Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-05-26T15:02:40Z No. of bitstreams: 1 simonejaquelinecardoso.pdf: 1421959 bytes, checksum: 0bda7b55f248e227b23eb59614787c9a (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-26T15:14:55Z (GMT) No. of bitstreams: 1 simonejaquelinecardoso.pdf: 1421959 bytes, checksum: 0bda7b55f248e227b23eb59614787c9a (MD5) / Made available in DSpace on 2017-05-26T15:14:55Z (GMT). No. of bitstreams: 1 simonejaquelinecardoso.pdf: 1421959 bytes, checksum: 0bda7b55f248e227b23eb59614787c9a (MD5) Previous issue date: 2009-12-21 / A morfometria trata da quantificação e medida dos diversos elementos da forma, englobando, portanto, o conjunto de métodos para medir as dimensões físicas de um indivíduo ou sistema. As avaliações morfológicas têm sido um mecanismo de estudo de muitas áreas dentro da ciência e funcionam como ferramentas fundamentais tanto em escala microscópica, quanto em dimensões ecossistêmicas. Em sistemas lacustres, a compreensão dos fatores que envolvem variáveis morfométricas é de grande importância; pois, esses fatores, podem contribuir com muitas informações a respeito de suas estruturas e funções, sobre a dinâmica de cadeias tróficas, e a regulação do fluxo de substâncias desses ambientes. A morfologia dos sistemas lacustres é um fator importante também na distribuição de espécies em diferentes níveis de observação, sejam eles, locais, regionais ou globais. Resultados que suportam esta aplicabilidade foram encontrados neste estudo, que utilizou a comunidade fitoplanctônica como modelo de estudo. Foram realizados levantamentos morfométricos e de riqueza fitoplanctônica em 26 lagos amazônicos de águas claras e em 40 diferentes lagos naturais e artificiais, sendo 20 lagos brasileiros e 20 lagos de diferentes regiões do mundo. Através de regressões lineares simples, foram encontradas relações positivas significativas (p<0,005) entre a riqueza de espécies fitoplanctônicas e parâmetros morfométricos como área, perímetro, volume, índice de desenvolvimento de margem e índice de desenvolvimento de volume. No entanto, o índice de desenvolvimento de margem, foi o que me melhor representou a relação entre complexidade do sistema e a riqueza de espécies do fitoplâncton, caracterizando um efeito de borda em lagos. / Morphometry is the measurement of various elements of form, and it includes methods to measure since the physical dimensions of an individual to the dimensions of a system. Morphological evaluations are good study mechanisms in many areas of science and work as fundamental tools from a microscopic scale to the dimensions of an ecosystem. In lakes, the understanding of the factors involving morphometric variables is of great importance. These factors can contribute with a lot of information about the structures and functions, on the dynamics of food chains, and on regulating the flow of substances such systems. The morphology of lakes is also an important factor in the species distribution at different levels of observation, whether local, regional or global. Results supporting this applicability were found in this study, which used the phytoplankton community as a model. It was performed surveys on morphometric features and phytoplankton richness in 26 Amazonian clear water lakes and on 40 different natural and artificial lakes, 20 lakes in Brazil and 20 lakes in different regions of the world. Through linear regression, we found significant positive relationships (p<0.005) between phytoplankton richness and morphometric parameters such as area, perimeter, volume, shoreline development and volume development. Although, the shoreline development was the one that best correlated to the phytoplankton diversity, featuring such an edge effect in lakes.

The thesis establishes guidelines for the development of a prototype secondary school in Lagos State, as well as in other parts of Nigeria with similar hot humid climate. The practicability of these guidelines was evaluated by applying it to a hypothetical design project. The study presents a general background of existing conditions in the country--social, educational system, physical and architecture, before defining the context within which the design guidelines must be evolved. With a careful examination of these aspects, a set of design guidelines have been developed. The proposed solution (guidelines) attempts to improve the environmental comfort in schools through the use of passive techniques. Experimental tests on the passive approach was limited to natural ventilation, daylighting and shading control. The design development and guidelines established in this thesis are not definitive but a representation of a preliminary architectural study which may need further investigations. / M. Arch.

The study sought to assess the knowledge of adolescents regarding abortion in a selected area in Lagos Nigeria. The researcher used a non-experimental, exploratory, descriptive research design for the study. One hundred adolescents participated in the study. The study found that many adolescents will not admit to having had an abortion. Moreover, the respondents gave different meanings for abortion, had inadequate knowledge of abortion and sexual and reproductive health. Cultural taboos and religious beliefs have a great impact on adolescents’ sexual behaviour. Most adolescents would not access abortions services because they regard it as killing an innocent baby. Efforts should be strengthened to make contraceptives and family life education available and accessible to the adolescents. / Health Studies / Thesis (M.A. (Health Studies))

The study sought to assess the knowledge of adolescents regarding abortion in a selected area in Lagos Nigeria. The researcher used a non-experimental, exploratory, descriptive research design for the study. One hundred adolescents participated in the study. The study found that many adolescents will not admit to having had an abortion. Moreover, the respondents gave different meanings for abortion, had inadequate knowledge of abortion and sexual and reproductive health. Cultural taboos and religious beliefs have a great impact on adolescents’ sexual behaviour. Most adolescents would not access abortions services because they regard it as killing an innocent baby. Efforts should be strengthened to make contraceptives and family life education available and accessible to the adolescents. / Health Studies / Thesis (M.A. (Health Studies))

This study explored the acceptance of cloud computing (CC) services by small and medium enterprises (SMEs) in Lagos, Nigeria, which has been missing from CC services literature. It aimed to understand the motivations for adoption, the uses of the services, and the benefits they derive from it. The uses and gratification theory was applied as the theoretic framework for this endeavor. An online survey with close-ended and open-ended questions was distributed to 1200 randomly selected participants through email. In total, 392 valid responses were collected and analyzed using descriptive statistics and categories. The results found that SMEs in Lagos, Nigeria had a low level of awareness and appreciation of CC services. The adoption rate was also low. Unlike their counterparts in other regions, SMEs primary concerns were service downtime, stable power supply, and better internet access. The study found that SMEs were not taking full advantage of the capabilities of CC services. Some sections, however, were doing better than others, such as the information and communications sub-sector. This study suggested that targeted interventions should be conducted to raise the awareness of CC services in SMEs, and to improve their efficient and effective use of CC services. The uses and gratification theory was appropriate for guiding this study to understand the acceptance and use of CC services by SMEs in Lagos, Nigeria.

Work is an essential activity that provides goods or services of value to oneself and others. Paradoxically, in a bid for self-realisation, workers are seriously endangered. Work-related or induced diseases and stresses pose serious threats to workers’ health and the general well-being, hence, the need to seriously consider the issue of occupational health and safety of workers. In terms of safety at work, the experience of small and medium scale enterprises (SMSEs) worldwide is that of neglect. Their incomes are very low and uncertain, coupled with high levels of risk and hazard in their work, with little or no social protection coverage (Chen, 2008). This study therefore examines how environmental and sociological factors determine occupational health and safety of workers in SMSEs in Lagos State, Nigeria. Ulrich Beck “Risk Society” theory, Political Economy of Health framework (PEH) (Minkler et al 1994, Linnan et al, 2001) and Labour Process Theory (LPT) (Braverman, 1974; Marx, 1976; Bottome, 1991) underpinned the study. The study adopts both the qualitative and quantitative methods of data collection. The qualitative method includes field observation of the selected workplaces, six Focus Group Discussion (FGD) and eight In-depth interviews (IDIs). The quantitative involved the use of structured questionnaire. The sample survey involved 180 respondents in a multi-stage sampling technique from purposively selected sawmills, mechanic villages and blacksmith cottages in three Local Government Areas in Lagos State. The quantitative data analysis uses simple percentile and univariate analyses, while the qualitative data are content-analysed, based on the objectives of the study. The findings identified