In recent decades there has been an increased interest in the carbon content of Earth’s geochemical reservoirs due to the impact of atmospheric carbon on the habitability of our planet. Earth’s interior likely hosts a greater mass of carbon than that of the oceans, atmosphere and crust combined, which has buffered the carbon content of the atmosphere over geological time. Yet only a few direct measurements of carbon from the upper mantle, and none from the lower mantle, have been made. Undegassed basalts erupted at mid-ocean ridges have previously been used to estimate the carbon content of the upper mantle. However, due to the low solubility of carbon within silicate melt, these undegassed basalt suites are rare. The majority of basalts have lost their mantle carbon information en route to eruption through the crust. Various crustal processes act to modify the geochemistry of melts before eruption, therefore it is important to be able to characterise the effect of these processes to better interpret the volatile signals preserved in erupted products. Pressure, and therefore depth, is a key parameter controlling volatile solubility and can be estimated using a variety of igneous barometers. This thesis presents results from crys- tallisation experiments conducted on basaltic glass from the Miðfell eruption, Iceland. The experiments provide new data that has been used to test a variety of barometers and crystalli- sation models used by igneous petrologists, and could aid future barometer recalibration. A key part of this work was the development of an experimental method for stabilising 5 kbar conditions in a piston cylinder apparatus. The experiments have shown that clinopyroxene- liquid barometry is more reliable than multi-reaction barometry. However, knowledge of equilibrium clinopyroxene compositions is crucial for accurately determining pressure using the clinopyroxene-liquid barometer. More experiments conducted at mid-crustal pressures are required for a full recalibration of these barometers. The results of testing igneous barometers and crystallisation models have been applied to two suites of olivine-hosted melt inclusions from the Kistufell and Miðfell eruptions to help determine the melt evolution history of these basalts. These eruptions were targeted due to previously measured noble gas isotopic ratios that suggest a primordial mantle component present in their melting regions, and therefore evoking the possibility that they could hold information about deep mantle carbon. Barometry suggests that Miðfell phases equilibrated, and therefore crystallised, at mid-crustal pressures (5–7 kbar), which could allow for the entrapment of undegassed melt inclusions within olivine. The two melt inclusion suites were found to differ in trace element variability, with the observation that the more trace element enriched eruption, Kistufell, had lower relative trace element variability than the more depleted eruption, Miðfell. Several processes, both in the crust and the mantle, are likely responsible for the level of trace element enrichment and variability, including extent of mantle melting, source heterogeneity, and melt transport. The depleted nature of the Miðfell melt inclusions has allowed them to preserve some of the highest CO$_2$/Ba and CO$_2$/Nb ratios ever recorded in basaltic glass, with ratios over five times greater than undegassed mid-ocean ridge basalt values. This carbon enrichment is not due to any crustal melt modification process, but rather pertaining to lower mantle carbon-rich lithologies that have been tapped by the Icelandic mantle plume. The carbon reservoir beneath Miðfell is estimated to contain 744 $\pm$ 188 ppm carbon, 15 times greater than the depleted upper mantle. This value matches estimates of bulk mantle carbon from planetary mass balance calculations and provides evidence for carbon-rich domains within the Earth.

abstract: Seismic observations have revealed two large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath Pacific and Africa. One hypothesis for the origin of LLSVPs is that they are caused by accumulation of subducted oceanic crust on the core-mantle boundary (CMB). Here, I perform high resolution geodynamical calculations to test this hypothesis. The result shows that it is difficult for a thin (~ 6 km) subducted oceanic crust to accumulate on the CMB, and the major part of it is viscously stirred into the surrounding mantle. Another hypothesis for the origin of LLSVPs is that they are caused by thermochemical piles of more-primitive material which is remnant of Earth's early differentiation. In such case, a significant part of the subducted oceanic crust would enter the more-primitive reservoir, while other parts are either directly entrained into mantle plumes forming on top of the more-primitive reservoir or stirred into the background mantle. As a result, mantle plumes entrain a variable combination of compositional components including more-primitive material, old oceanic crust which first enters the more-primitive reservoir and is later entrained into mantle plumes with the more-primitive material, young oceanic crust which is directly entrained into mantle plumes without contacting the more-primitive reservoir, and depleted background mantle material. The result reconciles geochemical observation of multiple compositional components and varying ages of oceanic crust in the source of ocean-island basalts. Seismic studies have detected ultra-low velocity zones (ULVZs) in some localized regions on the CMB. Here, I present 3D thermochemical calculations to show that the distribution of ULVZs provides important information about their origin. ULVZs with a distinct composition tend to be located at the edges of LLSVPs, while ULVZs solely caused by partial melting tend to be located inboard from the edges of LLSVPs. This indicates that ULVZs at the edges of LLSVPs are best explained by distinct compositional heterogeneity, while ULVZs located insider of LLSVPs are better explained by partial melting. The results provide additional constraints for the origin of ULVZs. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2015

