Lors d'un tremblement de terre, les transformations physiques et chimiques qui surviennent le long d'une zone de glissement vont conduire à l'altération et à la formation de minéraux. La gouge contient des minéraux magnétiques, qui peuvent être formés sous l'action combinée de la chaleur frictionnelle et par l'action chimique en relation avec les fluides. Ainsi, la gouge a la capacité de se comporter comme un enregistreur magnétique pendant un tremblement de terre. Il s'agit là d'une nouvelle méthode pour identifier les zones de tremblements de terre de glissement. En outre,les minéraux magnétiques initiaux, altérés, et néoformés peuvent être utilisés comme traceurs de certains processus physico chimique.Dans cette étude, nous étudions le magnétisme des roches et l'enregistrement paléomagnétique de la gouge de faille active de Chelungpu qui héberge, entre autres,la zone de glissement principale du tremblement de terre de Chi-Chi (Mw 7.6, 1999,Taiwan). Nous avons bénéficié pour cette étude d'échantillons non altérés provenant des carottes du forage B Taiwan Chelungpu-fault Drilling Project (TCDP). Nous avons également échantillonné la faille de Chelungpu à l'affleurement pour une caractérisation des nanoparticules. Cette caractérisation vise à estimer l'énergie de fracture dans la gouge de faille. / During an earthquake, the physical and the chemical transformations along a slip zone lead to alteration and formation of minerals within the gouge layer of a mature fault zone. The gouge contains magnetic minerals, which could be formed under the combined action of friction heat and fluid. Thus, gouge has the capacity to behave as a magnetic recorder during an earthquake. This constitutes a conceivable way to identify earthquakes slip zones. Besides, altered and neoformed magnetic minerals can be used as tracers of some earthquake processes. In this study, we investigate the rock magnetism and paleomagnetism of the Chelungpu fault gouge that hosts the principal slip zone of the Chi-Chi earthquake (Mw 7.6, 1999, Taiwan) using Taiwan Chelungpu-fault Drilling Project (TCDP) hole-B core samples. We also took a Chelungpu fault outcrop sample for identification of nanoparticle, which associated with fracture energy estimation in fault gouge.

Os sedimentos são de fundamental importância para estudos geomagnéticos, pois fornecem registros contínuos do campo magnético da Terra no passado. Variações na escala de tempo de 102-103 anos são ainda mal compreendidas em função da escassez de dados em alguns setores do globo. Na América do Sul o registro da orientação e intensidade do campo magnético é particularmente escasso, limitando-se a alguns dados do sudoeste da Argentina, com cobertura temporal de no máximo 24.000 anos. Com o objetivo de aprimorar o registro geomagnético da América do Sul, foram realizados estudos de magnetismo ambiental, paleomagnetismo e paleointensidade relativa em um testemunho de sedimento lamoso coletado no Platô de São Paulo (25,50°S e 46,63°W), o qual cobre o período entre 6.000 e 915 anos B.P. (before present) e tem uma taxa de sedimentação de 35.8 cm/ka. Os seguintes parâmetros magnéticos foram monitorados no testemunho IO7610: susceptibilidade magnética (), magnetização remanente anisterética (ARM), magnetização remanente isotermal (IRM) a 1000 mT e -300 mT [IRM1000mT, IRM-300mT], HIRM [Hard IRM= IRM1000mT IRM-300mT)/2], Razão-S [IRM-300mT/ IRM1000mT], ARM/IRM e IRM1000mT/. O controle da mineralogia magnética ao longo da sucessão sedimentar foi feito através de curvas termomagnéticas de alta e baixa temperatura, curvas de histerese, diagramas FORC e curvas ZFC. A principal contribuição para a susceptibilidade ao longo do IO7610 é devida aos minerais de argila, paramagnéticos. A contribuição relativa dos grãos ferromagnéticos tende a aumentar em direção ao topo. Três portadores magnéticos foram identificados ao longo do testemunho através das curvas de aquisição de IRM. O mais importante é a magnetida SD, que contribui com aproximadamente 85% da fração ferromagnética. As outras duas componentes magnéticas têm menor importância e correspondem à magnetita MD e à hematita. Foram identificadas importantes transições no comportamento e concentração dos minerais magnéticos em 4.800, 2.000 e 1.700 anos B.P. Essas mudanças podem ser atribuídas a duas diferentes fontes de sedimento, com base em modelos oceanográficos prévios: a plataforma continental da Argentina e a pluma do Rio da Prata. Variações da remanência natural e dos parâmetros de concentração dos minerais magnéticos indicam que esses sedimentos podem registrar de forma confiável o campo magnético no passado. Dados de paleointensidade foram obtidos através dois protocolos: (i) normalização clássica, pelos parâmetros , ARM10mT e IRM1000mT; e (ii) método pseudo-Thellier. O registro de paleointensidade obtido a partir do IO7610 apesar de apresentar alguma dispersão, mostra uma tendência de aumento da intensidade do campo entre 5.800 e 3.500 anos B.P. e uma tendência de diminuição da intensidade entre 1.200 e 915 anos PB. Tais tendências foram observadas nos modelos geomagnéticos e nos dados dos lagos da Argentina. Os dados direcionais para o testemunho também mostram alguma correlação com os outros dados disponíveis. Nossos resultados sugerem que os sedimentos da plataforma continental brasileira guardam potencialmente um bom registro do campo magnético do passado, e podem ser usados para melhorar a base de dados paleomagnéticos para a região. Além disso, as técnicas de mineralogia magnética se mostraram sensíveis às principais mudanças no contexto oceanográfico do Platô de São Paulo. / Sediments are invaluable targets for a better understanding of geomagnetic field variations, since they represent a continuous record of the ancient field. The secular variation (102-103 years) of the magnetic field is still poorly constrained due to the heterogeneous data distribution of fields direction and intensity throughout the globe. In South America directional and intensity data are even more scarce, being limited to the southwestern Argentina covering the last 24.000 years. In this work we performed a study of environmental magnetism, paleomagnetism and relative paleointensity in a piston core of muddy sediments collected at the São Paulo Plateau (25,50°S e 46,63°W) which covers ages between 6.000 and 915 years B.P. (before present) with a sedimentation rate of 35.8 cm/ky. The following magnetic parameters were monitored in core IO7610: magnetic susceptibility (), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 1000 mT and -300 mT [IRM1000mT, IRM-300mT], HIRM [Hard IRM= IRM1000mT IRM-300mT)/2], S-Ratio [IRM-300mT/ IRM1000mT], ARM/IRM e IRM1000mT/. Magnetic mineralogy control throughout the core was also monitored using thermomagnetic susceptibility analyses at high and low temperature, hysteresis loops, FORC diagrams and ZFC curves. The main contribution to the magnetic susceptibility throughout the core IO7610 arises from paramagnetic clay minerals. The relative contribution of ferromagnetic grains tends to increase towards the top. Three ferromagnetic carriers were identified throughout the sedimentary pile using IRM acquisition curves. The most important is SD magnetite, which contributes with about 85% of the ferromagnetic fraction. The other two magnetic components have smaller significance and correspond to MD magnetite and hematite. We have found important transitions in the behavior and concentration of magnetic carriers at 4.800, 2.000 and 1.700 years B.P. These changes can be attributed to two different sources of sediments according to previous oceanographic models: the Argentinean continental shelf and the plume of the La Plata river. Variations of natural remanence and parameters of concentration of magnetic minerals indicate that these sediments can be reliable records of the ancient field. Relative paleointensities were thus estimated using two protocols: (i) classic normalization, using parameters , ARM10mT e IRM1000mT; and (ii) pseudo-Thellier method. The paleointensity record obtained from IO7610 core is somewhat scattered but still shows increasing trends between 5.800 and 3.500 years B.P. and a decrease in intensity from 1.200 and 915 years B.P. Such trends were noted in the current geomagnetic models and in the record from Argentinean lakes. Directional data for the core also show a fair agreement with the data available for the Argentinean cores. Our results suggest that the shelf sediments of the Brazilian coast can be used to improve the paleomagnetic database in the region. Moreover, the magnetic mineralogy techniques have shown to be sensitive to the major paleoceanographic changes in the São Paulo Plateau.