low level of education (60.5%), and poor awareness of OHS in SMSEs (86.1%). It further reveals poor physical (69.5%) and technological environment (70.5%), unavailability of OHS facilities (60.5%) and prevention methods by manager/owners (60.5%), carefree attitudes of workers/managers/owners to OHS (69.5), non-acquaintance of workers to OHS laws (86.1%), workers’ economic incapacitation to deal with issues of occupational hazard (76.1%), lack of enforcement of OHS (88.3%), and transferring knowledge on OHS (82.2%) in the selected SMSEs. The study recommends roles for managers/owners, workers, trade associations, government, non-governmental organisations to promote effective OHS in the selected SMSEs. / Sociology / D.Phil. (Sociology)

Tesis presentada a la Universidad de Chile para optar al grado académico de Magíster en Bioquímica área de especialización en Bioquímica Ambiental y Memoria para optar al título profesional de Bioquímico / Chile en particular es uno de los países del mundo que alberga una mayor variedad de ecosistemas considerados extremos, por tener condiciones hostiles para la vida. Estas condiciones suponen un obstáculo al cual los organismos que los habitan deben sobreponerse adoptando distintas estrategias de supervivencia. Uno de estos ambientes extremos son los sistemas hidrotermales que se encuentran repartidos a lo largo de toda nuestra geografía. En muchos de los sistemas termales de todo el mundo con la característica de poseer un pH neutro o alcalino, se ha descrito a las cianobacterias de la subsección V (Stigonematales) como uno de los principales organismos que impactan los ciclos biogeoquímicos sobre todo del carbono y nitrógeno. La adaptación a las altas temperaturas de este grupo tan relevante de microorganismos en estos sistemas no ha sido todavía muy estudiada. Una de las posibles causas que hasta la fecha no ha sido explorada, y que podría explicar esta adaptación, es el efecto positivo de su asociación con cianofagos, virus de DNA de doble hebra que las infectan. En otros ecosistemas acuáticos como el marino, se ha sugerido que la interacción cianofago-cianobacteria implica una marcada co-evolución por parte de ambos, lo que tiene un impacto ecológico preponderante. En ambientes marinos los cianofagos han sido estudiados tanto morfológica como filogenéticamente utilizando diversos marcadores moleculares y métodos de observación, mientras que estas metodologías no se han aplicado en relación a la caracterización de cianofagos en sistemas hidrotermales. Debido a este vacío en la literatura en relación a los cianofagos de sistemas termales, es que en el presente proyecto se plantea caracterizar la diversidad tanto morfológica como filogenética de cianofagos presentes tanto en muestras naturales como en aislados en cultivo de cianobacterias del sistema hidrotermal de Porcelana, localizado (42º 27’ 29.1’’S - 72º 27’ 39.3’’O) en la Patagonia norte de Chile (X Región de los Lagos). En este sistema termal prístino, se ha identificado la presencia (Mackenzie et al. 2013) y aislado en cultivo (Alcamán et al. 2017) de cianobacterias de la subsección V. Los miembros de este grupo son dominantes en los tapetes microbianos a temperaturas entre 40°C y 60ºC en este sistema. Se llevarán a cabo análisis morfológicos y estructurales mediante microscopía electrónica (TEM), así como análisis basados en marcadores genéticos como el gen g20 (correspondiente a una proteína de ensamblaje de la cápside viral), psbA (gen de proteína de fotosistema), g23 (codifica para MCP, proteína mayor de la cápside), dnapol (DNA polimerasa), entre otros; análisis de secuencias encontradas en los metagenomas, metatranscriptoma y metaviroma, y en el genoma de los aislados para la detección de profagos. Los resultados que se obtengan en este estudio particular en la terma Porcelana se espera proporcionen la primera información que ayude a identificar los principales cianofagos asociados a cianobacterias termófilas de la subsección V, ayudando así a dilucidar su rol ecológico en este sistema y quizás en muchos otros sistemas termales similares a este repartidos por todo el mundo / Chile in particular is one of the countries in the world that shelters a greater variety of ecosystems considered extreme, because of their hostile conditions to life. These conditions constitute an obstacle to which the organisms that inhabit them must overcome by adopting different strategies of survival. One of these extreme environments are hydrothermal systems that are distributed throughout our geography. In many of the thermal systems of the world with the characteristic of having a neutral or alkaline pH, subsection V cyanobacteria (Stigonematales) have been described as one of the main organisms impacting the biogeochemical cycles, especially carbon and nitrogen. The adaptation to the high