Tesi sul tema "Mineralogy"

Orientador: Sebastião Gomes de Carvalho
Banca: Aroldo Misi
Banca: Yociteru Hasui
Banca: Jorge Silva Bettencourt
Banca: Antenor Zanardo
O presente trabalho reúne 3 artigos científicos, já formalizados para publicação em revistas internacionais, foi confeccionado para ser apresentado como tese de doutorado
Artigos em inglês, introdução e resumo em português
Resumo: O depósito de Fortaleza de Minas vem sendo estudado a mais de 20 anos desde a sua descoberta em 1983 e apresenta similaridades com outros depósitos komatiíticos arqueanos descritos na literatura. Sua configuração atual reflete ação de processos metamórficos e deformacionais diversos gerando novos tipos de minério sem, no entanto, perder sua identidade primária komatiítica e permitindo reconstruir sua faciologia vulcanológica. Contexto regional A região de Fortaleza de Minas corresponde a um bloco cratônico arqueano retrabalhado na Faixa Móvel Brasília de idade neoproterozóica. Os terrenos granito-greenstone afloram em meio à metasedimentos supracrustais proterozóicos dos grupos Araxá e Canastra que compõe a nappe de Passos. O bloco arqueano corresponde ao limite sul do antigo Craton do Paramirim fazendo contato com o cinturão granulítico de Alfenas a Sul. Estudos geológicos e geofísicos recentes demonstram que esta área corresponde a uma zona de junção entre dois blocos crustais, denominados Brasília e São Paulo, que representam duas paleo-placas separadas pela zona de sutura de Alterosa. No bloco Brasília ocorrem os greenstone belts de Morro do Ferro e Pihum-i. As idades obtidas para estes greenstone belts estão distribuídas entre 2,8 e 2,9 Ga e 2,9 e 3,1 Ga respectivamente e são discutidas no capítulo 3. O greenstone belt do Morro do Ferro ocorre como faixas descontínuas e estreitas estruturadas em quilhas sinclinais representando as raízes desta seqüência greenstone. Estão fortemente deformadas e cortadas pelo sistema sinistral de falhas transcorrentes Campo do Meio responsável pela estruturação sigmoidal da região (capítulo 2) (Fig. 1, pg. 33 e Fig. 1, pg.4). O Greenstone Belt Morro do Ferro é representado por derrames komatiíticos e mais restritamente toleíticos com intercalações subordinadas de sedimentos químicos exalativos...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: After 20 years of exploration and mining in the Fortaleza de Minas nickel deposit (formerly known as O'Toole) a better understanding of the geological framework and the volcanic environment was achieved. The different ore types observed in the deposit and its distribution revealed the original volcanic setting for the ore formation and also the geological evolution and transformation of the different ore types. The nickel mineralization is classified as a Type 1 deposit (Lesher and Keays, 2002). It is associated to an open trough structure of lava pathway. Later metamorphism and deformation obliterated most of the original volcanic textures and promoted a strong stretching of the ore zone and remobilization of the massive breccia ore along a major shear zone installed at the base of an upper fractionated host flow unit in contact with a footwall BIF. In the Neoproterozoic Brasiliano Cycle (0.6 Ga) a new ore type was formed of hydrothermal origin with extremely high nickel grades and PGE nuggests...(Complete abstract, click electronic address below)
Doutor

The underlying research that resulted in this doctoral dissertation was performed at the Division of Economic Geology and Petrology of the Department of Mineralogy, TU Bergakademie Freiberg between 2011 and 2014. It was the primary aim of this thesis to develop and test novel applications for the technology of ‘Automated Mineralogy’ in the field of economic geology and geometallurgy. A “Mineral Liberation Analyser” (MLA) instrument of FEI Company was used to conduct most analytical studies. This automated system is an image analysis system based on scanning electron microscopy (SEM) image acquisition and energy dispersive X-ray spectrometry which can be used to determine both quantitative mineralogical data and mineral processing-relevant parameters. The analyses can be conducted with unconsolidated and solid rocks but also with ores and products of the mineral processing and recycling industry. In consequence of a first-time broadly-based and comprehensive literature review of more than 1,700 publications related to all types of automated SEM-based image analysis systems several trends in the publication chronicle were observed. Publications related to mineral processing lead the field of automated mineralogy-related publications. However, this is with a somewhat smaller proportion than expected and with a significant decrease in share between around 2000 and 2014. The latter is caused by a gradual but continuous introduction of new areas of application for automated mineralogical analysis such as the petroleum industry, petrology or environmental sciences. Furthermore, the quantity of automated mineralogy systems over time was carefully assessed. It is shown that the market developed from many individual developments in the 1970s and 1980s, often conducted from research institutes, e.g., CSIRO and JKMRC, or universities, to a duopoly - Intellection Pty Ltd and JKTech MLA - in the 1990s and 2000s and finally to a monopoly by FEI Company since 2009. However, the number of FEI’s competitors, such as Zeiss, TESCAN, Oxford Instruments, and Robertson CGG, and their competing systems are increasing since 2011. Particular focus of this study, published in three research articles in peer-reviewed international journals, was the development of suitable methodological approaches to deploy MLA to new materials and in new contexts. Data generated are then compared with data obtained by established analytical techniques to enable critical assessment and validation of the methods developed. These include both quantitative mineralogical analysis as well as methods of particle characterisation. The first scientific paper “Use of Mineral Liberation Analysis (MLA) in the Characterization of Lithium-Bearing Micas” deals with the field of mineral processing and describes the characterisation of lithium-bearing zinnwaldite mica - as potential natural resource for lithium - by MLA as well as the achievement of mineralogical association data for zinnwaldite and associated minerals. Two different approaches were studied to comminute the samples for this work, conventional comminution by crusher as well as high-voltage pulse selective fragmentation. By this study it is shown that the MLA can provide mineral data of high quality from silicate mineral resources and results very comparable to established analytical methods. Furthermore, MLA yields additional relevant information - such as particle and grain sizes as well as liberation and grade-recovery data. This combination of quantitative data cannot be attained with any other single analytical method. The second article “Characterisation of graphite by automated mineral liberation analysis” is also located in the field of mineral processing. This research article is the first published contribution on the characterisation of graphite, an important industrial mineral, by MLA respectively an automated mineralogy-related analytical method. During this study graphite feeds and concentrates were analysed. By this study it is shown that it is possible to gather statistically relevant data of graphite samples by MLA. Furthermore, the MLA results are validated by quantitative X-ray powder diffraction as well as particle size determinations by laser diffraction and sieve analysis. The third research paper “Nature and distribution of PGE mineralisation in gabbroic rocks of the Lusatian Block, Saxony, Germany” deals with the scientific field of geoscience. In this study it is shown that it is possible to obtain a significant body of novel mineralogical information by applying MLA analysis in a region previously regarded as being well-studied. The complex nature and relatively large distribution of the occurring platinum group minerals (PGM) is well illustrated by this contribution. During previous light microscopic studies and infrequent electron microprobe measurements only a handful isolated PGM grains were identified and characterised. In this investigation, using the samples of previous studies, 7 groups of PGM and 6 groups of associated tellurides as well as in total more than 1,300 mineral grains of both mineral groups were identified. Based on the data obtained, important insight regarding mineral associations, mineral paragenesis and the potential genesis of the PGM is obtained. Within this context, the value of MLA studies for petrological research focused on trace minerals is documented. MLA yields results that are both comprehensive and unbiased, thus permitting novel insight into the distribution and characteristics of trace minerals. This, in turn, is immensely useful when developing new concepts on the genesis of trace minerals, but may also give rise to the development of a novel generation of exploration tools, i.e., mineralogical vectors towards exploration akin to currently used geochemical vectors. The present dissertation shows that automated mineralogy by using a Mineral Liberation Analyser is able to deliver a unique combination of quantitative data on mineralogy and several physical attributes that are relevant for ore geology and mineral processing alike. It is in particular the automation and unbiasedness of data, as well as the availability of textural data, size and shape information for particles and mineral grains, as well as mineral association and mineral liberation data that define major advantages of MLA analyses - compared to other analytical methods. Despite the fact that results are obtained only on 2-D polished surfaces, quantitative results obtained compare well/very well to results obtained by other analytical methods. This is attributed mainly due to the fact that a very large and statistically sound number of mineral grains/particles are analysed. Similar advantages are documented when using the MLA as an efficient tool to search for and characterise trace minerals of petrological or economic significance
Die Forschung die der vorliegenden kumulativen Dissertation (‚Publikationsdissertation‘) zugrunde liegt wurde im Zeitraum 2011-2014 am Lehrstuhl für Lagerstättenlehre und Petrologie des Institutes für Mineralogie der TU Bergakademie Freiberg durchgeführt. Das primäre Ziel dieser Arbeit war es neue Einsatzmöglichkeiten für die Technik der Automatisierten Mineralogie im Gebiet der Lagerstättenkunde und Geometallurgie zu entwickeln und zu testen. Im Mittelpunkt der wissenschaftlichen Studien stand die analytische Nutzung des Großgerätes „Mineral Liberation Analyser“ (MLA) der Firma FEI Company. Dieses automatisierte System ist ein Bildanalysesystem und basiert auf der Erfassung von Rasterelektronenmikroskopiebildern und energiedispersiver Röntgen-spektroskopie. Mit Hilfe der MLA-Analysetechnik lassen sich sowohl statistisch gesichert quantitative mineralogisch relevante als auch Aufbereitungsprozess-relevante Parameter ermitteln. Die Analysen können sowohl an Locker- und Festgesteinen als auch an Erzen und Produkten der Aufbereitungs- und Recyclingindustrie durchgeführt werden. Infolge einer erstmaligen, breit angelegten und umfassenden Literaturrecherche von mehr als 1.700 Publikationen im Zusammenhang mit allen Arten von automatisierten REM-basierten Bildanalysesystemen konnten verschiedene Trends in der Publikations¬historie beobachtet werden. Publikationen mit Bezug auf die Aufbereitung mineralischer Rohstoffe führen das Gebiet der Automatisierte Mineralogie-bezogenen Publikationen an. Der Anteil der Aufbereitungs-bezogenen Publikationen an der Gesamtheit der relevanten Publikationen ist jedoch geringer als erwartet und zeigt eine signifikante Abnahme des prozentualen Anteils zwischen den Jahren 2000 und 2014. Letzteres wird durch eine kontinuierliche Einführung neuer Anwendungsbereiche für die automatisierte mineralogische Analyse, wie zum Beispiel in der Öl- und Gasindustrie, der Petrologie sowie den Umweltwissenschaften verursacht. Weiterhin wurde die Anzahl der Systeme der Automatisierten Mineralogie über die Zeit sorgfältig bewertet. Es wird gezeigt, dass sich der Markt von vielen einzelnen Entwicklungen in den 1970er und 1980er Jahren, die oft von Forschungsinstituten, wie z. B. CSIRO und JKMRC, oder Universitäten ausgeführt wurden, zu einem Duopol - Intellection Pty Ltd und JKTech MLA - in den 1990er und 2000er Jahren und schließlich seit 2009 zu einem Monopol der FEI Company entwickelte. Allerdings steigt die Anzahl der FEI-Konkurrenten, wie Zeiss, TESCAN, Oxford Instruments und Robertson CGG, und deren Konkurrenzsysteme seit 2011. Ein Schwerpunkt der drei von Experten begutachteten und in internationalen Fachzeitschriften publizierten Artikel dieser Studie war die Entwicklung eines geeigneten methodischen Ansatzes um die MLA-Technik für neue Materialien und in neuem Kontext zu verwenden. Die erzeugten Daten wurden mit Daten die von etablierten analytischen Techniken gewonnen wurden verglichen, um eine kritische Bewertung und Validierung der entwickelten Methoden zu ermöglichen. Dazu gehören sowohl quantitative mineralogische Analysen als auch Methoden der Partikelcharakterisierung. Der Schwerpunkt der Studie zum ersten Fachartikel „Use of Mineral Liberation Analysis (MLA) in the Characterization of Lithium-Bearing Micas“ liegt im Gebiet der Aufbereitung mineralischer Rohstoffe. Er beschreibt die Charakterisierung von Zinnwaldit-Glimmer - einem potentiellen Lithium-Rohstoff - durch die MLA-Technik sowie das Erringen von Mineralverwachsungsdaten für Zinnwaldit und assoziierter Minerale. Dabei wurden zwei unterschiedliche Wege der Probenzerkleinerung des Rohstoffes untersucht. Zum einen erfolgte eine konventionelle Zerkleinerung der Proben mittels Brecher und Mühle, zum anderen eine selektive Zerkleinerung durch Hoch¬spannungsimpulse. Es konnte aufgezeigt werden, dass die automatisierte Rasterelektronen¬mikroskopie-basierte Bildanalyse mittels MLA von silikatischen Rohstoffen Mineral¬informationen von hoher Güte zur Verfügung stellen kann und die Ergebnisse gut vergleichbar mit etablierten analytischen Methoden sind. Zusätzlich liefert die MLA weitere wertvolle Informationen wie zum Beispiel Partikel-/Mineralkorngrößen, Aussagen zum Mineralfreisetzungsgrad sowie Gehalt-Ausbring-Kurven des Wertstoffes. Diese Kombination von quantitativen Daten kann mit keiner anderen analytischen Einzelmethode erreicht werden. Der zweite Fachartikel „Characterisation of graphite by automated mineral liberation analysis“ ist ebenfalls im Fachgebiet der Aufbereitung mineralischer Rohstoffe angesiedelt. Während dieser Studie wurden Edukte und Produkte der Aufbereitung von Graphit-Erzen untersucht. Der vorliegende Artikel ist der erste in einer internationalen Fachzeitschrift publizierte Beitrag zur Charakterisierung des Industrieminerals Graphit mittels MLA-Technik bzw. einer Analysenmethode der Automatisierten Mineralogie. Mit der Studie konnte gezeigt werden, dass es möglich ist, auch mit der MLA statistisch relevante Daten von Graphitproben zu erfassen. Darüber hinaus wurden die Ergebnisse der MLA-Analysen durch quantitative Röntgenpulverdiffraktometrie sowie Partikelgrößen-bestimmungen durch Laserbeugung und Siebanalyse validiert. Der dritte Fachartikel „Nature and distribution of PGE mineralisation in gabbroic rocks of the Lusatian Block, Saxony, Germany“ ist im Gegensatz zu den ersten beiden Artikeln im Gebiet der Geowissenschaften angesiedelt. In dieser Studie wird gezeigt, dass es möglich ist mittels MLA-Analyse eine signifikante Anzahl neuer Daten von einem eigentlich schon gut untersuchten Arbeitsgebiet zu gewinnen. So konnte erst mit der MLA die komplexe Natur und relativ große Verbreitung der auftretenden Platingruppenelement-führenden Minerale (PGM) geklärt werden. Während früherer lichtmikroskopischer Analysen und einzelner Elektronenstrahlmikrosonden-Messungen konnten nur eine Handvoll weniger, isolierter PGM-Körner nachgewiesen und halbquantitativ charakterisiert werden. In der vorliegenden Studie konnten nun, an den von früheren Studien übernommenen Proben, 7 PGM-Gruppen und 6 assoziierte Telluridmineral-Gruppen mit insgesamt mehr als 1.300 Mineralkörnern beider Mineralgruppen nachgewiesen werden. Auf der Grundlage der gewonnenen Daten wurden wichtige Erkenntnisse in Bezug auf Mineralassoziationen, Mineralparagenese und zur möglichen Genese der PGM erreicht. In diesem Zusammenhang wurde der Wert der MLA-Studien für petrologische Forschung mit dem Fokus auf Spurenminerale dokumentiert. Die MLA liefert Ergebnisse, die sowohl umfassend und unvoreingenommen sind, wodurch neue Einblicke in die Verteilung und Charakteristika der Spurenminerale erlaubt werden. Dies wiederum ist ungemein nützlich für die Entwicklung neuer Konzepte zur Genese von Spurenmineralen, kann aber auch zur Entwicklung einer neuen Generation von Explorationswerkzeugen führen, wie zum Beispiel mineralogische Vektoren zur Rohstofferkundung ähnlich wie derzeit verwendete geochemische Vektoren. Mit der vorliegenden Dissertationsschrift wird aufgezeigt, dass Automatisierte Mineralogie mittels Mineral Liberation Analyser eine einzigartige Kombination an quantitativen Daten zur Mineralogie und verschiedene physikalische Attribute, relevant sowohl für die Lagerstättenforschung als auch für die Aufbereitung mineralischer Rohstoffe, liefern kann. Im Vergleich zu anderen etablierten analytischen Methoden sind es insbesondere die Automatisierung und Unvoreingenommenheit der Daten sowie die Verfügbarkeit von Gefügedaten, Größen- und Forminformationen für Partikel und Mineralkörner, Daten zu Mineralassoziationen und Mineralfreisetzungen welche die großen Vorteile der MLA-Analysen definieren. Trotz der Tatsache, dass die Ergebnisse nur von polierten 2-D Oberflächen erhalten werden, lassen sich die quantitativen Ergebnisse gut/sehr gut mit Ergebnissen anderer Analysemethoden vergleichen. Dies kann vor allem der Tatsache zugeschrieben werden, dass eine sehr große und statistisch solide Anzahl von Mineralkörnern/Partikeln analysiert wird. Ähnliche Vorteile sind bei der Verwendung der MLA als effizientes Werkzeug für die Suche und Charakterisierung von Spurenmineralen von petrologischer oder wirtschaftlicher Bedeutung dokumentiert

