Dissertations / Theses: 'Carbonatites'

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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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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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Bonas, Thiago Bastos. "Aplicação de índice mineralógico como apoio na avaliação de reservas da mina de fosfato de Cajati-SP." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/44/44137/tde-17042007-094628/.

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A mina de fosfato de Cajati localiza-se a 230 km a sudeste da cidade de São Paulo. Nela aflora, de forma alongada segundo a direção N27ºW, um corpo de carbonatito mineralizado a apatita. O corpo mineralizado é subdividido em unidades litológicas a partir de variações nas características físicas (estruturas) e mineralógicas da matriz carbonática, dos principais acessórios e menores constituintes (textura e proporções). Dentro das unidades litilógicas existentes destacam-se a Zona de Xenólitos e Zonas de Diques, regiões caracterizadas por misturas entre magnetita-clinopiroxenitos, rocha encaixante e estéril com relação à mineralização de fosfato, e carbonatito em proporções que podem chegar a quase 100% de clinopiroxenito. Observam-se ainda zonas de reação, no contato entre as rochas descritas, caracterizando um bandamento centimétrico de composição silicática / carbonática com mineralogia peculiar e que na maioria das vezes são mineralizados economicamente a apatita. Considerando as Zonas de Xenólitos e de Diques como de aproveitamento parcial em função da presença do clinopiroxenito estéril e que as relações de distribuição espacial desta fase contaminante é errática sem qualquer controle geológico conhecido de distribuição, buscou-se estabelecer indicadores que permitem a caracterização percentual entre minério e estéril contidos nesta região. Para tanto foram realizados estudos de relação entre a composição química e a mineralogia do minério que permitiram estabelecer tais índices, os quais aplicados aos dados de análises químicas obtidos a partir de testemunhos de sondagem rotativa e de percussão (pó de perfuratriz) associados a parâmetros de lavra permitiram estabelecer níveis de aproveitamento mineral para as rochas existentes nestas unidades litológicas. Os indicadores matemáticos se apoiaram nos teores de sílica que refletem as proporções de silicatos (flogopita, olivina e piroxênio) e estabelecem nítidas fronteiras composicionais entre as três litologias presentes nas zonas de xenólitos, e definiram a Função Xenólitos. As variáveis mineralógicas apóiam as determinações de potencialidades volumétricas dos recursos discretizados no modelo de blocos de longo prazo e o aproveitamento das frentes nos planos de pré-lavra.
The Cajati phosphate mine is located 230 km southeast of São Paulo city. The ore body is composed by carbonatites mineralized with apatite, which are disposed in plant as an ellipse N27ºW oriented. The carbonatite is subdivided in lithologics units defined by variations in the physical aspects (structures) and the mineralogical characteristics of the carbonatic matrix, mainly related with the principal accessories and smaller constituents (texture and proportions). Xenoliths zones and Dikes zones are remarkable among the lithological units, they comprise portions characterized by mixtures of carbonatite and magnetite-clinopiroxenites, the hosting waste rock, in proportions that can reach almost 100% of clinopiroxenite. Some reaction zones are observed in the described rocks contact, characterizing centimetric bands (silicatic / carbonatic composition) with peculiar mineralogy that are frequently mineralized. Considering the Xenoliths zones and Dikes zones only partially profitable in function of the presence of the clinopiroxenite waste and that the spatial distribution of this contaminant rock is erratic without any geological known settings, efforts were applied in the establishment of mineralogical indicators to define the relative proportions of the constituent rocks. Stechiometric relationships between chemical and mineralogical characteristics associated with mining parameters allowed to set up levels of mineral profitability for these lithological units, which were applied in the data obtained by rotative and percussion drilling. Mathematical indicators based on silica grades, which reflect the silicates (phogopite, olivine and pyroxene) proportions, established a clear compositional division between the three litologies present in the xenoliths zones and defined the Xenoliths Function. The mineralogical variables support the profit potentiality definition for the ore resources associated with these assimilation zones, which were applied in the block model and are also used in the mining fronts.

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Roopnarain, Sherissa. "Petrogenesis of Carbonatites in the Alnö Complex, Central Sweden." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-215436.

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The Alnö Complex is a Late Precambrian alkaline and carbonatite intrusion (c. 30km2) into Early Proterozoic country rock that extends from the north east, to the north western shoulder of Alnö Island. Carbonatites are rare among volcanic provinces, with Oldoinyo Lengai of northern Tanzania being the only active carbonatite volcano in the world today. The high carbonate mineral volumes and rare earth element (REE) concentrations of carbonatites, in combination with the intrusive-extrusive nature of their suites contribute to the rarity of these rocks. Carbonatites, through their peculiar petrological and geochemical compositions, provide vital insights to the composition and condition of the Earth’s mantle. The genesis of the Alnö carbonatites and their relation to other lithological units at the complex is however, only partially understood. This stems from the epistemological division of carbonatites as having either a ‘magmatic’ or ‘reactive’ origin. This study focuses on sampled carbonatites from the Alnö Complex, employing an oxygen and carbon isotope approach on their native calcite, complemented with petrological and mineralogical methods in order to constrain petrogenesis. As a reference, oxygen and carbon isotope data of calcite from an earlier Alnö investigation as well as from an array of data from comparative alkaline complexes elsewhere are also discussed. The combined data and the derived findings support a scenario that is consistent with the ‘magmatic’ model wherein carbonatites have a primary mantle-derived origin, and prospectively stem from a parent magma akin to that of Oldoinyo Lengai, but have experienced a degree of silicate and sedimentary assimilation. The extraction of the Alnö carbonatites for their rare earth metals is a looming possibility due to the current volatility in the rare earth market. The risks and opportunities involved in this kind of natural resource extraction provide a context wherein sustainable development paradigms can be applied. The capacity of the Alnö environment to withstand the impact of development in the mining sector is discussed through a perspective of establishing a quarry, and quarry-related methods for rare earth extraction.

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Hodgson, Neil Andrew. "Carbonatites and associated rocks from the Cape Verde Islands." Thesis, University of Leicester, 1985. http://hdl.handle.net/2381/35041.

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Carbonatite magmas are alkali-bearing, ionic melts, analogous to synthetic carbonate melts. REE complexing suggests that carbonato-complexes dominate the melt, and these are more stable for the LREE than the HREE, leading to the extreme LREE/HREE enrichments characteristic of carbonatites. Crystal settling is viable in static magma chambers. however in thin carbonatite dykes as seen on San Vicente, turbulent flow velocities preclude vertical particle transfer against the flow of liquid, and favour fractionation by rapid crystal growth in a boundary layer close to the dyke margins, and particle accretion to the dyke walls. The Vale de Cavaleiros sovite on Fogo, displays mineralogical variation as a result of adcumulation, gravitationally controlled sedimentalogical sorting and post-lithification deformation. Minor and trace element variations are explained partly as a function of the heterogeneity of mineralogy, but require chemical modification of the magma by fractional crystallization and auto-metasomatizm. O18o and O13C of the carbonatites on San Vicente are decoupled, however calcite and dolomite may have equilibrated with seawater at temperatures close to 100°C. Fractionation of calcite and apatite from a carbonatite magma, produces cumulate microsovite and conjugate evolved carbonatite liquids which form the ferrocarbonatite suite. Trace element variations within the ferrocarbonatite suite indicate that the unstained ferrocarbonatites (unaltered 'quench' carbonatite) are heterogeneously metasomatized and mineralized by evolved (contaminated) orange ferrocarbonatites to produce brown-black ferrocarbonatites. The degree of dolomitization of the Camile dyke on San Vicente, relates to the activity of Ba2+ released during recrystallization of the original carbonate minerals. The arrays on plots of 87Sr/86Sr vs 143Nd/144Nd vs. 206Pb/204Pb for rocks from the Cape Verde Islands are interpreted as a two component mixing lines between recycled pelagic sediment and recycled altered MORB. The melilitites and nephelinites of the Malhada Pedra formation on Maio defines an array from CSn = 157. to CSN = 07 (in CSn-(Or+Ab) n-Din space), which may be interpreted as describing the loci of migration of the peritectic melt during the melting episode. There is little evidence for the genesis of carbonatite by ultra - fractionation of carbonated, alkalic, silicate magma. Neither major or trace element evidence can discriminate between liquid immiscibility, or direct partial melting of carbonated peridotite at pressures greater than 20kbar as mechanisms for generating carbonatite magmas.

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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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Frejd, Julia. "Magnetic Mineralogy of Nb-bearing Carbonatites from Oldoinyo Dili (Tanzania)." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445837.