Os sedimentos são de fundamental importância para estudos geomagnéticos, pois fornecem registros contínuos do campo magnético da Terra no passado. Variações na escala de tempo de 102-103 anos são ainda mal compreendidas em função da escassez de dados em alguns setores do globo. Na América do Sul o registro da orientação e intensidade do campo magnético é particularmente escasso, limitando-se a alguns dados do sudoeste da Argentina, com cobertura temporal de no máximo 24.000 anos. Com o objetivo de aprimorar o registro geomagnético da América do Sul, foram realizados estudos de magnetismo ambiental, paleomagnetismo e paleointensidade relativa em um testemunho de sedimento lamoso coletado no Platô de São Paulo (25,50°S e 46,63°W), o qual cobre o período entre 6.000 e 915 anos B.P. (before present) e tem uma taxa de sedimentação de 35.8 cm/ka. Os seguintes parâmetros magnéticos foram monitorados no testemunho IO7610: susceptibilidade magnética (), magnetização remanente anisterética (ARM), magnetização remanente isotermal (IRM) a 1000 mT e -300 mT [IRM1000mT, IRM-300mT], HIRM [Hard IRM= IRM1000mT IRM-300mT)/2], Razão-S [IRM-300mT/ IRM1000mT], ARM/IRM e IRM1000mT/. O controle da mineralogia magnética ao longo da sucessão sedimentar foi feito através de curvas termomagnéticas de alta e baixa temperatura, curvas de histerese, diagramas FORC e curvas ZFC. A principal contribuição para a susceptibilidade ao longo do IO7610 é devida aos minerais de argila, paramagnéticos. A contribuição relativa dos grãos ferromagnéticos tende a aumentar em direção ao topo. Três portadores magnéticos foram identificados ao longo do testemunho através das curvas de aquisição de IRM. O mais importante é a magnetida SD, que contribui com aproximadamente 85% da fração ferromagnética. As outras duas componentes magnéticas têm menor importância e correspondem à magnetita MD e à hematita. Foram identificadas importantes transições no comportamento e concentração dos minerais magnéticos em 4.800, 2.000 e 1.700 anos B.P. Essas mudanças podem ser atribuídas a duas diferentes fontes de sedimento, com base em modelos oceanográficos prévios: a plataforma continental da Argentina e a pluma do Rio da Prata. Variações da remanência natural e dos parâmetros de concentração dos minerais magnéticos indicam que esses sedimentos podem registrar de forma confiável o campo magnético no passado. Dados de paleointensidade foram obtidos através dois protocolos: (i) normalização clássica, pelos parâmetros , ARM10mT e IRM1000mT; e (ii) método pseudo-Thellier. O registro de paleointensidade obtido a partir do IO7610 apesar de apresentar alguma dispersão, mostra uma tendência de aumento da intensidade do campo entre 5.800 e 3.500 anos B.P. e uma tendência de diminuição da intensidade entre 1.200 e 915 anos PB. Tais tendências foram observadas nos modelos geomagnéticos e nos dados dos lagos da Argentina. Os dados direcionais para o testemunho também mostram alguma correlação com os outros dados disponíveis. Nossos resultados sugerem que os sedimentos da plataforma continental brasileira guardam potencialmente um bom registro do campo magnético do passado, e podem ser usados para melhorar a base de dados paleomagnéticos para a região. Além disso, as técnicas de mineralogia magnética se mostraram sensíveis às principais mudanças no contexto oceanográfico do Platô de São Paulo. / Sediments are invaluable targets for a better understanding of geomagnetic field variations, since they represent a continuous record of the ancient field. The secular variation (102-103 years) of the magnetic field is still poorly constrained due to the heterogeneous data distribution of fields direction and intensity throughout the globe. In South America directional and intensity data are even more scarce, being limited to the southwestern Argentina covering the last 24.000 years. In this work we performed a study of environmental magnetism, paleomagnetism and relative paleointensity in a piston core of muddy sediments collected at the São Paulo Plateau (25,50°S e 46,63°W) which covers ages between 6.000 and 915 years B.P. (before present) with a sedimentation rate of 35.8 cm/ky. The following magnetic parameters were monitored in core IO7610: magnetic susceptibility (), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 1000 mT and -300 mT [IRM1000mT, IRM-300mT], HIRM [Hard IRM= IRM1000mT IRM-300mT)/2], S-Ratio [IRM-300mT/ IRM1000mT], ARM/IRM e IRM1000mT/. Magnetic mineralogy control throughout the core was also monitored using thermomagnetic susceptibility analyses at high and low temperature, hysteresis loops, FORC diagrams and ZFC curves. The main contribution to the magnetic susceptibility throughout the core IO7610 arises from paramagnetic clay minerals. The relative contribution of ferromagnetic grains tends to increase towards the top. Three ferromagnetic carriers were identified throughout the sedimentary pile using IRM acquisition curves. The most important is SD magnetite, which contributes with about 85% of the ferromagnetic fraction. The other two magnetic components have smaller significance and correspond to MD magnetite and hematite. We have found important transitions in the behavior and concentration of magnetic carriers at 4.800, 2.000 and 1.700 years B.P. These changes can be attributed to two different sources of sediments according to previous oceanographic models: the Argentinean continental shelf and the plume of the La Plata river. Variations of natural remanence and parameters of concentration of magnetic minerals indicate that these sediments can be reliable records of the ancient field. Relative paleointensities were thus estimated using two protocols: (i) classic normalization, using parameters , ARM10mT e IRM1000mT; and (ii) pseudo-Thellier method. The paleointensity record obtained from IO7610 core is somewhat scattered but still shows increasing trends between 5.800 and 3.500 years B.P. and a decrease in intensity from 1.200 and 915 years B.P. Such trends were noted in the current geomagnetic models and in the record from Argentinean lakes. Directional data for the core also show a fair agreement with the data available for the Argentinean cores. Our results suggest that the shelf sediments of the Brazilian coast can be used to improve the paleomagnetic database in the region. Moreover, the magnetic mineralogy techniques have shown to be sensitive to the major paleoceanographic changes in the São Paulo Plateau.