Master of Science
Department of Geology
George R. Clark II
Conulariids are one of the most enigmatic groups of fossil organisms, and have been stimulating debates since the late 19th century. Many major questions remain; for example, three independent researchers (Babcock and Feldman, 1986b; Oliver and Coates, 1987; Van Iten, 1992b) reported three different mineralogies for the conulariid test within a six-year period, and are not known to have reached an agreement. Conulariid morphology is also debated, and many workers seem unable to agree on the basic architecture of the test or how it grows. Conulariid workers have also attempted to determine the taxonomic classification of conulariids, especially whether they have cnidarian affinities or occupy their own phylum. My work attempts to clarify some of these issues, as well as determine whether any morphological variation exists within single species of conulariids in different paleoenvironments. To this end, I have collected and prepared specimens for examination by scanning electron microscopy, transmitted polarized light microscopy, energy-dispersive spectrophotometery, and x-ray defractometry. Results include evidence for the presence of organic matrix in the conulariid test microstructure, the presence of three types of lamellae in the test, and support for carbonate-rich apatite [Ca5(PO4,CO3)3(OH,F)] mineralogy. Details of the test microstructure add further support for a coronatid scyphozoan affinity. The conulariid species examined here displayed no microstructural or mineralogical variation between different paleoenvironments (unless two of the species are actually environmental varieties, which seem unlikely).

Ti-rich minerals occur in xenoliths of metasomatized mantle peridotites, MARID and PIC. Xenocrysts produced by disaggregation during the intrusion have equivalent compositions. Early crystallization in the first intrusive stage in kimberlites and related rocks produces olivine phenocrysts that may have trapped inclusions of co-crystallizing rutile, Mg-rich ilmenite to geikielite and chromite. Geikielite may replace Ti-bearing minerals of the xenocrystic suite, producing a suite of magnesian ilmenites of intermediate compositions that follow an Mg enrichment trend depending on the grade of interaction xenocrysts/magma. Phlogopite microphenocrysts can start to crystallize in this stage. A second magmatic stage produces saturation in pyrophanite, that can precipitate or react with all the above Ti-rich minerals, producing crystallization of a suite of intermediate manganoan ilmenites whose compositions depend on that of the replaced Ti-mineral and the grade of interaction of the magma with the above crystals. Lately in this stage, qandilite-ulvöspinel-magnetite start to crystallize, together with perovskite, along with phlogopite microphenocrysts. Finally, the crystallization of ulvöspinel-magnetite crystals may be produced in disequilibria, inducing the development of atoll textures. Groundmass phlogopite crystallize in the late magmagtic stage. Monticellite can be formed in this stage. Interstitial glass can be produced at the end of this stage. Subsolidus hydrothermal processes are widespread in most of the kimberlites, with replacement of the early minerals by hydrous and carbonic fluids of kimberlitic provenance. Olivines and glass are replaced by serpentines and carbonates. A sequence of ilmenites (geikielite followed by pyrophanite) can precipitate directly or replace the above Ti-bearing minerals. Spinels and perovskites may also be replaced by Ti hydrogarnets and late perovskite or kassite accompanied by aeschynite. The composition of the replacing ilmenite depends on that of the replaced mineral. Hence, these ilmenites can retain Nb, Cr, Zr when replacing rutile or perovskite, chromite or crichtonite. Therefore, the trace composition of ilmenite cannot be used to extract petrogenetic information. Mg- or Mn-ilmenites cannot be used as DIM because they are very late minerals formed during the intrusion. When plotting the composition of these minerals in the existing IUGS classification diagrams there is an extensive overlap among kimberlites and related rocks. Thus the existing classification diagrams are not useful and we propose some amendments to the existing classification.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A mina Bom Futuro é atualmente uma das maiores produtora de estanho do país, com uma produção média anual nos últimos 10 anos de cerca de 2400 toneladas de estanho. As atividades industriais de extração de cassiterita na mina se concentram no morro Bom Futuro e adjacências, em depósitos primários e secundários, respectivamente. No morro Bom Futuro são reconhecidos dois pipes brechados alojados em gnaisses e anfibolitos, que são cortados por diques radiais e anelares de pórfiros graníticos com topázio, os quais são incluídos na Suíte Intrusiva Granitos Últimos de Rondônia (998 a 974 Ma). Pelo menos duas fases distintas de mineralização primária de estanho são identificadas com idades 40Ar/39Ar em zinnwaldita de 994±3 Ma e 993±3 Ma e são representadas por lentes, veios e vênulas de pegmatito e de quartzo. O pegmatito estudado ocorre na porção nordeste do morro, onde aparece hospedado em brechas de pipe e dique de topázio riólito pórfiro e cortado por dique de topázio granito pórfiro. Trata-se de um dique com mais de 200 m de comprimento, espessura variando 3 a 12 metros e de atitude geral N20E/45°SE. Na seção estudada com detalhe, o pegmatito mostra um zoneamento interno bem distinto, dado por camadas ou leitos subconcordantes entre si e com as paredes do dique. Pelo menos três zonas foram reconhecidas com base na mineralogia dominante, são elas do muro ao teto: zona do quartzo e topázio, zona do feldspato potássico e mica, e zona granítica (quartzo e feldspato potássico). Uma provável quarta zona não foi observada, mas segundo os garimpeiros, um leito de até 10 cm de espessura de cassiterita maciça ocorre de modo descontínuo junto ao muro do corpo. A estrutura das zonas é maciça e a granulação varia de média a grossa na zona granítica para grossa a muito grossa ou gigante (?) nas outras...
The mine Bom Futuro is currently one of the largest tin producer in the country with an average annual production over the past 10 years around 2400 tonnes of tin. The extraction industrial activities of cassiterite concentrate on the hill Bom Futuro and surrounding areas in primary and secondary deposits, respectively. On the hill Bom Futuro two breccia pipes are recognized hosted in gneisses and amphibolites, which are cut by radial and ring dikes of granite porphyry with topaz, which are included in the Intrusive Suite Latest Granites of Rondônia (998-974 Ma). At least two distinct phases of primary tin mineralization are identified with zinnwaldita 40Ar/39Ar ages of 994 ± 3 Ma and 993 ± 3 Ma and is represented by lenses, veins and venules of quartz and pegmatite. The studied pegmatite occurs in the northeastern portion of the hill, where it appears hosted in breccias pipe and topaz rhyolite porphyry dike cut by topaz granite porphyry dike. It is a dike over 200 meters in length, thickness ranging 3-12 meters and general attitude N20E/45 ° SE. In the studied section in detail, the pegmatite shows a very distinct internal zoning, given by layers or beds sub concordant among themselves and with the walls of the dike. At least three zones were recognized based on the dominant mineralogy, they are from the wall to the ceiling: zone of quartz and topaz, zone of mica and feldspar, and granitic zone (quartz and feldspar).A possible fourth zone was not observed, but according to the miners, a bed with 10 cm thick of massive cassiterite occurs discontinuously along the wall of the body. The structure of the zones are massive and the granulation varies from medium to coarse in the granite zone and coarse to very coarse or giant (?) In the other two. The primary mineralogy is relatively simple: the quartz is gray to milky white, the... (Complete abstract click electronic access below)

A Mina de diamantes de Romaria está localizada no perímetro urbano da cidade de Romaria, na região oeste de Minas Gerais. Durante os trabalhos de mineração executados nos últimos cem anos, foi lavrada uma área de aproximadamente 1 km2 de sedimentos. O local está situado na borda NE da Bacia do Paraná, na margem direita do Rio Bagagem, entre os Ribeirões Água Suja e Marrecos. Neste local vem sendo lavrado um conglomerado polimítico da Formação Uberaba, Grupo Bauru, pertencente ao Cretáceo Superior. Ele é constituído por clastos de micaxistos, anfibolitos, filitos e veios pegmatóides do Pré-Cambriano; arenitos da Formação Botucatu e basaltos da Formação Serra Geral. Possui matriz areno-argilosa onde foram identificadas as fases caulinita, illita e quartzo por difratometria. Sua espessura na área da mina oscila em torno de 6 m. Os minerais pesados separados do conglomerado diamantífero amostrado nas Frentes de Lavra 2 (Ferraria), 6 (Mangueiras) e na Cata exploratória do Sarkis, situada fora da área minerada, são constituídos em sua maior parte por fases opacas, entre as quais se destaca a magnetita, representando 50% em volume do concentrado. Outras fases opacas incluem hematita, ilmenita e fragmentos de lateritos. Entre as fases transparentes, destacase a granada que ocorre nas cores vermelha clara, vermelha escura, roxa, violeta e laranja, além de outros minerais derivados de rochas do embasamento cristalino. Análises químicas realizadas pela microssonda eletrônica revelaram que a ilmenita contém teores de MgO (7,4 - 11,4 % em peso) e de Cr2O3 (0,0 - 2,9 % em peso) típicos de rochas kimberlíticas. Da mesma forma, as granadas correspondem a piropos ricos em Cr2O3 (0,2 - 6,7 % em peso) correspondendo aos grupos G9 (lherzolitos), G5 e G4 (piroxenitos) e G10 (harzburgitos), sendo semelhantes a granadas das principais províncias kimberlíticas conhecidas. O diamante, por sua vez, contém microestruturas típicas semelhantes a diamantes de outras localidades. Foram identificadas trígonos em faces octaédricas, bem como microestruturas de simetria senária semelhantes às observadas em diamantes do lamproíto Argyle, na Austrália. Foram descritas microestruturas quadráticas nos cristais cúbicos, e degraus resultantes da dissolução de planos de crescimento cristalino em superfícies curvas de cristais rombododecaédricos. Atualmente a mina está paralisada desde 1984 devido a uma dívida contraída pela Extratífera de Diamantes do Brasil (EXDIBRA) com o Banco Nacional de Desenvolvimento Social. Apesar do potencial mineral existente no local, qualquer tentava de lavra só poderá ser executada mediante a quitação desta dívida.
The diamond Mine of Romaria is located in the northeast border of the Paraná Sedimentary Basin, nearby the town of Romaria, in western Minas Gerais State, Brazil. The mining place is situated on the right side of the Bagagem River, comprising an area of 1 km2 between the Água Suja and Marrecos streams. At this place diamonds have been washed from a Cretaceous polimictic conglomerate of the Uberaba Formation, Bauru Group, since the end of the nineteen century. This heterogeneous diamond-bearing conglomerate contains large conglomerate blocks of several lithologies with dimensions up to 0.80 m, set in an arenous-clayish matrix where kaolinite, illite and quartz have identified among the clasts such as mica and staurolite schists, phyllites and amphibolites of the Araxá Group, quartzites of the Canastra Group, arenites of the Botucatu Formation and basalts of the Serra Geral Formation. The concentrates obtained by washing the conglomerate contains large amounts of opaques phases mainly magnetite which may reach up to 50% in volume. Other opaques are represented by hematite, ilmenite, rutile, limonite as well as rock fragments of mica schists and complex intergrowths of laterites. The mineralogical assemblages of the transparent phases include staurolite, amphibole, epidote, kyanite, monazite, tourmaline, zircon and diamond as well. Electron micro probe analyses revealed that the ilmenites contain MgO (7.4-11.4 wt%) and Cr2O3 (0.0-2.9 wt%) contents similar to their counterparts of kimberlites from worldwide localities. Moreover, garnets are chromium rich pyropes with Cr2O3 ranging from 0.2 up to 6.7 wt %. The use discriminating diagrams revealed that most of the analysed sampled plot in the fields G9 and G3-G5 corresponding to lherzolitic and pyroxenitic parageneses, respectively. The plots include some rare G10 (harzbugitic) and G0 (unclassified) samples corresponding to garnets derived from rocks of the crystalline basement. Although diamonds have not been mined in the last years a small parcel produced by local diggers (garimpeiros) was available for physical studies including color and crystalline morphology. Several microstructures have been observed in octahedral crystal such as trigons and a pseudo-hexagonal microstructure observed in diamonds from lamproites. Cubic crystals showing the combination of the cube and dodecahedral revealed microstructures of square symmetry. Concerning dodecahedral crystal hillocks produced by dissolution were observed on the rounded faces of the samples. Presently the Mine of Romaria is closed since 1984 due to an old debt contracted by late owner Extratífera de Diamantes do Brasil (EXDIBRA) with the Brazilian Federal Agency of the Banco Nacional de Desenvolvimento Social (BNDES).

