Chapter 10 - Electromagnetic Properties of Rocks and Minerals

Abstract

The physical properties of rocks, which affect the propagation of the electromagnetic field, are electrical conductivity, dielectric permittivity, and magnetic permeability. In this chapter, we discuss these physical properties from three viewpoints: 1) the physical phenomena which cause the properties to behave as they do, 2) the values of these physical properties for rocks as they exist in the earth, and 3) the way in which these properties respond to environmental conditions and how they correlate with other physical and geological properties of rocks. We note also that, the electrical properties depend on many factors, some environmental, like temperature and pressure, and others which reflect the character of the rock, such as composition. We also introduce a phenomenon called induced polarization, associated with the current flow in the rocks. It is important to have a quantitative method, which would allow us to calculate the bulk conductivity of a complex rock formed by a mixture of conductive minerals and a host rock. This problem is solved using the methods of effective-medium theory. The properties of large-scale geoelectrical structures of the Earth, including the oceans and the atmosphere, are summarized as well.