From mantle geodynamics to environmental processes: a geochemical perspective

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Modern geochemistry provides us with the ability to investigate fundamental characteristics of our planet by quantifying and explaining the transfer of elements within and between major components of the Earth, including the lithosphere, the hydrosphere, the biosphere, and the atmosphere. Such research requires unprecedented precision and sensitivity for the analysis of elemental concentrations and isotopic ratios in rocks, minerals, water, and organic matter that can only be provided by modern and specific instruments (e.g., mass spectrometers). Importantly, these tools can be applied to many areas of study, including the relationship between our environment and human health. The overall goal of my proposed research program is to constrain the geochemical evolution of our planet and its main reservoirs, to evaluate the impact of pollution on the environment, and to train young scientists in geochemistry to be leaders in the workforce.As the Earth's deep interior cannot be directly sampled, geochemists rely on analyzing lavas to infer the composition of the mantle (84% of Earth's volume). I will study lavas from three large modern mantle plumes (Hawaii, Kerguelen, Galapagos) originating from deep in the mantle. Together with Cascade Arc volcanoes and sediments, I will model the amount of crustal recycling into the mantle using novel isotopic systems allowing to trace different signals and distinguish between recycled sediments, recycled oceanic crust, or slab melting. The results of this research will contribute to the chemical characterization of the mantle and its heterogeneities over geologic time and will transform the current mantle geodynamic model and help build transdisciplinary bridges. My research will also establish the source of Pacific NW volcanoes while identifying some potential hazards related to their activity.I will develop new analytical schemes for mass spectrometers to model oxide formation and problematic matrix effects, which is critical to achieve the best precision and reproducibility. This work will lead to an invaluable set of best practices and methodology for the scientific community. I will also use heavy stable isotope systems coupled with lead fingerprinting to examine element cycling and metal pollution in marine and terrestrial ecosystems as well as to trace the diet and movement of humans and animals through space and time. This work will increase our understanding of ancient climates and the respective roles of humans and nature in the distribution of potential pollutants in British Columbia. Documenting natural levels will help establish clean standards for fisheries and agriculture, and will provide constraints for both modern and ancient human occupation of the landscape.