ELECTRICAL PARAMETERS OF ROCKS IN DEVELOPING GEOPHYSICAL TECHNIQUES

Abstract

An electrical rock measurement program has been initiated at the Geological Survey of Canada. Although there has been a considerable amount of work done in the past on electrical properties of rocks, the basic concept of the electrical theory applied to rocks and the definition of electrical parameters seem to differ between each group of scientists. This paper reviews the theory of the parameters that describe the complex electrical characteristics (conductivity, permittivity, and loss tangent) of rocks. A review is made of the measuring systems and classified by technique over the frequency range from [Formula: see text] to [Formula: see text] hz. For measurements on dry rocks and massive sulfide minerals, a 2‐electrode configuration is used. Measurement accuracy and reproducibility are within ±2 percent. The accuracy is checked against international standard samples. The research aspect of the laboratory is concerned with problems encountered in field surveys. Besides measurements on dry rocks, investigations on ultramafic rocks that exhibit high permittivity and large loss tangent and nonlinear behavior in dry and moist rocks and minerals, have been singled out for study, especially for developing measuring techniques. Experience with these techniques is useful for studying the electrical characteristics of moist rocks, including anisotropic effects, conductive overburden materials, the separation of copper‐rich sulfides from iron‐rich sulfides, and graphite, coal, frozen soils, and ice in permafrost. A better understanding of the complex behavior of electrical currents in rocks and sulfides will lead to improvements in equipment design, techniques, and interpretation in exploration geophysics.