Over the last decade, the interstitial alloying of niobium has proven to be essential for enabling superconducting radiofrequency (SRF) cavities to operate more efficiently at high accelerating gradients. The discovery of "nitrogen doping" was the first readily accessible avenue of interstitial alloying in which researchers saw an increase in cavity performance. However, the serendipitous nature of the discovery led to additional research to fundamentally understand the physics behind the increase in cavity performance. This knowledge gap is bridged by materials characterization. Secondary ion mass spectrometry (SIMS) is a characterization technique which has become a staple of SRF cavity characterization that details elemental concentration profiles as a function of depth into the niobium surface with submicron resolution. SIMS has been widely used by the semiconductor industry for decades but has found less application in other fields due to the difficulty to produce reproducible data for polycrystalline materials. Much effort has been given to reduce the uncertainty of SIMS results to as low as 1% - 2% for single crystals. However, less attention has been given to polycrystalline materials with uncertainty values reported between 40% - 50% The sources of uncertainty were found to be deterministic in nature and therefore could be mitigated to produce reliable results. This dissertation documents the efforts to reduce SIMS method uncertainty which has been further used to solve mysteries regarding the characterization of SRF cavities which include predictive modeling of oxygen diffusion as well as the identification of contaminants resulting from cavity furnace treatments. / Doctor of Philosophy / Particle accelerators find many uses in society in which their complexity depends on their intended purpose. These purposes vary from projecting an image as in cathode ray tube (CRT) TVs, to creating high energy x-rays for life saving cancer treatments, to researching the very fundamental principles of science and physics. The later uses particle accelerators which are very large, spanning multiple miles, and run at extremely high energies. To keep operational costs reasonable, these instruments need to run as efficiently as possible. Therefore, superconducting radiofrequency (SRF) niobium cavities are used and are responsible for propulsion of charged particles. Although, niobium SRF cavities can pass incredibly high currents with very little surface resistance, these high-end particle accelerators push the operational boundaries of efficiency. To improve the efficiency of these cavities, an optimal concentration of impurities, such as oxygen and nitrogen, are added to the niobium surface. The addition of an impurity level that is too high or too low causes the resistance to increase which translates to higher operational costs. Therefore, it is important to accurately determine the concentration of impurities within the niobium and with high depth resolution. Secondary ion mass spectrometry is a characterization method that uses a primary ion beam to impact the surface of a material to remove atoms at the very surface. The ejected atoms are then ionized into a secondary beam which can then be detected to determine the concentration and to identify the species which was removed. Historically, this instrument has yielded results with 40% - 50% uncertainty for polycrystalline metals, such as niobium, which do not sputter evenly. With SRF cavity performance depending on accurate quantitation of impurities, a more robust method is needed. Therefore, this dissertation identifies issues which cause high uncertainties for polycrystalline materials and in addition offers mitigation strategies to reduce uncertainty to below 10%. These methods were then applied to solve real problems aimed to improve the production of niobium SRF cavities.

