Dissertations / Theses on the topic 'Laterita'

Ni-bearing Mg-phyllosilicates (commonly known as garnierites) are significant ore minerals in many Ni-laterite deposits worldwide. However, the characterisation of these mineral phases is complex, as well as their classification and nomenclature, due to their fine-grained nature, low crystallinity and frequent occurrence as mixtures. The aim of this study is to shed some light to the nature of the Ni-bearing Mg-phyllosilicates occurring at the Falcondo Ni-laterite. In this deposit, these minerals are found within the saprolite horizon mainly as fracture-fillings, coatings on joints and as breccias. The Falcondo garnierites display easily distinguishable different shades of green and characteristic textures, which correspond to different mineral phases. Five garnierite types were defined by X-ray diffraction (XRD), optical and electron microscopy, and electron microprobe (EMP) analyses: I) Ni-Fe-bearing serpentine-like, II) Ni-(Al)-bearing serpentine-like with minor talc-like, III) Ni-rich mixture of serpentine- and talc-like, IV) talc-like and V) sepiolite-falcondoite. The characterisation was completed with differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), Raman spectroscopy, microfocus X-ray absorption spectroscopy (i.tXAS) and dissolution experiments, in order to gain further insight on these mineral phases from different points of view. EMP oxide totals and DTA-TG indicate that talc-like contain higher H2O than talc sensu stricto (about 4.5% mass loss at 200°C, and up to 5% at 650°C), and therefore the names kerolite-pimelite [(Mg,Ni)3Si4010(OH)2• nH20] should be used instead of talc-willemseite [(Mg,1•103Si401o(OH)21. Compositional data showed continuous Mg-Ni solid solution along the joins lizardite-nepouite/chrysotile-pecoraite (serpentine-like), kerolite-pimelite (talc-like) and sepiolite-falcondoite. The phases with larger amounts of talc-like displayed the highest Ni contents (up to 2.2 apfu out of 3 octahedral atoms). In addition, EMP analyses of the mixed phases showed deviations from the stoichiometric Mg-Ni solid solutions of serpentine and talc. This is best explained by mixing at the nanoscale, which was confirmed by XRD and high resolution TEM imaging. Furthermore, a detailed textural study by means of EMP quantified X-ray element imaging was used to explain the relationships between textural position, sequence of crystallization and mineral composition of the studied Ni-phyllosilicates. These results indicate several stages of growth with variable Ni content, pointing to recurrent changes in the physical-chemical conditions during the precipitation of the different Ni-phyllosilicates. HRTEM and low magnification imaging enabled to measure the characteristic basal spacings of these phyllosilicates and to observe a wide variety of nanotextures, respectively: 15-sectored polygonal serpentine, chrysotile tubes, lizardite lamellae, kerolite-pimelite lamellae and sepiolite ribbons. In accordance with EMP results, chemical analyses by TEM showed that Ni is more concentrated in the kerolite-pimelite lamellae than in the serpentine particles. In addition, the HRTEM revealed that kerolite-pimelite lamellae replace the Ni-poor serpentine particles. These observations evidence the processes of progressive Ni-enrichment within some Ni-bearing Mg-phyllosilicates. Characteristic Raman bands were observed for serpentine-, talc- and sepiolite-like phases, and therefore this technique allowed discriminating the different garnierite types. The synchtrotron radiation-based µXAS analyses were conducted to investigate the speciation of Fe (by Fe K-edge X-ray absorption near edge structure, XANES) and the local environment of Ni (by Ni K-edge extended X-ray absorption fine structure, EXAFS). The XANES results indicate that Fe in the weathered saprolite and in the garnierites is mostly oxidised, whereas in the primary serpentine from the ultramafic protolith it is in the ferrous form. The EXAFS spectra indicate that Ni is homogeneously distributed in the unweathered rock, and is accumulated in discrete domains (clusters) in the weathered saprolite and in all the garnierite types. Finally, the dissolution experiments of a set of garnierites which cover a wide range of mineral compositions at acidic pH suggest that the dissolution rates are faster in serpentine- dominated garnierites than in talc (kerolite)-dominated garnierites or sepiolite-falcondoite, and that the dissolution is not congruent, being the serpentine component the first to dissolve in the garnierite mixtures of serpentine and talc (kerolite). In summary, the various analytical techniques applied to the garnierites of this study provide an accurate outlook of their complex mineralogy, structures, textures and chemistry at different scales that provides further details on the formation of these Ni-bearing Mg- phyllosilicates in a lateritic environment.
Els fil- losilicats de níquel (comunament anomenats "garnierites") són importants menes en molts jaciments laterítics de Ni del món. La seva caracterització, classificació i nomenclatura és complexa, ja que normalment es troben en forma de mescles íntimes de diferents fil- losilicats de gra molt fi i baixa cristal• linitat. L'objectiu d' aquesta tesi és avançar en el coneixement de la mineralogia dels fil- losilicats de Ni del dipòsit de laterites niquelíferes de Falcondo, a la República Dominicana, per mitjà de l'ús d'un ampli espectre de tècniques analítiques: difracció de pols de raig X, anàlisi tèrmica diferencial i termogravimetria, microscòpia òptica, microscòpia electrònica de rastreig, microsonda electrònica, microscòpia electrònica de transmissió, espectroscòpia Raman, espectroscòpia d' absorció de raigs X (EXAFS i XANES, amb radiació sincrotró) i per mitjà d'experiments de dissolució. Les garnierites de Falcondo es localitzen a la part baixa de l'horitzó saprolftic en forma de rebliment de fractures i vetes, i ciments i clasts en bretxes. Els principals resultats indiquen que hi ha cinc tipus de garnierites, segons el seu color, la seva mineralogia i la química mineral. La majoria són barreges de serpentina i talc hidratat (kerolita-pimelita), tot i que també hi ha fases de la sèrie sepiolita-falcondoita. La fase que concentra més Ni és la kerolita-pimelita, mentre que a la serpentina el Ni és sistemàticament molt baix i a la sepiolita-falcondoita és molt variable. Les imatges d' alta resolució obtingudes amb microscopi electrònic de transmissió indiquen que els fil- losilicats que componen les garnierites formen una gran varietat de textures: serpentina poligonal, tubs de crisòtil, lamel• les de lizardita, lamel• les de talc hidratat i cintes de sepiolita. A més, s'ha observat que la kerolita-pimelita (rica en Ni) reemplaça sistemàticament la serpentina (pobra en Ni). L'espectroscòpia Raman permet distingir els cinc tipus descrits de garnierites i per tant, s'ofereix com una tècnica ràpida, senzilla i no destructiva per analitzar aquest tipus de minerals al camp. L' absorció de raigs X per mitjà de radiació sincrotró ha permès identificar que tot el Fe contingut en les garnierites i en les serpentines de la saprolita està en forma de Fe3+, i que tot el Ni es troba acumulat formant clusters, i no pas en forma de solució sòlida homogènia, a la capa octaèdrica. Finalment, els experiments de dissolució suggereixen que les velocitats de dissolució són més ràpides en les garnierites que contenen molta serpentina, i que la dissolució no és congruent, sent el Mg el primer element en ser posat en solució, seguit del Si i del Ni.

Geólogo
Los suelos lateríticos son una de las fuetes de metales críticos (EGP y Au) y otros metales de interés económico como el Fe, Ni o Cr. En el caso de Chile, la existencia de estos suelos se ha reportado en la Cordillera de la Costa del centro sur del país, en particular en la localidad de Camán. En este trabajo de Título se investigan los procesos de formación de este suelo, la movilidad y redistribución de elementos durante el proceso de formación de la laterita, poniendo énfasis en los elementos del grupo del platino y el Au. Se determinó que este perfil está compuesto por un horizonte saprolítico inferior empobrecido en metales y un horizonte limonítico superior enriquecido en Ni, Fe, Cr EGP y Au. Los principales agentes participantes en la redistribución de elementos durante el proceso de laterización son la presencia de fronteras de pH y Eh, ligantes que transportan los elementos en solución (clorurados y orgánicos principalmente) y condiciones aptas para la deposición de nuevas fases minerales, como cambios en la oxidación o presencia de minerales con alta capacidad de adsorción de elementos, como las arcillas o los óxidos e hidróxidos de Fe. Finalmente, el estudio de las características del agua del sector sugiere que agua con características similares a la presente hoy en día en las inmediaciones del perfil pudo ser la responsable de la formación de la laterita. El modelado numérico de la interacción agua-roca indica que el agua de Camán tiene una alta capacidad de disolución de aquellos minerales que forman la roca y se encuentra además saturada con respecto a los minerales que conforman la laterita.
Este trabajo ha sido financiado por proyecto Fondecyt Iniciación # 11140005 "Decoding precious metals (platinum-group elements and gold) in upper mantle rocks of the Chilean Coastal Cordillera"

Magíster en Minería
Las lateritas niquelíferas son una fuente generadora de la materia prima del acero inoxidable, el níquel. Dicho elemento se encuentra presente en diferentes tipos de rocas que son formadas por procesos externos que alteran, meteorizan y por último transforman la roca madre del depósito. La presencia de diferentes tipos de rocas, desde el punto de vista físico, químico, mecánico y, por último, de su contenido en mineralización en porcentajes (%) de níquel, hierro, magnesio, sílice, alúmina, entre otros, sugiere que cada tipo de roca debe estudiarse en forma propia. Cada perfil de meteorización o dominio geológico, conformado por diferentes tipos de rocas, tiene un comportamiento geoespacial diferente debido al proceso geológico de formación y enriquecimiento del depósito. Surge entonces la pregunta de cómo diseñar una metodología para muestrear el perfil de meteorización para la optimización de la malla de muestreo a corto plazo, partiendo del muestreo realizado en exploración, para generar el respectivo modelo de recurso. La metodología que se propone para determinar la malla de muestreo a corto plazo en lateritas niquelíferas, es la siguiente: análisis exploratorio y variográfico de datos espaciales, seguido de la construcción de múltiples escenarios mediante simulación Gaussiana secuencial y, a partir de los escenarios obtenidos, categorización de los recursos en cada dominio geológico usando gráficos tonelaje-ley sobre una ley de corte vs coeficiente de variación condicional (CCV). Lo anterior se aplica a varias mallas de muestreo tentativas para cada dominio geológico y permite estudiar y analizar la relación CBNT (relación costo/benefico, número-tiempo de muestras preparadas-analizadas en el laboratorio, tiempo en perforar cada dominio con su respectiva malla propuesta) para determinar la malla óptima de corto plazo en cada dominio. Se ilustra la propuesta con un caso de estudio de una zona particular de una laterita niquelífera subdividida en tres dominios geológicos que cubren todo el perfil de meteorización.

Orientadores: Francisco Sergio Bernardes Ladeira, Fabiano Tomazini da Conceição
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências
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Resumo: A teoria de pediplanação proposta por King em 1956 ganhou atenção no Brasil a partir da sua publicação sobre a evolução do relevo da porção oriental brasileira. Este trabalho de King suscitou críticas e reflexões da comunidade geomorfológica nacional. Além de King, muitos autores publicaram trabalhos com este enfoque, podendo-se destacar Moraes Rego (1932), De Martonne (1943), Freitas (1951), Almeida (1964), Bigarella e Ab¿Sáber (1964), Barbosa (1965), Bigarella e Andrade (1965), Braun (1971), entre outros. Apesar de uma certa estagnação após a década de 1980, a temática "paleosuperfícies" ganhou destaque nas últimas duas décadas, principalmente devido ao surgimento de novos métodos de análise, inclusive a possibilidade de datações absolutas em perfis de intemperismo. Este trabalho busca associar os perfis lateríticos de ferro aos patamares altimétricos, tratando os perfis lateríticos como marco cronoestratigráfico passível de datação, através de análises químicas, mineralógicas, macromorfológicas e de datação por (U-Th)/He dos perfis lateríticos de ferro. Duas áreas principais foram estudadas mais a fundo: o quadrante leste do Quadrilátero Ferrífero (região de Catas Altas), nas imediações da Serra do Caraça, apresentando uma superfície laterítica de ferro a 890m de altitude, com 10 Km de extensão, sob a Formação Fonseca, na qual foi amostrado um perfil laterítico de ferro; e o quadrante oeste do Quadrilátero Ferrífero, a região da Serra do Rola Moça e norte da Serra da Moeda, onde foi também amostrado um perfil laterítico de ferro, a 1400m de altitude aproximadamente, sob o itabirito in situ (na Serra do Rola Moça). Nestas áreas foram mapeadas a superfície laterítica de ferro e realizada analise geoquímica, mineralógica e de datação (U-Th)/He dos perfis lateríticos amostrados. As idades encontradas variam no perfil da região de Catas Altas de 33,09±1,11Ma a 0,71±0,05Ma e no perfil da Serra do Rola Moça de 6,08±0,20Ma a 0,43±0,04Ma. Os dados apontam que a superfície laterítica de ferro teve o início da sua elaboração a 33Ma atrás na região de Catas Altas, sendo que a goethita desde este momento vem dissolvendo e recristalizando, por isso as idades mais recentes. Portanto, a área do Quadrilátero Ferrífero estava exposta há 60Ma, isso significa que a configuração do relevo com os topos eram os mesmos há 60Ma, principalmente em se tratando da região da Serra do Caraça. Os materiais datados na Serra do Rola Mola vão ao encontro das idades elencadas para as áreas vizinhas, como é o caso da Mina do Capão Xavier na Serra da Moeda (em torno de 6 a 8 Ma). Por fim, na análise de paleosuperfícies não se pode associar os patamares altimétricos a antigas superfícies de aplainamento de forma direta. De acordo com o estudo regional no Quadrilátero Ferrífero, pode-se afirmar que independente dos patamates altimétricos o que prevalece na paisagem é a superfície Sul-Americana e não encontrou-se evidências seguras da Superfície Gondwana, mais antiga
Abstract: The theory of pediplanation proposed by King em 1956 has gained attention in Brazil since his publication about the evolution of the relief of the Brazilian eastern portion. This King's work has given rise to reviews and reflections from the national geomorphological community. Besides King, many authors have published with this approach, highlighting Moraes Rego (1932), De Martonne (1943), Freitas (1951), Almeida (1964), Bigarella and Ab¿Sáber (1964), Barbosa (1965), Bigarella and Andrade (1965), Braun (1971), among others. In spite of a certain stagnation after the decade of 1980, the theme "paleosurfaces" has been highlighted in the last two decades, mainly due to the uprising of new methods of analysis, including the possibility of absolute dating in intemperism profiles. This work aims to associate the iron laterite profiles with elevation levels by using laterite profiles as a chronostratigraphic mark possible to be dated, through chemical, mineralogical, macromorphological analysis and dating by (U-Th)/He of the laterite iron profiles. Two main areas have been studied deeper: the eastern quadrant of Quadrilátero Ferrífero (Catas Altas region), next to Serra do Caraça, showing a laterite iron profile at 890m of altitude, with 10km of extension, under Fonseca Formation, in which a laterite iron profile was sampled; and the western quadrant of Quadrilátero Ferrífero, Serra do Rola Moça region and northern Serra da Moeda, where a laterite iron profile was also sampled, at about 1400m of altitude, under the itabirite in situ (in Serra do Rola Moça). In these areas the iron laterite surface was mapped and the geochemical, mineralogical analysis and dating (U-Th)/He of the sampled laterite profiles was done. The ages found range in the Catas Altas region from 33,09±1,11Myr ago to 0,71±0,05Myr ago and in the profile of Serra do Rola Moça from 6,08±0,20 Myr ago to 0,43±0,04 Myr ago. The data show that the laterite iron surface began its forming 33Myr ago in Catas Altas region, regarding that from this moment goethite has been dissolving and recrystallizing, then, the more recent ages. Thus, Quadrilátero Ferrífero area was exposed 60Myr ago, this means that the configuration of the relief with the tops was the same 60Myr ago, especially being the Serra do Caraça region. The material dated in Serra do Rola Moça meet the ages listed for the neighboring areas, as Mina do Capão Xavier in Serra da Moeda (about 6 to 8 Myr ago). Finally, in paleosurface analysis altitude levels cannot be associated with former flattening surfaces in a direct way. According to the regional study in Quadrilátero Ferrífero, we can state that independently of the altitude levels, what prevails in the landscape is the Sul-Americana surface and we did not find secure evidence of the Gondwana surface, older
Doutorado
Análise Ambiental e Dinâmica Territorial
Doutora em Geografia

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Sulfides exposition to atmosphere promotes its oxidation resulting in acid drainage and mobilization of heavy metals and metalloids in water. Arsenic (As) mobilization can be a serious problem due to anthropogenic activities in the presence of sulfide minerals such as arsenopyrite (FeAsS). The use of limestone gravel is a common practice to neutralize the acid drainage. In this process, mobilization of metals and metaloids is decreased by precipitation, co-precipitation or adsorption onto recently precipitated Fe oxides. In this work, the efficiency of limestone filters for As remotion from water and neutralization of acid drainage was evaluated under field conditions. Arsenic stability in sediments next to a gold exploitation area was evaluated by sequential extraction chemical analyzes. The efficiency of horizontal filters prototypes, containing soil materials combined with limestone, for acidity neutralization and As remotion from acid solutions, was also evaluated in laboratory. Water and sediment samples were collected from creeks in area close to a gold mineralization. Water samples were collected during wet and dry seasons, while sediments were collected only during the wet season. Measurements of pH, Eh, electric conductivity (EC), dissolved oxygen and temperature were registered immediately after water sampling and As concentrations were determined in laboratory. In sediment samples, it was determined texture, particle density, remaining As, organic carbon (OC); As, Al, Ca, Mg and P contents extracted by Mehlich-3, pH in water, potential acidity, As sequential extractions and total contents of As and Fe. In order to evaluate the prototypes, in laboratory, acid solutionswith approximately 58 mg L-1 As were applied throughout PVC modules filled with Laterite (LAT), an Oxisoil (SOLO), a 3:1 mixture of SOLO and organic waste (SOLO+RO), and with limestone gravel (BRITA). Twelve filtration cycles, totalizing applications of 6.2, 67.21, 99.74, 20.22, 10.13 g As, Fe, S, Mg and Ca per filter, respectively, were performed. The residence time of the solution in the filters, as well as pH, CE, acidity and As, Fe, S, Mg and Ca contents in the input and output solutions were monitored. In the field, contents of As in water samples were low, except in two points which presented values above 100 ug L-1. There was not a consistent behavior for As in water samples respective to the collection time, but it could be observed a trend to decrease As concentrations during dry season. In general, As content in sediments was related to the organic matter content. It was observed that sediments and limestone filters play an important role in As mobility in water streams affected by acid drainage. Arsenic was mainly associated to stable fractions of the sediments, with a mean of 58% of the As linked to Fe oxides and residual fractions, which present practically null mobility. In the laboratory, prototypes of limestone gravel filters removed approximately 26 and 23% of the As and Fe applied, respectively. There was no significant sulfate removing or pH alteration in the filtered solutions for all prototypes. However, significant levels of the total acidity neutralization were observed, directly related to the residence time. Prototypes with SOLO+RO presented the highest residence times. The use of soil containing filters associated to limestone filters removed 2.6 and 2.45 times the As and Fe, respectively, removed by the limestone filter. The prototype LAT/BRITA/SOLO presented highest As removal capacity, around 70% of the applied As, and the highest As removal rate, by 1.2 mg min-¹, among soil containing filters. However, the residence time was higher to the filters containing soil materials than to the limestone filters. This can be a disadvantage to the use of soil filters. Notwithstanding, the use of soil materials combined with limestone can be an important strategy to increase the safety of the systems for As removal and acid drainage neutralization during rainy season.
A exposição dos sulfetos ao ar atmosférico promove a sua oxidação, o que pode resultar na acidificação de águas de drenagem e a mobilização de metais pesados e de metalóides. A mobilização de arsênio (As) pode ser um sério problema decorrente de atividades antropogênicas, na presença de minerais sulfetados, como a arsenopirita (FeAsS). O uso de britas de calcário é uma prática bastante utilizada para neutralizar a drenagem ácida. Neste processo ocorre a limitação da mobilização de metais por precipitação, co-precipitação e adsorção em óxidos de Fe recentemente precipitados. O presente trabalho avaliou a eficiência de filtros de brita calcária na remoção de As; e a neutralização da drenagem ácida, em condições de campo. Também foi avaliada a estabilidade do As em sedimentos próximos a área de exploração de ouro, por meio análises químicas de extrações seqüenciais. Paralelamente, foi avaliada a eficiência de protótipos de filtros horizontais contendo materiais de solo em conjunto com filtros de brita calcária na neutralização da acidez e remoção de As de solução ácida, em laboratório. Em condições de campo, foram coletadas amostras de água e de sedimentos em córregos de áreas próximas a mineralização de ouro. As amostras de água foram coletadas nos períodos chuvoso e seco, ao passo que os sedimentos foram coletados apenas no período chuvoso. Foram determinados pH, Eh, condutividade elétrica (CE), oxigênio dissolvido e temperatura das amostras de água, imediatamente após a coleta e em laboratório foram determinadas as concentrações de As . Nos sedimentos foram determinados a textura, a densidade de partícula, o pH em água, a acidez potencial, o As-remanescente, o carbono orgânico (CO), os teores de As, Al, Ca, Mg e P extraídos por Mehlich-3, extrações seqüenciais de As, e os teores totais de As e Fe. Para avaliação dos protótipos, em laboratório, foram aplicadas soluções ácidas com aproximadamente 58 mg.L-1 de As através de módulos de PVC preenchidos com laterita (LAT), com Latossolo Vermelho-Amarelo (SOLO), com uma mistura do SOLO e um resíduo orgânico, na proporção 3:1 (SOLO+RO), e com brita calcária (BRITA). Foram realizados 12 ciclos de filtração, totalizando uma aplicação de 6,2; 67,2; 99,7; 20,2; 10,1 g de As, Fe, S, Mg e Ca por filtro, respectivamente. Foram monitorados o tempo de residência da solução nos filtros e os valores de pH, CE, acidez e teores de As, Fe, S, Mg e Ca nas soluções de entrada e saída dos filtros. Em condições de campo, as concentrações de As nas águas foram baixas, com exceção de dois pontos que apresentaram valores acima de 100 ug L-¹. Não se observou um comportamento consistente do As nas águas em relação às épocas de coleta, mas houve uma tendência de diminuição nas concentrações de As no período seco. De modo geral,o teor de As nos sedimentos apresentou certa relação com o teor de matéria orgânica. Verificou-se que os sedimentos e os filtros de brita calcária desempenham importante função no controle da mobilidade do As em cursos d água afetados por drenagem ácida. Nos sedimentos, o As está associado a frações mais estáveis, em média 58 % do total ligado a óxidos de Fe e à fração residual, de mobilidade praticamente nula. Em laboratório, os protótipos dos filtros de brita calcária retiveram aproximadamente 26 e 23 % do As e Fe aplicados, respectivamente. Não houve remoção significativa de sulfatos ou alteração significativa do pH nas soluções filtradas para todos os protótipos de filtros. No entanto, foram observados níveis significativos de neutralização da acidez total na solução filtrada, diretamente relacionados com os tempos de residência. Os protótipos com SOLO+RO apresentaram os maiores tempos de residência. O uso de filtros contendo solo associados a filtros de brita calcária promoveu retenções de até 2,6 e 2,45 vezes mais As e Fe, respectivamente, em relação aos filtros de brita apenas. O protótipo de composição LAT/BRITA/SOLO apresentou maior capacidade de remoção, cerca de 70 % do As aplicado, e maior taxa de remoção de As, cerca de 1,2 mg min-¹. No entanto, o tempo de residência dos protótipos com materiais de solo foi acentuadamente superior aos de brita calcária, o que pode ser uma desvantagem para seu emprego. Não obstante, o uso de materiais de solo em conjunto com brita calcária pode ser uma estratégia importante nos períodos de chuva para aumentar a segurança do sistema de remoção do As e neutralização da acidez das águas de drenagem.

