A zona de cisalhamento Patos consiste em uma mega-estrutura transcorrente E-W que deformou rochas pré-cambrianas durante a orogênese brasiliana. As relações entre fusão parcial e deformação, os mecanismos de deformação envolvidos na nucleação da estrutura e a evolução termocronológica da milonitização foram investigados por meio de trabalhos de campo e técnicas multidisciplinares tais como a anisotropia de suscetibilidade magnética (ASM), geocronologia (U-Pb SHRIMP) e orientações preferenciais cristalográficas medidas através de difração de elétrons retroespalhados (EBSD). O domo de Santa Luzia, situado na conexão da zona de cisalhamento com a Faixa Seridó, caracteriza-se pela trama magnética levemente oblíqua à elongação NE do corpo. Idades U-Pb obtidas na borda recristalizada de zircões do migmatito forneceram idades de 575 ± 3.4 Ma. Trama magnética e idade semelhantes foram encontradas no granito Acari, sugerindo a contemporaneidade entre o alojamento dos magmas e a deformação cisalhante. No anatexito Espinho Branco, geometrias complexas observadas em campo não são reproduzidas na trama de ASM, a qual concorda com a cinemática da zona de cisalhamento Patos. Entretanto, sítios com suscetibilidades baixas (< 0.5 mSI) exibem dispersões na trama magnética, as quais contrastam com orientações cristalográficas de biotita e dados de campo. Contudo, a anisotropia de remanência anisterética mantém-se coerente com o campo de deformação a que foi submetido o anatexito, sugerindo que a dispersão das direções principais de ASM relaciona-se à fases hidrotermais tardias que desorganizam a trama magnética. Ortognaisses miloníticos situados na borda norte da zona de cisalhamento são marcados por migração de bordas dos grãos, fraturamento intracristalino e mirmequitização periférica. As tramas de eixos [0001] de quartzo exibem máximos em Y nos milonitos de alto-grau, sugerindo ativação do sistema de deslizamento prismático-a. As microestruturas gradam para o estado magmático no contato com o anatexito, sendo comuns tramas randômicas de eixo-c de quartzo. Zircões extraídos de leucossomas fornecem uma idade de 566 ± 5 Ma, atribuídos à cristalização do magma. A margem sul da estrutura exibe uma progressiva redução do tamanho dos grãos e geração de milonitos finos a ultramilonitos sem a presença de fusão parcial. Zircões extraídos de um augen granítico forneceram uma idade de intercepto inferior de 545 ± 14 Ma, atribuída ao metamorfismo. Os milonitos da borda sul registram tramas de eixo-c de quartzo com máximos entre Z e Y, sugerindo ativação dos sistemas romboédrico- e basal-a. Nos feldspatos, os principais sistemas de deslizamento são (010)[001] e (010)[100] em todos os litotipos, com exceção do sistema (100)[010], observado na transição entre migmatitos e os milonitos de baixo grau. Estimativas de temperatura por meio do método TitaniQ registram temperaturas médias de ~ 490ºC nos milonitos da borda sul. O conjunto de resultados permite concluir que: i) a ASM reflete os incrementos finais da deformação regional que afetou os migmatitos, ii) a fusão parcial associada ao cisalhamento dextral do Patos ocorreu em c. 565 Ma, enquanto a milonitização de médio a baixo grau, datada em 545 Ma, caracteriza o retrabalhamento metamórfico ocasionado pela localização da deformação em regime dúctil-rúptil; iii) este retrabalhamento é correlacionável a outras zonas de cisalhamento da Província Borborema, constituindo um evento de caráter regional possivelmente relacionado às colisões tardias na margem oeste do Gondwana e, iv) a zona de cisalhamento Patos foi formada após a colisão dos crátons Oeste Africano e Congo-São Francisco ao escudo da Borborema, acomodando deslocamentos transcorrentes a partir de descontinuidades crustais formadas em estágio pré-colisional. / The Patos shear zone is an E-W transcurrent structure that deformed Precambrian rocks from the Borborema Province during the Neoproterozoic. The relationships between partial melting and deformation, the nucleation of the shear zone and the thermochronological evolution of mylonites were investigated by means of detailed field work coupled with Anisotropy of Magnetic Susceptibility (AMS), U-Pb SHRIMP geochronology and crystallographic fabrics measured through electron backscatter diffraction (EBSD). In the Santa Luzia dome, located within the Seridó Belt, the magnetic lineations are slightly oblique to the dome NE elongation. Zircon recrystallized rims yield U-Pb ages of 575 ± 3.4 Ma. These data are consistent with ages and magnetic fabrics found in the Acari granite, suggesting that magma emplacement and shearing were coeval in the Seridó belt. In the Espinho Branco anatexite, emplaced within the