SIMS est une technique d'analyse sensible de la surface. La probabilité d'ionisation dépend de l'état chimique de la surface. La génération des ions positifs est améliorée par le bombardement de la surface avec des éléments électronégatifs.Sur le NanoSIMS 50 de CAMECA, dont la configuration optique nécessite une polarité opposée entre ions primaires et secondaires, l'analyse des ions positifs se fait sous bombardement d'ions O-, générés dans un duoplasmatron. La faible brillance de la source en mode O- a comme conséquence une faible résolution latérale des analyses. Pour y remédier, nous avons étudié la possibilité de générer d’autres faisceaux d’ions primaires négatifs. Dans cet objectif, nous avons étudié la génération par duoplasmatron d'ions F-, Cl-, Br- et I- en fonction du champ magnétique, du courant d'arc et de la pression totale des gaz. Le courant d'ions et le diamètre du faisceau ont été mesurés afin de déterminer la brillance de la source en mode F-, Cl-, Br- et I-. Une brillance 5 fois plus élevée en mode F- qu'en mode O- a été déterminée.En utilisant les faisceaux F-, Cl-, Br- et I-, le rendement de pulvérisation, la concentration d'ions primaires implantés et le rendement utile ont été mesurés pour des semi-conducteurs et des métaux. Suite à une faible concentration en halogène à la surface des semi-conducteurs, résultant des processus de décapage, le rendement utile sous bombardement halogène était plus faible que sous bombardement O-. Pour les métaux (p.ex. Ni, Cu et Ag) par contre, une amélioration du rendement utile sous bombardement halogène jusqu'à deux ordres de grandeurs, comparé au bombardement O-, a été mesurée / Secondary Ion Mass spectrometry (SIMS) is a powerful surface analysis technique. The ionisation probability strongly depends on the chemical surface state. The generation of positive secondary ions can be enhanced by surface bombardment with electronegative elements.Due to the optical configuration of the CAMECA NanoSIMS 50, that necessitates an opposite polarity of incoming and ejected ions, analyses of positive ions are realized with primary O- ions, generated in a duoplasmatron ion source. As a consequence of the low O- brightness of the duoplasmatron source, the lateral resolution of the analyses on the NanoSIMS 50 is not satisfactory in the positive secondary mode. In this work, we studied the feasibility of different alternative negative primary ion beams. We investigated the possibility of F-, Cl-, Br- and I- ion generation with a duoplasmatron as a function of the source parameters, notably the magnetic field strength, the arc current and the total gas pressure. The ion current and the beam diameter were measured in order to determine the F-, Cl-, Br- and I- brightness of the source. A comparative study with the O- brightness demonstrates an increase of the F- brightness by a factor of 5.By using the F-, Cl-, Br- and I- bombardment, the sputtering yield, the concentration of implanted primary ions and the useful yield of different semi-conductor and metal samples were analysed. As a consequence of a low halogen concentration, related to etching effects, no enhancement of the useful yield could be noticed for the semi-conductors. For metals however (e.g. Ni, Cu and Ag), useful yield enhancements by up to a factor of 100 compared to the O- bombardment could be demonstrated

La technique Storing Matter a pour objectif d’améliorer la sensibilité et la quantification des analyses par SIMS. Elle consiste à découpler la phase de pulvérisation de l’échantillon de la phase d’analyse. Pour cela, la matière pulvérisée par bombardement ionique est déposée en sous-monocouche sur un collecteur optimisé. Le dépôt est ensuite analysé par SIMS. La probabilité d’ionisation de la matière ne dépend plus de son environnement initial (“effet de matrice”), mais de la surface du collecteur. Le choix du collecteur permet un gain de sensibilité et la quantification des concentrations de l’échantillon initial. L’efficacité de la technique dépend du choix du collecteur et d’un facteur de collection ? caractérisant la phase de pulvérisation-dépôt. Dans ce travail, nous avons étudié la pulvérisation et l’émission de la matière sous bombardement ionique pour optimiser ce facteur ?. Nous avons mis au point un dispositif expérimental ainsi qu’un protocole d’analyse par SIMS qui nous a permis d’étudier la distribution angulaire sous un bombardement d’ions Cs+ avec une incidence oblique pour différents paramètres d’impact. L’étude menée sur quatre cibles (Si, Ge, InP et GaAs) a montré que la distribution angulaire est de forme cosn (?