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Niobium (Nb) and Rare Earth Elements (REE’s) have in recent years received considerable attention because of their importance to the modern technical industry, and more specifically the enhanced sustainability that comes with them. The main source for Nb and REE’s on Earth are carbonatites and associated alkaline silicate rocks. This report examines the magnetic properties of rocks from the Oldoinyo Dili carbonatite complex in northern Tanzania. Previous workers have suggested a link between the Fe-bearing mineralogy and the formation of Nb-mineralizations at Oldoinyo Dili. This hypothesis is further examined in this report by combining detailed petrographic observations and withnew measurements of magnetic susceptibility. The aim is to see if any correlation exists between occurrence of Nb-mineralizations and the types of Fe-minerals present at Oldoinyo Dili. Based on the magnetic susceptibility measurements, at least two different species of Fe-minerals arefound in the examined samples. These are characterized by different magnetic trends during heating/cooling and also by their separate Curie temperatures (Tc). In combination with the petrographic observations these minerals are interpreted to be magnetite (Fe2O4) with Tc ~580°C, and a mineral that most likely represents a solid solution between ilmenite (FeTiO3) and hematite (Fe2O3) with Tc ~300°C. Here, no clear link between the type of opaque mineral(s) present and the total Nb content of the carbonatites can be conclusively determined based on the petrography and the magnetic measurements alone. Although the results of this report provide an important first step towards understanding the relationship between Nb-mineralizations and the magnetic mineralogy at Oldoinyo Dili, more detailed analyses of the mineral chemistry is a necessity to fully understand their complex relations and the specific conditions under which they formed.
Niob (Nb) och sällsynta jordartsmetaller (REE’s) har på senare år fått stor uppmärksamhet för sin betydelse för den moderna tekniska industrin, och specifikt för den förhöjda hållbarhet som de bidrar med. Den huvudsakliga källan till Nb och REE’s på jorden är karbonatiter och associerade alkalisilikater. Denna rapport undersöker de magnetiska egenskaperna för karbonatit-komplexet Oldoinyo Dili i norra Tanzania. Forskare har tidigare anat att det finns en koppling mellan Fe-bärande mineralogi och bildandet av Nb-mineraliseringar vid Oldoinyo Dili. Denna hypotes undersöks vidare i denna rapport genom att kombinera detaljerade petrografiska observationer med nya mätningar av magnetisk susceptibilitet. Syftet är att undersöka om det finns någon korrelation mellan förekomst av Nb-mineraliseringar och de typer av järnmineral som finns vid Oldoinyo Dili. Baserat på de genomförda magnetiska susceptibilitets-mätningarna så finns det åtminstone två olika sorters järnmineral i de undersökta proverna. De karaktäriseras av olika magnetiska trender vid upphettning/nedkylning och även av sina olika Curietemperaturer (Tc). Kombinerat med petrografiska observationer uttolkas att dessa mineral är magnetit (Fe2O4) med Tc ~580°C, samt en mineral som troligen är en solid solution av ilmenit (FeTiO3) och hematit (Fe2O3) med Tc ~300°C. Det går inte att senågon tydlig koppling mellan förekommande opaka mineral och det totala Nb-innehållet i karbonatiterna med säkerhet enbart utifrån petrografin och de genomförda magnetiska mätningarna. Resultaten av denna rapport utgör ett bra första steg mot att förstå relationen mellan Nb-mineraliseringar och den magnetiska mineralogin för Oldoinyo Dili, men mer detaljerade analyser av mineralkemin är nödvändigt för att till fullo förstå de komplexa förhållanden som råder vid bildning av dessa.

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Lee, Mi Jung. "Minéralogie, pétrologie et géochimie de l'association Phoscorite-Carbonatite du complexe alcalin de Sokli, Finlande." Saint-Etienne, EMSE, 2002. http://www.theses.fr/2002EMSE0020.

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Le complexe de Sokli, situé en Laponie finlandaise (67°48'N, 29°27'E), fait partie de la Province Alcaline de Kola, qui comporte 24 intrusions alcalines, mises en place au Dévonien, entre 370 et 340 Ma. Le complexe comprend principalement deux zones. La zone externe est constituée de roches modifiées ('métacarbonatites' et 'métaphoscorites', au sens de Verwoerd, 1967). La zone centrale est constituée pour l'essentiel de carbonatites associées à des phoscorites. Sur la base des assemblages minéraux et de la géochimie, trois paires principales ont été reconnues, C1-P1, C2-P2, C3-P3, qui se distribuent dans des zones successivement de plus en plus centrales du 'complex carbonatite-phoscorite' (CCP). A ces paires carbonatite-phoscorite succèdent des carbonatites à dolomite dominante (stade D4), puis un stade terminal, D5, de carbonatites à dolomite minéralisé en Strontium, Baryum et Terres Rares. Les minéraux de métaux rares (Zr, Nb, Ta,. . . ), préférentiellement concentrés dans les faciès phoscoritiques, passent de Baddeleyite seule dans CP1, à Baddeleyite+Pyrochlore dans CP2, puis à Pyrochlore dominant, et localement très abondant (quelques %), dans CP3
The Sokli complex (67°57'N, 29°05'E) is located in the north-eastern Finih Lapland, and belongs to the Paleozoic (380-360 Ma) Kola Alkaline Province (KAP). The complex comprises two main units organized as concentric zones. The outer zone is composed of alkaline silicate rocks intruded by numerous veins of carbonatites and largely transformed by the related fluids ; the inner zone is dominantly composed of carbonatites and subordinate phoscorites. Based on mineral assemblages, mineral compositions, and bulk chemical compositions, the Sokli phoscorites and carbonatites are classified in five stages of intrusion. In the early stages, phoscorites and calcite carbonatites are intimately associated with each other (P1-C1, P2-C2 and P3-C3 phoscorite-carbonatite pairs) ; in the later stages, the intrusive material is mostly dolomitic (D4 and D5 dolomite carbonatites) and lacks associated phoscorite. The latest stage rocks occur along a fracture zone in the centre of the 'magmatic core'

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Baghdadi, Bashar. "Géochimie analytique et prospection : application aux roches mantelliques de type péridotitique." Paris 6, 2013. http://www.theses.fr/2013PA066235.

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Les angrites forment un groupe d’achondrites rares dont la minéralogie est particulière. Ce sont les plus anciennes roches magmatiques du système solaire (~4. 564 Ga). Leur pétrogenèse est mal comprise, leur pétrographie inhabituelle place leur origine au cœur d’un grand débat. La présence de métal et des microstructures réactionnelles dans certains échantillons de ce groupe mérite d’être étudiée attentivement ce qui n’a pas été fait jusqu’à ici. La modélisation thermodynamique permettra de préciser les conditions de leur formation. Nous avons conduit des analyses pétrogéochimiques et minéralogiques sur des échantillons d’angrites de type péridotitique et sur des roches terrestres (enclaves carbonatées) de Tell Thennoun/Syrie. Les résultats nous ont permis de contraindre les conditions P-T nécessaires à l’existence du magmatisme parent des angrites et de vérifier dans quelle mesure les données sur les péridotites terrestres sont en accord avec ces résultats. La maîtrise des analyses géochimiques et leurs applications dans le domaine de la prospection des minéraux est un des objectifs de cette thèse, l’étude des roches carbonatées de Tell Thennoun en est un exemple. On en conclut que le corps parent des angrites est un planétoïde de grande taille avec une évolution métamorphique et dont le magmatisme associé est typique de l’évolution précoce des planètes. Quant aux roches carbonatées de Tell Thennoun, il semble qu’elles représentent des roches d’origine sédimentaire plutôt que magmatique, recyclées dans le volcanisme de rift syrien et dont l’intérêt économique est très faible
Angrites are a group of rare achondrites with particular mineralogy. They are the oldest igneous rocks in the solar system (~4. 564 Ga). Their petrogenesis is poorly understood, their unusual petrography put up their origin in the heart of a great debate. The presence of metal and reaction microstructures in some samples of this group deserve to be studied carefully what has not been done yet. The thermodynamic modeling would recognize the conditions of their formation. We carried out petrogeochemical and mineralogical analysis on some angrites of the peridotitic type and on some terrestrial rocks (carbonated enclaves) of Tell Thennoun/Syria. The results allow us to constrain the P-T conditions necessary for the existence of the parental magmatism of angrites and to verify the extent to which data on terrestrial peridotites are consistent with these results. The expertise of geochemical analysis and their applications to the field of mineral exploration is one of the objectives of this thesis, the study of carbonated rocks of Tell Thennoun is an example of the latter. We conclude that the angrites parent body is a large planetoid with a metamorphic evolution and the associated magmatism is typical of early evolution of planets. About the carbonated rocks of Tell Thennoun, it seems that they represent rocks of sedimentary origin, rather than magmatic ones, which have been recycled in the Syrian rift volcanism and show a low economic interest

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Onuonga, Isaac Oriechi. "Geochemistry and mineralization of Buru and Kuge volcanic carbonatite centres, Western Kenya." Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/15470.

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Western Kenya hosts a number of Tertiary and Quaternary alkaline volcanic carbonatite centres, such as Rangwa, the North and South Ruri centres, Kuge, Homa Mountain and Legetet which are located along an old Precambrian major shear zone lying within the Nyanza rift, off the main Kenyan (Gregory) rift. The centres consist of agglomerates and breccias with mixed clasts of silicate rocks and carbonatites, interbedded with carbonatitic and nephelinitic tuffs. The volcanic assemblage is transected by high level sheets and dykes of calcite carbonatite and ferrocarbonatite which were probably later feeders for the volcanic eruptions. Carbon, oxygen, and sulphur isotopic compositions were determined for calcite, siderite and barite from the Buru and Kuge carbonatite centres. Wide ranges in the isotopic compositions of the minerals were observed with values for delta13C and delta18O for the Buru calcites ranging from +1.27 to -3.23‰ (PDB) and +11.25 to +26.21‰ (SMOW). The delta13 C and delta18O for the Kuge calcites are -3.11 to -8.44‰ (PDB) and +18.09 to +25.73‰ (SMOW). The Buru siderites plot in a narrow and restricted range at -3.07 to -4.39‰ (PDB) and +12.61 to +16.10‰ (SMOW). Data on the sulphur isotopic composition from the Buru hill carbonatite show a fairly widespread variation in delta34S ranging from +4.50 to +12.40‰ (CDT), whereas Kuge hill displays a slightly more homogenous isotopic composition with values ranging from +1.10 to +5.10‰ (CDT). The carbon and oxygen isotopic compositions from the Buru and Kuge carbonatite centres do not retain the primary isotopic signatures expected for magmatic primary carbonatites. Most of the variations in isotopic composition have been attributed to secondary processes involving low temperature (60° to 144°C) hydrothemal alteration and isotopic exchange between the carbonatites and fluids (meteoric water). Higher delta18O values (+21.91 to +26.21‰) with a significant increase in delta13Cvalues (-1.48 to +1.27‰) shown by the most oxidized samples from the Buru carbonatite may indicate the involvement of supergene exchange with atmospheric CO2 at relatively lower temperatures (< 50°C). The variations in 34S shown by the two centres compared to mantle sulphur could be due to either redox processes and/or isotopic fractionations due to loss of volatiles. The Buru and Kuge carbonatite centres are characterized by enriched rare earth element (REE) values dominated by higher abundances of LREEs with steep chondrite-normalized distribution patterns. The lateritic zone at Buru hill, however, contains the greatest concentrations of REEs, barium, iron and manganese compared to the fresh carbonatite in which calcite and particularly siderite increase in abundance as the influence of supergene processes decrease with depth. The most common rare earth minerals encountered in the Buru and Kuge carbonatite centres are the fluorocarbonates (bastnaesite, synchysite and parisite), and monazite. The lanthanide fluorocarbonate and monazite control the concentration and bulk distribution of the REEs. The replacement textures of the lanthanide fluorocarbonates and monazite indicate that they are secondary in origin and appear to have been introduced by late stage, low temperature hydrothermal processes. The rare earth minerals are commonly accompanied by fluorite, and barite. Stable isotope studies suggest that the low temperature mineralogical changes and REE mineralization observed in western Kenyan carbonatites were controlled initially by hydrothermal activity and later by supergene processes. Higher delta18O and values, especially in the oxidized zones, correspond to higher REE abundances.