temperatures of this group of relevant microorganisms in these systems has not yet been studied. One of the possible causes that until now has not been explored, and which could explain this adaptation is the positive effect of its association with cyanophages, double-stranded DNA viruses that infect them. In other aquatic ecosystems such as the marine, it has been suggested that the cyanophage-cyanobacteria interaction implies a marked co-evolution, which has a preponderant ecological impact. In marine environments, cyanophages have been studied both morphologically and phylogenetically using different molecular markers and observation methods, whereas these methodologies have not been applied in relation to the characterization of cyanophages in hydrothermal systems. The lack of information in the literature regarding on cyanophages of thermal systems, the present project aims to characterize the morphological and genetic diversity of cyanophages present in both natural and cyanobacterial culture isolates of the Porcelana hydrothermal system, located (42º 27 '29.1''S - 72º 27 '39.3''O) in the northern Patagonia of Chile (X Region de los Lagos). In this pristine thermal system, the presence (Mackenzie et al. 2013) and isolated in culture (Alcamán et al. 2017) of subsection V was identified. The members of this group are dominant in the microbial mats at temperatures between 40°C And 60°C in this system. Morphological and structural analyzes will be performed using electron microscopy (TEM), as well as analyzes based on genetic markers such as the g20 gene (corresponding to a viral capsid assembly protein), psbA (photosystem protein gene), g23 (Major capsid protein), dnapol (DNA polymerase), among others; analysis of sequences found in metagenomes, metatranscriptome and metavirome, and in the genome of the isolates for the detection of prophages. The results obtained in this particular study in the Porcelana termal system are expected to provide the first information that will help to identify the main cyanophages associated to thermophilic cyanobacteria of subsection V, helping to elucidate their ecological role in this system and perhaps in many other thermal systems similar to this one, spread all over the world

Submitted by Dominick Jesus (dominickdejesus@hotmail.com) on 2016-01-26T18:05:05Z No. of bitstreams: 2 Dissertação_Maxley Barbosa Dias.pdf: 8346880 bytes, checksum: e5cebd420d314628157970f54d13eeec (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-01-26T18:05:05Z (GMT). No. of bitstreams: 2 Dissertação_Maxley Barbosa Dias.pdf: 8346880 bytes, checksum: e5cebd420d314628157970f54d13eeec (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2007-01-10 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The present study was done on the southwest of the Lago Piratuba Biological Reserve, on Araguari river floodplain, Amapá coast region, Brazil. The environments were the lakes Comprido de Cima, Bacia, Lodão, Ventos, Grande and Comprido de Baixo and the Araguari River downstream. This region is submitted to an influence of the semidiurnal tide from the Amazon River sediments plume and the periodical local rain regime. The ecological characterization of the phytoplankton community was done by to seasonal samples (rainy and less rainy season). Information from physical and chemical factors (pH, electrical conductivity, turbidity, water transparency, water temperature, salinity), climatological (precipitation) and hydrological (hydrometric level and river discharge). Phytoplankton was represented by 178 taxa. Although, these ecosystems are located in a great ecotone, they present a low specific diversity in contrast to the high specific diversity from other Amazonian environments. Lakes presented higher specific richness and diversity than the River. On both seasonal periods, lakes and Araguari River presented low phytoplankton composition complexity, described by C-strategists species, represented predominantly by cryptophytes and chrysophytes. These species are characteristic of shallow and turbid environments. The presence of estuarine species increases the diversity in some lakes and in Araguari River. They also contribute to the complexity increase of the phytoplanktonic community. The spatial uniformity between lakes probably is related to the low variation between the physical and chemical conditions. However, the river phytoplankton composition changed with the horizontal gradient observed for the physical and chemical factors when it comes near the delta. The environmental characteristics favoured the dominance of species form the functional groups S, X 1 , X 3 and Y in distinct points of the lakes and the Araguari River. They were also linked with the low significant incidence of desmids. The relevant regulatory factors on the phytoplankton population composition