The origin, structural style, and reactivation history of the Tabbernor Fault Zone, . Saskatchewan, Canada BY James R. Davies A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillmeot of the requirements for the degree Master of Science Department of Earth and Planetary Sciences McGill University, Montreal @James Davies, 1998 National Library BiMiothèque nationale du Canada Acquisitions and Acquisiîions et Bibliographie Services services bibliographiques 395 Wellington Street 395. rue Wdlington OrtawaON KlAOW OctawaON KlA ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive Licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or seil reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'autew qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Frontispiece Wollaston Lake at sunset, summer of 1996 Abstract The Tabbernor ~aunzone (TFZ) in Saskatchewan is a >1500krn geophysical, topographie and geological lineament that trends approximately northward dong the province's eastern boundary. Detailed field mapping and petrographic analyses, coupled with remote sensing and geophysical evidence have shown that the TFZ is a fundamental structure within the Trans-Hudson Orogen (THO), separating and offsetting severai lithotectonic domains. Eariiest deformûtion presewed within the TFZ in the Wollaston Lake area is the transposition of a regionai gneissic foliation ont0 a northeast-trending fiattening piane, within north-trending sinistral shear zones. The transposed fabnc is characterized by folded and attenuated remnants of the gneissic foliation. together with boudinaged leumgranitic sheets and dykes. Within these shear zones a shear fabric is developed parailel to the margins in several locations. The shear fabric offsets dl earlier foliations with consistent sinistrai offset. Adjacent to the shear fabric, structures are reoriented to lie dose to the shear plane. The fault and its associateci structures controlleâ the intrusion of grmitic and pegrnatitic dykes which were subsequently weakiy deformed. These intrusives relate to a regionai magmatic episode assouated with the culmination of the second tectonornorphic event in the THO at 1815Ma. Post-collisional adjustments caused localized reactivation of stnictures and assoaated retrogresive metamorphism. Brittle overpnnting of ductile fault features is widespread. Mineralized fault planes display well-developed slickenlines which formed during more than one reactivation episode. Reactivation may have been coevai with the age of formation of large uranium deposits in the irnmediately adjacent Athabasca Basin. Structural similafiaes between the TF2 and rninerdized areas suggest that the fault may have had a control on the location of minerakation. Sedirnentary features, apatite fission track data, and uranium mineralogical studies ail show that the TFZ was readvated at least twice in Phanerozoic times. Late Devonian tectonic events associated with the Antler Orogen caused reactivation of the TF2 dong much of its length. In southern Saskatchewan fault reactivation cuntrolled depositional patterns and structures within the Williston Basin. Further north. fault reactivation resulted in the widespread rernobilization of uranium-bearing minerais. Reactivation in the Eady Cretaceous Pefiod, associated with Cordilleran orogenic activity. had similar affects. The identification of multiple reactivations of an intracratonic structure calls into question the model of a 'stable' craton. La zone de la faille de Tabbemor (ZFï). situde en Saskatchewan, reprdsente un lineament g6ologique. topographique et gdophysique de plus de 1500km. Elle présente une orientation nord, longeant la frontière Est de la province. Une cartographie detailiee et une Btude petrographique, jumelés aux donnees de télédetedion et aux Bvidences geophysiques illustrent dairement qu'il s'agit d'une structure fondamentale au sein de I'orogène Trans-Hudsonienne (THO)l séparant et décalant plusieurs domaines lithotectonics. Dans la region du Lac Wollaston, les premieres evidences de d6formations observées au sein de la ZFT sont caracterisees par la transposition d'une foliation gneissic regionale dans un plan nord-est. Ce plan est situ6 A l'intérieur d'une zone de cisaillement qui est orienté vers le nord et & ddplacement sénestre. La fabrique transposee est caracteris& par des plis et des traces résiduelle de la foliation gneissk accompagne de feuillets leucogranitique et de dykes boudin&. A