Dissertations / Theses on the topic 'Manganese ore'
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Apostolopoulos, D. G. "The manganese oxide ore deposits of the Nevrokopi district, Macedonia, Greece." Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374035.
Full textAkil, Cem. "Optimization Of Conditions To Produce Manganese And Iron Carbides From Denizli-tavas Manganese Ore By Solid State Reduction." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608188/index.pdf.
Full textC with MoSi2 heating elements. After each experiment weight loss data were obtained and converted to percentage reduction. X-Ray, SEM-EDS and chemical analyses were done in order to determine whether or not carbide phases have been obtained, and calculate the composition of the product. Considering the experimental results, the optimum conditions found for reduction of Denizli-Tavas manganese ore were 1250 °
C, 4 hours, 100% of stoichiometric amount of active carbon and 5% CaO addition. Under the optimum conditions 83.85% reduction of calcined ore was obtained.
Åberg, Franz. "Mineralogical Study of Manganese Bearing Skarn Minerals and Manganese Content in Magnetite in the Dannemora Skarn Iron Ore Deposit." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-263473.
Full textSkarn-järnmalmsfyndigheten i Dannemora är belägen i den nordöstra delen av Bergslagen. Järnmalm och mindre sulfidmineraliseringar har blivit brutna sedan 1400-talet. Gruvan stängde 1992 men togs i produktion igen under 2012. Gruvan stängs återigen under 2015. Fyndigheten är omgiven av 1.9 Ga gamla sedimentära och vulkaniska bergarter. Järnmalmsfyndigheten innehåller både manganrika och manganfattiga järnmalmer. Syftet med denna studie är att undersöka varför fyndigheten har förhöjda halter av mangan. Förändringar av manganhalter och olika värdbergarter borde ge en annorlunda mineralsammansättning i de olika miljöerna. För att svara på dessa frågor skall både mikroskopiska och kemiska undersökningar göras för att bestämma och identifiera olika mineralogiska associationer. Petrografiska och kemiska studier indikerar två olika huvudtyper av amfiboler: kalciumhaltiga amfiboler och Mg-Fe-Mn-Li-amfiboler. Kalciumamfibolerna är generellt mer spridda i proverna medan Mg-Fe-Mn-Li-amfibolerna är mer koncentrerade till de mer manganrika sektionerna. När koncentrationen av mangan är högre blir granater och även epidot och olivin vanligare, speciellt närmare vulkaniska bergarter.
Kiracofe, Zachary Aaron. "Assessing the geologic sources of manganese in the Roanoke River watershed." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52890.
Full textMaster of Science
Harawa, Esau Tonderai. "Mineralogy and geochemistry of structurally-controlled metasomatic alteration of carbonate-rich manganese ore at Mamatwan Mine, Kalahari Manganese Field." Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/4717.
Full textCardakli, Ismail Seckin. "Production Of High Carbon Ferromanganese From A Manganese Ore Located In Erzincan." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612604/index.pdf.
Full textUpp, Oden Karen Lee 1959. "Bacterially catalyzed reductive dissolution of manganese for the liberation of silver from refractory ore." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277986.
Full textBodiba, A. L. "X-ray spectroscopic method development for quantitative analysis of manganese ore in the Kalahari basin." Thesis, Vaal University of Technology, 2016. http://hdl.handle.net/10352/386.
Full textKononov, Ring Materials Science & Engineering Faculty of Science UNSW. "Carbothermal solid state reduction of manganese oxide and ores in different gas atmospheres." Publisher:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41459.
Full textAndrade, Emily Mayer de. "Estudo de depressores na flotação de finos de minério de manganês com oleato de sódio." Programa de Pós-Graduação em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto, 2010. http://www.repositorio.ufop.br/handle/123456789/2379.
Full textApproved for entry into archive by Neide Nativa (neide@sisbin.ufop.br) on 2013-02-27T15:01:23Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO_EstudoDepressoresFlotação.pdf: 2366097 bytes, checksum: 9beeb25612b4624e59d30fb2c2743275 (MD5)
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Neste trabalho foram efetuados estudos de depressores na flotação de uma amostra de finos de minério sílico-carbonatado de manganês (estocados como rejeito) da Unidade Morro da Mina / RDM, localizada em Conselheiro Lafaiete-MG. Foram realizados testes de microflotação em tudo de Hallimond modificado, curvas de potencial zeta dos minerais puros na presença e ausência de reagentes e ensaios de flotação em bancada com amostra do resíduo do minério deslamado. Os reagentes estudados foram: fluorsilicato de sódio, metasilicato de sódio, amido de milho, dextrina branca e alguns tipos de quebracho (Floatans T0, T1, T5 e M3) utilizando-se oleato de sódio como coletor. A eficiência dos depressores testados na microflotação em relação à seletividade para a separação do quartzo dos minerais de manganês foi: floatan M3 > floatan T1> fluorsilicato de sódio > metassilicato de sódio > amido de milho > floatan T0 > dextrina > floatan T5. Os pontos isoelétricos dos principais minerais de Mn e ganga presentes neste minério foram determinados: rodonita (pH 2,8), rodocrosita (pH 10,5) e quartzo (pH 1,8). O estudo da adsorção que caracteriza a interação dos reagentes com as superfícies dos minerais mostrou ser de caráter específico. Os depressores mais eficientes na flotação em bancada entre os minerais de Mn e de ganga foram: floatan M3, floatan T1 e fluorsilicato de sódio, onde foram obtidos concentrados com teores de Mn, SiO2 e Al2O3 de aproximadamente 30, 17 e 10 %, respectivamente, para os três depressores testados. No entanto, a recuperação metalúrgica de Mn foi de 72,5 % para o floatan M3, 51 % para o floatan T1 e 45,2 % para o fluorsilicato de sódio. Posteriormente, efetuaram-se estudos preliminares de calcinação desse minério deslamado. O mais alto teor de Mn encontrado foi de aproximadamente 30 % com perda de massa de 11,2 % para temperatura de 1000 °C. ____________________________________________________________________________________________________
ABSTRACT: Flotation depressants were studied from silicate-carbonate manganese ore samples (waste) at RDM – Morro da Mina, in Conselheiro Lafaiete – MG, Brazil. Micro-flotation tests were conducted in a modified Hallimond cell, also zeta potential curves for pure minerals in the presence or lack of reagents and bench-scale flotation tests for deslimed ore waste sample. The following reagents were studied: sodium fluorosilicate, waterglass, starch, white dextrin, some quebracho kinds (Floatans T0, T1, T5 e M3) and sodium oleate as a collector. The efficiency of the depressants during the micro-flotation regarding the selection for separation of quartzo from manganese mineral was as it follows: floatan M3> floatan T1> sodium fluorosilicate > waterglass > starch > floatan T0 > dextrin > floatan T5. The isolectric points (pl) of the main ore were also determined as rhodonite (pH 2.8), rhodochrosite (pH 10.5) and quartz (pH 1.8). The adsorption test, characterized by the interaction of reagents and mineral surfaces, indicates its specific nature. The most efficient depressants in bench-scale flotation test among Mn ore and ganga were floatan M3, floatan T1 and sodium fluorosilicate containing Mn, SiO2 and Al2O3 concentrations of approximately 30, 17 and 10%, respectively, for all depressants herein mentioned. However, the metallurgical recovery for Mn was 72,5 % when using floatan M3, 51 % for floatan T1 and 45,2% for sodium fluorosilicate. Furthermore, calcination preliminary studies were conducted and the highest concentration of Mn found was approximately 30%, with an 11.2% weight loss for a 1000°C temperature.
