Date of Award
Master of Science
Dr. Dazhi Jiang
The theory for the deformation of the clast-matrix system where the clasts are rigid is based on Jeffery (1922, Proceedings of the Royal Society of London A102, 161-179) and is well understood. The theory for the deformation of the clast-matrix system where the clasts are deformable (Eshelby, 1957, Proceedings of the Royal Society of London A241, 376-396) has not been well studied, although it is more applicable to rock deformation. Recent studies indicate that a large discrepancy exists between microstructural data and the predictions based on Jeffery’s theory. Several mechanisms have been proposed to explain this discrepancy, but the problem remains unresolved. The purpose of this study is to numerically investigate the motion of a deformable clast immersed in a slow Newtonian viscous flow subjected to a general two dimensional deformation, and to apply the results to the microstructural analysis of mylonites, particularly, those from the southern Omineca Belt of the Canadian Cordillera. The motion of a deformable clast is determined by the bulk flow type, the viscosity ratio of the clast to the matrix, the aspect ratio and the initial orientation of the clast. Numerical investigations show that, for a kinematic vorticity number between 0 and 1, there are four regimes of clast behaviors and each regime has up to four types of clast deformation paths. It is found that a general model based on the modified Eshelby’s theory can be successfully applied to the interpretation of natural rock fabrics. Most mechanisms previously proposed to interpret the discrepancy between microstructural data and the predictions based on Jeffery’s theory can be explained by this general model proposed in this study. By comparing natural data with numerical results, the deformation kinematics and rheology of the high
strain zones in the southern Omineca Belt have been constrained.
Liu, Ruikun, "Deformation of the Clast-matrix System and its Application to the Microstructural Analysis o f Mylonites" (2009). Digitized Theses. 3897.