U-Pb Geochronology and Geochemistry by Nico Kastek a Thes
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2.0 to 1.9 Ga large igneous province magmatism in northern Quebec – U-Pb geochronology and geochemistry By Nico Kastek A thesis submitted to the Faculty of Graduate and Postdoctoral Affairs in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Sciences Carleton University Ottawa, Ontario © 2019 Nico Kastek ABSTRACT The northeastern margins of the Superior craton contain the Cape Smith belt and the Labrador Trough (including the Roberts Lake Syncline), which range from 2.2 to 1.9 Ga in age. This thesis examines the age of the Cape Smith belt, its correlation to other units of similar age and its possible extent to the southeast. Seven U-Pb ages on magmatic baddeleyite and zircon and 84 geochemical analyses were obtained of magmatic units throughout the Cape Smith belt. The most precise are two ages each for the Povungnituk and Chukotat Groups. The Povungnituk Group yields ages of 1998±6 Ma and 1967±7 Ma. The older age represents the main volcanic pulse, and matches previously obtained U-Pb ages for the Watts Group (Purtuniq) ophiolite of the northern Cape Smith Belt and the Minto and Lac Shpogan dyke swarms that intrude the Superior craton to the south. They define a large igneous province (LIP), extending over an area of >400,000 km2, herein defined as the Minto-Povungnituk LIP. The Minto-Povungnituk LIP can be divided into two spatially separate geochemical domains with different mantle source characteristics that can be produced in two ways: (1) melting of different portions of Superior craton lithosphere; or (2) two distinct deep mantle sources that remained separated within the ascending plume. ii A feeder dyke of the Chukotat Group yielded a U-Pb age of 1874±3 Ma, representing the younger end of its age range. An age obtained from the top of the Chukotat Formation yielded 1861±28 Ma and confirms the previously geochemistry-based interpretation that the Chukotat Group represents a single event. To the southeast of the Cape Smith belt, the Roberts Lake Syncline hosts two Paleoproterozoic mafic magmatic sequences but their correlation with the units of Labrador Trough to the south, or the Cape Smith belt to the north is uncertain. 94 geochemical analyses were obtained on the two volcanic units and the data show a closer match to the chemical stratigraphy observed within the Cape Smith belt, suggesting that the Roberts Lake Syncline is the easternmost portion of the Ungava Orogen rather than the northernmost part of the Labrador Trough. iii ACKNOWLEDGEMENTS I would like to first thank my primary supervisors, R.E. Ernst and B.L. Cousens. You have been an incredible help and I am thankful that you took the patience for the prolonged time it has taken me to get to this point. I also want to thank P. Sylvester, who supervised me during my first year at Memorial University of Newfoundland and dealt with me passing all of my PhD requirements. I owe a large debt of gratitude to W.R.A. Baragar, M.R. St-Onge and J.E. Mungall for allowing me to use some of their samples. I want to especially thank J.E. Mungall, who gifted me with a significant amount of time and helped me greatly in developing the fifth chapter of the thesis. I want to thank W. Bleeker, who guided me in the field and to whom I owe a deep understanding of my study area. He has also been an indispensable contributor to the development of our first publication on the geochronology and geochemistry of the Povungnituk Group. I want to thank Glencore for providing travel and access to the Raglan mine. I cherish the time I was able to spend on their facility and the samples they let me take. I also want to thank Anglo American and especially J.-F. Belanger, for welcoming me on their drill site in the Roberts Lake Syncline, access to all their samples and time on their on-site helicopter. I would not have been able to collect any of the data without M. Shaffer and D. Goudie, who assisted me with work on the SEM at Memorial University; U. iv Söderlund, who let me visit him at Lund University to learn his technique of separating baddeleyite; S. Kamo and M. Hamilton, who welcomed me in their laboratory at the University of Toronto and taught me how to analyze samples using ID-TIMS, sacrificing multiple weekends; K. Chamberlain who took me on as an assistant during one of his trips to UCLA for IN-SIMS dating and giving me enough of his measuring time to date two of my own samples; S. Jantzi for assistance with LA-ICP-MS geochronology at Memorial University; and D. Davis for assistance with LA-ICP-MS geochronology at the University of Toronto. S. Zhang has been a great help, providing guidance in the clean lab at Carleton University and amazing assistance during TIMS measurements. Special thanks to E.M.A. Bethell, who has