L’étude du paléomagnétisme des roches extraterrestres fournit des informations sur les champs magnétiques présents dans le système solaire il y a plusieurs milliards d’années. A travers ce travail de thèse nous avons exploré deux grands aspects : un champ de dynamo sur un corps différencié, la Lune, et des champs magnétique dans le système solaire primitif avec l’étude de chondrites (CM et les rumurutites). Notre étude des échantillons lunaires a permis de confirmer l’existence d’un champ de dynamo ancien de forte intensité (~50 µT) entre 3.8 et 3.3 Ga. En utilisant l’anisotropie de susceptibilité magnétique comme indicateur de paléohorizontale et en faisant l’hypothèse d’une géométrie de champ dipolaire, nous avons déterminé que l’axe de cette dynamo était centré sur l’axe de rotation actuel de la Lune. Les chondrites CM et les Rumurutites ont enregistré des champs magnétiques anciens quelques millions d’années après la formation du système solaire. L’aimantation rémanente des chondrites CM constitue probablement le plus ancien enregistrement paléomagnétique jamais mis en évidence. L’estimation de la paléointensité (2 µT) et les contraintes chronologiques dont nous disposons ne permettent pas de trancher entre un champ d’origine externe (solaire ou nébulaire) ou d’origine interne (dynamo). Cette dernière hypothèse laisse entrevoir la possibilité de la formation de corps partiellement différenciés dès les premiers millions d’année du système solaire. Dans les rumurutites, les conclusions sont similaires, avec une paléointensité également estimée à 2 µT. Cependant l’aimantation étant plus jeune, une origine interne est favorisée. / Paleomagnetic studies of extraterrestrials rocks provide information on magnetic fields that prevailed in the solar system several million years ago.Through this work we have explored two main aspects: a field dynamo on a differentiated body, the moon, and magnetic fields in the early solar system with the study of two chondrites classes; CM and rumurutites. Our study of lunar samples confirmed that an old dynamo field of high intensity (~50 µT) existed on the Moon between at least 3.8 and 3.3 Ga. Using the anisotropy of magnetic susceptibility as a proxy for paleohorizontale and assuming a dipole field geometry, we determined that the dynamo axis was centered on the actual rotation axis of the Moon.CM chondrites and Rumurutites recorded old magnetic fields acquired few million years after the formation of the solar system. The remanent magnetization of CM chondrites is probably the oldest paleomagnetic record never evidenced. The estimated paleointensity (2 µT) and time constraints not allowed to discriminate between a field of external (solar or nebular) or internal origin (dynamo). This latter hypothesis suggests that formation of partially differentiated body could occur during the first million years of the solar system history. In rumurutites, conclusions are similar, with a paleointensity also estimated at ~2µT. However, the magnetization is younger and an internal origin is favored.

Le but de cette thèse est de reconstruire l’évolution environnementale de la région nord de la mer de Chine du Sud au cours du Quaternaire récent. L'objectif est d'identifier des traceurs des interactions continent-océan, de la mousson est-asiatique et de la circulation océanique. Pour cela, des analyses des minéralogies argileuse et magnétique, de la composition en éléments majeurs, et la taille des grains ont été effectuées sur les sédiments de carotte MD12-3432 couvrant les derniers 400 ka avec un taux de sédimentation variant entre 4.5 et 24 cm/ka. Nous avons tout d'abord amélioré les calibrations de la composition en éléments majeurs obtenue par XRF core-scanning. En effet, celles-ci ne corrigeaient pas des variations de teneur en eau interstitielle observées la séquence sédimentaire étudiée. Nous avons donc proposé une correction polynomiale quadratique qui convertit maintenant correctement les données XRF core-scanning en concentrations précises d’éléments majeurs. La composition en élément majeurs, les minéralogies argileuse et magnétique, et la granulométrie indiquent que les changements climatiques à basse latitude influencent les diverses fractions terrigènes de différentes manières. Considérant d’abord les éléments majeurs et les argiles, nous observons que les rapports smectite/(illite+chlorite) et K₂O/Al₂O₃ présentent tous deux des cyclicités orbitales. Le rapport K₂O/Al₂O₃ qui reflète la contribution relative des apports de Taiwan par dénudation, augmente pendant les interglaciaires quand la mousson d’été asiatique est forte. Le rapport smectite/(illite+chlorite) présente des cyclicités également liées à l’excentricité et à la précession en phase avec les changements d’insolation de l’hémisphère nord en été. Connaissant les régions sources de ces argiles, nous suggérons que l’apport en smectite est étroitement lié à l'intensité de l’altération chimique et à la dénudation fluvial induite par les fortes précipitations de mousson, tandis que l’apport d’illite/chlorite depuis Taiwan répond principalement à la dénudation. Le rapport smectite/(illite+chlorite) reflète ainsi principalement l'intensité de l’altération chimique contemporaine (rapide) et donc l’intensité de la mousson d'été asiatique. Les résultats obtenus confirment que la mousson d'été asiatique est renforcée pendant les périodes interglaciaires et quand l'insolation d'été boréal est forte. Les propriétés magnétiques sédimentaires offrent des informations complémentaires sur les changements environnementaux passés dans cette région. La fraction magnétique de la carotte MD12-3432 est composée de magnétites, sulfures de fer et hématite. Des augmentations de teneur en hématite et des diminutions de la granulométrie sédimentaire sont observées aux minima de précession. Ces évènements qui ont lieu pendant les périodes arides pourraient illustrer des apports éoliens depuis le nord de la Chine, liés à des changements d'intensité et/ou de route des vents, probablement aussi liés à l’intensification de la mousson d'hiver. Outre les changements climatiques de basse latitude, le climat global et l'activité tectonique influencent aussi les apports terrigènes dans cette région. Les augmentations à long terme de la teneur en pyrrhotite par rapport à la magnétite et à l’hématite, de la teneur de illite/chlorite indiquent une contribution croissante de sédiment fine d'origine Taiwanaise au cours des derniers 400 ka. Ceci est très probablement lié à l’intensification de l'orogenèse taïwanais. A l'échelle glaciaire-interglaciaire, les variations synchrones des compositions argileuse et magnétique, de la taille des grains sédimentaires et magnétiques, et des taux de sédimentation sont attribuées aux changements de niveau marin. En effet, les bas niveaux marins pendant les