L'Orogène de l'Ungava correspond à la branche nord-est de l'Orogène Trans-Hudsonien et est situé sur la péninsule de l'Ungava dans le nord du Québec. La présence d'une éclogite de 1,8 Ga au sein du Domaine de Kovik dans l'Orogène de l'Ungava a été utilisée pour proposer une tectonique des plaques moderne active au Paléoprotérozoïque. Cette étude vise à contraindre la cinématique, la température et la chronologie de la déformation associée à une structure interprétée comme ayant permis l'exhumation de cette éclogite, la zone de cisaillement séparant le Domaine de Kovik du Domaine Nord. Nous avons combiné les observations de terrain le long de transects à travers le contact entre le Domaine de Kovik et le Domaine Nord, l'analyse microstructurale du quartz et de la titanite et des datations U-Pb sur titanite. Deux zones de cisaillement, localisées dans les orthogneiss du domaine de Kovik, ont été identifiées. La zone de cisaillement principale, distale au contact, est caractérisée par une cinématique de sommet-vers-le-sud et des fabriques d'axes-c du quartz associées à une déformation en aplatissement. La zone de cisaillement secondaire, proximale au contact, est caractérisée par une cinématique de sommet-vers-le-nord et des fabriques d'axes-c du quartz associées à une déformation plane. La température de déformation est contrainte à 627 et 580 ± 50°C pour les zones de cisaillement principale et secondaire, respectivement. La géochronologie U-Pb sur titanite a permis de définir deux populations de titanite. La vielle population, contrainte à ~1890 Ma, est contemporaine de la mise en place de la grande province ignée du Circum-Supérieur. La jeune population, contrainte à ~1740 Ma, est interprétée comme représentant la réinitialisation de la vieille population pendant un épisode de déformation tardive possiblement relié à l'effondrement de l'orogène. Nous interprétons que le contact entre le Domaine de Kovik et le Domaine Nord représente un détachement.

The southern Patagonian Andes record the Late Cretaceous closure and inversion of the Late Jurassic – Early Cretaceous Rocas Verdes marginal basin, subsequent development of the Patagonian retroarc fold-thrust belt and the Neogene to present tectonic superposition of a left-lateral strike-slip plate margin defined by the Magallanes- Fagnano fault zone. In this dissertation, I present new geologic maps, cross sections and detailed macro- and microscopic structural analyses that describe the geometry and kinematic evolution of the fold-thrust belt and superposed strike-slip deformation over ~200 km along-strike between 53° and 55° S latitude. Results are discussed in the context of the regional tectonic development of the southernmost Andes and are relevant to the understanding of important tectonic processes including the development of a retroarc fold-thrust belt, the formation of a basal décollement below and toward the hinterland of a fold-thrust belt and the spatial distribution of deformation along a strike-slip plate margin. New maps and balanced cross-sections of the Patagonian fold-thrust belt show that it developed during two main phases of Late Cretaceous to Paleogene shortening that were partly controlled by the antecedent geology and mechanical stratigraphy of the Rocas Verdes basin. During the Late Cretaceous, a thin-skinned thrust belt developed above a décollement that formed first in relatively weak shale deposits of the Rocas Verdes basin and later deepened to <1 km below the basement-cover contact. Ramps that cut mechanically rigid volcanic rocks of the marginal basin link the two décollements. Basement-involved reverse faults that cut the early décollements and probably reactivate Jurassic normal faults reflect Paleogene shortening. Shortening estimates increase northwest to southeast from 26 to 37% over 100 km along-strike and are consistent with regional models of the fold-thrust belt. Structural data, kinematic analyses, and microstructural observations from the lower décollement show that it is defined by transposition of several generations of northeast-vergent noncylindrical folds, shear bands, and a quartz stretching lineation that are kinematically compatible with first-generation structures of the fold-thrust belt. Quartz microstructural data from the décollement are consistent with deformation temperatures that decrease from ~500-650° C to ~400-550° C over ~75 km in the transport direction, indicating that the décollement dipped shallowly (~6°) toward the hinterland. The décollement decoupled the underthrust continental margin from the fold- thrust belt and exemplifies the kinematic relationship between shortening that occurs coevally in a retroarc fold thrust-belt and its polydeformed metamorphic ‘basement’. Fault kinematic data and crosscutting relationships show kinematic and temporal relationships between populations of thrust, strike-slip and normal faults that occur in the study area. Thrust faults form an internally compatible population that shows subhorizontal northeast-trending shortening of the fold-thrust belt and is kinematically distinct from populations of normal and strike-slip faults. Both strike-slip and normal faults crosscut the fold-thrust belt, are localized near segments of the Magallanes- Fagnano fault zone, have mutually compatible kinematic axes and are interpreted to be coeval. Strike-slip faults form Riedel and P-shear geometries that are compatible with left-lateral slip on the Magallanes-Fagnano fault-zone. Strike-slip and normal faults occur in a releasing step-over between two overlapping left-lateral, left-stepping segments of the Magallanes fault zone and record a tectonic event defined by sinistral transtension that probably reflects changing plate dynamics associated with the opening of the Drake Passage during the Early Miocene. / text