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10

Bizzarro, Martin. "Major element and isotope geochemistry (Sr, Nd and Hf) of mantle derived peridotites, carbonatites and kimberlites from Canada and Greeland; insights into mantle dynamics." Thèse, Chicoutimi : Montréal : Université du Québec à Chicoutimi ; Université du Québec à Montréal, 2003. http://theses.uqac.ca.

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Thèse (D.Ress.Min.) -- Université du Québec à Chicoutimi, programme extensionné à l'Université du Québec à Montréal, 2002.
Bibliogr.: f. 105-109. Document électronique également accessible en format PDF. CaQCU

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11

Sage, R. P. "Alkali rock complexes - carbonatites of Northern Ontario and their economic potential." Ottawa, 1986.

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12

Alves, Paula Regina. "The carbonatite-hosted apatite deposit of Jacupiranga, SE Brazil: styles of mineralization, ore characterization and association with mineral processing." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/prayb4_09007dcc804f7bd9.pdf.

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Thesis (M.S.)--Missouri University of Science and Technology, 2008.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 9, 2008) Includes bibliographical references (p. 131-139).

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Prud'homme, Nathalie. "Caractérisation pétrographique et géochimique de la carbonatite et de la syénite de la mine Lac Shortt /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1990. http://theses.uqac.ca.

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Mémoire (M.Sc.T.)--Université du Québec à Chicoutimi, 1990.
"Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en sciences de la terre" CaQCU Document électronique également accessible en format PDF. CaQCU

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14

Casola, Valentin. "Manteau source et genèse des magmas parents des carbonatites : les principales ressources en terres rares sur Terre." Electronic Thesis or Diss., Université de Lorraine, 2021. http://docnum.univ-lorraine.fr/public/DDOC_T_2021_0198_CASOLA.pdf.

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Les Terres Rares (REE) sont utilisés dans de nombreux produits industrialisés. Les principales sources de REE sont les laves et intrusions carbonatitiques. Les carbonatites sont des laves rares, riches en carbonates, dont les modèles pétrogénétiques font débat: soit une formation directe par la fusion partielle d'un manteau enrichi en carbone, soit par différenciation extrême puis immiscibilité à partir d'un magma silicaté alcalin. Ce projet se base sur une étude pétro-géochimique des xénolithes mantelliques recueillis autour de l'Oldoinyo Lengai (OL; Tanzanie), le seul volcan actif émettant des carbonatites, pour mieux contraindre la genèse des magmas carbonatitiques et alcalins associés. Grâce à une approche multi-minérale intégrant l'ensemble des données chimiques de toutes les phases minérales des xénolithes, cette étude montre que le manteau lithosphérique Tanzanien est hétérogène avec une histoire métasomatique complexe. Par ailleurs, certains xénolithes contiennent des carbonates similaires à ceux observés précédemment dans le manteau de la région. Les compositions des carbonates de cette étude et de deux échantillons de la littérature réanalysés ici documentent des δ18O et δ13C qui soutiennent la formation pédogénique de ces carbonates et réfutent donc un enrichissement global en carbone, sous forme de carbonates mantelliques, du manteau lithosphérique N-Tanzanien. Ces résultats soutiennent une formation des carbonatites de la région par une différenciation extrême de magmas alcalins produits par la fusion partielle d'un manteau lithosphérique relativement pauvre en carbone. Par ailleurs, les magmas silicatés alcalins (mélilitite, Mg-néphélinite) sont considérés comme les potentiels magmas parents des carbonatites actuellement produites par l'OL. Les études sur ces magmas ont montré qu'ils peuvent être générés par la fusion de lithologies métasomatiques pyroxénitiques porteuses de phases riches en éléments volatils (CO2, H2O). Ainsi, la fusion d'une veine métasomatique naturelle provenant de nos échantillons forme les magmas alcalins silicatés les plus riches en CO2 et H2O expérimentalement produits depuis un protolithe naturel. La fusion des veines de pyroxénites à phlogopites forme donc des magmas dont les compositions suggèrent leur implication dans la genèse des magmas primitifs de la région. Ces résultats suggèrent que la fusion partielle des veines fertiles d'un manteau métasomatisé participe à la formation des magmas parents des carbonatites
Rare Earth Elements (REE) are used in numerous industrialized products. The main sources of REE are carbonatite lavas and intrusions. Carbonatites are rare, carbonate-rich lavas, whose origin remains underconstrained: either directly derived from the melting of a C-rich mantle, or formed by protracted differentiation and immiscibility from silicate magmas. This project is focused on the petro-geochemical study of mantle xenoliths gathered around the Oldoinyo Lengai (OL; Tanzania), the only active volcano emitting carbonatites on Earth. Thanks to a multi-mineral approach integrating chemical data of all the mineral phases present in mantle xenoliths, this study shows that the Tanzanian lithospheric mantle is heterogeneous, with a complex metasomatic history. In addition, some xenoliths contain carbonates similar to those previously observed in the lithospheric mantle from the area. The isotopic compositions of carbonates from this study and of two samples from the literature reanalyzed herein display δ18O and δ13C isotopic compositions that support the pedogenic formation of these carbonates. This refutes an overall carbon enrichment, in the form of mantle carbonates, of the lithospheric mantle under the only active volcano emitting carbonatites. These results support the formation of Tanzanian carbonatites by extreme differentiation from alkaline magmas produced by the partial melting of a relatively C-poor mantle. In addition, alkaline silicate magmas (melilitite, Mg-nephelinite) are considered to be the potential parental magmas of carbonatites currently produced by the OL. Previous studies on these magmas have shown that they can potentially be generated by the partial melting of pyroxenite metasomatic lithologies carrying volatile-rich phases (CO2, H2O). Hence, the melting of a natural metasomatic vein from our sample set forms the most volatile-rich silicate alkaline magmas experimentally produced from a natural protolith. The melting of metasomatic phlogopite-rich pyroxenites veins produces magmas which compositions strongly suggest their involvement in the genesis of the primitive magmas of the area. Thus, these results suggest that the partial melting of the fertile veins of a metasomatized mantle participates in the formation of the parental magmas of carbonatites

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

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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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16

Ngwenya, Bryne Tendelo. "Magmatic and post-magmatic geochemistry of phosphorus and rare earth elements in carbonatites." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306803.

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This study documents the magmatic, hydrothermal and supergene mineralogy and geochemistry of phosphorus and rare earth elements in carbonatite complexes using examples from Tundulu (Malawi), Sokli (Finland), Siilinjarvi (Finland) and Kaluwe (Zambia). In carbonatites, phosphorus averages 1-2% P20S and forms the minerals fluorapatite and monazite. Hydrothermal and supergene processes enrich fluorapatite in Na and REEs through vitusite-type exchanges which lead to formation of vitusite, belovite and britholite; and in CO2 through anti-francolite substitutions. The highest rare earth element contents are found in late-stage ankerite carbonatites or similar rocks of low temperature origin (T < S(XtC) and in hydrothermally altered rocks, where they occur mainly as fluorocarbonates or carbonates. Such minerals are consistent with the REEs having been transported in form of mixed fluoride-carbonate complexes. The mineral paragenesis in hydrothermal veins suggests that different fluorocarbonates precipitated depending on the activity of Ca supplied to the fluid by the wall rocks. The various minerals are modelled to form by simple combinations of calcite (CaCO:v and bastnaesite (REEC03F) molecules. A secondary characteristic feature of these reactions is that extreme heavy rare earth enrichment occurs if the wall rocks are apatite-rich. Petrogenetic modelling using REEs suggests that carbonatites are unlikely to be derived from carbonated silicate magmas by fractional crystallisation or liquid immiscibility. These findings are supported by ex solution temperatures of about 9S0·C recorded using the calcitedolomite geothermometer for quenched lapilli from the Kaluwe carbonatite.

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Burger, Erasmus Petrus. "An Investigation of the carbonatites of the Kaapvaal Craton and their tectonic context." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/43297.

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Carbonatites are exotic rocks which usually occur in discrete intrusions. Considering the association of carbonatites with rifting environments, this dissertation proposes that: carbonatites occur in extensional tectonic settings and therefore carbonatite occurrence can be used to constrain an extensional setting for related occurrences. In order to give context in which to consider this hypothesis, the formation of carbonatites is reviewed. This work favours the direct mantle melting model as it is most relevant and consistent with observations of Kaapvaal Craton carbonatites. However the liquid immiscibility model cannot be entirely rejected with current knowledge. The hypothesis is applied to the Bushveld Igneous Complex after providing evidence of the rift-carbonatite association. The Bushveld Igneous Complex is considered to have been emplaced in the same tectonic setting as carbonatites. Therefore the Bushveld Igneous Complex was emplaced in an extensional tectonic setting. Finally the carbonatites which are part of the Pilanesberg Alkaline Province are considered in order to test the hypothesis. This work finds that the Pilanesberg carbonatites do occur with other rift related magmatism during the break-up of Nuna (Columbia) and therefore the hypothesis is not rejected. This work offers reviews of basic carbonatite background, formation models and carbonatite occurrences on the Kaapvaal Craton.
Dissertation (MSc)--University of Pretoria, 2013.
lk2014
Geology
MSc
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Bédard, L. Paul. "Pétrographie et géochimie du stock de Dolodau : syénite et carbonatite associée /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1988. http://theses.uqac.ca.