Polteau, Stéphane. "The early proterozoic Makganyene glacial event in South Africa : its implication in sequence stratigraphy interpretations, paleoenvironmental conditions and iron and manganese ore deposition." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1007612.
Full textDel, Rio Salas Rafael Eduardo. "METALLOGENESIS FOR THE BOLÉO AND CANANEA COPPER MINING DISTRICTS: A CONTRIBUTION TO THE UNDERSTANDING OF COPPER ORE DEPOSITS IN NORTHWESTERN MÉXICO." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145742.
Full textTsikos, Harilaos. "Petrographic and geochemical constraints on the origin and post-depositional history of the Hotazel iron-manganese deposits, Kalahari Manganese Field, South Africa." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005599.
Full textFERNANDES, ALBERTO de A. "Desenvolvimento de processo quimico para obtencao da nsutita (gama-MnO sub(2)) de alta densidade empregada na fabricacao de pilhas." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11021.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Feng, Yuexing. "40Ar/39Ar dating of young supergene Mn-Oxides : implication for late Cainozoic weathering history and landscape evolution, Mary Valley, Southeast Queensland, Australia /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19080.pdf.
Full textKnaust, Jacqueline M. "Self-assembly of one-, two, and three-dimensional coordination networks /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3091937.
Full textFairey, Brenton John. "Genesis of karst-hosted manganese ores of the Postmasburg Manganese Field, South Africa with emphasis on evidence for hydrothermal processes." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1020904.
Full textRasmeni, Sonwabile. "Lithostratigraphic correlation, mineralogy and geochemistry of the lower manganese orebody at the Kalagadi Manganese Mine in the Northern Cape Province of South Africa." Thesis, University of Fort Hare, 2012. http://hdl.handle.net/10353/d1016155.
Full textTerracin, Matthew Theodore. "Petrography, geochemistry and origin of atypical sedimentary-igneous contact relationships at the base of the Hotazel Formation around Middelplaats, Northern Cape Province, RSA." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1012985.
Full textRyabova, Anna. "Électrocatalyse de la réduction de l'oxygène et du peroxyde d'hydrogène sur les oxydes de manganèse." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF011/document.
Full textManganese oxides are of great interest due to their catalytic activity towards the ORR (the oxygen reduction reaction) in alkaline media and can be used as noble metal-free materials for the cathode in liquid and polymer electrolyte alkaline fuel cells. The present thesis is devoted to the investigation of the ORR activity of manganese oxides. It was shown that Mn2O3 with bixbyite structure has a better catalytic activity toward the ORR in alkaline media than other investigated manganese oxide, the surface activity of Mn2O3 is only 4 times lower than that of Pt at an overvoltage of 0.3 V (RHE). The link between the structure of Mn oxides and the ORR activity is found: the specific ORR activity exponentially increases with the potential of the surface Mn(III)/Mn(IV) red-ox couple. To ensure the high electrocatalytic activity of Mn2O3, it is necessary to add carbon to the electrode composition, as well as to keep potential above 0.7 V (RHE)
Guthrie, James McKamey. "Evaluating the suitability of the human toenail as a biomonitor for manganese status the one source cohort /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4929.
Full textThe entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 25, 2007) Vita. Includes bibliographical references.
Allen, George B. "Economic Geology of the Big Horn Mountains of West-Central Arizona." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/244099.
Full textAZZILEY, AZZIBROUCK GEORGES. "Sedimentologie et geochimie du francevillien b (proterozoique inferieur). Metallogenie des gisements de manganese de moanda, gabon." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13041.
Full textOngen, Sinan. "Les échanges métasomatiques entre granitoïdes et encaissants particuliers (calcaires, dolomies, ultrabasites, séries manganésifères) : l’exemple de la péninsule de Biga, Anatolie nord-ouest, Turquie." Nancy 1, 1992. http://www.theses.fr/1992NAN10349.
Full textSalomon, Hélène. "Les matières colorantes au début du paléolithique supérieur : sources, transformations et fonctions." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13971/document.
Full textDespite an increasing number of studies, colouring materials are still poorly understood among excavation remains. Their attraction lies in their capacity to bring to light diverse and complex skills, but also in their intense colouring power and their contrasting colours: red and black, which still possess a symbolic value. These highly-symbolic materials may, therefore, highlight the “conceptual” practices of prehistoric men and give access to their symbolic world and thought. In such a particular context as the transition between the Middle and the Upper Palaeolithic, these remains, which are very abundant in most excavations, offer the possibility, through analysis, to get an exceptional insight into the way of life of the last Neanderthals. The Châtelperronian site of the “Grotte du Renne”, in Arcy-sur-Cure (Yonne), is a landmark. It was excavated beween 1949 and 1963 by André Leroi-Gourhan: Numerous colouring materials were discovered there, and Leroi-Gourhan developed theories about their transformation and uses which so far have not been tested, and have remained unchallenged. Since their discovery, the assumption is that those minerals were heated in a controlled way, in order to modify their colour. It is indeed well-known that heat transforms yellow materials (iron oxides) in orange, red or purple materials (other iron oxides). From this hypothesis originates the theory according to which Neanderthals exploited colouring materials as pigments for symbolic or even aesthetic purposes. But the theory has so far never been proved true. Our study combines several sets of data, obtained from different methods. Physico-chemical and petrological analyses were carried out on the colouring materials. These data were related to their location on the site, in association with exceptionally well preserved “hut” structures. Furthermore, a series of experimentations, aimed to characterize powders obtained via different methods (grinding and crushing on the one hand, abrasion on the other hand). The comparison of all these data enabled us to identify the various technical choices which informed the supply in colouring minerals in all the Châtelperronian levels of the Grotte du Renne. It was thus possible to demonstrate that none of these materials, either red or black, was heated before being used, contrary to what had been assumed so far. The supply in colouring materials was as carefully organised as for other materials (flint, for example); they were collected in geological formations occasionally showing on the surface, at more than 10 km from the cave. The exploitation of these geological sites did not vary during the whole Châtelperronian period, and privileged materials which can easily be ground into powder. Part of their supply was ground coarsely in order to cover large surface areas (soils or hides) as preservative or to clean them up. The remaining materials were destined to more meticulous activities, which required a fine, regular, and highly-colouring powder. In this latter case, the Neanderthals of the Grotte du Renne used those products when working on bone materials (bone or mammoth ivory), and used them also for their sheer colour. The set of colouring minerals from the Grotte du Renne reveals Neanderthals’ in-depth knowledge of materials; they understood perfectly well their properties and qualities, and used them extensively, so that the Châtelperronian site must have been a literally dazzling sight, all red and black. The “chaîne opératoire” which transpires from our analysis shows very sophisticated techniques, and an advanced “technological” knowledge. They are witness to surprising capacities and a highly-evolved pattern of thought. Keywords: Colouring materials; Ochre; Haematite; Manganese; Middle/Upper Palaeolothic transition; Châtelperronian; Arcy-sur-Cure; Grotte du Renne; Heating; Grinding; Skhul; Les Maîtreaux; Combe Saunière
López, Hernández Irene. "Catalizadores metálicos estructurados en reacciones de Química Sostenible." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/172246.