Orientador: Washington Barbosa Leite Jr
Banca: Sebastião Gomes de Carvalho
Banca: César D'Abronzo Martinelli
Resumo: A mina Bom Futuro é atualmente uma das maiores produtora de estanho do país, com uma produção média anual nos últimos 10 anos de cerca de 2400 toneladas de estanho. As atividades industriais de extração de cassiterita na mina se concentram no morro Bom Futuro e adjacências, em depósitos primários e secundários, respectivamente. No morro Bom Futuro são reconhecidos dois pipes brechados alojados em gnaisses e anfibolitos, que são cortados por diques radiais e anelares de pórfiros graníticos com topázio, os quais são incluídos na Suíte Intrusiva Granitos Últimos de Rondônia (998 a 974 Ma). Pelo menos duas fases distintas de mineralização primária de estanho são identificadas com idades 40Ar/39Ar em zinnwaldita de 994±3 Ma e 993±3 Ma e são representadas por lentes, veios e vênulas de pegmatito e de quartzo. O pegmatito estudado ocorre na porção nordeste do morro, onde aparece hospedado em brechas de pipe e dique de topázio riólito pórfiro e cortado por dique de topázio granito pórfiro. Trata-se de um dique com mais de 200 m de comprimento, espessura variando 3 a 12 metros e de atitude geral N20E/45°SE. Na seção estudada com detalhe, o pegmatito mostra um zoneamento interno bem distinto, dado por camadas ou leitos subconcordantes entre si e com as paredes do dique. Pelo menos três zonas foram reconhecidas com base na mineralogia dominante, são elas do muro ao teto: zona do quartzo e topázio, zona do feldspato potássico e mica, e zona granítica (quartzo e feldspato potássico). Uma provável quarta zona não foi observada, mas segundo os garimpeiros, um leito de até 10 cm de espessura de cassiterita maciça ocorre de modo descontínuo junto ao muro do corpo. A estrutura das zonas é maciça e a granulação varia de média a grossa na zona granítica para grossa a muito grossa ou gigante (?) nas outras... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The mine Bom Futuro is currently one of the largest tin producer in the country with an average annual production over the past 10 years around 2400 tonnes of tin. The extraction industrial activities of cassiterite concentrate on the hill Bom Futuro and surrounding areas in primary and secondary deposits, respectively. On the hill Bom Futuro two breccia pipes are recognized hosted in gneisses and amphibolites, which are cut by radial and ring dikes of granite porphyry with topaz, which are included in the Intrusive Suite Latest Granites of Rondônia (998-974 Ma). At least two distinct phases of primary tin mineralization are identified with zinnwaldita 40Ar/39Ar ages of 994 ± 3 Ma and 993 ± 3 Ma and is represented by lenses, veins and venules of quartz and pegmatite. The studied pegmatite occurs in the northeastern portion of the hill, where it appears hosted in breccias pipe and topaz rhyolite porphyry dike cut by topaz granite porphyry dike. It is a dike over 200 meters in length, thickness ranging 3-12 meters and general attitude N20E/45 ° SE. In the studied section in detail, the pegmatite shows a very distinct internal zoning, given by layers or beds sub concordant among themselves and with the walls of the dike. At least three zones were recognized based on the dominant mineralogy, they are from the wall to the ceiling: zone of quartz and topaz, zone of mica and feldspar, and granitic zone (quartz and feldspar).A possible fourth zone was not observed, but according to the miners, a bed with 10 cm thick of massive cassiterite occurs discontinuously along the wall of the body. The structure of the zones are massive and the granulation varies from medium to coarse in the granite zone and coarse to very coarse or giant (?) In the other two. The primary mineralogy is relatively simple: the quartz is gray to milky white, the... (Complete abstract click electronic access below)
Mestre

Orientador: Daniel Marcos Bonotto
Banca: Francisco Yukio Hiodo
Banca: Wanilson Luiz Silva
Banca: Rosemarie Rohn Davis
Banca: Antônio Carlos Artur
Resumo: O gás radônio, resultado do decaimento radioativo do 238U e 232Th, é motivo de grande preocupação para o homem. Ele é uma das mais importantes fontes de radiação ionizante de origem natural que as pessoas estão expostas, sendo considerado pela OMS (Organização Mundial da Saúde) como o segundo maior causador de câncer de pulmão. O carvão mineral como qualquer outro combustível fóssil está associado a materiais radioativos naturais, devido principalmente ao seu conteúdo de 238U e 232Th. Para a compreensão do comportamento do gás radônio em área de mineração de carvão e determinar o grau de exposição das pessoas ao gás nesta área, foram determinadas a taxa de exalação de radônio de amostras de carvão, cinza, siltito e tufo vulcânico coletadas na mina Amado Simões PI-08 (Companhia Carbonífera do Cambuí), em Figueira (PR), a concentração de radônio no ar do interior da mina e a concentração de radônio, parâmetros físicos e químicos dos solos próximos à mina. As taxas de exalações foram obtidas por curvas experimentais da concentração de radônio em função do tempo, e variaram de 0,064 a 0,717 Bq/kg.h. Observou-se que o gás radônio entrou em equilíbrio radioativo após 180 horas de análise. A concentrações de radônio dissolvido no ar do interior da mina variaram de 7,2 a 770,5 Bq/m³, observou-se que o radônio tem maior escape das rochas por fraturas presentes nas frentes de lavra e que maior taxa de exalação vem das rochas encaixantes, remetendo em um problema radiológico à área de d... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Radon gas, the result of the radioactive decay of 238U and 232Th, is a matter of great concern to man. It is one of the most important sources of naturally occurring ionizing radiation that people are exposed to and is considered by the World Health Organization (WHO) to be the second largest cause of lung cancer. Mineral coal like any other fossil fuel is associated with natural radioactive materials, mainly due to its content of 238U and 232Th. In order to understand the behavior of the radon gas in the coal mining area and determine the degree of exposure of the people to the gas in this area, the radon exhalation rate of samples of coal, ash, silt, and volcanic tuff collected at the Amado mine Simões PI-08 (Companhia Carbonífera do Cambuí), in Figueira (PR), the radon concentration in the air inside the mine and the radon concentration, physical and chemical parameters of the soils near the mine. The exhalation rates were obtained by experimental curves of the radon concentration as a function of time, and ranged from 0.064 to 0.717 Bq / kg.h. It was observed that the radon gas entered into radioactive equilibrium after 180 hours of analysis. The concentrations of radon dissolved in the air inside the mine varied from 7.2 to 770.5 Bq / m³, it was observed that the radon has greater escape of the rocks by fractures present in the mining fronts and that higher exhalation rate comes from encasing rocks, sending in a radiological problem to the area of discard. The concentrat... (Complete abstract click electronic access below)
Mestre

The Silver Queen mine, southeast of Houston, B.C., consists of a series of epithermal base- and precious-metal bearing veins hosted by Late Cretaceous volcanic rocks of the Tip Top Hill formation. Mineralogically, the veins are complex, displaying several discrete mineralizing stages characterized by the presence of certain sulfide and gangue species. The complexity of the vein mineralogy has presented a problem in assessing the systemic evolution of the hydrothermal system. This study describes in detail the nature of the mineralogy, dividing the assemblages present into four distinct paragenetic stages. Particular attention was paid to the occurrence of potentially economic phases (e.g. electrum). Sulfide phases which were compositionally sensitive to trace element variations were examined by electron microprobe to determine variations on single grain and deposit scales. Microbeam analysis also assisted in the identification of several sulfosalt species. Evaluation of the mineralogy and paragenesis allowed for the assessment of the evolution of the deposit. Paragenetically, the mineralization is divided into four distinct stages. The first stage is characterized by fine grained pyrite and quartz mineralization, with hematite abundant in the assemblage in the central segment of the most extensive (Number Three) vein. Barite, svanbergite, and hinsdalite become abundant towards the south end of the Number Three vein, with marcasite more abundant towards the north. Stage II is dominated by the presence of massive sphalerite and layered carbonate (calcite in the south, manganoan carbonates in the north). Stage III, however, is more complex. Mineralization consists of chalcopyrite, galena, fahlores (tetrahedrite-tennantite), electrum, quartz, and sulfosalts. Included in the sulfosalt assemblage are the unusual Pb-Bi-Cu-Ag species berryite, matildite, gustavite, and aikinite. The final stage of mineralization is volumetrically minor and is dominated by fine-grained quartz, pyrobitumen, and calcite. Minor element trends in tetrahedrites and sphalerites reveal a mineralizing fluid with a high degree of compositional variability. Tetrahedrite grains show well developed oscillatory compositional zoning in Sb, As, Bi, Ag, and Cu, while sphalerites are commonly visually well layered. The latter was found to be the main repository for the unusual metals Ga, Ge, and In, which are found in anomalous levels in Silver Queen ore. The Silver Queen veins are proposed to have evolved from fluids originating at depth to the south of the Number Three vein. Pulses of metal-bearing fluids interacted with cooler groundwaters, producing the observed distribution of assemblages. The presence of Ga, Ge, and In may have been sourced in an organic-rich layer exposed in several locales in the Silver Queen mine area.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

Orientador: César Augusto Moreira
Banca: Ana Olivia Barufi Franco de Magalhães
Banca: Daniel Françoso de Godoy
Resumo: Este trabalho apresenta resultados gerados através de levantamentos geofísicos terrestres de eletrorresistividade e polarização induzida integrado ao reconhecimento geológico de superfície em área potencialmente mineralizada com sulfeto de cobre, localizada a noroeste do município de Caçapava do Sul, sul do Brasil, na região norte da Bacia Sedimentar do Camaquã. A ocorrência mineral é caracterizada por veios de quartzo contidos em sericita clorita quartzo xisto, com impregnações de malaquita, óxidos de ferro. A análise estrutural local revelou a existência de um sistema de fraturas com direções principais N40-50W e N70-80E. O levantamento geofísico consistiu em 6 linhas de tomografia elétrica dispostas de maneira azimutal com distância angular de 30º uma da outra em arranjo Wenner-Schlumberger, com 400 m cada dispostas segundo critérios estruturais previamente estabelecidos. Os modelos de inversão representados através de seções 2D indicaram áreas de baixa resistividade coincidentes com valores de alta cargabilidade predominantemente em profundidades abaixo dos 40 metros, interpretadas como possíveis concentração de sulfetos. A elaboração do modelo 3D possibilitou a geração de mapas multiníveis a cada 10 metros de profundidade a partir da superfície para as variáveis de eletrorresistividade e polarização induzida, que conjuntamente com modelos tridimensionais de isosuperfície para cargabilidade colaborou no mapeamento geométrico, continuidade lateral, profundidade e controle estrutural NE-SW e NW-SE para o corpo mineralizado
Abstract: This paper presents the results generated through geophysical surveys of DC Resistivity and induced polarization integrated with geological reconnaissance of surface in an area potentially mineralized with copper sulfide, located to the northwest of the Caçapava do Sul city, northern region of Camaquã sedimentary basin, southern Brazil. The mineral occurrence is characterized by quartz veins contained in sericite quartz chlorite schist, with impregnations of malachite, iron oxides. The structural analysis of the site revealed the existence of a system of fractures with main directions N40-50W and N70-80E. The geophysical survey consisted in 6 lines of electrical tomography arranged in an azimuthal way with angular distance of 30° from each other in Wenner-Schlumberger arrangement, with 400 m each arranged according to previously established structural criteria. The inversion models represented through 2D sections indicated areas of low resistivity coincident with values of high chargeability predominantly at depths below 40 meters, interpreted as possible concentration of sulfides. The development of the 3D model enabled the generation of multilevel maps every 10 meters of depth from the surface for the resistivity and chargeability variables, which together with three-dimensional models of isosurface for chargeability collaborated on geometric mapping, lateral continuity, depth and structural control NE-SW and SE to the mineralization
Mestre

This project was initiated to determine the effects of cooling conditions on the mineralogy of aluminous cements fired in oxidizing and reducing atmospheres. Using a vertical tube furnace, compositions covering the range of aluminous cements were melted at a predetermined temperature and at various oxygen partial pressures. They were subsequently cooled at different rates. Product identification was undertaken by X-ray diffraction, optical and scanning electron microscopy, and analytical electron microscopy. The clinker microstructures were found to differ radically with cooling rate, and the nature of the phases crystallizing proved to be very sensitive to the Fe²⁺/Fe³⁺ ratio of the parent melt. The order of crystallization and the phase composition of the individual phases were also affected by thermal history. Phases grown with fast undercooling exhibited departures from solid solution limits established under equilibrium. Furthermore, the coexistence of different phase assemblages within a same clinker was pointed out. With respect to the phases determined, more attention was paid to CA and pleochroite, for which latter high resolution transmission electron microscopy studies were carried out. Mixed pleochroitegehlenite intergrowths were characterized. Another aim of the project was to investigate the consequences of the mineralogy of the clinker on reactivity and strength of the cement. To this end, microcalorimetry experiments were performed to study the reactivity of cement up to 24 hours, and the compressive strength development of pastes was measured for ages up to 28 days. The mineralogical transformations taking place during the hydration of cement were explored, using the X-ray diffraction technique. As a result, different trends could be outlined. Reactivity and strength were found to be affected by cooling rate and FeO content of the cement, the respective influence of which differed with the overall chemical composition of the clinker.