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Nabyl, Zineb. "Caractérisation expérimentale du comportement des métaux rares au cours de la différenciation des carbonatites et des magmas alcalins." Thesis, Orléans, 2020. http://www.theses.fr/2020ORLE3048.

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Les carbonatites et les roches magmatiques alcalines constituent une faible fraction du magmatisme terrestre et sont essentiellement produits en contexte intraplaque. Ces magmas sont particulièrement riches en éléments volatils (dioxyde de carbone, halogènes et eau) et présentent aussi des fortes concentrations en métaux rares (REE, Hf, Zr, Nb, Ta). Les gisements associés à ces roches magmatiques sont souvent affectés par des stades hydrothermaux tardifs brouillant les relations entre les processus magmatiques à l’origine de la formation de ces magmas (immiscibilité, différenciation, cristallisation fractionnée) et cet enrichissement métaux et en constituants volatils. Des expériences haute pression et haute température ont été réalisées afin d’évaluer le comportement des métaux rares pendant la différenciation de ces magmas. Ces expériences adressent le comportement des métaux rares pendant les processus d’immiscibilité entre liquides silicatés et liquides carbonatés et pendant la cristallisation de ces magmas. Les conditions optimales d’enrichissement en REE des liquides carbonatés au cours de la différenciation des magmas alcalins sont identifiées : les liquides carbonatés les plus enrichis sont formés par immiscibilité avec des liquides silicatés très différenciés et polymérisés de type phonolite/phono-trachyte. Un modèle d’enrichissement en REE des liquides carbonatés basé sur la composition des liquides silicatés est proposé et permet d’identifier i) le potentiel en REE des carbonatites pouvant être formées par immiscibilité avec des magmas alcalins, et ii) le stade de genèse par immiscibilité des carbonatites tout au long de la différenciation alcaline. De plus, le degré de différenciation et de polymérisation des liquides silicatés joue également un rôle sur l’enrichissement en métaux rares des cristaux (clinopyroxène, grenat, titanite, calcite et apatite) : les métaux rares sont plus concentrés dans les minéraux coexistant avec des liquides silicatés plus différenciés et polymérisés. Ceci implique que les liquides silicatés alcalins tendent à s’appauvrir en REE au cours de la différenciation, en comparaison aux liquides carbonatés et aux cristaux
Carbonatites and alkaline magmatic rocks occur in intraplate context and constitute a small fraction of the earth magmatism. Those magmas are particularly enriched in volatiles (carbon dioxide, halogens, water) and also in rare metals (REE, Hf, Zr, Ta, Nb). The associated deposits are often affected by hydrothermal and supergen processes which erase any relation to the magmatic processes at the origin of these magmas (immiscibility, differentiation, fractional crystallization) and responsible of the rare metal and volatile enrichments.High pressure and high temperature experiments have been performed to characterize the behavior of rare metals during both magma differentiation. These experiments simulate the immiscibility between carbonate and alkaline silica-undersaturated melts, during the crystallization of the magma.The optimum of carbonate melt REE enrichments across alkaline magma differentiation course is identified : carbonate melts immiscible with highly differentiated and polymerised silicate melts of phonolitic/phono-trachytic compositions are the REE richest. A modelling of carbonate melts REE enrichment based on the silicate melt composition is suggested, to identify the REE potential of carbonatites which may be immiscible with an alkaline magmatic rock, or to identify at which differentiation stage the immiscibility has occurred. Moreover, the silicate melt degree of differentiation and polymerisation has also an impact on crystal rare metal enrichments : crystals which coexist with highly differentiated and polymerized silicate melts are highly enriched in rare metals. This implies that silicate melts become depleted in REE across the differentiation compare to crystals and carbonate melts

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Martin, Alexis. "Modélisation de saumures carbonatées et caractérisation hydrogéologique de la mine Niobec, Saint-Honore, Québec : /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1993. http://theses.uqac.ca.

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Andrade, Marcelo Barbosa de. "Estudo cristaloquímico de minerais do grupo do pirocloro no Brasil." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/44/44135/tde-30072007-165039/.

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Os minerais do grupo do pirocloro (A2B2X6Y1) apresentam grande interesse econômico, principalmente como fonte de nióbio e tântalo, metais que possuem importantes aplicações tecnológicas como a fabricação de aço e a confecção de componentes eletrônicos. Apesar de seu interesse científico e econômico, a maioria das ocorrências brasileiras de minerais do grupo do pirocloro está apenas parcialmente caracterizada ou não dispõe de nenhum estudo mineralógico. Adicionalmente, o atual sistema de classificação dos minerais do grupo do pirocloro, apesar de aprovado pela IMA, não segue as regras gerais de nomenclatura de minerais da própria IMA. Na posição A, não há diferenciação na ocupação por Ca e por Na, e se um ou mais cátions diferentes de Na ou Ca compuserem mais de 20 % total de átomos na posição A, então a espécie é nomeada pelo átomo mais abundante em A (exceto Na e Ca). Por outro lado, a espécie fluornatromicrolita foi aprovada com base na predominância de Na na posição A. Com relação à ocupação da posição B, a divisão entre os grupos não é feita com uma classificação tripartite: as espécies com Nb + Ta >2Ti e Nb > Ta são consideradas como do subgrupo do pirocloro; se Nb + Ta > 2Ti e Ta ≥ Nb, o mineral irá pertencer ao subgrupo da microlita; e se 2Ti ≥ Nb + Ta, o mineral irá pertencer ao subgrupo da betafita. Espécies isoestruturais com outros cátions predominantes na posição B não são incluídas no grupo do pirocloro (por exemplo, romeíta com Sb dominante). Os ânions não são levados em consideração na classificação, mas o flúor foi usado na aprovação da espécie fluornatromicrolita. Neste trabalho, são apresentados novos esquemas de nomenclatura para os minerais do grupo do pirocloro, que levam em consideração os íons ocupantes das posições A, B e Y. Os prefixos são sempre escritos por extenso (\'hidroxi\', \'fluor\', \'calcio\', \'natro\' etc), enquanto os sufixos são representados por símbolos químicos (Na, F, H2O etc) ou por [] (vazio). Os nomes raízes relacionam-se aos cátions predominantes na posição B, levando a termos como pirocloro, microlita, betafita e romeíta. São apresentados novos dados químicos por MEV-EDS e WDS (incluindo análises de Si, normalmente negligenciado na maioria dos dados da literatura). Foram analisados minerais de seis ocorrências em pegmatitos e uma em carbonatito. Os resultados obtidos permitem separar as espécies em três \'famílias\'. A primeira delas poderia ser denominada \'microlita\', envolvendo fluornatromicrolita, fluorcalciomicrolita, oxinatromicrolita e oxicalciomicrolita. Esta família foi identificada nas ocorrências da lavra do Morro Redondo, Coronel Murta, MG; lavra do Jonas, Conselheiro Pena, MG; mina Quixabá, Frei Martinho, PB; Pegmatito Volta Grande, Nazareno, MG; lavra do Ipê, Marilac, MG; e Pegmatito Ponte da Raiz, Santa Maria de Itabira, MG. A primeira das espécies, fluornatromicrolita, parece ser bem mais comum do que se imaginava, tendo sido descrita previamente no Brasil apenas em Quixabá, e agora verificada em diversas das ocorrências estudadas nesta tese. Apesar de usados os prefixos natro e cálcio, todas as amostras parecem tender para um termo de fórmula final (NaCa)Ta2O6F, ou seja, com Na=Ca em apfu, que poderia ser denominado, por exemplo, fluormicrolita-NaCa ou CaNa. O oxigênio é, algumas vezes, superior ao flúor (em apfu) na cavidade Y, dando origem a espécie oxi-. A segunda família poderia ser denominada \'hidromicrolita\', tendendo a [ [](H2O)]Ta2O6(H2O). Esta fórmula, entretanto, não é eletricamente neutra, necessitando que na cavidade A, (H2O) seja parcialmente substituído por cátions (Ba, U etc), ao mesmo tempo que parte do O da posição X seja substituído por (OH). Minerais desta família foram verificados no Pegmatito Volta Grande, Nazareno, MG. A terceira família, do \'pirocloro\', verificada apenas no carbonatito da mina Jacupiranga, Cajati, SP, inclui as espécies fluorcalciopirocloro e oxicalciopirocloro. Os novos nomes sugeridos parecem discriminar melhor as espécies, com base em cátions, vazios ou H2O predominantes nas posições A, B eY, permitindo inclusive uni-las em \'famílias\'. Esta nova nomenclatura apresenta também como vantagem não dar ênfase a componentes menores da cavidade A, bem como verificar nela a predominância de Ca ou Na. Adicionalmente, os cátions Ta, Nb e Ti passam a ter a mesma importância na cavidade B. Por outro lado são criados nomes \'exóticos\', como hidrohidromicrolita, ou \'impronunciáveis\', como hidro-[]-microlita.
Pyrochlore group minerals are important sources of niobium and tantalum and these metals are used in important technological applications such as steel manufacturing and eletronic components development. However, the majority of Brazilian occurrences are only partially characterized or there is no mineralogic study available. In addition, the official pyrochlore-group minerals classification system does not follow the IMA mineralogical nomenclature rules although this system is approved by IMA. In the A site, it does not differentiate between occupation by Ca and Na, and if there is one or more cation other than Na or Ca composing more than 20% of total A-atoms, then the species must be named according to the most abundant A-atom, other than Na or Ca. In spite of this, the species fluornatromicrolite was approved based on the predominance of Na in the A-site. Regarding the B-site occupation, the division among the subgroups is not made with a tripartite symmetrical classification: the species with Nb + Ta >2Ti and Nb > Ta are considered as pyrochlore subgroup minerals; if Nb + Ta > 2Ti and Ta ≥ Nb, the mineral will belong to the microlite subgroup; and if 2Ti ≥ Nb + Ta, the mineral will belong to the betafite subgroup. Isostructural species with other predominant cations in the B-site are not included in the pyrochlore-group (for example, romeite, with dominant Sb). The anions are not taken into account in the classification but the predominance of fluorine was used for the approval of the species fluornatromicrolite. In this present work new nomenclature schemes, based on the ions in A, B and Y sites, are presented. Prefixes are, for example, \'hidroxi\', \'fluor\', \'calcio\', \'natro\' etc., while sufixes are represented by chemical symbols (Na, F, H2O etc) or [] (vacancies). The root names (pyrochlore, microlite, betafite, romeite) are related to the dominant-constituent cations in the B position. New chemical data by MEV-EDS and WDS (including Si analysis, hardly ever mentioned in litetarature) were obtained. Six occurrences from pegmatites and one from carbonatite were analysed. The results allow the species to be grouped in three \'families\'. The first could be named as \'microlite\', and includies fluornatromicrolite, fluorcalciomicrolite, oxinatromicrolite and oxicalciomicrolite. This family was identified in Morro Redondo quarry, Coronel Murta, MG; Jonas quarry, Conselheiro Pena, MG; Quixabá mine, Frei Martinho, PB; Volta Grande pegmatite, Nazareno, MG; Ipê quarry, Marilac, MG and Ponte da Raiz pegmatite, Santa Maria de Itabira, MG. Fluornatromicrolite seems to be more common than was previously thought. It was previously described only in Quixabá but now many other occurrences are known. Although \'natro\' and \'calcio\' prefixes were used, all the formulae seem to approach the term (NaCa)Ta2O6F. As Na approximately equals Ca (apfu) it could be used the name fluornatromicrolite-Na-Ca or CaNa could be used. The oxigen content is sometimes greater than F content in the Y position. This generates the oxi- species. The second family could be named \'hidromicrolite\', becoming [ [] (H2O)]Ta2O6(H2O). This formulae is not eletrically neutral so the H2O is replaced by cations (Ba, U etc) in the A cavity while the O is replaced by (OH) in the X position. Minerals from this family were identified in the Volta Grande pegmatite, Nazareno, MG. The third family, \'pyrochlore\', was only verified in the Jacupiranga mine, Cajati, SP, including fluorcalciopyrochlore and oxicalciopyrochlore species. The suggested new names, based on cations, vacancies or H2O dominant constituents of A, B and Y sites, seem to better describe the species, allowing their grouping in families. This new nomenclature has the advantage of not emphasize minor constituents in the A cavity, and verify the dominance of Ca or Na. Furthermore, Ta, Nb and Ti cations have the same balance in B cavity. On the other hand, exotic names were created such as hydrohydromicrolite or unpronounceable as hydro-[]-microlite.

