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The Bella Coola area geographically straddles two zones of known Early to mid-Cretaceous sinistral ductile strain; the Grenville, Kitkatla, and Principe-Laredo shear zones to the northwest located near Prince Rupert, B.C., and the Tchaikazan fault system to the southeast. At the latitude of Bella Coola in west-central B.C., the Pootlass High Strain Zone (PHSZ) is a ductile, subvertical, shear zone system at least 2 km wide and at least 30 km long. The purpose of this study is to determine the age, kinematics, and tectonic significance of the PHSZ, and to investigate whether or not it was active as a kinematic link to Early to mid-Cretaceous sinistral ductile strain zones in the western Canadian Cordillera. This thesis reports recent observations from field mapping and new geochronological, microstructural, and petrological data, from which the PHSZ is characterized and placed into a regional tectonic framework. U-Pb and 40Ar/39Ar isotopic geochronology indicate that regionally extensive, southwest-vergent folding in the PHSZ area was active prior to 114 Ma and persisted until at least 73 Ma. High-temperature, ductile, sinistral non-coaxial strain in the PHSZ was accommodated between 76 (or earlier) and 62 Ma. Localization of high strain is associated with the emplacement of plutonic rock and abundant intrusive sills, which likely acted as a strain-softening mechanism. L-tectonites within the deformed plutonic rocks attest to the weakness of the rocks during deformation and support syn-kinematic magmatism. Geothermometric and petrological data suggest that deformation occurred at temperatures of 537 to 731°C and at crustal depths of —23 km. The PHSZ is interpreted to be kinematically related to the Talchako Fault to the east, which was active as a sinistral mylonitic shear zone between 70 and 65 Ma. A kinematic relationship between the PHSZ and the Grenville, Kitkatla and Principe-Laredo shear zones near Prince Rupert imply a protracted history of sinistral transpression in the Coast Mountains of British Columbia that persisted in the Bella Coola region through Late Cretaceous time.

The Bella Coola area geographically straddles two zones of known Early to mid-Cretaceous sinistral ductile strain; the Grenville, Kitkatla, and Principe-Laredo shear zones to the northwest located near Prince Rupert, B.C., and the Tchaikazan fault system to the southeast. At the latitude of Bella Coola in west-central B.C., the Pootlass High Strain Zone (PHSZ) is a ductile, subvertical, shear zone system at least 2 km wide and at least 30 km long. The purpose of this study is to determine the age, kinematics, and tectonic significance of the PHSZ, and to investigate whether or not it was active as a kinematic link to Early to mid-Cretaceous sinistral ductile strain zones in the western Canadian Cordillera. This thesis reports recent observations from field mapping and new geochronological, microstructural, and petrological data, from which the PHSZ is characterized and placed into a regional tectonic framework. U-Pb and 40Ar/39Ar isotopic geochronology indicate that regionally extensive, southwest-vergent folding in the PHSZ area was active prior to 114 Ma and persisted until at least 73 Ma. High-temperature, ductile, sinistral non-coaxial strain in the PHSZ was accommodated between 76 (or earlier) and 62 Ma. Localization of high strain is associated with the emplacement of plutonic rock and abundant intrusive sills, which likely acted as a strain-softening mechanism. L-tectonites within the deformed plutonic rocks attest to the weakness of the rocks during deformation and support syn-kinematic magmatism. Geothermometric and petrological data suggest that deformation occurred at temperatures of 537 to 731°C and at crustal depths of —23 km. The PHSZ is interpreted to be kinematically related to the Talchako Fault to the east, which was active as a sinistral mylonitic shear zone between 70 and 65 Ma. A kinematic relationship between the PHSZ and the Grenville, Kitkatla and Principe-Laredo shear zones near Prince Rupert imply a protracted history of sinistral transpression in the Coast Mountains of British Columbia that persisted in the Bella Coola region through Late Cretaceous time.