mylonites of the Patos shear zone, complex field leucosome geometries are not reproduced in the magnetic fabric, which is consistent with the kinematics of the shear zone. However, low susceptibilities (< 0.5 mSI) display a scattering of magnetic orientations and do not correlate with biotite lattice fabrics and field foliations. Nevertheless, anisotropy of anhystheretic remanence fabrics remain parallel to the external strain field, suggesting that AMS dispersions may be related to late percolation of hydrothermal fluids. Mylonitic orthogneisses from the northern border of the Patos shear zone are marked by grain boundary migration, intracrystalline fracturing and myrmekitization at the periphery of grains. Quartz [0001] lattice fabrics form maxima mainly on Y, suggesting activation of prism-a slip systems. Towards the contact with migmatites, the microstructures progressively change from solid-state to magmatic, characterized by widespread interstitial quartz and random orientations of quartz c-axis fabrics. Zircons from the leucosomes yield an age of 566 ± 5 Ma, which is attributed to magma crystallization. The southern border of the Patos shear zone is marked by progressive grain size reduction and formation of fine-grained mylonites to ultramylonites without traces of partial melting. An age of 545 ± 14 Ma, obtained in zircons from an ultramylonitic augen granite, constrains the timing of the low-grade metamorphism. These Southern mylonites show quartz [0001] fabrics with maxima spreading between Z and Y, suggesting activation of prism and basal slip systems. In feldspars, the main activated slip systems are (010)[001] and (010)[100] in all rock types, except for the (100)[010] slip system, observed in the transition from migmatites to low-grade mylonites. TitaniQ temperature estimates record mean temperatures of ~ 490ºC for the southern mylonites. These data allows us to conclude that: i) AMS reflects the final strain increments recorded in migmatites during regional deformation, ii) partial melting and dextral shearing in the Patos shear zone occurred at ~ 565 Ma, while low-grade mylonitisation dated at 545 Ma defines a late reworking at ductile-brittle conditions, iii) this reworking event is observed in other areas of the Borborema Province, defining a regional event possibly associated with late collisions in the western margin of Gondwana, iv) the Patos shear zone was nucleated after the collision between the Congo-São Francisco and West-African Cratons, through accommodation of strike-slip displacements localized in crustal discontinuities previously formed in an early pre-collisional stage.

Les chaînes plissées d'avant-pays sont des objets géologiques qui se forment dans un contexte compressif et représentent la partie externe des orogènes.Elles sont composées de nombreuses structures plissées associées à des chevauchements généralement enracinés au sein d'un niveau de décollement peu profond situé dans la partie basale de la couverture sédimentaire. Ces objets géologiques ont été beaucoup étudiés au XXème siècle.Ils ont été modélisés cinématiquement, analogiquement et mécaniquement.S’il est indispensable de tenir compte de l’aspect mécanique en géologie structurale, les modèles mécaniques restent cependant trop peu utilisés par le géologue structuraliste.L'objectif de cette thèse est de montrer comment apporter des contraintes mécaniques à l'étude des structures géologiques, grâce à une théorie mécanique facilement utilisable en géologie structurale.Cette théorie, le calcul à la rupture (Limit Analysis), représente en effet un bon intermédiaire entre les modèles cinématiques et les modèles mécaniques en éléments finis, très complets mais relativement complexes d'utilisation.Nous étudions ici des exemples appartenant à la chaîne plissée d’avant-pays du Jura et utilisons les logiciels Optum G2 et SLAMTec.Nous procédons alors selon deux approches. La première approche, présentée en première partie de ce manuscrit consiste à étudier la déformation passée.Nous nous focalisons sur la région de Saint-Ursanne dans le Nord-Est du Jura, en Suisse et réalisons dans un premier temps une coupe géologique d'une structure que nous étendons ensuite en 3D via une série de coupes balayant l'ensemble de la zone d'étude.Pour réaliser ces coupes nous utilisons à la fois des principes d’équilibrage cinématique, des modélisations mécaniques par calcul à la rupture et des modélisations analogiques en boîte à sable.Nous montrons ainsi l’importance de l’héritage tectonique sur la mise en place des structures de cette région et modélisons mécaniquement l’influence d’un décalage du niveau de décollement par une faille normale héritée, lors d’un