diffhnt endroits. plusieurs de ces zones de deformation possedent une fabrique de cisaillement paraiMe aux marges, deplaçant les foliations precedentes avec un mouvement s6nestre. Aux abords des plans de cisaillement, les structures sont rborientées de façon à être similaire aux fabriques de cisaillement. La faille de Tabbernore ainsi que les structures associées contrôlent l'intrusion de dykes granitiques et pegrnatitiques qui furent par la suite faiblement déformés. Ces intrusions sont associées à un épisode magmatique régional. associé avec la culmination du second 6venement tectonomorphique dans la THO. à 1815Ma. Des ajustements post-collisionnaux? ont causé la réactivation des différentes structures ainsi qu'un mdtamorphisme rétrograde. iii La superposition de structures cassantes sur les zones de faille ductile est trbs fr6quente. Les pians de failles min6raJises possèdent des "did<enlinesn bien développes formés lors de diffdrentes périodes de rdacüvation. La r&acüvation des plans de failles est probablement contemporaine la formation de grand d6pôts d'uranium dans le bassin adjacant d'Athabasca. Les similarit6s structurales entre la ZFT et les zones rnin&ralis&essuggdrent que la faille puisse avoir un contrôle sur la localisation de la rnindralisation uranifbre. Les caractéristiques s6dimentaires. les donnees de fission de I'apatite? ainsi que les résultats des Btudes sur la minhiagie des min6raux uranifhres démontrent tous que la rbactivation. Phan6rozoïque de la ZFT semble s'être produite a deux reprises. Les Bvenements tectoniques du DOvonien tardif associés B IOrogéne d'Antier, ont causds la r6activation de la ZFT sur presque toute la longueur de celle-ci. Dans le sud de la province du Saskatchewan. la réactivation de la faille contrôle les patrons de ddpdt ainsi que les structures a I'intdrieur du bassin de Williston. Plus au nord. la rdactivation de la faille a produit une rembilisation génerale des mineraux d'uranium. Cette rembilisation des mineraux uranifhres s'est aussi produite lors de la r6activation de la ZFT au Crétace Inférieur lors de I'Orog8ne CordilliBflenne. L'identification de plusieurs phases de rdactivation d'une structure intracratonique remets en question le modele d'un craton "stable". This thesis consists of four chapters, the second and third of which are in manuscript form. and are intended for submission to a refereed journal. In accordanœ with McOill thesis preparation guidelines the candidate is required to make an explicit statement on the authonhip of dl work submitted as part of the thesis: The analyses of two rock sarnple suites from the Wollaston Lake and Neilson Lake areas were undertaken by Dr. Barry Kohn, at the Australian Geodynarnics Cooperative Research centre. La Trobe University, Bundoora, Victoria. The samples were analyzed to provide an apatite fission track age for each sample. As well as the results, Dr. Kohn also provided a preliminary interpretation of the fission track age data within the context of the North Amencan continental history. Ail subsequent interpretetion of the data in relation to the cunent study is the work of the author. The Neilson Lake sample suite was collected by Colleen Elliott. Ail other data collection, preparation. analyses and presentation within the thesis was conducted entirely by the author. The thesis supervisor, Colleen Elliott of Concordia University. has reviewed both manuscri pts. Acknowledgements The author would like to acknowledge the role of his field assistants Luke Willis, Gary Smith, and Rami Mirshak for their patient and diligent work dunng two summers of fieldwork on Wollaston Lake. Additional field logistics were supplied by Gary Delaney, Tom Sibbald and Bruno Lafrance (dl Saskatchewan Energy and Mines). Laboratory preparation and results of fission track analyses on two sample suites was provided by Barry Kohn at La Trobe University. Victoria. Supervision of the Masten program was undertaken by Colleen Elliott of Concordia University. Colleen Elliott aiso gave review and cornments that greatly improved the organization 'and preparation of the two manuscripts. French translation of the thesis abstract by tissa Morotti and Annick Chouinard is gratefully acknowledged. I am especially indebted to Gary Delaney, lnhne Annedey (Saskatchewan Research Council), Don Baker, and Andrew Hynes (both McGill University) for their continued comments and advice during the cornpletion of this project. Funding for