The Bella Coola area geographically straddles two zones of known Early to mid-Cretaceous sinistral ductile strain; the Grenville, Kitkatla, and Principe-Laredo shear zones to the northwest located near Prince Rupert, B.C., and the Tchaikazan fault system to the southeast. At the latitude of Bella Coola in west-central B.C., the Pootlass High Strain Zone (PHSZ) is a ductile, subvertical, shear zone system at least 2 km wide and at least 30 km long. The purpose of this study is to determine the age, kinematics, and tectonic significance of the PHSZ, and to investigate whether or not it was active as a kinematic link to Early to mid-Cretaceous sinistral ductile strain zones in the western Canadian Cordillera. This thesis reports recent observations from field mapping and new geochronological, microstructural, and petrological data, from which the PHSZ is characterized and placed into a regional tectonic framework. U-Pb and 40Ar/39Ar isotopic geochronology indicate that regionally extensive, southwest-vergent folding in the PHSZ area was active prior to 114 Ma and persisted until at least 73 Ma. High-temperature, ductile, sinistral non-coaxial strain in the PHSZ was accommodated between 76 (or earlier) and 62 Ma. Localization of high strain is associated with the emplacement of plutonic rock and abundant intrusive sills, which likely acted as a strain-softening mechanism. L-tectonites within the deformed plutonic rocks attest to the weakness of the rocks during deformation and support syn-kinematic magmatism. Geothermometric and petrological data suggest that deformation occurred at temperatures of 537 to 731°C and at crustal depths of —23 km. The PHSZ is interpreted to be kinematically related to the Talchako Fault to the east, which was active as a sinistral mylonitic shear zone between 70 and 65 Ma. A kinematic relationship between the PHSZ and the Grenville, Kitkatla and Principe-Laredo shear zones near Prince Rupert imply a protracted history of sinistral transpression in the Coast Mountains of British Columbia that persisted in the Bella Coola region through Late Cretaceous time. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Archean North Caribou greenstone belt (NCGB) possesses abundant transpressive deformation zones on its northern margins, which appear to have formed under amphibolite facies conditions. Protracted deformation and regional metamorphism are coeval with widespread magmatism and accretion events in the Superior Province, yet the importance of these shear zones in the tectonic evolution of the NCGB is equivocal. Structural analyses support a transpressive system that strongly implicates horizontal tectonism. This is partly in contrast with some currently proposed models for Archean greenstone belts suggesting synchronous vertical and horizontal movements. Geochemical and microstructural analyses from shear zones indicate heterogeneous deformation/fluids conditions on a km-scale. Monazite and mica geochronological ages indicate metamorphism and deformation occurring during the amalgamation of the Superior craton from ca. 2.75 to 2.4 Ga. The high metamorphic grade background may obscure tectonic signatures, yet some structural and geochemical characteristics remain consistent with other greenstone belts where vertical and horizontal displacement are recorded.

The White Mountain shear zone (WMSZ) is a zone of intense penetrative deformation that lies along the western front of the northern White-Inyo Range in eastern-most California and western-most Nevada. The northern half of the WMSZ is characterized by a NNE to NNW-striking steeply dipping foliation and associated shallowly plunging NNE to NW-trending stretching lineations. S-C fabrics observed in outcrop, microstructural shear sense indicators and kilometer-scale foliation geometry all indicate dextral movement. Localized discrete zones of coeval steeply plunging stretching lineations are present in the northern half of the WMSZ. Microstructural data from these domains indicate a high component of pure shear within a separate coeval kinematic framework and hence a transpressional history. The WMSZ appears to be tectonically related to both the Sierra Crest shear system to the west and the Santa Rita shear system to the south. Correlation between the WMSZ and the Santa Rita shear system indicates that Late Cretaceous dextral transpression may extend up to ~120 km along the western front of the White-Inyo Range. Cross-cutting relationships with Late Cretaceous plutons bracket the age of the WMSZ at between 72-92 Ma. A lack of annealing recrystallization in deformed quartz and the presence of high temperature crystallographic fabrics near the margins of the ca. 72 Ma Boundary Peak pluton indicate significant strain accumulation within the WMSZ subsequent to emplacement of the Boundary Peak pluton. These observations extend the duration of Late Cretaceous dextral transpression in eastern California to at least as recent as 72 Ma. / Master of Science