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22

Ranta, Eemu. "Study of opaque phases in carbonatites of the Grønnedal-Íka alkaline complex, Southwest Greenland." Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-117831.

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Opaque phases from carbonatites of the Grønnedal-Íka alkaline complex (1299±17 Ma) of Southwest Greenland were analyzed in terms of their mineralogy and microstructure. The analysis demonstrates that a later intrusion by a 55 m wide dolerite dyke of unknown age has prompted the mineralization of magnetite by activating hydrothermal fluid convection. The fluid has interacted with the carbonatite, replacing siderite and ankerite by magnetite, which at places constitutes over half of the rock volume. Magnetite is shown to have become partly replaced by hematite at a later stage. A paragenetic sequence is suggested for the opaque phases that com- prise major magnetite and hematite, accessory pyrite and trace amounts of sphalerite, chalcopyrite and galena.
Low-temperature geologic sequestration of carbon by ikaite formation

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23

Do, Cabo Vistorina Nandigolo. "Geological, mineralogical and geochemical characterisation of the heavy rare earth-rich carbonatites at Lofdal, Namibia." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/15034.

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This study considered the geology, mineralogy, geochemistry, formation and evolution of the heavy rare earth element (HREE) mineralised Lofdal alkaline carbonatite complex (LACC), which is located on the Bergville and Lofdal farms northwest of Khorixas, in the Kunene Region of the Republic of Namibia. . Field methods used included mapping, ground and hyperspectral airborne geophysics, and sampling. Analytical techniques used were optical petrography and CL, XRF, ICP-AES, backscattered and secondary electron imaging, electron microprobe, LA-ICP-MS, leaching, as well as carbon and oxygen stable isotope determination. The LACC comprises a swarm of dykes, mainly calcite carbonatite but also dolomite and ankerite carbonatite dykes (classified into five types) and two newly discovered plugs of calcite carbonatite (‘Main’ and ‘Emanya’), with associated dykes and plugs of phonolites, syenites and rare mafic rocks. These all intrude into the Huab Metamorphic Complex basement rocks within a NE-SW shear zone over 30 km long. The main HREE host mineral is xenotime-(Y). It occurs in highly oxidised iron-rich calcite carbonatite dykes mantling and replacing zircon, associated with hematite, thorite and apatite, or associated with monazite-(Ce), synchysite-(Ce), and parisite-(Ce), replacing the fluorocarbonates; it also forms aggregates in ankerite carbonatite. Although xenotime-(Y) occurs throughout the paragenetic sequence, there is much evidence for hydrothermal fluid activity at Lofdal, altering the dykes, and taking xenotime-(Y) into brecciated carbonate veins in albitised country rock (fenite). Radiogenic (Sr, Nd-Sm, U-Pb) and C and O stable isotope studies confirm that the carbonatite, derived from an enriched mantle, is the source of the REE. Mineralisation was contemporaneous with carbonatite emplacement at 765 ±16 Ma. Magmatic fluids >300°C were diluted with cool meteoric fluids. Abundant fluorite and carbonate indicate roles for F- and CO32- in addition to Cl- in REE transport. These ligands form the most stable complexes with HREE and since xenotime is soluble in concentrated alkali halide solutions, they could have preferentially transported and then deposited xenotime. Many of the features of Lofdal are common to other REE-rich carbonatite complexes but the xenotime-(Y) abundance is so far unique. The high amount of fluid activity in shear zones around the dyke swarm and probably a higher proportion of HREE in the original magmas seem to be the main differentiating features.

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24

Morisset, Natalie Carleton University Dissertation Geology. "Stableisotope and radioisotope geochemistry of the Panda Hill carbonatite, Tanzania." Ottawa, 1992.

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25

Petibon, Caroline Marie. "The genesis of natrocarbonatites : constraints from experimental petrology and trace element partitioning /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0018/NQ54841.pdf.

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26

Dardon, Arnaud. "Caractérisation géochimique des rutiles éclogitiques et conséquences de la présence du rutile et de l'ilménite résiduels pour les liquides issus de la fusion partielle des MORB." Clermont-Ferrand 2, 2002. http://www.theses.fr/2002CLF22384.

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Les modalités de transfert de certains HFSE (Ti, Nb, Ta, Hf, Zr) et actinides (U, Th), entre les métabasaltes et les liquides issus de leur fusion partielle sont appréhendées à travers la stabilité et l'influence des minéraux titanifères (ilménite et rutile). Les techniques de la pétrologie expérimentale (piston-cylindre) et de l'analyse géochimique (microsonde électronique ; Ablation Laser ICP-MS) ont été utilisées conjointement. A partir de la composition des proportions modales des minéraux majeurs et du rutile de cinq éclogites (Massif Central français, Dora Maria, Dabie Mountains, Norvège), cette étude montre notamment que l'essentiel de Nb, Ta et une part significative de U de la roche totale est contenu dans le rutile. Hf et Zr sont majoritairement portés par le zircon. Les coefficients de partage mesurés expérimentalement dans différentes conditions P-T-fo2 entre ilménite/liquide et rutile/liquide montrent que Nb et Ta sont compatibles dans le rutile (25-210) et l'ilménite (1,5-4, composition "basaltique"). Hf et Zr ne sont compatibles que dans le rutile (<6). U est incompatible dans le rutile en conditions réductrices (0,1-0,2) mais faiblement compatible en conditions oxydantes (entre 1 et 10). U est très incompatible dans l'ilménite et les solutions solides hématite-ilménite obtenues à haute f02. L'ilménite et le rutile n'ont pas d'influence significative sur les REE, Sr et Th (D < 0,5). La composition chimique (donc la strucrure) des liquides, influence fortement la valeur du coefficient de partage rt/liqDNb, DTa mais aussi le rapport rt/liqDNb/DTa, qui varie entre 0,5 (liquide basaltique) et 0,7-1 (liquide rholithique-dacitique). Les liquides silicatés en équilibre avec des résidus de type éclogite à rutile sont caractérisés par des Nb/Ta superchondritiques et un fractionnement Th-U marqué. Les liquides en équilibre avec des résidus de type amphibolite à grenat sont caractérisés par des Nb/Ta subchondritiques et l'absence de fractionnement U-Th

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Mian, Ihsanullah. "The mineralogy and geochemistry of the carbonatites, syenites and fenites of North West Frontier Province, Pakistan." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/35068.

