Assembly, evolution and dynamics of the eastern Canadian Shield: evidence from present-day seismic structure

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Eastern Canada has a rich geologic history, spanning ~4 billion years of tectonic evolution, and likely encompassing the beginning of the plate-tectonic processes of the Earth. Models of present-day crust and upper-mantle structure, in conjunction with studies of surface geology, are key to understanding the forces that shape the continents and the nature of the interactions between the plates and the convecting mantle beneath.My research focuses on understanding the present-day structure and tectonic history of the eastern Canadian Shield. Structural models are derived using data from global earthquakes recorded at broadband seismograph stations across the region, including northern Ontario, Québec, Labrador and the Hudson Bay region. I have played an key role in establishing new seismograph networks across Québec and Labrador, and am also taking an active part in the installation of the US EarthScope Transportable Array in southern Québec.The long-term scientific objectives of the research programme are to investigate the fundamental building blocks of our continent, considering questions such as (i) how does the thickness and nature of the continental upper mantle vary across different tectonic provinces, and is there a correlation between surface geology and deeper structures? (ii) how was the Canadian Shield assembled and what does this tell us about the history of plate tectonics? (iii) how do structural alignments in the mantle relate to past and present continental dynamics? (iv) how do the thick continental keels affect the patterns of flow in the convecting mantle?On the practical side, regional-scale models of upper mantle structure are of increasing interest to the mining industry, especially since diamond formation takes place only under certain mantle conditions. Models of the crust can also be used to refine earthquake locations and thus provide important constraints in seismic hazard research.