SIQUEIRA, A.C.de A. Geoquímica das laterais de domínio médio Coreaú - Noroeste do Estado do Ceará. 2012. 97 f. Dissertação (Mestrado)- Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012.
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This paper makes an assessment of the geochemical signature of the lateritic rocks that occur near the towns of Granja, Martinópole and Parazinho northwest of the state of Ceara. Geologically the area is located in Médio Coreaú Domain, located in the northwestern portion of the Borborema Province, is characterized by the Granja Complex representing the basement of the region, composed of gneisses, granulites and migmatites, and supracrustal sequences composed by quartizitos, phyllites and schists of the Group Martinópole and Ubajara. The laterites occur forming a layer of weathering associated with phyllites, quartzites and gneisses and stand out to be an uncommon occurrence in areas considered semi-arid regions, where the most common would be associated with more humid climates (seasonal or not), so it is more likely that the process that led to the generation of these robes is due to different climatic conditions of the current old. The samples for geochemical analysis were collected at different points, where in each sample was collected from the source rock, the rock in the process of weathering and lateritic concretions in different lithologies in which the process is associated lateritization. The overall results show that in all the points considered, the contents of the oxides of iron and aluminum is higher, and the silica are lower than the bedrock, typical of a laterite profile. The H2O values also increased during the process and lateritization elements such as chromium, manganese, magnesium, sodium and phosphorus are stable. Taking into account the phyllite as source rock, it is observed that the enrichment in Al and Fe were found in the early stages of weathering, remaining stable during the process, as depletion of Si also followed this pattern of behavior. Iron was enriched in content of approximately 40% higher compared to the values shown in source rock. Considering the quartzite and gneiss in the increase of Fe content has become even more significant during the weathering process, with values greater than 70% of the rock in the process of change and of lateritic concretions. Results of X-ray diffraction show that the major oxides and hydroxides of the process are hematite and goethite in the oxidized sample stages silica is not present, in section 3 it is contained within the limit of concretionary nodules in training, this on a ledge mucking up the center. It can be considered by enriching the possibility of Fe mineralization, even though the enrichment of high-Al considered at all points where the contents of this element approximately estimated 6-7% of the rock in the process of change. However enrichment values are very significant Fe in the operation.
Este trabalho faz uma avaliação sobre as a assinatura geoquímica de rochas lateríticas que ocorrem nas imediações dos municípios de Granja, Martinópole e Parazinho a noroeste do Estado do Ceara. Geologicamente a área está localizada no Domínio Médio Coreaú, situado na porção noroeste da Província Borborema, é caracterizada, pelo Complexo Granja representando o embasamento da região, composto por gnaisses, granulitos e migmatitos, e por sequências supracrustais compostas pelos quartzitos e filitos do Grupo Martinópole e Ubajara. As lateritas ocorrem formando uma capa de intemperismo associada aos filitos, quartzitos e gnaisses e se destacam por serem uma ocorrência incomum em áreas consideradas semi-áridas, quando o mais comum seria estarem associadas a climas mais úmidos (sazonais ou não), portanto é mais provável que o processo que levou à geração desses mantos seja decorrente de condições climáticas antigas diferenciadas das atuais. As amostras para análise geoquímica foram coletadas em pontos distintos, onde em cada um deles foi coletado amostra da rocha fonte, da rocha em processo de intemperismo e das concreções lateríticas nas diferentes litologias em que o processo de laterização está associado. Os resultados gerais mostram que, em todos os pontos considerados, os teores dos óxidos de ferro e alumínio são superiores, e os de sílica são inferiores aos da rocha-mãe, característica típica de um perfil laterítico. Os valores de H2O também aumentam no decorrer do processo de laterização e elementos como o Cr, Mn, Mg, Na e P apresentam-se estáveis. No filito como rocha fonte, é possível observar que o enriquecimento em Al e Fe se deram nos primeiros estágios de intemperismo, permanecendo estável no decorrer do processo, assim como empobrecimento em Si também seguiu esse padrão de comportamento. O Fe foi enriquecido em teores de aproximadamente 40% maiores em relação aos teores apresentados na rocha fonte. Já no Complexo Granja e Grupo Martinólpole o aumento dos teores em Fe se tornou ainda mais significativo no decorrer do processo de intemperismo, apresentando valores maiores que 70% na rocha em processo de alteração e nas concreções de lateritas. Resultados de difração de raios X mostram que o principais óxi-hidróxidos envolvidos no processo são a hematita e goethita, nas fases mais oxidadas da amostra a sílica não está presente, no ponto 3 ela fica retida até o limite do nódulo concrecionário em formação, presente em uma borda zoneando o centro. É possível considerar que mesmo sendo alto o enriquecimento do Al em todos os pontos considerados, onde os teores desse elemento estimam aproximadamente 6 a 7% na rocha em processo de alteração, os valores de enriquecimento em Fe são muito significativos para exploração.

No Estado do Pará, convencionalmente são empregados rocha britada ou seixo rolado natural como agregados nas misturas asfálticas. Nas proximidades da região metropolitana de Belém, não há disponibilidade destes materiais, obrigando o transporte destes agregados de boa qualidade de pedreiras e jazidas distantes mais de 170 Km, aumentando consideravelmente os custos de pavimentação. Com o objetivo de redução de custos, buscou-se o estudo de um outro agregado natural nãoconvencional, a laterita, abundante nas proximidades de Belém. Três tipos de ligantes asfálticos foram utilizados nas misturas asfálticas pesquisadas: um asfalto convencional CAP de penetração 50-60 proveniente da refinaria da LUBNOR, no Ceará; um asfalto da refinaria da REMAN da Amazônia modificado por asfaltita; e um asfalto-borracha da região sudeste. Uma quarta alternativa da mistura asfáltica foi considerada, empregando conjuntamente laterita e seixo rolado como agregados. Foi realizada uma análise comparativa das misturas asfálticas baseada em ensaios laboratoriais tais como: dosagem Marshall, danos por umidade induzida, deformação permanente em simulador de tráfego, resistência à tração por compressão diametral, módulo de resiliência e fadiga. Um processo inovador foi concebido para separação e lavagem das lateritas. Os resíduos desta seleção de agregados foram testados de modo a viabilizar seu emprego como material de base ou sub-base. Foi realizada também uma breve análise mecanicista de estruturas de pavimentos com o auxílio do programa ELSYM 5. Concluiu-se que as misturas asfálticas com laterita lavada podem ser usadas em revestimentos de pavimento de vias públicas e de rodovias de baixo volume tráfego obtendo-se os melhores resultados para as misturas de lateritaasfalto com o ligante modificado por asfaltita.
Crushed igenous rocks and washed quartzite gravels are conventional aggregates for asphalt mixes in the State of Pará, northern Brazil. However, these materials are not available in many parts of the state, specially near the city of Belem, the state capital. The current practice is to import these high quality aggregates from the few quarries located in remote sites, leading to a considerable increase in construction costs. To cut down costs, it is necessary to look for alternative sources of natural aggregates. This study attempts to present an alternative solution for asphalt mixtures using a non-conventional natural aggregate: laterites, which are widely available in the metropolitan area. Three types of asphalt binders were used: a conventional one – AC penetration of 50-60, an asphalt cement modified by gilsonite, and an asphalt rubber. A fourth type of asphalt mix was considered, using washed quartzite gravels in addition to the laterite. A comparative analysis was conducted using parameters obtained from laboratory tests like Marshall design, stripping test, wheel tracking test, indirect tensile strength, resilient modulus, and fatigue life. An innovative process was developed to clean the laterite by water washing. Residuals from the process were tested regarding its possible use as a material for pavement base or subbase. Finally, a mechanistic analysis was performed, using ELSYM 5 software. Results indicate a good performance to the hot-mixes and the one with gilsonite modified binder presented the best performance.

Algumas indicações morfológicas sugerem que as superfícies de paisagem tropicais onde encontram-se os duricrusts ferruginosos, podem apresentar idades que variam desde o Quaternário até o Cretáceo, e que a laterização sobre estas superfícies pode ter sido iniciada simultaneamente ou não, estabelecendo-se uma sequência cronológica de formação escalonada de acordo com a elevação, em função da evolução geomorfológica das superfícies. Sabendo-se que no Planalto de Diamantina na Serra do Espinhaço Meridional (SdEM) são reconhecidos três níveis geomorfológicos correlatos aos ciclos de aplainamento da plataforma Sul-americana, o objetivo deste trabalho foi estudar as variações mineralógicas, geoquímicas e morfológicas de duricrusts ferruginosos da Serra do Espinhaço Meridional buscando entender os processos genéticos envolvidos e as implicações disto sobre a distribuição e evolução da paisagem regional e suas relações com os ciclos de aplainamento do continente Sul-americano. Para atingir estes objetivos, foram realizadas análises de difratometria de raios X, suscetibilidade magnética, microscopia eletrônica de varredura com sistema de energia dispersiva acoplado e análise elementar a partir da dissolução total dos minerais constituintes. Os resultados mostraram que no Planalto de Diamantina na SdEM coexistem níveis de ferricretes e lateritas na superfície correspondente ao ciclo erosivo Pós-Gondwanico. As superfícies lateríticas são provavelmente as formações supérgenas mais antigas da paisagem regional, originadas durante os processos denudacionais que ocorreram ao longo do ciclo erosivo Pós-Gondwanico. A erosão parcial de seu perfil laterítico constituíram o material fonte de Fe e Al para a gênese dos ferricretes distribuídos em superfícies elevadas (> 1200 m), especialmente aqueles em superfícies em torno de 1400 m de altitude. As variações paleoclimáticas do ciclo Pós-Gondwanico também proporcionaram ciclos erosivos alternados que resultaram no subescalonamento desta superfície, criando condições geomorfológicas favoráveis à gênese de ferricretes mais recentes (1200 - 1400 m). Além disso, os duricrusts ferruginosos do Planalto Diamantina (SdEM) sob influência do maciço quartzítico do Supergrupo Espinhaço e situados superfícies erosivas elevadas (> 1200 m), além de policíclicos, também podem apresentar características poligenéticas.
Some morphological indications suggest that the tropical landscape surfaces where the iron-rich duricrust are present may have ages varying from the Quaternary to the Cretaceous, and that the laterization on these surfaces may have been initiated simultaneously or not, establishing a sequence chronological formation according to the elevation, according to the geomorphological evolution of the surfaces. Three geomorphological levels correlated to the South American platform planing cycles are known on the Diamantina Plateau, for this the objective of this work was to study the mineralogical, geochemical and morphological variations of the iron-rich duricrust of the SdEM, trying to understand the genetic processes involved and the implications of this on the distribution and evolution of the regional landscape and its relations with the planning cycles of the South American continent. In order to reach these objectives, X-ray diffraction, magnetic susceptibility, scanning electron microscopy with dispersive energy system coupled and elemental analysis carried out from the total dissolution of the constituent minerals. The results showed that in the Diamantina Plateau at the SdEM, coexist levels of ferricretes and laterites on the surface corresponding to the Post-Gondwanic erosive cycle. The laterite surfaces are probably the oldest surviving formations of the regional landscape, originated during the denudation processes that occurred along the Post-Gondwanic erosive cycle. Partial erosion of its lateritic profile was source material of Fe and Al for the genesis of ferricretes distributed on high surfaces (> 1200 m), especially those on surfaces at 1400 m of altitude. The paleoclimatic variations of the Post-Gondwanic cycle also provided alternating erosive cycles that resulted in sub-scaling of this surface, creating geomorphological conditions favorable for genesis of earlier ferricretes (1200 - 1400 m). In addition, the ferricretes of the Diamantina Plateau (SdEM) under influence of the Quartzite massif of the Espinhaço Supergroup and located in elevated erosive surfaces (> 1200 m), besides polycyclics, may also present polygenetic characteristics.

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Os elevados custos das obras de engenharia civil induzem a necessidade de se desenvolver estudos de processos de estabilização e reforço que possibilitem melhorar determinadas propriedades geotécnicas dos solos, de modo a enquadrá-los dentro das especificações construtivas vigentes. A técnica de reforço de solos através da inclusão de fibras tem sido estudada por vários pesquisadores, e tem se mostrado eficiente, melhorando várias propriedades de engenharia do solo, gerando um compósito bastante atraente para a engenharia geotécnica, que neste trabalho será denominado fibrossolo. A avaliação do efeito da adição de fibras de sisal ao solo laterítico foi feita experimentalmente, em laboratório, determinando-se o comportamento mecânico via ensaios de compactação (na energia do Proctor Normal) e CBR, bem como sua resistência ao cisalhamento, através do ensaio de cisalhamento direto. Adotou-se como ponto de partida para análise, os teores de fibra de 0,25% a 1,0% em função da massa seca do solo e, também, do comprimento das fibras, nos valores 10 a 25mm. O trabalho teve como objetivo complementar o estudo do efeito do tratamento superficial das fibras de sisal com poliestireno expandido (EPS) reciclado, visando sua aplicabilidade como elemento inibidor do processo de absorção de água. Com base nos resultados obtidos neste trabalho, notou-se que a adição de fibras de sisal tratadas de distribuição aleatória apresentou significativas melhorias nas propriedades mecânicas do solo laterítico, transformando-o em um produto de melhor qualificação para aplicação em obras de engenharia civil, e que o polímero utilizado mostrou-se bastante aplicado à análise proposta, promovendo diminuição da higroscopicidade das fibras de sisal. ____________________________________________________________________________________________________
ABSTRACT: The high costs of the civil engineering construction requires the necessity to develop studies about the process of the stabilization and reinforcement which improves some geotechnical soils properties being part of the constructive specifications. The reinforcement technique of the soils with the inclusion of natural fibers has been studied for many researchers. It has showing efficient by improving many properties of the soil engineering which results in an interesting composite material for the geotechnical engineering. This composite is named fibersoil at this research. Experiments was done at the laboratory to evaluate the effect of the addition sisal fibers in the lateritic soil which will establish the mechanical behavior of the material through compaction tests, at the energy of the Normal Proctor and CBR. The shear strength was done through the direct shear test. Therefore, in the present investigation sisal fiber was randomly included in to the soil at four different percentages of fiber content with 0,25% to 1% by weight of raw soil and also considered different lengths between 10 to 25mm. The objective of this research is to contribute to the study on the effect of the sisal fibers with superficial treatment with recycled expanded polystyrene (EPS) inhibiting the absorption of water. With base in the results obtained in this work, it was noticed that the addition treated sisal fibers randomly distributed presented significant improvements in the mechanical properties of lateritic soil, transforming it in a product of better qualification for application in works of civil engineering, and that the polymer used it was shown quite applied to the proposed analysis, promoting decrease of the water absorption of the sisal fibers.