épisode compressif ultérieur.Nous montrons alors que ce décalage représente un générateur de failles ainsi qu’un point d’accroche qui ralenti la propagation du front de déformation, contrôlant par ailleurs la direction de la structure qui se développera.Nous montrons également que la topographie joue un rôle majeur dans la mise en place des structures géologiques.Dans la deuxième partie du manuscrit nous abordons une seconde approche qui consiste à étudier la déformation actuelle.Nous changeons cette fois-ci d’échelle pour nous intéresser à la tectonique actuelle de l’ensemble du Jura.Nos modélisations prédisent que cette chaîne plissée, formée par une tectonique de couverture, est aujourd’hui partiellement affectée par une tectonique de socle.Alors que la partie ouest du Jura serait toujours affectée par une tectonique de couverture, le socle devrait aujourd’hui être impliqué dans la déformation au niveau de la partie nord-est.Nous montrons cependant qu’une tectonique de socle n’empêche pas l’activation simultanée des niveaux de décollements situés dans la couverture (les évaporites triasiques, dans le cas du Jura).L’intérêt pratique de ces méthodes est illustré par des questions industrielles : le dernier chapitre présente une étude des coupes géologiques d’un terrain d’étude de la Nagra, situé dans l’est du Jura.Nous regardons la réponse mécanique actuelle en compression de l’interprétation structurale proposée.Les outils numériques utilisés dans l’ensemble de ce travail ont, par ailleurs, fait l’objet d’un tutoriel réalisé dans le cadre d’une mission au sein de l’entreprise Total. / Fold-and-thrust-belts form in a compressive geological context and represent the external part of orogens.They are composed of numerous folds and thrusts generally rooted in a shallow décollement level located in the basal part of the sedimentary cover.These belts have been studied extensively during the XX century. They have been modeled kinematically, analogically and mechanically.The mechanical aspect of deformation must be taken into account in structural geology, but yet, mechanical models remain underused by the structural geologist.The objective of this thesis is to show how to bring mechanical constraints to the study of geological structures with a mechanical theory easily usable in structural geology, the Limit Analysis.This theory represents a good compromise between the kinematic models and the finite element mechanical models, very complete but relatively complicated to use.We study here examples from the Jura fold-and-thrust belt and use the softwares Optum G2 and SLAMTec.We proceed with two different approaches.The first one is presented in the first part of this manuscript and consists in studying the past deformation.We focus on Saint-Ursanne area, in the North-East Switzerland Jura.We construct first a 2D geological cross section of the Mont Terri structure and then we extend this work in 3D by a series of cross sections that scan the whole Saint Ursanne area.These cross-sections are drawn using kinematical rules, mechanical modeling with Limit Analysis and analog sandbox modeling.We show the importance of the tectonic inheritance on the onset of structures in the studied region and we mechanically model the influence of a décollement offset due to an inherited normal fault during a subsequent compressive episode.We show that this offset represents a “fault generator” and a catching point that slows the propagation of the deformation front and furthermore controls the orientation of the structure that develops.We also show that the topography plays a major role in the establishment of geological structures.In the second part of the manuscript we follow a second approach that consists in studying the current deformation.We change of scale and study the current tectonics of the entire Jura.Our models predict that this belt, formed in thin-skin tectonics, is currently partially affected by thick-skin tectonics.The western Jura would be still affected by a thin-skin tectonics, but the basement should be involved in the deformation in the north-east Jura.However, we show that a thick-skin tectonics does not preclude the simultaneous activation of the shallower décollements contained by the sedimentary cover (Triassic evaporites, in the Jura).Practical interest of these methods is illustrated by industrial questions: the last chapter presents a study of geological cross-sections from a studied area of Nagra in the eastern Jura.We look at the current mechanical answer under compression of the proposed structural interpretations.The numerical tools used in this work have been the subject of a tutorial made during a mission at Total company.

