HR: 1340h
AN: T33C-1499    [Abstracts]
TI: Coupling between pressure solution and fracturing processes discussed from indenter experiments
AU: * GRATIER, J
EM: Jean-Pierre.Gratier@obs.ujf-grenoble.fr
AF: University of Grenoble, LGIT, CNRS-Observatoire Rue de la Piscine, Grenoble, 38041, France
AU: RENARD, F
EM: Francois.Renard@obs.ujf-grenoble.fr
AF: University of Grenoble, LGCA, CNRS-Observatoire Rue de la Piscine, Grenoble, 38041, France
AU: RENARD, F
EM: Francois.Renard@obs.ujf-grenoble.fr
AF: University of Grenoble, Physics of geologic processes Sem Selands vei 24, Oslo, 0316, Norway
AU: BERNARD, D
EM: bernard@icmcb-bordeaux.cnrs.fr
AF: University of Grenoble, ICMCB-CNRS Av. Dr Schweitzer, Pessac, 33608, France
AB: Pressure solution is a mechanism competing with cataclasis during sediment deformation. For example, both mechanisms are well documented in fault zones where they interact to make sedimentary rocks behave in both brittle and viscous manners. Cataclasis is associated with earthquake rupture whereas pressure solution accommodates post-seismic creep and sealing processes. In basins, sedimentary grains deform both by pressure solution and cataclastic deformation and are responsible for sediment compaction and porosity loss. As a consequence, the coupling between pressure solution and fracturing processes is a major issue, which we have studied experimentally. Indenter technique is a good technique for pressure solution studies since it allows controlling the distance of mass transfer, a crucial parameter in pressure solution constitutive laws. We have performed pressure solution indenter experiments on various kinds of single crystals leading to contrasting effects of the fracturing process on the kinetics of pressure solution creep. Indenting of quartz crystals leads to various hole shapes under the indenter. Cylindrical holes with a diameter equal to the indenter diameter are obtained at low stress (25-50 MPa), whereas hole larger than the indenter diameter are obtained at higher stresses (100-300 MPa). Reverse crown-shaped fractures below the indenter are associated with such a hole enlarging process. Successive fracture sets are created, then partially healed during the progressive indenting. However, displacement rates showed an exponential dependence on the stress values, as predicted theoretically. So the development of such fractures does not seem to significantly increase the kinetics of pressure solution. Conversely, indenting halite crystal in presence of brine solution led to different fracturing effects. At low stress no fracturing could be observed and the diameter of the hole was equal to the diameter of the indenter. However, near halite yield stress value, radial fractures developed and the rate of pressure solution kinetics was increased by a factor ten. We interpreted radial fracturing to have augmented the rate of diffusive mass transfer along the contact between the indenter and halite by a short cut of diffusion through the free-fluid filled fractures. We discussed the applications of these results to the modelling of rheological and permeability evolution of sedimentary rocks.
DE: 8030 Microstructures
DE: 8034 Rheology and friction of fault zones (8163)
DE: 8045 Role of fluids
DE: 8160 Rheology: general (1236, 8032)
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting