GEOLOGY 1 Lecture Notes - Lecture 15: Work Hardening, Differential Stress, Coble Creep
Document Summary
Dissolution at source -> diffusion/migration of dissolved material -> reprecipitation. Diffusion: atom to atom movement through grain interiors, along grain boundaries, across pore fluids. A slow, temperature dependent process (higher temperatures = higher diffusion rates) Fastest (most important): in fluids between grains, where crystal lattices with lots of impurities, in fine-grained rocks. Lower temperatures and more efficient than volume-diffusion creep. Movement of atoms along grain boundaries faster then within grains. Occurs if high temperatures / directed stress. Diffusion within mineral grains by atom swapping. Vacancies in lattice move toward high compressive stress and eventually out of lattice completely. Dislocations are linear arrays of lattice imperfections and there are. Edge dislocations (geometrically analogous to type 2 fractures) Screw dislocations (geometrically analogous to type 3 fractures) Edge dislocation: these form as a result of an extra half lattice plane in the crystal. The termination of the extra half lattice is the dislocation.
