Surface conductivity in rocks: a review

Ruffet, C.; Darot, M.; Guéguen, Yves

doi:10.1007/bf00682714

Cited by 39 publications

(26 citation statements)

References 32 publications

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“…At low frequencies, very high-relative permittivities (up to 10 4 ) were measured in mineral-water mixtures, though the constituents exhibit relative permittivities in the range of 5-80. This behaviour is of particular importance for clay-water mixtures (Olhoeft, 1987) that were the starting point for the detailed studies of interfacial effects and surface conductivity (Ruffet et al, 1995;Bo¨rner and ELECTRICAL PROPERTIES OF CRUSTAL AND MANTLE ROCKS Scho¨n, 1995;Revil et al, 1996). Ruffet et al (1995) and Revil et al (1996) studied surface conductivity r s in detail and presented an equation considering the electrochemical dependencies:…”

Section: Electrolytic Conductionmentioning

confidence: 99%

“…where C a , C c are the concentrations of the anions and cations, v a , v c are the mobilities and f a , f c are the conductivity coefficients depending on the concentration and chemical composition and ion charge (Ruffet et al, 1995), and with DT being the difference of temperature from 20°C (Dachnov, 1975). Following the argument above that a rock sample can be considered as a three-component system, then the total conductivity r t of a fluid saturated Figure 7.…”

Section: Electrolytic Conductionmentioning

confidence: 99%

“…Many research papers and review papers have been published giving a thorough overview of the physical and chemical parameters that control the electrical charge transport in rocks and minerals (Olhoeft, 1976;Olhoeft, 1979;Cemic et al, 1980Cemic et al, , 1981Duba et al, 1974Glover and Vine, 1995;Glover et al 1996;Hinze et al, 1981Hinze et al, , 1982Revil et al, 1996;Ruffet et al, 1991Ruffet et al, , 1995. Within the last 10 years many efforts were concentrated on the application of more sophisticated techniques to get a deeper insight into the physical and chemical parameters that control the electrical charge transport.…”

Section: Introductionmentioning

confidence: 98%

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Electrical Properties of Crustal and Mantle Rocks – A Review of Laboratory Measurements and their Explanation

Nover¹

2005

Surv Geophys

112

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The electrical properties of rocks and minerals are controlled by thermodynamic parameters like pressure and temperature and by the chemistry of the medium in which the charge carriers move. Four different charge transport processes can be distinguished. Electrolytic conduction in fluid saturated porous rocks depends on petrophysical properties, such as porosity, permeability and connectivity of the pore system, and on chemical parameters of the pore fluid like ion species, its concentration in the pore fluid and temperature. Additionally, electrochemical interactions between water dipoles or ions and the negatively charged mineral surface must be considered. In special geological settings electronic conduction can increase rock conductivities by several orders of magnitude if the highly conducting phases (graphite or ores) form an interconnected network. Electronic and electrolytic conduction depend moderately on pressure and temperature changes, while semiconduction in mineral phases forming the Earth's mantle strongly depends on temperature and responds less significantly to pressure changes. Olivine exhibits thermally induced semiconduction under upper mantle conditions; if pressure and temperature exceed $ 14 GPa and 1400°C, the phase transition olivine into spinel will further enhance the conductivity due to structural changes from orthorhombic into cubic symmetry. The thermodynamic parameters (temperature, pressure) and oxygen fugacity control the formation, number and mobility of charge carriers. The conductivity temperature relation follows an Arrhenius behaviour, while oxygen fugacity controls the oxidation state of iron and thus the number of electrons acting as additional charge carriers. In volcanic areas rock conductivities may be enhanced by the formation of partial melts under the restriction that the molten phase is interconnected. These four charge transport mechanisms must be considered for the interpretation of geophysical field and borehole data. Laboratory data provide a reproducible and reliable database of electrical properties of homogenous mineral phases and heterogenous rock samples. The outcome of geoelectric models can thus be enhanced significantly. This review focuses on a compilation of fairly new advances in experimental laboratory work together with their explanation.

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Section: Electrolytic Conductionmentioning

confidence: 99%

Section: Electrolytic Conductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Electrical Properties of Crustal and Mantle Rocks – A Review of Laboratory Measurements and their Explanation

Nover¹

2005

Surv Geophys

112

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“…[5][6][7] The dielectric properties of these systems are significantly affected by surface conduction along the fluid-solid interfaces. Hence, it is important to explicitly incorporate surface conduction into the mathematical formulations for the dielectric properties of these systems.…”

Section: Introductionmentioning

confidence: 99%

Complex dielectric response of ellipsoidal particles with surface conduction

Bertrand

Endres

2009

The Journal of Chemical Physics

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Both particle shape and surface phenomena significantly affect the effective complex dielectric properties of colloidal systems. The treatment of particle shape has generally relied on the extrapolation from the solution of the spherical case proposed by O'Konski [J. Chem. Phys. 64, 605 (1960)] that treats ellipsoidal particles possessing surface conductivity as equivalent homogeneous anisotropic ellipsoids with bulk conduction. To test this approach, we have performed a rigorous analysis of the complex dielectric response of an ellipsoidal particle with surface conductivity using the generalization of the O'Konski boundary conditions to an ellipsoidal shape. The resulting closed-form solution obtained shows that surface conduction effects are represented by an equivalent inhomogeneous anisotropic ellipsoid. For the case of a spheroidal particle, the principle axes of the effective dielectric permittivity tensor of the equivalent particle are aligned with its geometrical principal axes; the effective permittivity varies in the direction of the unique spheroidal axis. In addition, numerical results indicate that the product of the surface area to volume ratio and the specific surface conductivity completely characterizes the effect of the surface phenomena on the response of spheroidal particles with a given shape. Numerical simulations show that spherical and prolate spheroidal particles exhibit a progressive dielectric enhancement while more disklike oblate spheroidal particles undergo an initial dielectric suppression followed by a subsequent enhancement with increasing surface conduction. A comparison of our model predictions with those obtained using the O'Konski approximation revealed significant differences in the magnitude of the low-frequency dielectric enhancement and relaxation frequency for ellipsoidal particle suspensions.

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“…Conduction of electrical current through a volume of porous rock occurs along three 77 pathways: (1) through the rock matrix, (2) with conductive ions in the pore fluid, and (3) 78 along the water-rock interfaces in the pores; see Rink and Schoppers (1976), Guéguen and 79 Palciauskas (1994), and Ruffet et al (1995) for reviews, and Flóvenz et al (1985; for 80 information on Icelandic rocks. The matrix of both the igneous and sedimentary rocks found 81 in geothermal systems is not conductive and so the overall rock conductivity is controlled by 82 pore fluid conduction and interface (surface) conduction.…”

mentioning

confidence: 99%