Deformation in southern Alaska is controlled by the accretion and partial subduction of the Yakutat terrane as margin-parallel motion transitions to subduction. Recent studies have shown that deformation in the St. Elias orogen, at the northern end of the terrane, accommodates a large portion of convergence, but deformation at the eastern and southern margins remains more poorly constrained. Rapid recent sedimentation (> 1cm/yr) and glacio-isostatic uplift rates (> 3 cm/yr) in the Fairweather corridor highlight short-term vertical deformation at the eastern margin; however, the relationship between these rates and long-term deformation is less well known. New low-temperature cooling ages are reported along the eastern flank of the St. Elias orogen, placing constraints on vertical deformation over the past few million years. Young cooling ages (< 3 Ma) occur in a broad zone, extending along the onshore length of the strike-slip Fairweather fault. These ages indicate that protracted convergence has been accommodated in the Fairweather corridor. Average (~1 mm/yr) and peak (~3 mm/yr) late Cenozoic exhumation rates are similar to rates to the north, and suggest that the orogen is actually boomerang-shaped in map view. If ~1 mm/yr exhumation has been steady, the onset of rapid exhumation is constrained to post-12 Ma, but likely occurred at 5 Ma with changes in climate and plate obliquity. Although cooling ages reveal no coherent regional pattern relative to known structures, they indicate the margin accommodates a significant component of pure shear and is slip-partitioned. The resolved magnitude of convergence in the Fairweather corridor also indicates that Yakutat terrane motion is rotated from Pacific plate motion, and likely requires significant slip on the Transition fault at the southern edge of the Yakutat terrane. Although million-year exhumation rates are rapid, they are slower than short-term rates related to deglaciation. / Master of Science

Le bassin de Levant, localisé à l’extrémité la plus orientale de la Méditerranée, se situe à jonction de trois plaques tectoniques majeures (Afrique, Arabie, Eurasie ainsi que la microplaque Anatolienne). Il est bordé à l’Est par la faille du Levant (frontière Arabie/Afrique), qui représente un système transformant de 1000 km de long, reliant le rift dans la Mer Rouge au sud avec la zone de convergence le long du Taurus au nord (frontière Arabie/Eurasie). Son extrémité nord est marquée par la frontière convergente Afrique/Anatolie soulignée par l’arc de Chypre. Le bassin Levantin a enregistré l’interaction entre ces différentes plaques au cours du Cénozoïque et sa bordure Est a été en particulier déformée par la mise en place de la faille du Levant. Cette limite de plaque majeure est marquée au Liban par un relais compressif qui a été actif depuis la fin du Miocène. Jusque récemment, l’absence de données sismiques dans la partie centrale du bassin levantin (offshore Liban) a constitué un handicap important dans la caractérisation de ce basin. Dans ce secteur, la géométrie, cinématique, l’âge des structures tectoniques ne sont pas connus. Plusieurs questions en découlent. Quel est impact de la frontière transformante du Levant sur la structure du bassin? Le bassin a-t-il enregistré d’autres déformations au cours du Cénozoïque ? Quel est l’effet de la structuration ancienne et profonde de la marge sur la déformation actuelle ? Ce travail s’est appuyé sur l’interprétation des données sismiques 2D et 3D de haute qualité dont deux cubes 3D de 4290 m3 et sept lignes 2D de 830 km de long. Cette étude a permis d’identifier les structures tectoniques affectant le secteur offshore Libanais et de caractériser leurs origines. Plusieurs familles de failles tout au long de la marge Est du bassin ont été identifiées et témoigne d’une histoire tectonique méso-cénozoïque longue et complexe. Les structures reconnues sont tout d’abord (1) des failles chevauchantes NNE-SSW actives depuis le début du Tertiaire jusqu’à la fin Miocène, (2) des anticlinaux NNE-SSW formés durant le Miocène supérieur et se localisant sur des structures préexistantes et (3) des failles décrochantes dextres, héritées des structures mésozoïques et réactivées durant le Miocène supérieur. Seules les failles décrochantes dextres montrent des preuves d’une activité actuelle, liée à la transpression au long de la faille du Levant. Ces structures constituent le prolongement vers l’ouest de la frontière de plaque du Levant sous un régime transpressif et une compression NW-SE. Nous mettons en évidence que cette