-?Max) pour une énergie et un angle d’impact de respectivement 2 à 10 keV et 30° à 60°. L’exposant n est ~2 tandis que la direction d’émission préférentielle ?Max varie de la normale à la surface (0°) jusqu’à un angle d’émission de 35° dans la direction spéculaire au faisceau en fonction de l’énergie d’impact et de l’angle d’incidence. Ces résultats appliqués à Storing Matter ont permis de déterminer la configuration optimum pour une collection maîtrisée en fonction du bombardement / The Storing Matter technique aims at optimising the sensitivity and quantitativeness of SIMS analysis. It consists in decoupling the sputtering of the specimen from the subsequent analysis step. The specimen is sputtered by means of an ion beam. The emitted particles are deposited at a sub-monolayer level on an optimised collector. The deposit is subsequently analysed in a SIMS instrument. The ionisation probability in SIMS does not depend anymore on the initial sample composition (“Matrix effect”), but on the collector surface chemistry. The collector is chosen in order to increase the sensitivity and to quantify the specimen. The efficiency of this new technique depends on the collector choice and on the collection factor ? characterising the sputter-deposition step. In this work, the sputtering and emission processes under ionic bombardment have been studied in order to optimise this factor ?. We developed an experimental set-up and an analysis protocol based on SIMS that allows us to study the angular distribution under Cs+ bombardment with an oblique incidence for different impact parameters. Four targets (Si, Ge, InP and GaAs) were studied. The results show that the angular distribution is shaped as a cosine function cosn (?-?Max) for impact energies between 2 and 10 keV and for incidence angles from 30 to 60°. Under these conditions, the exponent n is ~2 and the preferential direction of emission ?Max varies from the normal to the surface to 35° in the specular direction in function of the impact energy and the incidence angle. The results allowed to find the best settings for the Storing Matter technique to control the sputtered matter collection in function of the bombardment parameters

Cette thèse est focalisée sur la contribution de l'étude couplée de l’organisation multi-échelle et de la composition isotopique de C et N des carbones de météorites différenciées (acapulcoites – lodranites (A-L)), pour mieux comprendre l’histoire de leur corps-parent. Nous avons systématiquement combiné observations des carbones de ces météorites avec des analogues expérimentaux. Nous avons développé une méthodologie originale couplant l'étude de l'organisation des échelles micrométriques à nanométriques (par Microscopie Electronique par Transmission et Microspectrométrie Raman) et l'analyse isotopique des carbones (par SIMS) sur rigoureusement les mêmes plages de dimensions micrométriques. La comparaison avec les mélanges expérimentaux indique que le graphite d’Acapulco s’est formé par un mode de graphitisation "catalysée par le fer". L’absence de graphitisation des carbones de Lodran dans un environnement riche en fer et chaud est apparemment paradoxale. Toutes nos observations peuvent être réconciliées si nous considérons une collision tardive du corps-parent des A-L avec un corps chondritique apportant matière organique insoluble et chaleur d'impact. Ce scénario est conforté par les analyses isotopiques qui indiquent une formation des carbones des A-L par carbonisation d’un précurseur chondritique et une migration d’effluents carbonés au sein du corps-parent / This thesis is focused on the contribution of the coupling of multi-scale organization and C, N isotopic composition of carbons in differentiated meteorites (acapulcoites – lodranites (A-L)), in order to better understand the history of their parent body. We systematically combined observations of carbons from these meteorites with experimental analogues. We developed an original methodology associating the study of the organization at the micrometre to nanometre scales (by Transmission Electron Microscopy and by Raman Microspectrometry), and the analysis of the isotopic composition of carbons (by SIMS) on strictly the same areas of micrometre dimensions. The comparison with experimental analogues indicates that the Acapulco graphite was formed by a "catalytic" graphitization mode. The absence of graphite in Lodran, in an iron-rich and hot environment, is apparently paradoxical. All our observations can be reconciled if we consider a late collision of the A-L parent body with a chondritic body bringing insoluble organic matter and impact heat. This scenario is strengthened by isotopic analyses, which indicate formation of A-L carbons by carbonization of a chondritic precursor and migration of carbonaceous effluents within the parent-body

FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Na atualidade, grande parte de nossas aÃÃes e relaÃÃes à mediada por objetos eletrÃnicos. De modo especial, crianÃas e adolescentes se iniciam na âaventura tecnolÃgicaâ via jogos eletrÃnicos, os quais passam a intervir diretamente na produÃÃo de novas formas de subjetividades. Os altos investimentos na indÃstria de jogos eletrÃnicos mostram que, longe de um modismo, essa à uma atividade que se estabeleceu em praticamente todo o mundo, o que nos permite e exige pensÃ-la como uma questÃo relevante para as CiÃncias Humanas e, em especial, para a Psicologia Social. Esta pesquisa foi realizada com intuito de refletir acerca dos usos das novas tecnologias na produÃÃo da subjetividade contemporÃnea, investigando, em especial, as expressÃes de poder/controle suscitadas pelo jogo de simulaÃÃo de vida The Sims e demais implicaÃÃes para a sociabilidade de seus usuÃrios. Parte do referencial teÃrico-crÃtico da Escola de Frankfurt e de autores contemporÃneos, a exemplo de Turkle, Lasch e Severiano. As estratÃgias metodolÃgicas utilizadas na pesquisa empÃrica envolveram trÃs etapas, a saber: coleta de dados iniciais em fÃruns sobre o jogo; aplicaÃÃo de questionÃrios, enviados por e-mail aos usuÃrios, e realizaÃÃo de entrevistas on line. Os dados foram analisados inicialmente quantitativamente, com auxilio do software EPInfo, e posteriormente procedeu-se a uma anÃlise qualitativa dos posicionamentos mais relevantes, em articulaÃÃo com os primeiros. Nossos dados confirmam elementos atribuÃveis ao que Lasch (1983) denominou de âCultura do narcisismoâ, na medida em que a categoria âpoder/controleâ recebeu uma forte adesÃo dos jovens pesquisados. Revelam tambÃm nuanÃas distintas deste tipo de cultura, especialmente no que concerne à categoria âsociabilidadeâ, uma vez que esses jovens ainda demonstram a necessidade do outro em sua realidade concreta, preferindo-o Ãqueles do mundo virtual. / At the present time, great part of our actions and relationships are mediated by electronic objects. In a special way, children and adolescents begin in the "technological adventure" saw electronic games, which start to intervene directly in the production in new ways of subjectivities. The high investments in the industry of electronic games show that, far away from an idiom, that is an activity that settled down in practically everyone, what allows us and he/she demands to think her as a relevant subject for the Humanities and, especially, for the Social Psychology. This research is accomplished with intention of contemplating concerning the uses of the new technologies in the production of the contemporary subjectivity, investigating, especially, the expressions of power raised by the game of life simulation "The Sims" and other implications for their usersâ sociability. He/she intends to examine, through interviews on line and personal, that it forms the feelings of power, possibly raised by the referred game, they affect the adolescentsâ relationships with their pairs, as well as their perceptions and capacity of discernment concerning the virtual world and of the real world. This use the theoretical-critical referencial of the School of Frankfurt and contemporary authors, to example of Turkle, Lasch and Severiano. The methodological strategies used in the empiric research involved three stages, to know: collects of initials data in forums on the game; application of questionnaires, sent by e-mail to the users, and accomplishment of interviews on line. The data were analyzed initially quantitatively, with the software EPInfo, and later we proceeded to a qualitative analysis of the most relevant positionings, in articulation with the first ones. Our data confirm attributable elements to the that Lasch (1983) denominated of "Culture of the narcissism", in the measure in that the category "power/control" received a strong adhesion of the researched youths. They also reveal nuances different from this culture type, especially in what it concerns to the category "sociability", once those young ones still demonstrate the need of the other in his/her concrete reality, preferring it to those of the virtual world.

No description available.