Orientador: George Luiz Luvizotto
Banca: Vania Rosolen
Banca: Rafael Rodrigues de Assis
Banca: Carolina Del Roveri
Banca: Fabiano Cabañas Navarro
Resumo: A natureza da mobilização, enriquecimento e fracionamento dos elementos terras raras e o ítrio (ETR) nos processos de intemperismo ainda é pouco compreendida. Diversos trabalhos seguiram o entendimento de que esses elementos fossem imóveis perante o intemperismo, o que foi refutado pela descoberta dos depósitos de ETR do tipo ion-adsorption clay (IAC) no sudeste asiático na década de 60, onde se observou o transporte desses elementos no perfil laterítico seguido de acumulação por fixação em minerais neoformados. Os depósitos do tipo IAC se desenvolvem quando biotita e/ou muscovita sienogranitos portadores de minerais de ETR susceptíveis ao intemperismo são submetidos ao intemperismo tropical, onde os ETR são liberados de sua mineralogia original e acumulados no horizonte saprolítico ao serem adsorvidos por argilominerais cauliníticos neoformados. Com base nisso, foi feito um processo prospectivo, tomando como base as características químicas e mineralógicas dos granitos mineralizados em ETR do tipo IAC no sudeste asiático, onde se identificou corpos graníticos no Terreno Apiaí-Guaxupé com características prospectivas para esse modelo de mineralização. Os granitos São Francisco e Capão Bonito, corpos cálcio-alcalinos compostos por biotita sienogranitos metaluminosos a peraluminosos e portadores de minerais (fluor)carbonáticos de ETR, muito susceptíveis ao intemperismo, foram tomados como base para estudo da mobilidade desses ETR no meio exógeno. Nesses corpos foram identificad... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The nature of the mobilization, enrichment and fractionation of the rare earth elements and yttrium (REE) in weathering processes are still poorly understood. These elements have been considered immobile in weathering profiles, taking into consideration their behavior in other geological processes. In the 1960‟s, the discovery of the ion-adsorption clay (IAC) REE deposits in the southeast Asia, and subsequent studies at other locations, has pointed out to the mobilization of REE in weathered granites, with the possibility of accumulation and retention of these metals neoformed minerals. The IAC deposits are developed by weathering of biotite and/ou muscovite syenogranites that contain weakly resistant REE-bearing minerals. At those conditions, the REE are leached from weakly resistant minerals and accumulated in the saprolite horizon, where they are adsorbed onto the surface neoformed clayminerals, particularly those from the kaolinite group. In this study, prospecting REE IAC work in the southeast of Brazil began with a compilation of published geochemical data on granite occurrences, in order to compare them with the granites that originate IAC deposits in south of China. Results show that that tardi- to post-tectonic granites on the Apiaí-Guaxupé Terrain, especially those from the Itu Rapakivi Province, have geochemical and geological aspects that are similar to those of exogenous REE mineralized granites. In the present work, the exogenous mobility of REE is evaluated by ... (Complete abstract click electronic access below)
Doutor

Orientador: Francisco Sergio Bernardes Ladeira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias
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Resumo: Muitos trabalhos no âmbito da geomorfologia buscaram associar níveis altimétricos às superfícies de erosão. Partindo-se da teoria de Davis, de topos concordantes ou topos de mesma altitude (uma abordagem clássica baseada em pontos de maior altitude), realiza-se a associação destas superfícies com a ocorrência de perfis bauxíticos, identificando-se assim as antigas superfícies ou paleosuperfícies. Portanto, este trabalho tem como objetivo principal correlacionar as superfícies geomórficas com os perfis de alteração, no caso, os Perfis Lateríticos-Bauxíticos, utilizando-se destes como marcos estratigráficos. A partir do trabalho de campo, no Planalto de Poços de Caldas encontrou-se três tipos de Perfis Bauxíticos: de Serra, de Campo e Retrabalhados. Os Perfis de Serra são mais espessos que os Perfis de Campo, com maior teor de alumínio e menor teor de sílica, indicando que provavelmente se formaram no topo, onde a drenagem permitiu uma maior lixiviação e concentração de alumínio. O que diferencia um Perfil de Serra do de Campo é uma camada de argila existente entre a rocha e a bauxita. Esta camada de argila não possui estruturas da rocha e é bastante homogênea, enquanto, em todo o depósito encontram-se volumes com estrutura concêntrica e sistemas de fraturas preservados do material de origem. Os Perfis Bauxíticos Retrabalhados possuem sua origem nos Perfis de Serra, pois nestes materiais a concentração de alumínio é elevada e a de sílica é baixa. Ao correlacionar os Perfis Bauxíticos, com as prováveis superfícies geomórficas, segundo a altimetria, percebe-se que não há uma ordem, os perfis estão distribuídos aleatoriamente nas bordas e no interior da área, em diferentes patamares do relevo, onde especialmente observa-se a ocorrência de Perfis Bauxíticos de Serra posicionados em altimetrias de Perfis de Campo e Perfis Retrabalhados posicionados sobre Perfis de Serra, acima dos 1.400 metros. O controle estrutural observado em campo, na literatura e nas cartas topográficas nos mostra zonas de falhas comuns, podendo-se associar esta descontinuidade do perfil bauxítico com essas movimentações. Uma das evidências mais claras são os padrões de drenagem que são preferencialmente controlados pelos alinhamentos estruturais que seccionam o embasamento. Muitas movimentações, provavelmente, ocorreram anteriormente à formação dos perfis bauxíticos, entretanto ocorreu uma reativação das falhas, pois se verificou que as falhas cortam os materiais associados aos Perfis de Serra, Perfis de Campo e em alguns casos, afetam os níveis de Perfis Retrabalhados, indicando que a atividade tectônica não se restringiu apenas em moldar o quadro (junto com o clima) dos processos erosivos que afetaram os perfis in situ, mas avançou para além dos eventos de formação dos materiais lateríticos depositados
Abstract: Many works in the geomorphology scope have tried to associate the elevation levels with the erosion surfaces. Starting from Davis' accordance tops or similar elevation theory (a classical aproach based in points of higher elevation) it is proposed the association of these surfaces with the occurrence of Bauxite Profiles, identifying the old surfaces or paleosurfaces. Therefore, this work has the main objective of correlating the geomorphic surfaces with the alteration profiles, in this case the Bauxite Laterite Profiles, applying these as statigraphic marks. Through the field work in Poços de Caldas Plateau were found three types of Bauxite Profile: Rim, Plateau and Reworked Profiles. The Rim Profiles are thicker than the Plateau Profiles, with bigger amount of aluminium and smaller of silica, indicating that they probably were formed in top, where the drainage allowed a bigger leaching and concentration of aluminium. The aspect that distinguishes a Rim from a Plateau Profile is a clay layer between the rock and the bauxite. This clay layer does not have rock structures and it is rather homogeneous, while, in the whole deposit were found contents with concentrical structure and fractures systems preserved from the material of origin. The Reworked Bauxite Profiles have their origin in Rim Profiles, because in these materials the concentration of aluminium is high and silica is low. Correlating the Bauxite Profiles with the probable geomorphical surfaces, following the altitude, it is not noticed any order, the profiles are distributed at random in the borders and in the inner area, in different levels of relief, where it is specially observed the occurrence of Bauxite Rim Profiles located in elevations of Plateau Profiles, and Reworked Profiles located over Rim Profiles, above 1,400 meters. The structural control observed in field, in literature and in the topographic maps shows zones of common faults, and 0it can associate this discontinuity of the Bauxite Profile with these movements. One of the clearest evidences are the drainage patterns, which are mainly controlled by basement structural alignments. Probably many movements have taken place before the formation of the Bauxite Profiles, however, a reactivation of the faults has ocurred, therefore it was verified that the faults cut the materials associated with Rim Profiles, Plateau Profiles and, specially in some instances, affect the levels of Reworked Profiles, indicating that the tectonic activity did not restrict only in molding the chart (with the climate) of the erosive processes which have affected the profiles ¿in situ¿, but it has advanced farther on the events of formation of the deposited laterite materials
Mestrado
Análise Ambiental e Dinâmica Territorial
Mestre em Geografia

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GEOCIAM - Instituto Nacional de Ciência e Tecnologia de Geociências da Amazônia
O depósito mineral de Sapucaia, situado no município de Bonito, região nordeste do Estado do Pará, é parte de um conjunto de ocorrências de fosfatos de alumínio lateríticos localizados predominantemente ao longo da zona costeira dos estados do Pará e Maranhão. Estes depósitos foram alvos de estudo desde o início do século passado, quando as primeiras descrições de “bauxitas fosforosas” foram mencionadas na região NW do Maranhão. Nas últimas décadas, com o crescimento acentuado da demanda por produtos fertilizantes pelo mercado agrícola mundial, diversos projetos de exploração mineral foram iniciados ou tiveram seus recursos ampliados no território brasileiro, dentre estes destaca-se a viabilização econômica de depósitos de fosfatos aluminosos, como o de Sapucaia, que vem a ser o primeiro projeto econômico mineral de produção e comercialização de termofosfatos do Brasil. Este trabalho teve como principal objetivo caracterizar a geologia, a constituição mineralógica e a geoquímica do perfil laterítico alumino-fosfático do morro Sapucaia. A macrorregião abrange terrenos dominados em sua maioria por rochas pré-cambrianas a paleozóicas, localmente definidas pela Formação Pirabas, Formação Barreiras, Latossolos e sedimentos recentes. A morfologia do depósito é caracterizada por um discreto morrote alongado que apresenta suaves e contínuos declives em suas bordas, e que tornam raras as exposições naturais dos horizontes do perfil laterítico. Desta forma, a metodologia aplicada para a caracterização do depósito tomou como base o programa de pesquisa geológica executada pela Fosfatar Mineração, até então detentora dos respectivos direitos minerais, onde foram disponibilizadas duas trincheiras e amostras de 8 testemunhos de sondagem. A amostragem limitou-se à extensão litológica do perfil laterítico, com a seleção de 44 amostras em intervalos médios de 1m, e que foram submetidas a uma rota de preparação e análise em laboratório. Em consonância com as demais ocorrências da região do Gurupi, os fosfatos de Sapucaia constituem um horizonte individualizado, de geometria predominantemente tabular, denominado simplesmente de horizonte de fosfatos de alumínio ou crosta aluminofosfática, que varia texturalmente de maciça a cavernosa, porosa a microporosa, que para o topo grada para uma crosta ferroalumino fosfática, tipo pele-de-onça, compacta a cavernosa, composta por nódulos de hematita e/ou goethita cimentados por fosfatos de alumínio, com características similares aos do horizonte de fosfatos subjacente. A crosta aluminofosfática, para a base do perfil, grada para um espesso horizonte argiloso caulinítico com níveis arenosos, que repousa sobre sedimentos heterolíticos intemperizados de granulação fina, aspecto argiloso, por vezes sericítico, intercalados por horizontes arenosos, e que não possuem correlação aparente com as demais rochas aflorantes da geologia na região. Aproximadamente 40% da superfície do morro é encoberta por colúvio composto por fragmentos mineralizados da crosta e por sedimentos arenosos da Formação Barreiras. Na crosta, os fosfatos de alumínio estão representados predominantemente pelo subgrupo da crandallita: i) série crandallita-goyazita (média de 57,3%); ii) woodhouseíta-svanbergita (média de 15,8%); e pela iii) wardita-millisita (média de 5,1%). Associados aos fosfatos encontram-se hematita, goethita, quartzo, caulinita, muscovita e anatásio, com volumes que variam segundo o horizonte laterítico correspondente. Como os minerais pesados em nível acessório a raro estão zircão, estaurolita, turmalina, anatásio, andalusita e silimanita. O horizonte de fosfatos, bem como a crosta ferroalumínio-fosfática, mostra-se claramente rica em P2O5, além de Fe2O3, CaO, Na2O, SrO, SO3, Th, Ta e em terras-raras leves como La e Ce em relação ao horizonte saprolítico. Os teores de SiO2 são consideravelmente elevados, porém muito inferiores aqueles identificados no horizonte argiloso sotoposto. No perfil como um todo, observa-se uma correlação inversa entre SiO2 e Al2O3; entre Al2O3 e Fe2O3, e positiva entre SiO2 e Fe2O3, que ratificam a natureza laterítica do perfil. Diferente do que é esperado para lateritos bauxíticos, os teores de P2O5, CaO, Na2O, SrO e SO3 são fortemente elevados, concentrações consideradas típicas de depósitos de fosfatos de alumínio ricos em crandallita-goyazita e woodhouseítasvanbergita. A sucessão dos horizontes, sua composição mineralógica, e os padrões geoquímicos permitem correlacionar o presente depósito com os demais fosfatos de alumínio da região, mais especificamente Jandiá (Pará) e Trauíra (Maranhão), bem como outros situados além do território brasileiro, indicando portanto, que os fosfatos de alumínio de Sapucaia são produtos da gênese de um perfil laterítico maturo e completo, cuja rocha fonte pode estar relacionada a rochas mineralizadas em fósforo, tais como as observadas na Formação Pimenteiras, parcialmente aflorante na borda da Bacia do Parnaíba. Possivelmente, o atual corpo de minério integrou a paleocosta do mar de Pirabas, uma vez que furos de sondagem às proximidades do corpo deixaram claro a relação de contato lateral entre estas unidades.
The mineral deposit of Sapucaia, located in Bonito county, northeast of Pará state, is part of a set of occurrences of lateritic aluminum phosphates located predominantly along the coastal area of Pará and Maranhão states. These deposits were subjetc for study since the beginning of the last century, when the first descriptions of "phosphorous bauxites" were mentioned in the NW region in Maranhão. In the last decades, with the increase demand for fertilized products for agricultural world market, various mineral exploration projects were started or expanded their resources in Brazilian territory, among them there is the economic viability of deposits of aluminous phosphates, as Sapucaia, which will be the first project of economic mineral production and marketing of thermophosphates of Brazil. This study aimed to characterize the geology, mineral composition and geochemistry of lateritic aluminum phosphates profile of the Sapucaia hill. The macro-region inclued lands mostly dominated by Precambrian to Paleozoic rocks land, locally defined by Pirabas Formation, Barreiras Formation, latosoils and recent sediments. The morphology of the deposit is characterized by a discrete elongated hillock that offers smooth and continuous slopes at its edges, which become rare natural exposures of the laterite profile horizons. So, the methodology used to characterize the deposit was based on the program of geological research performed by “Fosfatar Mining”, hitherto owns their mineral rights, has provide two trenches and samples of 8 drill cores. Sampling was limited to the extent of lithological lateritic profile, with the selection of 44 samples at intervals of 1m, and underwent a course of preparation and laboratory analysis. According with the other occurrences of the Gurupi region, the phosphates of Sapucaia contains an individualized horizon, called simply aluminum phosphates or aluminophosphatic crust, which varies texturally to massive horizon, cavernous, porous microporous, which to the top transitions to phosphate ferroalumino crust, “leopard skin”, cavernous, composed of nodules of hematite and / or goethite cemented by aluminum phosphates, with similar characteristics to the underlying phosphate horizon. The aluminophosphatic crust to the base of the profile transition to a thick horizon kaolinitic clay with sand layers, which rests on weathered heterolithic fine-grained sediments, sericite clay aspect, sometimes interspersed with sandy horizons, and have no apparent correlation with other rocks outcrop in the region. Approximately 40% of the surface of the hill is covered by colluvium composed of mineralized fragments of the crust and sandy sediment from Barreira Formation. In the crust, the aluminum phosphates are predominantly represented by the subgroup of crandallite: i) Crandallite-goyazite (average 57.3%); ii) woodhouseite-svanbergite (average 15.8%); and iii) wardite-millisite (average 5.1%). Associated with phosphates are: hematite, goethite, quartz, kaolinite, muscovite and anatase, with volumes that vary according to the corresponding laterite horizon. As the heavy minerals in the accessory level are zircon, staurolite, tourmaline, anatase, andalusite and sillimanite. The horizon of phosphates and iron phosphate crusts shows be clearly rich in P2O5, and Fe2O3, CaO, Na2O, SrO, SO3, Th, Ta and LREE such as La and Ce relative to the horizon saprolite. The contents of SiO2 are pretty high, but much lower than those identified in lower clay horizon. In profile as a whole, there is an inverse correlation between SiO2 and Al2O3, between Al2O3 and Fe2O3, and positive between SiO2 and Fe2O3, which confirms the nature of the lateritic profile. Different from what is expected by bauxitic laterites, the content of P2O5, CaO, Na2O, SrO and SO3 have a elevated concentration, considered typical of phosphate deposits of aluminum rich in crandallite-goyazite and woodhouseite-svanbergite. The succession of horizons, the mineralogical composition and geochemical patterns allow correlating the deposit with other aluminum phosphates presents in the region, more specifically Jandiá (Pará) and Trauíra (Maranhão), as well as others located beyond the Brazilian territory, thus indicating that the aluminum phosphates of Sapucaia are the genesis of a lateritic mature and a complete profile, products whose source rock may be related to mineralized rocks in phosphorus, such as those observed in Pimenteiras Formation, partially outcropping on the edge of the Parnaíba Basin. Possibly, the current ore body was integrated of Pirabas paleocost sea, since drill holes on the side of the body, made clear the relationship of lateral contact between these units.

