Microstructures in deforming–reactive systems
Bruce E. Hobbs, Alison Ord, 2011. "Microstructures in deforming–reactive systems", Deformation Mechanisms, Rheology and Tectonics: Microstructures, Mechanics and Anisotropy, David J. Prior, Ernest H. Rutter, Daniel J. Tatham
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The inter-relationships between mineral reactions and deformation are explored with a view to understanding the development of certain mineral foliations and lineations. The following arguments are presented: (i) the processes involved during mineral reactions in deforming metamorphic rocks are described by coupled reaction–diffusion–deformation equations; (ii) these reactions can become unstable producing compositional patterning in both space (metamorphic differentiation) and time (compositional zoning); (iii) the patterns (foliations and mineral lineations) that result from coupled reaction–diffusion–deformation equations are described by surfaces that approximate minimal surfaces (surfaces of zero mean curvature) and an example of such geometry is given; and (iv) the foliations and mineral lineations that form by such processes are controlled by the evolution of the kinematics of the deformation history and not by the finite strain tensor.
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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.