerimasi, were collected and compared. A compilation of all the available data on known extrusive carbonatites is also presented. The major results documented in this thesis are: 1. Alkali carbonatites from Oldoinyo Lengai erupted in 1993 contain petrographic evidence for an origin by liquid immiscibility from a highly fractionated peralkaline silicate melt (wollastonite nephelinite). 2. The suite of silicate rocks at Kerimasi are derived from a primary olivine nephelinite by fractional crystallisation and cumulus processes. 3. Extrusive carbonatites at Kerimasi are not genetically related to the silicate suite. By contrast intrusive sovites also present, originated by liquid immiscibility from a primitive silicate magma, equivalent to a melilite, nephelinite, at low pressure. 4. Extrusive calciocarbonatites from Kerimasi were erupted directly from the mantle. They contain phenocrysts (previously interpreted as pseudomorphs after alkali carbonate) which are now thought to have been dolomite containing calcite exsolution lamellae. 5. Of the 35 other extrusive carbonatite occurrences, none show any petrographic or geochemical evidence of having originally being alkaline. Therefore extrusive carbonatites from Oldoinyo Lengai are thought to be unique. 6. Of the 37 extrusive carbonatites, 50% are associated with melilitites or melilitebearing rocks, 27% are associated with nephelinites and the remaining 23% were erupted with no associated silicate magmas.
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2

Anzolin, Henrique de Maman. "Multigerações de apatitas no carbonatito Três Estradas, sul do Brasil : significado físico-químico e implicações para a qualidade do minério fosfático." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/184646.

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As recentes descobertas de corpos carbonatíticos no estado geram interesse sobre o potencial econômico destas rochas. Associada ao Complexo Granulítico Santa Maria Chico, o carbonatito Três Estradas apresenta um elevado teor de apatita torna-o um alvo para a implantação de um empreendimento de produção de fosfato, importante para a produção de insumos na indústria agrícola. Neste projeto procurou-se examinar este mineral associado ao carbonatito Três Estradas no estado do Rio Grande do Sul, bem como no perfil de alteração intempérica gerado sobre estas rochas. Foi realizado um estudo detalhado das ocorrências deste mineral associado a este corpo carbonatítico que mostrou a presença de diferentes gerações de apatita ao longo do perfil de alteração intempérica, evidenciando processos de dissolução parcial, substituições químicas e precipitação. Confirmada a existência de apatitas de diferentes gerações, o estudo foi direcionado para caracterizar as populações de apatitas e o ambiente geoquímico associado. Dentre os métodos que foram utilizados cita-se a análise química das amostras por espectrometria de fluorescência de raios-X, microssonda eletrônica, espectroscopia de infravermelho por transformada de Fourier e espectroscopia micro Raman, análise mineralógica através da difratometria de raios X e análise petrográfica e dos elementos texturais por microscopia ótica complementada pela microscopia eletrônica de varredura. Com os resultados obtidos foi possível compreender as variações na composição química das apatitas proveniente do carbonatito e no perfil de alteração destas rochas, identificando distintos tipos de ocorrência deste mineral e caracterizando-os quimicamente, além de especular sobre as condições supergênicas que propiciaram a formação de gerações tardias do mineral elevando consideravelmente as concentrações de fosfato.
Recent discoveries of carbonatite bodies in the state of Rio Grande do Sul created interest about the economic potential of these rocks. Associated with the granulitic complex Santa Maria Chico, the Três Estradas carbonatite presents a high content of apatite, making it a target to the implementation of an adventure for the production of phosphate, an important mineral for the production of inputs for the agricultural industry. In this project, this mineral was examined, as well as the weathering profile occurring in these rocks. A detailed study of the occurrence of this mineral associated with this carbonatite body was elaborated and revealed the presence of different generations of apatite along the weathering profile, evidencing processes of partial dissolution, chemical substitutions and precipitation. Once confirmed the existence of apatite of different generations, the study was directed to characterizing the populations and the geochemical environment associated with each one. Among the methods applied were the chemical analysis of the samples by x-ray fluorescence spectroscopy, electronic microprobe, Fourier-Transform infrared spectroscopy and micro Raman spectroscopy, the mineralogic analysis by x-ray diffraction, and the petrographic and textural analysis by optic microscopy complemented by scanning electron microscope. With the results obtained it was possible to comprehend the variations in the chemical composition of the apatite from the carbonatite and in the weathering profile of these rocks, allowing the identification of different types of occurrence and its chemical characteristics, as well as speculate about the supergenic condition that favored the formation of late generations of the mineral, what elevates considerably the phosphate concentration.
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3

Luciano, Rejane Lima [UNESP]. "Petrografia e geoquímica das rochas metacarbonatíticas do Complexo Angico dos Dias, divisa Bahia/Piauí, Brasil." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/138310.