Full text[CA] En aquesta tesi doctoral s'ha investigat sobre l'ús de catalitzadors metàl·lics estructurats en reaccions relacionades amb la Química Sostenible. En primer lloc, s'ha estudiat l'eliminació dels òxids de nitrogen mitjançant la seua reducció catalítica selectiva emprant amoníac. S'han emprat catalitzadors bimetàlics Mn-Fe suportats sobre zeolites amb diferent relació Si/Al i morfologia (BEA, CHA, ITQ-2 and FAU), materials mesoporosos (MCM-41 and SBA-15) i òxids metàl·lics (MgO, TiO2 and γ-Al2O3). S'ha comprovat que existeix una forta influència del tipus de suport sobre l'activitat catalítica, obtenint-se els millors resultats amb els catalitzadors els suports dels quals presentaven propietats àcides i que tenien una elevada àrea superficial. Per al cas de les zeolites, la seua morfologia no influeix tant en l'activitat catalítica com la relació Si/Al, obtenint-se els millors resultats amb els catalitzadors suportats sobre zeolites amb alta relació Si/Al. Els catalitzadors suportats sobre òxids metàl·lics han mostrat millors resultats amb aquells catalitzadors suportats en òxids que presenten alta àrea superficial i propietats àcides. Els resultats més prometedors, sobretot per la seua elevada estabilitat hidrotèrmica, es van obtindre amb el catalitzador preparat amb la zeolita CHA (Si/Al = 10), que manté tota la seua activitat després de ser sotmés a un envelliment. En segon lloc, s'ha estudiat l'activitat en l'oxidació de CO de catalitzadors basats en Ag i Ag-Au, suportats sobre la zeolita ITQ-2. Els catalitzadors de plata es van emprar per a estudiar la influència de la naturalesa de les espècies de Ag en l'activitat catalítica. Per a això, els catalitzadors s'han preparat mitjançant tres mètodes diferents: impregnació a volum de porus, intercanvi iònic, i amb nanoclusters de Ag25(SR)18 suportats. L'anàlisi dels resultats catalítics obtinguts amb els diferents materials, juntament amb els resultats de caracterització han permés determinar que l'espècie activa en aquesta reacció és la plata metàl·lica, aconseguint els millors resultats amb els catalitzadors que presentaven una major quantitat de d'aquesta espècie en la seua superfície, la qual cosa ve determinada pel mètode d'addició de la plata i per l'evolució de les espècies durant la seua activació i durant els cicles de reacció. D'altra banda, els catalitzadors bimetàl·lics Ag-Au van ser preparats mitjançant la impregnació de nanoclusters AgxAu25-x(SR)18 sobre la zeolita ITQ-2. Els resultats van mostrar que la millor activitat era obtinguda quan es produïa la formació de nanopartícules aliades de Ag-Au, que afavorien l'adsorció del CO i del O2. Aquestes partícules es formaven després de la destrucció incompleta dels lligands tiolats. Es va comprobar que, durant les condicions de reacció, tots els nanoclusters evolucionaven cap a la formació de nanopartícules Ag-Au independentment del pretractament aplicat. Aquests resultats han permés mostrar que la reacció d'oxidació de CO és una eina molt útil per a seguir l'evolució dels nanoclusters metàl·lics durant els processos d'activació i durant la reacción. Finalment, s'ha estudiat l'activitat en la semihidrogenació del fenilacetilè a estiré dels catalitzadors basats en nanoclusters d'or amb diferent nombre d'àtoms, Au25 i Au11, i amb diferents lligands (tiolat per a Au25 i fosfina per a Au11). Aquests catalitzadors van ser suportats sobre òxids metàl·lics (MgO, γ-Al2O3 i hidrotalcita Mg/Al), observant-se que l'activitat depén tant de la composició dels nanoclusters, com del suport i del pretractament emprat. S'ha determinat que l'activació de l'hidrogen és un factor clau, estant això directament relacionat amb les propietats àcid/base del suport. Els millors resultats es van obtindre amb els catalitzadors preparats amb nanoclusters Au25 sobre la hidrotalcita Mg/Al, la qual presenta una basicitat intermèdia, la qual cosa afavoreix l'activació de l'hidrogen, però evita la sobrehidrogenación dels alquins als alcans. Els resultats obtinguts en les diferents reaccions amb els diferents catalitzadors han mostrat que la interacció suport-metall és fonamental a l'hora de dissenyar catalitzadors actius en les reaccions estudiades. Aquesta interacció depén en gran manera de les propietats àcid/base del suport i dels pretractaments aplicats als catalitzadors. S'ha comprovat, a més, que els centres metàl·lics evolucionen al llarg de la reacción, podent portar a la formació de noves espècies que poden ser més o menys actives segons la reacció estudiada.
[EN] The use of structured metallic catalysts in reactions related to Sustainable Chemistry have been investigated in this Doctoral Thesis. Firstly, the removal of NOX through the selective catalytic reduction with ammonia has been studied. Mn-Fe catalysts supported on zeolites with different Si/Al ratio and morphology (BEA, CHA, ITQ-2 and FAU), on mesoporous materials (MCM-41 and SBA-15) and on metallic oxides (MgO, TiO2 and γ-Al2O3) have been employed. It has been proved that there is a strong influence of the type of support in the catalytic activity, obtaining the best results with the catalysts supported on materials with acidic properties and high surface area. The morphology of zeolite-based catalysts does not influence the catalytic activity as much as the Si/Al ratio does, obtaining the best results with the catalysts supported on zeolites with high Si/Al. It has been shown that the activity of the catalysts supported on metallic oxides is strongly influenced by the surface area of the support and by its acid/base properties, obtaining the best results with the catalysts supported on oxides with high surface area and acidic properties. Furthermore, all catalysts present a selectivity towards N2 greater than 90 %. The most promising results, mainly for its hydrothermal stability, are obtained with the catalysts prepared with CHA zeolite (Si/Al = 10), that maintain the activity after the aging. Secondly, the activity in the catalytic oxidation of CO of Ag and Ag-Au catalysts supported on ITQ-2 zeolite has been studied. Silver-based catalysts were used in order to investigate the influence of the nature of silver species in the catalytic activity. For this, catalysts were prepared using different methods, leading to different silver species: incipient wetness impregnation, ion exchange, and as supported Ag25(SR)18 nanoclusters. The catalytic results together with the characterization results have allowed to determine that metallic silver is the active specie in this reaction, obtaining the best results with the catalysts containing a higher concentration of this species on the surface. This is determined by the preparation method and by the evolution of these species during the activation and the reaction cycles. In the other hand, the Ag-Au bimetallic catalysts were prepared by the impregnation of AgxAu25-x(SR)18 nanoclusters on the ITQ-2 zeolite. The results showed that the best activity is obtained when Ag-Au alloy nanoparticles are formed, favouring the CO and O2 adsorption. These types of particles were formed after the partial destruction of thiolate ligands that are protecting the nanoclusters, that is favoured by the pretreatment with hydrogen. However, it has been shown that during reaction, nanoclusters evolved to the formation of Ag-Au alloyed nanoparticles regardless of the pretreatment applied. These results proved that the CO oxidation reaction is a useful tool to follow the metallic nanoclusters evolution during the activation processes and during reaction. Finally, the activity of catalysts based on gold nanoclusters with different number of atoms, Au25 y Au11, and different ligands (thiolates for Au25 and phosphines for Au11) in the semihydrogenation of phenylacetylene to styrene has been studied. These catalysts were supported on various metallic oxides (MgO, γ-Al2O3 and Mg/Al hydrotalcite), observing that catalytic activity depends on the nanoclusters composition, but also on the support and on the pretreatment. It has been shown that H2 partial activation is a key factor, which is directly related to the acid/base properties of the support. The best results were obtained with the catalysts prepared with Au25 nanoclusters supported on the Mg/Al hydrotalcite, that presents a medium basicity between MgO and alumina, favouring the hydrogen activation, but avoiding the overhydrogenation of alkynes to alkanes. The results obtained for the different reactions with the different catalysts have shown that the support-metal interaction is essential when designing active catalysts for a particular reaction. This interaction strongly depends on the acid/base properties of the supports and on the pretreatments, and they must be selected for any reaction. Moreover, it has been proved that metallic sites evolve during the reaction leading to new species that can be more or less active, depending on the studied reaction.