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Tertiary carbonatites occur along thrust planes at Loe Shilman in Kyber Agency and at Silai Patti in Malakand Agency, NW Pakistan. The Loe Shilman carbonatite sheet complex comprises an amphibole sovite which is intruded by a biotite sovite and an ankeritic dolomite carbonatite. These carbonatites have produced zoned fenites as a result of Na, K and Na+Mg+Fe fenitizing-fluids emanating from the amphibole sovite, biotite sovite and ankeritic dolomite carbonatite respectively. The fenites grading into unfenitized Palaeozoic thinly bedded slates and phyllites. The variation in the whole-rock and mineral chemistries of the fenites correlates with the distances from the carbonatite contact. These gradual variations in chemistry are attributed to the low permeability of the slates and phyllites. A path of fractionation from calcite-rich to dolomite-rich carbonatites can be distinguished, while the final-stages which return to the calcite-rich carbonate phase are recorded only in the carbonatite veins The Silai Patti carbonatite sheet complex comprises a biotite sovite which is intruded by an amphibole sovite. These sovites have induced K-and Na-fenitizations respectively in granite-gneisses, amphibolites, dolerites and quartzites. The chemical variations in the rocks and minerals of the fenites correspond with the degree of intensity of fenitization. The chemistry of amphiboles, micas and pyroxenes which are in equilibrium with the carbonatitic fenitizing fluids are typically magnesio-arfvedsonite, phlogopite and aegirine-augite respectively. It is proposed that the Na-rich carbonatite magmas are derived from the magma produced by liquid immiscibi1ity from phonolite, but the K-rich magma has evolved from the primitive Na-rich carbonatite magma by crystal fractionation.

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Chen, Chunfei, Yongsheng Liu, Stephen F. Foley, Mihai N. Ducea, Detao He, Zhaochu Hu, Wei Chen, and Keqing Zong. "Paleo-Asian oceanic slab under the North China craton revealed by carbonatites derived from subducted limestones." GEOLOGICAL SOC AMER, INC, 2016. http://hdl.handle.net/10150/622796.

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It is widely accepted that the lithospheric mantle under the North China craton (NCC) has undergone comprehensive refertilization due to input from surrounding subducted slabs. However, the possible contribution from the Paleo-Asian oceanic slab to the north is poorly constrained, largely because of the lack of convincing evidence for the existence of this slab under the NCC. We report here carbonatite intruding Neogene alkali basalts in the Hannuoba region, close to the northern margin of the NCC. Trace element patterns with positive Sr and U anomalies, negative high field strength elements (Nb, Ta, Zr, Hf, and Ti) and Ce anomalies, high Sr-87/Sr-86 ratios (0.70522-0.70796), and high delta O-18(SMOW) (standard mean ocean water) values (22.2%-23%) indicate that this carbonatite had a limestone precursor. However, the presence of coarse-grained mantle-derived clinopyroxene, orthopyroxene, and olivine, and chemical features of the carbonates suggest that the carbonate melts were derived from the mantle. The carbonates have high Nd-143/Nd-144 ratios (0.51282-0.51298) and show negative correlation between CaO and Ni contents, resulting from reaction between carbonate melt and peridotite. Considering the regional tectonic setting, the carbonatite probably formed by melting of subducted sedimentary carbonate rocks that formed part of the Paleo-Asian oceanic slab, and thus could provide the first direct evidence for the presence of the Paleo-Asian oceanic slab beneath the NCC.

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Baamrane, Najjaj Naima. "Etude minéralogique et géochimique du complexe carbonatitique d'Iron Hill, dans le Colorado et du massif alcalin de Rainy Creek dans le Montana (Etats Unis)." Paris 6, 1994. http://www.theses.fr/1994PA066722.

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Notre etude a porte sur deux massifs alcalins, d'ages differents, situes aux etats unis: le massif d'iron hill dans le colorado (570 ma) et le massif de rainy creek dans le montana (94 ma). Le massif d'iron hill est constitue de carbonatites intrusives et filoniennes associees a des pyroxenites, uncompahgrites, ijolites et syenites. L'etude mineralogique et geochimique de ce massif a montre une evolution des pyroxenites vers les syenites. La presence de deux types de carbonatites (magnesienne et calcique) implique sans doute qu'au cours de l'evolution du magma initial, il y a eu deux phases d'immiscibilite de liquides carbonates et de liquides silicates. Apres leur separation, les liquides carbonates ont evolue par cristallisation fractionnee comme le montre l'etude mineralogique des carbonates et des micas ainsi que l'etude geochimique des terres rares. Le massif de rainy creek comprend essentiellement des pyroxenites et des syenites auxquelles sont associes quelques filons riches en carbonates. L'etude mineralogique et geochimique de ce massif a montre une evolution des pyroxenes et des micas, marquee par une diminution du rapport mg/mg+fet, evolution similaire a celle observee dans le massif d'iron hill. L'etude isotopique du soufre effectuee sur les sulfures des carbonatites d'iron hill et des filons de quartz et carbonates de rainy creek, nous a permis de confirmer d'une part l'origine magmatique des carbonatites d'iron hill et d'autre part de presenter un argument tres fort en faveur d'une origine magmatique des filons a carbonates trouves dans le massif de rainy creek

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30

Farrell, Sean Bradley. "The sulphur isotope geochemistry of carbonatites and associated silicate rocks from the Superior Province of the Canadian Shield." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/26901.

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Thirty-five sulphur isotopic analyses have been obtained from six carbonatite-alkalic rock complexes ranging in age from 1906 Ma to 1008 Ma located within the Ontario portion of the Superior Province. Pyrrhotite, chalcopyrite and pyrite mineral separates were used. The overall range of delta 34SCDT values are from +3.4 to -4.5‰. Each complex shows its own distinct range and mean sulphur isotopic composition. The overall range in the sulphur isotopic composition in conjunction with carbon and oxygen isotopic data suggests that these carbonatites and associated silicate rocks were derived from a relatively primitive mantle source. This is consistent with previously published Sr and Nd isotopic data that suggest that the mantle source underlying the Superior Province has remained essentially a closed system from about 2700 Ma to at least 1008 Ma. The sulphur isotopic data reported here is the first ever for carbonatites from the Superior Province. (Abstract shortened by UMI.)

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Giebel, Robert Johannes [Verfasser], and Gregor [Akademischer Betreuer] Markl. "The petrogenesis of carbonatites : Mineral variations and effects on the REE mineralization / Robert Johannes Giebel ; Betreuer: Gregor Markl." Tübingen : Universitätsbibliothek Tübingen, 2019. http://d-nb.info/1198858842/34.

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Giebel, Johannes [Verfasser], and Gregor [Akademischer Betreuer] Markl. "The petrogenesis of carbonatites : Mineral variations and effects on the REE mineralization / Robert Johannes Giebel ; Betreuer: Gregor Markl." Tübingen : Universitätsbibliothek Tübingen, 2019. http://d-nb.info/1198858842/34.

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33

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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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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Mourtada, Saïd. "Pétrogenèse des carbonatites et contribution à l'étude des minéralisations (NB, Tr, Ba et Sr) associées : exemple du complexe alcalin de Tamazert (Haut-Atlas marocain)." Clermont-Ferrand 2, 1997. http://www.theses.fr/1997CLF21963.

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Le complexe alcalin de tamazert (haut-atlas, maroc) comporte plusieurs gisements a carbonatites. A l'exception des natrocarbonatites, tous les types actuellement connus dans le monde sont representes. Cette grande variete a permis de proposer une nouvelle classification. Quatre types sont definis : les ca-carbonatites (sovites, microsovites et alvikites), les mg-carbonatites intrusives (en filons et en amas) et extrusives (tuffisites beforsitiques), les fe-carbonatites (a ankerite et a fe-calcite) et les sr-carbonatites. La mise en place de la plupart d'entre elles a ete accompagnee d'une metasomatose potassique intense affectant surtout l'encaissant syenitique. Deux aspects de la geologie ont ete abordes dans cette these : petrologie : l'histoire petrogenetique de l'ensemble de ces carbonatites est relativement complexe, mettant en jeu des processus magmatiques (fusion partielle, cristallisation fractionnee, immiscibilite) et syn- a post-magmatiques (dolomitisation et metasomatose). Les ca-carbonatites proviendraient, par immiscibilite, d'un magma silicate de nature monchiquitique. Elles forment une suite complete, depuis les sovites jusqu'aux alvikites dont l'evolution temoigne d'une competition entre la cristallisation fractionnee et la metasomatose. Ce dernier mecanisme joue un role principal dans la genese des fe-carbonatites. Les mg-carbonatites extrusives, de par leur mineralogie a rutile et spinelle chromifere et leur composition chimique, seraient issues directement du manteau par fusion partielle. Les mg-carbonatites intrusives, quant a elle, seraient formees essentiellement par dolomitisation des sovities primaires. Les sr-carbonatites auraient precipite a partir des solutions carbo-hydrothermales enrichies en sr, ba et s, derivant du magma sovitique. Cette diversite d'origine va a l'encontre de l'hypothese classique, selon laquelle toutes les varietes carbonatitiques seraient issues d'un magma primitif unique. Metallogenie : l'alteration hydrothermale tardive, ayant affecte les ca-carbonatites dans le gisement de l'oued tamazert, s'est accompagnee de nombreuses mineralisations notamment de sr, ba et tr. Cette alteration se serait realisee sous de basses p (< 1kb) et t (< 425 c). Les fluides mineralisateurs impliques, auraient un ph acide et de fortes activites en tr, f, sr, si, mg et ba. Leur composition evoluerait aux depens de la composition de la roche hote par le biais de la dissolution des phases magmatiques primaires (apatite, pyrochlore et calcite). Au cours de l'evolution sovites alvikites, ces fluides auraient ete ainsi enrichis en plusieurs ligands comme f#-, po#4#3#-, so#2#-#4 et co#3#2#- responsables de la complexation des terres rares (tr).

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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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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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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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Ouzegane, Khadidja. "Les granulites al-mg et les carbonatites dans la serie de l'in ouzzal : nature et evolution de la croute continentale profonde pendant l'archeen." Paris 6, 1987. http://www.theses.fr/1987PA066566.

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Ouzegane, Khadidja. "Les Granulites Al-Mg et les carbonatites dans la série de l'In Ouzzal nature et évolution de la croûte continentale profonde pendant l'Archéen /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37608648z.

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Amsellem, Elsa. "Le fractionnement isotopique du Ca et du Sr à haute température : apport sur la formation et l’évolution de la Terre." Thesis, Université de Paris (2019-....), 2019. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=3979&f=25544.