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Este trabalho verificou que as rochas metacarbonatíticas do Complexo Metacarbonatítico de Angico dos Dias (CMCAD), constituídas principalmente por calcita, apatita, olivina, flogopita e magnetita dispõem-se em dois conjuntos: um localizado na mina de fosfato da Galvani (corpo principal, Campo Alegre de Lourdes-BA) e o outro na Fazenda Pimenteira (Caracol-PI). Variação no conteúdo de apatita, minerais ferro-magnesianos e magnetita configura um acamadamento cumulático e permite individualizar cinco fácies petrográficas (contatos graduais). Além disso, exibem manto intempérico, que resulta no minério de fosfato residual (apatitito). Registram pelo menos três fases deformacionais marcadas por estruturas primárias (acamamento reliquiar - S0) que devido aos processos de transposição (D1) da foliação S1 e da deformação D2 associada às zonas de cavalgamento (S2) se mantêm de forma escassa nas áreas menos deformadas. D2 evolui para um bandamento tectônico vertical (S3) nas zonas de cisalhamento (D3). Dados isotópicos indicam que as rochas metacarbonatíticas, datadas em 2.011±6Ma (U-PB em badeleíta e zircão), originaram-se de uma fonte mantélica enriquecida e que o enriquecimento em 18O é reflexo do reequilíbrio durante o metamorfismo/ hidrotermalismo relacionado ao Evento Brasiliano. Dados petrográficos e de química mineral apontam: que a olivina altera para serpentina, tremolita, antofilita e magnetita; que é comum a exsolução de dolomita em calcitas e de ilmenita em magnetitas e; que os carbonatitos foram parcialmente silicificados. As demais rochas do CMCAD, milonitizadas e metamorfizadas em fácies anfibolito alto (mesopertitas), exibem processo de potassificação (fenitização), metassienito e metassienogranito, além de processos de sericitização, saussuritização e epidotização dos plagioclásios. O evento metassomático/hidrotermal (fácies xisto verde médio a alto) tem caráter regional e atinge além das rochas do CMCAD as rochas do Complexo Sobradinho-Remanso. Dados geoquímicos classificam as rochas metacarbonatíticas principalmente como calciocarbonatitos. Aquelas intensamente hidrotermalizadas são classificadas como ferrocarbonatitos e magnesiocarbonatitos. Indicam filiação magmática comum para todos os cinco litofácies, associada a processos de diferenciação magmática por segregação mineral.
This study found that the metacarbonatite rocks of the Angico dos Dias Metacarbonatite Complex (CMCAD), consisting mainly of calcite, apatite, olivine, phlogopite and magnetite are arranged in two sets: one located at the phosphate mine Galvani (main body, Campo Alegre de Lourdes-BA) and the other at the Farm Pimenteira (Caracol-PI). Variation in the content of apatite, iron-magnesium minerals and magnetite sets up a cumulatic layering and allows individualize five petrographic facies (gradual contacts). Furthermore, exhibit weathering mantle, which results in the residual phosphate ore (apatite-rock). Register at least three deformational phases marked by primary structures (layering reliquiar - S0) that due to the transposition process (D1) of the foliation S1 and D2 deformation associated with thrust zones (S2) remain scantily the least deformed areas. D2 evolves into a tectonic vertical banding (S3) in the shear zones (D3). Isotopic data indicate that metacarbonatite rocks, dated at 2,011 ± 6Ma (U-PB in baddeleyite and zircon), originated from a mantle source enriched and the enrichment in 18O reflects the rebalancing during metamorphism/hydrothermalism related the Brasiliano Event. Petrography and mineral chemistry data point: the olivine changes to serpentine, tremolite, anthophyllite and magnetite; which it is common to exsolution of dolomite in calcite and ilmenite in magnetite and; that carbonatites were partially silicified. The other rocks CMCAD, mylonite and metamorphosed to amphibolite facies high (perthites) exhibit potassification process (fenitization), metasyenite and metasyenogranite, and sericitization, saussuritization and epidotization processes of plagioclase. The metasomatic/hydrothermal event (medium to high greenschist facies) has regional character and reaches beyond CMCAD rocks the rocks of Sobradinho-Remanso Complex. Geochemical data classify metacarbonatite rocks mainly as calcium carbonatites. Those intensely hydrothermalized are classified as iron metacarbonatites and magnesium carbonatites. Indicate common magmatic membership for all five lithofacies, associated with magmatic differentiation processes for mineral segregation.
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4

Cerva-Alves, Tiara. "Geologia dos carbonatitos ediacaranos de Caçapava do Sul, Rio Grande do Sul, Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/157570.

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A avaliação integrada de dados de geoquímica do solo, aerogamaespectrometria (eTh), mapeamento geológico e estrutural associado à descrição de furos de sondagem e afloramentos da região de Caçapava do Sul, sul do Brasil, levou à descoberta de dois corpos de carbonatitos. Estes corpos estão localizados próximos aos limites sudeste e leste do Granito Caçapava, intrudindo o Complexo Passo Feio. O sistema é composto por alvikitos de coloração rosada seguidos por beforsitos brancos tardios, ambos na forma de corpos tabulares deformados concordantes com a xistosidade e dobras das rochas encaixantes. Análises petrográficas e avaliações utilizando microscópio eletrônico de varredura demonstraram que a calcita é o mineral predominante nos alvikitos, sendo os seguintes minerais acessórios e traço: apatita, magnetita, ilmenita, biotita, badeleita, zircão, rutilo, minerais do grupo do pirocloro e minerais de elementos terras raras (ETR). O beforsito, caracterizado pela presença abundante de dolomita, possui os mesmos minerais acessórios e traço observados nos alvikitos. A metodologia utilizada para geocronologia foi U-Pb em zircões via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), executada em uma amostra de beforsito. A idade de cristalização fornecida pelo método foi de 603,2 ± 4,5 Ma, colocando a intrusão em um contexto de ambiente pós-colisional ediacarano, com tectonismo transpressivo predominante e atividade vulcânica marcada por características shoshoníticas.
The integrated evaluation of soil geochemistry, aerogammaspectrometry (eTh), geological and structural mapping associated with description of boreholes and outcrops of Caçapava do Sul region, southernmost Brazil, led to the discovery of two carbonatite bodies. They are located near to the east and southeast of Caçapava Granite, intruding the Passo Feio Complex. The system is composed by early alvikite pink-colored rock followed by late white beforsite dikes in deformed tabular units concordant with the host rock schistosity and folds. Petrographic and scanning electron microscopy show that the alvikites are dominantly by calcite with subordinate apatite, magnetite, ilmenite, biotite, baddeleyite, zircon, rutile, pyrochlore-like and rare earth element minerals. Beforsites have the same minor and accessory minerals of the alvikites. U-Pb zircon geochronology via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was performed on a beforsite sample, yielding a 603.2 ± 4.5 Ma crystallization age, in an Ediacaran post-collisional environment with transpressive tectonism and volcanic activity market by initial shoshonitic characteristics.
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Mäder, Urs Karl. "The Aley carbonatite complex." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26006.