périodes glaciaires exposent l’immense plateau continental et permettent à la Rivière des Perles de livrer au site du sédiment terrigène en plus grande quantité et plus grossier. / The aim of this study is to reconstruct late Quaternary environmental changes in the northern South China Sea by applying multi-disciplinary proxies of land-sea interaction, East Asian monsoon, and oceanic circulation. Investigations of clay and magnetic mineralogy, major element composition, and grain size were performed on marine sediment Core MD12-3432 retrieved from the continental slope of the northern South China Sea. The core covers the last 400 ka with a sedimentation rate varying between 4.5 and 24 cm/ka. We examined the accuracy of existing calibration methods on major element composition obtained by XRF core-scanning, because downcore variations in interstitial water content should strongly affect scanned element contents. We proposed a quadratic polynomial correction to account for this effect and implemented it in the calibration methods. Data from Core MD12-3432 show that the improved calibration process now correctly converts XRF core-scanning data into major element concentrations. Our results on high-resolution major element composition, clay and magnetic mineralogy, and grain size data indicate that low-latitude climate changes influence various terrigenous fractions in different ways. In bulk sediment, K₂O/Al₂O₃ ratio mainly reflects the relative contribution of detrital supply from Taiwan, and its variation exhibits eccentricity cycles. The ratio increases during interglacials, showing that strong precipitation and denudation are induced by enhanced East Asian summer monsoon. In clay fractions, smectite/(illite+chlorite) ratio presents both eccentricity and precession periodicities, in phase with the northern hemisphere summer insolation changes and therefore with the East Asian summer monsoon evolution. Based on the knowledge of sediment provenances, these results suggest that high smectite/(illite+chlorite) ratios illustrate contemporaneous chemical weathering intensity in Luzon. It supports the understanding that East Asian summer monsoon is enhanced during interglacial periods and when the boreal summer insolation is strong. Therefore, these two ratios are appropriate sedimentary tracers for East Asian summer monsoon evolution in the South China Sea. The magnetic fraction yields complementary information about environmental changes in the South China Sea. The magnetic mineral assemblage of Core MD12-3432 is mainly composed of magnetite, sulphide, and hematite, and the relative contributions of all these magnetic mineral contents change with time. Variations on precessional band related to the low latitude East Asian monsoon are observed in magnetic properties and grain size values. High magnetic inputs with high hematite proportion, which is part of fine-grain sediment, are observed during the precession minima. These events occurring during arid periods may illustrate enhanced eolian inputs caused by changes in intensity and/or winds pathway of winds, probably related to enhanced winter monsoon. Besides the low-latitude climate changes, global climate and tectonic activity also influence the terrigenous composition at the studied site at different timescales. A long-term increase in pyrrhotite content with respect to magnetite and hematite and in illite/chlorite contents indicates an increasing contribution of fine grained sediments from Taiwan. This is most likely related to the intensification of Taiwanese orogeny over the last 400 ka. On glacial-interglacial scale, coeval increases observed in sedimentation rate, magnetite/pyrrhotite content, kaolinite content, and grain size during glacial periods are attributed to sea-level changes. Low sea-level during glacial periods exposes the vast shelf and allows the Pearl River to deliver more and coarser terrigenous sediments to our site.

A trama de magmas graníticos alojados na crosta intermediária e superior pode-se originar pela ação de forças de corpo (ascensionais, convectivas) e/ou tectônicas. Diferentes mecanismos podem concorrer para a formação de tramas, embora a interação entre a deformação magmática e a tectônica regional seja um dos mecanismos fundamentais, notadamente nos granitos alojados em faixas orogênicas. No Domínio Apiaí da Faixa Ribeira (SP - PR), os batólitos graníticos alongados têm sido historicamente classificados como sintectônicos, ou seja, colocados durante o desenvolvimento de um arco magmático continental neoproterozóico. Os plútons menores, de forma circular a ovalada, geralmente discordantes e com típica coloração avermelhada, são considerados pós-tectônicos ou alojados após a colisão continental entre os diferentes blocos litosféricos que formaram a Faixa Ribeira. Essa classificação esquemática tem sido baseada em geoquímica e geocronologia dos granitos. Este trabalho identificou e mapeou a trama interna dos plútons sin-tectônicos (Ribeirão Branco) e pós-tectônicos (Capão Bonito e Sguário) utilizando a anisotropia de suscetibilidade magnética (ASM), de forma a inserí-los propriamente nos modelos de classificação tectônica, cujas premissas básicas são de natureza estrutural. Os granitos porfiríticos (Ribeirão Branco e Itaóca) possuem uma elevada suscetibilidade magnética (k 10-2 SI), a qual é menor (k 5 x 10-3 SI) nos granitos vermelhos (Capão Bonito e Sguário). A suscetibilidade dos granitos porfiríticos é proveniente de óxidos ferromagnéticos, notadamente magnetita pobre em Ti, que encontra-se frequentemente associada com titanita, biotita e anfibólio. Nos granitos vermelhos a suscetibilidade é gerada por magnetita, variavelmente oxidada (maghemita) e Ti-hematita (hemo-ilmenita), havendo também significativa contribuição da fração paramagnética (biotita cloritizada) à suscetibilidade total nas rochas, quando k < 10-3 SI. O grau de anisotropia magnética (P) tanto nos granitos porfiríticos como nos vermelhos é variável, porém tipicamente maior nos porfiríticos (P = 1,14, dp. 0,08), se comparado aos vermelhos (P = 1,07, dp. 0,05). A maior anisotropia de suscetibilidade no plúton Ribeirão Branco é atribuída a uma incipiente foliação detectada em vários setores do granito, que contrasta com a microestrutura aparentemente isótropa dos granitos vermelhos. O estudo da trama de silicatos no granito porfirítico Itaóca e no granito Capão Bonito mostrou que os eixos principais de anisotropia de suscetibilidade magnética e da orientação preferencial de forma (OPF) de feldspato e de biotita, são correspondentes, porém, comumente oblíquos. Essa obliquidade entre eixos é atribuída às características físicas próprias (forma, tamanho e anisotropia) dos minerais marcadores da trama. O estudo combinado da ASM e da OPF revelou ainda que P tende a crescer com a intensidade da orientação