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La formation du Système Solaire et son évolution restent peu connues aujourd’hui malgré le grand nombre de missions d’exploration spatiale mises en place depuis la deuxième moitié du 20ème siècle. Pour obtenir des informations sur les premières phases de la formation de la Terre et l’évolution du manteau terrestre, les météorites et les roches ignées sont de bons objets d’étude: les premières sont des témoins des conditions de la formation du Système Solaire et sont formées avant les planètes, les secondes nous renseignent sur la composition du manteau terrestre. Ces travaux de thèse se consacrent à l’analyse isotopique du calcium (Ca), du strontium (Sr) et du rubidium (Rb) d’une grande variété de roches terrestres et extra-terrestres en utilisant le MC-ICP- MS. Les isotopes stables du Ca et Sr permettent de tracer des processus physico-chimiques liés à la formation des roches. Le système Rb-Sr permet quant à lui de dater des évènements liés à l’histoire de ces roches. Les chondres, composants majoritaires des chondrites, ont été étudiés par analyse isotopique du Ca pour tes- ter et confirmer un modèle récent d’accrétion planétaire, le pebble accretion model. D’autres phénomènes peuvent affecter les corps qui peuplent notre système solaire. Notamment les chondrites peuvent subir des épisodes de chauffage et donc subir un métamorphisme thermique. La chronologie Rb-Sr permet de dater ces évènements de chauffage et d’en révéler l’origine qu’on estime alors liée à des impacts dans la ceinture d’astéroïdes. Les échantillons terrestres, des komatiites, MORBs et OIBs sont analysés pour estimer la composition isotopique du manteau en Ca et Sr ainsi que son évolution. La composition des isotopes stables du Sr dans le manteau semble homogène dans le temps alors que les isotopes du Ca révèlent la préservation d’hétérogénéités datant du début de l’histoire de la Terre. Les carbonatites, roches magmatiques contenant au moins 50% de minéraux carbonatés, sont étudiées en isotopie du Ca dans l’optique de révéler leur origine. L’enrichissement en isotopes légers du Ca des carbonatites comparé à la valeur moyenne du manteau reflète une contribution de matériel recyclé dans leur source mantellique. Ces travaux de recherche visent à explorer les grandes applications du fractionnement isotopique du Ca et du Sr à haute température
The formation of the Solar System and its evolution remain poorly known despite the explosion of space exploration in the mid 20th century. Meteorites and terrestrial igneous rocks are particularly useful objects of study for gaining insights into the formation and evolution of the Earth: the former existed before the planets and the latter reflect the composition of the terrestrial mantle. For this thesis, we performed Ca, Sr and Rb isotopic analyses using MC-ICP-MS technique on a variety of terrestrial and extra-terrestrial rocks. The fractionation of Ca and Sr stable isotopes allows for tracing processes and source effects and Rb-Sr system enables us to date primordial events. Chondrules, a major component of chondrites, are analysed for Ca isotopic composition to test and confirm the pebble accretion model for the formation of the Earth. The timing of the heating event of thermally metamorphosed carbonaceous chondrites is estimated using Rb-Sr chronology and reveals the process of the event as impacts in the asteroid belt. From Earth, komatiites, OIBs and MORBs samples are analysed to estimate the Ca and Sr isotopic composition and evolution of the mantle. The stable isotopic composition of Sr in the mantle is homogenous through the evolution of the mantle while Ca isotopes reveal preservation of early heterogeneities. Carbonatites, rare igneous rocks containing 50 % of carbonate minerals, are studied for Ca isotopic composition in order to indicate their origin. We suggest that the enrichment in lighter Ca isotopes of the carbonatites compared to the bulk silicate Earth’s value derives from a contribution of recycled components through subduction in their mantle source. This thesis explores the wide applications of Ca and Sr isotopic fractionation in high temperature geochemistry

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Brassinnes, Stéphane. "Relations cumulat-liquide dans les massifs alcalins et carbonatitiques: les cas des massifs de Vuoriyarvi (Péninsule de Kola, Russie) et de Tajno (N.E. Pologne)." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210796.

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Les carbonatites sont des roches magmatiques essentiellement composées de carbonates (calcite et/ou dolomite) d'origine magmatique. Leur statut pétrographique en tant que liquide magmatique ou cumulat reste à l'heure actuelle fort contreversé. Cette thèse de doctorat à pour objectif une étude pétrographique fine de ces roches couplée à des microanalyses in-situ des éléments en trace des principaux minéraux (carbonate, apatite).
Doctorat en sciences, Spécialisation géologie
info:eu-repo/semantics/nonPublished

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Donczew, Anna. "An Innovative In-Tunnel Seismic Study for Sustainably Extracting Apatite Ore at the Siilinjärvi Mine, Eastern Finland." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388162.

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Siilinjärvi located in eastern Finland is presently the only phosphate mine with significant phosphorus production in western Europe. Phosphate rock and phosphorus are known as a critical raw material for the European Union due to their economic importance and being prone to the supply risks. Securing their sustainable exploration as well as extraction is hence important. At Siilinjärvi, the phosphate rocks appear within a major Archean alkaline and carbonatite system deformed by several shear zones and intruded by dike systems. By understanding their spatial and temporal relationships an improved exploration and extraction of the ore is possible, which in turn will contribute to the sustainable extraction of this critical material. In October 2018 a novel in-tunnel seismic survey was conducted in the Siilinjärvi open-pit mine. The objective of the study was to employ an in-tunnel seismic survey intersecting several major shear zones running on the eastern side of the main pit, with the idea of characterising its geometry and relationship with the mineralization. The use of the existing mine infrastructure (a water-drainage tunnel) makes the acquisition of the data quite novel in open-pit mines. The water-drainage tunnel nearly in the bottom of the pit crosscutting several major shear zones and dikes was used to enable bench-tunnel seismic data acquisition. High-quality data were acquired using 144 receivers inside the tunnel, with the sources located both inside the tunnel (Bobcat-mounted vertical drophammer) and on the surface (combined explosives and Bobcat-drophammer). Results obtained show at least two reflections interpreted to originate from subvertical shear zones intersecting the tunnel illustrating the importance of such surveys for shear-zone imaging and site characterization. Based on a careful study of a number of shot records, delay in arrival times and partial amplitude lose, these reflections are interpreted to be backscattered surface-waves generated from the shear zones.
Siilinjärvi i östra Finland är just nu den enda fosfatgruvan med en betydande fosforproduktion inom den Europeiska Unionen. Fosfater och fosfor är viktigt för EU på grund av deras ekonomiska betydelse och begränsade tillgång. Den fosforbärande bergarten i Siilinjärvi befinner sig i ett stort Arkeiskt alkalisk och karbonatit-komplex som är deformerad av flera skjuvzoner och intruderat gångsystem. En förbättring av sökandet och utvinnandet av denna viktiga malm skulle vara möjligt genom en ökad förståelse för de spatiala och temporala relationerna i komplexet. Syftet med denna studie var att tillämpa en ny seismisk undersökning, baserad på existerande infrastruktur i gruvan, för en bättre geologisk förståelse och därmed en förbättrad exploatering. En innovativ seismisk undersökning av tunnlar gjordes i Siilinjärvis dagbrott oktober 2018. En vattendräneringstunnel nästan i botten av brottet som korsar fem skjuvzoner användes för att mäta seismiskt tunnel-data. Hög kvalitativ data samlades in genom att använda 144 mottagare inuti tunneln med källor lokaliserade både inuti tunneln, i form av en vertikal dropphammare monterad på en Bobcat, och på ytan i form av en kombination av sprängning och Bobcatmoterad dropphammare. Två reflektioner tolkades att ha sitt ursprung från subvertikala skjuvzoner som korsar tunneln vilket visar på vikten av dessa typer av undersökningar för skjuvzons detektion och områdes karaktärisering.

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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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Ogungbuyi, Ibiyemi Prisca. "Geochemical and isotopic constraints on the source regions of phanerozoic carbonatites and associated alkaline rocks from the Zandkopsdrift complex of Namaqualand, South Africa, and the Marinkas Quellen, and Dicker Willem complexes in Namibia." Doctoral thesis, Faculty of Science, 2020. http://hdl.handle.net/11427/32311.

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This is a study of Phanerozoic carbonatites and related alkaline silicate rocks from Zandkopsdrift in Namaqualand, South Africa (55 Ma), and Marinkas Quellen (529 Ma), and Dicker Willem (49 Ma) in southern Namibia, all emplaced within the Proterozoic Namaqua Natal province. The aims of this thesis are to characterise their mantle source region, including the timing and nature of the metasomatism that affected their sources, and to constrain their petrogenesis, particularly the relationships between the carbonatites and associated silicate igneous rocks. These associated silicate igneous rocks include olivine melilitite, aillikite and alkaline lamrophyre at Zandkopsdrift, nepheline syenite and trachyte at Marinkas Quellen, and ijolite and trachyte at Dicker Willem. At both Marinkas Quellen and Dicker Willem, the trachytes appear to be derived primarily from fenitised country rock. The major and trace element characteristics, enrichment in LREE and other incompatible elements, large Zr-Hf-Ti depletions and high Zr/Hf ratios all appear to have been inherited from a metasomatised mantle source region rather than being the result of residual source mineralogy. The δ18O and δ13C values of carbonate in the study locations vary significantly. The δ13C values (-3.9 to -8.8 ‰) are within the range of mantlederived carbonatites, whereas the δ18O values are often significantly higher (+8.64 to +22.22 ‰, versus SMOW) for “mantle-derived” carbonatites. The higher δ18O values observed are most likely attributable to low-temperature, post-emplacement alteration by hydrous fluids. O-isotope thermometry of the silicate mineral pairs (clinopyroxene, amphibole, and biotite) gives close to magmatic temperatures (≈800 oC), whereas the equilibration temperature of calcite-silicate mineral pairs is lower. The carbonatite and associated igneous rock samples contain unradiogenic Sr and mildly radiogenic Nd isotope compositions below and above Bulk Earth/CHUR values respectively. This suggests that carbonatite magmas were generated from sources with long-lived Rb/Sr lower than, and Sm/Nd higher than, the primitive mantle. In ƐHf(t)-ƐNd(t) space, the carbonatites and associated silicate rocks plot as much as 8 ƐHf units below the terrestrial ƐNd-ƐHf array, indicating mixing of a source with moderate ƐNd and exceptionally unradiogenic Hf isotope compositions. The radiogenic Pb isotope composition of the carbonatites (206Pb/204Pbi ratios from 18.06 to 22.38), is consistent with a source having high U/Pb, akin to the HIMU mantle end member. The radiogenic isotopes of the carbonatites and the alkaline silicate rocks seem most consistent with a dominantly asthenospheric source, with minor contributions from lithospheric sources. There is little evidence supporting the derivation of carbonatites at the three complexes from parental hybrid carbonate-silicate magmas. Rather, the evidence seems most consistent with deriving the carbonatites directly from very low-degree mantle melts, which subsequently become variably differentiated, first by melt-rock interaction in the mantle and subsequently by fractional crystallization. The associated silica undersaturated silicate igneous rocks appear most likely to represent relatively primitive (melilitites) to differentiated (nepheline syenites) melts of metasomatic wehrlites that were formed by carbonatite-peridotite melt-rock interaction.