This dissertation is focused on the design of the Open Data Repository's Data Publisher (ODR), a web-based central repository for scientific data, primarily focused on mineralogical properties, but also applicable to other data types, including for instance, morphological, textural and contextual images, chemical, biochemical, isotopic, and sequencing information. Using simple web-based tools, the goal of ODR is to lower the cost and training barrier so that any researcher can easily publish their data, ensure that it is archived for posterity, and comply with the mandates for data sharing. There are only a few databases in the mineralogical community, including RRUFF (http://rruff.info) for professionals, and mindat.org (http://www.mindat.org) for amateurs. These databases contain certain specific mineral information, but none, however, provide the ability to include, in the same platform, any of the many datatypes that characterize the properties of minerals. The ODR framework provides the flexibility required to include unforeseen data without the need for additional software programming. Once ODR is completed, the RRUFF database will be migrated into ODR and populated with additional data using other analytical techniques, such as Mössbauer data from Dr. Richard Morris and NVIR data from Dr. Ralf Milliken. The current ODR pilot studies are also described here, including 1) a database of the XRD analysis performed by the CheMin instrument on the Mars Science Laboratory rover Curiosity, 2) the NASA-AMES Astrobiology Habitable Environments Database (AHED), which aims to provide a central, high quality, long-term data repository for relevant astrobiology information, 3) the University of Arizona Mineral Museum (UAMM), with over 21,000 records of minerals and fossils from the museum collection, and 4) the Mineral Evolution Database (MED), that uses the ages of mineral species and their localities to correlate the diversification of mineral species through time with Earth's physical, chemical and biological processes. A good database design requires understanding the fundamentals of its content, so part of this thesis is also focused on developing my skills in mineral analysis and characterization, through the study of the crystal-chemistry of diverse minerals using X-ray diffraction, Raman spectroscopy and microprobe analysis, as principal techniques.

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

Orientador: José Marques Júnior
Coorientador: Milton César Costa Campos
Coorientador: Diego Silva Siqueira
Banca: Marcílio Vieira Martins Filho
Banca: Livia Arantes Camargo
Banca: Zigomar Menezes de Souza
Banca: Ricardo Simão Diniz Dalmolin
Resumo: O trabalho fornece informações sobre a formação da Terra Preta Arqueológica e sua relação com a expressão magnética proveniente de minerais litogenênicos, pedogenéticos e influência antrópica. Os resultados da presença de minerais ferrimagnéticos nos solos de Terra Preta Arqueológica (TPA) pode ser utilizada para compreender o processo de formação destes solos ou utilizar a expressão magnética como indicador agrícola para cultivo nestes solos. O trabalho possui dois objetivos: (i) verificar as influências geológicas, pedogenéticas e antrópicas na suscetibilidade magnética (SM) da TPA e (ii) estudar o potencial da SM como indicadora agrícola e ambiental para cultivo nestes solos. Foram abertos treze perfis com TPA e um perfil de floresta (solo não antropogênico), sendo coletadas amostras por horizonte em cada perfil. Próximo de um dos perfis com TPA foi estabelecido uma malha de 70 x 70 m e coletada amostras de solos em espaçamentos regulares de 10 m na profundidade de 0,0-0,20 m. Nas amostras coletadas, realizou-se a análise textural, fertilidade e análises mineralógicas. A SM foi determinada nos solos, nas cinzas das plantas e fragmentos de cerâmica encontradas nas TPAs. Na malha, também foi determinado o fluxo de CO2 (FCO2), temparatura e umidade. Há uma grande diversidade de minerais nas TPA, entre eles destacam-se: goethitas (0,16 a 21,86 g kg-1), hematitas (0,27 a 45,14 g kg-1), e maghemita (em baixas concentrações). A SM foi maior nos horizontes antrópicos dos perfis co... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The study provides information about the formation of archeological black earth and relation with magnetic expression from lithogenic, pedogenic and anthropogenic minerals. The results of the presence of ferrimagnetic minerals in archeological black earth (ABE) soils can be used to understand the process of formation of these soils or to use magnetic expression as an agricultural indicator for cultivation in these soils. The study has two objectives: i) to verify the geological, pedogenetic and anthropogenic influences on the magnetic susceptibility (MS) of archeoloical black earth (ii) to study the potential of MS as agricultural and environmental indicator for cultivation in these soils. Thirteen archeological black earth profiles and a forest profile (non-anthropogenic soil) were opened, and samples were collected per horizon in each profile. Next to one of the profiles with ABE a grid of 70 m x 70 m was established and soil samples were collected at regular spaced every 10 m at the depth of 0.0-0.20 m. The samples collected determine the textural, fertility and mineralogical analyzes.The MS was determined in soils, in the ashes of plants and ceramic fragments found in ABE. In the grid, the CO2 flux (FCO2), temperature and moisture was also determined. There is a hight diversity of minerals in archeological black earth, among them goethites (0.16 to 21.86 g kg-1 ), hematite (0.27 to 45.14 g kg-1 ), and maghemite (In low concentrations). The MS was higher in the anthropic h... (Complete abstract click electronic access below)
Doutor

A series of pottery samples provided from the survey investigations and excavations from Degirmentepe Mound (Malatya), belonging to Chalcolithic (Ubaid), Early Bronze and Iron Ages, were investigated by petrographic and X-ray diffraction (XRD) analyses to determine their textures, mineralogical compositions and microstructures. The sample microstructures and chemical (semiquantitative) compositions were also studied by scanning electron microscope with energy dispersive X-ray spectrometry (SEM - EDX). The chemical analyses of some samples were further investigated by inductively coupled plasma &ndash
optical emission spectrometry (ICP-OES). Almost all samples were observed to consist of rock fragments, originating from metamorphic and igneous rocks, although larger grain sizes and higher grain to matrix ratios are recorded for Chalcolithic Age samples compared to those samples belonging to Iron Age. XRD investigations on representative samples of the three periods, revealed high abundances of quartz, feldspar, and pyroxene group minerals in all samples, while the presence of hematite and mica minerals were observed both in Chalcolithic and Iron Age samples, but underlying the use of micaceous raw materials mostly in Iron Age. In the XRD traces of the investigated sherds of Chalcolithic and Iron Ages, the absence of clay fractions both in the bulk and oriented samples, supports a minimum firing temperature of around 800- 850 °
C, while the presence of mullite phase both in XRD and SEM &ndash
EDX results showed the possible use of high firing temperatures, in the range of 950&ndash
1050°
C, starting from Chalcolithic Age. Chemical compositions of major oxides obtained ICP &ndash
OES analyses exhibit similar compositions both for Chalcolithic and Iron Age samples. Few exceptions observed may indicate possible use of different raw material and/or different manufacturing technique.

16 samples of increasing metamorphic grade from the Ballachulish Igneous Complex and Aureole, located in the west of Scotland, were studied in order to analyze the sulfide mineralogy and to what extent they were affected by contact metamorphism. The samples were collected from two lithologies, the Creran Succession and the Ballachulish Slate lithology, as well as from the igneous complex. The sulfides of main interest in the samples are pyrite and pyrrhotite. At the onset of contact metamorphism, pyrite disappears while pyrrhotite gets more abundant as metamorphic grade increases. Pyrrhotite also undergoes multiple changes such as 1) elongation and thinning of the grains, 2) development of 120° grain-boundaries, 3) development of pyrite-zones within the pyrrhotite and 4) the decomposition of pyrrhotite and alignment of pyrite along its grain-boundaries at high temperature. The elongation of the grains occurs in both the Creran Succession and the Ballachulish Slate. The rest of the textures, however, can only be found in the Creran Succession. The two lithologies differ by the high graphite content in the Ballachulish Slate. The elongated grains as well as the pyrite inclusions in the pyrrhotite both are strong evidence of recrystallization. The absence of pyrite in the Ballachulish Slate was most probably caused by the buffering properties of the graphite-rich fluid in these rocks, causing more reducing conditions. There is evidence against a heavy, pervasive fluid flow through the aureole. However, the inner contact zone seems to have been affected by a more pronounced fluid flow. This could have been caused by the metamorphic fluid working in conjunction with fluids released from the intrusion. Regarding the mobility of S in the aureole, no strong evidence could be found, other than the decomposition of pyrrhotite grain-boundaries in the high-grade metamorphic samples.

The crystal-chemistry and paragenesis of astrophyllite group minerals (AGM) from over- and undersaturated alkaline rocks has been documented by a combination of electron microprobe analyses, single-crystal and powder X-ray diffraction, Mossbauer spectroscopy, Fourier-transform infrared spectroscopy, nuclear reaction analysis, thermal gravitational analysis, thermal decomposition, wet-chemical methods and optical measurements. A standardized general formula for AGM has been developed, based on 31 anions, and is of the form A2BC7D 2T8O26(OH)4X 0-1, where [10]--[13]A = K, Rb, Cs, H3O+, H2O, or □; [10] B = Na or Ca; [6]C = Mn, Fe2+ Fe3+ Na, Mg, or Zn; D = [6]Ti, Nb, or Zr; [4]T = Si or Al and X = &phis; = F, OH, O, or □. Results from Mossbauer spectroscopy, bond valence sums and thermodynamic calculations indicate F to order at X [&phis;(16)] whereas the monovalent anion sites in the O-sheet are host solely to OH- . On this basis, eight species and two AGM polytypes are recognized, the most recent, niobokupletskite, identified from Mont Saint-Hilaire during the course of this study. The AGM heterophyllosilicate structure consists of two composite sheets stacked along [001] in a 2:1 ratio resulting in a layered HOH structure. Single-crystal X-ray refinements indicate the existence of two kupletskite polytypes, kupletskite-1A and kupletskite-Ma2b2c, the result of polytypic stacking of identical HOH layers. Mossbauer spectroscopy indicates all Fe to be present in the O-sheet, and Fe3+/Fe tot ratios in AGM to range from 0.01 to 0.21, corresponding to 0.05 to 0.56 apfu Fe3+, confirming that Fe 2+ is the dominant valence state for iron in the AGM structure. AGM from oversaturated alkaline intrusions are characterized by a restricted range of Mn/Mn+Fetot (0.03 to 0.69) and enrichments in K, Rb, Ti (with positive values of Nb-Zr) and Si. AGM from undersaturated intrusions display a wide range in Mn/Mn+Fetot, (0.09 to 1.00) and have been further subdivided into a kupletskite subgroup (Mn/Mn+Fetot ≥ 0.50) and an astrophyllite subgroup (Mn/Mn+Fetot < 0.50). Kupletskite subgroup samples are enriched in Na, Mn, Zn, Fe3+, Nb and Zr (with positive values of Nb-Zr), whereas astrophyllite subgroup samples are enriched in K, Ca, Fe2+, Ti, Zr (with negative values of Nb-Zr) and F. Crystal-chemical parameters in AGM (such as Mn/Mn+Fetot and Nb/Nb+Zr) can be used as petrogenetic indicators. At Mont Saint-Hilaire (Quebec), two distinct paragenetic trends are recognized in the AGM population: (1) an oxidizing magmatic to post-magmatic oxidizing trend resulting in enrichment of the AGM in Na, Mn, Fe3+ and Nb, and (2) a reducing trend resulting in enrichment in Ca, Fe2+, Zr and F by hydrothermal or metasomatic processes. The second evolutionary trend is thought to be the result of interaction of an exsolved magmatic fluid with either meteoric waters or sediments. Both trends lend evidence for late-stage mobilization and concentration of high field-strength elements (such as Nb and Zr) in highly alkaline systems.

The meteorite impact that formed the 32-km-diameter Upper Pennsylvanian (285 +/- 23 Ma) West Clearwater structure, situated about 125 km east of the Hudson Bay arc, northern Quebec, formed a sheet of impact melt now exposed on a central ring of islands. At least seven marble enclaves have been mapped in the melt sheet; this report is based on observations made on samples from two of these enclaves. These blocks represent recrystallized remnants of a cover of Middle Ordovician limestone, now completely eroded in the area. While the impact melt was still above its solidus, the locally fossiliferous dolomite-bearing limestone recrystallized to granoblastic calcite + periclase marble. The silica content of the marble led to the formation of a sanidinite-facies assemblage of unusual nesosilicates such as spurrite, Ca5(SiO4)2(CO3), merwinite, Ca 3Mg(SiO4)2, and monticellite, CaMgSiO4. Aluminian srebrodolskite, Ca2(Fe3+,Al)2O 5, the Fe3+-dominant analogue of brownmillerite, Ca 2(Al,Fe3+)2O5, is found in material with a composition similar to "Portland cement clinker". At its type locality, srebrodolskite is attributed to the calcining of ankeritic carbonate. Phase equilibrium and stratigraphic data constrain peak conditions of metamorphism to at least, T ≈ 815º +/- 15ºC, P < 100 bar and X(CO2) > 0.1. Retrograde mineral assemblages indicate that X(CO2) < 0.1 was achieved shortly after peak metamorphism owing to influx of H2O. Portlandite, Ca(OH)2, is one of several species formed during late hydration of the assemblage upon cooling.

The primary and secondary mafic silicates from the Amba Dongar carbonatitic-alkaline complex, Gujarat, India and the Strange Lake peralkaline granitic complex, Quebec-Labrador, Canada are the subject of this investigation of their origin, evolution and relationship to mineralization. Primary minerals are transformed by a variety of processes related to their crystallization history. The most important of these processes are: magma evolution, magma degassing and metasomatism. These processes are commonly associated with the evolution of peralkaline granitic and carbonatitic-alkaline complexes, and with the formation of associated mineral deposits (e.g., fluorite in the Amba Dongar complex; Zr-, REE- (rare-earth elements), Be-, Nb-and Y-rich deposit in the Strange Lake complex). Although all minerals in these complexes may be subject to these changes, the mafic silicates amphibole, pyroxene and mica are of particular interest, as they remain poorly studied and may comprise up to 10 vol.% of the rock. Moreover, they can contain significant quantities of high field-strength elements (HFSE), which may be mobilized following interaction with later fluids, and deposited as secondary minerals in the ore zone.
In the Amba Dongar complex, Na-metasomatism followed by K- (or Mg-) metasomatism resulted in the formation of fenites, with mobilization of HFSE, among other trace elements. Vermiculite was formed by a subsequent stage of hydrothermal alteration, which is also responsible for formation of the fluorite deposit. In the Strange Lake complex, enrichment of the primary arfvedsonitic amphibole in HFSE and REE is related to magmatic evolution, whereas later degassing released sufficient amounts of volatiles and Na that the amphibole became more potassic and aegirine crystallized. This amphibole acted as a sink for trace elements such as Li, HFSE and REE. These elements were remobilized during Na-metasomatism through replacement of amphibole by aegirine, and deposited as secondary, generally Ca-rich, minerals (e.g., winchitic amphibole and biopyriboles) during later, lower-temperature Ca-metasomatism. Primary mafic silicates in alkaline complexes can thus undergo metasomatic reactions that result in the mobilization of elements that contribute to formation of related ore deposits. These findings concerning the solid phases involved in both localities correlate very well with indications of mixing of two distinct fluid phases.