preferencial de silicatos, o que permitiu identificar os domínios de maior deformação magmática e correlacioná-los com a estrutura regional. A trama magnética do granito Ribeirão Branco organiza-se em coerência com uma tectônica regional transcorrente sinistral. Na margem ocidental deste granito, contudo, a orientação da trama é diferente do restante do maciço, tendo sido aparentemente afetada pela intrusão do granito Sguário. A trama magnética do Ribeirão Branco contrasta com a do plúton Itaóca, este último exibindo um padrão concêntrico que antecedeu ao desenvolvimento da deformação transcorrente regional. Zircões do Itaóca forneceram uma idade U-Pb (SHRIMP) concordante de 623 ± 10 Ma, atribuída à cristalização deste plúton. Dados da literatura indicam que o granito Capão Bonito é aproximadamente 15 Ma mais jovem que os batólitos de granito porfirítico. O Capão Bonito, entretanto, apresenta uma trama muito bem organizada, típica de intrusões sin-tectônicas, destacando-se excelente alinhamento da lineação magnética. No granito Sguário, o arranjo da trama é tipicamente helicoidal e, junto com a estrutura do Capão Bonito, podem ter sido organizadas em resposta a uma deformação transcorrente E-W destral. Este evento tardio estaria associado à reativação da zona de cisalhamento Ribeira, que afetou a borda sul do granito Itaóca e que contém uma componente extensional. A deformação transtensiva E-W, que favoreceu a injeção dos granitos vermelhos no Domínio Apiaí, sucederia a um evento tectonomagmático principal, que teria sido responsável pela colocação e deformação dos batólitos de granito porfirítico. A intrusão dos grandes corpos graníticos ocorreu em torno de 615 Ma e foi relacionada à convergência crustal e estiramento subparalelo à Faixa Ribeira, com a deformação localizada notadamente nas estruturas transcorrentes de direção NE-SW. / The fabric of granitic magmas emplaced in the middle and upper crustal levels can be caused by the stress action during the ascension and convection of plutons and/or tectonic strain. Several mechanisms can contribute for the previous thing, nevertheless the interaction between the distortions and tectonic is the domineering one, principally in granites located in orogenic belts. In the Apiaí domain of the Ribeira belt (SP-PR) the elongated granitic batholiths have been historically classified like syn-tectonic and them was emplaced during the development of a neoproterozoic continental magmatic arch. Small Plutons with subcircular to oval forms generally discordant with regard to the disposition of the regional structures and that in turn possess feldspars of reddish typical colour, had been considered pos-tectonic, and therefore, emplaced after the collision that joined the different litho-tectonic units that constitute the Ribeira orogenic belt. This schematic classification of these granites relicts on geochemistry and geochronology data. In this study was identified and recorded in map the internal fabric of the syn-tectonic Ribeirão Branco granite and of the pos-tectonic Capão Bonito and Sguário granites using the anisotropy of magnetic susceptibility (AMS) with the aim of inserting them appropriately in the models of tectonic classification whose basic premises are of structural nature. The porphyritic Ribeirão Branco and Itaóca granites have a high magnetic susceptibility (k = 10-2 SI), which is minor than (k = 5 x 10-3 SI) in the red granites (Capão Bonito, Sguário). In the first ones the poor Ti magnetite is the main source of susceptibility, commonly associated to titanite, biotite and amphibole. In the red granites, the susceptibility is provided by magnetite variability rusty (maghemite) and Ti - hematite (hemo-ilmenite), in addition to the significant contribution of biotite altered by hydrothermal processes. The grade of anisotropy rise (P) in the porphyritic granites (P = 1,14 SD. 0,08) and this is bigger than in the red ones (P = 1,07, SD. 0,05). In the Ribeirão Branco pluton, the high value of P is attributed to an incipient foliation detected in several sectors, which contrasts with the microstructure seemingly isotropic of the red granites. The study of the fabrics of silicates in the porphyritic granites Ribeirão Branco and Itaóca revealed that the orientations of the main axes of AMS and of shape preferred orientation (SPO) of feldspar and mafic silicates (biotite + amphibole) are congruent, nevertheless some obliquities occur. Those obliquities are attributed to the influence of the proper characteristics (form, size, anisotropy) of the marker minerals of the respective sub fabrics. In the same way, the above-mentioned study of silicates fabric demonstrated that P tends to grow up with the intensity of the SPO of silicates, which allowed to identify domains with major magmatic distortion into de granitic bodies and to correlate them with the regional structure. In general, the magnetic fabric of the Ribeirão Branco granite is organized coherently with the tectonic regional sinestral strike-slip shear zones; nevertheless, in the western sector the orientation of the magnetic fabric was likely modified by the accommodation of the Sguário granite. In the Itaóca granite, the organization of the magnetic fabric is different if compared with fabrics of the previous pluton. In Itaóca granite was recorded a fabric with a concentric organization in 623 ± 10Ma. (MSWD 0,31), according to the concordant U-Pb (SHRIMP) age in zircons obtained for the crystallization of the granite, that seems to be occurred before the strain related with the activation of the regional strike-slip shear zones. Geochronology data of the literature indicates that the Capão Bonito granite is approximately 15 Ma. younger than the batholiths of porphyritic granite. The Capão Bonito granite has an organized fabric typical of syn-tectonic intrusions that has an excellent alignment of the magnetic lineation. In the granite Sguário, the fabric has a spiral organization, in the same way as recorded in Capão Bonito, like response to a strain associated with to a small strike-slip shear zone with W-E direction. This event would be related to the reactivation of the Ribeira strike-slip shear zone, which affected the south sector of the Itaóca granite, with the participation of an extensional component. The W-E transtensive deformation that favoured the injection of the red granites in the Apiaí Domain likely was subsequent to a main tetonomagmatic event and this should have been the responsible by the emplacement and strain in the porphyritic granites. The intrusion of the big granitic bodies ~ 615 Ma. and could be it related to the convergence between crustal blocks and to the consequent stretching sub parallel of the Ribeira belt, in which the distortion was located remarkably in the strike-slip shear zones with NE-SW direction.