L'intégration de composés semi-conducteurs III-V sur silicium devrait conduire au développement de nouveaux dispositifs micro- et optoélectroniques performants. Le composé InGaAs de haute mobilité électronique est un candidat prometteur pour le transistor métal-oxyde-semiconducteur à effet de champ à canal n au-delà du noeud technologique 10 nm. En outre les semi-conducteurs III-V sont aussi des matériaux appropriés pour la fabrication de composants optiques (lasers, diodes) et de dispositifs analogiques ultra-haute fréquence et leur intégration sur une plateforme Si ajoutera de nouvelles fonctionnalités pour le réseau de communications optiques. Cependant la miniaturisation des dispositifs et leur intégration dans les architectures 3D nécessitent le développement de méthodes de caractérisation avancées pour fournir des informations sur leur composition physico-chimique avec une résolution à l'échelle nanométrique.Dans cette thèse, les études physico-chimiques des hétérostructures III-V directement élaborées sur plaquettes de Si 300 mm par épitaxie en phase vapeur sont adressées. Les techniques de spectrométrie de masse d'ions secondaires sont utilisées et développées dans le but d'étudier la raideur des interfaces, la composition chimique et le dopage de couches III-V minces dans des architectures 2D et 3D avec une bonne résolution en profondeur. L'analyse quantitative précise sur un puits quantique InGaAs (PQ) pour des architectures 2D et 3D a été réalisée en utilisant les techniques SIMS magnétique et Auger. Pour obtenir le profil chimique des structures III-V étroites et répétitives, une méthode de moyenne des profils a été développée pour ces deux techniques. Egalement, la reconstruction 3D et le profil en profondeur de tranchées individuelles (moins de cent nanomètres de largeur) contenant un PQ d’InGaAs mince obtenu par croissance sélective dans des cavités de dioxyde de silicium en utilisant la méthode de piégeage des défauts par rapport d’aspect ont été obtenus avec succès en utilisant le SIMS à temps de vol ainsi que la sonde atomique tomographique. Enfin, les résultats ont été corrélés avec des mesures de photoluminescence. / The integration of III-V semiconductor compounds on silicon should lead to the development of new highly efficient micro- and opto-electronic devices. High mobility InGaAs material is a promising candidate for n-channel metal-oxide semiconductor field-effect transistor beyond the 10 nm technology node. Moreover III-V semiconductors are also suitable materials for fabrication of optical (lasers, diodes) and ultra-high frequency analog devices and their integration on a Si platform will add new functionalities for optical network and communication. However the miniaturization of devices and their integration into 3D architectures require the development of advanced characterization methods to provide information on their physico-chemical composition with nanometer scale resolution.In this thesis, the physico-chemical studies of III-As heterostructures directly grown on 300 mm Si wafers by metalorganic vapor phase epitaxy are addressed. Secondary ion mass spectrometry techniques are used and developed in order to study interfaces abruptness, chemical composition and doping of III-V thin layers in 2D and 3D architectures with high depth resolution. The accurate quantitative analysis on InGaAs quantum wells (QWs) in 2D and 3D architectures was performed using magnetic SIMS and Auger techniques. To obtain the chemical profiling of narrow and repetitive III-V structures the averaging profiling method was developed for both techniques. Additionally, 3D reconstruction and depth profiling of individual trenches (less than hundred nanometer in width) containing thin InGaAs QWs selectively grown in silicon dioxide cavities using the aspect ratio trapping method were successfully obtained using Time-of-flight SIMS and atom probe tomography. Finally, the results were correlated with photoluminescence measurements.

