The effect of fluids on deformations
2002. "The effect of fluids on deformations", Deformation Mechanisms, Rheology and Tectonics: Current Status and Future Perspectives, S. de Meer, M. R. Drury, J. H. P. de Bresser, G. M. Pennock
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Dead weight uniaxial compaction creep experiments were carried out on fine-grained, super-pure calcite (<74 μm) at room temperature and applied effective stresses of 1–4 MPa. All samples were pre-compacted dry at a stress of 8 MPa, for 30 minutes, to obtain a well-controlled initial porosity. The samples were then wet-compacted under ‘drained’ conditions with pre-saturated solution as pore fluid. Control experiments, which were done either dry or with chemically inert pore fluid, showed negligible compaction. However, samples tested with saturated solution as pore fluid showed easily measurable compaction creep. The compaction strain rate decreased with increasing strain and increasing grain size, and increased with increasing applied stress. Addition of Mg2+ ions to the saturated solution dramatically inhibited compaction. From the literature, Mg2+ ions are known to inhibit calcite precipitation. By comparison with a theoretical model for intergranular pressure solution in calcite, the observed mechanical behaviour and the way that compaction responded to the pore fluid chemistry suggest that, under our experimental condition, intergranular pressure solution is the mechanism of the deformation and that precipitation is likely to be the rate-limiting step.
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The motion and deformation of rocks are processes of fundamental importance in shaping the Earth, from outer crustal layers to the deep mantle. Reconstructions of the evolution of the Earth therefore require detailed knowledge of the geometry of deformation structures and their relative timing, of the motions leading to deformation structures and of the mechanisms governing these motions. This volume contains a collection of 22 papers on field, experimental and theoretical studies that add to our knowledge of these processes. They are a mixture of review papers oh selected topics in the field of structural geology and tectonics and papers on current issues and new techniques and are grouped into four themes:
The effect of fluids on deformation
The interpretation of microstructures and textures
Deformation mechanisms and rheology of crust and upper mantle minerals
Crust and lithosphere tectonics
The volume will appeal to researchers in the fields of structural geology and tectonophysics, both in academia and industry.