Apatite occurs as an accessory phase throughout the Sudbury Igneous Complex (SIC), Ontario, as well as in the overlying tuffaceous rocks of the Onaping Formation (OF). This investigation was designed to characterize the textural development and composition of apatite. Representative samples were taken from three traverses: the NW suite is the most pristine. Apatite is found primarily as a post-cumulus (or intergranular) phase, but becomes a cumulus mineral in the quartz gabbro. The apatite is F-rich; Cl and OH contents decrease from the base of the complex upward. Apatite in the OF has higher inferred levels of OH. In the SIC, Cl and OH decreased relative to F upon vapour saturation of the evolving melt. The concentrations of LREE, up to 2 wt% La$ rm sb2O sb3+Ce sb2O sb3+Nd sb2O sb3,$ are higher in apatite near the base of the complex. The chondrite-normalized REE patterns, and $ sp{87}$Sr/$ sp{86}$Sr ratios (0.707-0.708), are similar in apatite from each rock type of the Main Mass. The SIC evolved normally by fractional crystallization of a single batch of basic magma, which likely resulted from an impact-generated crustal melt. Apatite from the SW section and, to a lesser extent, the NE section, has significantly lower levels of Cl and LREE; the $ sp{87}$Sr/$ sp{86}$Sr ratio has also been reset (up to 0.739). Local recrystallization during metamorphism thus led to remobilization of these elements from apatite.

Geometric models of the pyroxenes have been developed that allow the calculation of pyroxene crystal chemical properties as a function of pressure, temperature, and composition. The set of all closest-packed stacking sequence labels of length N using the standard A, B, and C notation is partitioned into equivalence classes using the generalized symmetry group, Q ≅ D(N) x S₃. Representatives of each equivalence class are used to derive crystal structure data sets for all of the possible ideal pyroxenes based on stacking sequences of length 12 or less. Stacking sequences of observed pyroxenes are identified, crystallographic settings of the pyroxenes and transformations between them are systematically derived, and the M2-T interatomic distance is identified as an important crystal chemical parameter. The constraint of closest-packing is removed and models of the commonly observed polytypes are derived that have regular M1 and T. These models are parameterized in terms of the O3-O3-O3 angle and the model oxygen radius. M2 is allowed to distort. Crystallographic parameters such as interatomic distances, unit cell volume, and packing distortion are determined as a function of the O3-O3-O3 angle. Results are compared with observed pyroxenes, providing insight into which interatomic interactions are important in determining pyroxene topology and behavior. Temperature is shown to favor polyhedral regularity in orthopyroxene and protopyroxene. Compression and expansion strain ellipsoids for observed and model pyroxenes are compared, demonstrating that a combination of tetrahedral rotation and isotropic compression approximately reproduces the compression ellipsoids of pyroxenes, but not the expansion ellipsoids. Ambient cell volumes of the C2/c pyroxenes are strongly correlated with M1 cation radius. Integrating the relationship between volume and M1 radius with the model provides a means to model volume changes with P, T, and x in the C2/ c pyroxenes.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os métodos geofísicos elétricos, principalmente a eletrorresistividade e polarização induzida (IP), são de grande relevância nos estudos das Geociências, principalmente em investigações de áreas com potencial mineral. Este trabalho visa integrar dados geofísicos, geológicos e furos de sondagens, para o estudo de uma ocorrência mineral de sulfeto de cobre disseminado, localizada no extremo norte da bacia sedimentar do Camaquã (RS). Esta bacia é composta por um conjunto de rochas sedimentares, vulcânicas e vulcanoclásticas, com deformações e falhamentos pós-deposicionais, na qual são descritas diversas ocorrências minerais, principalmente, Cu, Zn , Au, Ag e Pb. Estudos geoquímicos prévios resultaram na descoberta da ocorrência mineral Colônia do Santa Bárbara, pelo Departamento Nacional de Produção Mineral (DNPM) em 1965. Perfurações testemunhadas em conjunto com geoquímica de solos realizadas nesta época apresentaram resultados insatisfatórios. Estudos metalogenéticos recentes no âmbito da bacia sedimentar do Camaquã sugerem a possibilidade de jazimentos do tipo sulfetos disseminados, em contraste ao modelo filoniano historicamente aceito. Dados geofísicos adquiridos, integrados aos dados geoquímicos prévios, complementados por descrições litotógicas e levantamentos estruturais, são utilizados neste trabalho na tentativa de reavaliar as potencialidades econômicas da ocorrência, além da necessidade do estudo de modelos metalogenéticos para direcionamento de pesquisas minerais
Electrical geophysical methods, especially the Electrical Resistivity and Induced Polarization (IP) are of great importance in the geosciences studies, especially in investigations of areas with mineral potential. In this work, we intend to integrate geophysical, geological, geochemical and boreholes, for the study an occurrence of disseminated copper sulphide, located in the northernmost of the sedimentary basin of Camaquã (RS). This basin consists in a set of sedimentary rocks, volcanic and vulcanoclastic with deformation and post-depositional faulting, in which are described several mineral occurrences, mainly Cu, Zn and Au. Previous geochemical studies resulted in the discovery of mineral occurrence by the Departamento Nacional de Pesquisa Mineral (DNPM) in 1965. Witnessed drillings carried this season showed unsatisfactory results in the decision of the finalization of the research. Recent metallogenic studies within the Camaquã sedimentary basin of suggest the possibility of disseminated sulphides types, deposits in contrast to the historically accepted filonian model. Newly acquired geophysical data will be integrated to the previous geochemical data, supplemented by lithological descriptions and structural surveys in an attempt to reassess the economic potential of the event, besides the need for metalogenic models targeting mineral research

Orientador: Walter Malagutti Filho
Banca: José Domingos Faraco Gallas
Banca: Cesar Augusto Moreira
Resumo: Os métodos geofísicos elétricos, principalmente a eletrorresistividade e polarização induzida (IP), são de grande relevância nos estudos das Geociências, principalmente em investigações de áreas com potencial mineral. Este trabalho visa integrar dados geofísicos, geológicos e furos de sondagens, para o estudo de uma ocorrência mineral de sulfeto de cobre disseminado, localizada no extremo norte da bacia sedimentar do Camaquã (RS). Esta bacia é composta por um conjunto de rochas sedimentares, vulcânicas e vulcanoclásticas, com deformações e falhamentos pós-deposicionais, na qual são descritas diversas ocorrências minerais, principalmente, Cu, Zn , Au, Ag e Pb. Estudos geoquímicos prévios resultaram na descoberta da ocorrência mineral Colônia do Santa Bárbara, pelo Departamento Nacional de Produção Mineral (DNPM) em 1965. Perfurações testemunhadas em conjunto com geoquímica de solos realizadas nesta época apresentaram resultados insatisfatórios. Estudos metalogenéticos recentes no âmbito da bacia sedimentar do Camaquã sugerem a possibilidade de jazimentos do tipo sulfetos disseminados, em contraste ao modelo filoniano historicamente aceito. Dados geofísicos adquiridos, integrados aos dados geoquímicos prévios, complementados por descrições litotógicas e levantamentos estruturais, são utilizados neste trabalho na tentativa de reavaliar as potencialidades econômicas da ocorrência, além da necessidade do estudo de modelos metalogenéticos para direcionamento de pesquisas minerais
Abstract: Electrical geophysical methods, especially the Electrical Resistivity and Induced Polarization (IP) are of great importance in the geosciences studies, especially in investigations of areas with mineral potential. In this work, we intend to integrate geophysical, geological, geochemical and boreholes, for the study an occurrence of disseminated copper sulphide, located in the northernmost of the sedimentary basin of Camaquã (RS). This basin consists in a set of sedimentary rocks, volcanic and vulcanoclastic with deformation and post-depositional faulting, in which are described several mineral occurrences, mainly Cu, Zn and Au. Previous geochemical studies resulted in the discovery of mineral occurrence by the Departamento Nacional de Pesquisa Mineral (DNPM) in 1965. Witnessed drillings carried this season showed unsatisfactory results in the decision of the finalization of the research. Recent metallogenic studies within the Camaquã sedimentary basin of suggest the possibility of disseminated sulphides types, deposits in contrast to the historically accepted filonian model. Newly acquired geophysical data will be integrated to the previous geochemical data, supplemented by lithological descriptions and structural surveys in an attempt to reassess the economic potential of the event, besides the need for metalogenic models targeting mineral research
Mestre

Orientador: César Augusto Moreira
Banca: Vinicius de Abreu Oliveira
Banca: George Luiz Luvizotto
Resumo: Na região de Itapira (SP) são conhecidas diversas ocorrências de manganês supergênico, dispostas em uma faixa que se estende desde Itapira-Socorro (SP) até Natércia-Careaçu (MG). Localmente o minério ocorre na forma de lentes, embutidas nos litotipos do Grupo Itapira (quartzitos e quartzo xistos), cujas rochas apresentam padrão estrutural complexo representado por dobras fechadas, redobradas e cisalhadas, com ângulos de mergulho médios a altos em suas porções axiais. Em campo o depósito é caracterizado por superfícies lateríticas, de coloração cinza escura a preta, constituídas predominantemente por óxidos e hidróxidos de manganês resultantes da alteração de gonditos. Análises de difração de raios-X, realizadas em depósitos vizinhos, confirmam a presença de grafita no minério e protominério de Itapira em teores de até 5%. Muitos veios e bolsões de quartzo ocorrem na área, associados com o minério e com as rochas encaixantes. Neste trabalho são apresentados os resultados da caracterização morfológica de uma ocorrência de manganês supergênico por meio de investigação geofísica. Foram utilizados os métodos da Eletrorresistividade e Polarização Induzida e os dados coletados por meio da técnica do Imageamento Elétrico em um arranjoWenner-Schlumberger. Um total de 10 linhas de 420 m cada foram realizadas, com espaçamento entre eletrodos de 10 m, paralelas e espaçadas 50 mentre si. Os dados foram processados com o software Res2Dinv e modelos de inversão 2D foram gerados para os parâmetros resistividade e cargabilidade. Em seguida os modelos 2D foram exportados e interpolados na plataforma Oasis Montaj Geosoft para a geração de modelos de visualização 3D. Os resultados revelaram uma relação do minério de manganês com zonas de baixa resistividade e alta cargabilidade. As altas cargabilidades ocorrem devido aos óxidos de manganês e ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Some manganese supergenic occurences are found next to the Itapira city (SP, Brazil), representative of a trend that extends from Itapira/Socorro (SP) to Natércia/ Careaçu (MG), hosted by quartzites, schists and gneisses of the Itapira Group (Neoproterozoic). Several tectono-metamorphic events (from Paleoproterozoic to Neoproterozoic)affected the area regionally, resulting in a complex structural pattern represented by isoclinal folds, sometimes refolded and sheared. The ore/protore occurs as small bodies of manganese oxides and hydroxides, derived from the supergene alteration of gondite rocks. It is lenticular, rounded to elliptical in shape, with average dimensios of 100 m x 150 m, and dark gray to black in color. It is also locally associated with veins and lumps of quartz. Some of the occurences (Córrego do Cocho, Morro das Palmeiras e Soares) have been studied by others in terms of their mineralogy, petrography, geochemistry and ore processing aspects and X-Ray diffraction measurements showed significant amounts of graphite in the ore, up to 5%. This study aims the morphological characterization of the São Roque occurrence by integrating geological and geophysical investigations (DC-Resistivity and Induced Polarization. The geophysical data were obtained using a multi-electrode cable and the Electrical Resistivity Tomography (ERT) technique, using aWenner-Schlumberger array. Data were modelled through Res2dinv (2D geophysical inversion software for resistivity and IP data) software, where topographical data were included to generate 2D models in terms of resistivity and chargeability. The results showed that the manganese ore is related to low resistivity areas associated with high chargeability areas. Low resistivity results are correlated with highly saturated quartzites (host rocks) in depths below 30-35 meters, while high chargeability values are correlated ... (Complete abstract click electronic access below)
Mestre