Les propriétés d'autodiffusion de l’uranium sont essentielles pour la compréhension d’interaction pastille-gaine dans le réacteur. L'objectif de cette thèse est de déterminer les coefficients d'autodiffusion de l'uranium dans l’$UO_2$ hyper-stœchiométrique qui sont contrôlés, dans certaines conditions thermodynamiques, par les défauts ponctuels. Pour cet objectif, trois études différentes ont été réalisées. La première porte sur la compréhension des défauts d'oxygène et les différents réarrangements du réseau après oxydation. Pour cela, des échantillons d’$UO_2$ et d’$UO_{2+x}$ ont été caractérisés par une diffraction neutronique au sein du laboratoire ILL à Grenoble. Les résultats obtenus de l’analyse par la « Pair Distribution Function » montrent que les ions interstitiels ont tendance à être isolés aux faibles valeurs de x mais ils sont groupés aux valeurs plus élevées de x. La deuxième partie vise à étudier les défauts lacunaires d'uranium, prédominants dans les échantillons d’$UO_{2+x}$ recuits à haute température, qui influent directement sur l'autodiffusion de l'uranium. La méthode non destructive de « Spectroscopie d'annihilation de Positron », implémentée au laboratoire CEMHTI à Orléans, a été appliquée. Les résultats ont montré l'existence des lacunes d'uranium dans le matériau et leurs quantités peuvent être estimées en fonction de la mesure de durée de vie des positrons à l'aide d'un modèle de piégeage. La connaissance de la nature des défauts cationiques et anioniques et des équilibres de défauts aide à comprendre la corrélation entre les propriétés importantes du combustible (e.g, la diffusion, le fluage) et les conditions thermodynamiques (T, pO2). / Uranium self-diffusion properties are essential for the understanding of in-reactor pellet-cladding interaction. The aim of this thesis is to determined uranium self-diffusion coefficients in hyper-stoichiometric uranium dioxide under certain thermodynamic conditions, which indeed are governed by the induced point defects. For that purpose, three separate studies were carried out on virgin material. Firstly, to improve the knowledge of oxygen defects and the rearrangements occurring in the oxygen sub-lattice after oxidation, $UO_2$ and $UO_{2+x}$ samples were characterized by neutron diffraction in ILL Grenoble. The results obtained by a Pair Distribution Function analysis show that interstitial ions tend to be isolated at lower x but cluster at higher x. Secondly, to study the predominant uranium vacancy defects in high-temperature annealed $UO_{2+x}$, which directly influence the uranium self-diffusivity, a non-destructive method – Positron Annihilation Spectroscopy, available in CEMHTI, Orleans has been carried out. The results of Doppler broadening spectroscopy of annihilation of electron-positron pairs has proved the existence of uranium vacancies in the materials, and their concentration can be estimated based on the positron lifetime measurements using a trapping model. The knowledge of the nature relating to both cation and anion defects and defect equilibria are used to understand the correlation between important fuel properties (e.g. diffusion, creep) and thermodynamic conditions (i.e. temperature and oxygen partial pressure).

Les dispositifs avancés pour la microélectronique intègrent divers matériaux et sont de dimensions nanométriques. Une connaissance précise de leur composition est requise pour améliorer leurs procédés de fabrication et comprendre leur comportement électrique. Le ToF-SIMS est un candidat intéressant, qui souffre cependant des effets de matrice et ne possède pas toujours une résolution spatiale suffisante. Le but de ce travail est de permettre une analyse quantitative et résolue en profondeur de matériaux et structures pour la microélectronique avancée à l'aide d'un ToF-SIMS standard. Cette étude porte sur SiGe, sur des matériaux à haute permittivité, des implants basse énergie et des matériaux organiques. Elle se concentre sur la préparation d'échantillons, l'optimisation des conditions expérimentales et le traitement de données pour mettre au point des protocoles d'analyse originaux dont la précision est évaluée grâce à d'autres techniques de