Plútons graníticos (Patrimônio Santo Antônio, São Domingos, Ouro Verde e Santa Rita) alojados na porção nordeste da Suíte Intrusiva Cunhaporanga (c. 620-590 Ma) intrudiram metassedimentos pelíticos e carbonáticos de baixo grau metamórfico do Grupo Itaiacoca. Os plútons são isótropos, de coloração cinza a rósea e composição monzo- a sienogranítica, predominando granitóides porfiríticos grossos e, secundariamente, tipos inequigranulares a equigranulares. A cartografia regional mostrou que a foliação das rochas metassedimentares encaixantes mergulha dominantemente para NE e contém uma lineação (interseção, mineral) de direção NNW-SSE. A trama metamórfica das encaixantes assume progressivamente a direção NE-SW conforme se aproxima da zona de cisalhamento transcorrente de Itapirapuã, onde quartzo-milonitos verticalizados exibem uma cinemática sinistral. A trama dos plútons foi estudada pela técnica da anisotropia de suscetibilidade magnética (ASM). Foram amostradas 40 estações (300 espécimes) no granito porfírítico Patrimônio Santo Antônio, 7 estações (48 espécimes) no granito equigranular fino de São Domingos, 9 estações (67 espécimes) no granito inequigranular de Ouro Verde e 14 estações (92 espécimes) no granito porfiritico foliado de Santa Rita. A suscetibilidade magnética média (k) do granito Patrimônio Santo Antônio é da ordem de 23,29 x \'10 POT.-3\' SI, enquanto nos granitos Santa Rita (k = 11,85 mSI), São Domingos (k = 7,43 mSI) e Ouro Verde (k = 7,46 mSI) são menores. Por outro lado, a anisotropia magnética (P = \'k IND.max\'/\'k IND.min\', onde \'k IND.max\' > \'k IND.int\' > \'k IND.min\') é menor em Patrimônio Santo Antônio (P = 1,09 ± 0,04) do que no São Domingos (P = 1,21 ± 0,09), Ouro Verde (P = 1,19 ± 0,07) e Santa Rita (P = 1,23 ± 0,11). Estudos termomagnéticos e de magnetização remanente isotermal mostraram que as propriedades magnéticas dos granitoides são dominadas pela magnetita (pobre em Ti) e, secundariamente, Ti-hematita. Sulfetos de Fe (pirita, calcopirita) ocorrem como acessórios. Os óxidos de Fe estão frequentemente associados à titanita, biotita e anfibólio e suas microestruturas são tipicamente magmáticas, exceto no granito Santa Rita onde a microestrutura apresenta evidência de recristalização pós-magmática. A foliação magnética dos maciços graníticos mergulha suave a moderadamente e, no plúton Patrimônio Santo Antônio, exibe um padrão tipicamente dômico. A lineação magnética subhorizontal orienta-se na direção NNW-SSE paralelamente ao eixo do dobramento regional das rochas metassedimentares encaixantes. Esta característica indica que os granitos são sin-tectônicos a um evento deformacional cujo controle está aparentemente relacionado ao funcionamento das grandes transcorrências regionais de direção NE-SW. A ocorrência de domos graníticos (Patrimônio Santo Antônio) e elipsóides magnéticos dominantemente prolatos (São Domingos) sugerem que a trama NNW teria sido formada por uma tectônica que combina transcorrência e extensão. Uma idade concordante U-Pb (SHRIMP) em zircão de 589 ± 6 Ma, atribuída à cristalização do plúton Patrimônio Santo Antônio, indica que a deformação que afetou o granito no estado magmático bem como suas encaixantes ocorreu nos estágios finais da formação da Suíte Intrusiva Cunhaporanga. / Granite plutons located on the northeast of Cunhaporanga Intrusive Suite (Patrimônio Santo Antônio, Ouro Verde, São Domingos and Santa Rita) are emplaced into low grade metasedimentary rocks (Itaiacoca Group) of the Apiaí Domain (Ribeira Belt). Most of these plutons are isotropic with pinkish to grey colors and their compositions vary from monzogranite to sienogranite. They are usually porphyritic and locally inequigranular and equigranular. Regional mapping revealed that the foliation of the metasedimentary host rocks dips mainly to NE while the lineation (intersection, mineral) strikes in the NNW-SSE direction. The host rocks metamorphic fabric rotates progressively to become parallel to the NE-trending Itapirapuã transcurrent shear zone. Kinematic markers such as elongated quartz grains and mica-fish from quartz-milonites indicate the Itapirapuã shear records a sinistral movement. The fabric of the plutons was studied by anisotropy of magnetic susceptibility (AMS) technique. Forty sites (300 specimens) were sampled at the Patrimônio Santo Antônio granite, 7 sites (48 specimens) at São Domingos, 9 sites (67 specimens) at Ouro Verde and 14 sites (92 specimens) at Santa Rita granite. The mean of magnetic susceptibility (k) is higher in Patrimônio Santo Antônio granite (k = 23,29 x \'10 POT.-3\' SI) and lower in the granites of Santa Rita (k = 11,85 mSI), São Domingos (k = 7,43 mSI) and Ouro Verde (k = 7,46 mSI). In contrast the magnetic anisotropy (P) is lower in the Patrimônio Santo Antônio granite (P = 1,09 ± 0,04) and higher in the granites São Domingos (P = 1,21 ± 0,09), Ouro Verde (P = 1,19 ± 0,07) and Santa Rita (P = 1,23 ± 0,11). Thermomagnetic and Isothermal Remanent Magnetization (IRM) studies show that Ti-poor magnetite is the principal carrier of rock magnetic properties but that includes minor contributions of Ti-hematite. Iron oxides are frequently associated with titanite, biotite and amphibole. Microstructures are typically magmatic, except for Santa Rita granite which shows post-magmatic recrystallized microstructures. The magnetic foliation of granitic plutons dips smooth to moderately and for the Patrimônio Santo Antônio body it exhibits a typical dome pattern. The subhorizontal magnetic lineation strikes NNW-SSE parallel to regional folding axe of the metasedimentary rocks. This feature shows that the granites are syntectonic to a deformation event apparently connected to NE-trending transcurrent shears. The occurrence of a foliation dome in the Patrimônio Santo Antônio pluton and prolate magnetic ellipsoids in São Domingos pluton suggest that the NNW-trending structures includes, besides a strike-slip shear fabric, a component of extension that probably assisted the emplacement of the plutons. A U-Pb (SHRIMP) determination in the Patrimônio Santo Antônio zircons have produced a concordia age of 589 ± 6 Ma attributed to the crystallization of the granite. These results indicate that in the latest stages of the development of the Cunhaporanga Intrusive Suite the Apiaí Domain was submitted to a regional strain field recording transcurrent simple shear and extension.