A área estudada está inserida no Domínio Transversal da Província Borborema. As unidades litoestratigráficas que compõem o embasamento paleoproterozócio (riaciano) são representadas por rochas ortoderivadas dos Complexos Salgadinho e Cabaceiras. Esses complexos foram individualizados de acordo com as suas diferenças composicionais, texturais e/ou geocronológicas. As rochas metassedimentares de idade paleoproterozóica (Orosiriano) foram interpretadas como constituintes do Complexo Sertânia. O magmatismo no estateriano é caracterizado por ortognaisses sienogranítcos da Suíte Carnoió-Caturité e por metanortositos do Complexo Metanortosítico Boqueirão. As unidades litoestratigráficas do Neoproterozóico são representadas por sucessões metassedimentares Criogenianas do Complexo Surubim e ortognaisses granodioríticos e sienograníticos do início do Ediacarano, denominados de Complexo Sumé e Ortognaisse Riacho de Santo Antônio, respectivamente. O magmatismo granítico do Ediacarano foi caracterizado pelo alojamento dos Plutons Inácio Pereira e Marinho. Os dados geocronológicos (U-Pb em zircão) obtidos indicam, no mínimo, o desenvolvimento de três eventos tectono-magmáticos. As idades de 2042 + 11Ma e 1996 + 13Ma obtidas nos ortoanfibolitos do Complexo Cabaceiras foram interpretadas como a idade de cristalização do protólito e metamorfismo, respectivamente. A idade de 1638 + 13Ma proveniente de hornblenda ortognaisse sienogranítico da Suíte Carnoió-Caturité foi interpretada como a idade de cristalização do protólito, marcando um evento magmático Estateriano de afinidade anorogênica. A idade de 550 + 3.1Ma encontrada em monzogranito porfirítico do Pluton Marinho é um registro do último evento magmático no final do Ediacarano, associado ao estágio tardio de desenvolvimento da Zona de Cisalhamento Coxixola. Os dados estruturais permitiram a individualização de três fases de deformação dúcteis, individualizadas como D1, D2 e D3. A fase D1 foi responsável pela geração de uma foliação S1, observada somente na charneira de dobras F2. O evento D2 é assinalado por uma tectônica contracional com transporte para NNW, observado a partir de bandas de cisalhamento assimétricas e dobras de arrasto em cortes paralelos a lineação de estiramento (L2x). Zonas de cisalhamento dúcteis de geometria e cinemática distintas desenvolveram-se durante a fase D3. As zonas de Cisalhamento Boa Vista, Carnoió e Congo estão orientadas na direção NE-SW e exibem cinemática sinistral em cortes paralelos à lineação de estiramento (L3x). As terminações meridionais dessas zonas de cisalhamento estão conectadas com a Zona de Cisalhamento Coxixola. Essa zona de cisalhamento, de direção WSW-ENE e cinemática destral, atravessa toda a área de estudo, com uma espessura média de rochas miloníticas de 300m. A Zona de Cisalhamento Inácio Pereira ocorre na porção leste da área de estudo, orientada na direção WNW-ESE. A análise geométrica e cinemática dessa zona de cisalhamento sugere uma evolução deformacional através de regime transpressivo oblíquo sinistral. O padrão anastomosado final resultante do desenvolvimento de todas as zonas de cisalhamento da área é relacionado à evolução estrutural de um sistema de zonas de cisalhamento dúcteis conjugadas. / The studied area is inserted in the Transversal Domain of Borborema Province. The Paleoproterozoic (Riacian) basement encompasses mainly by metaplutonic rocks from Salgadinho and Cabaceiras Complex. These complexes were individualized according to their compositional, textural and/or geochronological datas. The Paleoproterozoic (Orosirian) metasedimentary rocks were interpreted as components of Sertânia Complex. The Estatherian magmatic event is characterized by syenogranitic orthogneisses of the Carnoió-Caturité Suite and metaplutonic rocks of Metanorthositic Boqueirão Complex. The Neoproterozoic lithostratigraphic units are represented by Cryogenian metasedimentary successions of Complex Surubim and by Early-Ediacaran granodioritic and syenogranitic orthogneisses and of the Sumé Complex and Riacho de Santo Antonio orthogneisses, respectively. The Ediacaran granitic magmatism was characterized by the emplacement of Inácio Pereira and Marinho Plutons. The geochronological data (LA-ICPMS) indicate at least of three tectono-magmatic events. The 2042 + 13Ma and 1996 + 11Ma ages from amphibolites of Cabaceiras Complex were interpreted as the crystallization age of the protolith and metamorphism, respectively. The age of 1638 + 13Ma from the syenogranitic hornblende orthogneiss of Carnoió-Caturité Suite was interpreted as the crystallization age of the protolith, marking an Estatherian anorogenic magmatic event. The age of 550 + 3.1Ma acquired in a porphyritic monzogranite of Marinho Pluton is a record of the last magmatic event in the Late-Ediacaran, associated with the final stage of development of the Coxixola Shear Zone. The structural data allowed the individualization of three deformation phases, individualized as D1, D2 and D3. D1 was responsible for generating a S1 foliation, observed only at the hinge of F2 folds. The D2 event is marked by a thrust regime with transport to NNW, observed from asymmetrical shear bands and drag folds in sections parallel to stretching lineation (L2x). Ductile shear zones of different geometry and kinematics had been developed during the D3 phase. The NE-SW Boa Vista, Carnoió and Congo Shear zones exhibit sinistral kinematic in sections parallel to stretching lineation (L3x). The southern limits of these shear zones are connected with Coxixola Shear Zone. This WSW-ENE shear zone with dextral kinematics crosscut the entire studied area, with an average of 300m thickness of mylonitic rocks. The WNW-ESE Inácio Pereira Shear Zone is situated in the eastern portion of the studied area, shows geometric and kinematic characteristics in agreement with an evolution through an oblique-sinistral transpressive regime. The structural evolution of a system of conjugate ductile shear zones is responsible by anastomosed framework exposed in a map view.