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CPRM - Companhia de Pesquisa de Recursos Minerais / Serviço Geológico do Brasil
O objetivo principal deste trabalho foi estabelecer um estudo sistemático do padrão de dispersão dos elementos químicos em solos e crostas lateríticas, derivados de litótipos de ambientes geológicos diversos em áreas de clima tropical úmido na Amazônia. Foram selecionados 2 alvos a amostragem de solos que apresentam características de latossolos: um na Serra dos Carajás, no sudoeste do Estado do Pará(N-5), rico em gibbsita e o segundo (TN-6), localizado na Serra do Tiracambu, municípios de Carutapera e Bom Jardim, no Estado do Maranhão. Possue predominância de caulinita e oxi-hidróxidos de ferro, sobrepostos a bauxita. Para o estudo das crostas, foi selecionada a crosta ferro-fosfática de Pirocaua contendo solo nas bordas, localizada próximo a foz do rio Maracaçume, município de Godofredo Viana, litoral noroeste do Estado do Maranhão e a crosta ferruginosa do alvo N-1 na Serra dos Carajás. A metodologia utilizada foi a mesma para os quatros alvos, a saber: a- para a obtenção dos contrastes mineralógicos e geoquímicos necessários foi utilizada amostragem em superfície em malhas de 200 por 200 metros; b- separação das amostras de solo em três partes, amostra total, fração menor que 200mesh e fração -80+200 mesh (para as crostas, foi utilizada apenas a amostra total).; c- as analises mineralógicas foram realizadas através da difratometria de raios-X, enquanto as análises químicas foram feitas por absorção atômica para determinação de Ni, Co, Cr, Cu, Mn, V, As e Bi, e, Au através da análise por fusão; d- determinações por fluorescência de raios-X para SiO2, Fe2O3, Al2O3, TiO2, P2O5, Ba, Y Nb, Zr, Ga e Sc; através de espectrografia ótica de emissão com pré-concentração foram analisados os EGP (Pt, Pd, Rh) e por ICP os ETR. Os dados químicos e mineralógicos foram tratados para obtenção de parâmetros estatísticos básicos através de microcomputadores IBM-PC/XT compatíveis, utilizando-se o "Sistema Geoquant" (versão 3.1), da CPRM. Outros programas (CONVERT e o QPRO),foram utilizados como complementares no estudo estatístico ou na representação gráfica dos dados, alem de analises de agrupamentos realizadas através do programa CLUSTER, utilizando o "Modo R" e o "Modo Q". os resultados obtidos através da difratometria de raios-x, mostraram que no alvo TN-6 na serra do Tiracambu, o latossolo caracteriza-se mineralogicamente por certa homogeneidade, com predominância de caulinita, Al-goethita e anatásio. Esta homogeneidade é mostrada também na composição química, tanto na amostra total como nas frações analisadas, através de uma distribuição de SiO2-Al2O3-Cu-Mn-Sr, Fe2O3-V-Cu-Ba-Cr-As-Sc-ETR e TiO2-Y-Nb-Zr-Ga-Sc-ETR como principais associações geoquímicas, refletindo a caulinita, oxi-hidróxidos de ferro e o anatásio. Já no alno N-5, na Sera dos Carajás, os latossolos são constituídos de gibbsita seguida de goethita-hematita e em menor quantidade caulinita e anatásio. Neste alvo, embora do ponto de vista mineralógico apresnte como única diferença a presença da gibbsita em relação ao alvo TN-6, destacam-se, por outro lado, as associações TiO2-Al2O3-Ga-Zr-Sc-Sr e Fe2O3-Mn-V-Cr-Sc-As. A primeira, representando a gibbsita e anatásio, que alem de ser mais consistente, envolve a associação do Fe2O3, que, por sua vez, reflete os oxi-hidróxidos de ferro e, de forma indireta, a interferência de rochas básicas na origem dos latossolos. Os resultados obitidos nas amostras de crostas, como a do alvo N-1 que apresenta diferenciação textural: estratificada, pisolítica e cavernosa, mostram que independente da textura, apresentam concentrações semelhantes para MN, SR, Nb e Ga. Os estudos revelaram uma pequena diferença constatada na crosta cavernosa que émais rica em gibbsita, e onde predomina também a presença de Au e Pt. Na totalidade doa alvo N-1, a associação geoquímica mais significativa foi definida por Al2O3-TiO2-Cr-V-Sr-Nb-Zr-Ga-Sc-As. A baixa concentração dos elementos traços nesta associação reflete sua origem a partir das rochas desprovidas de silicatos ferromagnesianos, de natureza sedimentar, compouco influencia máfica-ultramáfica. Na serra do Pirocaua, a nalise de agrupamentos e matrizes de correlação estabeleceram duas grandes associações geoquímicas semelhantes na crosta e nos solos. A primeira, Fe2O3-V-Ga-Ni-Cu-Cr-As, indica os minerais de ferro representados principalmente por goethita e hematita e a segunda, P2O5-Al2O3-(TiO2)-Sr-Y-Zr-ETR, reflete os fosfatos do grupo da crandalita. A associação do Fe2O3 é mais freqüente e ocupa grande parte do platô, não discriminada crosta e solos, assim como o ouro que apresentou indistintamente valores qualificados em 13 amostras, comédia de 0.2 ppm, tendo como valor maximo1,01 ppm. As concentrações de As possuem em média 188 ppm na crosta e 273 ppm nos solos, às quais estão associadas a presença da turmalina (dravita) no solo e, localizadamente, preenchendo fraturas na crosta, passível de ser observada em alguns afloramentos, evidenciando a influencia de zona hidrotermal. Resaltam-se também os valores qualificados para Pt (0.1 a 0.4 ppm), diretamente associados às altas concentrações de Cr (1235 ppm na crosta), além dos altos teores de P2O5 (11,85-solo a 15,05%-crosta), evidenciando que o substrato da serra do Pirocaua é de naturaza vulcano sedimentar, de composição básica, rica em fosfatos. Os estudos realizados são importantes na caracterização de solos e crostas lateríticas, do ponto de vista geológico, mineralógico e químico, observando-se que em ambos casos, a amostragem em superfície reflete com certa segurança a naturaza dos substrato através das associações geoquímicas, como foi observado nos alvos N-5 e Serra do Pirocaua a influencia de rochas básicas, e, nos alvos TN-6 e N-1 a influencia de rochas sedimentares. Este fato reveste-se de importância para a utilização da prospecção geoquímica, na caracterização de litótipos que constituem o substrato de coberturas autóctones na Amazônia, visto que, a freqüência da distribuição daqueles litotipos nesta região é bastante extensiva e com escassez de afloramentos, estando a eles relacionados ambientes hospedeiros de mineralizações e depósitos minerais, cujas rochas encaixantes não são facilmente diagnosticadas face a condição morfológica e espessura de suas coberturas.
This work intention is to stand out a sistematic study on the chemical elements dispersion in soils and duricrust, developed over, diversified geological environments lithotypes, under humid tropical climate in the Amazon region-. Two target areas were chosen for soil sampling( Serra dos Carajás-N-5 and Serra do Tiracambu TN-6); the former, a gibbsite rich latosoil, is situated in the southwest part of Pára State; the latter, has a predominartee- of kaolinite and iron oxi-hydroxides overling a bauxite layer, situated in the western border of Maranhão State. Two other areas were selected for duricrust studies, Pirocaua iron-phosphate crust, surrounded by latosoil ( NW of Maranhão State) and Serra dos Carajás target N-1 feruginous crust. The methodology assumed was the same for all targets for both soil and duricrust, as follow: a - sampling grid of 200x200m; b - Three parts separation of soil samples (bulk,<200-14 and -80-F200- mesh- )-for duricrusts were only considered bulk samples; - X-ray difratometric analysis were carried out to determine mineralogical composition and atomic absortion for determination of Ni,Co,Cr,Cr,Mn,V,As and Bi and, Au, through fire assay; d X-ray fluorescence analysis were taken for SiO2,Fe2O3,Al2O3,TiO2,Ba,Y,Nb,Zr,Ga and Sc; PGE (Pt,Pd,Rh) and REE analysis were obtained by aplicai emission spectrography after pre concentration and ICP, respectively. Mineralogical and chemical data were processed in order to obtain basic statistical parameters by using compatible PC-IBMIXT through Geoquant System CPRM 3.1 version, as well as some other complementary softwares CONVERT and QPRO) both in the statistical studies and graphic data display, besides CLUSTER R MOD and Q MOD analysis. Target TN-6 X-ray difratometry soil samples analysis showed a mineralogical homogeneous character as predominantly composed by kaolinite,A1-goethite and anatase. This homogeneity is also present in bulk sample chemical composition and in the analized fractions as well,revealing a distribution of three main geochemical association-SiO2-Al2O3-Cu-Mn-Sr; Fe2O3-V-Cu-Ba-Cr-As-Sc-REE and TiO2-Y-Nb-Zr-Ga-Sc-REE as a reflect of kaolinite, iron oxi-hydroxide and anatase,respectively. On the other hand target N-5 latosoils are made out by gibbsite followed by goethite-hematite and in minor content, kaolinite and anatase. Although this target, from the mineralogical point of view, does not present much difference from the TN-6 except for the presence or gibbsite, it outstands the association of TiO2- Al2O3-Ga-Zr-Sc-Sr as well as Fe2O3-Mn-V-Cr-Sc-As. The former association representing gibbsite and anatase, besides being more consisterrt, surrounds the Fe2O3 association wich in turn reflect iron oxi-hydroxides and, indirectly, the contribution of basic rocks in the latosoils origin. Regarding target N-1duricrust, which presents differents textures (stratified,pisolitic and cavernous), the results obtained showed independently, similar concentration for Mn, Sr,Nb and Ga. Small difference characterize the cavernous duricrust in the gibbsite content and the predominantly presence of Au and Pt. In target N-1, as a whole, the most significant geochemical association was defined by Al2O3-TiO2-Cr-V-Sr-Nb-Zr-Ga-Sc-As. Low concentration of trace elements in this association reflects its origin from sedimentary nature Fe-Mn silicate deprived rocks, with low mafic/ultramafic contribution correlation matrix and groupment analysis in the Pirocaua target stablished two great geochemical associations with equal importance for soils and duricrust. The first, Fe2O3-V-Ga-Ni-Cu-Cr-As, indicates iron minerais, chiefly goethite and hematite, while the second, P2O5-Al2O3-(TiO2)-Sr-Y-Zr-REE reflects the crandallite-goyazite group of phosphates. The iron association is more frequent, occuping great extension of the plateau, not discerning soils or duricrust. So does the Au disperssion which presents indistinctly qualified values for 13 samples averaging 0.2 ppm and 1.01 ppm as maximum value. Arsenic concentratiton achieved an average of 188 ppm in duricrusts and 273 ppm in soils to which are associated the presence of tourmaline (dravite) in soil derived from hydrothermal zones noticiable in some outcrops fractures. Regarding PGE,qualified values for PT ( 0.1 to 0.4ppm) are directly associated to high concentration of Cr ( 1235 ppm in duricrust) and high values of P2O5 ( 11.85% soil to 15.05%-duricrust), this geochemical landscape is an evidence a basic composition vulcanosedimentary bedrock, rich in phosphates for the Serra do Pirocaua. The studies carried out were important in characterizing soils and duricrusts under a geological, mineralogical and chemical pooints of view, considering that, in both sample categories a surface sampling reflects, till certain extent and accuracy, trough geochemical association, the bedrock nature from which these covers had derived, as observed in the Pirocaua and N-5 targets the contribution of basic rocks as well as in the TN-6 and N-1 sedimentary rocks influence. This fact shows an importance to.consider.in the geochemical surveys, in characterizing concealed bedrock lithotypes by sampling their autochthonous covers, developed under humid tropical climate regions as the Amazon, taking into account that these rocks are not easily identified due the morphological condition involved and the consequent thicknes of the overburden. This is most outstanding inasmuch that the widrespread distribution frequency of those lithotypes in this region plus the scarcety of outcrops and their relationship to host environments of mineral deposits.

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O estudo sobre a evolução mineralógica e geoquímica dos lateritos da Serra de Maicuru-PA, formados a partir do intemperismo de rochas pertencentes ao complexo alcalino-ultramáfico-carbonatitico, foi feito com base nas amostragens (total de 223 amostras), abrangendo materiais de perfis lateríticos (sobre glimerito, apatitito, piroxenito, biotitito, dunito e sienito) e de superfície (crosta e solos). Este estudo demonstrou que após a dissolução dos carbonatos, alteração completa dos piroxênios e anfibólios em esmectitas e das micas (biotita e flogopita) em vermiculita e alteração incipiente das fluora-patitas, ocorreu: enriquecimento dos ETR, provavelmente sob as formas de hidroxi-carbonatos; perdas moderadas para o Si, Ca, Mg, Na, K, Mn, Zn, Sr, Y e PI: e retenção do Al, Ni, Co, Cu (mantidos nas esmectítas e vermiculita), Fe, Ti, Nb, representados pela ilmenomagnetita, titanita e perovskita (Ti e Nb), e Zr, alojado preferencialmente na ilmenomagnetita e titanita. Na interface horizontes de transição e argilo-fosfático, ocorreu a degradação das esmectitas e vermiculita e dissolução das fluorapatitas e perovskita, enquanto que a titanita e ilmenomagnetita permaneceram inalteradas. Portanto, foram obtidos como produtos a caolinita, goethita, anatásio e fosfatas aluminosos (wavelita, wardita e grupo da crandalita). Foi verificado assim, em relação aos níveis inferiores dos perfis, o enriquecimento moderado de Ti, Nb e Zr, deficiência dos ETR, especialmente ETRL, retenção de Al e Fe e perdas expressivas dos outros elementos analisados. Nos níveis intermediários do horizonte argilo-fosfótico. Procedeu-se à transformação da titanita em anatásio, com retenção do Nb e Zr em sua estrutura e liberação dos ETR, Ca,Sr e Na, que foram retidos sob as formas dos fosfatos do grupo da crandalita e wardita. Na parte superior deste horizonte ocorreu a oxida4o da ilmenomagnetita, que posteriormente evoluiu para maghemita e anatasio. A partir deste nível foi possível verificar nos perfis lateriticos: um grande enriquecimento em Y, ETR, (principalmente dos ETRL, tendo em vista os elevados teores de fosfato do grupo da crandalita), Ti, Nb, Fe e Zr, representados pelo anatásio goethita e maghemita; enriquecimento moderado do Cu sob a forma de turquesa, do Sr e Zn, abrigados na estrutura do grupo da crandalita, do Mn, contido nos relíctos de ilmenita e sob a forma de hidróxido (que deve ter fixado frades remanescentes de Co); lixiviação acentuada do Si K, Ca e Mg, moderada do Na e Ni e pouco expressiva do P. Os padrões de distribuição dos ETR normalizados aos condrítos para as rochas mães indicaram enriquecimento preferencial dos ETRL em relação aos ETRP. Este comportamento foi refletido ao longo dos perfis lateriticos, porém tornou-se mais acentuado nas amostras de crosta aflorante, haja vista a abundância de fosfato do grupo da crandalita. Foi observado eventualmente um maior enriquecimento em ETRP em relação aos ETRL, no horizonte argilo-fosftico e em algumas amostras da crosta, devido provavelmente, à formação da churchita. Esses lateritos apresentam perspectivas econômicas favoráveis especialmente para fosfatos, titânio e terras raras.
The study on the mineralogical and geochemical evolution of the laterites formed from the weathering of the aika-Iine-ultramafic-carbonatite rocks of the Maicuru complex, Pará, were based in the sampling of laterites (about 223 samples), including lateritic profiles (on the apatitite, glimmerite, pyroxenite, biotitite, dunite and syenite) and surface (crust and soils) materials. This study permited to conclude that after dissolution of the carbonates, complete alteration of the pyroxenes and anphiboles in to smectites and micas (biotite and phlogopite) in to vermiculite, and incipient alteration of the fluorapatite, occurred: enrichement of the REE, probabig in the form of carbonate-hidroxi; moderate losses in Si, Ca, Mg, Na, K, Mn, Zn, Y, Sr and P; and retention of Al, Ni, Co, Cu, main-tmined in smectite and vermiculite, Fe, Ti, Nb, represented bg ilmenomagnetite, titanite and perovskite (Ti and Nb), and Zr, lodged in the ilmemomagnetite and titanite structures. In the transitional and phosphatic-clageg hor)zons interface occured the degradation of smectite and vermiculite and dissolution of fluorapatite and perovskite, while titanite and ilmenomagnetíte remain inaltered. In this wag the following products were obtained: Kaolínite, goethite, anatase and aluminous phosphates (wavelite, wardite and crandallite group). Hence, was observed: moderate enrichment in Ti, Nb and Zr, depletion in rare earth elements, especially in the LREE; retention of Al and Fe; and expressive losses in other elements analyzed, relative to the lower levels of the Profiles. In the intermediary levels of the phosphatic-clayey horizon the transformation of the titanite into anatase, took place with retention of Nb and Zr in its structures and the liberation of REE, Ca, Sr and Na, which were in part retained as crandallite group and wardite phosphates. In the phosphatic-clayey and crust horizons interface oxidation of ilmenomagneti-te occurred, with latter evolution into maghemite and anatase. From this level was possible to verify into the lateritic profiles: a great enrichment in Y, REE, (mainly LREE, due to high concentration in crandalite group), Ti, Nb, Fe and Zr, represented by anatase and maghemite; moderate enrichement of Cu, as turquoise, Sr and Zn, acomoded in structure of the crandallite group; Mn contained in the ilmenites and as hgdroxides (which fixed fractions of Co); intense lixiviation of Si, Kr Ca and Mg, moderate lixiviation of Na e Ni; and little lixiviation of P. The chondrite normalized REE patterns for the parent rocks indicated a preferable enrichment in LREE relative to the HREE. This behavior as reflected along the profiles, but stand out mainly in the outcropping crust, samples where there is abundance of crandalite group phosphates. Eventually, the enrichment of HREE in the phosphatic-clayey horizon and in some samples formation of the crust was observed, probably due to churchite. The laterites show favorable economic perspectives for phosphates, titanium and rare earth elements.

Orientador: Cassio Eduardo Lima de Paiva
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Esta pesquisa procurou estabelecer uma correlação entre os valores de capacidade de suporte resultantes dos ensaios CBR (Califórnia Bearing Ratio) versus DCP (Dynamic Cone Penetrometer), realizados com o solo proveniente de vias não-pavimentadas dentro do Campus da UNICAMP, situado em Campinas, São Paulo. O Cone de Penetração Dinâmica (DCP) é caracterizado como um equipamento simples, portátil e de baixo custo, cujo ensaio revela ser praticamente não-destrutivo. Com ele é possível determinar o perfil de resistência de camadas de solo compactadas ou em seu estado natural, controlar a execução de obras viárias e avaliar estruturas de pavimentos. Uma investigação do solo através de ensaios DCP e CBR conduziu ao desenvolvimento de modelos de regressão, correlacionando a capacidade de suporte obtida através de ensaios ¿in situ¿ com o auxílio do DCP, e ensaios de laboratório utilizando o ensaio de CBR e DCP. Através das informações contidas na literatura técnica, dos procedimentos experimentais efetuados e das análises de regressão realizadas, ficou evidenciado o relacionamento entre o DCP e o CBR, validando as correlações estabelecidas e propondo modelos próprios, aumentando a confiabilidade dos resultados dos ensaios DCP para avaliação da capacidade de suporte de solos
Abstract: This research establishes a correlation among the strength or supporting values of the tests: CBR (California Bearing Ratio) versus DCP (Dynamic Cone Penetrometer), accomplished with the soil originating from no-paved roads inside of the Campus of UNICAMP. The Cone of Dynamic Penetration (DCP) it is characterized as an equipment simple, portable and of low cost, whose tests reveals to be practically no-destructive. DCP test determines the profile of resistance of soil layers compacted or in your natural state, to control the execution of road buildings and to evaluate structures of pavements. An investigation of the soil through DCP and CBR tests led to the development of regression models, correlating the strength measures obtained through in-situ tests with the aid of DCP and laboratory tests using the CBR and DCP. Through the information contained in the technical literature, of the made experimental procedures and of the regression analyses accomplished, the relationship was evidenced between DCP and CBR, validating the established correlations and proposing own models, increasing the reliability of the results of the DCP tests for determining strength values of soils
Mestrado
Transportes
Mestre em Engenharia Civil

