Experimental and theoretical basis of electrokinetic phenomena in rock‐water systems and its applications to geophysics

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Abstract
The ζ potentials and the streaming potential coefficients of silicate mineral‐water and rock‐water systems were measured for purposes of estimating the magnitude of electrokinetic effects induced by water diffusion in the earth's interior. In rock‐water systems the adsorption reaction of H+ at a solid surface is proved to be a main factor determining the ζ potential. For typical crustal rocks the ζ potential in water of pH higher than 2 is commonly negative and increases in absolute magnitude as supporting electrolyte concentration decreases and as temperature increases. A physicochemical theory was developed on the above features of the ζ potential on the basis of the adsorption reaction at the solid‐liquid interface. The experimental and theoretical results obtained in the present study of the ζ potential and the streaming potential coefficient in rock‐water systems are applied to some geophysical problems: electromagnetic variations induced by water diffusion prior to earthquakes and the self‐potential anomaly associated with hydrothermal convection.