During an Electromagnetic survey, using the principle of induction, an electric current of known frequency and magnitude is pulsed through a large transmitter loop generating a primary magnetic field. The magnetic component of an EM field penetrating through ground induces alternating currents or “eddy currents” to flow within the conductor in the presence of a conducting orebody. The “eddy currents” generate their own secondary EM field distorting the primary field. The subsequent measuring of the response occurs as it propagates through the subsurface. The response differs in phase, amplitude, and direction. The ratio of the magnitudes of the primary and secondary currents is proportional to the terrain conductivity.

Ground Electromagnetic techniques are proficient in direct detection of conductive sulfide deposits, in which large conductivity contrasts exist between the orebodies and host rocks or overburden cover. EM surveys rely on the response of the ground to variations in electric and magnetic forces where the target is moderately to highly conductive. The depth of penetration of an EM field depends upon its frequency and the electrical conductivity of the medium through which it is propagating. The differences between transmitted, and received EM field reveal the presence of a conductor. Providing information on its geometry and electrical properties. Conductivity and resistivity are the inverse of each other. Resistive zones will return a weak response whereas conductive zones will return a strong response. These changes are detected by receivers as data which is then processed to provide crutial information about the conducting material in terms of geometry and intensity.