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The Aley carbonatite complex, a property belonging to Cominco Ltd., is 140 km north-northeast of Mackenzie, British Columbia at latitude 56°27' N, longitude 123°45' W. The complex intruded Cambrian rocks 345 ma ago near the shelf / off-shelf boundary of ancient North America and is now contained in an imbricate thrust sheet of the Northern Rocky Mountains. The circular complex is 3 km in diameter, cylindrical with respect to the third dimension and little affected by structures of the Rocky Mountains. The relationship of nearby lamprophyric dikes and the lamproitic Ospika diatreme, closely related in time, is unclear. The Aley carbonatite complex consists of an older, outer "syenite" ring (33% of the area) and a younger dolomite carbonatite core with minor calcite carbonatite "sweats". Rare-earth rich ferro-carbonatite dikes intruded the contact aureole. The contact aureole is composed of recrystallized rocks characterized by brownish weathering, but is little affected by metasomatism and shows no indication of high temperature contact metamorphism. The mineralogy and mineral chemistry were studied in detail. Over forty mineral species are described, including rare-earth carbonates (burbankite, ancylite, cordylite, huanghoite etc.), niobium oxides (pyrochlore, fersmite, columbite) and alkali-rich silicates (arfvedsonite, aegirine, richterite). Dolomite carbonatite contains apatite, pyrite and fersmite pseudomorphs after pyrochlore. Calcite carbonatite is composed of apatite, magnetite, biotite, pyrochlore, pyrite, ± richterite. The inner part of the contact aureole forms an annular, cylindrical ductile shearzone suggesting that doming was the major mechanism of emplacement. This is consistent with the circular structural trends in the carbonatite core. Temperatures deduced from field observations and mineralogy (250°C-400°C) disagree with temperatures calculated for a cooling igneous body based on a simple heat conduction model (500°C-600°C) further supporting the view that the complex was emplaced at subsolidus temperatures. Oxygen and carbon isotope ratios (δ¹⁸O = 7.7-15.4, δ¹³C = -4.7 - -6.1) and some initial Sr isotope ratios (⁸⁷Sr/⁸⁶Sr = 0.7034-0.7036) are indicative of a mantle source of carbonatite and syenite. Ceochemically, the carbonatites are enriched in the incompatible elements LREE, Th, U, Nb, Ta, Zr. The rare-earth carbonatite dikes represent a residual liquid extremely enriched in Fe, S, LREE, Sr and Ba. The "syenite" is not a .typical alkali-syenite, bearing quartz instead of felspathoids. A strong metasomatic overprint is marked by secondary aegirine and metamorphic textures. Processes by which the rocks of the Aley may be related genetically are discussed in the light of petrography, geochemistry and experimental studies.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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6

Djeddi, Asma. "Pétrogenèse des carbonatites et magmas alcalins protérozoïques d’Ihouhaouene : terrane de l’In Ouzzal, Hoggar occidental, Algérie." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG022/document.

