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

TLDR

The study measured ζ potentials and streaming potential coefficients in silicate mineral‑water and rock‑water systems to estimate electrokinetic effects caused by water diffusion in the Earth’s interior. The authors measured ζ potentials and streaming potentials and developed a physicochemical theory grounded in surface adsorption reactions to explain the observed electrokinetic behavior. The study found that H⁺ adsorption at solid surfaces governs ζ potential, which is typically negative above pH 2 and grows in magnitude with decreasing electrolyte concentration and increasing temperature, and that these findings can explain electromagnetic variations before earthquakes and self‑potential anomalies in hydrothermal convection.

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 p H 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.