Les compositions isotopiques en Nd, Hf, Pb et Sr des sédiments de rivière sont souvent considérées comme étant représentatives de celles de leurs roches sources. Elles sont donc largement utilisées pour tracer la provenance des sédiments ou pour moyenner les compositions isotopiques des lithologies drainées. L'influence des processus sédimentaires sur les compositions isotopiques de ces sédiments est cependant mal connue. L'objectif de l'étude présentée ici est de caractériser l'ampleur de la variabilité isotopique pouvant être générée par les processus de tri minéralogique au cours du transport des sédiments dans le milieu fluviatile. Pour ce faire, nous avons analysé les concentrations en éléments traces et les compositions isotopiques en Nd, Hf, Pb et Sr dans différents types de sédiments de rivière (bedload, suspended load, bank) échantillonnés à plusieurs endroits dans le système fluviatile du Ganges qui draine une partie de l'orogène Himalayenne. Nous avons également mesuré les compositions chimiques et isotopiques de nombreuses fractions minérales et granulométriques séparées de ces sédiments afin de mieux comprendre l'influence de chaque espèce minérale dans le budget isotopique total d'un sédiment de rivière. Dans le cas où les lithologies drainées sont essentiellement cristallines et sédimentaires, nous montrons que les isotopes du Nd dans les sédiments de rivière sont très peu affectés par les processus de tri minéralogique puisqu'ils sont toujours contrôlés par les mêmes minéraux, à savoir la monazite et l'allanite. Au contraire, les systèmes isotopiques de l'Hf, du Pb et du Sr s'avèrent particulièrement touchés par les processus de tri minéralogique. Les isotopes de l'Hf et du Pb sont tous deux affectés par un effet zircon qui génère de larges variations isotopiques entre les sédiments de fond de rivières et ceux transportés en suspension. Pour le Sr, les variations observées entre les différents types de sédiments résultent des proportions variables de micas et feldspath-K qu'ils contiennent. Dans le cas où les principales lithologies drainées présentent de forts contrastes d'érodabilité i.e. basaltes versus roches cristallines, nous montrons que les effets combinés de l'érosion différentielle dans le bassin de drainage et du tri sédimentaire dans la colonne d'eau sont responsables d'importantes variations isotopiques en Nd, Hf et Pb entre les sédiments de fond de rivière et ceux transportés en suspension. Nos calculs suggèrent que les produits d'érosion basaltique, relativement fins, sont préférentiellement transportés en suspension, proche de la surface de l'eau, alors que les produits d'érosion des roches plus cristallines sont préférentiellement concentrés dans les sédiments de fond de rivière. Enfin, nous suggérons que les variations isotopiques observées entre les différents types de sédiments transportés par les rivières sur les continents pourraient avoir d'importantes implications pour les systématiques isotopiques des sédiments océaniques terrigènes et sur l'évolution à long terme du réservoir mantellique si ces derniers sont recyclés au niveau des zones de subduction. / Nd, Hf, Pb and Sr isotopic compositions of river sediments are often considered to be representative of those of their source rocks. Thus, they are widely used to trace sediment provenance or to average the isotopic compositions of the drained lithologies. The influence of sedimentary processes on the isotopic composition of these sediments is however poorly known. The aim of the present study is to characterize the extent of the isotopic variability that can be generated by mineral sorting process during sediment transport in fluvial system. To do this, we analyzed trace element concentrations and Nd, Hf, Pb and Sr isotopic compositions in river bank, bedload and suspended load sampled at several locations in the Ganga fluvial system draining part of the Himalayan orogen. We also measured the chemical and isotopic compositions of numerous mineral and granulometric fractions separated from these sediments to better understand the contribution of each mineral species to the bulk isotopic budget of river sediments. When the drained lithologies are mainly crystalline and sedimentary, we show that Nd isotopes are very little affected by mineral sorting processes because, whatever the sediment type, those isotopes are always controlled by the same minerals i.e. monazite and allanite. In contrast, Hf, Pb and Sr isotopic systems are significantly affected by mineral sorting processes. Both Hf and Pb isotopes are affected by a zircon effect that generates large isotopic variations between bedload and suspended load. For Sr, variations between the different sediment types more likely result from variable proportions of K-feldspar and mica. When the main drained lithologies are characterized by strong differences in erodibility i.e. basalts versus crystalline rocks, we show that the combined effects of differential erosion in the drainage basin and sediment sorting in the water column are responsible for significant Nd, Pb and Hf isotopic variations between bedload and suspended load. Our calculations suggest that basaltic erosion products are preferentially transported in suspension, near the water surface, whereas the erosion products of more crystalline rocks are preferentially concentrated in bottom sediments. Finally, we suggest that the isotopic variations observed between bedload and suspended load on continents may have important implications for the isotopic systematics of oceanic terrigenous sediments and the long-term evolution of the mantle if these latters are recycled in subduction zones.

