A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy, Johannesburg 2014 / Namibia is renowned for its abundant mineral resources, a large proportion of which are hosted in the metasedimentary lithologies of the Damara Belt, the northeast-trending inland branch of the Neoproterozoic Pan-African Damara Orogen. Deposit types include late- to post-tectonic (~ 523 – 506 Ma) LCT (Li-Be, Sn-, and miarolitic gem-tourmalinebearing) pegmatites, and uraniferous pegmatitic sheeted leucogranites (SLGs), which have an NYF affinity. Fluid inclusion studies reveal that although mineralization differs between the different types of pegmatites located at different geographic locations, and by extension, different stratigraphic levels, the fluid inclusion assemblages present in these pegmatites are similar; thus different types of pegmatites are indistinguishable from each other based on their fluid inclusion assemblages. Thorough fluid inclusion petrography indicated that although fluid inclusions are abundant in the pegmatites, no primary fluid inclusions could be identified, and rather those studied are pseudosecondary and secondary. Fluid inclusions are aqueo-carbonic (± NaCl), carbonic, and aqueous. It is proposed that all of the pegmatites studied share a similar late-stage evolution, with fluids becoming less carbonic and less saline with the progression of crystallisation. Oxygen isotope ratios allow the discrimination of different pegmatites into two groups, Group A (Sn-, Li-Sn-, and gem-tourmaline-bearing LCT pegmatites), and Group B (Li-Bebearing LCT, and U-bearing NYF pegmatites). Group A pegmatites have O-isotope ratios ranging from 11 to 13 ‰ suggesting that they have an I-type affinity. These values are, however, elevated above those of typical I-type granites (7 - 9 ‰), indicating either a postemplacement low-temperature exchange with meteoric fluid, high-temperature hydrothermal exchange with δ18O country rocks during emplacement, or the derivation of these pegmatites from a non-pelitic/S-type metaigneous source. Group B pegmatites have higher δ18O ratios (δ18O = 15 - 16 ‰), indicative of their S-type affinity, and their derivation from metapelitic source rocks. δD values of all the pegmatites range from -40 ‰ to -90 ‰ indicating that the pegmatitic fluids are primary magmatic with a metamorphic fluid component. Trends in the trace element concentrations of both Group A and Group B pegmatites are very similar to each other, making the two groups indistinguishable from each other on this basis. The Damaran pegmatites also share similar geochemical trends with their country rocks. There is, however, no direct field evidence to suggest that the pegmatites were derived from the in situ anatexis of the country rocks. It is more likely that anatexis occurred some distance away from where the pegmatites were ultimately emplaced, and that the melts migrated and were finally emplaced in pre-existing structures, possibly formed during Damaran deformation. O-isotope and Ti-in-quartz geothermometry indicate that Damaran pegmatites can be subdivided into two groups based on their crystallisation temperatures. LCT pegmatites crystallised at temperatures ranging from ~ 450 - 550 ºC, while the NYF pegmatites crystallised at higher temperatures, ranging from 630 - 670 ºC. It is important to note that the subdivision of pegmatites in Groups A and B based on their O-isotope systematics does not correspond with their subdivision into the LCT and NYF pegmatite families according to their crystallisation temperatures. In addition to clarifying aspects of the emplacement and evolution of the Damaran pegmatites, this study points out that there are several discrepancies in the current classification schemes of pegmatites. It shows that in addition to the problems encountered when trying to distinguish between LCT and NYF pegmatites based on their mineralogy, they also cannot truly be distinguished from each other using their geochemical and isotopic characteristics, or their tectonic settings. It is tentatively proposed that crystallisation temperature be considered as an alternative or additional characteristic in the classification of pegmatites, and that it be considered on a regional scale rather than only in the evaluation of the highly evolved end-members of a pegmatite swarm.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / Granitoid intrusions are numerous in southwestern Rajasthan and are useful because they can provide geochronological constraints on tectonic activity and geodynamic conditions operating as the time of intrusion, as well as information about deeper crustal sources. The particularly voluminous Neoproterozoic felsic magmatism in the Sirohi region of Rajasthan is of particular interest as it may have implications for supercontinental (Rodinia and Gondwana) geometry. The Mt. Abu granitoid pluton is located between two major felsic suites, the older (~870-800 Ma) Erinpura granite and the younger (~751-771 Ma) Malani Igneous Suite (MIS). The Erinpura granite is syn- to lateorogenic and formed during the Delhi orogeny, while the MIS is classified as alkaline, anorogenic and either rift- or plume-related. This tectonic setting is contentious, as recent authors have proposed formation within an Andean-type arc setting. The Mt. Abu granitoid pluton has been mapped as partly Erinpura (deformed textural variant) and partly younger MIS (undeformed massive pink granite). As the tectonic settings of the two terranes are not compatible, confusion arises as to the classification of the Mt. Abu granitoid pluton. Poorly-constrained Rb-Sr age dating place the age of formation anywhere between 735 ± 15 and 800 ± 50 Ma. The older age is taken as evidence that the Mt. Abu intrusion was either a late phase of the Erinpura granite. However, U-Pb zircon geochronology clearly indicates that the Mt. Abu felsic pluton is not related to- or contiguous with- the Erinpura granite suite. The major results from this study indicate that the all textural variants within the Mt. Abu pluton were formed coevally at ~765 Ma. Samples of massive pink granite, mafic-foliated granite and augen gneiss from the pluton were dated using U-Pb zircon ID-TIMS at 766.0 ± 4.3 Ma, 763.2 ± 2.7 Ma and 767.7 ± 2.3 Ma, respectively. The simple Mt. Abu pluton is considered as an enriched intermediate I- to A-type intrusion. They are not anorogenic A-types, as, although these felsic rocks have high overall alkali and incompatible element enrichment, no phase in the Mt. Abu pluton contains alkali rich amphibole or pyroxene, nor do REE diagrams for the most enriched samples show the gull-wing shape typical of highly evolved alkaline phases. The alkali-enriched magma may be explained by partial melting of a crustal source such as the high-K metaigneous (andesite) one suggested by Roberts & Clemens (1993), not derivation from a mantle-derived mafic magma. The fairly restricted composition of Mt. Abu granitoids suggests that partial melting and a degree of assimilation/mixing may have been the major factors affecting the evolution of this granitoid pluton; fractional crystallization was not the major control on evolution of these granitoids. Revdar Rd. granitoids that are similar in outcrop appearance and petrography to Mt. Abu granitoids also conform to Mt. Abu granitoids geochemically and are classified as part of the Mt. Abu felsic pluton. Mt. Abu samples from this study have a maximum age range of 760.5-770 Ma, placing the Mt. Abu pluton within the time limits of the Malani Igneous Suite (MIS) as well as ~750 Ma granitoids from the Seychelles. Ages of the Sindreth-Punagarh Groups are also similar. These mafic-ultramafic volcanics are thought to be remnants of an ophiolitic mélange within a back-arc basin setting at ~750-770 Ma. The three Indian terranes are spatially and temporally contiguous. The same contiguity in space and time has been demonstrated by robust paleomagnetic data for the Seychelles and MIS. These similarities imply formation within a common geological event, the proposed Andean-type arc (Ashwal et al., 2002) on the western outboard of Rodinia. The implications are that peninsular India did not become a coherent entity until after this Neoproterozoic magmatism; Rodinia was not a static supercontinent that was completely amalgamated by 750 Ma, as subduction was occurring here simultaneous with rifting elsewhere. Pageiv The Mt. Abu pluton has undergone deformation, with much of the pluton having foliated or augen gneiss textures. The timing of some of the deformation, particularly the augen gneiss and shear zone deformation, is thought to have occurred during intrusion. The Mt. Abu and Erinpura granitoids have experienced a common regional metamorphic event, as hornblende (Mt. Abu) and biotite (Erinpura) give 40Ar/39Ar ages of 508.7 ± 4.4 Ma and 515.7 ± 4.5 Ma, respectively. This event may have reactivated older deformatory trends as well. The temperature of resetting of argon in hornblende coincides with temperatures experienced during upper-greenschist to lower-amphibolite facies metamorphism. These late Pan-African ages are the first such ages reported for the Sirohi region and southern part of the Aravalli mountain range. They offer evidence for the extension of Pan-African amalgamation tectonics (evidence from southern India) into NW India. The age of formation of the Erinpura augen gneiss magma is 880.5 ± 2.1 Ma, thus placing the Erinpura granitoids within the age limits of the Delhi orogeny (~900-800 Ma; Bhushan, 1995). Most deformation observed here would have been caused by compression during intrusion. The Erinpura granitoids are S-type granitoids due to their predominantly peraluminous nature, restricted SiO2-content, normative corundum and the presence of Al-rich muscovite and sillimanite in the mode. Weathered argillaceous metasedimentary material may also have been incorporated in this magma, while the presence of inherited cores suggests relatively lower temperatures of formation for these granitoids as compared to the Mt. Abu granitoids. The age of inheritance (1971 ± 23 Ma) in the Erinpura augen gneiss is taken as the age of the source component, which coincides with Aravalli SG formation. The Sumerpur granitoids differ from the Erinpura granitoids in terms of macroscopic and microscopic texture (undeformed, rarely megaporphyritic) but conform geochemically to the Erinpura granitoid characteristics and may thus be related to the Erinpura granitoid suite.The Revdar Rd. granitoids that are similar in macroscopic appearance to Erinpura granitoids also conform geochemically, and may similarly belong to the Erinpura granite suite. A Revdar Rd. mylonite gneiss with the Erinpura granitoids’ geochemical signature was dated at ~841 Ma, which does not conform to the age of the type-locality Erinpura augen gneiss dated here, but later intrusion within the same event cannot be ruled out because of the uncertainty in the age data (~21 Ma). The presence of garnet in one Revdar Rd. (Erinpura-type) sample implies generation of these granitoids at depth and/or entrainment from the source, similar to the S-type Erinpura granitoids. The Ranakpur granitoids differ significantly from both the Erinpura and Mt. Abu intrusives due to their low SiO2-content and steep REE profiles (garnet present in the source magma); they are thought to have been generated under higher pressures from a more primitive source. The deeper pressure of generation is confirmed by the absence of a negative Eu-anomaly. The Ranakpur quartz syenite dated at 848.1 ± 7.1 Ma is younger by ~30 m.y. than the Erinpura augen gneiss. It is within the same time range as numerous other granitoids from this region as well as the Revdar Rd. granitoid dated in this study. The prevalence of 830- 840 Ma ages may indicate that a major tectonic event occurred at this time. The Ranakpur quartz syenite may have been generated near a subduction or collision zone, where thickened crust allows for magma generation at depth. The deeply developed Nb-anomaly in the spider diagram also implies a larger subduction component to the magma. The Swarupganj Rd. monzogranite is interpreted to have formed by high degrees of partial melting from a depleted crustal source and is dissimilar to other granitoids from this study. More sampling, geochemical and geochronological work needs to be done in order to characterize this intrusion. Pagev The Kishengarh nepheline syenite gneiss is situated in the North Delhi Fold Belt and is the oldest sample dated within this study. The deformation in this sample is due to arc- or continental- collision during a Grenvillian-type orogeny related to the amalgamation of the Rodinia supercontinent (and peninsular India), dated by the highly reset zircons at ~990 Ma. This is considered a DARC (deformed alkaline rock and carbonatite) and represents a suture zone (Leelanandam et al., 2006). The primary age of formation of this DARC is older than 1365 ± 99 Ma, which is the age of xenocrystic titanites from the sample. The granitoid rocks from this study area (Sirohi region) range widely in outcrop appearance, petrography and geochemistry. Granitoids from the Sirohi region dated in this study show a range of meaningful ages that represent geological events occurring at ~880 Ma, ~844 Ma, ~817 Ma, ~789 Ma, ~765 Ma and ~511 Ma. Granitoid magmatism (age of formation) in this region is predominantly Neoproterozoic, and the number of events associated with each granitoid intrusion as well as diverse tectonic settings implies a complexity in the South Delhi Fold Belt that is not matched by the conventional and simplified view of a progression from collision and orogeny during Grenvillian times (Rodinia formation), through late orogenic events, to anorogenic, within-plate (rift-related) alkaline magmatism during Rodinia dispersal. Instead, it is envisaged that convergence and subduction during the formation of Rodinia occurred at ~1 Ga (Kishengarh nepheline syenite deformation), with a transition to continental-continental collision at ~880-840 Ma (Erinpura and Ranakpur granitoids). This was then followed by far-field Mt. Abu and MIS magmatism, related to a renewed period of subduction at ~770 Ma. The last deformatory event to affect this region was that associated with the formation of Gondwana in the late Pan-African (~510 Ma).

A thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy University of the Witwatersrand School of Geosciences and Dublin Institute for Advanced Studies School of Cosmic Physics Geophysics Section February 2016 / Archean cratons, and the Proterozoic orogenic belts on their flanks, form an integral part of the Southern Africa tectonic landscape. Of these, virtually nothing is known of the position and thickness of the southern boundary of the composite Congo craton and the Neoproterozoic Pan African orogenic belt due to thick sedimentary cover. In this work I present the first lithospheric-scale geophysical study of that cryptic boundary and define its geometry at depth. The results are derived from two-dimensional (2D) and three-dimensional (3D) inversion of magnetotelluric data acquired along four semi-parallel profiles crossing the Kalahari craton across the Damara-Ghanzi-Chobe belts (DGC) and extending into the Congo craton. Two dimensional and three-dimensional electrical resistivity models show significant lateral variation in the crust and upper mantle across strike from the younger DGC orogen to the older adjacent cratons. The Damara belt lithosphere is found to be more conductive and significantly thinner than that of the adjacent Congo craton. The Congo craton is characterized by very thick (to depths of 250 km) and resistive (i.e. cold) lithosphere. Resistive upper crustal features are interpreted as caused by igneous intrusions emplaced during Pan-African magmatism. Graphite-bearing calcite marbles and sulfides are widespread in the Damara belt and account for the high crustal conductivity in the Central Zone. The resistivity models provide new constraints on the southern extent of the greater Congo craton, and suggest that the current boundary drawn on geological maps needs revision and that the craton should be extended further south. The storage possibilities for the Karoo Basins were found to be poor because of the very low porosity and permeability of the sandstones, the presence of extensive dolerite sills and dykes. The obvious limitation of the above study is the large spacings between the MT stations (> 10km). This is particularly more limiting in resolving the horizontal layers in the Karoo basin. However the 1D models provide layered Earth models that are consistent with the known geology. The resistivity values from the 1D models allowed porosity of the Ecca and Beaufort group lithologies to be calculated. It is inferred that the porosities values are in the range 5-15 % in the region below the profile. This value is considered too low for CO2 storage as the average porosity of rock used for CO2 is generally more than 10 to 12 percent of the total rock unit volume.

A dissertation submitted to the Faculty of Science, University of Witwatersrand in the fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015. / Northwest Botswana holds a key position for the correlation of the Pan-African mobile belts of southern Africa (i.e. the Damara-Zambezi-Lufilian Orogeny). Phanerozoic cover (Kalahari Group) precludes direct correlation between Proterozoic lithologies of the Damara Belt and thick metasedimentary sequences of northwest Botswana. A combination of new geological and geophysical field observations, interpretation of 50 m resolution aeromagnetic data, and 2.2 km resolution gravity data of Namibia and Botswana, have led to the development of a new sub- Kalahari geological map of the Damara Belt and northwest Botswana. The interpretation of potential field and magnetotelluric (MT) data complemented with both new and published geological data, has improved the identification of the northern and southern margins of the Damara Belt and northwest Botswana, and tectonostratigraphic zones within them. In addition, these correlations have established that the northern margin of the Kalahari Craton on geological maps extends further north than previously noted. The northeast trending Damara Belt is confidently traced into northwest Botswana (Ngamiland) to ~19.5°S, 22.0°E. At this location, in map view, aeromagnetically interpreted structures follow a radial distribution from northwest-striking in the west to northeast-striking in the east. The lithostratigraphic units to the north of this location cannot be confidently correlated with lithostratigraphic units of the Damara Belt. Instead, these units are better correlated with lithostratigraphic units in southern Angola and/or Zambia. The southeastern margin of the Damara Belt is in tectonic contact with the northern margin of the Ghanzi-Chobe Belt as identified in the aeromagnetic images. The Ghanzi-Chobe Belt is correlated with the Sinclair Supergroup in the Rehoboth Subprovince in Namibia. The basal Kgwebe volcanics are correlated with the Oorlogsende Porphyry Member and Langberg Formation and the unconformably overlying metasediments of the Ghanzi Group are correlated with the metasediments of the Tsumis Group. The correlations are based on similar aeromagnetic signatures, lithologies, mineralisation and age dates constrained by carbon isotope chemostratigraphy. Physical property measurements were collected on Meso- to Neoproterozoic lithologies of the Damara Belt, northwest Botswana and Zambia. The measurements included hand held magnetic susceptibility measurements on 303 samples and density measurements on 174 samples. The measurements provide one of the largest physical property databases for Namibia, Botswana and Zambia. In general, the sedimentary units have the lowest magnetic susceptibility values of ~0.207 x 10-3 SI units, respectively. The exceptions are the iron formation and diamictite of the Chuos Formation and conglomerate of the Naauwpoort Formation of 15.2 x 10-3 SI units. The iron iii formation ranges in magnetic susceptibility from 3.34 x 10-3 SI units to 92.0 x 10-3 SI units and the diamictite has a magnetic susceptibility of 7.68 x 10-3 SI units. The igneous lithologies have a density and magnetic susceptibility range from 2.58 g.cm-3 to 3.26 g.cm-3 and 0.001 x 10-3 SI units to 11.6 x 10-3 SI units, respectively. The lower values are associated with pegmatites and rhyolites and the higher values are associated with mafic lithologies and magnetite bearing granites (Omangambo, Salem, Sorris-Sorris and Red Granites). The metamorphic lithologies have the widest range of density and magnetic susceptibility values, between 2.61 g.cm-3 and 3.37 g.cm-3, and -0.299 x 10-3 SI units and 49.5 x 10-3 SI units, respectively. The lower values are associated with low grade metamorphic facies of sedimentary origin, and the higher values are associated with high-grade metamorphic facies of an igneous origin. The first upper crustal-scale interpretation of the Southern African MagnetoTelluric EXperiment (SAMTEX) was developed. The results were derived from 1D Occam inversion models, at depth intervals of 1 – 5 km, 1 – 15 km and 1 – 35 km. The MT data were acquired across the semiparallel, north-south striking DMB, NEN and OKA-CAM profiles in the vicinity of the Namibia – Botswana border between 2006 and 2009. Beneath the MT profiles are two zones of enhanced conductivity, a northern and southern zone. The enhanced conductivity of the northern zone (> 100 Ωm) is associated with individual geological bodies. The southern zone forms an elongated belt of enhanced conductivity (> 300 Ωm) at a depth of less than 5 km. This zone of enhanced conductivity is associated with Proterozoic plate boundaries and subduction zones. Three ~350 km long, north-south trending magnetic profiles were 2D forward modelled to investigate the proposed northward subduction of oceanic crust and subsequently a portion of the Kalahari Plate beneath the Congo Craton. Additionally, the folding pattern of the Ghanzi- Chobe Belt was developed. The interpretation of the magnetic models suggests a northward subduction is a possible cause for the evolution of the Damara Orogen with the regionally eastwest striking negative aeromagnetic anomaly, in northern Namibia, being caused by a thick package (~12 km to 20 km) of metasediments with a modelled magnetic susceptibility of 0. 829 x 10-3 SI units. The Damara Orogen has passed through the subduction-collisional transition but did not evolve into a large-hot orogen. Evidence suggests that the Damara Orogen has gone through the transition of subduction of oceanic crust to terrane accretion (speculated to be represented by the Deep-Level Southern Zone and Chihabadum Complex) and continental collision. However, the doubly vergent wedges did not evolve into an orogenic plateau completing the transition from a small-cold orogen to a large-hot orogen. This is similarly observed in the Alps Orogeny.

Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems ABSTRACT This Ph.D. thesis aims to investigate dynamics of emplacement and tectonic history of selected volcano-plutonic complexes in a continental magmatic arc and back arc setting. The thesis presents new data sets from five field areas, presented in separate chapters, which could be viewed as representing a vertical sections through upper part of an intermediate to felsic magmatic system. From top to bottom in this ‛imaginary' vertical system, the examined units are: (1) andesitic lava domes and (2) sub-volcanic magma chambers (<3 km deep) of the Miocene Štiavnica volcano- plutonic complex, Western Carpathians (Slovakia), (3) Shellenbarger pluton (<3 km depth) within the mid-Cretaceous Minarets caldera, Sierra Nevada batholith in California (USA), and ~7-10 km deep granitoids of (4) Lower-Cretaceous Wallowa batholith, Blue Mountains province in Oregon (USA) and (5) Late Devonian Staré Sedlo complex, central Bohemian Massif (Czech Republic). The research incorporates extensive field and structural data, supported by analysis of igneous textures and anisotropy of magnetic susceptibility (AMS). The latter is further accompanied by detailed examination of magnetic mineralogy using thermomagnetic measurements and optical and back...

La tectonique moléculaire est une partie de la chimie supramoléculaire traitant de la formation d’architectures périodiques mono-, bi- et tridimensionnelles générées via l’auto-assemblage de briques moléculaires complémentaires nommées tectons. Ces derniers possèdent des sites de reconnaissance basés sur des interactions non-covalentes et réversibles. Les interactions largement utilisées sont les liaisons hydrogène et les interactions de coordination. Au cours de cette thèse, les sites de liaison H utilisés sont les nucléobases (thymine, adénine, cytosine, guanine) présentes dans l'ADN et l'ARN, qui ont été introduites en périphérie de différents sites de coordination, tels que les porphyrines, les dipyrrines, les pyridines et les terpyridines. Une bibliothèque de 25 nouveaux tectons à base de nucléobases a été synthétisée et caractérisée. De plus, les tectons ont été cristallisés pour étudier leur auto-assemblage à l'état solide. En présence de cations métalliques externes, les tectons conduisent à la formation de réseaux de coordination de topologies variées associant des liaisons H additionnelles entre les nucléobases. / Molecular tectonics is a field of supramolecular chemistry dealing with the formation of 1D, 2D and 3D molecular networks generated through the self-assembly processes between complementary building blocks (tectons). The latter offer complementary sites leading to recognition patterns via non-covalent and reversible interactions. The interactions widely used are hydrogen bonds and coordination interactions. During this thesis, the H-bonding sites used are the Nucleobases (Thymine, Adenine, Cytosine, Guanine) found in the DNA and RNA, which were introduced to different coordination sites, such as porphyrins, dipyrrins, pyridines and terpyridines. A library of 25 new tectons based on nucleobases were synthesized and characterized. Furthermore, the tectons were crystalized to study their self-assembly in the solid state. In the presence of external metal cations, the tectons lead to the formation of coordination and H-bonded networks of various topology via the self-assembly of nucleobases together with the formation of coordination bonds.