Orientador: Joel Carneiro de Castro / Banca: Gilmar Vital Bueno / Banca: Sergio Henrique Sousa Almeida / Banca: Yociteru Hasui / Banca: Adilson Viana Soares Jr. / Resumo: Na parte continental desenvolveu-se um estudo para o reconhecimento estrutural, tectônico e geomorfológico, por meio de sensoriamento remoto, com o intuito de identificar as feições lineares transversais que se projetam para a porção norte da Bacia de Santos. Para isso, utilizou-se imagem de satélite SRTM 90 para mapear os principais lineamentos tectônicos, onde foram extraídas aproximadamente 5600 feições lineares no continente. A imagem permitiu a identificação dos lineamentos tectônicos transversais (NW-SE e NNW-SSE) que interceptam as principais estruturas pré-cambrianas (NE-SW). Esses lineamentos transversais foram selecionados e classificados em 47 conjuntos principais de lineamentos e o critério para essa seleção foi verificar o padrão de segmentos contínuos das feições lineares. Esses conjuntos foram objeto de estudo para a interpretação de dados de subsuperfície (geofísicos). Na porção norte da Bacia de Santos foram interpretadas 25 seções sísmicas 2D, 12 dados de poços, assim como dados aeromagnetométricos e gravimétricos, fornecido BDEP-ANP. Por meio da análise nas seções sísmicas com a localização das feições transversais (NW-SE e NNW-SSW) observadas nos mapas estruturais e métodos potenciais, mostram que algumas falhas interpretadas apresentam estrutura-em-flor, ocorrência de inversão do rejeito com a profundidade, mudanças abruptas na espessura ou mesmo o desaparecimento dos refletores ao longo da seção sísmica, que são características de falhas de movimentação laterais. E provavelmente estão associados a falhas de transferência. A integração desses dados em ambiente SIG e tridimensional permitiu identificar seis conjuntos de falha de transferência que foram nomeados de FT-1, FT-2, FT-3, FT-4, FT-5 e FT-6. Esses resultados de subsuperfície foram integrados com aqueles obtidos nas interpretações do continente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the continental area has developed a research for the structural, tectonic and geomorphological recognition, through remote sensing, intending to identify linear features transverse that has a projection for the northern portion of the Santos Basin.. For this, used image satellite SRTM 90m to map the main tectonic lineaments, which were extracted from approximately 5600 linear features on the continent. The image allowed the identification of transverse tectonic lineaments (NW-SE and NNW-SSE) that intersect the main structures of pre-cambrian (NE-SW). These lineaments transverse were selected and classified into 47 segments and criterion for this selection was check the pattern of continuous segments of the linear features. These sets have been object of studied for the interpretation of subsurface data (geophysical). In the northern portion of the Santos Basin were interpreted 25 seismic sections, 12 well data and potential methods data (aeromagnetometric and gravimetric), provided by BDEP-ANP. Through the seismic sections analysis with the location of the features transverse (NW-SE and NNE-SSW) observed in the structural maps and potential methods, demonstrate that some fault interpreted to show flower structures, displacement inversion in depth (inverse at the base and normal at the top), sudden changes of thickness or even disappearance of reflectors, that are characteristic of transcurrent faults. And probably are associated with transfer faults. The integration of these data in GIS and three-dimensional environment allowed identified 6 transfer faults (TF) that were named of TF-1, TF-2, TF-3, TF-4, TF-5 and TF-6. These results of subsurface were integrated with those obtained in the interpretations of the continent by remote sensing, in a GIS environment and threedimensional. The integration allowed observe that the main lineaments interpreted on the continent only... (Complete abstract click electronic access below) / Doutor