Durant cette thèse, nous appliquons la méthode de la corrélation de bruit ambiant dans la région particulièrement hétérogène des Pyrénées et des ses alentours (socle rocheux affleurant et bassin sédimentaires épais). Le jeu de données utilisé est une combinaison de deux réseaux temporaires large-bande français et espagnol (PYROPE et IBERARRAY) et de stations des réseaux permanents large-bande français et catalan. Le bruit sismique, enregistré pendant un an par les 158 stations est utilisé pour calculer les corrélations dans la gamme de période 5-55 s. Les vitesses de groupe de l'onde de Rayleigh et de l'onde de Love entre paires de stations sont inversées de manière linéarisée et nous obtenons, pour chaque période, des cartes de vitesses de groupe avec une résolution latérale d'environ 40 km. La comparaison entre les deux types d'ondes montre qu'il existe une anisotropie radiale à courtes périodes, alors que peu ou pas d'anisotropie radiale n'est visible aux périodes plus longues. Nous avons développé une nouvelle stratégie d'inversion des courbes de dispersion en modèle de vitesse d'onde S que nous avons appliqué sur les vitesses de groupe de l'onde de Rayleigh. Cette approche d'inversion est basée sur une exploration complète de l'espace des modèles et une inversion linéarisée. Le modèle obtenu, validé par la comparaison avec des résultats provenant d'autres méthodes, est le premier modèle 3-D crustale en vitesse d'onde S de la région et il permet d'apporter des contraintes sur la géodynamique des Pyrénées et de ses alentours. Deux points importants sont soulevés : (1) Des profils de vitesses atypiques sous l'Est du Massif Central, avec une croûte amincie et des vitesses anormalement faibles dans le manteau supérieur. (2) Deux anomalies de vitesses rapides sous la zone du Labourd-Mauléon et dans le prolongement du bassin de Parentis. Ces anomalies, situées à 25 km de profondeur, sont interprétées comme les traces de l'hyper-extension qui aurait précédée la phase de collision amenant à la formation des Pyrénées. La forte hétérogénéité de la zone permet également de faire l'analyse de l'influence de la non prise en compte des déviations de rais lors de l'inversion. Les premiers résultats montrent que le modèle obtenu en utilisant la théorie des rais droits ne permet pas d'expliquer les déviations calculées par la méthode de formation de voie. Ces déviations observées peuvent donc apporter une amélioration du modèle en considérant l'utilisation d'une inversion combinée. / In this thesis, we applied the ambient noise correlation method in the very heterogeneous region of the Pyrenees and the surrounding areas (mountain belt and thick sedimentary basins). The dataset used is a combination of two temporary broadband arrays from France and Spain (PYROPE and IBERARRAY) and stations of the French and Catalan permanent broadband arrays. Seismic noise recorded over years by the 158 stations was used to calculate correlations in a period range of 5-55 s. Observed Rayleigh and Love wave group velocities between pairs of stations were used as input to a linearized inversion scheme, where we obtained for each period group velocities maps, with a lateral resolution of approximately 40 km. The comparison between the two type of waves demonstrates radial anisotropy at short periods, while little or no radial anisotropy is present at long periods. We developed a new strategy for the inversion of dispersion curves to shear wave velocity models and applied it to the Rayleigh waves group velocity. This approach is based on the combination of a full exploration of the model space and a linearized inversion. The obtained model, validated by the comparison of our results with the results of other methods, is the first complete 3-D crustal Vs model of the region. We in particular note : (1) Atypical S-waves profiles in the Eastern part of the Massif Central which indicate a thinned crust and low velocities in the uppermost mantle. (2) High-velocity anomalies at 25 km depth beneath the Labourd-Mauléon area and the on-land continuation of the Parentis basin. We suggest that they are the traces of the hyper-extension which might have preceded the collision phase which lead to the formation of the Pyrenees. The strong heterogeneity of our study region is also well-adapted to analyze the influence of the ray deviations on the reconstruction of the model. First results show that the reconstructed model, using great-circle paths, does not explain the ray deviations as observed by beamforming. Observed deviations therefore carry the potential of improving the model in a combined inversion scheme.

Made available in DSpace on 2014-12-17T14:57:53Z (GMT). No. of bitstreams: 1 SaniaMBA_TESE.pdf: 2511848 bytes, checksum: 97413b8278096d3ff64cc7f5138841e7 (MD5) Previous issue date: 2012-04-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Chitin and chitosan are nontoxic, biodegradable and biocompatible polymers produced by renewable natural sources with applications in diverse areas such as: agriculture, textile, pharmaceutical, cosmetics and biomaterials, such as gels, films and other polymeric membranes. Both have attracted greater interest of scientists and researchers as functional polymeric materials. In this context, the objective of this study was to take advantage of the waste of shrimp (Litopenaeus vannamei and Aristeus antennatus) and crabs (Ucides cordatus) from fairs, beach huts and restaurant in Natal/RN for the extraction of chitin and chitosan for the production of membranes by electrospinning process. The extraction was made through demineralization, deproteinization, deodorization and deacetylation. Morphological analyzes (SEM and XRD), Thermal analysis (TG and DTG), Spectroscopy in the Region of the Infrared with Transformed of Fourier (FTIR) analysis Calorimetry Differential Scanning (DSC) and mechanical tests for traction were performed. In (XRD) the semicrystalline structure of chitosan can be verified while the chitin had higher crystallinity. In the thermal analysis showed a dehydration process followed by decomposition, with similar behavior of carbonized material. Chitosan showed temperature of maximum degradation lower than chitin. In the analysis by Differential Scanning Calorimetry (DSC) the curves were coherent to the thermal events of the chitosan membranes. The results obtained with (DD) for chitosan extracted from Litopenaeus vannamei and Aristeus antennatus shrimp were (80.36 and 71.00%) and Ucides cordatus crabs was 74.65%. It can be observed that, with 70:30 solutions (v/v) (TFA/DCM), 60 and 90% CH3COOH, occurred better facilitate the formation of membranes, while 100:00 (v/v) (TFA/DCM) had formation of agglomerates. In relation to the monofilaments diameters of the chitosan membranes, it was noted that the capillary-collector distance of 10 cm and tensions of 25 and 30 kV contributed to the reduction of the diameters of membranes. It was found that the Young s modulus decreases with increasing concentration of chitosan in the membranes. 90% CH3COOH contributed to the increase in the deformation resulting in more flexible material. The membranes with 5% chitosan 70:30 (v/v) (TFA/DCM) had higher tensile strength / Quitina e quitosana s?o pol?meros at?xicos, biodegrad?veis e biocompat?veis produzidos por fontes naturais renov?veis com aplica??es em diversas ?reas como: agricultura, t?xtil, farmac?utica, cosm?ticos e biomateriais, tais como g?is, filmes, membranas polim?ricas entre outros. Ambas t?m despertando grande interesse de cientistas e pesquisadores como materiais polim?ricos funcionais. Nesse contexto, o objetivo do presente trabalho foi aproveitar os res?duos de camar?es (Litopenaeus vannamei e Aristeus antennatus) e de caranguejos (Ucides cordatus) proveniente de feiras, barracas de praia e restaurantes em Natal/RN para extra??o de quitina, quitosana e produ??o de membranas pelo processo de eletrofia??o. A extra??o foi realizada a partir das etapas de desmineraliza??o, desproteiniza??o, desodoriza??o e desacetila??o. An?lises morfol?gicas (MEV e DRX), an?lises das propriedades t?rmicas (TG e DTG), an?lise por Espectroscopia na Regi?o do Infravermelho com Transformada de Fourier (FTIR), an?lise de Calorimetria Explorat?ria Diferencial (DSC) e ensaios mec?nicos por tra??o foram realizados. Na an?lise de DRX pode-se verificar a estrutura semicristalina da quitosana enquanto a quitina teve alta cristalinidade. As an?lises t?rmicas demonstraram um processo de desidrata??o seguido da decomposi??o com comportamento similar de material carbonizado. A quitosana apresentou temperaturas de m?xima degrada??o mais baixas do que a quitina. Na an?lise por Calorimetria Explorat?ria Diferencial (DSC) as curvas foram coerentes aos eventos t?rmicos das membranas de quitosana. Os resultados obtidos com (GD) para quitosana extra?da de camar?es Litopenaeus vannamei e Aristeus antennatus foram (80,36 e 71,00%) e caranguejos Ucides cordatus foi 74,65%. Pode-se perceber que, com solu??es 70:30 (v/v) (TFA/DCM), 60 e 90% CH3COOH, ocorreu melhor facilita??o na forma??o das membranas, enquanto em 100:00 (v/v) (TFA/DCM) houve forma??o de aglomerados. Em rela??o aos di?metros dos nanofilamentos das membranas de quitosana, percebeu-se que a dist?ncia capilar-coletor de 10 cm e tens?es de 25 e 30 kV contribu?ram para a redu??o dos di?metros das membranas. Quanto ao m?dulo de Young diminui com o aumento da concentra??o da quitosana nas membranas. 90% CH3COOH contribuiu para o aumento da deforma??o, sendo um material mais flex?vel. As membranas com 5% quitosana 70:30 (v/v) (TFA/DCM) apresentaram maior valor de resist?ncia ? tra??o

Le nettoyage laser Nd:YAG Q-switched (1064 nm) confère souvent aux surfaces nettoyées un aspect plus jaune que les autres techniques de nettoyage. Cet effet jaune peut conduire à l’obtention de contrastes de couleur inesthétiques si différentes techniques de nettoyage sont utilisées sur un même ensemble architectural, comme c’est le cas par exemple pour le portail des Valois de la basilique Saint-Denis près de Paris. Une des hypothèses émises pour expliquer le phénomène est que le jaunissement laser serait lié à la présence de résidus d’irradiation nanométriques formés par interaction du faisceau laser avec la salissure, en particulier les croûtes noires gypseuses communément observées sur les monuments en pierre. Dans le cadre de cette thèse, une méthodologie analytique multi-échelle allant jusqu’à l’échelle nanométrique a été développée pour observer et caractériser les composés néoformés responsables de la coloration jaune. Des éprouvettes de croûtes modèles à base d’hématite et de croûtes reconstituées à partir de croûte noire naturelle ont été élaborées. La croûte noire naturelle a été caractérisée pour déterminer les composés susceptibles de réagir au faisceau laser et donc de contribuer au jaunissement. Des oxydes de fer (hématite, magnétite, maghémite) et des cendres volantes silico-alumineuses issues de la combustion du charbon ont ainsi pu être mis en évidence. La nature chimique et structurale des produits de l’irradiation laser des éprouvettes a ensuite été examinée à l’aide d’un panel de techniques incluant entre autres la microscopie électronique à transmission (MET) couplée à la diffraction électronique et aux spectroscopies de rayons X par dispersion d’énergie (EDX) et de perte d’énergie des électrons (EELS). Des nanostructures cristallisées sous forme de nano-sphères et de nano-résidus ont ainsi pu être observées. La caractérisation de la composition chimique à l’échelle nanométrique a permis de révéler la présence de fer dans toutes les nanostructures. Une étude approfondie de la couleur a en outre permis de relier les propriétés colorimétriques du processus de jaunissement à la nature des nano-composés néoformés par irradiation laser. D’autre part, le portail des Valois de la basilique Saint-Denis a été le sujet d’une étude de cas qui est venue complémenter la recherche tout en ancrant l’étude dans la réalité du monde de la conservation des monuments historiques. Enfin des essais de remédiation ont démontré les potentialités de l’utilisation d’un rayonnement UV pour atténuer ou ne pas produire de jaunissement. In fine, ce travail a permis de démontrer que le phénomène de jaunissement laser observé à l’échelle macroscopique est intimement lié à des transformations de matière à l‘échelle nanométrique, induites par l’interaction du rayonnement laser avec les oxydes de fer et les cendres volantes présents dans les encrassements. / Nd:YAG Q-Switched laser cleaning of soiled stone at 1064 nm can sometimes result in yellower appearances than other conventional cleaning techniques. This yellowing effect can lead to unsightly colour contrasts if different cleaning techniques are used on the same architectural complex, as is the case for the Valois Portal of the Saint-Denis basilica near Paris. One argument made to explain the phenomenon is that the laser yellowing is linked to the creation of nano-sized irradiation residues through the laser beam interaction with soiling matter such as black gypseous crusts. In this study, a multi-scale analytical method extending to the nanoscale has been used to observe and characterize the neo-formed compounds accountable for the yellow discoloration. Samples of model crusts containing hematite and reconstituted crusts prepared with natural black crust have been synthetized. The natural black crust has been characterized in order to identify the compounds that may react under the laser beam and thus contribute to the yellowing effect. Iron oxides (hematite, magnetite and maghemite) and aluminosilicate fly-ashes originating from coal combustion have been discovered. The chemical and structural nature of irradiation products has then been investigated by several techniques including in particular transmission electron microscopy (TEM) coupled with electronic diffraction and energy-dispersive X-ray (EDX) and electron energy-loss (EELS) spectroscopies. Iron containing nanostructures crystallized in the form of nano-spheres and nano-residues have been evidenced and characterized. By studying thoroughly the colour, the colorimetric properties of the yellowing process have been linked to the nature of the neo-formed compounds. Furthermore a case study on the Valois Portal has completed the research while setting it within the reality of the conservation world. Finally experiments with UV light have shown the promising potentiality of this tool as a remedy to the yellowing effect. In summary, this study has demonstrated that the yellowing phenomenon observed at the macroscale is intimately linked to matter transformations occurring at the nanoscale, induced by the interaction between the laser beam and the iron oxides and fly-ashes found in black crusts.