and abundance on these environments were the conspicuous variation on the water column between both seasonal periods, the water from the daily tide in the river and some lakes estudied, the presence of currents on lakes, the constant mixture on the water column and the low water transparency, especially on the less rainy season. / O presente estudo foi desenvolvido a sudoeste da Reserva Biológica do Lago Piratuba, na planície de inundação do rio Araguari, região costeira do estado do Amapá, Brasil. Os ambientes estudados compreendem os lagos Comprido de Cima, Bacia, Lodão, Ventos, Grande e Comprido de Baixo e o baixo curso do rio Araguari. Esta região localiza-se em área de intenso hidrodinamismo, sofrendo influência de maré semidiurna, da pluma de sedimentos do rio Amazonas e da freqüência e periodicidade das chuvas locais. A caracterização ecológica da comunidade fitoplanctônica desses ecossistemas foi feita a partir de duas amostragens sazonais (chuvoso e menos chuvoso). Foram realizadas análises físicas e químicas (pH, condutividade elétrica, turbidez, transparência da água, temperatura da água, salinidade), climatológicas (pluviosidade) e hidrológicas (nível hidrométrico e vazão do rio). As populações fitoplanctônicas foram quantificadas pelo método da sedimentação em microscópio invertido. O fitoplâncton esteve representado por 178 táxons. Apesar dos sistemas encontrarem-se em uma grande área de ecótono, do ponto de vista do fitoplâncton a diversidade específica foi baixa em comparação com a alta diversidade específica registrada para o fitoplâncton de outros ambientes amazônicos. Os lagos apresentaram maior riqueza específica e diversidade do que o trecho rio estudado. Nos dois períodos sazonais os lagos e o rio Araguari apresentaram baixa complexidade em a composição florística, marcada por espécies C-estrategistas, representadas principalmente por criptofíceas e crisofíceas características de ambientes rasos, turbulentos e com elevada turbidez. No entanto, a presença de algas mixohalinas, além de aumentar a diversidade do rio Araguari e de alguns lagos, principalmente no período menos chuvoso, também contribuíram para o relativo aumento da complexidade da comunidade fitoplanctônica em certos lagos. A uniformidade espacial entre os lagos provavelmente está relacionada à baixa variabilidade das condições abióticas. Já no rio, a composição fitoplanctônica acompanhou o gradiente horizontal observado para as variáveis físicas e químicas, à medida que se aproximava da foz. As características do ambiente favoreceram a dominância de espécies dos grupos funcionais S, X 1 , X 3 e Y em pontos distintos dos lagos e do rio Araguari e a presença pouco significativa das desmídias. A marcante variação da coluna d’água entre os dois períodos sazonais, a entrada da maré diária no rio e em alguns lagos estudados, a presença de corrente nos lagos, mistura constante da coluna d’água e a baixa transparência, principalmente no período menos chuvoso configuraram-se como fatores reguladores relevantes na composição e abundância das populações fitoplanctônicas desses ambientes.

O depósito laterítico de Nb (ETR, Ti) Morro dos Seis Lagos (MSL) é derivado de siderita carbonatito (SC). O gnaisse encaixante foi afetado por fenitização potássica (flogopita e ortoclásio + monazita, fluorapatita e bastnäsita). Há três tipos de SC: o de núcleo (siderita e hematita + acessórios Ce-Ba-pirocloro, Nb-brookita, Ti-maghemita e thorbastnäsita; uma variedade do de núcleo rica em ETR-P (siderita e hematita + Ce-Ba-pirocloro, monazita e bastnäsita; e o de borda (siderita e barita + gorceixita, rabdofano e Pb-Ba-pirocloro). Dados de inclusões fluidas e isótopos de C e O indicam que o SC de núcleo é tardi-magmático a hidrotermal e o de borda é hidrotermal. O SC de núcleo é o carbonatito mais rico em Fe e o mais pobre em Ca jamais descrito, é rico em Mn, Ba, Th, Pb, ETRL e Nb. A alta razão Nb/Ta indica líquidos residuais derivados por cristalização fracionada. Dados isotópicos (Sr e Nd) sugerem origem mantélica praticamente sem contaminação crustal. O complexo carbonatítico MSL representa a parte apical de sistema carbonatítico magmático diferenciado e o SC é relacionado a processos tardi-magmáticos a carbo-hidrotermais. O depósito de Nb é associado a lateritas de 6 tipos (do topo para a base): pisolítica, fragmentada, mosqueada, roxa, manganesífera e marrom. Todas são compostas por goethita (predominante nas partes inferior e superior) e hematita (predominante na porção intermediária). As lateritas superiores foram retrabalhadas. Na laterita manganesífera, os óxidos de Mn (hollandita e pirolusita) ocorrem em veios relacionados a evento tardio na formação das lateritas. O principal mineral de Nb é Nb-rutilo presente em todo o perfil, formado juntamente com Ce-pirocloro, Nb-goethita e cerianita. Nb-brookita