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PADCT - Programa de Apoio ao Desenvolvimento Científico e Tecnológico
CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
Para estudar a gênese dos solos desenvolvidos sobre crostas lateríticas foram selecionados cinco perfis, localizados na região de Carajás (N5 e igarapé Bahia) e nos municípios de Paragominas (Mina de Camoaí) e Belém (balneários de Outeiro e Mosqueiro), todos no Estado do Pará. A estruturação dos cinco perfis (N5, Igarapé Bahia, Camoaí, Outeiro e Mosqueiro) permitiu individualizar quatro horizontes: crosta sã, crosta parcialmente intemperizada, crosta intemperizada e solo. A crosta sã é compacta vacuolar, constituída por óxi-hidróxidos de Fe e Al. A crosta parcialmente intemperizada compõe-se por relictos da crosta sã envolvidos por uma matriz argilosa amarelada ou avermelhada, dependendo da composição mineralógica da crosta sã. A crosta intemperizada caracteriza-se pela predominância da matriz argilosa em relação a seus relictos enquanto o solo é formado exclusivamente por material argiloso. A estruturação dos perfis mostra que a passagem da crosta sã para o solo sobreposto é gradual, havendo expansão de volume no inicio da fragmentação e posterior colapso do perfil, quando os relictos se transformam totalmente em um material terroso e microagregado. Os perfis de N5 e Igarapé Bahia são derivados a partir de urna crosta ferro-aluminosa matura. Caracterizam-se pelos teores mais elevados de caolinita e hematita na crosta e seus relictos. No solo concentram-se a gibbsita, Al-goethita e anatásio com tendência a formação de um solo inicialmente bauxítico, que passa a caolinítico em direção ao topo do perfil. No Igarapé Bahia tem-se acúmulo de quartzo no solo. Quimicamente observa--se que a modificação mineralógica leva a um decréscimo nos teores de Fe203 e 6i02 e aumento de Al203, TiO2 e PF. Os elementos-traço (V, Cr, Ni, B, Mo, Zr, Ga, Sc, Y, Mn, Cu e Pb, além de Au no perfil do igarapé Bahia) e os ETR mostram concentração de B e Zr, enquanto os demais tendem a serem diluídos da crosta para o solo. O balanço isotitânio mostra que a transformação da crosta em solo se dá por lixiviação de SiO2 e Fe2O3 nos dois perfis, enquanto o Al2O3 se enriquece no perfil de N5 e é lixiviado no perfil do Igarapé Bahia. A formação do solo de Camoaí, a partir de crosta aluminosa matura, difere dos perfis de N5 e Igarapé Bahia pela diminuição nos teores de gibbsita e aumento nos de caolinita e quartzo, enquanto os teores de hematita, goethita e anatásio, muito baixos, não tem variação significativa. Acompanhando a composição mineralógica tem-se diminuição nos teores de Al2O3 e aumento nos de SiO2, enquanto os de Fe2O3 e TiO2, muito baixos, não tem uma distribuição característica. Os elementos-traço e os ETR, com teores bem mais baixos que nos demais perfis, mostram aumento de Zr e Mn em direção ao solo e diluição dos demais elementos. Em Camoaí a transformação da crosta aluminosa em solo, segundo o balanço isotitânio, dá-se pela lixiviação de Al2O3 e enriquecimento em SiO2 e Fe2O3. Nos perfis de Outeiro e Mosqueiro, derivados de crostas lateriticas silico-ferruginosas imaturas, a formação do solo se com diminuição nos teores de hematita+goethita, de modo que no solo predominam quartzo e caolinita. Conseqüentemente tem-se decréscimo nos teores de Fe2O3 e aumento nos de SiO2 e Al2O3. A distribuição dos elementos-traça mostra, assim como em N5 e igarapé Bahia, concentração de Zr e diluição dos demais. Com base no balanço isotitânio a transformação da crosta dos perfis de Outeiro e Mosqueiro se dá pela lixiviação de Fe2O3, enquanto o SiO2 e o Al2O3 se enriquecem no perfil de Outeiro e são lixiviados no de Mosqueiro. Com base na estruturação dos perfis, na mineralogia e geoquímica, foi possível caracterizar um acentuado processo de desferrificação das crostas ferro-aluminosas e sílico-ferruginosas e de desaluminizaçâo das aluminosas, levando a geração de solos. No perfis derivados das crostas ferro-aluminosas e silico-ferruginosas tem-se a substituição da hematita por Al-goethita, uma fase intermediária onde predomina gibbsita nos perfis ferro-aluminosos e, finalmente, caolinita no topo dos dois perfis. Em todos os perfis observou-se acúmulo em quartzo. O enriquecimento em quartzo e o provável aporte externo de SiO2, via decomposição de material vegetal, levou a neoformação da caolinita a partir da gibbsita nos perfis de N5, igarapé Bahia e Camoaí. Nos perfis de Outeiro e Mosqueiro a presença de caolinita no solo deve-se ao seu enriquecimento relativo a partir da crosta. Como consequência da transformação mineralógica houve a lixiviação de ferro nos perfis de N5, igarapé Bahia, Outeiro e Mosqueiro e de alumínio no de Camoaí, além de V, Cr, Ni, Mo, Ga, Sc, Cu, Pb e ETR, forte enriquecimento em Zr e em parte de 13 e Mn em todos os perfis. As transformações que levaram à quebra no equilíbrio das crostas, a sua desagregação e cominuição, formando relictos e uma nova fase mineral argilosa, são consequências da ação da matéria orgânica, que torna o ambiente mais ácido e menos oxidante, em um processo similar ao da formação de perfis intempéricos em ambiente tropical úmido. As diferenças mineralógicas e geoquímicas observadas entre os perfis são conseqüência das variáveis composicionais das crostas que, em parte, refletem também o seu grau de maturidade. As características mineralógicas e geoquímicas dos solos nos perfis estudados permitem que eles sejam correlacionados a Argila de Belterra, podendo-se portanto admitir que a Argila de Belterra tem origem autóctone em relação as crostas lateríticas subjacentes.
With the aim of studying the genesis of soils developed on lateritic crusts, five profiles located in the region of Carajás (N5 and Igarapé Bahia procpects) as well as in Paragominas (Camoaí Mine) and Belém (Mosqueiro and Outeiro Beaches) municipalities all them located in Pará State, Brazil - have been selected. Based on the structures described in the profiles (N5, igarapé Bahia, Camoaí, Outeiro and Mosqueiro), it has been Possible to distinguish four differents horizons: fresh crust, partially-weathered crust, weathered crust and soil. The fresh crust is compact, vacuolar and composed of iron and aluminium oxyhydroxides. The partially-weathered crust is made up of fresh-crust relicts enclosed in yellowish or reddish clayey matrix, depending on the mineralogical composition of the fresh crust. The weathered crust is characterized by dominance of clayey matrix in relation to relicts, while the soil is composed exclusively of clayey material. The structures of the profiles show that the change from fresh crust to the overlying soil is gradual with volume expansion at the beginning of the fragmentat ion processes. This expansion is followed by the collapse of the profile as the relicts are entirely transformed into an earthy micro-aggregated material. The profiles of N5 and Igarapé Bahia prospects have been derived from a mature iron-aluminous crust, being characterized by the highest contents of kaolinite and hematite either in the crust or in the relícts. Gibbsite Al-goethite, anatasse and quartz are concentrated in the soil, which tends to be initially bauxitic, at the base of the profile, and to become kaolinite-rich toward the top. The mineralogical changes led to chemical modifications such as decrease in Fe2O3 and 8iO2 and increase in Al2O3, TiO2 and PF. The trace elements (V, Cr, Ni, R, Mo, Zr, Ga, Sc, Y, Mn, Cu and Pb besides Au in the profile of Igarapé Bahia) and REE's exhibit concentrations of 8 and Zr whereas the remaining ones tend to be progressively diluted from the crust toward the soil. The TiO2-mass balance shows that the transformation of the crust into soil took place by means of leaching of SiO2 and Fe2O3 in two profiles above mentioned, while Al2O2 underwent enrichment in the profile of N5 and leaching in the profile of igarapé Bahia. The soil formation from a mature aluminous crust in Camoaí differs from those described in the profile of Igarapé Bahia and of N5 in that it shows a decrease in gibbsite contents and an increase in kaolinite and quartz, whereas the verey low contents of ,hematite, goethite, and anatase do not present a characteristic distribution. The trace elements and the REE's, with contents much lower than those observed in the others profiles, show an increase in Zr and Mn toward the soil horizon and a dilution of the remaining ones. In the Camoaí, the transformation of the aluminous crust into soil, based on the TiO2-mass balance, took place through leaching of Al2O3 and enrichment in SiO2 and Fe2O3. In the profiles of Outeiro and Mosqueiro, deriveci from immature silicoferruginous lateritic crust the soil formation occurred by means of decreasing in hematite+goethite so that, in the resulting soil, quartz and kaolinite predominate. In consequence of this, a decrese in the Fe2O3 contents and an increase in SiO2 and Al2O3 have been observed in those profiles. The trace elements distribution presents, as in igarapé concentration of Zr and dilution of the remaining ones. Based on TiO2-mass balance, it could be noticed that the transformation of the crust in the profiles of Mosqueiro and Outeiro took place through leaching of Fe2O3, whereas SiO2 and Al2O3 underwent enrichment in the profile of Outeiro and Leaching in the one of Mosqueiro. On the basis of structures, mineralogical composition and geochemical data of the profiles, it has been possible to characterize an accentuated process of Fe loss in the iron-aluminous and in the silicoferruginous crust as well as Ai removal in the aluminous ones what led to soil generation. In the profiles derived from the iron-aluminous and the silicoferruginous crust, it has been observed substitution of hematite by Al-goethite, an intermediated segment - where there is predominance of gibbsite in the iron-aluminous profiles -- and presence of kaolinite at the top of both profiles. In every profiles, it has been reported quartz acumulation. The enrichment in quartz and the S1O2 being the latter likely come from externai sources -via vegetable-material decay - caused the neoformation of kaolinite from gibbsite in the profiles of N5, igarapé Bahia, and Camoaí. In the profiles of Mosqueiro and Outeiro the kaolinite presence in the soil is a consequence of its relative enrichment in the relation to the crust from which it has been derived. As a consequence of the mineralogical transformation, Fe has been leached from the profiles of N5, Igarapé Bahia, Mosqueiro, and Outeiro and Al from those of the Camoaí, as well as V, Cr, Mo, Ga, Sc, Cu, Pb and REErs. On the other hand, a strong enrichment in Zr and, in part, in 8 and Mn has been reported in every stud ied profiles. The transformations that caused the break down of the balance of the crusts, their desmantlement and comminution, forming relicts and a new clayey mineral phase, are consequence of organic matter influence which turns the environments conditions more acid and less oxidizing, in a process similar to that of weathering-profiles formation in humid tropical environments. The mineral and chemical difference observed between the profiles are consequence of compositional variation of the crusts which, in part, also reflect the degree of maturity of theirs. The mineralogical and geochemical characteristics of the soils in the investigated profiles allow us to correlate them to the Belterra Clay and, in consequence of this, to admit that Belterra Clay had an autochthonous origin in relation to the underlying lateritic crusts.

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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
Existem dois níveis de bauxitas distintos no platô Miltônia-3 localizado na Província Bauxitífera de Paragominas-PA. Estes níveis estão separados por um horizonte de laterita ferruginosa (LF) pseudopsolítica a concrecionária que marca um hiato entre dois ciclos distintos de formação do perfil bauxítico atual. As bauxitas do nível superior (2° ciclo de formação) possuem características nodulares a concrecionárias e as do nível basal (1° ciclo de formação) composto por uma bauxita concrecionária (BC) mais íntegra fisicamente somado a outro nível de bauxita mais friável com porções argilosas para a sua base (BCBA). Percebeuse tratar da Bauxita Nodular Concrecionária (BNC) localizada no nível superior, de horizonte enriquecido em gibbsita, com baixos teores de sílica reativa e ferro, teores esses muito semelhantes àqueles encontrados no horizonte do principal minério de bauxita (BC) do perfil. Em observações de campo, nas frentes de lavra e nos testemunhos de sondagem constatou-se que esta BNC é uma gradação do horizonte de Bauxita Nodular (BN) acima. Essa gradação é observada pelo aumento do tamanho dos nódulos bauxíticos, onde os seus pseudopisólitos Fe-gibbsíticos intercrescem por coalescência, diminuindo os teores de ferro e sílica disseminados marcados pela mudança de coloração, passando de amarelo-lilás, até atingir uma coloração vermelho-alaranjado a ocre, à medida que se avança na profundidade. Nota-se também marcante diminuição até o completo desaparecimento dos pseudopisólitos Al-ferruginosos, além da diminuição do volume de argila gibsítica-caulinítica neste nível. Com base nos estudos como petrografia macroscópica e microscópica, MEV/EDS, DRX e análises químicas, além de Análise de Componentes Principal (ACP) e estatística descritiva, foram desenvolvidas duas propostas de modelos de evolução sobre a gênese do nível superior de bauxitas nodulares deste depósito laterítico-bauxítico, considerando: Modelo (1) - Origem a partir da degradação das bauxitas originais (1º Ciclo), relacionadas a um 2º Ciclo de Lateritização que consiste na preexistência da bauxita matura (BC), sobreposto pela LF, que foi recoberto por “Argila de Belterra”. Este novo nível nodular imposto (BN), ocorre pelo processo de coalescência onde houve a junção da fase aluminosa residual, resultante da migração do Fe e Si em solução para fora deste nível e pela migração do Al dos níveis vizinhos acima do capeamento (CAP) e abaixo deste de LF e BC, formando e concentrando em larga escala a gibbsita preferencialmente e secundariamente a caulinita. Com a contínua evolução deste nível de BN, observa-se um amadurecimento da porção basal deste nível, formando a BNC cujos nódulos estão intercrescidos, se conectando localmente, consumindo os níveis vizinhos acima da BN e os níveis abaixo de LF e BC, até o total consumo destes; Modelo (2) - Sua origem a partir de um 2º Ciclo de Lateritização, porém a partir de uma deposição sedimentar posterior sobre o perfil laterítico do 1º Ciclo. Com a exposição de uma rocha fonte como um plúton granitóide (Granito Cantão, Japiim, Jonasa, Ourém e Ney Peixoto do Neoproterozóico), gnaisse (embasamento cristalino arqueano) ou sedimentos siliciclásticos (Formações Itapecuru e Ipixuna do Cretáceo Superior), cuja degradação intempérica possibilitou a geração de sedimentos de natureza argilosa preferencialmente caulinítica durante o Paleógeno até o início do Oligoceno?. Houve a migração de Fe, Si, Ca, Na, etc. para fora deste nível, preservando e concentrando in situ o Al e O, além do Si residual. O processo de coalescência permitiu a junção da fase aluminosa residual, concentrando preferencialmente gibbsita e secundariamente caulinita, fechando o primeiro ciclo de formação de bauxita. Em seguida houve um soerguimento regional, seguido por processos erosivos que possibilitaram a exposição deste perfil bauxítico anteriormente formado, sob clima sazonal, com abundância de água meteórica e intensa insolação se intercalando, onde se desenvolveu a LF, de ocorrência regional marcando um hiato entre os ciclos de formação destas bauxitas. Nova movimentação regional de rebaixamento, que possibilitou a deposição de sedimentos de origem siliciclástica, que serviram de rocha fonte para um novo ciclo de formação de bauxita durante o Mioceno Superior. Podem ser as mesmas rochas cuja degradação física e química forneceram os sedimentos para o 1° ciclo de formação de bauxitas. Repetindo o processo de coalescência da fase aluminosa residual, com o desenvolvimento em larga escala preferencialmente da gibbsita e secundariamente caulinita, fechando o segundo ciclo de formação de BN e BNC.
There are two distinct levels of bauxites on the Miltônia-3 plateau located at the Bauxite Province of Paragominas-PA. These levels are separated by a pseudopsolitic to concretionary ferruginous laterite (FL) horizon, marking a hiatus between two distinct cycles of the current bauxite profile formation. The bauxites of the upper level (2nd cycle of formation) have nodular to concrete characteristics whereas those of the basal level (1st cycle of formation) are composed by a more physically complete concrete bauxite (CB) added by another level of a more friable bauxite with clayey portions for its base (concrete bauxite with clayey bauxite - CBCB). It was noticeable the CNB located at the upper level of gibbsite-enriched horizon with low reactive silica and iron contents, which are very similar to those found on the horizon of the main bauxite ore (CB) of the profile. In field observations, on the survey fronts and in the drill holes it was found that this CNB is a gradation of the above Nodular Bauxite (NB) horizon. This gradation is observed by the increase in the size of the bauxite nodules, where their Fe-gibbsite pseudopsolites grows up by coalescence, decreasing the diffused iron and silica contents marked by the change in color from lilac-yellow to a red-orange color, to ocher, in higher depths. It is also noticeable a decrease until the complete disappearance of the Al-ferruginous pseudopsolites, in addition to the decrease of the volume of gibsytic-kaolinite clay at this level. Based on this study using macroscopic and microscopic petrography, SEM/EDS, XRD and chemical analysis, as well as Principal Component Analysis (PCA) and descriptive statistics, two evolution model proposals were developed on the genesis of the upper level of nodular bauxites of this lateritic-bauxite deposit, considering: Model (1) - Origin from the degradation of the original bauxites (1st Cycle), related to a 2nd Lateritization Cycle which consists of the preexistence of mature bauxite (CB), overlapped by FL, which was covered by "Belterra Clay". This new nodular level (NB) occurs through the coalescence process whereby the residual aluminous phase junction occurred, resulting from the migration of Fe and Si in solution out of this level and by the migration of the neighboring levels above the clayey overburden (CAP) and below that of FL and CB, forming and concentrating large scale gibbsitepreferably and secondarily to kaolinite. With the continuous evolution of this level of NB, a maturation of the basal portion of this level is observed, forming the CNB whose nodules are interincreased, connecting locally, consuming neighboring levels above NB and levels below FL and CB, up to the total consumption of these; Model (2) - Its origin from a 2nd Lateritization Cycle, however from a later sedimentary deposition on the lateritic profile of the 1st Cycle. With the exposure of a source rock as a granitoid pluton (Cantão, Japiim, Jonasa, Ourém and Ney Peixoto of Neoproterozoic granites), gneiss (Archaean crystalline basement) or siliciclastic sediments (Itapecuru and Ipixuna Formations of the Upper Cretaceous), whose weathering degradation made it possible the generation of sediments of clayey nature preferentially kaolinite during the Paleogene until the beginning of the Oligocene. Migration of Fe, Si, Ca, Na, etc. occurred outside this level, preserving and concentrating the Al and O in situ, in addition to the residual Si. The process of coalescence allowed for the addition of the residual aluminous phase, preferentially concentrating the gibbsite and secondarily kaolinite, closing the first cycle of bauxite formation. Thereafter, there was a regional upwelling, followed by erosive processes that allowed for the exposure of this previously formed bauxite profile, under a seasonal climate, with an abundance of meteoric water and intense intercalated insolation, where the FL developed, of regional occurrence marking a hiatus between the formation cycles of these bauxites. New regional retraction movement, which allowed for the deposition of sediments of siliciclastic origin, which served as source rock for a new bauxite formation cycle during the Upper Miocene. They may be the same rocks from which physical and chemical degradation provided sediments for the 1st cycle of bauxite formation. Repeating the coalescence process of the residual aluminous phase, with the large scale development preferably of the gibbsite and secondarily kaolinite, closing the second cycle of NB and CNB formation.

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O estudo sobre a evolução mineralógica e geoquímica das crostas lateríticas e dos sedimentos sobrepostos na estrutura de Seis Lagos (Amazonas), foi baseado em amostras de crostas lateríticas superficiais e três furos de sondagem. Na caracterização química dos materiais estudados foram empregados métodos clássicos e espectroanalíticos. Na caracterização mineralógica foi utilizado difração de raios-X, microscopia ótica, espectroscopia no infravermelho e termogravimetria (ATD e ATG). Foram efetuadas análises por sistema dispersivo de energia (EDS), que foram aplicados nos estudos micromorfológicos das crostas e sedimentos da Bacia Esperança. Nas amostras de siderita foram determinados os isótopos de 13C e 18O e razões isotópicas 87Sr/86Sr. Na tentativa de datar as amostras totais e siderita da brecha carbonática, foi utilizado o método Rb/Sr. As características texturais, mineralógicas e geoquímicas observadas nas crostas superficiais e do perfil do furo 1, mostraram origem laterítica para esses materiais. A assinatura carbonatítica das crostas foi indicada pelos minerais como ilmenorutilo, Nb-rutilo, Nb-brookita, pirocloro e monazita, típicos de carbonatitos e rochas associadas e resistentes aos processos lateríticos e pelos teores elevados e anômalos de Nb, ETR, também de Ba, Mn, Th, Co, Zr, Sc, V, Mo e Be. O perfil do furo 3, que se apresentou estruturado em horizontes bem distintos, característicos de perfil laterítico, mostrou composição química-mineralógica indicativa de derivação laterítica a partir de rochas aluminosilicatadas pobres em ferro, como as encaixantes (granitos e gnaisses) de Seis Lagos. Os sedimentos da bacia Esperança mostraram que tiveram como área fonte os diferentes horizontes dos perfis lateríticos e grande contribuição orgânica vegetal e animal. Os materiais que constituiram a brecha carbonática, foram provenientes das crostas ferruginosas lateríticas dada a semelhança geoquímica entre esses materiais, a presença dos minerais resistatos da crosta ferruginosa e de minerais típicos de ambiente sedimentar-diagenético, essencialmente ferrosos como pirita e siderita. A argila carbonosa demonstrou ter como área fonte os horizontes argilosos lateríticos como aqueles do perfil do furo 3 e, que a deposição desta camada ocorreu em momento de menor subsidência da bacia Esperança, quando as crostas ferruginosas que estavam situadas em níveis mais elevados tinham sido erodidas e os horizontes argilosos estavam expostos. A camada de sapropelito indicou a instalação de um ambiente ácido redutor prolongado, dada pela sua elevada espessura, que sua constituição química-mineralógica foi contribuída também pelos lateritos, principalmente, dos horizontes argilosos, e que a formação de pirita foi a mesma daquela da brecha carbonática. A camada de argila creme-solo foi constituída também dos horizontes argilosos, como indicou sua composição química-mineralógica. Na brecha carbonática da seqüência litológica da bacia Esperança não foram encontrados minerais típicos de carbonatitos, a exceção dos resistatos (ilmenorutilo, Nb-rutilo, Nb-brokita, pirocloro e monazita) e siderita não comuns nessas rochas, mas minerais lateríticos como gibbsita e grupo da crandalita. As filiações geoquímicas encontradas entre crostas e brecha carbonática e argilas/sapropelito e horizontes argilosos lateríticos foram notáveis. O não alinhamento dos pontos analíticos no diagrama isocrônico (87Rb/86Sr vs. 87Sr/86Sr) obtidos tanto das amostras totais como de cristais de siderita da brecha carbonática não foram compatíveis com rochas homogêneas, como seriam esperados para carbonatitos, ao contrário do espesso pacote sedimentar. Os resultados mineralógicos, geoquímicos e isotópicos demonstraram que a brecha carbonática não corresponde à rocha carbonatítica, e que os sedimentos da bacia Esperança incluindo a brecha carbonática tiveram como área fonte principal os diferentes horizontes dos perfis lateríticos, onde a crosta ferruginosa foi a fonte de grande parte dos sedimentos da base da coluna (base da bacia, provavelmente) e os horizontes argilosos das camadas superiores. Isso permitiu que em toda a extensão da coluna, fosse transferida a assinatura geoquímica da fonte primária geradora dos lateritos que foram rochas carbonatiticas, e preservada nos lateritos.
The study of the mineralogical and geochemical evolution of the lateritic crusts and the overlying sediment in the structure of Seis Lagos (Amazonas State) has been based on the analyses of samples from the surface lateritic crusts and from three boreholes as well. In the chemical characterization of the examined material, it has been used both classic and spectroanalytic methods, while in the mineralogical characterization, x-ray diffraction, optical microscopy, infrared spectroscopy and thermogravimetry (DTA and DTG) have been employed. Energy dispersive system analyses (EDS) have been performed and applied to the micromorphologic study of the crusts and sediments from the Esperança Basin. In siderite samples, it has been determined 13C and 18O isotopic contents as well as the 87Sr/86Sr isotopic ratios. The Rb/Sr method has been used in an attempt to date whole samples and siderites from the carbonatic breccias. The textural, mineralogical and geochemical features observed, both in the surface crusts and in the profile of the borehole number 1, point to a lateritic origen for those materials. The carbonatitic signature of the crusts is indicated by typical minerals of carbonatites and associated rocks such as ilmenorutile, Nb-rutile, Nb-brookite, pyrochlore and monazite, which are resistant to lateritic processes; by high and anomalous contents of Nb, REE, as well as, Mn, Th, Co, Zr, Sc, V, Mo and Be. The profile of the borehole number 3 is arranged in well distinct horizons, what is characteristic of lateritic profiles, shows chemical and mineralogical compositions indicative of a lateritic derivation from aluminosilicatic iron-poor rocks, as those of the wall rocks (granites and gneisses) of Seis Lagos. The sediments of the Esperança Basin show evidence of being derived from the different horizons which make up the lateritic profiles, with a significant vegetable- and animal-derived organic contribution. The materials which constitute the carbonatic breccia are thought to be originated from lateritic ferruginous crust due to the existing geochemical similarities among them, to the presence of resistate minerais of the ferruginous crust and to the presence of essentially iron-bearing minerais, typical of sedimentary-diagenetic environment, such as pyrite and siderite. The carbonaceous clay proved to be derived from lateritic clayey horizons, as those of the profile of the borehole 3, and the deposition of this layer took place in a moment of lower subsidence rate in the Esperança Basin, when the ferruginous crust, positioned at higher levels, were being eroded and the cayey horizons were exposed. The sapropelite layer indicates, considering its large thickness, that a development of a long-lasting acid and reducing environment might have taken place; its chemical and mineralogical composition received contributions from latentes, mainly from the clayey horizons; and the pyrite formation has been the sanie of that of the carbonatic breccia. The beige-colored clay bed, as it is indicated by its chemical and mineralogical composition, was also formed by clayey-horizons material. In the carbonatic breccia of the Esperança Basin, typical caxbonatite minerals have not been found, except for the resistates (ilmenorutile, Nb-rutile, Nb-brookite, pyrochlore and monazite) and siderite, where the last one is not a common constituent of those rocks. Lateritic minerals, however, such as gibbsite and those of the crandallite group have been found. The geochemical filiation reported among crusts, carbonatic breccias, clay/sapropelite and clayey lateritic horizons is noteworthy. The nonalignment of the points plotted in isochronic diagram (87Rb/86Sr vs. "Sr/"Sr), obtained either from the whole sample or the individual siderite analyses of the carbonatic breccia are not compatible with homogenous rocks, as it would be expected for carbonatites, although they are with the thick sedimentary pile. The mineralogical, geochemical and isotopic data demonstrate that the carbonatic breccia composition does not correspond to that of the carbonatites and thus the sediments of the Esperança Basin, including the carbonatic breccia, might have had the various horizons of the lateritic profiles as their source, where the ferruginous crust might have largely been the source for the sediments of the base of column (probably the basal portion of the basin) as well as the clayey horizons of the upper beds might have been. This made possible that, along all the extension of the stratigraphic column, the geochemical signature of the carbonatitic source rock, from which the laterites were generated, was transferred to the sedimentary rocks as well as it was also preserved in the laterites.