D’importantes découvertes de gaz ont été faites récemment en Méditerranée orientale (www.nobleenergyinc.com), incitant les compagnies pétrolières à s’intéresser de plus près au bassin du Levant, considéré aujourd’hui comme une véritable province pétrolière. Par conséquent, une quantité considérable de données géophysiques a été produite et une série d'études académiques et industrielles ont été réalisées. La compréhension de l’architecture crustale et sédimentaire associée à celle de la thermicité actuelle et passée des marges de ce bassin, notamment la marge continentale du Liban, présente des enjeux industriels et scientifiques majeurs. Cette question a des implications majeures pour l'évolution tectonique, les prévisions des tremblements de terre ainsi que celle des systèmes pétroliers. Malgré les différents travaux géophysiques menés sur la Méditerranée orientale ces dernières années, la configuration crustale profonde du bassin du Levant, connu pour avoir été le siège d’un rifting à la fin du Paléozoïque et au début du Mésozoïque, reste imprécise. La transition d’une croûte continentale épaisse vers une croûte atténuée en mer (peut-être même une croûte océanique) a été invoquée, mais pas encore prouvée. Des approches géophysiques intégrées ainsi qu’un travail de modélisation ont été utilisés dans cette thèse pour étudier la structure profonde de la lithosphère sous la région Est de la Méditerranée.Une modélisation crustale 2D à l’échelle régionale (du delta du Nil au sud à la Turquie au nord, et du bassin Hérodote à l’ouest à la plaque arabe à l’est) a été effectuée dans le but d’étudier l’architecture de la croûte dans cette partie de la méditerranée orientale. L’algorithme utilisé est une méthode d’essai-erreur qui fournit l’épaisseur crustale et la profondeur de la limite lithosphère- asthénosphère (LAB) ainsi que la distribution de la densité crustale par l’intégration du flux de chaleur surfacique, l’anomalie gravimétrique à l’air libre, les données du géoïde et la topographie. La profondeur du Moho et l’épaisseur de la croûte ont été contraintes localement par des données de sismique réfraction là où elles sont disponibles. Les résultats montrent une croûte cristalline progressivement atténuée dans une direction EW. Dans le bassin du Levant, la croûte est interprétée comme continentale et composée de deux croûtes distinctes, une supérieure et une inférieure, contrairement au bassin Hérodote qui repose sur une croûte mince, probablement océanique.Une inversion 3D jointe des données de gravité, du géoïde et de la topographie appliquée sur la même région a confirmé les résultats de la modélisation crustale 2D. A total of 168 simulations ont été réalisées, parmi lesquelles, la simulation avec les erreurs les moins grandes sur les données correspond à l’inversion d’un modèle dans lequel la profondeur du Moho varie entre 23 et 26 km dans le bassin du Levant et devient plus profond dans le bassin Hérodote et aux larges des côtes africaines. La profondeur de la LAB est située entre 100 et 150 km dans le bassin du Levant et atteint plus de 180 km dans le bassin Hérodotes. L’interprétation de cinq lignes de sismique réflexion 2D PSTM à 14 s TWT couvrant la partie nord du bassin du Levant a révélé un total de 10 horizons, dont le plus profond pourrait être une interface croûte-manteau. L’interprétation des paquets sismiques, leurs surfaces de raccord ainsi que l’analyse des facies ont été contraints par les interprétations sismiques 2D publiées de la partie nord de l’offshore Libanais (Hawie et al., 2013b), dans lesquelles les connaissances stratigraphiques et sédimentologiques récentes de la marge libanaise ont été extrapolées jusqu’au bassin. Un total de huit paquets sédimentaires a été identifié dans le bassin aux âges variant du Jurassique Moyen au Quaternaire. / Significant gas discoveries have been made recently in the Eastern Mediterranean (www.nobleenergyinc.com), which turned the attention of oil companies towards the Levant Basin. This region is considered today as a typical hydrocarbon frontier province. Hence, a considerable amount of geophysical data has been produced and a series of academic and industry-based studies have been performed. Understanding the crustal and sedimentary architecture, the actual and past thermicity of this basin, in particular on the Lebanese continental margin, has major academic and economic interests. This has important implications on understanding tectonic evolution and earthquakes generation and on assessing petroleum systems. Despite numerous old and recent geophysical studies in this region, the deep crustal configuration of the Levant Basin, known to be the site of rifting in the Late Paleozoic and Early Mesozoic, remains enigmatic. The transition from a typical thick continental crust to thinner attenuated crust offshore (possibly even oceanic crust) has been invoked, but not yet proven. Integrated geophysical approaches and modeling techniques are used in this thesis to study the deep structure of the lithosphere underlying the easternmost Mediterranean region.A 2D modeling approach was accomplished at a regional scale (1000x1000 km2) extending from the Nile delta in the south, to Turkey in the north, from the Herodotus Basin in the west to the Arabian plate in the east. The algorithm used is a trial and error method that delivers the crustal thickness and the depth of the lithosphere-asthenosphere boundary (LAB) as well as the crustal density distribution by integrating top basement heat flow data, free-air gravity anomaly, Geoid