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Le craton archéen de l’In Ouzzal représente une succession d'événements intrusifs et métamorphiques depuis l’Eburnéen qui en font un marqueur important des processus géodynamiques à travers les temps géologiques. La région d’Ihouhaouene située au N-W du terrane de l’In Ouzzal en Algérie est unique de par la présence d’intrusions protérozoïques de carbonatites associées à des roches alcalines saturées. Ces carbonatites intracontinentales comptent parmi les plus anciennes et inhabituelles de par leurs diversités et la présence de minéraux à terres rares. Les carbonatites sont pegmatitiques ou bréchiques avec des fragments de syénite. Elles sont des calciocarbonatites composées de calcite (>50 vol.%), apatite, clinopyroxène et wollastonite et sont associées à des syénites rouges ou blanches présentes sous forme massive. Les syénites sont composées d’alternance de niveaux clairs de feldspaths alcalins rouges ou de wollastonites associées aux feldspaths blancs et de niveaux sombres d’apatites et de clinopyroxènes. Les carbonatites et syénites forment une suite cogénétique caractérisée par une augmentation en SiO2 et une diminution en CaO et CO2. Les carbonatites ont des compositions en silice comprises entre 5 et 35 pds.%, 28 et 53 pds.% CaO et 11 à 36 pds.% CO2. Les syénites montrent une forte teneur en K2O (12 pds.%) et des teneurs très faibles en Na2O (1 pds.%). Les carbonatites et syénites sont riches en éléments incompatibles avec des teneurs en REE supérieures à 7000 fois les chondrites et 1000 fois les chondrites dans les syénites, respectivement, et de fortes teneurs en U, Sr et Th. Les éléments en trace dans les minéraux magmatiques (apatite et pyroxène) mettent en évidence des processus complexes à l’origine de ces roches impliquant plusieurs étapes de cristallisation fractionnée et d’immiscibilité à partir d’un magma mélilititique riche en CO2. Les minéraux des carbonatites riches en silice et des syénites blanches ont des signatures géochimiques similaires et se caractérisent par des rapports élevés en Nb/Ta typiques de magmas riches en carbonate par immiscibilité. Les syénites rouges ont des caractéristiques de liquides silicatés évolués par différentiation. Les minéraux des carbonatites pauvres en silice ont des rapports Nb/Ta très variables, sub-chondritiques (<10), indiquant une cristallisation à partir de liquides très évolués et la présence de magmas carbonatitiques tardifs. Les apatites, en particuliers, enregistrent divers épisodes magmatiques et également supergènes. Elles présentent dans certaines roches une redistribution et un enrichissement en terres rares variables qui se caractérisent par des exsolutions de britholite dans les carbonatites riches en silice et monazite dans les carbonatites pauvres en silice. Ces exsolutions traduisent des rééquilibrations locales sub-solidus avec des fluides tardi-magmatiques de composition riche en Cl-Th-REE pour l’exsolution de la britholite et S-Ca-P-CO2 pour les inclusions de monazite. L’apatite et le zircon présents dans ces roches alcalines et carbonatites, ont permis de déterminer l’âge de mise en place du complexe magmatique de Ihouahouene à 2100 Ma syn-métamorphique et de confirmer l’âge panafricain de son exhumation. L’étude pétrologique, géochimique et géochronologique des carbonatites et syénites d’Ihouhaouene a permis de mettre en évidence l’origine magmatique de ces roches et de définir les interactions fluides-roches supergènes à l’origine des enrichissements en REE. Les carbonatites et syénites d’Ihouahouene proviennent d’un faible taux de fusion partielle d’un manteau Précambrien riche en CO2. Plusieurs étapes de cristallisation fractionnée et d'immiscibilité ont permis la genèse de ces roches hybrides, piégées le long de grandes zones de cisaillement durant la période de transition Archéen /Eburnéen dans un régime extensif à l’In Ouzzal caractérisé par un environnement granulitique d’ultra-haute-température
The In Ouzzal Archaean craton represents a succession of intrusive and metamorphic events since Eburnean, and an important marker of geodynamic processes through geological time. The Ihouhaouene area located in the N-W of In Ouzzal terrane in Algeria is unique by the presence of Proterozoic carbonatite intrusions associated with silica-saturated alkaline rocks. These intracontinental carbonatites are among the oldest and exceptional because of their diversity and the presence of unusual rare earth minerals. Carbonatites are pegmatitic or brecciated with fragments of syenite. They are calciocarbonatites with calcite (> 50 vol.%), apatite, clinopyroxene and wollastonite and are associated with red or white syenites in massive outcrops. Syenites are composed of alternating light levels of red alkaline feldspar or wollastonite associated with white feldspar and dark levels of apatite and clinopyroxene. Carbonatites and syenites form a cogenetic suite characterized by an increase in silica and decrease in calcium and CO2 content. The carbonatites have silica content ranging from 5 to 35 wt.%, 28 to 53 wt.% CaO, and 11 to 36 wt.% CO2. Syenites have high K2O (12 wt.%) and low Na2O content (1 wt.%). Carbonatites and syenites have high incompatible element concentrations with high REE content (7000*chondrites and 1000*chondrites, respectively) and high U, Pb, Sr and Th content. Trace elements (eg. Rare Earths, Nb-Ta, Zr-Hf) in magmatic minerals (apatite-pyroxene) of carbonatites and syenites reveal complex magmatic processes at the origin of these rocks involving several stages of fractional crystallization and immiscibility from a CO2-rich melilititic magma. Silica-rich carbonatites and white syenites are characterized by high Nb/Ta, Y/Zr and Rb/Sr ratios, typical of carbonate-rich magmas by immiscibility. The red syenites have characteristics of immiscible differentiated silicate melt. Silica-poor carbonatite minerals have variable subchondritic Nb/Ta (<10) indicating crystallization from highly evolved liquids and the presence of late carbonatitic magmas. Apatites, in particular, record various magmatic and supergene processes. They present, in some rocks, redistribution and enrichment in rare earth elements, which are characterized by exsolutions of britholite in silica-rich carbonatites and monazite-quartz-calcite inclusions in silica-poor carbonatites. These minerals reflect local sub-solidus re-equilibration with late-magmatic fluids rich in Cl-Th-REE for the exsolution of britholite and S-Ca-P-CO2 for monazite inclusions. The apatite and zircon present in these alkaline and carbonatite rocks, allow determination of the syn-metamorphic crystallization age of the Ihouahouene magmatic complex at 2100 Ma and confirm the pan-African age of its exhumation. The petrological, geochemical and geochronological study of Ihouhaouene carbonatites and syenites highlights the magmatic origin of these rocks and constrains the fluid-rock interactions at sub-solidus conditions leading to REE-enrichment. The carbonatites and syenites result from a low partial melting rate of a CO2-rich Precambrian mantle. Several fractional crystallization and immiscibility stages allowed the genesis of these hybrid magmas, trapped along large shear-zones during the Archean/Eburnean transition period in the In Ouzzal terrane, characterized by extensive deformation in ultra-high-temperature granulitic environment
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Rahman, Aklaqur. "Alnö Carbonatite: A Future Moneymaker?" Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328062.