En el Sáhara Occidental hay dos unidades principales: la cobertera sedimentaria del Fanerozoico y un basamento cristalino que forma parte del cratón del África Occidental, constituido desde el Paleoarcaico al Paleoproterozoico. A su vez, en el basamento se ha definido una serie de dominios o terranes, delimitados por fallas regionales, que responden a microcontinentes que colisionaron principalmente durante la orogenia Birimiense y la Hercínica. Los primeros estadios de granitización parecen producirse entre el Paleoproterozoico y el Mesoproterozoico dependiendo del dominio, pero el primer gran episodio de plutonismo de tipo TTG generalizado es en la orogenia Leoniana (hacia 3 Ga). Se forman importantes depósitos de BIF en cuencas de “greenstone belts”. El ciclo Liberiense comienza con diques y “sills” ultrabásicos asociados a una pluma mantélica, que evoluciona a una LIP constituida por enjambres de diques de diabasa; en el resto de sectores se produce la individualización de los microcontinentes. El final del ciclo implica la colisión parcial de algunos de estos dominios y procesos de subducción que generan magmatismo calcoalcalino. El proceso de rift en el límite Arcaico- Proterozoico produce magmatismo alcalino saturado y subsaturado, con indicios de elementos raros. Localmente se individualizan cuencas sedimentarias submarinas en las que se forman depósitos importantes de BIF. Durante el Paleoproterozoico se produce la convergencia de la mayoría de las microplacas; en las zonas de suprasubducción se produce un magmatismo calcoalcalino; con el cierre de los océanos y la colisión continental se forman complejos ofiolíticos, a veces con mineralizaciones de Cr-PGE y depósitos de oro orogénico. Esta orogenia produce la cratonización de la mayor parte de los dominios. Los granitos alcalinos asociados al rift posterior son en cambio estériles. El magmatismo calcoalcalino asociado a la orogenia Kibariense en el margen occidental del crató n no par ece haber gener ado depósitos, pero los granitos alcalinos que cierran el ciclo contienen concentraciones muy altas de REE y Nb. La orogenia Panafricana determina la aparición de magmatismo calcoalcalino en el borde occidental del cratón, así como una nueva colisión con el dominio oriental de los Mauritánides, que se cratoniza. El proceso de rifting subsecuente genera rocas alcalinas saturadas y subsaturadas estériles. Los márgenes continentales así formados facilitan la sedimentación de series de plataforma del Paleozoico, en los que se encuentran mineralizaciones de Fe oolítico en el Devónico inferior. Durante la orogenia hercínica se produce la colisión continental de todos estos dominios y Laurussia, formándose el supercontinente de Pangea. En este contexto los cabalgamientos asociados pueden formar mineralizaciones de oro orogénico, y pueden darse mineralizaciones de Cr podiforme (PGE) en ofiolitas. Finalmente, la apertura del Atlántico N desde el Triásico superior-Jurásico produce el desarrollo de carbonatitas en el dominio más occidental de los Mauritánides, asimismo con mineralización de elementos raros. Los márgenes continentales así formados permiten el desarrollo de series de plataforma ricas en yacimientos de fosfatos y con potencial para petróleo. En el curso de este t rabajo se han descubierto varios depósitos minerales, pr incipalmente en el basamento del Precámbrico. Los depósitos de menas metálicas más interesantes son los siguientes: a) Los depósitos ortomagmáticos de Cr- PGE -Ti-V en el complejo estratiforme de Bir Malhat, con continuidades de decenas de km b) Los depósitos de Cr-PGE en cromititas podiformes en contextos oceánicos del Proterozoico de los Mauritánides. c) Los depósitos de Au-(PGE) orogénico asociados a zonas de cizalla, tanto en forma de listwänitas-birbiritas, sistemas filonianos o mineralizaciones estratoligadas asociadas a los mismos, correspondiendo a cizallas formadas en épocas panafricanas (dominios de Tifariti-Bir Lehlu-Ain ben Tili y de Sfariat) o hercínicas (Mauritánides). d) Los depósitos de BIF en series submarinas; si bien estos depósitos se encuentran en todos los dominios, los más interesantes por su continuidad y leyes se encuentran en las zonas de Sfariat y Miyec-Ijil. e) depósitos de Nb-Ta-LREE-U-Fe-V- P-Mo en carbonatitas, importantes tanto en las de edades del Proterozoico como en las del Cretácico. f) depósitos de Nb-Ta-F-HREE-U-Th en rocas alcalinas saturadas o subsaturadas, preferentmente en las enriquecidas en F. g) depósitos de Fe oolítico en las series de plataforma del Devónico inferior, de grandes reservas. h) depósitos de fosforitas y petróleo asociados a la cuenca sedimentaria de El Aaiún. i) Depósitos de U-(REE??) de edad Cuaternario , asociados a calcretas y ferricretas.
Two main geological units are distinguished in Western Sahara: a Phanerozoic sedimentary cover and a cryst a lline basement o f Paleoarchean to Paleoproterozoic age. This basement is a part of the Reguibat ridge, in the Western Africa craton. An ensemble of domains (or terranes) are distinguished in the basement. These domains are limited by regional fauls and correspond to old microcontinents collisioned mainly during the Birimian and Hercynian orogenies. Earlier granitization stages were produced in the Paleoarchean and the Mesoarchean depending on the domain, but the first generalized episode of TTG plutonism occurs in the Leonian orogeny ( circa 3 Ga). Important BIF deposits formed in greenstone belt basins. The Liberian cycle start with the intrusion of ultrabasic sills and dykes, associated with a mantle plume. This scenario evolved to a LIP made up by a dense network of diabase dykes; the individualization of the microcontinents took place in the rest of the area. Convergence of some of these microplates pr oduced subduction and a calc-alkaline magnatism and finally a collision between some of these domains at the end of this cycle. Rifting at the limit Archean-Proterozoic generated saturated and subsaturated alkaline magmatism. Showings of rare- element mineralization occur in these rocks. Submarine sedimentary basins are locally developed, and contain important BIF deposits. Most of the microplates converged during the Paleoproterozoic; calc-alkaline magmatism do occur in the suprasubduction zones; closing of the oceans and subsequent continental collision is associated with development of Cr- (PGE) bearing ophiolitic suites. Regional shear zones are associated with orogeenic gold deposits. This Birimain orogen produced the cratonization of most of the domains.. Alkaline granites intruded in a rft stage at the end of the orogeny, but they are barren. Calc-alkaline magmatism is also present during the Kibarian and Panafrican orogeny at the west border of the WAC, and is not mineralized; however, the alkaline granites of the rifting closing the Kibaran orogeny contain high concentrations of Nb and REE; those at the end of the end of the Panafrican are devoid of mineralization.. The continental margins of the craton allowed the sedimentation of thick platform series during the Paleozoic. The lower Devonian series hosts oolitic iron deposits. The general collision of all these domains and Laurussia during the Hercynian orogeny produced the Pangea supercontinent. In this context, the thrusts can carry orogenic gold deposits, and podiform Cr-(PGE) deposits outcrop in ophiolites. Finally, the opening of the North Atlantic since the Upper Triassic-Jurassic produced carbonatites at the western end of the WAC ; these carbonatites are enriched in rare elements. The continental margins formed in this epoch allowed the sedimentation of platform series thaht contain phospate deposits and have potential to contain oil. Western Sahara has a large potential for ore deposits, and some of them have been discovered during the development of this memory; most of them are hosted in the Precambrian materials: a) Stratiform Cr-PGE -Ti-V deposits associated with the Bir Malhat complex, and their continuity overpass 20 km. b) Podiform Cr-PGE chromitite deposits were produced in the Proterozoic of the Mauritanids. c) Orogenic gold deposits (Au-(PGE) are associated with the regional shear zones. There are several styles of mineralization: listwänites- birbirites, vein systems, or stratabound mineralizations replacing favourable host rocks in the vicinity of shear zones formed during the Birimian orogeny (Tifariti-Bir Lehlu-Ain ben Tili and Sfariat domains) o the Hercynian (Mauritanids). d) BIF deposits in submarine series. These deposits occur in most of the domains, but the Sfariat and Miyec-Ijil domains contain most of the largest reserves. e) Deposits of rare elements as Nb-Ta- LREE-U-Fe-V-P-Mo occur in the Proterozoic and Cretaceous carbonatites. f) Deposits of Nb-Ta-F-HREE-U-Th are found in undersaturated or saturated alkaline rocks, mainly in those enriched in F. g) Oolitic iron deposits have large reserves in the platform series of the Lower Devonian. h) World-class stratiform phosphorite deposits occur in the Paleogene El Aaiún sedimentary basin, which has also potential for oil deposits. i) Calcrete and ferricrete U-(REE??) deposits of Quaternary age.

The most important Greek perlite deposits crop out on the islands of Milos (Provatas and Trachilas areas), Kimolos, and Kos, Aegean Sea, which are currently under exploitation. More than 200 specimens of raw perlite were collected from these perlite deposits and were subjected to physical, chemical, petrographic and expansion tests. The perlite deposits have been formed by a phreatomagmatic eruption, which is the last event of volcanic activity on the islands. Most of the deposits comprise the sand, ash, and perlitic fragments' formation, the perlitic lahar, the perlite beds, and the perlitic dome. The first formation is the precursor of the eruption, and is followed by the perlitic lahar, which is result of lava fragmentation, and the perlite beds, which are slow-cooled lavas. The perlitic dome penetrates into the perlitic succession. Vesiculation has taken place in the perlite beds, producing the pumiceous textures of perlite. Dacite fragments are found in the perlitic lahar, as well. Perlite consists of more than 70% of high silica and alkalies glass. Phenocrysts of quartz, feldspar (mainly plagioclase of oligoclase composition), biotite, opaque minerals (magnetite, ilmenite) and apatite are also present. Various types of perlite, rich in quartz, feldspar, tridimite, and cristobalite, were identified. Two main modes of water are found in perlite. Differences in chemical composition of perlites indicate four individual parent magma sources. The main chemical variation is present in alkalis and Ba, Sr, Rb, and the R.E.E. The Eu anomaly is a common characteristic for the studied perlites. The relationship between glass and perlite composition is given. The specific gravity of Greek perlites ranges between 1.50 and 3.00 gr/cm3, the p.H. between 6.5 and 8.5, the surface area is around 3.00 m2/gr. All the studied perlites indicate good expansibility, obtaining low loose bulk density values (20-240 kgr/m3), low percent of nonexpansibles (1-7%), large particle size, low compaction resistance, high water (15-35%) and oil (400-2200cc/100gr) absorption, and surface area values (6-13 m2/gr). The expanded perlite is chemical inert. A new phase rich in Cr and Fe, a pyroxene, and cristobalite are determined in the expanded product. Four different stages in the expansion process are determined by the scanning electron microscope. The phenocryst proportion and grain size contribute to the expansion results. On the other hand, the chemical and the mineral composition does not affect the expansibility of perlite, perhaps because the range of composition is small. The studied perlite is of good quality and is therefore suitable for filter aid, concrete and plaster aggregate, loose fill insulation, cryogenic, horticulture, animal feed, fire protection, and thermal insulation purposes.

Ni laterites are considered worthy targets for critical metals (CM) exploration as rare earth elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this investigation geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s) (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits. Two Ni laterite profiles from the Falcondo mining area have been compared for their platinum group element (PGE) geochemistry and mineralogy. One profile (Loma Peguera) is characterized by PGE-enriched (up to 3.5 ppm total PGE) chromitite bodies incorporated within the saprolite, whereas the second profile is chromitite-free (Loma Caribe). Total PGE contents of both profiles slightly increase from parent rocks (36 and 30 ppb, respectively) to saprolite (-50 ppb) and reach highest levels within the limonite zone (640 and 264 ppb, respectively). Chondrite-normalized PGE patterns of saprolite and limonite reveal rather flat shapes with positive peaks of Ru and Pd. Three types of platinum group minerals (PGM) were found by using an innovative hydroseparation technique: (i) primary PGM inclusions in fresh Cr-spinel (laurite and bowieite), (ii) secondary PGM (e.g., Ru-Fe-Os-Ir compounds) from weathering of preexisting PGM (e.g., serpentinization and/or laterization), and (iii) PGM precipitated after PGE mobilization within the laterite (neoformation). Results provide evidence that (i) PGM occurrence and PGE enrichment in the laterite profiles is independent of chromitite incorporation; (ii) PGE enrichment is residual on the profile scale; and (iii) PGE are mobile on a local scale leading to in situ growth of PGM within limonite, probably by bioreduction and/or electrochemical metal accretion. Free grains of PGM with delicate morphologies were discovered in limonite hosted chromitite samples (“floating chromitites”) from highest levels in the Falcondo Ni laterite deposit (Dominican Republic). Textural and chemical evidence obtained via SEM and EMP analysis points to a multistage formation: (i) primary PGM formation at magmatic stage; (ii) transformation to highly porous secondary Os-Ru PGM during serpentinization; (iii) neoformation of Ir-Fe-Ni-(Pt) mineral phases during early stages of lateritization; (iv) neoformation of Pt-(Ir) mineral phases within the critical zone of the profile resulting in nugget shaped accumulation of rounded particulates during late stages of lateritization. The observation of accumulations of most likely biogenic mediated in situ growth of Pt rich nanoparticles in supergene environments could help to explain (i) why Pt bearing nuggets are the most abundant PGM found in surface environments, (ii) why Pt nuggets from placer deposits generally surpass the grain sizes of Pt grains found in parent rocks by several orders of magnitude (few micrometers vs. several millimeters) and (iii) how anthropogenic PGE contamination may affect our biosphere. Osmium chromitite, saprolite and limonite (Falcondo mining area), suggest that serpentinization of the Loma Caribe peridotite has not significantly affected the Re-Os system in Os-rich PGM. This is noted by the fact, that primary PGM formed at magmatic stage and secondary Ru-Os-Mg- isotope characteristics from primary and secondary PGM, separated from Si PGM formed due desulphurization of primary PGM with significant incorporation of Mg silicates, have almost identical Os isotope characteristics, typical of the mantle. However, the Re-Os system can be significantly disturbed during stages of lateritization when porous secondary PGM react with Fe-rich fluids, thus forming hexaferrum and magnetite in the 187 188 interstices of secondary PGM. Here presented data indicate that more radiogenic ratios in higher levels of the weathering profile are linked to steady mobilization of PGE within secondary PGM resulting in subsequent loss of Os counterbalanced by the incorporation of Fe. Os/ Os In this investigation presented data clearly states that PGE are neither noble nor inert in surface environments, at least in those related to tropical Ni laterites from the Northern Caribbean.

En Angola afloran complejos carbonatíticos en todos los niveles de emplazamiento tanto plutónico, hipoabisal como volcánico. Recientemente, se han caracterizado en detalle algunos de estos complejos debido a las mineralizaciones en HFSE y REE que presentan así como su comportamiento en función del nivel de emplazamiento. Sin embargo, aún no se conoce con precisión la distribución de elementos raros en ambientes subvolcánicos explosivos. Los complejos de Monte Verde y Bonga muestran mineralizaciones en las manifestaciones explosivas de modo que su estudio ha permitido describir y comprender la distribución de elementos raros en tales condiciones. De forma paralela, los resultados obtenidos en esta tesis han permitido entender la relación entre carbonatitas y lamprófidos ultramáficos en el complejo de Bonga, asociación que hasta ahora ha sido descrita en escasos complejos. El complejo de Bonga presenta cuerpos intrusivos mixtos de composición carbonatítica – lamprofíricos. Éstos fueron formados en estadios de cristalización tardíos por fenómenos de magma mingling como resultado de una intrusión de magma aillikítico y alnöítico dentro de una cámara magmática con magma carbonatítico residente. Esta mezcla de magmas dio lugar a estadios explosivos que no concentran especialmente elementos raros como HFSE y REE. De forma similar, las brechas subvolcánicas estudiadas en el complejo de Monte Verde contienen cantidades secundarias de estos elementos. En ambos complejos se concentran en cantidades traza de pirocloro empobrecido en F. El estudio de la distribución de elementos raros y la evolución de la carbonatita de Bonga se ha realizado mediante la caracterización de la geoquímica del pirocloro. Se ha determinado pirocloro primario de Na y F en los diques anulares alrededor de la intrusión que indica una composición rica en álcalis en el magma carbonatítico. El contenido en Na y F disminuye debido a la progresión de la fenitización. Los estadios posteriores más tardíos que dan lugar a rocas de magnetita-apatito, al cuerpo calciocarbonatítico central y a la matriz carbonatítica, presentan pirocloro pobre en F con una proporción de Na inferior. Los mayores enriquecimientos de elementos raros HFSE y REE se registran en los pirocloros secundarios formados en procesos hidrotermales muy tardíos y que están asociados a la invasión de la carbonatita por fluidos procedentes de las rocas encajantes. En estos estadios es donde se concentran carbonatos y fosfatos de REE. En consecuencia, el potencial metalogenético de las rocas de Bonga en ambientes explosivos no es destacable. Sin embargo, los elementos raros se suelen concentrar en estadios anteriores, en la formación de los diques anulares y rocas de magnetita – apatito. El potencial en elementos raros en las brechas carbonatíticas subvolcánicas de Monte Verde es muy bajo. Tampoco las rocas plutónicas alcalinas asociadas contienen cantidades de elementos raros importantes, como indica la escasez en carbonatos, fosfatos de REE así como en silicatos y óxidos agpaíticos (loparita, eudialita y sorosilicatos de Na-Ti-Zr). Éstos además presentan intervalos de agpaicidad bajos.