López Hernández, I. (2021). Catalizadores metálicos estructurados en reacciones de Química Sostenible [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172246
TESIS
Ourari, Ali. "Étude de deux réactions d'électrocatalyse : hydrogénation électrocatalytique sur des films de polymères contenant des microparticules de métaux nobles et activation de l'oxygène par des complexes Mn(III) - bases de Schiff." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10171.
Full textAllam, Lévi. "Etude de la diffusion unidimensionnelle dans les chaines finies : application au tmmc-cd." Toulouse 3, 1987. http://www.theses.fr/1987TOU30063.
Full textPappas, Adlreburg Nickolas. "To Make Iron of Iron : A Comprehensive Analytical Study of Spade Shaped Iron Bars." Thesis, Stockholms universitet, Arkeologiska forskningslaboratoriet, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-145694.
Full textJones, Clive John. "Continuous leaching of a reduced manganese ore." Thesis, 2015. http://hdl.handle.net/10539/17469.
Full textPreston, Paula Cristina Canastra Ramos. "Physical and chemical characterization of the manganese ore bed at the Mamatwan mine, Kalahari manganese field." Thesis, 2009. http://hdl.handle.net/10210/1967.
Full textThe Mamatwan mine is situated at the most southern end of the world’s largest landbased resource of manganese, the Kalahari manganese field. The mine is operated by South African Manganese Corporation Limited (SAMANCOR) and is the largest open pit manganese mine in the world. The sedimentary manganese ore bed is interbedded with iron-formation of the Hotazel Formation of the Early Paleoproterozoic Voëlwater Subgroup of the Transvaal Supergroup. The open pit Mamatwan mine has a proven economic ore reserve of between 300 and 400Mt and produces 1.2Mt of manganese ore annually, of which 0.5Mt of ore is beneficiated and shipped through the harbour at Port Elizabeth. The remaining ore is railed to ferro-alloy plants at Meyerton and Newcastle. Carbonate-rich manganese lutite mined at the Mamatwan Mine is widely known as Mamatwan-type ore. It has a manganese content ranging from 30 – 38%. Only a small portion (15m of a total thickness of 49m) of the ore bed, containing an average of 38% Mn, is being mined and processed at present. The larger portion of the ore bed is not utilized. This study focuses on the physical and chemical characteristics of the ore bed in more detail in order to make suggestions on how to a) reduce waste by upgrading the upper parts of the lower manganese ore bed, or b) to improve the current recovery from the present economic zone. A second part of this study pays special attention to the lithostratigraphy of the lower manganese ore bed. The focus is on the paragenetic sequence and the diagenetic evolution of the braunite lutite that constitutes the manganese ore. The Mamatwan-type ore can be described as diagenetic to very low-grade metamorphic carbonate-bearing braunite manganolutite. Based on geochemical and mineralogical data, the lower manganese ore body was previously subdivided into eleven lithogically distinct zones. Based on detailed diamond drill core logging and with the aid of geochemical and physical data of two selected drill cores, an additional thirteen subzones were identified in this study. These new subzones were found to be consistent across the entire study area, located to the west and north of the present Mamatwan open pit. The paragenetic sequence recognised in the ore of the lower manganese ore bed can be subdivided into four stages, namely: (a) sedimentation, which is represented by fine lamination and the presence of fine-grained “dusty hematite”. (b) early diagenesis as represented by micritic carbonate matrix and possibly braunite, (c) late diagenesis or low-grade metamorphism are represented by coarse grained hausmannite, specularitic hematite, partridgeite and Mn-calcite, and supergene alteration that occurs immdediately below the contact of the ore bed to the unconformably overlying Tertiary Kalahari Formation. This supergene altered zone is marked by the presence of Mn4+ oxides such as cryptomelane, manjiroite, romanechite and pyrolusite, in addition to barite. The results obtained in this study permit definition of two sedimentary cycles within the manganese ore bed at the Mamatwan mine. Both cycles are defined by a carbonate-rich finely laminated zone at the base, overlain by a central manganese-rich economic zone, capped by manganese lutite that is enriched in carbonate ovoids. The two manganeserich zones are known as the M (lower) and X (upper) zone, and are characterized by the replacement of carbonate ovoids by hausmannite. The two Mn-rich zones are chemically and physically almost identical, with the M zone 7.5m thick and the X zone 5.5m thick. However, in the present mining configuration only the M zone is being mined. The most important result arising from the present study is the recommendation to restructure the future mining operation in order to mine not only the M zone, but also the X zone.
Burucu, E. "Kinetics and mechanism of the reduction of Mamatwan manganese ore fines by solid carbon." Thesis, 1991. http://hdl.handle.net/10539/22033.
Full textThe kinetics of reduction of the manganese ore from the Mamatwan mine has been studied by thermogravimetric (TGA) analysis, x-ray diffraction analysis (XRD), optical microscopy, and energy dispersive analysis of x-rays (EDAX) between 1100 and 1350 degree celcius with pure graphite under argon atmosphere. It has been observed that the rate and degree of reduction increased with increasing temperature and decreasing particle size. The effect of the different reaction atmosphere has also been investigated by replacing argon atmosphere with carbonmonoxide (CO) and carbondioxide (C02)' The results clarified importance of some reactions in the reduction mechanism of the ore. In early stages of reduction, up to about 4 minutes of reaction time, carbothermic reduction of higher oxides of manqanase and iron (Mn203 and Fe2o3) to manganeous oxide (MnO) and metallic iron respectively was observed which was controlled by diffusional process across the boundary layer between the solid phases. Apparent activation energy is calculated as 61.03 kJ for this stage which corresponds to about 30 percent reduction. Metallization started as random nucleation of iron rich carbides around Mno grains inside the particle. After 30 percent reduction the formation of a silicate phase was observed. Up to 70 percent reduction at 1350oC, reduction rate was controlled by chemical reaction between oxide phase and gaseous phase with an apparent. activation energy of 153 32 kJ.
MT2017
Burger, Albert Meiring. "Fault-controlled hydrothermal alteration of Palaeoproterozoic manganese ore in Wessels Mine, Kalahari Managanese Field." Thesis, 2014. http://hdl.handle.net/10210/9945.
Full text"Geochemistry and mineralogy of supergene altered manganese ore below the Kalahari unconformity in the Kalahari manganese field, Northern Cape Province, South Africa." Thesis, 2009. http://hdl.handle.net/10210/1958.