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Carbonatites are rare igneous rocks, which contain at least 50 %, carbonate minerals. They are often found along with alkaline silicate rocks, meaning that they contain relatively large amounts of Na2O and K2O, and important tools to understand mantle processes. Importantly, carbonatites are known to be rich in REE (Rare Earth Elements), compared to other magmatic rocks. The Alnö complex is located in the northern part of the island of Alnö, northeast of Sundsvall and is one of the biggest ring-shaped intrusions of the alkaline and carbonatite sort. The origin of carbonatites is not fully known yet but they may have resulted from a mantle plume, and absolute dating methods indicate that the age of the Alnö carbonatites are around 600 Ma. A large amount of carbonatites have been found in the Alnö complex and the purpose of this thesis is to assess whether the Alnö complex and its carbonatites can become a potential source of REEs and if it can be profitable to mine these. The research has been conducted by first analyzing samples from the Alnö complex in thin sections through a light polarising microscope. The thin sections were photographed with a focus on apatite crystals, since apatite are hosts of REE. The apatites in the thin sections are crystals with high relief, sub-rounded and white-grey in color in a calcitic matrix. The images of the apatite were then edited with photoshop, to graphically isolate the apatite. The processed images were then analyzed in a program called “ImageJ” to calculate the total area of apatites in the thin sections and the area percentage of apatites. The area percentage helps to give an estimation of how much REE that can occur in the carbonatites of the Alnö Complex. A recent 3D- analysis of the Alnö complex using petrophysical and geophysical methods indicated the volume of the complex, which when coupled with our apatite data, allows us to estimate the total REE volume. The estimation of occurrences of apatites was calculated to around 13 % of the carbonatites in the Alnö complex. The cost to mine the REEs was much higher than the market price of the REEs. So the Alnö carbonatites are not profitable to mine for REEs today.
Karbonatit är en ovanlig bergart som innehåller minst 50 procent karbonater, därav namnet. De hittas ofta i samband med alkaliska silikat-bergarter, vilket innebär att de innehåller till stor del natriumoxid och kaliumoxid samt kisel, och är viktiga för att kunna förstå processer i manteln. Karbonatiter är kända för att vara innehållsrika på sällsynta jordartsmetaller, även kända som REE, jämfört med andra magmatiska bergarter. Alnökomplexet ligger i den norra delen av Alnön, nordost om Sundsvall och är ett av världens största alkaliska och karbonatit-ringkomplex, med en radie på 2,5 km. Dess ursprung i jordens inre är okänt men det tros vara ett resultat av en mantelplym, smältor från manteln som stiger mot ytan, och åldersdatering via absoluta dateringsmetoder tyder på att karbonatiterna är nästan 600 Ma. Stora mängder karbonatiter har hittats i Alnökomplexet och syftet med detta arbete är att bedöma om Alnökomplexet potentiellt kan bli gynnsam som källa för prospektering av sällsynta jordartsmetaller, ur ekonomisk synpunkt. Detta utfördes genom att analysera prover från Alnökomplexet samt studera data från Magnus Anderssons arbete om Alnökomplexet. Proverna analyserades med hjälp av en mikroprob som fotograferade apatiten, vita kristaller i ett mörkgrå matrix, då apatit indikerar på hög sannolikhet för REE-förekomst. Sedan redigerades dessa bilder med Photoshop och Paint, där andra kristaller redigerades bort så att det enda som var kvar var de vit-gråa utåtstickande kristallerna mot ett kalcitrikt matrix. Med ett annat program som heter ImageJ beräknades arean av dessa kristaller samt procenten av arean som apatiterna utgör i tunnslipen. Detta gav en viss uppskattning på hur stor mängd REE som kan förekomma i Alnökarbonatiter. Resultatet jämfördes med data från Magnus Andersson som har gjort en 3D- undersökning av karbonatiter under Alnö-komplexet. Apatiten utgjorde en area på 13 % och mängden REE var inte tillräckligt stor mängd relativ marknadspriserna samt utvinningskostnader för att räknas som vinstgivande.
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Mollex, Gaëlle. "Architecture de la plomberie du volcan carbonatitique Oldoinyo Lengai : nouvelles contraintes sur la source, les transferts hydrothermaux, et la différenciation magmatique dans la chambre active." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0123/document.

