Deformation of the Earth: From Processes to Phenomena

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The research program seeks to understand processes by which rocks deform through consideration of natural examples, deformation experiments and theory. Particular interests are the triggers and mechanisms by which tectonic regions cycle between seismic (earthquakes) and aseismic (flow) deformation. Individual projects typically comprise combinations of fieldwork with laboratory analysis undertaken primarily by research students (undergraduate and graduate) as part of their disciplinary training. Field work includes classical geological mapping to determine the composition and geometry of distinct tectonic regimes, aided in turn by remote imaging such enhanced photogrammetry with drones, and LIDAR (light detection and ranging). Data are then integrated into 3-dimensional models of the geological structures. Analytical techniques range from optical (light) microscopy and scanning electron microscopy (SEM) to characterize textures at the scale of centimetres to micrometres (1 thousandth of a millimeter), and electron microprobe (EMP) for grain-scale chemical analysis. Electron beam scanning diffraction (EBSD) at the latter scales is capable of discerning not only compositional variations, but also crystallographic orientation differences among grains that are used to infer the progress of deformation “frozen” into the rock texture. A technique central to the research is transmission electron microscopy (TEM). TEM is capable of imaging mineral grains and particles to the nanometer scale (1 millionth of a millimeter), a necessary requirement for analyzing fault rocks in which particles often approximate this size. Because the ratio of surface area to volume for nanoparticles is so much greater than “normal” materials, it is not appropriate to simply extrapolate processes (diffusion, reactions, particle deformation) from standard observations to the ultra-fine-grained materials. Hence, TEM is able to acquire images, crystallographic data and chemical information at the scale needed to address the fundamental processes within deformed rocks. Imaging of 3-dimensional porosity and textural attributes is achieved by microCT x-ray analysis. The research program relates to understanding dynamics of Earth seen as earthquakes, volcanoes, the formation of economic mineral deposits by fluid-rock interaction focussed along ancient faults and shear zones Although earthquake hazards are largely concentrated along the west coast of Canada, there is an additional indirect effect of hazard through financial losses by the domestic insurance industry and foreign aid and disaster assistance related to external disasters such as the 2010 Haiti earthquake. Reaction to such events argues for investment in systematic study of such phenomena in support of better predictive models.