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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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46

Gomide, Caroline Siqueira. "Geoquímica e química mineral de carbonatitos e isótopos estáveis em carbonatitos da província ígnea do alto Paranaíba." reponame:Repositório Institucional da UnB, 2015. http://dx.doi.org/10.26512/2015.12.T.20104.

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Tese (doutorado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2015.
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A Província Ígnea do Alto Paranaíba (APIP), resultado de intenso magmatismo alcalino que gerou corpos intrusivos e extrusivos de afinidade kamafugítica, é uma das maiores províncias ultramáficas-ultrapotássicas mundiais. Os complexos carbonatíticos presentes na APIP são intrusões multifásicas formadas por rochas das séries bebedourítica, carbonatítica e foscorítica. Esta tese aborda a composição isotópica de carbonatos e sulfetos presentes em carbonatitos da província e inclui, além das análises isotópicas, a obtenção de novos dados petrográficos, imagens de microscopia eletrônica, análises de química mineral e geoquímica de rocha total. No trabalho investiga-se a relação entre a geoquímica de rocha total e composição de isótopos estáveis de carbonatitos pertencentes aos complexos Tapira, Araxá, Salitre, Serra Negra, Catalão I e Catalão II da APIP e, para efeito de comparação, do Complexo Jacupiranga (afiliação sódica), na província Grossa Ponta. Os dados de litogeoquímica aliados a critérios mineralógicos permitiram classificar os carbonatitos em cinco grupos (C1 a C5) e definir um índice de evolução (BaO/(BaO+SrO)) para rochas carbonatíticas. Os carbonatitos evoluem de calciocarbonatitos enriquecidos em apatita para magnesiocarbonatitos enriquecidos em Ba, Sr e REE. Esta evolução é marcada principalmente pelo fracionamento de apatita, flogopita, dolomita, calcita e enriquecimento em monazita, norsethita, e estroncianita. Os dados de isótopos estáveis registram uma ampla variação nos complexos da APIP, em comparação com Jacupiranga, tendo em vista que as intrusões da APIP se estabeleceram em níveis mais rasos, permitindo a atuação de uma diversidade muito maior de processos petrogenéticos, incluindo cristalização fracionada, imiscibilidade de líquidos, desgaseificação e interação com sistemas hidrotermais e carbohidrotermais. Uma diversidade de carbonatos foi encontrada na provincia incluindo, além de calcita e dolomita (os dois carbonatos mais comuns), estroncianita, olekminskita, burbankita, ancylita, norsethita, baritocalcita, basnaesita, parisita e benstonita. Calciocarbonatitos e magnesiocarbonatitos pouco evoluídos são tipicamente compostos de calcita e dolomita de alta temperatura, com exsoluções de burbankita, olekminskita e ancylita, e com microinclusões de nyerereita e gregoryita/zemkorita tipos de carbonato descritos pela primeira vez na Província. Carbonatitos intermediários apresentam estrontianita, norsethita e baritocalcita como fases liquidus, além de calcita e dolomita. Carbonatitos tardios podem apresentar, além desses, carbonatos de terras raras (ancylita, bastnaesita e parisita). Estudos texturais, mineralógicos e de composição ajudaram a entender processos como evolução magmática por cristalização fracionada, desgaseificação e processos fluidos tardios.
The Alto Parnaíba Igneous Province (APIP) results from an intense alkaline magmatism that generated intrusive and extrusive bodies of kamafugitic affinity, and it is one of the largest ultramaficultrapotassic provinces in the world. Carbonatite complexes present in the APIP are multiphase intrusions formed by rocks derived from the bebedourite, carbonatite and foscorite series. This thesis discusses the APIP carbonatites on the basis of the stable isotope composition of their carbonates and sulphides, petrographic data, high-resolution electron images, mineral chemistry and whole rock geochemistry. The relationship between whole rock geochemistry and stable isotope composition of carbonatites belonging to the Tapira, Araxá, Salitre, Serra Negra, Catalão I and Catalão II complexes of APIP is investigated, and compared with the Jacupiranga Complex, an example of sodic complex from the Ponta Grossa Province. The geochemical and mineralogical criteria were used to divide the carbonatites into five groups (C1 to C5), and to propose a chemical index (BaO/(BaO+SrO) to gauge the evolution of the carbonatite carbonatite magma. The APIP carbonatites evolve from apatite-rich calciocarbonatite to magnesiocarbonatite enriched in Ba, Sr and REE, mostly as a result of the fractionation of apatite, phlogopite, dolomite, calcite and enrichment in monazite, norsethite, strontianite. Data from stable isotopes record a wide variety of evolution processes in the APIP magmas, fractional crystallization, such as liquid immiscibility, degassing and interaction with hydrothermal and carbohydrothermal systems, resulting from their emplacement at shallower depths than Jacupiranga. A variety of carbonates is reported from the APIP carbonatites in addition to the essential calcite and dolomite, including strontianite, olekminskite, burbankite, ancylite, norsethite, barytocalcite, basnaesite, parisite and benstonite. Early-stage calciocarbonatites and magnesiocarbonatites are typically composed of high temperature calcite and dolomite which contain exsolutions of burbankite, olekminskite and ancylite, as well as microinclusions of nyerereite and gregoryite/zemkorite a type of carbonate identified for the first time in the Province. Intermediate carbonatites have strontianite, norsethite and barytocalcite as liquidus phases, in addition to calcite and dolomite. In late-stage carbonatites REE carbonates (ancylite, bastnaesite and parisite) also crystallize as liquidus phases. Textural, mineralogical and compositional evidence helped to understand processes such as magma evolution by fractional crystallization, degassing processes and interaction with late-stage fluids in the studied complexes.

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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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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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49

Sharpe, Joanna Carleton University Dissertation Geology. "Geochemistry of the Cargill Carbonatite Complex, Kapuskasing, Ontario." Ottawa, 1987.

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50

Moore, Meghan. "Carbonatite-related rare-earth mineralization in the Bear Lodge alkaline complex, Wyoming: Paragenesis, geochemical and isotopic characteristics." ElSevier, 2014. http://hdl.handle.net/1993/23991.

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The Bear Lodge alkaline complex in northeastern Wyoming (USA) is host to potentially economic rare-earth mineralization in carbonatite and carbonatite-related veins and dikes that intrude heterolithic diatreme breccias in the Bull Hill area of the Bear Lodge Mountains. The deposit is zoned and consists of pervasively oxidized material at and near the surface, which passes through a thin transitional zone at a depth of ~120-183m, and grades into unaltered carbonatites at depths greater than ~183-190m. Carbonatites in the unoxidized zone consist of coarse and fine-grained calcite that is Sr-, Mn- and inclusion-rich and are characterized by the presence of primary burbankite, early-stage parisite and synchysite with minor bastnäsite that have high (La/Nd)cn and (La/Ce)cn values. The early minerals are replaced with polycrystalline pseudomorphs consisting of secondary rare-earth fluorocarbonates and ancylite with minor monazite. Different secondary parageneses can be distinguished on the basis of the relative abundances and composition of individual minerals. Variations in key element ratios, such as (La/Nd)cn, and chondrite-normalized profiles of the rare-earth minerals and calcite record multiple stages of hydrothermal deposition involving fluids of different chemistry. A single sample of primary calcite shows mantle-like δ18O V-SMOW and δ13C V-PDB values, whereas most other samples are somewhat depleted in 13C (δ13C V-PDB ≈ –8 to –10‰) and show a small positive shift in δ18O V-SMOW due to degassing and wall-rock interaction. Isotopic re-equilibration is more pronounced in the transitional and oxidized zones; large shifts in δ18O V-SMOW (to ~ 18‰) reflect input of meteoric water during pervasive hydrothermal and supergene oxidation. The textural relations, mineral chemistry, and C and O stable-isotopic variations record a polygenetic sequence of rare-earth mineralization in the deposit. With the exception of one Pb-poor sample showing an appreciable positive shift in 208Pb/204Pb value (~39.2), the Bear Lodge carbonatites are remarkably uniform in their Nd, Sr and Pb isotopic composition: (143Nd/144Nd)i=0.512591-0.512608; εNd=0.2-0.6; (87Sr/86Sr)i=0.704555-0.704639; εSr=-1.5-2.7; (206Pb/204Pb)i=18.071-18.320; (207Pb/204Pb)i=15.543-15.593; (208Pb/204Pb)i=38.045-39.165. These isotopic characteristics indicate that the source of the carbonatitic magma was in the subcontinental lithospheric mantle, and modified by subduction-related metasomatism. Carbonatites are interpreted to be generated from small degrees of partial melt that may have been produced via interaction of upwelling asthenosphere giving a small depleted MORB component, with an EM1 component likely derived from subducted Farallon crust.

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Dissertations / Theses on the topic 'Carbonatites'

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