Sinéclises intracrâtonicas são pouco deformadas em comparação a outros tipos de bacias sedimentares, sua arquitetura é caracterizada por unidades litoestratigráficas subhorizontais que podem ser acompanhadas por grandes distâncias sem alterações estruturais significativas. O tectonismo concentra-se em alguns locais, tais como zonas de falha e altos estruturais, onde ocorre toda sorte de estruturas geológicas predominatemente rúpteis. Altos estruturais são locais interessantes para o estudo das sinéclises intracratônicas já que o basculamento de camadas propicia o afloramento de diversas unidades estratigráficas em áreas restritas, mas, sobretudo, são regiões propícias para o entendimento de sua evolução tectônica devido à abundância de estruturas aflorantes. Além disso, essas feições possuem grande importância econômica pois tradicionalmente são investigadas como potenciais armazenadores de hidrocarbonetos. Mais recentemente tem sido utilizadas na estocagem de gás combustível e tem-se avaliado seu potencial para armazenamento de gases do efeito estufa. Na Bacia do Paraná existem diversos altos estruturais, dentre os quais destaca-se, por suas dimensões, o Alto Estrutural de Pitanga. Localizado na região centro-leste do Estado de São Paulo, é uma braquianticlinal alongada na direção NNE-SSW. Em mapa possui formato grosseiramente elíptico, atingindo cerca de 30 km de comprimento em seu eixo maior, de direção NNE-SSW, e até 15 km no eixo menor, de direção WNWESE. O presente trabalho buscou caracterizar em detalhe a geometria dessa braquianticlinal mediante a construção de um mapa de contorno estrutural, e analisar os principais estilos estruturais encontrados nessa região. Com isso, tentar elucidar qual regime tectônico e posição do campo de esforços foram responsáveis pela geração do alto estrutural. Na área do Alto Estrutural de Pitanga foram encontrados evidências de regimes tectônicos compressivo, distensivo e transcorrente registrados em seis fases de deformação. Comparando-se a geomertria e orientação espacial da braquianticlinal bem caracterizada pelo mapa de contorno estrutural, e a orientação das estruturas e campo de esforços associados às diferentes fases de deformação, foi possível identificar o provável tectonismo que deu origem a esse alto estrutural, além de estimar a sua idade. Também foi possível avaliar o seu potencial como armadilha para o sistema petrolífero Irati-Pirambóia. / Intracratonic basins are slightly deformed compared to other types of sedimentary basins. The architecture of intracratonic basins are characterized by subhorizontal stratigraphic units which may be followed by large distances without significant structural changes. Deformation is concentraded in specifc sites such as fault zones and structural highs. Structural highs are interesting sites to study intracratonic basins since the tilting of layers provides the outcrop of different stratigraphic units in restricted areas, but most of all, they are conducive regions for the understanding of their tectonic evolution. Moreover, these features are traditionally investigated as potential traps of hydrocarbons. They have been used in the storage of fuel gas and, more recently, has evaluated its potential for storage of greenhouse gases. In Paraná Basin there are several structural highs among which stands out for its dimensions the so called Pitanga Structural High . Located in the central-eastern part of São Paulo State, south east of Brazil, is a gentle NNE-SSW-oriented anticlinal fold. On the map, it has a roughly elliptical geometry, reaching approximately 30 and 15 km in length on its major NNE-SSW and minor WNW-ESE axis, respectively. This study aimed to characterize, in detail, the Pitanga Structural High geometry by constructing a structural contour map, and to analyze the main structural styles found in this region to clarify what tectonic style and orientation of the stress field were responsible for the generation of this anticlinal. There are varied structural styles found in the area of Pitanga Structural High, related to compressive, transcurrent, and extensional tectonic regimes of six distinct deformation phases. By comparing the spatial orientation and geometry of the anticlinal characterized by structural contour map, and orientation of structures and stress field associated to different stages of deformation, it was possible to identify the likely tectonism which led to this structural high and so estimate its age. It was also possible to evaluate its potential as a trap for the petroleum system Irati-Pirambóia.

L’explosion du nombre et de la variété des données géodésiques, sismologiques et tsunami disponibles est une opportunité exceptionnelle pour produire de nouveaux modèles de la source sismique. Mais ces données n’apportent pas toutes la même information et sont soumises à différentes sources d’incertitudes, rendant la solution au problème inverse non-unique. Dans cette thèse, nous utilisons une méthode d’échantillonnage bayésien pour produire de nouveaux modèles de glissement moins assujettis au sur-ajustement des données et permettant une estimation réaliste de l’incertitude associée aux paramètres estimés. Nous l’appliquons à l’étude du glissement dans trois contextes tectoniques différents : le séisme de Landers (1992, Mw=7.3), la zone de subduction équato-colombienne où s’est produit le séisme de Pedernales (2016, Mw=7.8), et le séisme intra-plaque de Tehuantepec (2017, Mw=8.2). À travers ce travail, nous démontrons l’importance de la considération rigoureuse des incertitudes et les atouts de l’approche bayésienne pour l’étude des différentes phases du cycle sismique. / The explosion in the amount and variety of available geodetic, tsunami, and seismological observations offers an outstanding opportunity to develop new seismic source models. But these data are sensitive to different sources of uncertainty and provide heterogeneous information, which makes the solution of the inverse problem non-unique.In this thesis, we use a Bayesian sampling method to propose new slip models, which benefit from an objective weighting of the various datasets by combining observational and modelling errors. These models are less affected by data overfit and allow a realistic assessment of posterior uncertainties. We apply this method to the study of slip processes occurring in three different tectonic contexts: the Landers earthquake (1992, Mw=7.3), the Ecuador-Colombia subduction zone which hosted the Pedernales earthquake (2016, Mw=7.8), and the intraslab Tehuantepec earthquake (2017, Mw=8.2). Through these analyses, we demonstrate how the study of the seismic cycle can benefit from rigorous uncertainty estimates and Bayesian sampling.