caractérisation de pointe. Ces protocoles permettent d'améliorer la qualité des analyses en termes de résolution en profondeur, de précision et de reproductibilité / Next generation devices for microelectronics feature nanometric dimensions and incorporate heterogeneous materials. Accurate knowledge is needed on their chemical composition to address elaboration processes and understand electrical properties. ToF-SIMS is an interesting candidate, but it suffers from matrix effects and insufficient depth resolution. The aim of this work is to enable quantitative, depth resolved analysis of materials and structures for advanced devices with a standard ToF-SIMS. Studies focus in SiGe and high-k based materials, ultra shallow implants and materials for organic electronics. We investigate sample preparation, experimental condition optimization and data treatment to setup original analysis protocols. Accuracy of the new protocols is tested with leading edge external characterization techniques in each of the materials of interest. These developments allowed enhanced analysis quality in terms of depth resolution, accuracy and reproducibility.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / O Orógeno Ribeira representa um cinturão de dobramentos e empurrões, gerado no Neoproterozóico/Cambriano, durante a Orogênese Brasiliana, na borda sul/sudeste do Cráton do São Francisco e compreende quatro terrenos tectono-estratigráficos: 1) o Terreno Ocidental, interpretado como resultado do retrabalhamento do paleocontinente São Francisco, é constituído de duas escamas de empurrão de escala crustal (Domínios Andrelândia e Juiz de Fora); 2) o Terreno Oriental representa uma outra microplaca e abriga o Arco Magmático Rio Negro; 3) o Terreno Paraíba do Sul, que constitui-se na escama superior deste segmento da faixa; e 4) o Terreno Cabo Frio, cuja docagem foi tardia, ocupa pequena área no litoral norte do estado do Rio de Janeiro. Em todos os diferentes compartimentos do segmento central da Faixa Ribeira podem ser identificadas três unidades tectono-estratigráficas: 1) unidades pré-1,8 Ga. (ortognaisses e ortogranulitos do embasamento); 2) rochas metassedimentares pós-1,8 Ga; e 3) granitóides/charnockitóides brasilianos. O Complexo Mantiqueira é composto por ortognaisses migmatíticos, tonalíticos a graníticos, e anfibolitos associados, constitui o embasamento pré-1,8 Ga das rochas da Megasseqüência Andrelândia no domínio homônimo do Terreno Ocidental. Foram integrados 68 dados litogeoquímicos dentre ortognaisses e metabasitos do Complexo Mantiqueira. As rochas dessa unidade pertencem a duas séries distintas: série calcioalcalina (rochas intermediárias a ácidas); e série transicional (rochas básicas, ora de afinidade toleítica, ora alcalina). Com base em critérios petrológicos, análise quantitativa e em valores [La/Yb]N, verificou-se que o Complexo Mantiqueira é bastante heterogêneo, incluindo diversos grupos petrogeneticamente distintos. Dentre as rochas da série transicional, foram identificados 2 conjuntos: 1) rochas basálticas toleiíticas, com [La/Yb]N entre 2,13 e 4,72 (fontes do tipo E-MORB e/ou intraplaca);e 2) rochas basálticas de afinidade alcalina, com [La/Yb]N entre 11,79 e 22,78. As rochas da série calciolacalina foram agrupadas em cinco diferentes conjuntos: 1) ortognaisses migmatíticos quartzo dioríticos a tonalíticos, com [La/Yb]N entre 11,37 e 38,26; 2) ortognaisses bandados de composição quarzto diorítica a granodiorítica, com [La/Yb]N entre 4,35 e 9,28; 3) ortognaisses homogênos de composição tonalítica a granítica, com [La/Yb]N entre 16,57 e 38,59; 4) leucognaisses brancos de composição tonalítica/trondhjemítica a granítica, com [La/Yb]N entre 46,69 e 65,06; e 5) ortognaisse róseo porfiroclástico de composição tonalítica a granítica, com [La/Yb]N entre 82,70 e 171,36. As análises geocronológicas U-Pb SHRIMP foram realizadas no Research School of Earth Science (ANU/Canberra/Austrália). Foram obtidas idades paleoproterozóicas para as rochas das duas séries identificadas, interpretadas como a idade de cristalização dos protólitos magmáticos desses gnaisses e metabasitos. Os resultados obtidos mostram uma variação de idades de cristalização de 