been at my side through every bad and every good day. I owe you the mental and physical strength to have come to this point. Thank you for making Ottawa my home. Great thanks goes to S. Davey, my office mate since day one. You were a pillar of happiness and support in the past years. I count myself lucky to have been given the desk beside you. I want to thank C.C. Rogers, who has been an incredible colleague and an amazing friend. A lot of my research would not have reached its current quality without you. My officemates and colleagues have played a vital role in making my time at Carleton University the incredible journey it was. Thanks to J. Graff, D. Liikane, v M. Trenkler, K. Klausen, and K. Little. You guys were the reason I looked forward to coming into the office. Thanks to D. Hartten, D. Puccini, C.Bergemann, B. Wroniecki, and S. Horn, who surpassed the 5,870 km distance between us to keep a friendship alive and well and who constantly remind me that I always have a place in their lives. Finally, I want to thank my parents, K. and M. Kastek. Thank you for wholeheartedly supporting every decision I ever made and for giving me the opportunity to pursue my dream, although my actions might not always have been what you had wished for. I miss you. vi STATEMENT OF CONTRIBUTION Fieldwork and sample collection I (Nico Kastek) visited field locations the Roberts Lake Syncline in northern Quebec in the summer of 2013 to collect 10 samples. I was accompanied on the trip by W. Bleeker (Geological Survey of Canada), who helped me identify suitable samples and provided expertise on the regional geology. We were hosted by J.-F. Belanger from Anglo American, who led a drill project in the Roberts Lake Syncline and who provided us with transportation (air and land). An additional 7 rock samples and 84 rock powders were provided by W.R.A. Baragar and 2 rock samples from M.R. St-Onge for the Povungnituk Group. J.E. Mungall provided 84 unpublished major element analyses from the Roberts Lake Syncline, from which powders of 39 samples were taken for further trace element and platinum group element (PGE) analyses. Sample preparation Single polish thin-sections for selected coarse grained samples of the Povungnituk and Chukotat Group were prepared at Memorial University of Newfoundland. Samples not obtained as powder or crushed material were cleaned, cut into slabs, crushed to <2 mm and subsequently powdered in an agate mill by myself under the supervision of T. Mount (Carleton University). vii Major and trace element analyses All samples for the Povungnituk Group were sent to ALS Geochemistry laboratories in North Vancouver, British Columbia for major element analysis via Inductively Coupled Plasma Atomic Emissions Spectrometry (ICP–AES) as well as trace and rare earth element (REE) analysis via Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Major element concentrations for samples that J.E. Mungall collected from the Roberts Lake Syncline in 1998, 1999 and 2000 were determined by borate fusion X-ray fluorescence analysis at the Geoscience Laboratories (Geo Labs) of the Ontario Geological Survey in Sudbury, Ontario. Samples collected by myself in 2013 from the Roberts Lake Syncline and a subset of the sample suite provided by J.E. Mungall were sent to ALS Geochemistry laboratories in North Vancouver, British Columbia for ICP-AES. Isotopic analyses I performed sample preparation and all of the isotopic analyses for thermal ionization mass spectrometry (TIMS) at Carleton University’s Isotope Geochemistry and Geochronology Research Facility (IGGRF) under the supervision of S. Zhang. viii Geochronology I identified zirconium-bearing phases in thin section at the scanning electron microscope (SEM) at the TERRA facility – CREAIT (Memorial University Earth Science Department). I took promising samples to Lund University Geochronology laboratory, where I mechanically separated baddeleyite grains under the supervision of U. Söderlund. I separated additional baddeleyite grains at the Jack Satterly Geochronology Laboratory at the University of Toronto under the supervision of B. Foursenko. A difficult sample (BLS-73-31) was further processed by S. Kamo (also at the Jack Satterly Geochronology Laboratory) using heavy liquid (methylene iodide) and I picked the baddeleyite crystals from the remaining grains. I then assisted S. Kamo in Isotope Dilution Thermal Ionization Mass Spectrometer (ID-TIMS) U-Pb analysis. The data was edited by S. Kamo, who also interpreted the respective ages. I provided K. Chamberlain (University of Wyoming) with polished thin sections, in which zirconium-bearing phases had been identified. He re-analysed the samples via wavelength dispersive spectroscopy (WDS) at the University of Wyoming and identified zirconium-bearing phases using energy dispersive spectroscopy (EDS).