Full textIt is the focus of the study to qualitatively describe and then quantify the mineralogical and geochemical changes associated with the supergene alteration of carbonate-rich braunite lutite (Mamatwan-type ore) immediately below the Kalahari unconformity along the southeastern suboutcrop perimeter of the Hotazel Formation in the Kalahari deposit. It was also the objective of this study to determine the timing and duration of supergene alteration. Samples for polished thin sections were carefully selected from eight representative boreholes to be representative of all the lithostratigraphic zones and ore types. The thin sections were used to study mineralogy by means of reflected light microscopy and scanning electron microscopy. X-ray powder diffractometry on representative powder samples were used to study the mineralogy and geochemistry of the samples. Microprobe analyses were also performed on the representative samples. Finally the samples were submitted for 40Ar/39Ar geochronology. In this supergene enrichment zone carbonates are leached (associated with an increase in porosity) and Mn2+/Mn3+ -bearing minerals (kutnahorite, Mn-calcite an braunite) are altered to supergene Mn4+-bearing mineral phases (todorokite and manganomelane) and minor quartz. This process upgrades ore from 38 wt% Mn to ore with more than 40 wt% Mn. Element fluxes, enrichment and depletion of major and trace elements were quantified by mass balance calculations. Na2O, K2O, Sr, Ba, Zn and H2O were enriched, while Mn3O4, Fe2O3, CaO, MgO, P, B and CO2 were leached from the ore during supergene alteration. Results of this study suggest that the development of Post African I erosional surface may have taken place 45 Ma ago. The bottom of the weathering profile gives a well-defined peak at ca. 5 Ma that may possible coincide with the development of Post African II erosional surface. The major characteristics of the alteration process of the unaltered Mamatwan-type ore to supergene altered braunite lutite can be summarized as follow: • Leaching of Mn carbonates and Mn2+/Mn3+-oxides. • Formation of Mn4+-oxyhydroxides and quartz. • Decrease in relative density of the ore. • Increase in porosity of the ore. • Leaching of Mn3O4, Fe2O3, CaO, MgO, P, B, CO2. • Enrichment of Na2O, K2O, Sr, Ba, Zn, H2O. Chemical weathering processes along the Cenozoic Kalahari unconformity appear to have affected the manganiferous lithologies of the Hotazel Formation from 45 Ma onwards to 5 Ma. The weathering front processes very slowly through the Mn-rich braunite lutite (<10m in 40 Ma; <0.25m/Ma); producing a very uniform and microcrystalline supergene mineral assemblage with distinct characteristics.
Van, Staden Anelda. "Characterisation of the lowermost manganese ore bed of the Hotazel Formation, Gloria Mine, Northern Cape Province." Thesis, 2009. http://hdl.handle.net/10210/1975.
Full textThis dissertation describes the N1 manganese ore bed at Gloria Mine in the Kalahari Manganese Field, Northern Cape Province. It also compares the ore bed at Gloria Mine with the correlative bed further to the south at Mamatwan Mine. The ore bed at Gloria Mine can be subdivided into ten texturally distinct zones that are laterally consistent throughout the mine lease area. The mineralogy and geochemistry of the various lithostratigraphic zones are described from two drill cores (GL28 and GL24), situated away from any known structural features or unconformities that could have affected the properties of the Ore. The ore in drill core GL28 has a mineralogical composition similar to that of typical Mamatwan-type ore described at Mamatwan Mine with braunite and kutnahorite as the main minerals. However, in drill core GL24 the ore has a very different mineralogical composition although it is texturally and geochemically rather similar to Mamatwan-type ore. The ore is composed of hausmannite, calcite and jacobsite and is apparently related to a post-depositional alteration event that did not effect Mamatwan-type ore in the Mamatwan Mine area. This altered ore is similar in composition to low-grade leastaltered manganese ores in the cores of fault blocks at Wessels and N’Chwaning Mines i.e. the area known for its hydrothermally altered high-grade manganese ores in the northern part of the Kalahari Manganese Field. In addition to the above, the N1 manganese ore bed at Gloria Mine also underwent ferruginisation close to certain joints and normal faults. No obvious alteration could be detected where the ore bed is unconformably overlain by Dwyka diamictite, nor associated with a thrust fault displacing the ore.
(9673769), William E. Odom III. "Dating the Cenozoic incision history of the Tennessee and Shenandoah Rivers with cosmogenic nuclides and 40Ar/39Ar in manganese oxides." Thesis, 2020.
Find full textBhalla, Amit. "Hydrocarbon reduction of manganese ores." Thesis, 2018. https://hdl.handle.net/10539/25884.
Full textReduction behavior of South African Mamatwan manganese ore using methane-argon- hydrogen gas mixture was investigated experimentally in the temperature range of 1050ºC to 1250ºC. The effect of changing gas mixture composition, time and temperature was studied using a vertical tube furnace. After each test, three representative samples were prepared; one was analyzed by chemical analysis to obtain metallization results as a function of each reducing condition for each time interval over the total reduction period of two hours. Second sample was analyzed by X-ray diffraction to determine the progress of phase changes; the third sample was mounted, polished and submitted for SEM-EDAX in order to examine the morphology of the ore and its changes in the course of reduction. It was seen that CH4 was an effective reductant as it cracked, supplying the reaction site with hydrogen gas and very fine solid carbon. The excess carbon from cracking of methane ensures regeneration of reductants CO and H2 from reaction product gases of CO2 and H2O ensuring low partial pressure of oxygen at the reaction site. Hydrogen gas may also be involved in the reduction of iron oxide components of the ore. Moreover, depending upon temperature and CH4/H2 ratio in the gas phase the activity of carbon in the system reaches values much higher than unity, shifting the reduction reaction by carbon to lower temperatures. It was observed that bulk of the metallization occurred in the first thirty to forty minutes and the metallization reached some kind of a reduction maximum at 73% metallization. The Mn/Fe ratios in the resulting alloy were higher than those in ordinary carbothermic solid-state reduction, indicating the simultaneous reduction of Fe and Mn at these low reducing temperatures due to a low oxygen potential set up by the methane bearing gas mixtures. It was seen that metallization of Mamatwan ore proceed in two stages. First, reduction of the higher oxides to MnO and metallic iron. Second, reduction of any remaining oxides and MnO to mixed carbide of iron and manganese. During first stage values of effective CO-CO2 diffusivities generated by the model were found to lie in the range from 1.45 *10-6 cm2sec-1 to 8.43*10-6 cm2sec-1 at 1100ºC. Apparent activation energy for first stage calculated in the temperature range of 1050ºC to 1250ºC varied from 1.47 kJ/mol to 24.72 kJ/mol indicating possibility of diffusional control. For the second stage the experimental curves could be duplicated with the mathematical model reasonably well with a maximum difference between the experimental and predicted values being about 5 percent. Rate of metallization values during the second stage (Ms) changed between 1.83*10-8 mol.sec-1.cm-2 and 8.55*10-8 mol.sec-1.cm-2. Specific rate constant values (ks) for the second stage, varied from 5.53*10-6 cm/sec to 3.16*10-5 cm/sec which are much smaller than specific rate constant for the first stage of reduction (kf), which varied from 1.64*10-4 cm/sec to 1.15*10-4 cm/sec, as the rate of second stage of the reduction is much slower than the rate of the first stage. X ray analysis revealed that manganese ore was reduced primarily to carbide Mn7C3 at lower temperature range of the experiments, but at 1200ºC the dominant reaction product was Mn5C2 in both mixtures of methane-argon and methane-hydrogen. The S.E.M images revealed that the product metallic phase occurred all throughout the surface, with globular formation in case of reduction where hydrogen was the carrier gas.
MT 2018
Gutzmer, Jens. "Genesis and alteration of the Kalahari and Postmasburg manganese deposits, Griqualand West, South Africa." Thesis, 2012. http://hdl.handle.net/10210/5803.
