Seismic and thermochemical structure of the lithosphere: implications for continental evolution and resource potential

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In the last 10-15 years, there has been a remarkable increase in seismic data coverage over much of the North American continent, due to regional and national initiatives to install networks of seismograph stations to record earthquake signals. The seismic waves from global earthquakes, recorded at these stations, provide a wealth of information on Earth structure, as their speed depends on the nature of the rocks through which they travel. My research to date concentrated on establishing seismic models of the crust and upper mantle across regions of central, eastern and northern North America using a variety of methods to capture this structure. My proposed research program will investigate the crust and upper mantle of northern North America, in particular, the Canadian Shield and its surroundings, using an innovative approach that explicitly explores the variations in temperature and chemical composition, properties that are not readily distinguishable from seismic data alone. My research group and I will integrate a wide variety of data sets, including geophysical (seismology, topography, gravity and heat flow) and geochemical (global databases of rock composition and data from the Canadian Shield) measurements to model these structural variations. We will also contribute new high-resolution seismic models to these data sets. Offshore areas surrounding Canada have suffered from poor data coverage in the past, hampering efforts to understand continental rifting and breakup. To address this issue, I will be active in experiments involving ocean-bottom seismometer installations from a new national marine seismology facility, with a focus on the St. Lawrence valley and Baffin Bay. Overall, my program will include research projects for 5 graduate students and 1 postdoc, plus smaller projects suitable for undergraduates. The new research program will provide important insights into how continents are formed and how they evolve over geologic time. The seismic and thermal/chemical models provide a present-day "snapshot" of continental structure, which will be used in conjunction with geochemical measurements to understand better the geologic history of the continent. As well as answering fundamental questions about the Earth's evolution, my proposed research program will address issues related to the exploration for natural resources across central and eastern Canada where the most ancient crust is found. While much of the mineral exploration across Canada has traditionally focused on geologic mapping and shallow geophysical studies, interest is increasing in the "mineral systems" approach to exploration, where a fundamental understanding of large-scale crust and upper mantle structure provides key information on the processes that control the evolution and emplacement of economically important minerals. My new thermal/chemical models of the crust and upper mantle will be of significant importance to this developing exploration paradigm.