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Анотація:
La particularité de l’Oldoinyo Lengai à émettre des laves natrocarbonatitiques fait de ce volcan un laboratoire naturel pour l’étude de la genèse de ces magmas. De nouvelles mesures isotopiques en hélium nous ont permis de constater que la signature des fumerolles est constante depuis 1988 malgré le changement morphologique considérable du cratère sommital lors de la dernière éruption subplinienne de 2007-2008. L’alternance des éruptions explosives et effusives n’engendre donc aucune modification majeure dans l’organisation du système hydrothermal qui est par conséquent profondément enraciné. Les xénolites cogénétiques qui ont été émis lors de l’éruption de 2007-2008 permettent d’étudier directement les processus magmatiques qui se déroulent dans la chambre magmatique active. La comparaison des signatures isotopiques des gaz rares (hélium) de la chambre magmatique et des volcans silicatés de la région d’Arusha montre que les deux types de magmatisme ont une source analogue identifiée comme un manteau lithosphérique subcontinental préalablement métasomatisé par des fluides asthénosphériques. De plus, ces signatures isotopiques confirment l’absence de contaminations crustale lors de la remontée du magma entre le manteau source et la surface. Une description pétrographique de détail couplée à une approche thermobarométrique, ainsi qu’à la détermination des modèles de solubilité des volatils dans les liquides phonolitiques, nous a permis d’identifier l’évolution du liquide dans la chambre magmatique et ses paramètres de stockage. Les résultats nous révèlent que le magma injecté en 2007 a une composition phonolitique et des teneurs élevées en volatils (3.2 wt.% de H2O et 1.4 wt.% de CO2) ainsi qu’une température d'environ 1060° C. Ce magma évolue ensuite dans la chambre magmatique crustale se trouvant à 11.5±3.5 km de profondeur jusqu’à atteindre une composition de néphélinite et une température de 880°C. Pendant sa différenciation, le magma silicaté s’enrichit en calcium, sodium, magnésium et fer alors que sa concentration en silice, potassium et aluminium décroit. Ces résultats concordent avec les précédents relatifs à cette éruption, ou aux produits volcaniques plus anciens émis tout au long de la vie du volcan. Cette similarité suggère qu’aucun changement majeur n’ait eu lieu dans l’organisation de la plomberie du volcan Oldoinyo Lengai au cours de son évolution. Les mesures en éléments traces (REE, HFSE et LILE) dans les minéraux cristallisés lors de cette séquence de différenciation, et les inclusions magmatiques associées montrent un enrichissement pouvant atteindre de 100 à 1000 fois la composition du manteau primitif. Une étude expérimentale préliminaire s’appuyant sur la composition du liquide de recharge (phonolite) et les conditions (P, T) identifiées pour la chambre magmatique nous a permis de reproduire l'immiscibilité entre un liquide silicaté et carbonatitique, processus à l’origine de la formation des carbonatites de l’Oldoinyo Lengai. La poursuite de ces travaux expérimentaux permettra de mieux contraindre la genèse des magmas carbonatitiques et ainsi comprendre les processus en jeux dans l’enrichissement en éléments traces des magmas carbonatitiques
The uniqueness of Oldoinyo Lengai to emit natrocarbonatite lavas makes this volcano a natural laboratory to study the genesis of these magmas. New helium isotopic data permit to assert that the signature of the fumaroles has been constant since 1988 despite the radical morphological change of the summit crater after the last sub-Plinian eruption in 2007-2008. The alternation of the effusive and explosive eruptions does not cause major modifications in the hydrothermal system architecture, which is inferred to be deeply rooted. Cognate xenoliths that were emitted during the eruption in 2007-2008 represent a unique opportunity to document the igneous processes occurring within the active magma chamber. The comparison between the noble gas (helium) isotopic compositions of the active magma chamber and those of the other silicate volcanoes of the Arusha region indicates that both types of magmatism have similar sources, identified as being a typical sub-continental lithospheric mantle, which was previously metasomatized by asthenospheric fluids. Moreover, these isotopic signatures confirm that no crustal contamination has occurred during the magma ascent from the mantle to the surface. Detailed petrographic descriptions coupled to a thermo-barometric approach, and to the determination of volatile solubility models for a phonolite composition, allow us to identify the melt evolution at magma chamber conditions and the storage parameters. These results indicate that the magma injected in 2007 has a phonolitic composition and contains a high amount of volatiles (3.2 wt.% H2O and 1.4 wt.% CO2) as well as a temperature around 1060° C. This magma subsequently evolved in the crustal magma chamber located at 11.5 ± 3.5 km depth until reaching a nephelinite composition and a temperature of 880°C. During the differentiation in the magma chamber, the silicate magma is enriched in calcium, sodium, magnesium and iron, whereas the content of silicate, potassium and aluminum decreases. Our results support previous studies related to this eruption, and are similar to the historical products emitted during the whole volcano history, permitting the suggestion that no major modification in the plumbing system has occurred during the Oldoinyo Lengai evolution. The trace elements (REE, LILE and HFSE) measured in the minerals and melt inclusions reveal a concentration reaching 100 to 1000 times the primitive mantle composition. A preliminary experimental study based on the recharge melt composition (phonolite) and identified magma chamber conditions (P, T) permits to reproduce the immiscibility between silicate and carbonatite liquids, key processes at the origin of the Oldoinyo Lengai carbonatites. The continuation of this experimental study will lead to a better comprehension of the carbonatite genesis, thus improving our understanding of the processes that are responsible for the enrichment in trace elements
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9

Broom-Fendley, Sam Louis. "Targeting heavy rare earth elements in carbonatite complexes." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/18490.

