The channelling of natural electric currents by orebodies

Abstract

Natural fluctuations of the magnetic field of the earth induce large scale electric currents to flow in the crust and upper mantle. The currents are commonly known as telluric currents, and where an inhomogeneity of high electrical conductivity exists these currents will preferentially tend to flow through it. On the regional scale of continent-wide induction such channelled currents are sometimes strong enough to be detected by the surface observation of their associated magnetic fields. This paper investigates the extent to which a measurable effect might occur on the physically smaller scale when the inhomogeneity is an orebody.