Faults and fluids in accretionary orogens

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Accretionary orogens (mountain belts) form over tens to hundreds of millions of years as continental and oceanic fragments (terranes) carried on a subducting oceanic plate accrete to a continental plate margin. These multiple collisions produce a complex network of faults (breaks in the Earth's otherwise largely impermeable crust) in the resulting mountain belts, that can be prone to later slip (reactivation). The faults can be efficient pathways for the transfer of rock melt (magma), fluids and heat, which facilitate the flux and concentration of metals. Many ore-deposit settings (e.g. deformation zones, intrusions, basins) occur within or proximal to accretionary orogen fault systems, and host metals, many of which are considered essential for Canada's future society (e.g., Sn, W, Mo, In, Au, Bi, Co, U). The long-term objective of my research program is to document the fault, fluid and thermal records of orogenic upper crust and relate them to geodynamic processes and ore-deposit formation. My recent work has focused on coeval geological, structural and ore-system records in Canada's flanking accretionary orogens, the east coast Canadian Appalachians and the west coast Canadian Cordillera. These studies suggest that ore-relevant processes may have been triggered by perturbations of the Earth's lithospheric mantle (the layer of the Earth that underlies the crust) beneath accreted terranes. My short term objectives (O1-3) are focused around testing that hypothesis in these two orogens. Over the next five years, I will (O1) reconstruct the temperature-time and structural evolution of the upper crust during post-accretionary reactivation of orogenic fault zones using field mapping, analysis of rock microstructures, and petrochronology and thermochronology rock dating methods. I will (O2) determine the fault-fluid-critical metal mineralization relationships during these periods using novel methods including U-Pb dating of slickenfibres and veins, K-Ar dating of fault gouge clay and stable and clumped isotopes. Finally, I will (O3) explore how lithospheric perturbations such as subducted slab break-off and delamination may influence the temperature-time evolution of the upper crust in a post-accretionary orogenic setting via numerical modeling. This work will result in a refined framework for long-term fault behaviour in accretionary orogens, particularly in the contexts of orogen lithosphere evolution and ore-deposit formation. Results will contribute to Canada's ability to search for its critical mineral resources. HQP involved in conducting this research will collaborate with world-class laboratories, industry, and government, and will develop transferable skills in analytical research, data management, common structural geology and ore deposits field and laboratory research methods, and science communication.