Full textThe economically important sedimentary manganese deposits of the Paleoproterozoic Kalahari and Postmasburg manganese fields, are situated in close geographic vicinity to each other in the Griqualand West region of the Northern Cape Province, South Africa. This thesis describes aspects of mineralogy, petrography and geochemistry of the manganese ores with the purpose to establish genetic models for genesis and alteration of manganese ores of both manganese fields. The Kalahari manganese field, situated some 60 km northwest of Kuruman, is the largest known land-based manganese deposit. Manganese ores occur interbedded with iron-formations of the Hotazel Formation of the Voelwater Subgroup of the Late Archean-Paleoproterozoic Transvaal Supergroup. The sediments of the Voelwater Subgroup are preserved in five erosional relics, of which the Kalahari manganese deposit is by far the largest and the only one of economic importance. Two types of ore are mined, low-grade sedimentary Mamatwan-type ore and high-grade Wesselstype ore. Mamatwan-type ore is represented by microcrystalline laminated braunite-lutite composed of kutnahorite, Mn-calcite, braunite and hematite, modified by the occurrence of late diagenetic or metamorphic hausmannite, partridgeite, manganite and calcite. Mamatwan-type ore contains up to 38 mass % Mn and constitutes about 97 % of the ore reserves in the Kalahari manganese deposit. High-grade Wessels-type ore, with a manganese content of between 42 to 48 mass % Mn (on average), constitutes about 3 % of the ore reserves. It occurs only in the northwestern part of the main Kalahari deposit, and in small deposits at Hotazel and Langdon, in association with a system of north-south striking normal faults. The Wessels alteration event is thought to be related to the Kibaran orogenetic event (about 1.1 Ga). Fault zones are ferruginized and alongside faults sedimentary Mamatwan-type ore has been hydrothermally upgraded to Wessels-type ore. Metasomatic fronts are defined by changing mineral associations. These associations clearly illustrate that decreasing degrees of alteration relate to increasing distance from the fluid feeders. Areas of unaltered Mamatwan-type ore are preserved in the core of fault blocks. Wessels-type ore consists mostly of hausmannite, bixbyite, braunite II and manganite and subordinate gangue minerals such as clinochlore and andradite but the mineral assemblage associated with the Wessels alteration event is unusually diverse. More than 100 minerals have been identified, amongst them 8 new mineral species and an unusual, ferrimagnetic, Fe-rich variety of hausmannite. Mass balance calculations illustrate that the upgrading of the Wessels-type manganese ore is a consequence of leaching of CaO, MgO, CO 2, and Si02 from a low-grade Mamatwan-type precursor. This metasomatic process results in increasing secondary porosities, compaction of the orebody to two thirds of its original thickness and consequently residual enrichment of manganese in the ores. Three younger alteration events are observed in the Kalahari manganese deposit. These are only of minor economic importance. Wallrock alteration associated with the Mamatwan alteration event is characterized by reductive leaching of Fe and Mn around syntectonic veins and joints with pyritechalcopyrite- carbonate mineralization. The alteration is explained by infiltration of epithermal solutions that were introduced along veins or joints. The timing of the alteration event has tentatively been placed into the Pre-Karoo era. The Smartt alteration event is associated with intensive faulthosted brecciation and replacement of braunite and carbonates of the Mamatwan-type ore by todorokite and manganomelane, a process that causes considerable upgrading of the manganese ore next to a fault breccia at Mamatwan mine, and the formation of stratiform cross-fibre todorokite veins at Smartt mine. The Smartt alteration event postdates the Mamatwan alteration event and has tentatively been correlated with Pre-Kalahari groundwater circulation. Supergene alteration of the ores took place in Kalahari and Post-Kalahari times. It is characterized by the occurrence of cryptomelane, pyrolusite and other typically supergene manganese oxides along the suboutcrop of the Hotazel Formation beneath the Cenozoic Kalahari Formation. The Postmasburg manganese field is situated about 120 km to the south of the Kalahari manganese field on the Maremane dome. Two arcuate belts of deposits extend from Postmasburg in the south to Sishen in the north. Two major ore types are present. The ferruginous type of ore is composed mainly of braunite, partridgeite and bixbyite and occurs along the centre of the Gamagara Ridge, or Western belt. The siliceous type of ore consists of braunite, quartz and minor partridgeite and occurs in small deposits along the Klipfontein Hills (or Eastern belt) and the northern and southern extremities of the Gamagara Ridge. Geological and geochemical evidence suggest that the manganese ores represent weakly metamorphosed wad deposits that accumulated in karst depressions during a period of lateritic weathering and karstification in a supergene, terrestrial environment during the Late Paleoproterozoic. The dolomites of the Campbellrand Group of the Transvaal Supergroup are host and source for the wad accumulations. Contrasting geological settings are suggested for the accumulation of the siliceous and the ferruginous types of ore respectively. The former originated as small pods and lenses of wad in chert breccia that accumulated in a karst cave system capped by the hematitized Manganore iron-formation of the Transvaal Supergroup. The cave system finally collapsed and the hematitized iron-formation slumped into the sinkhole structures. The ferruginous type of ore accumulated as mixed wad-clay sediment trapped in surficial sinkhole depressions in the paleokarst surface. The orebodies are conformably overlain by the Doornfontein hematite pebble conglomerate or aluminous shales belonging to the Gamagara Formation of the Late Paleoproterozoic Olifantshoek Group. Well preserved karst laterite paleosol profiles, described from the basal section of the Gamagara Formation, provide a strong argument for the terrestrial, supergene origin of the manganese ores. The manganese ores in the Postmasburg manganese field were affected by diagenesis and lower greenschist facies metamorphism. Metamorphism resulted in recrystallization to braunite in the siliceous ores of the Eastern belt, and to massive or mosaic textured braunite and idioblastic partridgeite in the ferruginous environment of the Western belt. Secondary karstification and supergene weathering are evidence for renewed subaerial exposure of the manganese ore and their host rocks. The metamorphic mineral assemblage is replaced by abundant romanechite, lithiophorite and other supergene manganese oxides. Comparison between the Kalahari- and the Postmasburg manganese field shows that sedimentary manganese accumulation took place in entirely different depositional environments and owing to different mechanisms. Their close geographic relationship appears to be coincidental. Apparent similarities arise as a consequence of regional geological events that postdate the deposition of the manganese ores. These similarities include the lower greenschist facies metamorphic overprint, an event tentatively related to thrusting and crustal thickening during the Kheis orogenetic event, and syn- to Post-Kalahari supergene alteration. The correlation of structurally controlled hydrothermal alteration events in the Kalahari manganese field and the Postmasburg manganese field remains difficult due to the absence of the necessary geochronological constraints.
"Mineralogiese ondersoek van hoë-temperatuur-reduksieprodukte van mangaanerts vanuit die Mamatwanmyn, Kalaharimangaanveld." Thesis, 2015. http://hdl.handle.net/10210/14487.
Full textThis investigation is a mineralogical study of the reduction products formed during the reduction of Mamatwan manganese ore, as well as presentation of a possible reduction mechanism for this ore type. Cubes, 20 millimeter in dimensions, of Mamatwan manganese ore were reduced in a vertical tube resistance furnace at temperatures varying from 1200 to 1500°C with various reductants and retention times...
Van, Bart Adrian. "Structure, stratigraphy and sedimentology of the paleoproterozoic Nsuta manganese deposit, Ghana." Thesis, 2008. http://hdl.handle.net/10210/812.