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A pesquisa foi desenvolvida a sul do MunicÃpio de IrauÃuba, englobando o distrito de JuÃ, em uma Ãrea de 130kmÂ. A RegiÃo Nordeste do Brasil, especificamente no do Estado do CearÃ, à marcada, geralmente, pelo clima seco e distribuiÃÃo irregular da quadra chuvosa. A captaÃÃo de Ãgua subterrÃnea, muitas vezes, à a Ãnica alternativa para suprir a falta deste recurso quando a estiagem prolongada compromete o abastecimento. Tendo em vista minimizar os erros inerentes da locaÃÃo de um poÃo realizou-se a anÃlise em detalhe das estruturas rÃpteis que afetam os terrenos prÃcambrianos. Litologicamente à constituÃda por rochas Ãgneas e metamÃrficas pertencentes as unidades Pelito-CarbonÃtica e MigmatÃtica. As rochas destas unidades foram submetidas a retrabalhamentos durante o Evento Brasiliano, registrando estruturas dÃcteis e rÃpteis. Nestes terrenos configura-se o âdomÃnio hidrogeolÃgico do cristalinoâ, com a ocorrÃncia de Ãgua subterrÃnea condicionada por estruturas rÃpteis que podem estar interconectadas, e adquirir porosidade secundÃria capaz de facilitar a percolaÃÃo e o armazenamento de fluidos. A caracterizaÃÃo estrutural das feiÃÃes rÃpteis, em escala de detalhe, foi realizada por meio da tÃcnica do âmetro linearâ. O estudo de imagens de sensoriamento remoto consistiu na aplicaÃÃo de tÃcnicas de processamento digital. De forma complementar, utilizou-se a geofÃsica terrestre atravÃs do caminhamento eletromagnÃtico. As direÃÃes de alinhamentos estruturais obtidas pela interpretaÃÃo das imagens de satÃlite sÃo compatÃveis com os resultados da interpretaÃÃo dos dados de fraturas, estudadas nas rochas. As principais famÃlias de fraturas identificadas sÃo a N-S e E-W, secundariamente, NE-SW e NW-SE. O uso da geofÃsica terrestre revelou zonas condutivas relacionada à presenÃa de fraturas em subsuperfÃcie. Com a integraÃÃo dos dados gerados foram selecionadas duas Ãreas potencialmente importantes para exploraÃÃo hidrogeolÃgica, correspondentes as concentraÃÃes C-01, norte de Juà e C-04 nas imediaÃÃes de JuÃ. / This research was carried out in a 130 km2 area, in the Juà village, south of the IrauÃuba town. The Northeast of Brazil, specially the countryside, is marked by arid climate and irregular distribution of rain. The captation of groundwater is normally the only solution to provide water during dry weather. To minimize the natural errors that occur during the location of a well we made detailed analysis of the reptile structures that affect the Precambrian terrains. Lithologically it is constituted by igneous and metamorphic rocks belonging to the Migmatitic and Pelitic-Carbonatic Units. These rocks were reworked during the Brasilian Event, which registered both ductile and ruptile structures. In these terrains the âhydrological domain of the crystallineâ is represented, in which the groundwater is controlled by ruptile structures that may be interconnected to the point of acquiring enough secondary porosity to facilitate the percolation and the storing of fluids. The structural characterization of these ruptile features was made in a detailed scale by means of the âlinear-meterâ technique. The remote sensing images study consisted on the application of digital processing techniques, as well as terrestrial geophysics by means of electromagnetic profiles. The structural trends obtained by satellite images are compatible with the results taken from fracturing data. The main fracture sets are N-S and E-W and secondarily, NE-SW and NW-SE. Geophysical studies revealed conductive zones related to the presence of subsurface fractures. Data integration led to two potentially important areas for hydrogeological exploration, which correspond to the C-01 (north of JuÃ) and C-04 (JuÃ) concentrations.

