| This thesis encompasses ultramafic xenoliths, granulite-facies metamorphic rocks and sedimentary rocks, which are representative of the Earth's upper mantle, lower crust and upper crust, respectively. The accent is on plastic flow, brittle fracturing, microstructures, mechanical processes, and petrophysical properties of these rocks. Chapter 1 gives the indispensable background on elasticity, seismic anisotropy, shear-wave splitting, the shear-lag model and fluid inclusions; these will be crucial to understand the next chapters of the thesis. Chapter 2 is devoted to plastic deformation, lattice preferred orientations, and seismic properties of ultramafic xenoliths from the southern Canadian Cordillera. Analyses of the Pn and SKS splitting data obtained from the region, based on the calculated seismic properties of the mantle xenoliths, suggest that both the foliation and stretching lineation are horizontal in the upper mantle beneath the southern Canadian Cordillera and the seismic anisotropy extends to about 400 km depth. Chapter 3 deals with pervasive, closely spaced, relatively straight, tensile fractures in garnet crystals from granulite facies metamorphic rocks from the Morin shear zone in the Grenville province and explores the possible implications of these fractures for the uplift process of high grade metamorphic terranes. A modified shear-lag model is developed to explain why tensile fracturing took place preferentially in stiff garnet rather than in felsic material, and why the fractures are unequally spaced in the garnet grains. The final chapter is concerned with the relationship between joint spacing and layer thickness in Cambrian sedimentary rocks from the Quebec Appalachians. Taking into account a non-linear decay of the shear-stresses and various thicknesses of bounding non-jointing beds, an improved shear-lag model has been developed in order to better predict observed variations of saturated joint spacing as functions of both jointing and non-jointing layer thicknesses. The model may have important potential significance for the solution of a number of very practical problems in the design and stability of engineering and mining projects. |
