Electromagnetic Response of a Medium Loaded with Coated Conductive Particles

We consider a model of a mineralized ore zone in the form of a dissemination of metal particles of spheroidal shape. To account for electrochemical effects, the surface of the particles exhibits an interface impedance that can be any specified function of frequency. A quasi-static analysis is used, which is justified because the particles are electrically small. Explicit expressions for the induced dipole are given for the prolate spheroidal geometry and the oblate case follows a simple transformation. The result is exact only for the case where the angular dependence of the interface impedance has a special form. A general expression is given for the transient response of the particles when the primary field is abruptly terminated. The resulting decay of the secondary field is shown to be a strong function of the particle shape.