frontière de plaque montre une évolution au cours du Néogène avec une forte décroissance de la composante de raccourcissement à partir du Pliocène. La mise en évidence de jeux plus anciens témoigne d’une structuration profonde E-W de la marge, vraisemblablement héritée des tectoniques mésozoïques. L’impact de cette structuration a été évalué à travers une modélisation analogique. Les résultats démontrent le rôle considérable de cet héritage sur l’évolution du relais compressif de la faille du Levant au Liban, entre autre en localisant la déformation le long de couloirs E-W et en segmentant les structures transpressives NNE-SSW. Ces résultats nous conduisent à interpréter les structures E-W comme majeures et traduisant la prolongation vers l’ouest du bassin mésozoïque des Palmyrides. Nous mettons ici en évidence le rôle majeure d’une marge sur la structure d’une frontière de plaques transformante. Le développement de failles antithétiques (failles dextres dans une frontière transformante senestre), connus dans d’autres frontières de ce type, est ici clairement associé à une anisotropie profonde forçant la localisation de la déformation. / The Levant Basin is located at the easternmost Mediterranean at the intersection of three major tectonic plates (Africa, Arabia, Eurasia and the smaller Anatolian microplate). The Levant Fracture System (Arabia-Africa plate boundary) borders the basin to its east and represents a 1000 km long left-lateral transform system linking rifting in the Red Sea with plate convergence along the Taurus Mountains (Arabia-Eurasia plate boundary). The Levant Basin is bordered to the north by the Cyprus Arc (Africa-Eurasia plate boundary). The interaction between these tectonic plates had important consequences on the evolution of the Levant Basin whereby its eastern boundary has been affected by deformation along the Levant Fracture System. This major plate boundary is associated with a restraining bend in Lebanon and has been active since the Late Miocene. Until recent days, the absence of seismic data in the central Levant Basin was an obstacle against characterizing the tectonic setting of the basin. In this area, the geometry, kinematics and the age of the tectonic structures are poorly understood. A focal question thus remains on how the Levant Basin was affected by this adjacent plate boundary. Therefore, what is the impact of the deformation along the Levant Fracture System since the Late Miocene on this basin and how can we assess it? Has the latter been affected by other tectonic regimes prior to the onset of transpression? If so, how would the existing structures influence the style of modern deformation? In this study, high quality 2D and 3D seismic reflection data (with two 4290 m3 3D seismic cubes and seven 830 km long 2D seismic lines) were interpreted allowing identification and timing of the structures in the Levant Basin offshore Lebanon. Several fault families, mapped along the margin, are remnants of a lasting and complex tectonic history since Mesozoic times. These include NNE-SSW striking thrust faults active during the early Tertiary and inactive since the Pliocene; NNE-SSW striking anticlines folded during the Late Miocene and overlying pre-existing structuresd; and ENE-WSW striking dextral strike-slip faults inherited from Mesozoic times and reactivated during the Late Miocene. Only the dextral strike-slip faults show evidence of current activity and are interpreted to be linked to transpression along the Levant Fracture System. They constitute the westward extension of the plate boundary, formed under a transpressif regime and a NW-SE compression. We have showed how this plate boundary has evolved through the Neogene with a decrease in the shortening component during the Pliocene.The identification of pre-existing structures along the eastern Levant margin shed the light on the deep structuration affecting this area, inherited from Mesozoic tectonic events. The impact of these structures was tested through analogue modeling. Results indicated a considerable impact of pre-existing structures on the development of the restraining bend, localizing deformation at the onset of transpression and responsible of segmenting the restraining bend along an ENE direction. These ENE-WSW faults are thus major and are most likely associated with the deformation affecting the Palmyra basin since the Mesozoic, which is thus extending westward to Lebanon. This study has shown the important role of a margin on a strike-slip plate boundary. Namely, the development of antithetic faults (local dextral strike-slip faults in a regional sinistral strike-slip plate boundary) known in other similar plate boundaries is associated with a deep crustal anisotropy localizing the subsequent deformation.

