Deformation Conditions of Quartz-rich Mylonites of the Grenville Front Tectonic Zone and Application to the Crustal Strength
Abstract
This thesis analyzes a suite of mylonites from the Grenville Front shear zone exposed southeast of Sudbury, Ontario. Lattice preferred orientations, titanium-in-quartz thermometer, and dynamically recrystallized grain size piezometer measurements were applied to obtain the deformation mechanisms, deformation temperatures (T), and differential stresses (σ), respectively. Results show that these mylonites were formed in the shear zone during the terminal stage of the Grenville Orogeny. The dominant deformation mechanism is by regime 2 dislocation creep. The deformation temperature is between 425-567 °C, and the differential stress is between 56-133 MPa. These results are discussed in the context of wet quartzite flow laws. This study shows that a recently calibrated flow law that considers the pressure dependence of the activation enthalpy is applicable to the Grenville Front shear zone. The thesis also improves our understanding of the Grenville Front deformation zone.