The Vale KGRA is characterized by high heat flow, two to five times higher than the worldwide average, and by numerous hot springs. The hot springs are aligned along faults. This phenomena is typical of a Basin and Range type geothermal system. The hot geothermal fluids migrate upward along the more permeable, fault planes. The rocks exposed in the Vale area are the Pliocene Chalk Butte formation and the Pleistocene beds of Captain Keeney Pass. Both units are composed of volcaniclastic siltstones, sandstones and conglomerates. The units are differentiated by color, texture and degree of lithification. About 200 meters of the Chalk Butte formation and 100 meters of the beds of Captain Keeney Pass are exposed in the area. Silicification is wide spread in the rocks of the Chalk Butte formation.

A detailed geologic investigation was made of the eastern part of the Dairy Ridge Quadrangle and the western part of the Meachum Ridge Quadrangle, Utah. The area is located in north-central Utah in Rich County. It lies between lat. 41°22'30" N. and lat. 41° 28'50" N. and between long. 111° 21'40" W. and long. 111°25'15" W. The area measures 13.8 km in the north-south direction and 5.5 km in the east-west direction. It is on the eastern side of the Wasatch Range about 20 km west-southwest of Randolph, Utah. Stratigraphic units of Precambrian to Cambrian age crop out in the western part of the area, above the Woodruff thrust fault, and dip west. These include the Precambrian Mutual Formation and the Cambrian Geertsen Canyon Quartzite. Units of Pennsylvanian to Jurassic age crop out in the eastern part of the area below the Woodruff thrust fault. They dip west and are overturned to the east. These units include the following: Pennsylvanian Weber Formation, Permian Grandeur Member of the Park City Formation, Permian Phosphoria Formation, Triassic Thaynes Limestone, Triassic Ankareh Formation, Jurassic Nugget Sandstone, and Jurassic Twin Creek Limestone. The Tertiary Wasatch Formation unconformably overlies all older units in places. The Woodruff thrust fault is the major structural feature of the area. Quartzite of the Precambrian Mutual Formation is thrust eastward over the Pennsylvanian Weber Formation as well as over formations of Permian and Triassic ages. The Woodruff thrust fault strikes about N. 20° E. and dips 18° W. to 33° W. Stratigraphic throw is at least 5,800 m. Probable horizontal displacement is tens of kilometers. The stratigraphic units, under the thrust fault, dip west and are overturned to the east. They form the western limb of a large asymmetrical syncline. The overturned units are cut by a west-dipping high-angle thrust fault. The syncline and the thrust faults were produced by the Sevier orogeny which began in latest Jurassic or earliest Cretaceous time. Deformation may have continued into Paleocene time.

Late-Archaean deformation at Ora Banda 69km northwest of Kalgoorlie, Western Australia, resulted in upright folds (D2), ductile shear zones (D3), and a regional-scale brittle-ductile fault network (D4). Early low-angle faults (D', D1), documented in the surrounding Coolgardie, Kambalda and Boorara Domains are not developed in the Ora Banda Domain, and the fabrics reflect only the latest ENE-WSW shortening event. The western limb of the regional-scale ESE- plunging Kurrawang syncline (D2), is truncated by the Zuleika Shear Zone (D3), a within- greenstone ductile shear zone located 10km southeast of Ora Banda. The shear zone has a much greater strike length (250km) than depth extent, as seismic imagery reveals a sharp truncation against a mid-crustal decollement at a depth of 6km-depth below surface. The Zuleika Shear Zone is a NW-SE trending band of anastomosing S-C mylonite zones formed in conjugate sets of NW- SE trending sinistral and N-S trending dextral shear zones. Widely distributed flattening strains and more restricted zones of non-coaxial shear in the Zuleika Shear Zone, suggest deformation-path partitioning typical of a transpressional tectonic environment. Latetectonic brittle-ductile faults (D4) cross-cut the Zuleika Shear Zone and surrounding greenstones, and hence are not Riedel structures or other lower order faults genetically related to the ductile shearing. Gold mineralisation of the Zuleika Shear Zone began during the ductile deformation (D3), continued through peak metamorphism that postdates the shearing, and finally ceased after the brittle-ductile faulting event (D4). Gold deposits are primarily located where brittle-ductile faults intersect the Zuleika Shear Zone. / Brittle-ductile faults (D4), are developed in three principal structural orientations: N-S (dextral), NE-SW (dextral) and E-W (sinistral). These faults display mutual cross-cutting relationships and were formed synchronously during a single regional shortening event. The brittle-ductile fault network is developed unevenly over the region, being localised in packets of high fracture-density referred to as structural zones. The Ora Banda structural zone is an area of high density faulting in the vicinity of Ora Banda, composed of a network of interlinked faults in which alternating ductile and brittle conditions