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Foram estudados corpos graníticos localizados no setor Monsenhor Bastos, porção sudoeste da Província Uranífera de Lagoa Real (PULR). A amostragem foi desenvolvida nas pedreiras de Lagoa Linda (LL), Pedreira Nova (PN) e no granitoide Lajedo (GR) este ultimo que aflora imediatamente a leste da anomalia uranífera AN02. O trabalho focaliza aspectos mineralógicos, geoquímicos, tipológicos e de fluidos desses granitoides, a fim de classificá-los mineralogica, textural e quimicamente. Foram utilizadas as metodologias de petrografia, microssonda eletrônica, geoquímica, termobarometria e estudo de inclusões fluidas (IF). As amostras de granitos apresentam uma paragênese magmática composta por feldspato potássico, plagioclásio, quartzo, piroxênio, ilmenita 1 e zircão. Também foram identificadas duas fases pós-magmáticas compostas por anfibólio, biotita, granada, allanita, ilmenita 2, kainosita, parisita. A ocorrência desses eventos pós-magmáticos propiciou também a formação de uma segunda geração de plagioclásio, zircão, além da formação de mirmequitas e a recristalização de parte dos feldspatos e quartzo. O anfibólio estudado foi formado por alteração do piroxênio em contato com o fluido do primeiro evento pós-magmático. A biotita foi gerada a partir da alteração do anfibólio. No mesmo período de formação do anfibólio foi gerada a allanita, sendo que a parisita e kainosita formaram-se pela alteração desta durante um evento pós-magmático. O evento pós-magmático mais antigo está associado a fluidos ricos em F e Cl, com baixo fO2, pressão próxima a 7 Kbar e temperatura inferior a 700 oC. A parte final desse evento esta associado a soluções alcalinas, ricas em CO2, com temperaturas no intervalo entre 480 C e 600 oC. O estudo de IF permitiu caracterizar fluidos tardios aprisionados no quartzo, que podem estar relacionados com o segundo evento pós-magmático. Esses fluidos, de provável origem hidrotermal, é bastante semelhante ao encontrado por Fuzikawa et al (1988), nas IF dos veios de quartzo que cortam os gnaisses da PULR. A geoquímica permitiu classificar os granitos como sienogranitos / quartzo sienitos, metaluminosos, alcalino-cálcicos (na fronteira dos calci-alcalinos), plotando na série shoshonitica. Também foram classificados como granitos Tipo A, não evoluídos e ferroan. Os dados obtidos não permitem classificar os granitos São Timóteo como rapakivi. Entretanto, a composição desses granitos é equivalente, em termos de elementos maiores e elementos traços, aos granitos rapakivi Cigano e Serra dos Carajás, fases menos especializadas da Suíte Serra dos Carajás. Finalmente, ressalta-se a clara necessidade do desenvolvimento de estudos metalogenéticos, geoquímicos e isotópicos que permitam conhecer com aprofundamento a composição e evolução da Suíte magmática de Lagoa Real e sua relação com as mineralizações de urânio.
Granitic bodies located in the Monsenhor Bastos sector, southwestern portion of the Lagoa Real Uranium Province (PULR) were studied. The sampling was developed in the quarries of Lagoa Linda, Pedreira Nova and Lajedo granitoids that outcrop immediately east of the uranium anomaly (AN02). The work focused on the mineralogical, geochemical, and fluid typological aspects of these granitoids in order to classify them mineralogical, textural and chemically. Petrography, electron microprobe, geochemical, thermobarometry and study of fluid inclusions (FI) methods were performed. The granite shows a magmatic paragenesis with potassium feldspar, plagioclase, quartz, pyroxene, ilmenite and zircon. Two post-magmatic stages composed of amphibole, biotite, garnet, allanite, ilmenite, kainosite, parisite were also identified. The occurrence of post-magmatic events has also led to the formation of a second generation of plagioclase, zircon, besides mirmequites formation and recrystallization of feldspar and quartz. The amphibole was formed by the alteration of pyroxene in contact with the first post-magmatic fluid event. The biotite was generated from the alteration of the amphibole. Allanite was generated in the same period of the amphibole formation, while parisite and kainosite were formed from allanite alteration during a pós-magmatic event.. The post-magmatic oldest event is associated to low fO2, near 7 Kbar pressure, below 700 oC temperature F and Cl rich fluids. The final part of this event is associated to alkaline solutions, rich in CO2, with temperatures between 480 C and 600 oC. The FI studies allowed to characterize late fluids trapped in quartz, which may be related to the second post-magmatic event. This fluid, probably of hydrothermal origin, is quite similar to one found by Fuzikawa et al (1988), in FI found in quartz veins cutting the PULR gneisses. The geochemistry allowed to classify the granites as sienogranites / quartz syenites, metaluminous, alkali-calcic (the border of calc-alkaline) and plotting in shoshonitic field. Granites were also classified as Type A, unevolved and ferroan. The data do not allow the classification of São Timóteo granite as rapakivi type. However, the composition of these granites is equivalent, in terms of major and trace elements, to the Cigano and Serra dos Carajas rapakivi granites, less specialized phases of Serra dos Carajás suite. Finally, it emphasizes the clear need for further metallogenesis, geochemical and isotopic studies depth as to show the composition and evolution of magmatic suite of Lagoa Real and its relationship to uranium mineralization.

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Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências- Geoquímica Ambiental. Niterói, RJ
As várzeas são ecossistemas extremamente ricos, em termos de biodiversidade e de produtividade (Junk, 1997), na Amazônia. Embora muito pouco se conheça sobre a dinâmica sedimentar no interior destes sistemas de várzeas, eles parecem desempenhar um papel importante tanto no que diz respeito ao transporte sedimentar, quanto nos ciclos dos elementos dissolvidos e particulados. Este estudo possibilitará, através de uma caracterização sedimentológica da várzea, a compreensão dos principais processos que determinam a deposição e/ou remobilização dos sedimentos superficiais nestes sistemas. O que de uma maneira mais ampla será extremamente importante para determinarmos a natureza do material sedimentar (orgânico e mineral) e conhecermos a atual dinâmica dos sedimentos, desde sua entrada nos lagos até sua deposição, assim como os processos que regem esta deposição e a provável ressuspensão. A várzea escolhida para este estudo foi a Várzea do Lago Grande do Curuai, situada próxima à cidade de Óbidos, no estado de Pará, a 850 km a montante da desembocadura deste no Oceano Atlântico. Para a realização deste estudo diferentes pontos de coleta de sedimento foram amostrados e os parâmetros a seguir foram analisados: concentração em material em suspensão, granulometria, mineralogia, teor em carbono e nitrogênio orgânico, a razão C/N e a composição isotópica do carbono e nitrogênio (δ13C e δ15N ). Os resultados mostram que com relação à caracterização granulométrica, foi verificado que os lagos próximos ao rio Amazonas apresentam uma granulometria mais fina devido ao material que chega pelas águas do rio Amazonas. Os lagos próximos a terra firma, são caracterizados por maiores teores de areia. Essa areia seria proveniente de igarapés que deságuam nestes lagos e trazem consigo um material mais grosseiro. A várzea de um modo geral apresenta-se como siltosa, variando entre silte médio a fino. Alguns lagos são um pouco arenosos, como é o caso do Lago Curumucuri, isolado do sistema, de águas pretas e com um igarapé desaguando sobre ele. Os Minerais presentes na Várzea são: a caolinita, a esmectita, o quartzo, a sílica amorfa. Apresentando como o argilo-mineral mais presente a esmectita. Os lagos com maiores teores em matéria orgânica são os lagos de águas pretas. A matéria orgânica presente nos sedimentos dos lagos parece ter basicamente duas fontes: o Rio Amazonas e a atividade biológica local (macrófitas, fitoplâncton e perifito). Mas de uma maneira geral a componente fitoplanctônica parece ser muito bem preservada nos sedimentos da várzea
Flood plains are extremely rich ecosystems of Amazonia in terms of biodiversity and high production (Junk, 1997). Furthermore, they play an important role in sedimental transportation as well as for the cycles of dissolved and particular elements. Várzea of Lago Grande de Curuai is located on the southern banks of the Amazon River, 850 km in length until the mouth of the river in the Atlantic Ocean. Through a full sedimentological characterization of the flood plain, this study will enable the understanding of the main processes, that determine the bulk and/or remobilization of the superficial sediments in these systems. This will be extremely important for us to determine the nature of sedimental material (organic and mineral) and to know the present dynamics of the sediments, the organic material and the potential of accumulation of carbon in these systems. For the study of the recent sedimentation in the area, a sedimental collection was made at several spots along Várzea. For the comprehension of these, sedimentological and grainsize studies of the material in suspension and the origin of the organic material, with a total of carbon, nitrogen, its reason and isotopic composition δ13C e δ15N, were made. In relation to the grainsize characterization, it was verified that lakes nearby the Amazon River show smaller grainsize due to the fine material brought by the water of the river. In lakes close to the forests, one can find find higher concentrations of sand. than in others. This sand comes from igarapés, which flows into these lakes, bringing with it thick material like sand. In general the flood plain presents silty, varying from medium to small silt. Some lakes, such as Lago Curumucuri have less sand. Morover, it is isolated from the system, containing black water and an igarapé flowing into it. The present minerals found in the Várzea are: kaolinite, smectite, quartz, and amorphous silic. Presenting as a claymineral, the most present material is esmectita. The organic material present in the sediments of the lakes is the main consequence of the phytoplanktonic activity in situ

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O presente trabalho tem como objetivos caracterizar a mineralogia da fração argila e a suscetibilidade magnética em diferentes superfícies geomórficas, avaliar a correspondência entre difração de raios x e a espectroscopia de reflectância difusa no auxílio das estimativas dos teores de goethita e hematita, avaliar a influência dos óxidos de ferro na adsorção de fósforo bem como a calibração e a validação de funções de pedotransferência para a predição do fósforo adsorvido, utilizando os óxidos de ferro e a suscetibilidade magnética. Uma área de 500 hectares foi delimitada e uma amostra de solo, a cada seis hectares foi coletada na profundidade de 0,0 a 0,20 m. No espigão da área, foi locada uma transeção, e amostras de solos foram coletadas a cada 25 metros. Em cada superfície geomórfica mapeada na área, foram coletadas aproximadamente 20 amostras de solos dispostas nas laterais da transeção. As amostras de solos foram levadas ao laboratório para a realização das análises granulométricas, físicas, mineralógicas, de fósforo adsorvido e da suscetibilidade magnética. Os teores de goethita e hematita foram estimados utilizando a proporção destes óxidos de ferro obtida por difração de raios x e por espectroscopia de reflectância difusa. Os resultados das análises foram submetidos às análises estatísticas e geoestatísticas, e funções de pedotransferência foram calibradas e validadas para a predição do fósforo adsorvido bem como seu mapeamento. Os resultados permitiram concluir que: A natureza dos minerais da fração argila e a suscetibilidade magnética são dependentes da variação do material de origem. A variabilidade espacial da cristalinidade e dos teores dos óxidos de ferro, bem como da suscetibilidade magnética, é dependente da idade das superfícies geomórficas. A superfície mais nova...
This study aims to characterize the clay mineralogy and magnetic susceptibility in different geomorphic surfaces, evaluate the correlation between x-ray diffraction and diffuse reflectance spectroscopy in the estimation of goethite and hematite, the influence of iron oxides on the adsorption phosphorus as well as the calibration and validation of pedotransfer functions for predicting adsorbed phosphorus using iron oxides and magnetic susceptibility. An area of 500 hectares was delineated and a soil sample every six hectares was collected in depth from 0.0 to 0.20 m. A transect was leased, and soil samples were collected every 25 meters. In each geomorphic surface mapped in the area were collected approximately 20 soil samples arranged on either side of the transect. Soil samples were taken to the laboratory for carrying out particle size analysis, physical, mineralogical, adsorbed phosphorus and magnetic susceptibility. The goethite and hematite were estimated using the ratio of iron oxides obtained by x-ray diffraction and by diffuse reflectance spectroscopy. The results of the analysis were subjected to statistical analysis and geostatistical, and pedotransfer functions were calibrated and validated to predict the adsorbed phosphorus and its mapping. The results showed that: The spatial variability of crystallinity and of the content of the iron oxides, as well as the magnetic susceptibility is dependent on the age of the geomorphic surfaces. The surface newest (III) has a higher spatial variability of these attributes. The clay minerals influence the soil physical properties. The characterization of the spatial variability of iron oxides and magnetic susceptibility allows the delineation of homogeneous areas that may be relevant future ace soil series and the specific management areas. The goethite and hematite... (Complete abstract click electronic access below)