La frontière de plaque transpressive Nord Caraïbe s'exprime dans la région d'Haïti par un partitionnement de la déformation entre deux failles décrochantes et des chevauchements. L'étude de données de bathymétrie, de sismique réflexion, et de fonctions récepteur apporte des contraintes sur la structure et le fonctionnement de cette frontière de plaque en transpression en mer et à terre. Les données de bathymétrie des campagnes Haïti-SIS 1 et 2 nous ont permis de cartographier précisément le grand système de failles décrochantes senestres et leur segmentation. L'étude des profils de sismique réflexion a mis en évidence l'existence de structures pré-existantes à l'activité du décrochement EPGFZ en mer. Nous avons également identifié un domaine crustal distinct, que nous avons relié au plateau océanique Caribéen. L'étude des déformations actuelles en mer nous permet de montrer que la faille EPGFZ est principalement décrochante, avec une composante compressive qui augmente vers l'Est. Les estimations de raccourcissement restent cependant très faibles (2 à 3%) en comparaison des estimations faites par les modélisations GPS. A terre en Haïti, nous avons imagé l'épaisseur crustale grâce à une étude de fonctions récepteur. Les épaisseurs imagées délimitent trois domaines différents. Nous proposons que ces domaines correspondent à trois ensembles géologiques distincts, composés respectivement de l'arc Crétacé des Grandes Antilles au Nord, du plateau océanique Caraïbe au Sud, et d'une croûte continentale au centre. Cette croûte pourrait être sous-charriée par du matériel dense provenant de la subduction d'une portion du plateau océanique Caribéen sous Haïti. / The Northern Caribbean transpressive plate boundary is expressed in Haiti by the partitioning of the deformation between two strike-slip faults and compressive structures. Bathymetric, seismic reflection and receiver-functions studies are methods used here to constrain the structure and the dynamic of the Northern Caribbean transpressive plate boundary offshore and onshore. The bathymetric data acquired during the Haiti-SIS cruises provide a detailed mapping of the geometry and segmentation of the senestrial strike-slip fault systems. The seismic profiles in the Jamaica Passage show that basin structures exist prior to the initiation of the EPGFZ and are cross-cut and folded by the EPGFZ. We identify a distinct crustal domain that we relate to the Caribbean large igneous province. The present deformations offshore show that the EPGFZ is primary strike-slip, with an increasing compressive component of the deformation toward the east. The shortening estimates are very small (2 to 3%) compared to the short-term GPS modeling estimates. Onshore in Haiti, we image the crustal structure from a receiver-functions study. The crustal thickness is ~23 km in the northern part of Haiti, ~22 km in the southern part of Haiti and ~41 km in the middle part, delimiting 3 distinct domains. We propose that these domains correspond to 3 geological distinct terranes: the Cretaceous volcanic arc in the north, the oceanic igneous province in the south, and in between a continental crust underthrusted by dense material. The underthrusted material could be a subducted portion of the Caribbean large igneous province under the Trans-Haitian fold-and-thrust belt.

This study combines structural field data with microstructural observations in an analysis of a mid-crustal shear zone related to the emplacement of the Misty pluton during a high-flux magmatic event in Northern Fiordland, New Zealand. These high-flux magmatic events transport massive amounts of heat and material as they develop along accretionary continental margins, and represent a primary source of continental crust. Fiordland, New Zealand possesses, perhaps, the most extensive middle and lower crustal exposure of these systems on earth. Therefore, this study area provides a significant opportunity to understand processes of continental crust formation in the mid-crust and how these events relate to the broader construction of continents. Herein, I document the four-stage geologic history of the Cozette Burn field area. Pre-existing structures along the Gondwana accretionary margin hosted a regional flare-up magmatic event that produced the Misty pluton and several other large plutons of the West Fiordland Orthogneiss (WFO). This study primarily focuses on the mid-crustal emplacement of the Misty pluton during oblique convergence along the accretionary margin, forming the upper-amphibolite facies Misty Shear Zone (MSZ). The exposures of the MSZ within the Cozette Burn preserve rare structural relationships between host rock and the intrusive Misty pluton. Together, these structures developed during end-stage contractional tectonics that constructed a long-lived (~270+ Ma) composite batholith. Heterogeneous ductile shearing defines the MSZ, with microstructural evidence indicating an interplay of high-temperature crystal plastic deformation along with partial melting of host rock and melt channeling. This resulted in focused, melt-assisted shearing under regional transpressive deformation. These accommodative processes provided an efficient mechanism for moving heat, fluids and magma sourced from the lower crust/mantle boundary into the mid-crust during 15-25 km of crustal thickening related to arc flare-up magmatism. This flare up magmatism and MSZ formation occurred during the final stages of crustal thickening along Gondwana continental margin. High-strain, mylonitic- ultramylonitic shear zones developed in a later phase of deformation, cutting MSZ fabrics near contacts between the Misty pluton and host rock. These more localized shear zones can be attributed to either accommodation of localized melt-pressure buildup or the shift to extensional tectonics. Brittle faulting cut these structures with oblique-thrust in the Tertiary. These mid-crustal structures carry economic relevance: thickened-crust events along accretionary continental margins produce deep-crustal sourced, metal-bearing magmas that are transferred into mid-crust prior to their hydrothermal emplacement as ore deposits in the upper crust. The lasting influence of these processes warrants consideration when assessing continental crust architecture at all scales.