2139 35 a 2143,4 9,4, para as rochas da série transicional, e de 2126,4 8 a 2204,5 6,7, para aquelas da série calcioalcalina. Dentre todas as amostras estudadas, apenas a amostra JF-CM-516IV forneceu dados discordantes de idades arqueanas (292916 Ma), interpretados como dados de herança. Contudo, evidências dessa herança semelhantes a esta são observadas em outras amostras. Ambas as séries também apresentaram idades de metamorfismo neoproterozóico, no intervalo de 548 17 Ma a 590,5 7,7 Ma que é consistente com o metamorfismo M1 (entre 550 e 590 Ma), contemporâneo à colisão entre os Terrenos Ocidental e Oriental do setor central da Faixa Ribeira (Heilbron, 1993 e Heilbron et al., 1995). / The Ribeira Orogen is a complex orogenic belt developed during the Brasiliano Orogeny, along the southern and southeastern borders of the São Francisco Craton, and is subdivided into four tectono-stratigraphic terranes: 1) the Occidental Terrane, taken as the reworked margin of São Francisco paleocontinent, displays an internal tectonic organization with two crustal scale thrust sheets (Andrelândia and Juiz de Fora); 2) the Oriental Terrane, comprises another crotonic block or microplate and includes the Rio Negro magmatic arc; 3) the Paraíba do Sul Terrane, which comprises the uppermost thrust slice of the central segment of the belt; and 4) the Cabo Frio Terrane, which occupies a restrict area at the coast of Rio de Janeiro State, records a late docking event. Within all the forementioned terranes, it can be identified three litho-tectonic units: pre-1.8 Ga basement units (orthognaisses and orthogranulites); 2) post-1.8 Ga supracrustal rocks; and 3) brasiliano granitoids and charnockitoids. Mantiqueira Complex comprises a great variety of tonalitic to granitic orthogneisses and minor orthoamphibolites. This unit comprises the basement rocks of the Andrelândia Megasequence within the Andrelândia tectonic domain. Lithogeochemical data of 68 samples, including orthogneisses and metabasites, indicate that the Mantiqueira Complex comprises two different series: calcalkaline series (intermediate to acid calcalkaline rocks); and transicional series (alkaline to tholeiitic basic rocks). Based on petrological criteria, quantitative analysis and [La/Yb]N values, it was possible to verify that the Mantiqueira Complex is heterogeneous and includes many petrogenetic groups. The transicional series comprises two groups: 1) tholeitic basic rocks, with [La/Yb]N between 2,13 and 4,72 (E-MORB and/or Intraplate type); and 2) alkaline basic rocks, with [La/Yb]N between 11,79 and 22,78. The calcalkaline rocks of the Mantiqueira Complex may be grouped into five different petrogenetic groups: 1) migmatitic quartz dioritic to tonalitic orthogneisses, with [La/Yb]N between 11,37 and 38,26; 2) banded quartz dioritic to granodioritic orthogneisses, with [La/Yb]N between 4,35 and 9,28; 3) tonalitic to granitic homogeneous orthogneisses, with [La/Yb]N between 16,57 and 38,59; 4) white tonalitic/trondhjemitic to granitic leucogneisses, with [La/Yb]N between 46,69 and 65,06; and 5) pinkish orthogneiss of tonalitic to granitic composition and [La/Yb]N between 82,70 and 171,36. U-Pb SHRIMP geocronological analysis were performed at the Research School of Earth Science (ANU/Canberra/Australia). Paleoproterozoic ages, interpreted as protoliths cristalization ages, were obtained for rocks from both the calcalkaline and transitional series. Obtained results display a range of cristalization ages from 2139 35 to 2143,4 9,4, to the rocks of the transitional series, and from 2126,4 8 to 2204,5 6,7, for those of the calcalkaline one. Among all studied rocks, only one (sample JF-CM-516 IV) yielded discordant archean zircons (292916 Ma), interpreted as inherited ones. However, evidences of archean zircons were obtained from zircons of other samples. All studied samples record a neoproterozoic metamorphic event in the interval from 548 17 Ma to 590,5 7,7 Ma, which is consistent with the M1 metamorphic event (from 550 to 590 Ma), contemporaneous to the main collision of the central segment of Ribeira Belt (collision between the Occidental and Oriental Terranes (Heilbron, 1993 e Heilbron et al., 1995).