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The HREE are generally considered to be the most critical of the REE, indispensable for many high-tech applications such as smart-phones and electric vehicles. Currently, carbonatites are the main source of REE due to their high REE grade; most carbonatites, however, are HREE-poor. This thesis presents the findings on HREE mineralisation at the Songwe Hill carbonatite, in the CAP of south-eastern Malawi. Across all carbonatite types at Songwe, whole-rock Y and P2O5 concentrations correlate positively, indicating that phosphate minerals have a strong control over the HREE contents. This is confirmed through textural and geochemical analyses (LA ICP-MS and EPMA) of apatite, which show that it can be subdivided into 5 different types (Ap-0–4), found at different stages of the paragenetic sequence. The chemistry of each of these apatite types becomes progressively more HREE-enriched, up to 3 wt. % Y2O3, and ultimately culminating in xenotime crystallisation. Cross-cutting relationships indicate that HREE-enriched apatite formed as an early crystallisation product from a late-stage, carbonatite-derived hydrothermal fluid. It is evident that LREE-fluorcarbonate mineralisation occurred after apatite crystallisation and it is assumed that crystallisation of all hydrothermal phases was though the evolution of a single fluid, rather than several different fluids. The apatite composition is compared to a compilation of analyses of apatite from other carbonatites and granitoids, as well as new analyses of late-stage apatite from the Kangankunde and Tundulu carbonatites, Malawi. Based on these analyses, it is concluded that apatite from Songwe has the highest HREE concentration compared to apatite from any previously analysed carbonatite. However, apatite from the Tundulu carbonatite has a similar geochemistry and paragenesis to the HREE-rich apatite from Songwe, suggesting that late-stage HREE enrichment may be a common process in carbonatites. In order to elucidate the fluid conditions which led to HREE mineralisation, new fluid inclusion and stable isotope data are presented to complement the mineralogical data. The fluid inclusions constrain the minimum temperature of apatite crystallisation of 160 °C, and most homogenisation temperatures in apatite are between 160-360 °C. Inclusions from apatite are CO2-rich, and it is suggested that transport of the REE occurred in carbonate complexes. Stable isotope data were obtained from both conventional C and O analyses of carbonates and from a novel method developed for acquiring δ18OPO4 from apatite. A conceptual model involving the simultaneous cooling and mixing of magmatically-derived and meteoric fluids is suggested. Two possible causes of REE fractionation are suggested: (1) a crystal-chemical control and (2) control through preferential stability of LREE and HREE complexes. However, neither mechanism is equivocal and further work on the stability of carbonate complexes is suggested in order to better understand REE mineralisation at carbonatites In addition to results on the HREE mineralisation in carbonatites, new data on the mineralogy, geochemistr y and age of the Songwe Hill carbonatite and the closely-associated Mauze nepheline syenite intr usion are presented. Songwe compr ises three stages of intr usion (C1–3): (C1) sovitic calcite carbonatite, (C2) alvikitic calcite-carbonatite and (C3) Fe-rich carbonatite. The LREE grade increases with the increasing Fe-content of the intrusion, as is common at many REE-rich carbonatites. Later-stages of the intrusion include apatite-fluorite veins (C4) and Mn-Fe-veins. The former is a volumetrically minor stage, but can contain up to 1 wt. % Y2O3, and the latter is formed through oxidation of carbonatite by supergene fluids. Samples analysed from Mauze show that it is REE- and P2O5-poor, with MREE-depleted REE distributions. U-Pb dating of zircons from Songwe and Mauze show that they are 131.5 ± 1.3 and 133.1 ± 2.0 Ma, respectively. The close temporal association of each intrusion suggests that Mauze could be a ‘heat-engine’ for hydrothermal mineralisation at Songwe.
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10

Norton, Gillian Elizabeth. "The physical properties of carbonatite and silicate magmas." Thesis, Lancaster University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316563.

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Книги з теми "Carbonatiite"

1

Bell, Keith, and Jörg Keller, eds. Carbonatite Volcanism. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79182-6.

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2

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Goldray Carbonatite Complex, district of Cochrane. Toronto, Ont: Ministry of Northern Development and Mines, Mines and Minerals Division, 1988.

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3

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Argor Carbonatite Complex, district of Cochrane. Toronto, Ont: Ministry of Northern Development and Mines, Mines and Minerals Division, 1988.

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4

Sage, R. P. Carbonatite - alkalic rock complexes in Ontario: Big Beaver House Carbonatite Complex, District of Kenora. Toronto, Ont: Ministry of Northern Development and Mines, 1987.

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5

Kresten, Peter, and Valentin R. Troll. The Alnö Carbonatite Complex, Central Sweden. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90224-1.

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6

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Cargill Township Carbonatite Complex, district of Cochrane. Toronto, Ont: Ontario Ministry of Northern Development and Mines, Mines and Minerals Division, 1988.

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7

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Schryburt Lake Carbonatite Complex, district of Kenora. Toronto, Ont: Ontario, Ministry of Northern Development and Mines, Mines and Minerals Division, 1988.

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8

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Borden Township carbonatite complex, district of Sudbury. Toronto, Ont: Ontario Ministry of Northern Development and Mines, 1987.

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9

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: "Carb" Lake Carbonatite Complex, district of Kenora. Toronto, Ont: Ministry of Northern Development and Mines, 1987.

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10

Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Spanish River Carbonatite Complex, district of Sudbury. Toronto, Ont: Ministry of Northern Development and Mines, 1987.

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Частини книг з теми "Carbonatiite"

1

Kresten, Peter, and Valentin R. Troll. "An Introduction to Carbonatites and Carbonatite Complexes." In The Alnö Carbonatite Complex, Central Sweden, 1–53. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90224-1_1.

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2

Singh, Yamuna. "Carbonatites." In Society of Earth Scientists Series, 137–78. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-41353-8_4.

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3

Milashev, Vladimir A. "Alkali Basaltoid and Carbonatite Diatremes." In Explosion Pipes, 127–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-73258-4_12.

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4

Kaminsky, Felix V. "Carbonatitic Lower-Mantle Mineral Association." In The Earth's Lower Mantle, 205–28. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55684-0_6.

