Some overvoltage field trials with a new type of equipment

Abstract

The paper reports some field studies of the induced polarization effect over known sulphide ores and graphitic schists in the northern part of Sweden, carried out in 1963–1964. There is employed a new instrumentation technique by which it has been found possible to obtain more undisturbed overvoltage decay curves in the field. The purpose of the investigation was to study the diagnostic value of the decay curve characteristics for ore and mineral prospecting. It has not thus been found possible to distinguish between different sulphide ores and graphitic schists. But the observations illustrate the limitation of the conventionally utilized characteristics of the IP effects. And they have led to suggest a new way of presenting IP effects, i. e. by a ratio term, enabling more clearly to locate separately the ionic, respectively the electronic, conductors in the ground. The advantage of having both Self-Potential, Resistivity and Induced Polarization measurements integrated into the same prospecting system is emphasized as important, despite the fact that in some cases dissemination zones can be located by resistivity measurements alone.