and topography data. Moho depth and crustal thickness were locally constrained by refraction data where available. Three models are presented, two in EW direction (580 and 650 km long) and one in SN direction (570 km long). The models in EW sections show a progressively attenuated crystalline crust from E to W (35 to 8 km). The SN section presents a 12 km thick crust to the south, thinning to 9-7 km towards the Lebanese offshore and reaching 20 km in the north. The crystalline crust is best interpreted as a strongly thinned continental crust under the Levant Basin, represented by two distinct components, an upper and a lower crust. The Herodotus Basin, however, shows a very thin crystalline crust, likely oceanic, with a thickness between 6 and 10 km. The Moho under the Arabian plate is 35-40 km deep and becomes shallower towards the Mediterranean coast. Within the Levant Basin, the Moho appears to be situated between 20 and 23 km, reaching 26 km in the Herodotus Basin. While depth to LAB is around 110 km under the Arabian and the Eurasian plates, it is about 150 km under the Levant Basin and plunges finally to 180 km under the Herodotus Basin.A 3D joint inversion of gravity, geoid and topography data applied on the same region confirmed the results of the 2D modeling. A total of 168 of simulations were run, among which the simulation with the minimal data misfits corresponds to a model where the Moho depth varies between 23 and 26 km in the Levant Basin and becomes deeper in the Herodotus Basin and off the African coast. The LAB is 100 to 150 km deep in the Levant Basin and deepens to more than 180 km in the Herodotus Basin.

La localisation de la déformation est une caractéristique nécessaire de la tectonique. Pour localiser la déformation, une roche doit subir un affaiblissement. Le processus affaiblissant principal des roches est l'interconnexion de phases faibles. Dans le cas de la croûte continentale, les phases faibles étant le plus souvent responsables de la localisation sont les micas et les liquides silicatés résultant de la fusion partielle. Bien qu'il existe des études expérimentales sur la rhéologie des micas, il y a très peu d'études sur l'impact des micas sur la localisation dans les conditions de la croûte continentale inférieure. De même, les précédentes études expérimentales montrent l'effet de la fusion partielle sur la résistance des roches mais elles utilisent toutes un matériel de départ isotrope. Or la croûte subissant la fusion partielle dans les orogènes est susceptible d'être préalablement déformée et donc anisotrope. Dans le but d'apporter de nouvelles données sur le comportement mécanique et les microstructures de la croûte continentale anisotrope, ainsi que sur l'effet des micas sur la localisation de la déformation, cette thèse propose de réaliser une série d’expériences en presse de Griggs. Cette approche expérimentale est aussi couplée à un travail de terrain sur la zone de faille de Møre og Trøndelag (Norvège). Cette structure étant un zone de cisaillement d'échelle crustale dont la cinématique est partiellement synchrone de la fusion partielle, elle est adaptée à l'étude naturelle des relations entre fusion partielle et déformation. / Strain localization is a necessary feature of tectonic. To be able to localize deformation, rocks must undergo weakening. The main weakening process is weak phase interconnection. For continental crust, weak phases that are the most often responsible of strain localization are micas and melt. Although previous experimental studies exist about rheological properties of micas, none are about the effect of micas on the strain localization in the lower continental crust conditions. Previous experimental studies about the effect of partial melting were always done with isotropic starting material. But continental crust which undergo partial melting is very likely to be deformed before melting and therefore to be highly anisotropic. In the aim to bring new data about mechanical behavior and microstructures of anisotropic continental crust, as well as the effect of micas on strain localization, this thesis propose to conduct a series of experiments in a Griggs apparatus. This experimental approach is also coupled with field work on the Møre og Trøndelag Fault Zone (Norway). This crustal scale shear zone was partially synchronous with partial melting and therefore is well suited for studying relation ship between deformation and partial melting

The distribution and geologic history of nitrogen on Earth is poorly known. Traditionally thought to be an inert gas, with only a small but important biologic cycle, geochemical investigation highlights that it can also be present in rocks and minerals. Even at low concentrations, the great mass of the solid Earth allows for the possibility of substantial N mass and cycling in the geosphere over Earth history. Thus, the assumption that N on the surface of the Earth has remained in steady state over Earth history can be questioned. The research goals of this thesis are to investigate the Earth System N cycle using both large- and small-scale approaches. I present a comprehensive literature compilation to ascertain the N budget of Earth. Determining the total abundance of N in all reservoirs of the Earth, including the atmosphere, oceans, crust, mantle, and core is crucial to a discussion of its cycling in the past. This budget study suggests that the majority of planetary N is likely in the core, with the Bulk Silicate Earth a more massive reservoir than the atmosphere. I