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5

Jones, Adrian P., Matthew Genge, and Laura Carmody. "10. Carbonate Melts and Carbonatites." In Carbon in Earth, edited by Robert M. Hazen, Adrian P. Jones, and John A. Baross, 289–322. Berlin, Boston: De Gruyter, 2013. http://dx.doi.org/10.1515/9781501508318-012.

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6

Wright, J. B. "The Permo-Triassic dolerites and carbonatites." In Geology and Mineral Resources of West Africa, 126–28. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-015-3932-6_14.

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7

Kresten, Peter, and Valentin R. Troll. "Alnö Minerals." In The Alnö Carbonatite Complex, Central Sweden, 55–90. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90224-1_2.

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8

Kresten, Peter, and Valentin R. Troll. "Geochemistry and Alnö as an Economic Reserve." In The Alnö Carbonatite Complex, Central Sweden, 91–119. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90224-1_3.

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9

Kresten, Peter, and Valentin R. Troll. "Excursion Guide." In The Alnö Carbonatite Complex, Central Sweden, 121–78. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-90224-1_4.

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10

Knudsen, C. "Pyrochlore Group Minerals from the Qaqarssuk Carbonatite Complex." In Lanthanides, Tantalum and Niobium, 80–99. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-87262-4_3.

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Тези доповідей конференцій з теми "Carbonatiite"

1

Massey, Skylar, and Maya Kopylova. "Fenitization of ultramafic rocks around late carbonatites in the Kovdor Massif (Kola Alkaline Carbonatitic Province)." In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.6356.

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2

Walter, Benjamin, R. Johannes Giebel, Matthew Steele-MacInnis, Michael A. W. Marks, Jochen Kolb, and Gregor Markl. "Fluid release in carbonatitic systems and its implication for carbonatite magma ascent, compositional evolution and REE-mineralization." In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.5590.

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3

Shavers, Ethan, Abduwasit Ghulam, and John Encarnacion. "CARBONATITE WEATHERING MINERALOGY." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-287256.

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4

Song, Wenlei, Cheng Xu, Jindrich Kynicky, and Martin Smith. "Heavy Rare Earth Element (HREE) Enrichment in Carbonatites: A Case Study from a Xenotime-Bearing Carbonatite REE Deposit in Bachu, Xinjiang of China." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2436.

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5

Sun, Weidongsun, Lipeng Zhang, Guozhi Xie, Chris Hawkesworth, and Robert Zartman. "Carbonatite Formed Through Diamond Oxidation." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2507.

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6

Mororó, Emanuel, Marta Berkesi, and Tibor Guzmics. "Composition of carbonatite-related orthomagmatic fluids." In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.7996.

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7

Vasyukova, Olga, Anthony E. Williams-Jones, Guillaume Matton, Christian Beaulieu, and Marc Lavoie. "Phoscorite – The ‘Secret Weapon’ of Carbonatite Niobium-Enrichment." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2669.

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8

Giebel, R. Johannes, Benjamin F. Walter, Michael A. W. Marks, and Gregor Markl. "Mica Compositions Record Carbonatite – Silicate Wall-Rock Interaction." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.826.

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9

Forir, Matt, and Donald Hoover. "CARBONATITE VOLCANISM AS A MECHANISM FOR SILCA MOBILIZATION." In GSA Connects 2022 meeting in Denver, Colorado. Geological Society of America, 2022. http://dx.doi.org/10.1130/abs/2022am-382719.

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10

Polák, Ladislav, Lukáš Ackerman, Tomáš Magna, Michael Bizimis, and Vladislav Rapprich. "Lu–Hf Isotope Systematics of Carbonatites." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2100.

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Звіти організацій з теми "Carbonatiite"

1

Richardson, D. G., and T. C. Birkett. Carbonatite-associated deposits. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208032.

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2

Richardson, D. G., and T. C. Birkett. Residual carbonatite-associated deposits. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/207966.

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3

Richardson, D. G., and T. C. Birkett. Gîtes associés à des carbonatites. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208033.

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4

Woolley, A. R., and B. A. Kjarsgaard. Carbonatite occurrences of the world: map and database. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2008. http://dx.doi.org/10.4095/225115.

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5

Richardson, D. G., and T. C. Birkett. Gîtes résiduels associés à des carbonatites. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/207967.

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6

Peterson, T. D., J. M. J. Scott, and C. W. Jefferson. Uranium-rich bostonite-carbonatite dykes in Nunavut: recent observations. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2011. http://dx.doi.org/10.4095/288751.

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7

Sappin, A. A. Role in sub-activity from IOA-REE to carbonatite. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/329140.

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8

Desbarats, A. J., J. B. Percival, P. Pelchat, J. Sekerka, I. Bilot, I. Girard, and P. Gammon. Geoenvironmental characterization of carbonatite tailings, Saint Lawrence Columbium Mine, Oka, Québec. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2020. http://dx.doi.org/10.4095/327572.

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9

Baragar, W. R. A., U. Mader, and G. M. Lecheminant. Lac Leclair carbonatitic ultramafic volcanic centre, Cape Smith Belt, Québec. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1992. http://dx.doi.org/10.4095/132853.

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10

Charbonneau, B. W., and D. D. Hogarth. Geophysical expression of the carbonatites and fenites, east of Cantley, Quebec. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1988. http://dx.doi.org/10.4095/122640.

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