Introduction to IP

Induced polarization, or IP, is a measure of a delayed voltage response in earth materials. The IP effect is caused by a current-induced electron transfer reaction between electrolyte ions and metallic-luster minerals, a measurement of the electrical energy storage capacity of the earth. By passing an induced current into the ground and measuring the change in voltage with respect to time, or changes in phase at a given frequency with respect to a reference phase, the IP effect can be determined.

To produce an IP effect, fluid-filled pores must be present, since the rock matrix is basically an insulator. The IP effect becomes evident when these pore spaces are in contact with metallic-luster minerals, graphite, clays or other alteration products. IP effects make the apparent resistivity of the host rock change with frequency - generally the rock resistivity decreases as the measurement frequency increases.