Geometry of intercrystalline brine in plastically deforming halite rocks: inference from electrical resistivity
Published:January 01, 2010
Tohru Watanabe, 2010. "Geometry of intercrystalline brine in plastically deforming halite rocks: inference from electrical resistivity", Advances in Interpretation of Geological Processes: Refinement of Multi-scale Data and Integration in Numerical Modelling, M. I. Spalla, A. M. Marotta, G. Gosso
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Electrical impedance measurements were performed on deforming fine-grained (c. 300 µm) synthetic halite rocks containing small quantities of water in order to study the distribution of intercrystalline brine. The experimental conditions were 125 °C and 50 MPa confining pressure. The resistivity at the predeformational, heated and hydrostatically pressurized state suggests that brine is interconnected in halite. The resistivity progressively increases with deformation, reflecting the change in distribution. In this paper we applied a simple tube model to the resistivity change, and found that the change must be caused by deformation of a thin fluid path with an initial aspect ratio of less than 2×10−4. Brine must, therefore, exist on grain boundaries as a thin fluid film. Previous studies on dihedral angles, however, showed that brine cannot be interconnected under our experimental conditions. The variation in grain-boundary energy cannot explain the coexistence of grain-boundary brine with a positive dihedral angle. The observed resistivity change requires grain-boundary brine to be very thin (<100 nm). Such a thin fluid film might have properties distinct from the bulk fluid, and coexist with brine pores at grain corners and grain faces.
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Advances in Interpretation of Geological Processes: Refinement of Multi-scale Data and Integration in Numerical Modelling
Iterative comparison of analytical results and natural observations with predictions of numerical models improves interpretation of geological processes. Further refinements derive from wide-angle comparison of results from various scales of study. In this volume, advances from field, laboratory and modelling approaches to tectonic evolution – from the lithosphere to the rock scale – are compared. Constructive use is made of apparently discrepant or non-consistent results from analytical or methodological approaches in processing field or laboratory data, P–T estimates, absolute or relative age determinations of tectonic events, tectonic unit size in crustal scale deformation, grain-scale deformation processes, various modelling approaches, and numerical techniques. Advances in geodynamic modelling critically depend on new insights into grain- and subgrain-scale deformation processes. Conversely, quantitative models help to identify which rheological laws and parameters exert the strongest control on multi-scale deformation up to lithosphere and upper mantle scale.