Full textDr. J.M. Huizenga Prof. Nic Beukes Prof. J. Gutzmer
"A geometallurgical evaluation of the ores of the northern Kalahari manganese deposit, South Africa." Thesis, 2010. http://hdl.handle.net/10210/3223.
Full textThe Kalahari Manganese Deposit (KMD) is the largest of five erosional relics of the Hotazel Formation that are located near Kuruman in the Northern Cape Province of South Africa. Manganese ores are exploited from the lowermost of three manganiferous beds that are interbedded with banded iron-formation (BIF) and hematite lutite, that together constitute the Hotazel Formation. Two major ore types have been delineated previously, viz. low grade braunite lutite of the Mamatwan-type, and high grade oxidic ores of the Wessels-type, with the latter spatially restricted to the northern KMD. Genesis of the ores was temporally distinct, with the Mamatwan-type ore considered as a sedimentary-diagenetic precursor to the hydrothermally altered Wessels-type ore. Drill core samples from the Nchwaning-Gloria area of the northern KMD were analysed, with the aim to better characterise ore genesis, with emphasis on ore alteration. A second part of the study aimed at the application of mineralogical and geochemical information to aspects of ore smelting for the production of Mn alloy for use in the steel industry. Methods employed were drill core logging, X-ray diffraction (XRD), petrography, electron probe microanalysis (EPMA), major and trace element (including REE) analysis (employing artificial neural networks for evaluation of elemental trends), and stable isotope (C and O) analysis. Significant effort was invested in method development for quantitative mineralogical modal analysis using Rietveld refinement of XRD data. The study shows that a number of ore types can be differentiated in the northern KMD on the basis of mineral assemblage, grade, texture and geochemical characteristics. The ores are broadly classified into least altered (LA), partially altered (PA) and advanced altered (AA) types. The LA ores are low grade (<40 wt%Mn) Mn lutites, with dolomite-group carbonate a significant component in addition to braunite. Serpentine is a ubiquitous trace mineral, and boron is a characteristic trace element hosted predominantly by braunite in these ores. Ores of the PA type comprise either braunite-hausmannite-calcite or hausmannite-calcite assemblages, are fine to coarse grained, and display intermediate Mn grades (40-45 wt%Mn). They exhibit a transitional trace element signature. Advanced altered ores may be classified into five different types, based on mineral assemblages that contain hausmannite and/or braunite as significant minerals. Carbonates occur predominantly in the form of calcite, present in minor to trace proportions. Textures vary from fine to very coarse grained, and high Mn grades (typically >45 wt%Mn), are recorded. Trace elements of significance include Zn, associated with hausmannite, B, associated with massive braunite and a number of trace minerals, and P, typically present in trace quantities of apatite. In terms of ore genesis, mineralogical, geochemical and geological considerations suggest that Mn (and Fe) originated from submarine hydrothermal vents, from which it travelled in hydrothermal plumes, prior to rapid deposition ~2.2 Ga ago. Diagenesis followed soon after deposition, through redox reactions involving organic matter and higher oxides of Mn to produce the braunite-carbonate assemblage primarily observed in LA ores. The carbonate:oxide ratio and nature of the carbonates varied slightly depending on fluctuations in organic matter flux to the sediment, as well as marine bicarbonate concentrations. Metamorphism, in relation to diagenesis and metasomatism, is poorly understood, but is perceived to have resulted in serpentine formation, as observed in LA and PA ores.
Schutte, Sabine Silke. "Ongeluk volcanism in relation to the Kalahari manganese deposits." Thesis, 2011. http://hdl.handle.net/10210/4101.
Full textThe Ongeluk Formation is a laterally extensive sequence of ≈2200 Ma tholeiitic basaltic andesites in the upper Griqualand West Sequence of the northern Cape Province. The stratigraphic thickness is about 500 m and the Ongeluk Formation underlies the ore-bearing strata of the Kalahari Manganese Field. The formation comprises massive lavas, pillow lavas and hyaloclastite beds in close association. These rocks were extruded under water in a marginal basin within the continental setting of the Kaapvaal Craton. The Hekpoort Basalt Formation of the Transvaal is magmatically cogenetic with the Ongeluk, having indistinguishable geochemistry and sharing a stratigraphically related hiatus in Cr values. The best age estimate for the two formations is 2193 ± 71 Ma, from Rb-Sr data of two previous workers for Hekpoort samples. The Ongeluk Formation shows a mild "regional" geochemical alteration and a profound "Kalahari" alteration beneath the Kalahari Manganese Field. Geochemical screening was used to reconstruct the magmatic composition from a selected dataset. Three stages in the development of regional alteration are ascribed to sea water-rock interaction at different temperatures, and have distinct geochemical signatures. The pervasive Kalahari alteration is characterised by a purple colouration and the decoupled alteration of alkali and high field strength elements. It is due to the development of major hydrothermal systems close to a volcanic vent which are analogous to modern mid-ocean ridge systems. A multi-system isotopic study showed that most of the isotope systems were modified by sea-floor alteration. The similarity of the 2237 ± 23 Ma Pb-Pb errorchron age with the Rb-Sr Hekpoort age reflects changes in U-Pb ratios with minor changes in Pb isotope ratio. Evidence was found in the Rb-Sr system for a minor disturbance at ≈ 1100 Ma, also reported by previous workers. This event is related to the Namaqua tectogenesis, while no isotopic evidence was found for the enigmatic ≈ 2200 to 1750 Ma Kheis orogeny, regarded as the cause of thrust faulting in the region. A genetic connection between the Ongeluk lava and the Kalahari Manganese deposits was established. The manganese ores contain evidence for both marine and hydrothermal contributions to chemical sedimentation. Negative Ce anomalies characterise an oxygenated sea in which the interaction between global oceanic and continental influences is seen. Heavy rare earth enrichment reflects volcanic hydrothermal exhalations from the Kalahari Ongeluk system. Mass balance calculations show that the entire 9 billion tons of Kalahari Manganese ore could have been derived from the Ongeluk Formation. A new model describing the origin and evolution of the Kalahari Manganese Field places a strong emphasis on the role of the syngenetic hydrothermal exhalation and upgrading.
"Genesis and characteristics of the Wolhaarkop breccia and associated manganore iron formation." Thesis, 2009. http://hdl.handle.net/10210/1970.
Full textHematized iron formation known as the Manganore iron formation is slumped into sinkhole structures in the Campbellrand Subgroup, Transvaal Supergroup, on the Maremane dome. These iron deposits are underlain by manganiferous breccias known as the Wolhaarkop Breccia. Known iron and manganese deposits of this type occur in an arc from Sishen in the north to Postmasburg in the south. The area is not being mined for manganese at the moment due to the relatively high grade of the Kalahari manganese field situated to the north of this area. The iron deposits, though, are some of the richest in the world. The aim is to establish the mode of origin for the Wolhaarkop Breccia. The Wolhaarkop Breccia is interpreted as being a residual ancient manganese wad from a karst environment in manganese rich dolostones of the Campbellrand Subgroup. This siliceous breccia contains authigenic megaquartz and angular poorly sorted clasts of chalcedony and quartz, set in a braunite-hematite matrix. Fluid inclusions in the authigenic quartz of the Wolhaarkop Breccia have been studied to establish the source of the fluid responsible for quartz precipitation in the Wolhaarkop Breccia, and indirectly, for the formation of the Wolhaarkop Breccia. Thermometric data was used to determine the maximum possible pT and depth conditions under which the quartz might have been precipitated. Fluid chemistry was determined using the bulk crush-leach method to shed some light on the fluid origin. It was established that the fluid responsible for chert recrystallization and precipitation of authigenic quartz and chalcedony had a meteoric source. Considering the results of the above-mentioned analysis, it was concluded that the iron and manganese deposits were formed during a cycle of uplift followed by subsidence. During the period of uplift, erosion in a karst environment and enrichment of iron formation in a supergene environment concentrated manganese as a manganese wad, and iron as a residual iron-oxide laterite. Meteoric water was the main fluid present during this period. Later, during a stage of subsidence, the Wolhaarkop Breccia underwent diagenesis and later lower greenschist-facies metamorphism. During a final stage of uplift the deposit was exposed to the atmosphere again, the dolostones were weathered away and the residual Manganore iron formation and Wolhaarkop Breccia were exposed to supergene alteration.