Des modèles géométriques ont été proposés pour reconstruire la géométrie de plis associés aux rampes (par exemple pli sur flexure de faille), en identifiant en particulier la profondeur de niveau de décollement et le déplacement total sur la rampe. Ces méthodes de reconstruction géométrique sont appliquées pour des plis partiellement érodés. Au cours de l'érosion, le cut-off de la rampe peut être érodé et, par conséquent, le déplacement sur la rampe est difficile à quantifier. Dans cette thèse, nous développons onze modèles thermo-géométriques. Les modèles combinent les données géométriques et les données d’enfouissement pour proposer une évolution cinématique d’un pli avec cut-off érodé. Nous supposons que la mise en place d'une unité tectonique produit une anomalie thermique dans le mur de la faille, et que cette anomalie thermique pourrait indiquer une épaisseur de bloc chevauchant. Les modèles fournissent une estimation de la profondeur de décollement et le déplacement total sur une rampe érodée, qui ne dépend pas de taux d’érosion. Dans le cas de chevauchements actifs, les modèles proposent un taux de déplacement et un âge de l'initiation de la faille en fonction de taux d'érosion. Ces données sont utilisées pour proposer un développement cinématique de coupes érodées. Nous appliquons les modèles sur les plis érodés et actif à Taiwan dans les zones de Choshui et Miaoli. On propose des coupes régionales équilibrées en utilisant la technique de modélisation directe. Dans la section Choshui, nous proposons un niveau de détachement de ~5 km à ~14 km, marquée par deux sauts successifs de rampes de ~5 km and ~4 km. En supposant un taux d'érosion à 4 mm/an, l'âge de l’initiation de chevauchement active est entre 3,3 Ma dans la partie intérieure de prisme (Chevauchement de Tili) à 0,9 Ma dans la partie extérieur (Chevauchement de Chelungpu). Le raccourcissement totale sur la coupe de Choshui est ~100 km et le taux de déplacement calculé est ~1 cm/an. Pour tester nos modèles thermo-géométriques dans une chaîne plissée inactive, on applique nos modèles sur les plis érodés associés aux failles de Pine Mountain et Jones Valley dans la chaîne plissée des Appalaches. L'application des modèles thermo-géométriques nous permet d’estimer une quantité de déplacement sur les deux failles et expliquer de manière satisfaisante l'anomalie thermique dans le mur des failles de Pine Mountain et Jones Valley. Afin d'améliorer la description de l’anomalie thermique qui se développe dans le soubassement des failles, on a étudié l'évolution des minéraux magnétiques des roches argileuses le long de quatre sections dans la chaîne plissée à Taiwan. On a remarqué que la greigite (Fe3S4) domine l'assemblage magnétique dans les roches enfouies à moins à moins de de 70°C. La magnétite (Fe3O4) se développe pour des températures d’enfouissement de ~50°C et domine l’assemblage magnétique jusqu'à ~350° C. A partir ~300°C, la pyrrhotite monoclinique (Fe7S8) se développe aux dépens de la magnétite, et à ~350°C, la magnétite n'est plus détecté. Ces résultats peuvent être utilisés en complément d'autres géothermomètres pour identifier les anomalies thermiques dans une gamme de de 50-70°C et de 300-350°C où les caractéristiques des minéraux magnétiques sont identifiées / Geometric models have been proposed to account satisfactorily for ramp-related folds (e.g. fault-bend fold), identifying in particular detachment depth and total shortening. These methods of geometric reconstruction are applied on partially eroded folds. During erosion, the fault cut-off may be removed and as a result, the displacement is difficult to quantify. In this thesis, we develop 11 thermo-geometric models combining geometric description of folds and burial data to propose kinematic evolution of folds with eroded cut-offs. We assume that the emplacement of a tectonic unit will result in a thermal anomaly in the footwall, and that this thermal anomaly might indicate a thickness of the overriding unit. The models provide an estimation of the detachment depth and the total shortening on an eroded ramp, independent of the erosion rate. In the case of active thrusts, the models provide an estimation of the slip rate and the age of the initiation of the thrust as a function of the erosion rate. These data are used to unravel the kinematic development of eroded cross-sections. We apply the models on eroded folds from Taiwan underlined by active thrusts in the Choshui and Miaoli sections. We propose regional balanced cross-sections using forward modeling technique. In the Choshui section, we propose a detachment profile with a depth between ~ 5 km and ~ 14 km, marked by two steps of ~ 5 km. Assuming erosion rate at 4 mm/a, the age of initiation of the active thrusts is ranging from 3.3 Ma inward (Tili thrust) to 0.9 Ma outward (Chelungpu thrust). The total shortening from the whole section is ~100 km and the calculated slip rate is about 1 cm/a. To test our models in a non-active fold-and-thrust belt, we study eroded folds associated to the Pine Mountain thrust and Jones Valley thrust from the Appalachian belt. The application of the thermo-geometric models provides a value of the total shortening and explains satisfactorily the thermal anomaly in the footwall of the Jones Valley thrust. In order to improve the description of the thermal anomaly, we have studied the evolution of magnetic minerals of argillaceous rocks in four sections from the Taiwan thrust belt. We found that the iron sulfide greigite (Fe3S4) is dominating the magnetic assemblage in the less buried rocks (<70°C). The magnetite (Fe3O4) develops at burial temperature of ~50°C and is dominating the magnetic assemblage up to ~350°C. By ~300°C, the monoclinic pyrrhotite (Fe7S8) develops at the expense of magnetite, and at ~350°C, the magnetite is no longer detected. These results can be used complementary to other geothermometers to identify thermal anomalies in the range 50-70°C and 300-350°C where characteristic magnetic minerals are identified

Cette thèse concerne l’étude du message magnétique de la lithosphère océanique. Nous nous sommes, dans un premier temps, intéressés à l’évolution du signal magnétique à travers une section de croûte océanique complète et continue des basaltes jusqu’aux gabbros. Le but était de comprendre comment les propriétés magnétiques des roches peuvent nous renseigner sur les conditions d’altération dans la croûte océanique. Nous avons donc établi un jeu de données magnétiques (température de Curie, paramètres d’hystérésis, mesures magnétiques basse température) sur l’ensemble de la section de croûte océanique forée au site IODP 1256D, dans l’océan Pacifique. Ces données sont confrontées aux températures d’altération, établies par thermo barométrie et mettent en évidence une étroite relation entre l’altération des phases magnétiques et les températures d’altération. De plus, des analyses semi-quantitatives et des observations microscopiques (optique, MEB et MET) mettent en évidence un changement de structure cristalline, associée à une perte de titane, permettant la formation d’une phase secondaire, l’hydroschorlomite, dans un intervalle de forte altération des phases magnétiques (entre 670 et 1028 mbsf (meters below sea floor)). Dans un second temps, l’acquisition de profils d’anomalies magnétiques marines de surface et d’un profil d’anomalies de fond « deep tow » à travers le superchron du Crétacé (entre 83 et 120 Ma) nous a permis de tester la stabilité de polarité du champ géomagnétique durant cette période. Nous mettons en évidence la présence d’anomalies magnétiques : des anomalies de courtes longueurs d’onde ou « tiny-wiggles » à travers l’ensemble du superchron et des anomalies magnétiques de plus grande longueur d’onde, assimilables à de courts intervalles de polarité inverse. Nos mesures montrent que le comportement du champ magnétique durant le superchron n’est pas différent des périodes qui le précèdent (chrons M0-M1-M2) et le suivent (chrons 33n et 33r). La définition de superchron doit être remise en question. / So we, in a first part, studied the evolution of the magnetic signal through a section of a, complete and continuous, oceanic crust, from basalts to gabbros. In