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DAAD - Serviço Alemão de Intercâmbio Acadêmico / Deutscher Akademischer Austauschdiens
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
FINEP - Financiadora de Estudos e Projetos
A mina Igarapé Bahia e o prospecto Águas Claras são exemplos de mineralizações de ouro supergênico relacionados a gossans e lateritos. Ambas as áreas estão situadas na região de Carajás, Estado do Pará, pertencem a Companhia Vale do Rio Doce e foram pesquisadas pela Docegeo. Neste trabalho foram estudados a mineralogia e a geoquímica dos perfis laterito-gossânicos dessas duas áreas, com ênfase para a distribuição do ouro e outros elementos associados. As duas áreas em questão apresentam estilos de mineralização primária semelhantes e dentro do mesmo contexto geológico regional, a saber, ouro associado a zonas de sulfetos maciços ou disseminados, ligados a processos de alteração hidrotermal em zonas de cisalhamento, cujas rochas hospedeiras são seqüências metavulcano-sedimentares do Arqueano-Proterozóico. Os produtos supergênicos são divididos em dois grupos distintos: os do sistema gossânico e os do sistema laterítico, onde foi evidenciada a superposição do último sistema sobre o primeiro. Na descrição dos perfis supergênicos, através de amostras e informações de superfície e sub-superficie, os seguintes horizontes e zonas foram caracterizados, da base para o topo: (1) no sistema gossânico: zona de sulfetos primários, zona de cementação e espessa zona de oxidação; (2) no sistema laterítico: crosta lateritica com fragmentos dos gossans, crosta laterítica desmantelada ou linhas de pedras e latossolos. O perfil laterítico se desenvolveu sobre gossans pré-existentes, com obliteração das suas feições originais e promovendo remobilização química e física do ouro e dos outros elementos. No quadro geomorfólogico atual, a área Igarapé Bahia apresenta essa estruturação completa, enquanto que na área Águas Claras, o perfil laterítico sobre os corpos mineralizados foi truncado e os gossans estão aflorantes. A composição mineralógica da porção superior dos gossans e dos lateritos é essencialmente à hematita, goethita (com teores variáveis de Al), maghemita, gibbsita, caulinita e quartzo, em diferentes proporções. Nos gossans é nítido o domínio da hematita sobre os demais minerais. Nas porções mais profundas dos gossans, em direção a zona de sulfetos primários, foram identificados: malaquita, cuprita e cobre nativo, predominantemente, e associados a hematita, além de azurita, crisocola e quartzo; na zona de sulfetos primários observou-se uma paragênese um pouco distinta, entre as duas áreas. Em Igarapé Bahia dominam: calcopirita, magnetita, clorita, siderita e quartzo, enquanto em Águas Claras foram descritos: calcopirita, pirita, arsenopirita, cobaltita, magnetita, quartzo, wolframita e turmalina. O ouro primário ocorre finamente disseminado, incluso nos sulfetos, apresentando diferentes graus de pureza. Na área Águas Claras, ocorre associado a uma grande variedade de teluretos de Bi, Ag, Pb e Bi nativo. Ainda nesta área, turmalina (dravita) e wolframita (do tipo ferberita) são importantes minerais acessórios, comportando-se como resistatos, durante o desenvolvimento dos perfis, enriquecendo-se nos gossans e nas crostas, na forma de agregados centimétricos, e servindo como importantes guias na prospecção desses corpos. A composição química dos perfis, em termos dos elementos maiores, é caracterizada por teores extremamente elevados de Fe nos gossans, que diminuem, progressivamente, em direção aos latossolos, e inversamente, Si, Al, Ti e H₂O (perda ao fogo), enriquecendo-se para o topo dos perfis. Cálcio, Mg, Na e K estão completamente empobrecidos na maioria das amostras estudadas. Em relação aos elementos-traço, as associações geoquímicas são bastante variáveis, entre os perfis das duas áreas, refletindo, fundamentalmente, as variações químico-mineralógicas das zonas primárias. Nos corpos gossânicos mineralizados, as seguintes assinaturas geoquímicas foram caracterizadas: Au, Cu e Mo, na área Igarapé Bahia; e Au, Cu, As, B, W, Sn e Bi, na área Aguas Claras. Diferentes partículas de Au de diversos pontos dos perfis, associadas a sulfetos, veios de quartzo, gossans, crostas lateríticas e latossolos foram observadas ao Microscopio Eletrônico de Varredura e analisadas com o Sistema de Energia Dispersiva, com grandes variações observadas, em termos da morfologia e da composição química das mesmas. Prata, Pt, Pd, Fe e Cu foram freqüentemente encontrados nas análises, onde os teores de Ag variavam de menos de 1% até a composição do electrum. As partículas estudadas foram divididas em: (1) Partículas de ouro primárias (associadas aos sulfetos primários); e (2) Partículas de Au secundárias ou supergênicas, associadas aos gossans, crostas lateriticas e latossolos, sendo essas últimas classificadas como (2.1) residuais, aquelas, em geral, com mais de 30 gm de diâmetro médio, núcleo primário e bordas lixiviadas em Ag; e (2.2) autigênicas ou neo-formadas, de elevada pureza, e extremamente diminutas (< 5 pm), via de regra na periferia dos grãos maiores, residuais. Em todas as partículas de ouro relacionadas aos perfis laterito-gossânicos estudadas, as formas e os contatos delas com os principais minerais hospedeiros, goethita e hematita, indicam uma cristalização contemporânea do ouro com esses minerais. Os resultados obtidos levaram a interpretação do desenvolvimento dos perfis laterito-gossânicos em quatro fases principais, de abrangência regional, onde cada uma dessas fases desempenhou um importante papel na redistribuição do ouro: A fase I, denominada de Fase de formação dos gossans, está relacionada ao desenvolvimento dos gossans, em condições climáticas tropicais semi-áridas a sazonalmente úmido (savana), e considerados neste trabalho como anteriores ao Terciário Inferior. Durante essa fase, o ouro foi remobilizado das zonas sulfetadas através, principalmente, de soluções ou complexos Au-tiossulfatados, reprecipitando na zona oxidada, junto com os óxidos 'e hidróxidos de ferro. As partículas neoformadas, resultantes, apresentam granulação fina e pureza média (teor algo elevado de Ag); A fase II foi denominada de lateritização Matura e está relacionada ao marcante processo de intemperismo laterítico que aconteceu na região Amazónica, como um todo, durante o Terciário Inferior. Perfis lateríticos maturos se formaram, indistintamente, sobre os gossans, e sobre as suas encaixantes, com o desenvolvimento de crosta laterítica brechóide contendo fragmentos dos gossans. Com essa superposição de processos, o sistema gossânico foi aberto, e uma nova remobilização aconteceu, dessa vez em condições mais oxidantes e, certamente, com uma importante atuação dos complexos orgânicos, cianetos e complexos aquo-hidrolisados na mobilização do ouro. Além da mobilização química desse elemento, importante dispersão fisica aconteceu, com o início da formação da feição morfológica tipo "cogumelo". Na fase três, descrita neste trabalho como pós-lateritização Matura, assiste-se a uma retomada de condições favoráveis a lateritização, semelhantes as da fase anterior, com o intemperismo dos perfis lateríticos maturos, a partir do Mioceno Médio. Os principais produtos deste período são os latossolos da área Igarapé Bahia. Com a nova abertura de sistema, o ouro é novamente remobilizado, através dos mesmos mecanismos fisico-químicos e com a atividade orgânica desempenhando um papel mais intenso em relação a fase anterior, com forte dispersão fisica, no sentido do espalhamento ou abertura dos halos de dispersão do Au e diminuição do sinal deste elemento. A intensidade deste ciclo de lateritização foi menor que o do Terciário Inferior, já que a mudança para condições mais secas no Plioceno e início do Pleistoceno, levou a uma intensa denudação da paisagem, com a erosão e truncamento dos perfis na área Águas Claras e exposição dos gossans. Importantes depósitos coluvionares (na área Águas Claras) e aluvionares auríferos, a nível regional, são relacionados a esse período. A fase IV estão associados todos os processos de destruição/intemperismo do quadro geomorfológico estabelecido no final da fase III, em função das condições, predominantemente, úmidas, que passaram a prevalecer a partir do final do Pleistoceno e início do Holoceno, dando origem a novos níveis de latossolos, linhas de pedras, colúvios e aluviões.
The Igarapé Bahia mine and the Águas Claras prospect are examples of supergene gold mineralization in gossans and latentes. They are located in the Carajás mining district, Pará state, Northern Brazil. These areas belong to Vale do Rio Doce Company and all the exploration programs were conducted by DOCEGEO. In this work, mineralogical and geochemical studies were performed in the weathering profiles of both areas focussing on the behaviour and distribution of gold and associated elements. The two areas exhibit similar primary geological context, with gold-bearing sulphide zones associated with shear zones and intense hydrothermal alteration, related to Archaean to Proterozoic metavolcano-sedimentary sequences. The supergene products are divided in two main groups: The gossan system and the lateritic system with evidences of superimposition of the latter on the former. The profiles were studied after different surface and subsurface sampling. The following horizons and zones were described, from base to top: (1) in the gossan system: primary sulphide zone, secondary sulphide zone and a thick oxidation zone; (2) in the latente system: a brecciated lateritic iron crust, a dismantled iron crust or stone-lines and latossols. The lateritic iron crust developed over the pre-existing gossans, resulting in a complete obliteration of the primary textures and structures and promoting a new remobilization of gold and other elements. This structuration can be observed today in the Igarapé Bahia area while at Águas Claras the latente profile over the mineralized bodies was truncated and exposing the gossans. The mineralogical composition of gossans and latentes is mainly represented by hematite, and variable amounts of goethite, Al-goethite, maghemite, gibbsite, kaolinite and quartz. Hematite predominates in the gossans and goethite becomes progressively enriched toward the latentes. In the deepest parts of the gossans the following minerais were identified: malachite, cuprite and native copper, mainly associated with hematite, besides azurite, chrysocolla and quartz; the Aguas Claras area presents a broader paragenesis in the primary sulphide zone, that includes: chalcopyrite, pyrite, arsenopyrite, cobaltite, quartz, magnetite, wolframite and tourmaline. Primary gold occur as diminute particles finelly disseminated in the sulphides and with different compositions in the Au-Ag alloy. In the Águas Claras area it occurs associated with a wide range of Bi-, Ag- and Pb-tellurides, besides native bismut. Tourmaline (dravite) and wolframite (ferberite) also occur as important accessory minerais, both in the primary and secondary environment. In the gossans they occur as centimetric cumulates, acting as important guides for gossans identification. Major element geochemistry of the profiles is mainly characterized by very high iron contents in the gossans, that progressively diminish toward the latossols. On the oder hand, the contents of Si, Al, Ti and LOI increase toward the top of the profiles. Calcium, Mg, Na e K are completely depleted in the gossans and laterites. Geochemical associations of trace elements are variable for the two areas and reflect mainly the chemical and mineralogical variations from the primary zones. In the mineralized bodies (gossans + iron crust) the following geochemical signatures were characterized: Au, Cu and Mo, for the Igarapé Bahia area; and Au, Cu, As, B, W, Sn and Bi, for the Águas Claras area. From the various horizons and zones of the profiles, different gold particles were separated and analised by Scanning Electron Microscope with Energy Dispersive System. Strong variations were described in terms of morphology and chemical compositions in the Au-Ag alloy. Silver, Pt, Pd, Fe e Cu were frequently detected, where Ag contents range from less than 1% to more than 25%. The studied grains were divided in two groups: (1) Primary particles associated with primary sulphides; and (2) Secondary or supergene particies, associated with gossans, latentes and latosols. These were further divided in two groups: (2.1) residuais particles, generally with more than 30 grn of mean diameter and exhibiting a primary core with Ag-depleted rims; and (2.2) authigenic or neoformed particles, which are extremely fine (< 5 1.un) and of very high fineness, frequently associated to the coarser and residual grains. The results obtained allowed us to interpret the supergene evolution of the area in four main phases, each one associated with or related to a major period of gold remobilization: Phase I - Gossan formation: related to the development of gossanic bodies in tropical climatic conditions which ranged from semi-arid to seasonally humid (savannas). In this work this is considered as prior to Lower Tertiary. During this phase, gold was remobilized from lower primary zones through thiosulphates complexes and reprecipited in the upper oxidized zones associated with iron oxy-hydroxides. The reprecipitated gold is fine-grained and of medium fineness. Phase Mature Lateritization: related to the broad lateritic weathering processes that took place in the whole Amazon region during Early Tertiary times. Mature lateritic profiles were formed above the gossans and their wall-rocks, with the development of a brecciated lateritic iron crust that includes gossans fragmenta. The gossan system was obviously oppened during this phase resulting in physical and chemical dispersion of gold. The role of organic matter related to biological activity was very important in the chemical remobilization of gold. Phase 111 - Post-Mature lateritization: related to all weathering processes that took place in the region after the establishment of the lateritic profiles during the trànsition Upper Oligocene-Middle Miocene. The main supergene products of this phase are the upper latosols of the Igarapé Bahia area. After the weathering of gold-bearing lateritic crusts, this element is once again remobilized following the same chemical mechanisms of phase II, but under increasing biological activity. This resulted in an intensive physical dispersion, broadening of geochemical haloes and weakening of gold signals. This new lateritic cycle was less intensive as compared to the previous one. It took place in the transition to more and conditions during the Plio-Pleistocene, resulting in an intense denudation of the landscape with erosion, truncation and exposure of the Aguas Claras gossans. Widespread gold-bearing coluvium (in the Águas Claras arca) and Placer deposits are inportant supergene products regionally related to this phase. Ali the weathering processes that took place after the establisment of the landscape in the end of phase III are considered in this work as phase IV. These are related to prevailing humid conditions that become dominant after the end of Pleistocene and during the Holocene, giving rise to new latosols, stone-lines, coluvium and aluviums.

Falconbridge Dominicana C. Por A. operating in the Dominican Republic produces nickel as an iron-nickel alloy from laterite ore. Material that is rejected from their mining operations due to its incompatible chemistry is currently being stockpiled against mine depletion. Recent interest in recuperating nickel from this reject material led to the examination of the suitability of carbothermic reduction followed by magnetic separation for nickel recovery from this reject ore. Five parameters were considered in a Design of Experiment framework, namely: heating time; temperature; material type, coke addition and oxygen partial pressure. Magnetic separation was conducted with a Davis Tube and a low intensity hand magnet.
It was found that this reject material can successfully be treated using a carbothermic reduction process to produce 50 to 75 mum diameter metallic components within a gangue matrix. The recovery of nickel ranged from 61.7% to 21.9% to 16.4% in the high, low and non magnetic fractions, respectively, separated from the reduced material. The grade of nickel ranged from 1.97 wt% Ni to 1.58% to 0.75 wt% Ni in the high, low and non magnetic fractions, respectively.
Heating temperature had the greatest positive influence on the performance of the process followed by material type and heating time. Oxygen activity and coke addition were seen not to influence the performance. The Boudouard reaction was considered to be the rate controlling step and a maximum possible operating temperature was considered to depend on the physical properties of the material, specifically the softening temperature.

This article presents nano composite TiO2.Fe2O3/laterite materials, which were successfully prepared by hydrometallurgical method. The materials were modified using urea as the nitrogen source. The particles size of the materials is from 20-30 nanometers. The obtained materials can not only absorb arsenic compounds but also enhance the ability of converting As (III) or As (V) into Aso, which is removed from solution. Arsenic removal efficiency of these materials is high. Using sunlight in a hydraulic retention time, about 180 minutes, the arsenic value at the inflow was about 10 mg/L but the outflow was negligible. Covering TiO2.Fe2O3 nano on laterite have brought high economical efficiency, on one hand, it saved material and on the other hand, it can be continuously operated without the centrifugal separation of the nano material
Bài báo này giới thiệu về phương pháp điều chế vật liệu nano TiO2.Fe2O3 biến tính nitơ được phủtrên đá ong bằng phương pháp thủy luyện. Vật liệu nano thu được có kích thước 20-30 nm. Vật liệu thu được không những có khả năng hấp phụ các hợp chất của asen mà còn có khả năng khử As (III) hoặc As (V) thành Asokhi được chiếu sáng. Sử dụng ánh sáng mặt trời chiếu vào hệ thống xử lý trong thời gian 180 phút có thể loại bỏ được gần như hoàn toàn asen ra khỏi nước mặc dù hàm lượng đầu vào là 10 mg/l. Việc phủ vật liệu TiO2.Fe2O3 nano lên đá ong đã mang lại hiệu quả kinh tế cao, một mặt nó tiết kiệm được vật liệu, mặt khác, vật liệu có thể sử dụng một cách liên tục mà không cần phải tách bằng phương pháp ly tâm

This study was carried out to evaluate the sorption capacity of Pb, As, Cd, Zn, and Mn by laterite from Tam Duong District (Vinh Phuc Province) and Thach That District (Hanoi City). Laterite samples were exposed to different initial concentrations of heavy metals in solutions (2.5, 5.0, 10, 20, and 50 mg/l) at pH = 5.5 during 24 hours. The results demonstrated that sorption capacity of heavy metals was in the following order: Pb> As> Cd> Zn>Mn. The highest sorption capacity of Pb, As, Cd, Zn, and Mn of laterite from Tam Duong was 1553, 756, 397, 281, and 143 mg/kg, respectively and the highest removal efficiency was 94, 76, 70, 56 and 37%. The results indicated that laterite from Tam Duong District showed lower sorption capacity than that from Thach That District. The disparity sorption capacity of Pb, As, Cd, Zn, Mn between laterite from Thach That and Tam Duong was 10.3–11.6, 11.9–17.9, 11.5–13.7, 9.5–17.6, and 11.1–14.3%, respectively. Laterites from Tam Duong and Thach That are a promising environmental material which can be used in the removal of heavy metals from wastewater.
Nghiên cứu này được thực hiện nhằm đánh giá khả năng hấp phụ Pb, As, Cd, Zn, và Mn bởi laterit đá ong khu vực huyện Tam Dương (Vĩnh Phúc) và huyện Thạch Thất (Hà Nội). Mẫu đá ong được tiến hành thí nghiệm trong các dung dịch có hàm lượng kim loại nặng ban đầu khác nhau (2,5; 5,0; 10; 20 và 50 mg/l) tại pH=5,5 trong 24 giờ. Kết quả nghiên cứu cho thấy mức độ hấp phụ kim loại nặng bởi laterit đá ong lần lượt là Pb> As> Cd> Zn>Mn. Dung lượng hấp phụ Pb, As, Cd, Zn và Mn cao nhất của laterit Tam Dương lần lượt là 1553, 756, 397, 281 và 143 mg/kg và hiệu suất hấp phụ cao nhất lần lượt là 94, 76, 70, 56 và 37%. Dung lượng hấp phụ kim loại nặng của laterit huyện Tam Dương thấp hơn khu vực huyện Thạch Thất. Sự chênh lệch về dung lượng hấp phụ Pb, As, Cd, Zn và Mn giữa laterit Thạch Thất và laterit Tam Dương lần lượt là 10,3–11,6; 11,9–17,9; 11,5– 13,7; 9,5–17,6 và 11,1–14,3%. Kết quả nghiên cứu bước đầu cho thấy đá ong khu vực huyện Tam Dương và Thạch Thất là vật liệu hấp phụ tiềm năng phục vụ ứng dụng trong xử lý nước thải bị nhiễm kim loại nặng.