Channon, Walter Patrick. "The reduction of fluxed and non-fluxed manganese ores by ferromanganese-silicide." Thesis, 2014. http://hdl.handle.net/10539/15969.
Full textMedium- and low- carbon ferromanganese are produced by the silicotherm ic redixction of slags containing MnO, Because of its importance in the production of refined ferromanganese, the reaction between a premelted Mamatwan manganese ore and various ferromanganese «silicide reducing alloys has been studied with and without additions of fluxing agents. This relatively low grade manganese ore is partially self-fluxing and it is necessary to optimize the amounts and timing of fluxing additions during the production of refined ferromanganese to ensure both efficient electric furnace operation and manganese extraction from the premelt. Therefore, throughout the laboratory investigation, emphasis has been placed on the implications for industrial practice, Alloys containing different silicon concentrations were added to a premelted sample of Mamatwan ore before the sample was introduced into a molybdenum-wound resistance furnace,. The reaction was carried out under an argon atmosphere and the parameters varied were reaction time reaction temperature, alIoy~to*ore ratio, fluxing additions and the silicon contents of the reducing alloy. The effect of stirring of the reacting melt was also examined. The highly exothermic nature of the reactions involved in this investigation constituted a m ajor obstacle to any attempt to maintain close control of temperature in the system. This also adversely affected the possibilities of carrying out controlled equilibrium and kinetic studies in this slag-m etal system* Because of the highly exothermic reaction, temperature appeared to have little effect on the rates of manganese transfer to the metal and silicon transfer to the slag and an apparent equilibrium was rapidly approached, Limits were determined for the favourable effects of fluxing additions and manganese recoveries declined as the CaQ"to~MgO ratio decreased for any percentage of basic flux additions, As the silicon content of the alloy was progressively increased, the recovery of manganese i passed through a maximum and subsequently decreased, Similar results ■were obtained with variations in the a lloy-to-ore ratio/ When aluminium was used as a reducing agent together with silicon, substantial increases in manganese recovery were achieved because the aluminoi >- „ , ,o « resection displaced the apparent equilibrium. The s.ilicor • ’»■* . . of the resulting alloy was above the specifications for refine ' : cioo .anganese. Stirring of the reacting melts decreased the manganese . .-tcovery and this result conflicts with the results of a previous investigation but may be explained by theexotherrnic nature of the silicon reduction reaction. The results obtained when used in conjunction with other physicochem ical data related to this slag^metal system suggest optimum slag compositions fo r m ore efficient manufacture of m edium- and low -carbon ferromanganese ■fom vlamatwan ore, -
Chisonga, Benny Chanda. "Metasedimentary manganese ores of the Serra do Navio deposit, Amapa Province, Brazil." Thesis, 2009. http://hdl.handle.net/10210/1952.
Full textHou, Baohong. "Geology and genesis of Dounan manganese deposits, Yunnan Province, P. R. China / Baohong Hou." 1993. http://hdl.handle.net/2440/21425.
Full textxix, 288, [36] leaves, [15] leaves of plates : ill. (some col.), maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This study examines the medium sized sedimentary manganese deposit of Dounan, Yunnan Province of China, to determine the sedimentary environments controlling the distribution of ores and rocks, and to establish the relationships between ore mineralization and changes in the sedimentary environment. The thesis also aims to work out the sequence of events after the primary ore is formed, to determine which processes lead to secondary enrichment of the ore.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1994
Huq, Mohammad Mahmudul, and 馬皓翔. "One-step electrophoretic fabrication of graphene and carbon nanotube-based scaffold for manganese-based pseudocapacitors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/77904412234324024871.
Full text元智大學
化學工程與材料科學學系
104
This study develops an one-step method of electrophoretic deposition (EPD) of carbon nanotubes (CNTs) and graphene nanosheets (GNs) as a scaffold for manganese-based pseudocapacitors. In this study, two different scaffolds for manganese deposition were fabricated: one having 2D GNs and another with 3D GN/CNT nano-porous structure (designated as GN-Mn and GN-CNT-Mn respectively). Manganese was deposited in-situ during the EPD fabrication process. For comparison one 3D nanoporous electrode was made without any Mn deposition by the same method. The microstructure and morphology of as-prepared electrodes were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction spectroscopy was carried out in order to evaluate the crystalline nature of the electrodes. The amount of carbon materials (GNs and CNTs) in the electrodes was estimated by thermogravimetric analysis (TGA). The capacitive performance of the electrodes was examined by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) cycle and electrochemical impedance spectroscopy (EIS) in 1 M Na2SO4 electrolyte, using a three electrode system with platinum wire and Ag/AgCl electrode as counter electrode and reference electrode, respectively. In order to evaluate the cyclic stability of the GN-CNT-Mn electrode CV test for 2000 cycles was carried out, achieving 95% of capacitance retention, clearly showing the capability of EPD method to fabricate GN/CNT based scaffold for Mn-based electrode. A gravimetric capacitance of 240 F g-1 was achieved for GN-CNT-Mn electrode at a current density of 0.5 A g-1, calculated from GCD curve. The areal capacitance of the electrode was calculated as 200 mF cm-2 at the same current density. The excellent capacitive performance of GN-CNT-Mn can be ascribed to the unique three dimensional structure created by CNTs and GNs that facilitates more accessible electroactive area. The weight loading and the thickness of the electrode was precisely controlled by tuning the EPD deposition time. As the weight loading of the as prepared electrode was increased the gravimetric capacitance decreased significantly, proving existence of dead zones, the area inaccessible to electrolytes in the electrode structure. On the other hand areal capacitance was found to be an increasing function of the weight loading. At a relatively low weight loading of 0.31 mg cm-2 the gravimetric capacitance was 407 F g-1 at a current density of 0.1 A g-1. Conversely the areal capacitance rose to 350 mF cm-2 at a weight loading of 1.88 mg cm-2 at 0.1 A g-1. Overall, the study suggests that EPD method is precisely tunable, which is very important in industrial applications. Keywords: Supercapacitor; Electrophoretic deposition; Manganese oxides; Graphene sheets; Carbon nanotube; Areal capacitance
Ahamed, Mohamed Muzamil. "Mode of occurrence, mineralogy, textures palynology and origin of manganese ores of North Kanara District, Karnataka." Thesis, 1991. http://hdl.handle.net/2009/2716.
Full text"Luminescence studies of one-dimensional manganese salts and d(8)-d(8), d(8)-d(6) dimeric complexes." Tulane University, 1990.
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