also present experimental data and data from lunar samples as added context. As quantification of geologic N is difficult, I present research detailing the adaptation of a fluorometric technique common in aquatic geochemistry for use on geologic samples. I compare fluorometry analysis of geochemical standards to several other techniques: colourimetry, elemental analyzer mass spectrometry, and neutron activation analysis. Fluorometry generally behaves well for crystalline samples, and is a relatively quick and easy alternative to more expensive or intensive techniques. As a preliminary application, I have determined a N budget estimate for the continental crust based on analysis of crystalline crustal rocks and glacial tills from North America. This budget is consistent with published work, suggesting about 2 × 1018 kg N, or half a present atmospheric mass of N, is in the continental crust. I also present a geochemical study measuring N-isotopes and redox sensitive trace elements from a syn-glacial unit deposited during the the Marinoan Snowball Earth. Snowball Earth events were the most extreme glaciations in Earth history. The measurements presented herein are the first to quantify biologic activity via N-isotopes as well as the redox state of the atmosphere and ocean using trace elements from this intriguing time period in Earth history. The data suggests that there was active N- fixing in the biosphere, persistent but limited O2, nitrification, and nearly quantitative denitrification during the glaciation. After the glacial interval, O2 levels increased and denitrification levels dropped, indicated by near-modern δ15N values. The combined use of N-isotope with redox sensitive trace elements provides a more nuanced and comprehensive view in reconstructing past ocean and biologic conditions. Lastly, I present an Earth-system N cycle model with nominal results. Previous modelling efforts have agreed with the traditional notion that atmospheric N-levels have remained constant over geologic time. This is in contrast with modern geochemical evidence suggesting net transport of N from the surface into the mantle. The aim, in turn, of this model is to model N cycling over Earth history by explicitly incorporating both biologic and geologic fluxes. The model is driven by a mantle cooling history and calculated plate tectonic speed, as well as a prescribed atmospheric O2 evolution history. This approach is the first of its kind, to my knowledge, and produces stable model runs over Earth history. While tuning and sensitivity studies may be required for publishable results, nominal runs are compelling. In model output, atmospheric N varies by an factor of 2 − 3 over Earth history, and the availability of nutrients (i.e., PO4) exerts a strong control on biologic activity and movement of N throughout the Earth system. Such a planetary perspective on N serves as an entry point into discussions of planetary evolution as a whole. With the great increase in the number of discovered exoplanets, the scientific community is charged with developing models of planetary evolution and factors that promote habitability. Comparison of Earth to its solar system neighbours and future data on exoplanets will allow a system of evolution pathways to be explored, with the role of N expected to be prominent in discussions of habitability and planetary evolution. / Graduate / 0996 / 0425 / bwjohnso@uvic.ca

Magma plumbing systems represent the physical framework of magma transport and storage from the source region in the mantle, through the crust, until reaching the surface in a volcanic eruption. Characterising the different aspects of magma plumbing, in particular the distribution of magma storage zones throughout the crust, is of key importance to better understand the behaviour of individual volcanoes. In particular, shallow crustal magma storage and associated magma-crust interaction processes could potentially explain some of the worlds most unpredictable and explosive volcanoes. This thesis studies magma plumbing architecture in the Sunda Arc (Indonesia), and the North Atlantic Igneous Province, based on elemental and isotope geochemistry, and derived petrological modelling. In this study, I have employed petrological models, so called geothermobarometers, to calculate pressures and temperatures (P-T) of crustal magma storage. Geothermobarometers are calibrated thermodynamic formulations based on the composition of magmatic minerals and their co-existing melt as a function of the P-T conditions of crystallisation. Using the calculated P-T estimates, I was able to derive the depth of magma storage, and thereby reconstruct the architecture of magma storage systems. A number of different geothermobarometers based on different mineral phases, including plagioclase, clinopyroxene and olivine, were used for this purpose, The geothermobarometric modelling was combined with additional elemental and isotope geochemical analyses, as well as collaborations with geophysical investigations. These additional approaches were used to corroborate the findings of the geothermobarometric modelling, and also to model and quantify magma-crust interaction processes that take place during crustal magma storage, such as assimilation of crustal lithologies into the magmatic system. The findings of this thesis build upon the growing body of evidence in support of the prevalence of shallow magma storage in different volcanic settings worldwide. This realisation is relevant to volcano monitoring and hazard mitigation worldwide.