produced cataclasite, breccia and quartz vein systems overprinting mylonite and schistosity. Other areas of high fracture-density (eg. Grants Patch and Mount Pleasant structural zones), are located within the NW-SE trending Ora Banda mafic sequence and spaced at 10km intervals to the southeast of Ora Banda. This spatial periodicity of high fracturedensity within the mafic sequence may have developed as a result of layer-parallel extension during ENE- WSW regional shortening. Gold deposits are concentrated in the Ora Banda, Grants Patch and Mount Pleasant structural zones. Gold distribution within the Ora Banda structural zone traces out the distribution of brittle-ductile faults, indicating that the fault network was the major pathway for fluid flow during mineralisation. Hydrothermal minerals are integral components of fault fabrics within the structural zone, and textures indicate that the faults were formed under conditions of high fluid pressure and, for much of the deformation, may have been fluid-generated. / At Ora Banda the Enterprise gold deposit (40 tonnes Au) highlights the control of mesoscopic- scale fractures on gold distribution. On aeromagnetic imagery, the Enterprise fault zone appears as a narrow fault structure, but at a mesoscopic-scale, it is a broad zone of interlinked brittle-ductile faults and quartz veins. Fabrics developed in the layered, differentiated dolerite host rocks of the Enterprise fault zone, range from cataclasite to banded mylonite with a major component of net- veined breccia (mesofracturing). Kinematic analyses of fault slip lineations reveal an 055 directed (ENE-WSW) maximum shortening axis during brittle-ductile faulting. Microfabrics of the faults show extensive recrystallisation with significant post-deformation recovery that may be related to late to post - tectonic intrusion of the adjacent Lone Hand Monzogranite. Deformation mechanisms indicate that the D4 event occurred at a low-to-moderate temperature, in a low strain-rate enviromnent typical of mid to upper-greenschist facies crustal conditions. Gold mineralisation in the Enterprise deposit is controlled by faults with high-grade shoot development at the intersection of faults and host rock contacts that may represent gradients in tensile rock-strength. Although gold distribution indicates that faults are a major control on mineralisation, at a microscopic-scale, the control is by a linked network of microfractures that pervades the host rocks. / Fry analysis of gold deposits within the Ora Banda mafic sequence shows clustering into groups with about 10km spacing. Coincidence of high fracture-density zones and gold deposits in 1Okm spaced-corridors reveals the regional-scale nature of gold mineralisation within the brittle-ductile fault network. Fluid-pressure gradients generated by pressure release during high-density fracturing, may have effectively increased fluid-rock ratios by focussing of metamorphic fluids through these areas. The largest gold deposits in the Ora Banda mafic sequence are hosted by 060-090 trending brittle-ductile faults with dilational textures (hydraulic breccia), and minor evidence of slip with negligible offsets. The orientation of these structures is sub-parallel to the regional axis of maximum shortening, hence an environment of fluid overpressuring in the presence of a far-field stress system produced conditions where fluid pressure is greater than or equal to the combined minimum compressive stress and the tensile rock strength. Such conditions are conducive to multiple failure episodes with fluid-pressure cycling and transient permeability as a consequence of fault reactivation. Formation of the brittle-ductile fault network occurred as a result of a delicate balance between deviatoric stress and fluid pressure, hence incremental fault development contributed to, and was a consequence of, the gold mineralisation event. / The geometric relations of shear zones, brittle-ductile faults and gold mineralised zones are similar across all scales of observation from regional to microscopic and are therefore fractal. Fractal geometry indicates that deformation and gold mineralisation are temporally and genetically associated, and this combined with the textural relationships of the gold ores indicates that the sites of gold deposition were not structurally prepared prior to mineralisation. Development of early ductile to later brittle-ductile structures indicates changing conditions of deformation typical of decreasing crustal depth, or a variation of strain rate with time. The lack of a significant change in orientation of the maximum shortening direction and continuance of gold mineralisation throughout ductile and brittle deformation events, implies that deformation was progressive during a bulk shortening that accompanied uplift of the crust.

Abstract not available

Fiordland is located southwest of South Island of New Zealand. The field area of this thesis is in northern Fiordland, at the boundary of pristine arc rocks (Median Tectonic Zone) and a belt of Paleozoic paragneisses and orthogneisses of variable age that represent the metamorphosed paleo-Pacific Gondwana margin.