Diffusion-creep modelling of fibrous pressure shadows II: influence of inclusion size and interface roughness
J. R. Berton, D. W. Durney, J. Wheeler, 2011. "Diffusion-creep modelling of fibrous pressure shadows II: influence of inclusion size and interface roughness", Deformation Mechanisms, Rheology and Tectonics: Microstructures, Mechanics and Anisotropy, David J. Prior, Ernest H. Rutter, Daniel J. Tatham
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This paper extends previous work by us to gain a fuller appreciation of the physical factors that affect polycrystal diffusion-creep simulations of fibrous pressure-shadow growth around a pyrite inclusion. The earlier work dealt with the effect of diffusion ratio or diffusional conductance of the inclusion/matrix interface. The new work also examines the effects of inclusion geometry: a smaller inclusion of similar smoothness to the original, a regularly serrated inclusion the same size as the original and a coarse irregular inclusion of the same size. The results show: (1) significant enhancement of fibrous pressure-shadow growth and change of matrix strain pattern with decreased inclusion size, similar to an increase in diffusion ratio; (2) approach towards a maximum fibrous pressure-shadow growth at high diffusion ratios in the small-pyrite model; (3) little influence of the model serrations; (4) significant sliding on the interface at low diffusion ratios in all of the models; and (5) enhanced sliding in the irregular-pyrite model at low diffusion ratios. The results are qualitatively consistent with diffusion creep of a single grain interacting with a deforming medium. They demonstrate factors that may influence development of the natural structures under similar conditions in rocks.
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This collection of papers presents recent advances in the study of deformation mechanisms and rheology and their applications to tectonics. Many of the contributions exploit new petrofabric techniques, particularly electron backscatter diffraction, to help understand evolution of rock microstructure and mechanical properties. Papers in the first section (lattice preferred orientations and anisotropy) show a growing emphasis on the determination of elastic properties from petrofabrics, from which acoustic properties can be computed for comparison with in-situ seismic measurements. Such research will underpin geodynamic interpretation of large-scale active tectonics. Contributions in the second section (microstructures, mechanisms and rheology) study the relations between microstructural evolution during deformation and mechanical properties. Many of the papers explore how different mechanisms compete and interact to control the evolution of grain size and petrofabrics. Contributors make use of combinations of laboratory experiments, field studies and computational methods, and several relate microstructural and mechanical evolution to large-scale tectonic processes observed in nature.