O Pantanal Matogrossense divide-se em onze sub-regiões com características muito distintas, entre elas a Nhecolândia, cuja porção oeste, a Baixa Nhecolândia, apresenta uma fisiografia única no planeta, com milhares de lagoas salinas e hipossalinas intercaladas de forma aparentemente aleatória. Este ambiente, inserido em uma planície muito mais ampla, tem parte de seus limites bruscos e retilíneos. Um deles, a NW, reconhecido na literatura como de origem tectônica, é dado por reativação do Lineamento Transbrasiliano que soergueu a Baixa Nhecolândia. O outro, a SW, embora também retilíneo, não tem na literatura menção a uma possível origem tectônica. Considerando a dificuldade de se encontrar em areias inconsolidadas evidências diretas de possíveis estruturas, optou-se por buscar em variações topográficas evidências deste evento. A região tem gradiente topográfico extremamente baixo, com declividade para SW dando-se em cm/km e a diferença de altitude encontrada no limite NW da ordem de 4 m. Considerando usar modelos digitais de terreno gerados por imagens SRTM para obter perfis altimétricos das porções lineares dos limites daquele ambiente, encontrou-se o problema de ruídos de alta freqüência inerentes ao método, gerando variações de até 16 m na altitude indicada, portanto, várias vezes superiores às variações do terreno. Sendo quase perfeitamente gaussiana a distribuição dos erros em valores negativos e positivos desenvolveu-se um filtro passa-baixas ponderado baseado no princípio dos de média móvel, utilizados para esse fim há décadas. Aplicado este filtro pôde-se não apenas confirmar as variações de altitude do limite NW como obter indicações do limite SW. Com isso pôde-se formular a hipótese de estar toda a Baixa Nhecolândia soerguida em relação às planícies vizinhas, hipótese que tem como corolário a de que a origem do campo de lagos seria função de tal soerguimento, com o rebaixamento do nível de base isolando segmentos das drenagens pré-existentes. A este limite SW nomeou-se Lineamento do Rio Negro, o qual em sua continuidade para NW captura o rio Paraguai e se confunde com o Lineamento Tucavaca, na Bolívia. Por outro lado foi realçada a distribuição das lagoas, utilizando filtros passa-baixas ponderados desenvolvidos previamente para realçar feições geológicas de baixa freqüência. Com isso pôde-se verificar padrões diferenciados na distribuição de lagoas salinas e hipossalinas, com concentração de lagoas salinas dando-se, aparentemente, em porções mais elevadas da planície, como confirmado em uma região, no extremo oeste da Nhecolândia. Não se descarta, portanto, uma influência da tectônica na distribuição das lagoas salinas da Baixa Nhecolândia. / The Pantanal Matogrossense is divided in eleven sub-regions that present highly distinct characteristics. Among these sub-regions is the Nhecolândia, whose West portion presents a unique physiography in the globe, with thousands of randomly disposed saline ponds. This environment is part of a much wider plain and shows part of its limits sharp and straight. The NW limit has a tectonic origin resulting from reactivation of the Transbrasiliano Lineament, which caused the uplift of the Low Nhecolândia. The SW limit is also straight, but no mention to its possible tectonic origin exists. As the sands present are incohesive, there are no direct records of these possible tectonic structures and we opted to use topographic variations to search for evidences. The area has an extremely low topographic gradient and shows cm/km SW-verging declivities, as well as circa 4 m levels differences in the NW limit. Attempts of using digital models generated by SRTM images in order to obtain altimetric profiles of the linear portions in its limits, problems regarding the highfrequency noises that are part of the method were found. This generated up to 16 m variations in the topography, much higher than the real variations on the terrain. As the distribution of both positive and negative errors is nearly gaussian we developed a weighted low-pass filter based on the mobile average principle, which has been used for decades. The application of this filter allowed to confirm not only the variations in the topography in the NW limit but also to obtain information about the SW limit. This lead to the hypothesis that the whole Low Nhecolândia must have been uplifted in relation to the neighboring plains and the field of ponds would have its origin as a function of such uplift as the base level is goes down and isolates segments from former drainages. The SW limit is being called Rio Negro Lineament, which continues to NW and gets the Paraguai River and mix with the Tucavaca Lineament, in Bolivia. On the other hand the distribution of the ponds was remarked when using the weighted low-pass filter previously developed to enhance lowfrequency geological features. We could then verify different patterns in the distribution of both saline and hyphosaline ponds. The first concentrates apparently in higher portions in the plain, as confirmed in a region at the West part of Nhecolândia. The tectonic influence in the distribution of the saline ponds in the Low Nhecolândia cannot be discarded.