formada a partir do Nb-rutilo ocorre como esférulas com estrutura Liesegang. Nb-rutilo e Nb-brookita incorporam Nb pela substituição [Fe3+ + (Nb, Ta) = 2Ti]. As lateritas têm teor médio de Nb2O5 de 2,91% e 5,00% de TiO2. A mineralização associada de ETR é de 3 tipos: primária, supergênica e clástica-autigênica (em bacias cársticas). O SC de núcleo tem concentração média de 0,70% de ETR2O3 (thorbastnäsita) e uma zona mais rica (1,48% de ETR2O3) com monazita e bastnasita. Nas lateritas inferiores (1,02% de Ce2O3) a cerianita-(Ce) intercalada na goethita foi formada pela decomposição do Ce-pirocloro; na laterita manganesífera (1,41% de Ce2O3) ocorre cerianita-(Ce) intercrescida com hollandita; nas lateritas superiores ocorre florencita-(Ce). Na bacia Esperança (233 m de espessura) a mineralização de ETR nas brechas do pacote inferior, ricas em fragmentos de SC, e nos ritmitos lacustres do pacote intermediário (com clastos de materiais ferruginosos relacionados aos estágios iniciais da alteração do siderita carbonatito) é principalmente clástica (monazita e florencita). No pacote superior (0 – 73 m, com 1,72 wt% de ETR2O3), formado por argila carbonosa rica em matéria orgânica, que marca a inversão do relevo, a florencita-(Ce) é autigênica, formada principalmente por dissolução de minerais da laterita retrabalhada, transporte e deposição em ambiente alcalino rico em Al e P. A evolução mineralógica e geoquímica dos ETR nesses três domínios são integrados em um modelo compreensível para o comportamento ETR no MSLD. / The Morro dos Seis Lagos Nb (REE, Ti) lateritic deposit is derived from a primary siderite carbonatite (SC). The country rock gneiss was affected by potassic fenitization (phlogopite and orthoclase + monazite, fluorapatite and bastnäsite). Three types of SC are recognized: core SC (siderite and hematite + Ce-Ba-pirocloro; Nb-brookita; Ti-maghemita; and thorbastnäsite; a REE-P-rich variety of CSC (siderite and hematite, + Ce-Ba-pyrochlore, monazite and bastnäsite; a border SC (BSC) (siderite and barite + gorceixite, rabdophane and Pb-Ba-pyrochlore). Fluid inclusion and C and O isotopic data indicate that the CSC is latemagmatic to hydrothermal and the BSC is hydrothermal. The CSC is the richest in Fe and the poorest in Ca siderite carbonatite yet recognized, has high Mn, Ba, Th, Pb, LREE and Nb contents. The high Nb/Ta ratio indicates residual liquids from fractional crystallization. Isotopic data (Sr and Nd) suggest the carbonatite has a mantle origin with essentially no crustal contamination. The Morro dos Seis Lagos Carbonatite Complex represent the uppermost parts of a differentiated carbonatite magmatic system, and the SC is related to latemagmatic- to- carbo-hydrothermal processes. The Nb deposit is associated to 6 laterite types (from top to bottom): pisolitic, fragmented, mottled, purple, manganiferous, brown. All are composed of goethite (in the lower and upper laterites) and hematite (in the intermediate types). The upper laterites were reworked. In the manganiferous laterite Mn-oxides (hollandite and pyrolusite) occur as veins formed in a late event during the development of the laterite. The main Nb ore mineral is Nb-rich rutile, which occurs in all laterites and is formed together with Ce-pyrochlore, Nb-rich goethite and cerianite. Nb-rich brookite formed from Nb-rich rutile occurs as broken spherules with Liesegang ring structure. Nb-rich rutile and Nb-rich brookite incorporate Nb following the [Fe3+ + (Nb, Ta) for 2Ti] substitution. The laterites have an average 2.91 wt.% of Nb2O5 and an average 5.00 wt.% of TiO2. The associated REE mineralization is of 3 types: primary, supergene and clastic-authigenic (karstic basins). The CSC has an average 0.70 wt% of REE2O3 (thorbastnäsite) and a rich zone 1.48wt.% of REE2O3 (monazite and bastnäsite). In the lower laterites (1.02 wt% Ce2O3) cerianite-(Ce) occurs as bands intercalated with goethite formed by pyrochlore breakdown; at the manganiferous laterite (1,41 wt.% Ce2O3) cerianite-(Ce) occurs intergrown with hollandite; florencite-(Ce) occurs in the reworked laterites. At the Esperança Basin (233m thick) the REE mineralization in breccia in lower package, rich in CSC fragments, and in rythmites in the intermediary package rich ferruginous materials related to the early stages of siderite carbonatite alteration, is clastic (monazite and florencite). In the upper package (0 – 73 m, 1,72 wt% of ETR2O3), formed by carbonaceous clay rich in organic matter, which marks the relief inversion, occurs an authigenic florencite-(Ce), fomed by dissolution of minerals from the reworked laterites, transportation and deposition in a alkaline environment rich in Al and P. The mineralogical and geochemical evolution of the REE is these three domains are integrated into a comprehensible model for the REE behavior at the MSLD.