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O depósito de Fortaleza de Minas vem sendo estudado a mais de 20 anos desde a sua descoberta em 1983 e apresenta similaridades com outros depósitos komatiíticos arqueanos descritos na literatura. Sua configuração atual reflete ação de processos metamórficos e deformacionais diversos gerando novos tipos de minério sem, no entanto, perder sua identidade primária komatiítica e permitindo reconstruir sua faciologia vulcanológica. Contexto regional A região de Fortaleza de Minas corresponde a um bloco cratônico arqueano retrabalhado na Faixa Móvel Brasília de idade neoproterozóica. Os terrenos granito-greenstone afloram em meio à metasedimentos supracrustais proterozóicos dos grupos Araxá e Canastra que compõe a nappe de Passos. O bloco arqueano corresponde ao limite sul do antigo Craton do Paramirim fazendo contato com o cinturão granulítico de Alfenas a Sul. Estudos geológicos e geofísicos recentes demonstram que esta área corresponde a uma zona de junção entre dois blocos crustais, denominados Brasília e São Paulo, que representam duas paleo-placas separadas pela zona de sutura de Alterosa. No bloco Brasília ocorrem os greenstone belts de Morro do Ferro e Pihum-i. As idades obtidas para estes greenstone belts estão distribuídas entre 2,8 e 2,9 Ga e 2,9 e 3,1 Ga respectivamente e são discutidas no capítulo 3. O greenstone belt do Morro do Ferro ocorre como faixas descontínuas e estreitas estruturadas em quilhas sinclinais representando as raízes desta seqüência greenstone. Estão fortemente deformadas e cortadas pelo sistema sinistral de falhas transcorrentes Campo do Meio responsável pela estruturação sigmoidal da região (capítulo 2) (Fig. 1, pg. 33 e Fig. 1, pg.4). O Greenstone Belt Morro do Ferro é representado por derrames komatiíticos e mais restritamente toleíticos com intercalações subordinadas de sedimentos químicos exalativos...
After 20 years of exploration and mining in the Fortaleza de Minas nickel deposit (formerly known as O`Toole) a better understanding of the geological framework and the volcanic environment was achieved. The different ore types observed in the deposit and its distribution revealed the original volcanic setting for the ore formation and also the geological evolution and transformation of the different ore types. The nickel mineralization is classified as a Type 1 deposit (Lesher and Keays, 2002). It is associated to an open trough structure of lava pathway. Later metamorphism and deformation obliterated most of the original volcanic textures and promoted a strong stretching of the ore zone and remobilization of the massive breccia ore along a major shear zone installed at the base of an upper fractionated host flow unit in contact with a footwall BIF. In the Neoproterozoic Brasiliano Cycle (0.6 Ga) a new ore type was formed of hydrothermal origin with extremely high nickel grades and PGE nuggests...(Complete abstract, click electronic address below)

Orientador: José Marques Júnior
Coorientador: Gener Tadeu Pereira
Banca: Dilermano Perecin
Banca: Newton La Scala Júnior
Banca: Pablo Vidal Torrado
Banca: Alberto Vasconcelos Inda Júnior
Resumo: O presente trabalho tem como objetivos caracterizar a mineralogia da fração argila e a suscetibilidade magnética em diferentes superfícies geomórficas, avaliar a correspondência entre difração de raios x e a espectroscopia de reflectância difusa no auxílio das estimativas dos teores de goethita e hematita, avaliar a influência dos óxidos de ferro na adsorção de fósforo bem como a calibração e a validação de funções de pedotransferência para a predição do fósforo adsorvido, utilizando os óxidos de ferro e a suscetibilidade magnética. Uma área de 500 hectares foi delimitada e uma amostra de solo, a cada seis hectares foi coletada na profundidade de 0,0 a 0,20 m. No espigão da área, foi locada uma transeção, e amostras de solos foram coletadas a cada 25 metros. Em cada superfície geomórfica mapeada na área, foram coletadas aproximadamente 20 amostras de solos dispostas nas laterais da transeção. As amostras de solos foram levadas ao laboratório para a realização das análises granulométricas, físicas, mineralógicas, de fósforo adsorvido e da suscetibilidade magnética. Os teores de goethita e hematita foram estimados utilizando a proporção destes óxidos de ferro obtida por difração de raios x e por espectroscopia de reflectância difusa. Os resultados das análises foram submetidos às análises estatísticas e geoestatísticas, e funções de pedotransferência foram calibradas e validadas para a predição do fósforo adsorvido bem como seu mapeamento. Os resultados permitiram concluir que: A natureza dos minerais da fração argila e a suscetibilidade magnética são dependentes da variação do material de origem. A variabilidade espacial da cristalinidade e dos teores dos óxidos de ferro, bem como da suscetibilidade magnética, é dependente da idade das superfícies geomórficas. A superfície mais nova... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This study aims to characterize the clay mineralogy and magnetic susceptibility in different geomorphic surfaces, evaluate the correlation between x-ray diffraction and diffuse reflectance spectroscopy in the estimation of goethite and hematite, the influence of iron oxides on the adsorption phosphorus as well as the calibration and validation of pedotransfer functions for predicting adsorbed phosphorus using iron oxides and magnetic susceptibility. An area of 500 hectares was delineated and a soil sample every six hectares was collected in depth from 0.0 to 0.20 m. A transect was leased, and soil samples were collected every 25 meters. In each geomorphic surface mapped in the area were collected approximately 20 soil samples arranged on either side of the transect. Soil samples were taken to the laboratory for carrying out particle size analysis, physical, mineralogical, adsorbed phosphorus and magnetic susceptibility. The goethite and hematite were estimated using the ratio of iron oxides obtained by x-ray diffraction and by diffuse reflectance spectroscopy. The results of the analysis were subjected to statistical analysis and geostatistical, and pedotransfer functions were calibrated and validated to predict the adsorbed phosphorus and its mapping. The results showed that: The spatial variability of crystallinity and of the content of the iron oxides, as well as the magnetic susceptibility is dependent on the age of the geomorphic surfaces. The surface newest (III) has a higher spatial variability of these attributes. The clay minerals influence the soil physical properties. The characterization of the spatial variability of iron oxides and magnetic susceptibility allows the delineation of homogeneous areas that may be relevant future ace soil series and the specific management areas. The goethite and hematite... (Complete abstract click electronic access below)
Doutor

Orientador: Guillermo Rafael Beltran Navarro
Resumo: Conhecido por ser um dos polos cerâmicos de maior destaque da América Latina, o Polo Cerâmico de Santa Gertrudes (PCSG), tem o diferencial de seus produtos associado aos argilitos e siltito provenientes da Formação Corumbataí (Neopermiano da Bacia do Paraná) aflorantes por toda a região dos municípios de Cordeirópolis, Ipeúna, Limeira, Piracicaba, Rio Claro e Santa Gertrudes (SP). Devido à sua importância no mercado nacional e internacional, o PCSG tem sido objeto constante de estudos que visam aprimorar sua produção e buscar novas fontes de matérias-primas. O presente trabalho busca caracterizar os litotipos da Formação Tatuí (Neopermiano) quanto à sua composição química, mineralogia e aspectos tecnológicos, com o intuito de verificar se esses materiais podem ser aplicados como fonte alternativa de matéria-prima para o PCSG. Para isso foi realizado o levantamento geológico de duas colunas estratigráficas da Formação Tatuí na região do município de Ipeúna, cujos litotipos foram avaliados por meio de análises químicas, petrográficas e difratométricas, além de ensaios cerâmicos, os quais abrangeram testes de queima a 950º C, 1050º C e 1150º C, testes de carga de ruptura instantânea, resistência a flexura e absorção de água, além de analises de granulometria de moagem por difração de raios - X. As análises mostraram que os litotipos apresentam, de maneira geral, granulometria fina e são constituídos principalmente por quartzo, feldspato potássico, plagioclásio (albita) e filossi... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Known for being one of the most important ceramic centers in Latin America, the Santa Gertrudes Ceramic Pole (PCSG) has the differential of its products associated with the high quality red clays of the Corumbataí Formation (Neopermian) found throughout the city areas of Cordeirópolis, Ipeúna, Limeira, Piracicaba, Rio Claro and Santa Gertrudes (SP). Due to its importance in the national and international market, the PCSG has been the object of constant studies that aim to to improve its production and to look for new sources of raw materials. The present work aims to characterize the Tatuí Formation (Neopermian) lithotypes in their geochemistry, mineralogy and technological aspects, in order to verify if these materials can be used as an alternative source of raw materials for the PCSG. In order to achieve this goal, a geological survey of two stratigraphic profiles of the Tatuí Formation was carried out in the region of Ipeúna, with their lithotypes submitted to chemical, petrographic and diffractometric analyzes, as well as ceramic tests. These tests included burning at 950 º C, 1050 ° C and 1150 ° C, instantaneous burst load, flexural strength, water absorption and particle size analysis by X - ray diffraction. The analysis showed that the lithotypes have, in general, fine granulometry and are constituted mainly by quartz, potassium feldspar, plagioclase (albite) and phyllosilicates, with secondary concentrations of zeolite and iron oxides and hydroxides. These results, co... (Complete abstract click electronic access below)
Mestre

Orientador: Glauco de Souza Rolim
Resumo: Nos solos a goetita e hematita são os principais representantes dos óxidos de ferro, estes minerais necessitam de condições distintas para sua formação, e apresentam influências positivas nas propriedades físicas e químicas do solo. Embora os óxidos de ferro sejam considerados estáveis por longo tempo, estes tem apresentado diferenças no teor em intervalo de tempo menor. Existindo ainda os minerais pedogênicos e litogênicos e sendo a disponibilidade destes minerais fortemente relacionados às condições climáticas. O objetivo deste estudo foi relacionar as concentrações de hematita e goetita com as condições climáticas de 30 anos e gerar concentrações desses óxidos em cenário otimista (RCP 2.6) e pessimista (RCP 8.5) de mudanças climática, preconizados Painel Intergovernamental sobre Mudanças Climáticas (IPCC). O cenário otimista indica aumento médio da Temperatura em 1°C e redução da precipitação média em 7,5 mm no planeta. O cenário pessimista indica aumento da temperatura em 2°C e aumento da precipitação em 37,8 mm. Foi realizada uma metanálise para prospecção dos teores de hematita e goetita em solos de diferentes regiões do mundo e informações climáticas foram coletados na plataforma NASA-POWER. Os dados dos teores dos óxidos de ferro e climáticos foram relacionados de diversas formas. O modelo de aprendizagem de maquina, Random florest regressor (RF) foi usado para estimar as concentrações de Hm e Gt para o mundo, mapas de distribuição desses minerais foram criados consid... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre

The May Lake interpluton screen is a 4 km long, ∼0.5 km wide swath of metamorphic rock cropping out between plutons of the ∼103 Ma Yosemite Valley Intrusive Suite and the ∼93-85 Ma Tuolumne Intrusive Suite in Yosemite National Park, California. Metasomatic alteration and recrystallization due to contact metamorphism and fluid infiltration resulted from the emplacement of the Cretaceous plutons. Mineral assemblages are consistent with metamorphism to hornblende-hornfels and amphibolite facies. The presence of sillimanite-bearing metapelite and more Mg-rich clinopyroxene in calc-silicate assemblages of the northeast section of the screen than the southwest suggest higher grade metamorphism was experienced to the northeast. Pseudosection diagrams created from whole rock chemical analyses of three metapelite rocks also indicate higher temperatures in the northeastern section of the screen with minimum temperatures estimated from ∼540-617°C. Based on petrographic analysis of andalusite- and sillimanite-bearing metapelite, it is likely that the screen experienced two stages of contact metamorphism: relatively lower temperature metamorphism during intrusion of the Yosemite Valley Intrusive Suite followed by relatively higher temperature contact metamorphism during intrusion of the more mafic Tuolumne Intrusive Suite. Stable isotope data suggest that rock permeability and preexisting structures were the strongest factors controlling fluid infiltration through the contact aureole.

The interactions of polysaccharides (dextrin, amylopectin and carboxymethyl cellulose (CMC)) with variously modified quartz samples were investigated using floatability, wettability, electrokinetic and adsorption tests, supplemented by conventional titration and infrared spectroscopic studies. The quartz samples were treated either by methylation (rendered hydrophobic), lead coating (introduction of metallic adsorption centres), or both forms of surface modification. The presence of metal ionic sites on a quartz surface played a decisive role in polysaccharide adsorption. The adsorption densities of both dextrin and CMC on lead-coated quartz were both much higher and much more pH-dependent than those on uncoated quartz. The "hydrophobic bonding" of dextrin with mineral surfaces as reported in the literature was not observed with hydrophobic (methylated) quartz. However, if the quartz contained surface lead ionic sites and was also methylated, it adsorbed more dextrin than unmethylated, lead-coated quartz. This was also true for the adsorption of CMC onto similarly modified quartz samples. To obtain a rational understanding of the importance of metal ions in polysaccharide adsorption, studies of the solution chemistry of polysaccharides and metal ions were conducted. CMC co-precipitated with both metal cations and metal hydroxy complexes, (including metal hydroxides), whereas dextrin co-precipitated only with metal hydroxides. Co-precipitation involving either polysaccharide caused a decrease in the solution pH. Dextrin-metal co-precipitation occurred at pH optima of 7.5, 8, 9, 11, and 12 for ferric, aluminum, cupric, lead and magnesium ions, respectively. Infrared spectroscopic studies of the precipitates revealed the elimination of glucose ring deformation, suggesting a chemical basis for the interaction between dextrin and metal hydroxides. The surfaces of sulphide minerals behaved like hydroxide during dextrin adsorption. Since copper and lead hydroxides form over different pH ranges, the pH ranges for optimum adsorption of dextrin on copper sulphides and lead sulphides were different. The results of preliminary flotation tests indicated that dextrin could be utilized in the differential flotation of Cu-Pb sulphides. Small scale flotation tests conducted on synthetic mixtures of chalcopyrite and galena confirmed this point.
Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate

The mineralogy, petrology and petrogenesis of a representative suite of late Archean syenitic intrusions emplaced along the Porcupine-Destor fault zone near Matheson, Ontario in the southern Abitibi greenstone belt are studied using a combined approach involving field work, petrography, mineral chemistry and, major and trace element geochemistry. Members of the Matheson suite are from east to west: Iris, Garrison, Emens, Ludgate and Pangea intrusions. The Iris, Emens, Ludgate and Pangea intrusions are mostly composed of syenitic rocks with compositions ranging from alkali-feldspar quartz-syenite to melasyenite. Textures range from equigranular to porphyritic. Iris and Pangea intrusions also contain related mafic rocks. The Garrison intrusion is composed of hornblende quartz-monzonite. All intrusions but one have hypersolvus feldspar assemblages; the exception being Garrison intrusion, which displays a subsolvus feldspar assemblage. The occurrence of late aegirine-augite, magnesioriebeckite and widespread albite replacement, especially in rocks from Ludgate and Iris intrusions, indicates that late or post-magmatic sodium-rich fluids variably affected the rocks. Two magmatic series were identified based on silica-saturation properties and alkali-contents. (Abstract shortened by UMI.)