order to understand how the magnetic properties of rocks can tell us about the conditions of alteration in the oceanic lithosphere, we established a set of magnetic data (Curie temperature, hysteresis parameters, low temperature magnetic measurements) through the entire section of the oceanic crust, drilled at IODP Site 1256D, in the Equatorial Pacific Ocean. These magnetic data are compared to alteration temperatures, determined by thermobarometry (Alt et al., 2010) and show a close relationship between the alteration of the magnetic phases and the alteration temperatures, including the identification of an interval of strong alteration of the titanomagnetites (between 670 and 1028 mbsf (meters below sea floor). In addition, semi quantitative chemical analysis and microscopic observations (optical, SEM and TEM), performed on titanomagnetites, show a change in crystalline structure and a loss of titanium element (Ti4 +) in titanomagnetites to form a secondary phase rich in titanium, in this same interval of strong alteration. In a second part, the acquisition of numerous sea-surface magnetic profiles and a high resolution magnetic profile ("deep tow") through the Cretaceous Normal Superchron (83-120 Ma), allowed us to test the stability of the geomagnetic polarity of the superchron and to highlight the presence of numerous magnetic anomalies: anomalies of short wavelength or "tiny-wiggles” through the entire period and magnetic anomalies of greater length wave, similar to short intervals of reverse polarity. Our measurements show that the behavior of the magnetic field during the superchron is no different from previous periods (chrons M0-M1-M2) and the following magnetic period (chrons 33n and 33R) and the definition of ‘superchron’, long geomagnetic event without inversions, must be questioned

Plútons graníticos (Patrimônio Santo Antônio, São Domingos, Ouro Verde e Santa Rita) alojados na porção nordeste da Suíte Intrusiva Cunhaporanga (c. 620-590 Ma) intrudiram metassedimentos pelíticos e carbonáticos de baixo grau metamórfico do Grupo Itaiacoca. Os plútons são isótropos, de coloração cinza a rósea e composição monzo- a sienogranítica, predominando granitóides porfiríticos grossos e, secundariamente, tipos inequigranulares a equigranulares. A cartografia regional mostrou que a foliação das rochas metassedimentares encaixantes mergulha dominantemente para NE e contém uma lineação (interseção, mineral) de direção NNW-SSE. A trama metamórfica das encaixantes assume progressivamente a direção NE-SW conforme se aproxima da zona de cisalhamento transcorrente de Itapirapuã, onde quartzo-milonitos verticalizados exibem uma cinemática sinistral. A trama dos plútons foi estudada pela técnica da anisotropia de suscetibilidade magnética (ASM). Foram amostradas 40 estações (300 espécimes) no granito porfírítico Patrimônio Santo Antônio, 7 estações (48 espécimes) no granito equigranular fino de São Domingos, 9 estações (67 espécimes) no granito inequigranular de Ouro Verde e 14 estações (92 espécimes) no granito porfiritico foliado de Santa Rita. A suscetibilidade magnética média (k) do granito Patrimônio Santo Antônio é da ordem de 23,29 x \'10 POT.-3\' SI, enquanto nos granitos Santa Rita (k = 11,85 mSI), São Domingos (k = 7,43 mSI) e Ouro Verde (k = 7,46 mSI) são menores. Por outro lado, a anisotropia magnética (P = \'k IND.max\'/\'k IND.min\', onde \'k IND.max\' > \'k IND.int\' > \'k IND.min\') é menor em Patrimônio Santo Antônio (P = 1,09 ± 0,04) do que no São Domingos (P = 1,21 ± 0,09), Ouro Verde (P = 1,19 ± 0,07) e Santa Rita (P = 1,23 ± 0,11). Estudos termomagnéticos e de magnetização remanente isotermal mostraram que as propriedades magnéticas dos granitoides são dominadas pela magnetita (pobre em Ti) e, secundariamente, Ti-hematita. Sulfetos de Fe (pirita, calcopirita) ocorrem como acessórios. Os óxidos de Fe estão frequentemente associados à titanita, biotita e anfibólio e suas microestruturas são tipicamente magmáticas, exceto no granito Santa Rita onde a microestrutura apresenta evidência de recristalização pós-magmática. A foliação magnética dos maciços graníticos mergulha suave a moderadamente e, no plúton Patrimônio Santo Antônio, exibe um padrão tipicamente dômico. A lineação magnética subhorizontal orienta-se na direção NNW-SSE paralelamente ao eixo do dobramento regional das rochas metassedimentares encaixantes. Esta característica indica que os granitos são sin-tectônicos a um evento deformacional cujo controle está aparentemente relacionado ao funcionamento das grandes transcorrências regionais de direção NE-SW. A ocorrência de domos graníticos (Patrimônio Santo Antônio) e elipsóides magnéticos dominantemente prolatos (São Domingos) sugerem que a trama NNW teria sido formada por uma tectônica que combina transcorrência e extensão. Uma idade concordante U-Pb (SHRIMP) em zircão de 589 ± 6 Ma, atribuída à cristalização do plúton Patrimônio Santo Antônio, indica que a deformação que afetou o granito no estado magmático bem como suas encaixantes ocorreu nos estágios finais da formação da Suíte Intrusiva Cunhaporanga. / Granite plutons located on the northeast of Cunhaporanga Intrusive Suite (Patrimônio Santo Antônio, Ouro Verde, São Domingos and Santa Rita) are emplaced into low grade metasedimentary rocks (Itaiacoca Group) of the Apiaí Domain (Ribeira Belt). Most of these plutons are isotropic with pinkish to grey colors and their compositions vary from monzogranite to sienogranite. They are usually porphyritic and locally inequigranular and equigranular. Regional mapping revealed that the foliation of the metasedimentary host rocks dips mainly to NE while the lineation (intersection, mineral) strikes in the NNW-SSE direction. The host rocks metamorphic fabric rotates progressively to become parallel to the NE-trending Itapirapuã transcurrent shear zone. Kinematic markers such as elongated quartz grains and mica-fish from quartz-milonites indicate the Itapirapuã shear records a sinistral movement. The fabric of the plutons was studied by anisotropy of magnetic susceptibility (AMS) technique. Forty sites (300 specimens) were sampled at the Patrimônio Santo Antônio granite, 7 sites (48 specimens) at São Domingos, 9 sites (67 specimens) at Ouro Verde and 14 sites (92 specimens) at Santa Rita granite. The mean of magnetic susceptibility (k) is higher in Patrimônio Santo Antônio granite (k = 23,29 x \'10 POT.-3\' SI) and lower in the granites of Santa Rita (k = 11,85 mSI), São Domingos (k = 7,43 mSI) and Ouro Verde (k = 7,46 mSI). In contrast the magnetic anisotropy (P) is lower in the Patrimônio Santo Antônio granite (P = 1,09 ± 0,04) and higher in the granites São Domingos (P = 1,21 ± 0,09), Ouro Verde (P = 1,19 ± 0,07) and Santa Rita (P = 1,23 ± 0,11). Thermomagnetic and Isothermal Remanent Magnetization (IRM) studies show that Ti-poor magnetite is the principal carrier of rock magnetic properties but that includes minor contributions of Ti-hematite. Iron oxides are frequently associated with titanite, biotite and amphibole. Microstructures are typically magmatic, except for Santa Rita granite which shows post-magmatic recrystallized microstructures. The magnetic foliation of granitic plutons dips smooth to moderately and for the Patrimônio Santo Antônio body it exhibits a typical dome pattern. The subhorizontal magnetic lineation strikes NNW-SSE parallel to regional folding axe of the metasedimentary rocks. This feature shows that the granites are syntectonic to a deformation event apparently connected to NE-trending transcurrent shears. The occurrence of a foliation dome in the Patrimônio Santo Antônio pluton and prolate magnetic ellipsoids in São Domingos pluton suggest that the NNW-trending structures includes, besides a strike-slip shear fabric, a component of extension that probably assisted the emplacement of the plutons. A U-Pb (SHRIMP) determination in the Patrimônio Santo Antônio zircons have produced a concordia age of 589 ± 6 Ma attributed to the crystallization of the granite. These results indicate that in the latest stages of the development of the Cunhaporanga Intrusive Suite the Apiaí Domain was submitted to a regional strain field recording transcurrent simple shear and extension.