O depósito do Morro dos Seis Lagos (DMSL) é o maior depósito de Nb até hoje encontrado. A mineralização é laterítica, ocorrendo associada ao corpo principal do Complexo Carbonatítico Seis Lagos (CCSL). Este trabalho apresenta resultados da datação U-Pb (por MC-ICP-MS com LASER acoplado) de zircões de sete amostras abrangendo todos os tipos litológicos conhecidos no CCSL/DMSL: rocha encaixante (gnaisse), veio de feldspato na encaixante, siderita carbonatito (3 amostras) e crostas ferruginosas mineralizadas em Nb (2 amostras). Os zircões do gnaisse e do veio de feldspato forneceram idades de, respectivamente, 1.826 ± 9 Ma e 1.839 ± 29 Ma, as quais mostram que a litofácies Tarsira do Complexo Cauaburi (o embasamento do Domínio Imeri na Província Rio Negro) é de 16 Ma a 29 Ma mais antiga do que o anteriormente suposto. Os zircões de duas amostras de carbonatito forneceram idades de 1.837 ± 8 Ma e 1.841 ± 7 Ma, as mais antigas encontradas no Domínio Imeri no Brasil, interpretadas como relacionadas a rochas profundas, cujos zircões foram capturados pelo magma carbonatitico durante sua ascensão A idade de 1.818 ± 8 Ma obtida em zircões da crosta pisolítica indica que o Complexo Cauaburi foi uma importante fonte para os clastos presentes nesta crosta. A idade de 1.873 ± 70 em zircões da crosta fragmentada pode indicar que rochas mais antigas, de outra provincia, também participaram como fonte de clastos para a cobertura laterítica do CCSL. Os zircões de uma amostra de carbonatito da parte central do corpo forneceram duas idades: 1.841 ± 7 Ma e 1.457 ± 71 Ma. Esta última idade é interpretada como a idade máxima do CCSL. Análises por microssonda eletrônica indicam que os zircões mesoproterozoicos têm alguma afinidade com carbonatito. A possibilidade do CCSL ter uma idade mesoproterozoica é discutida à luz do atual conhecimento da evolução geológica da Província Rio Negro, concluindo-se por uma relação com a evolução do Cinturão K’Mudku. / The Morro dos Seis Lagos deposit (MSLD) is the world’s largest Nb-deposit. The lateritic mineralization occurs associated to the major body of the Seis Lagos Carbonatite Complex (SLCC). This paper presents results of U-Pb dating (by MC-ICP-MS, coupled to LASER) of zircons from seven samples that cover all of the known lithotypes in the SLCC/MSLD: host rock (gneiss), feldspar/kaolin intercalation in the host rock, siderite carbonatite (3 samples), and ferriferous Nb-mineralized crust (2 samples). Zircons from the gneiss and the feldspathic vein provided ages of 1.826 ± 9 Ma and 1.839 ± 29 Ma, respectively, which implies that the lithofacies Tarsira of the Cauaburi Complex (the basement of the Imeri Domain in the Rio Negro Province) is 16 Ma to 29 Ma older than previously supposed. Zircons from two carbonatite samples provided ages of 1.837 ± 8 Ma and 1.841 ± 7 Ma which are interpreted as ages of deeper host rocks whose zircons were extracted by the rising carbonatitic magma The age of 1.818 ± 8 Ma obtained in zircons from the pisolitic crust indicate the Cauaburi Complex as the main source of clasts for this crust. The age of 1.873 ± 70 in zircons from the fragmented crust may indicate that rocks from another province older than the Rio Negro Province also contributed as source of clasts to the SLCC lateritic cover. The zircons of a carbonatite sample from the central part of the carbonatite body yield two ages: 1.841 ± 7 Ma and 1.457 ± 71 Ma. The late age is interpreted as the maximum age of the SLCC. Analysis by electron microprobe reveals some evidences that the mid-Proterozoic zircons could be carbonatite zircons. The possible age of 1.457 Ma for the SLCC is discussed in view of the present knowledge on the geology of the Rio Negro Province; a relation with the evolution of the K'Mudku Belt is prognosticated.