Arsenic (As) contaminated groundwater has been a major concern due to the negative impacts to exposed people. This research was conducted to assess and compare the removal efficiency of As from groundwater by laterite, sand, and ash. The experiment was carried out in 14 days in a household scale in Son Dong commune, Hoai Duc district, Ha Noi. Groundwater was pumped directly from a well and flowed through 20 cm (diameter) x 80 cm (length) columns. The initial As concentration in groundwater was 526 μg/L decreasing to an average of 189, 192 and 154 μg/L after being filtrated using sand, ash, and laterite, respectively. Average removal efficiency of sand, ash and laterite during the experiment was 63.3, 63.9, and 70.5%, respectively. Laterite had higher As removal efficiency may be due to higher content of goethite and kaolinite in this sorbent which resulted in better adsorption of As. The concentrations of As in the outflow water were higher than the allowable limit set by the national technical regulation on drinking water quality (QCVN 01:2009/BYT). Therefore, it requires higher volume of sorbents or additional treatment technologies for removal of As from groundwater.
Ô nhiễm asen (As) trong nước ngầm hiện nay là một vấn đề cấp bách đối với xã hội bởi những rủi ro tiềm ẩn với sức khoẻ con người. Nghiên cứu được thực hiện nhằm đánh giá và so sánh khả năng hấp phụ As trong nước ngầm của đá ong, cát và tro. Thí nghiệm được tiến hành trong vòng 14 ngày đặt tại một hộ gia đình có nguồn nước ngầm bị ô nhiễm As thuộc xã Sơn Đồng, huyện Hoài Đức, Hà Nội. Nước ngầm được bơm từ giếng và chảy qua các cột đựng vật liệu có đường kính và chiều dài lần lượt là 20 cm và 80 cm. Nồng độ As ban đầu là 526 μg/L đã giảm xuống còn 189, 192 và 154 μg/L sau khi lọc bằng cát, tro và đá ong. Hiệu suất xử lý As trung bình của cát, tro và đá ong lần lượt là 63,3, 63,9 và 70,5 μg/L. Đá ong xử lý As tốt hơn có thể do hàm lượng goethit và kaolinit cao hơn trong vật liệu hấp phụ này dẫn đến khả năng hấp phụ As tốt hơn. Tuy nhiên hàm lượng As trong nước đầu ra vẫn chưa đạt quy chuẩn cho nước uống (QCVN 01:2009/BYT). Do đó, cần tăng thêm lượng vật liệu hoặc kết hợp với các phương pháp khác để xử lý As hiệu quả hơn.

Embankments are key elements in the infrastructural development of structures such as dams, bridges, and roads. Residual soils are generally used as fills in the construction of embankments in areas were residual soils such as laterite is the dominant soil types. Laterite soils have the characteristics of losing its shear strength with time and in fully saturated conditions and its properties varies from region to region. The soil property is influenced by the chemical composition and the environment. The binding agent iron oxide in such soils changes its composition with time and in the presence of moisture. Sudden failures of embankments founded of laterite soils which were, otherwise, checked and found to be safe with high factor of safety, have been observed. This study is performed to investigate the stability of embankments with sudden loss of strength with time and when it is fully saturated. The research includes an investigation of the properties of laterite soils around the world, with particular emphasis on Nigeria. Initially, information is gathered from different sources about the strength-based properties of such soils. Previous research in Nigeria is used as a basis for obtaining real-world soil data. Next, stability analyses are performed using SLOPE/W with shear strength parameters for total stress (short-term), effective stress (long-term), and fully saturated soil conditions. A probability analysis is conducted for the fully saturated conditions because of the variability in the input parameters. Three slope configurations (1:1, 2:1, and 3:1) are considered. The study revealed that the laterite soils embankments lose most of its stability over time period and in full saturation soil conditions. Both these conditions significantly compromise the strength of the soil and the related stability of slopes. To consolidate all information, a database of the properties of laterite soils in some localities of Nigeria was created on the geographic information system (GIS), in order provide a quick access to information on laterite soils in Nigeria.
M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering

This article presents nano composite TiO2.Fe2O3/laterite materials, which were successfully prepared by hydrometallurgical method. The materials were modified using urea as the nitrogen source. The particles size of the materials is from 20-30 nanometers. The obtained materials can not only absorb arsenic compounds but also enhance the ability of converting As (III) or As (V) into Aso, which is removed from solution. Arsenic removal efficiency of these materials is high. Using sunlight in a hydraulic retention time, about 180 minutes, the arsenic value at the inflow was about 10 mg/L but the outflow was negligible. Covering TiO2.Fe2O3 nano on laterite have brought high economical efficiency, on one hand, it saved material and on the other hand, it can be continuously operated without the centrifugal separation of the nano material.
Bài báo này giới thiệu về phương pháp điều chế vật liệu nano TiO2.Fe2O3 biến tính nitơ được phủtrên đá ong bằng phương pháp thủy luyện. Vật liệu nano thu được có kích thước 20-30 nm. Vật liệu thu được không những có khả năng hấp phụ các hợp chất của asen mà còn có khả năng khử As (III) hoặc As (V) thành Asokhi được chiếu sáng. Sử dụng ánh sáng mặt trời chiếu vào hệ thống xử lý trong thời gian 180 phút có thể loại bỏ được gần như hoàn toàn asen ra khỏi nước mặc dù hàm lượng đầu vào là 10 mg/l. Việc phủ vật liệu TiO2.Fe2O3 nano lên đá ong đã mang lại hiệu quả kinh tế cao, một mặt nó tiết kiệm được vật liệu, mặt khác, vật liệu có thể sử dụng một cách liên tục mà không cần phải tách bằng phương pháp ly tâm.

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A origem do minério de ferro macio hospedado nos jaspilitos da Formação Carajás ainda é objeto de debate. A fim de contribuir para melhor compreensão de sua origem, o furo de sondagem SSDFD663 da mina de ferro S11D em Carajás foi investigado. Vinte amostras foram analisadas por DRX, microscopia óptica, química de rochas total e MEV/EDS. O perfil compreende quatro horizontes de intemperismo, definidos da base ao topo, como protominério, saprólito grosso, saprólito fino e crosta. O minério principal ocorre distribuído ao longo do horizonte saprolítico, é composto principalmente por hematita e subordinadamente por magnetita. A quantidade de quartzo aumenta com a profundidade, enquanto que ao topo aumenta a quantidade de minerais de Fe-Al(Ti-P). O ferro total é enriquecido relativamente no saprólito fino em comparação com o protominério (42,55 a 97,62% em peso de Fe2O3). Os elementos traços, como Zr, Cr, Y e ETR, mostram aumento relativo em direção ao topo, uma vez que eles geralmente ocorrem na presença de minerais residuais (como zircão e anatásio). Além disso, os ETR exibem a assinatura geoquímica dos jaspilitos, o que reafirma sua relação genética. Sugere-se um modelo genético laterítico-supergênico para a origem do minério macio no depósito de S11D.
The origin of the soft iron ore hosted in the jaspilites of the Carajás Formation is still subject of debate. In order to contribute to a better understanding of its origin, the SSDFD663 drill hole from the S11D iron mine in Carajás was investigated. Twenty samples were analyzed by XRD, optical microscopy, whole-rock chemistry and SEM/EDS. The profile comprises four weathering horizons, defined from the base to the top, such as protore, saprolite (coarse and fine), and crust. The main ore occurs distributed along the saprolite horizon, it is composed mainly of hematite, and subordinately by magnetite. The amount of quartz increases with the depth, while towards the top increases the amount of Fe-Al(Ti-P)-minerals. The total iron is enriched relatively in the fine saprolite in comparison to the protore (42.55 to 97.62 wt.% Fe2O3). Trace elements such as Zr, Cr, Y, and REE show relative enrichment upward since they usually occur in the presence of residual minerals (such as zircon and anatase). In addition, the REEs exhibit the geochemical signature of the jaspilites, which reaffirms their genetic relationship. A genetical laterite supergene model is suggested for the origin of soft ore at the S11D deposit.

A systematic research study was carried out in order to characterize the rheology of concentrated slurries prepared from eight nickel laterites. The experiments were carried out using a rotational viscometer, and the behavior of the laterites was evaluated in terms of the apparent viscosity and yield stress obtained through flow curve modeling. An attempt was made to correlate the results obtained for the laterite samples with data obtained for model single mineral systems as well as for model mixed mineral systems. In combination with detailed mineralogical characterization of the laterite samples, all the rheological results allowed a rheology-based laterite classification system to be proposed. Accordingly, the laterite samples gave the following responses: the SAPSIL samples (high-quartz) generally producedl ow yield stress values, the SAPFE samples (high-iron) were characterized by intermediate to high yield stress values, while the SAP samples (saprolite) gave the highest yield stress values. Interestingly, these dominant rheological responses of laterites could actually be predicted based on rheological tests carried out on model mineral suspensions (particularly goethite and quartz). Since the rheology of fine mineral suspensions is largely determined by the surface properties (surface charge) of the particles, a series of electro-acoustic measurements were also performed on model minerals and laterite samples to analyze the surface charge characteristics of the tested samples. It was demonstrated that the current electro-acoustic theory developed for single mineral systems can readily be used for modeling the behavior of mixed mineral systems. The modeling and experimental data agreed exceptionally well when constituent minerals were of the same surface charge under given pH. Clear but rather small deviations between experiment and theory were observed under conditions when the minerals were oppositely charged. This observation strongly suggested that inter-particle aggregation was most likely responsible for the observed discrepancies. Overall, the results of this thesis show that laterite slurries exhibit a wide range of rheological responses due to highly variable mineralogy, differences in particle size distributions, and difference in the surface properties of the many constituent minerals. It also shows that the surface properties of the minerals relates to rheology.

In recent years nickel is mostly produced from lateritic ore deposits such as nontronite, limonite, etc. Resource estimation is difficult for laterite deposits as they have a weak and heterogeneous form. 3D modeling software are rather suitable for deposits having tabular or vein type ores. In this study the most appropriate estimation technique for resource estimation of nickel laterite deposits was investigated. One of the known nickel laterite deposits in Turkey is located at Tü
rkmenç
ardagi - Gö
rdes region. Since the nickel (Ni) grade recovered from drilling studies seem to be very low, a reconciliation pit having dimensions of 40 m x 40 m x 15 m in x-y-z directions was planned by Meta Nikel Kobalt Mining Company (META), the license owner of the mine, to produce nickel ore. 13 core drilling and 13 reverse circulation drilling (RC) and 26 column samplings adjacent to each drillholes were located in this area. Those three sampling results were compared to each other and as well as the actual production values obtained from reconciliation pit. On the other side 3D computer modeling was also used to model the nickel resource in Tü
rkmenç
ardagi - Gö
rdes laterites. The results obtained from both inverse distance weighting and kriging methods were compared to the results of actual production to find out the applicability of 3D modeling to laterite deposits. Modeling results showed that Ni grade of the reconciliation pit in Tü
rkmenç
ardagi - Gö
rdes, considering 0.5% Ni cut-off value, by using drillholes data, inverse distance weighting method estimates 622 tonnes with 0.553% Ni and kriging method estimates 749 tonnes with 0.527% Ni. The actual production pit results provided 4,882 tonnes of nickel ore with 0.649% Ni grade. These results show that grade values seem to be acceptable but in terms of tonnage, there are significant differences between theoretical estimated values and production values.

With the dramatic growth of interest in nickel laterite resource exploitation, fueled by increasing demand and new processing technologies, the need for accurate resource delineation and careful mine planning becomes paramount. The traditional use of borehole grids to calculate mineral resources has proven to be neither sufficiently accurate nor cost-effective at many sites due to the complexity of tropical weathering profiles. Although an unconventional approach to laterite mine planning and resource delineation, emerging near-surface geophysical methods, particularly ground penetrating radar (GPR), hold tremendous potential for addressing project geology, resource delineation, and mine planning issues. GPR acquisition and processing techniques have been developed specifically for laterite applications and have been successfully utilized in the field. Preliminary test work has been performed at varied sites in Papua New Guinea, Indonesia, Venezuela, Guatemala, the Philippines, and Brazil. Two projects in New Caledonia were selected as comprehensive test sites for experimentation with GPR. Test surveys with GPR were performed at these sites to determine the effectiveness of the method in mapping the lateritic weathering profile. A description of the geology of various humid laterite deposits and the geophysical consequences of their complex nature is discussed, as well as the correlation of the acquired geophysical data to geological borehole information. Geophysics in general, and GPR in specific, has been proven to increase the database of knowledge with respect to project geology, as well as provide invaluable assistance in mine planning by high resolution imaging of the bedrock depth and texture as well as the accurate location of subsurface pinnacle structures at many sites.

Nickel laterites account for ?40 % of global nickel production and contain 60 % of the world's total land based nickel resources. Despite the importance of these deposits published studies, detailing their morphology and formation processes are relatively few and the interaction of variables responsible for the formation of different nickel laterites are poorly understood. To better understand the process of nickel laterite formation, the Caldag and Bitincke paleodeposits were studied and their geological history established. The Caldag laterite, western Turkey, formed by intense chemical weathering of a serpentinite protolith in a region with a high water table and relatively low topography, resulting in the formation of an oxide deposit. In addition silica precipitation is common in the upper horizons of the deposit, where it creates an indurated layer, protecting the deposit from erosion. The Bitincke Nickel laterite, Albania is composed of two distinct zones characterized by silicate nickel and iron oxide phases. At Bitincke laterite formation and variations in thickness were controlled by the interaction between topography, faulting and protolith fracture density. The morphological and geochemical study of the Caldag and Bitincke paleodeposits indicates that there is a complex interplay between structures, topography, water table height and climate. Therefore nickel laterite deposits developed on very similar protoliths can form deposits with distinct and different characteristics. By comparing climatic data for regions where suitable ultramafic rocks are exposed and defining the climatic conditions favourable for the formation of nickel laterite deposits, the optimum temperatures and precipitation rates for nickel laterite development can be identified. A compilation of paleoclimatic data from western Turkey and Albania allows for the optimum periods of laterite formation within these regions to be established. Calculation of temperatures of formation from goethite oxygen and hydrogen isotopes could provide additional data on paleoclimaitc conditions. However due to the heterogeneity of laterite deposits and an extended weathering history, data gained from goethite appears not to provide a robust measure of paleotemperature. The study of the Caldag and Bitincke deposits combined with the analysis of the optimum conditions for nickel laterite formation has shown that there are four main factors which effect laterite formation: 1) Exposure of a suitable protolith; 2) Optimum climatic condition; 3) Geological variables; 4) Environment of preservation. Knowledge of these variables will assist in future laterite studies and will improve predictability of the location of new deposits.

La repartition dans les profils des concentrations cobaltiferes est controlee par deux mecanismes qui interferent: le premier consiste en une accumulation progressive du cobalt dans une tranche donnee de profil correspondant au toit des alterites silicatees, au fur et a mesure de l'approfondissement de l'alteration; le second consiste en une migration progressive du cobalt depuis les zones hautes vers les depressions du toit silicate, formees par la roche en cours d'alteration. Le cobalt est porte par des produits noirs caracteristiques des divers milieux de depot

The SOLSA project aims to construct an analytical expert system for on-line-on-mine-real-time mineralogical and geochemical analyses on sonic drilled cores. A profilometer is indispensable to obtain reliable and quantitative data from RGB and hyperspectral cameras, and to get 3D definition of close-to-surface objects such as rheology (grain shape, grain size, fractures and vein systems), material hardness and porosities. Optical properties of minerals can be analyzed by focusing on the reflectance. Preliminary analyses were performed with the commercial scan control profilometer MI-CRO-EPSILON equipped with a blue 405 nm laser on a conveyor belt (depth resolution: 10 μm; surface resolution: 30x30 μm2 (maximum resolution; 1m drill core/4 min). Drill core parts and rocks with 4 different surface roughness states: (1) sonic drilled, (2) diamond saw-cut, polished at (3) 6 mm and (4) 0.25 μm were measured (see also abstract Duée et al. this volume). The ΜICRO- EPSILON scanning does not detect such small differences of surface roughness states. Profilometer data can also be used to access rough mineralogical identification of some mineral groups like Fe-Mg silicates, quartz and feldspars). Drill core parts from a siliceous mineralized breccia and laterite with high and deep porosity and fractures were analyzed. The determination of holes’ convexity and fractures) is limited by the surface/depth ratio. Depending on end-user’s needs, parameters such as fracture densities and mineral content should be combined, and depth and surface resolutions should be optimized, to speed up “on-line-on-mine-real- time” mineral and chemical analyses in order to reach the target of about 80 m/day of drilled core.

The SOLSA project aims to construct an analytical expert system for on-line-on-mine-real-time mineralogical and geochemical analyses on sonic drilled cores. A profilometer is indispensable to obtain reliable and quantitative data from RGB and hyperspectral cameras, and to get 3D definition of close-to-surface objects such as rheology (grain shape, grain size, fractures and vein systems), material hardness and porosities. Optical properties of minerals can be analyzed by focusing on the reflectance. Preliminary analyses were performed with the commercial scan control profilometer MI-CRO-EPSILON equipped with a blue 405 nm laser on a conveyor belt (depth resolution: 10 μm; surface resolution: 30x30 μm2 (maximum resolution; 1m drill core/4 min). Drill core parts and rocks with 4 different surface roughness states: (1) sonic drilled, (2) diamond saw-cut, polished at (3) 6 mm and (4) 0.25 μm were measured (see also abstract Duée et al. this volume). The ΜICRO- EPSILON scanning does not detect such small differences of surface roughness states. Profilometer data can also be used to access rough mineralogical identification of some mineral groups like Fe-Mg silicates, quartz and feldspars). Drill core parts from a siliceous mineralized breccia and laterite with high and deep porosity and fractures were analyzed. The determination of holes’ convexity and fractures) is limited by the surface/depth ratio. Depending on end-user’s needs, parameters such as fracture densities and mineral content should be combined, and depth and surface resolutions should be optimized, to speed up “on-line-on-mine-real- time” mineral and chemical analyses in order to reach the target of about 80 m/day of drilled core.

The aim of this study was to extract nickel and cobalt from the lateritic nickel ores of Gö
rdes region by hydrometallurgical methods under the optimum conditions. Limonitic and nontronitic types of Gö
rdes lateritic nickel ores were used during experiments. Agitative and column leaching experiments at atmospheric pressure were conducted with various parameters
these were duration, temperature and initial sulfuric acid concentration of leach solution. It was shown that in agitative leaching, under the optimum conditions that were determined as 24 hours of leaching at 95°
C with initial sulfuric acid concentration of 192.1 g/L for nontronite and 240.1 g/L for limonite, nickel and cobalt extractions were 96.0% and 63.4% for nontronite
93.1% and 75.0% for limonite, respectively. Overall acid consumptions of ores were calculated as 669 kg H2SO4/ton dry ore for nontronitic type nickel ore and 714 kg H2SO4/ton dry ore for limonitic type nickel ore. Column leaching experiments also showed that nickel and cobalt could be extracted from both ore types by heap leaching. Nontronite type of laterite was found to be more suitable for column leaching by sulfuric acid. In column leaching, the calculated nickel and cobalt extractions were 83.9% and 55.2% for nontronite after 122 days of leaching with 100 g/L sulfuric acid concentration. Acid consumption of nontronite was found to be 462 kg H2SO4/ton dry ore.