O Pantanal Matogrossense divide-se em onze sub-regiões com características muito distintas, entre elas a Nhecolândia, cuja porção oeste, a Baixa Nhecolândia, apresenta uma fisiografia única no planeta, com milhares de lagoas salinas e hipossalinas intercaladas de forma aparentemente aleatória. Este ambiente, inserido em uma planície muito mais ampla, tem parte de seus limites bruscos e retilíneos. Um deles, a NW, reconhecido na literatura como de origem tectônica, é dado por reativação do Lineamento Transbrasiliano que soergueu a Baixa Nhecolândia. O outro, a SW, embora também retilíneo, não tem na literatura menção a uma possível origem tectônica. Considerando a dificuldade de se encontrar em areias inconsolidadas evidências diretas de possíveis estruturas, optou-se por buscar em variações topográficas evidências deste evento. A região tem gradiente topográfico extremamente baixo, com declividade para SW dando-se em cm/km e a diferença de altitude encontrada no limite NW da ordem de 4 m. Considerando usar modelos digitais de terreno gerados por imagens SRTM para obter perfis altimétricos das porções lineares dos limites daquele ambiente, encontrou-se o problema de ruídos de alta freqüência inerentes ao método, gerando variações de até 16 m na altitude indicada, portanto, várias vezes superiores às variações do terreno. Sendo quase perfeitamente gaussiana a distribuição dos erros em valores negativos e positivos desenvolveu-se um filtro passa-baixas ponderado baseado no princípio dos de média móvel, utilizados para esse fim há décadas. Aplicado este filtro pôde-se não apenas confirmar as variações de altitude do limite NW como obter indicações do limite SW. Com isso pôde-se formular a hipótese de estar toda a Baixa Nhecolândia soerguida em relação às planícies vizinhas, hipótese que tem como corolário a de que a origem do campo de lagos seria função de tal soerguimento, com o rebaixamento do nível de base isolando segmentos das drenagens pré-existentes. A este limite SW nomeou-se Lineamento do Rio Negro, o qual em sua continuidade para NW captura o rio Paraguai e se confunde com o Lineamento Tucavaca, na Bolívia. Por outro lado foi realçada a distribuição das lagoas, utilizando filtros passa-baixas ponderados desenvolvidos previamente para realçar feições geológicas de baixa freqüência. Com isso pôde-se verificar padrões diferenciados na distribuição de lagoas salinas e hipossalinas, com concentração de lagoas salinas dando-se, aparentemente, em porções mais elevadas da planície, como confirmado em uma região, no extremo oeste da Nhecolândia. Não se descarta, portanto, uma influência da tectônica na distribuição das lagoas salinas da Baixa Nhecolândia. / The Pantanal Matogrossense is divided in eleven sub-regions that present highly distinct characteristics. Among these sub-regions is the Nhecolândia, whose West portion presents a unique physiography in the globe, with thousands of randomly disposed saline ponds. This environment is part of a much wider plain and shows part of its limits sharp and straight. The NW limit has a tectonic origin resulting from reactivation of the Transbrasiliano Lineament, which caused the uplift of the Low Nhecolândia. The SW limit is also straight, but no mention to its possible tectonic origin exists. As the sands present are incohesive, there are no direct records of these possible tectonic structures and we opted to use topographic variations to search for evidences. The area has an extremely low topographic gradient and shows cm/km SW-verging declivities, as well as circa 4 m levels differences in the NW limit. Attempts of using digital models generated by SRTM images in order to obtain altimetric profiles of the linear portions in its limits, problems regarding the highfrequency noises that are part of the method were found. This generated up to 16 m variations in the topography, much higher than the real variations on the terrain. As the distribution of both positive and negative errors is nearly gaussian we developed a weighted low-pass filter based on the mobile average principle, which has been used for decades. The application of this filter allowed to confirm not only the variations in the topography in the NW limit but also to obtain information about the SW limit. This lead to the hypothesis that the whole Low Nhecolândia must have been uplifted in relation to the neighboring plains and the field of ponds would have its origin as a function of such uplift as the base level is goes down and isolates segments from former drainages. The SW limit is being called Rio Negro Lineament, which continues to NW and gets the Paraguai River and mix with the Tucavaca Lineament, in Bolivia. On the other hand the distribution of the ponds was remarked when using the weighted low-pass filter previously developed to enhance lowfrequency geological features. We could then verify different patterns in the distribution of both saline and hyphosaline ponds. The first concentrates apparently in higher portions in the plain, as confirmed in a region at the West part of Nhecolândia. The tectonic influence in the distribution of the saline ponds in the Low Nhecolândia cannot be discarded.