The objective of this thesis study is to recover nickel and cobalt at maximum efficiency from column leach liquor of lateritic nickel ores existing in Gö
rdes region of Manisa by performing various hydrometallurgical methods under the optimum conditions. This column leach solution of nontronite type lateritic nickel ore was initially neutralized and purified from its basic impurities by a two stage iron removal process under the optimum conditions determined experimentally. Then, nickel and cobalt were precipitated in the form of mixed hydroxide precipitate from the purified leach solution by a two stage precipitation method called &ldquo
MHP&rdquo
and a manganese removal process was carried out also under the optimum conditions determined. By decreasing Mn concentration with this process to an acceptable level yielding at most 10% Mn in hydroxide precipitate, it was possible to produce a qualified MHP product suitable to the current marketing and standard conditions. As a result of this thesis study, the experiments conducted showed that by recycle leaching with sulfuric acid about 81% of Ni and 63% of Co in the lateritic nickel ore (9.72 kg Ni / ton of ore and 0.28 kg Co / ton of ore) could be extracted as mixed hydroxide precipitate by MHP method. The MHP product contains 41.9% Ni, 1.0% Co, 2.3% Mn, 0.06% Al, 1.5% Mg, 0.02% Fe, 0.01% Cr, 0.25% Zn, 0.03% Cu and 4.73% S.

ABSTRACT HIGH PRESSURE ACID LEACHING OF TURKISH LATERITES Kaya, Serif M.Sc., Department of Metallurgical and Materials Engineering Supervisor: Prof. Dr. Yavuz A. Topkaya January 2011, 91 pages The aim of this thesis study was to investigate and find the most cost effective way of extracting nickel and cobalt into the pregnant leach solution (PLS) from Gö
rdes lateritic nickel and cobalt ore by means of sulphuric acid leaching under high temperature and high pressure conditions.The high pressure acid leach (HPAL) experiments were conducted with nontronitic and limonitic types of Gö
rdes lateritic nickel ore, respectively. Leaching experiments of nontronite ore have shown that almost all of the nickel and cobalt contained in the nontronitic ore were easily extracted into the (PLS). Therefore, the rest of the experiments were concentrated on difficult to leach limonitic sample when compared with the nontronitic one, and higher nickel and cobalt extractions were aimed to be obtained. By taking economic and technical considerations into account, the basic (HPAL) process parameters for the limonitic sample were optimized as
leaching at 255 °
C with a particle size of 100% -850 &mu
with 0.30 sulphuric acid to ore weight ratio in 1 hour of leaching duration. The experiments were conducted with 30% solids ratio and it was found that 87.3% of nickel and 88.8% of cobalt present in the limonitic ore could be extracted into the pregnant leach solution. Nevertheless, these results were found to be below the desired values. Therefore, the possible reasons of this behavior were investigated and the presence of hematite mineral in the limonitic ore was found to be the most probable one. Therefore, in order to dissolve the nickel and cobalt present in the hematite mineral, the additions of HCl, ferrous ions, cuprous ions and sulphur were tried, respectively and they were found to be beneficial in order to increase the degree of nickel and cobalt extractions.

The purpose of this study was to investigate the process optimization of combined high pressure acid leaching (HPAL) and mixed hydroxide precipitation (MHP) route for the extraction of nickel and cobalt from Ç
aldag lateritic nickel ore. In order to extract nickel and cobalt values into pregnant leach solution (PLS), several process parameters of HPAL including acid load, temperature, leaching duration and particle size were investigated in comparative manner at constant solid concentration and agitation speed. After HPAL trials, it has been found that more than one combination of parameters offered higher than 90% extraction efficiencies for both nickel and cobalt. Among them, 0.325 kg/kg acid load, 250°
C, 1 hour duration and 100% -1 mm particle size was selected as the optimum conditions with 94.1% Ni and 94.0% Co extractions. A stock of PLS was prepared under the stated conditions that was treated by downstream operations in order to obtain MHP. Initially by two-stage iron removal of downstream operations major impurities iron, chromium and aluminum were nearly completely removed with acceptable nickel and cobalt losses from PLS. Then, the nickel and cobalt were precipitated by two-stage mixed hydroxide precipitation. In the first step of MHP, the optimum conditions were chosen as pH=7.10, 60°
C and 1 hour duration. The intermediate product obtained at these conditions contained 44.3% Ni, 3.01% Co with 3.06% Mn contamination. In summary, it was found that Ç
aldag nickel laterite ore was readily leachable under HPAL conditions and PLS obtained was easily treatable in order to produce saleable MHP.

Madagascar - Ambatovy region, AMBATOVY Project - Sherritt International. The Ambatovy Project, a mine for nickel and cobalt ore located in the centre of the country, required the construction of a slurry pipeline to transport the ore 220 km to be processed on the east coast. The pipeline and its maintenance road traverses primary forests, the sensitive Torotorofotsy Wetlands and include 172 stream crossings in sensitive laterite soils. The restoration and rehabilitation of the cut and fill geotechnical works and stream crossings is important technical works within the environmental portfolio and for project cost reductions.The surface water erosion of the soil and the associated stream sedimentation are studied. These processes are classified based on the characteristics of the vegetation/land use, the slopes and the type of laterite soil. Three representative sites are chosen for a detailed study using field observations and field measurements (TSS in streams). These results are compared to numerical modeling results using RUSLE (Revised Universal Soil Loss Equation model) for surface erosion within GeoWEPP (Geo-spatial interface for Water Erosion Prediction Project), a USGS (US Geological Survey) –LESAM (Landscape-based Environmental System Analysis & Modeling) model which conducts continuous and process-based simulations of small watersheds, for soil erosion and sedimentation.At the three selected sites, the use of GeoWEPP as a tool to explore possible mitigation measures using geotechnical engineering methods combined with revegetation is investigated and discussed. The results of these studies will be used to suggest measures to mitigate environmental impacts associated with the pipeline construction for the Ambatovy Project.
Madagascar – région d'Ambatovy, Projet AMBATOVY - Sherritt International. Le Projet Ambatovy, une mine de nickel et cobalt située au centre de l'ile, a requiert la construction d'un pipeline de pulpe pour pouvoir transporter le minerai sur 220kms, pour pouvoir être acheminé et transformé sur la côte Est. Le pipeline et son réseau routier de maintenance traverse des forêts primaires, la sensible région du marais de Torotorofotsy et incluant 172 cours d'eau sensibles reposant sur le sol latéritique. La restauration et la réhabilitation des tranchées de remblai et déblai grâce aux travaux géotechniques sont d'importants travaux techniques pour les cours d'eaux notamment au niveau de l'impact environnemental et jouant sur la réduction des couts du projet. Le phénomène de l'érosion de surface au niveau des cours d'eau et la sédimentation des rivières y associée ont été étudiés. Les processus sont classés sur base des caractéristiques de la végétation, de la pente et du type de sol latéritique. Trois sites représentatifs sont choisis aux fins d'une étude détaillée avec usage des données et observations de terrain (MES dans les rivières). Ces résultats sont par la suite comparés aux résultats avec usage des modèles numériques utilisant RUSLE (Revised Universal Soil Loss Equation model) pour l'érosion de surface dans GeoWEPP (Geo-spatial interface for Water Erosion Prediction Project), un modèle provenant de USGS (US Geological Survey) –LESAM (Landscape-based Environmental System Analysis & Modeling) qui conduit notamment des simulations en mode continu et sous base de processus pour les petits bassins versants, concernant l'érosion et la sédimentation.Au niveau de ces trois sites sélectionnés, l'utilisation de GeoWEPP comme utile de prédiction et de « design » des mesures de mitigation possibles par usage de solutions d'ingénierie géotechnique combinée à la re-végétalisation ont pu être étudiés et comparés. Les résultats de ces études pourront être utilisés en tant que suggestion de mesures de mitigation des impacts environnementaux relatifs à la construction du pipeline du Projet Ambatovy.

The aim of this thesis study was to extract nickel and cobalt from Sivrihisar limonitic nickel laterite ore by high pressure acid leaching (HPAL) method under most economical operating parameters. Optimizing the conditions to yield a saleable quality mixed hydroxide product from the pregnant leach solution (PLS) was also investigated. To extract high amounts of nickel and cobalt from the laterite matrix
leaching duration, leaching temperature and sulfuric acid/ore ratio were studied at fixed conditions of -850 µ
limonitic ore particle size and 40% solids concentration. The Sivrihisar limonitic nickel laterite ore was found to be readily leachable. It was found that 95.4% of Ni and 91.5% of Co were extracted at the optimized conditions of 235oC, 0.23 acid/ore ratio in 60 minutes. The real pregnant leach solution produced at the optimized conditions of HPAL was purified in two iron removal stages under the determined optimum conditions. Nearly all of the Al and Cr were removed from the PLS in the two stages of iron removal. Then, nickel and cobalt were taken out from the PLS in the form of mixed hydroxide precipitates (MHP) in two stages. A MHP 1 product containing 33.41 wt.% Ni, 2.93 wt.% Co was obtained with a Mn contamination of 3.69 wt.% at the optimized conditions of pH=7, 50oC and 60 minutes. The MHP 1 product was also contaminated with Fe (2.83 wt.%) since it could not be completely removed from the PLS without the critical losses of nickel and cobalt during the two iron removal stages.

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Locally available building materials are proven energy efficient and eco-friendly, making them a sustainable building material. In the last two decades, use of raw earth as building material is augmented, owing to the environmental concerns construction industry is also reconsidering the use of raw earth, researchers on the other hand are working to understand the mechanical and dynamic behaviour of earthen buildings, yet the study of mechanical parameters possess multiple challenges due to material inert properties exposing the need of new experimental approaches to extract accurate mechanical parameters. Building techniques such as adobe, compressed earth blocks, rammed earth, and laterite building stones are on a verge of reclaiming elite position in construction industry. In this study, experimental investigation on two naturally available building materials, unstabilised rammed earth (USRE) and laterite building stones (LBS) are carried out. The work focuses on the parameters that need to be considered in the experimental procedures, which influences the mechanical properties of USRE and LBS are seen. The locally available soils in the region of Rhone-alps, France and laterite building stones from Burkina Faso are used in this experimental campaign. Rammed earth walls are constructed by compacting moist soil in layers, due to manufacturing technique there is a density gradient within the layer that leads to heterogeneity. On the other hand, the manufacturing parameters of the USRE such as compaction energy and manufacturing water content have a direct influence on the dry density of the material and therefore the strength. The manufacturing parameters and specimens replicating the in-situ condition are very important to understand the behaviour of USRE wall. Hence an experimental procedure to study the unconfined compressive strength, considering the influence of manufacturing parameters and specimens replicating in-situ conditions are performed along with the cyclic loading and unloading to study the elasto-plastic property of the USRE. The test procedure is performed on two different soils that are used to build USRE structures. Along with the compressive strength of USRE, the tensile strength and flexural strength are also presented by subjecting specimens under split tensile test and four point bending test. Another important parameter is the mechanical strength properties of USRE layer interface under lateral loads. A novel experimental procedure to study the interface strength properties are discussed in this study. The experimental procedure is simple and xii compact that can be performed using a simple uniaxial press using inclined metallic wedges that allows rectangular prism to undergo bi-axial loading. With the help of inclined metallic wedges, shear stress and normal stress can be induced on the specimen interface allowing to obtain coulomb’s failure criteria and hence the strength properties of the interface. Laterite building stones (LBS) which are mainly used in tropical countries are porous in nature. The moisture retention capacity of porous building material will bring indoor comfort, but the presence of water molecules within the material and their variation to the outdoor environment is responsible for complex mechanical behaviour. Hence an experimental investigation to analyse the moisture ingress of LBS and their influence on mechanical strength is designed. The moisture ingress is studied by subjecting LBS for moisture sorption and desorption test and moisture buffering test. Then the influence of moisture ingress on mechanical strength (flexure and compression) are investigated using three point bending test and unconfined compression test with loading and unloading cycles. This experimental investigation allows studying the moisture ingress and their influence on strength along with elasto-plastic behaviour of LBS

Nickel extracting industries have been facing challenges reflecting, inter alia, low recoveries of Ni and Co, high acid consumption and inadequate knowledge of dissolution kinetics. In oxic laterite, Ni is mostly associated with goethite. Consequently, for effective extraction of Ni and Co from oxic Ni laterites, a clear understanding of their chemistry, mineralogy and mechanism of sorption in goc;!thite during laterite ore formation is essential. The result from experiment of Ni sorption on goethite revealed that at surface loadings of 0.003 to 0.2 wt. % Ni, only the >Fe(OH)2Ni complex was needed to, fit the data whereas both >Fe(OH)2Ni and (FeOH)2Ni complexes were invoked to fit surface loadings of >0.2 to 0.35 wt. % Ni. At 0.75 wt. % Ni and above, however, the polynuclear complex (FeOH)3Nh was required to fit the data. Similar results were obtained for Co sorption and co-sorption of Ni and Co on goethite. EXAFS results support the existence of Ni surface precipitate or extended polynuclear Ni complex in the Ni-sorbed goethite and Ni laterite. In all the samples, Ni and Co dissolve incongruently with iron. However, there exist disparities in their dissolution and desorption kinetics as a function of aging and concentration, which indicate differences in chemical structure. Modelling of Ni laterite using PHREEQC and equilibrium constants obtained from EQLFOR provides information on the processes of Ni laterite formation and the zones of supergene Ni enrichment as well as prediction of the weathering profile. The solubility product (Ksp) of Ni or Co substituted goethite increases with increasing metal substitution. Similar results were obtained for bi-metal substituted goethite. In general, leaching with dilut~ 2.75 M aqua regia is best for Ni laterites formed at low loading as well as those formed via surface precipitation with Fe content less than 33 wt. % Fe whereas 2.75 M HCI is effective for those formed at high loading containing> 33 wt.% iron.

Lateritisation is associated with tropical climates and geomorphic conditions of peneplanation where hydromorphic processes of weathering predominate. Laterites are products of relative (residual) and absolute(chemical) accumulation after leaching of mobile constituents. Their major element chemistry is controlled by the aluminous character of bedrock and drainage. Bauxitisation is characterised by residual gibbsite neoformation and lateritisation, by both residual accumulation and hydromorphic precipitation of goethite controlled by the redox front at the water table. The laterite forms part of a weathering profile that is underlain by saprock, saprolite, the mottled zone and overlain by a soil horizon. The secondary gold in laterites has its source invariably with mineralised bedrock. The distribution of secondary gold is controlled by mechanical eluviation and hydromorphic processes governed by organic, thiosulphate and chloride complexing. The precipitation of secondary gold is controlled by pH conditions, stability of the complexing agent and ferrolysis. Gold-bearing laterites are Cainozoic in age and are best developed on stable Archean and Proterozoic cratons that have suffered epeirogenesis since lateritisation. Mechanical eluviation increases in influence at the expense of hydromorphic processes as a positive function of topographic slope and degradation rate. Gradients greater than 10⁰ are not conducive for lateritisation, with latosols forming instead. High vertical degradation rates may lead to the development of stone lines. In the Western Australian case, post-laterite aridification has controlled the redistribution of secondary gold at levels marked by stabilisation of the receding palaeowater table. Mineable reserves of lateritic ore are located at Boddington, Westonia and Gibson toward the south-west of the Yilgarn Block. A significant controlling variable appears to be the concentration of chloride in the regolith. Based on the Boddington model, the laterite concentrates the following elements from bedrock gold lodes: i) Mo, Sb, W, Hg, Bi and Au as mobile constituents. ii) As and Pb as immobile constituents. Geochemical sampling of ferruginous lag after bedrock and laterite has provided dispersed anomalies that are easily identifiable. "Chalcophile corridors" up to 150 km in length are defined broadly by As and Sb but contain more discrete anomalies of Bi, Mo, Ag, Sn, W, Se or Au, in the Yilgarn Block. The nature of the weathered bedrock, the tabular distribution of secondary gold ore deposition and the infrastructural environment lends the lateritic regolith to low cost, open-cut mining. The western Australian lateritic-gold model perhaps can be adapted and modified for use elsewhere in the world.

Leaching is the most widely used process for extraction of nickel metal from lateritic ores. In this study, nickel extraction from Manisa-Gö
rdes region laterites by hydrochloric acid leaching is aimed. The mineralogical analysis of sample showed that hematite, goethite, dolomite, quartz and smectite are the main minerals in the ore. Attrition scrubbing, cycloning and magnetic separation with permroll were used as preconcentration processes but results were unsatisfactory. HCl leaching experiments were conducted both at room temperature and at elevated temperatures. The effects of various parameters such as leaching duration, particle size, concentration of HCl, pulp density, Cl- concentration and temperature on nickel recovery were examined. The results showed that under the optimised leaching conditions (particle size: 100 % -1 mm, HCl concentration: 3 N, leaching duration: 3 hours, leaching temperature: 100 oC, pulp density: 1/30 solid to liquid ratio by volume) it was possible to extract 87.26 % of nickel in the ore.

Remote sensing data and image processing techniques are used increasingly to aid scientific investigation and address geological problems in areas that are difficult to map by conventional methods. This thesis explores how multi spectral satellite data, supported by traditional geological techniques, facilitate a study of lateritic palaeosols. The work centres on laterites, which are thin but important elements of the Phanerozoic stratigraphy of NE Africa. They immediately pre-date midOligocene flood basalts and, if mapped, can be used to delineate a flood basalt-Iaterite contact and define the pre-30 Ma African Surface and uplift patterns. They have important engineering properties and are key to understanding basement alteration and its associated mineralization. They affect agriculture and groundwater quality and retention - essential in Sub-Saharan Aflica where access to safe water is limited. They dominate the landscape, yet are unmapped and marginalised in the literature. Their geological context supports a laterite-focused remote sensing mapping strategy. A strategy for geologic mapping of laterites based on their simple mineralogy and spectral characteristics that distinguish them from other rocks is developed. Methods for mapping are presented using Earth Observation data. The outcome is a series of regional geological maps of Eritrea and Ethiopia. These reveal that laterite cover is more extensive than previously thought and enable further lines of research. The maps provide a means of regional dating of laterites, which, together with ages obtained for overlying flood basalts and new basement cooling ages, indicate a major planation during the Palaeozoic and constrain the timing of associated uplift and erosion. A regional review of Mesozoic-Cenozoic climatic, strati graphic and structural evolution is presented and a model of Neogene deformation of the lateriteflood basalt datum is produced. Finally, laterite maps, petrographic and geochemical evidence are used to access basic essentials of life: clean water, a safe environment and a sustainable economy.

In several parts of Burkina Faso, there is an urgent need of making arsenic contaminated water potable. The shallow, dug out wells traditionally used in the rural areas provides small, inconsistent yields and are vulnerable to microbes. Consequentially, many of them have now been replaced with drilled tube-wells, intercepting water from fractures in the bedrock and providing reliable water sources. However, as arsenic is naturally present in the bedrock in many parts of the country, previous studies has shown that water from a lot of these wells is not safe to drink. In some cases, the wells had to be closed due to high arsenic concentrations. The medical effect of the arsenic exposure has also been evaluated among the inhabitants of affected villages, indicating that the problem is critical. Previous studies in this project were focused on using the commercial material Granular Ferric Hydroxide (GFH) as a possible method for arsenic removal in the villages. As the price of GFH however is too high, other methods has been researched instead. In this study, natural laterite rock has been crushed and used as adsorbent in column experiments, but indicating a low arsenic capacity. The same lateritic sand has then been coated in ferrihydrite both by drying the materials together in the oven and by a centrifugation method previously evaluated in Uppsala, Sweden. Although results after the ferrihydrite-coating improved, the adsorption capacity was still significantly lower than that of GFH. The results from the ferrihydrite-coated sand also differed largely from those previously found in Uppsala, and though this could be due to the fact that this study was made with natural water instead, it is thought that the inevitable alterations in the coating method might have affected the result of the coating to a great extent. The conclusion of this study is therefore that ferrihydrite-coated sand still is a possible low-cost adsorbent material for arsenic contaminated water in developing countries, though factors such as sand material, grain size and coating method should be evaluated further.