ELECTROLYTE ACTIVITY: ITS EFFECT ON INDUCED POLARIZATION

Abstract

Induced polarization (IP) occurs at metal‐solution and membrane‐solution interfaces in rock materials. Minerals producing significant IP include sulfides, magnetite (electrode polarization), and some clays (membrane polarization). In mineral exploration, one is concerned with the distinction between these two phenomena; either may be significant, but together they are confusing. While no practical means has yet been devised to do this in the field, one may exist. The present study represents the first stage in an attempt to elucidate the phenomena and to make such a distinction. There is no means of studying directly the effect of variables on polarization at a single interface or cell in a rock if those variables also affect rock resistivity. Hence, one must speak of rock IP independently of individual cell IP. Data reported herein reflect rock IP. Temperature and pressure appear to have little effect on IP of specimens studied so far; further investigation may show that they are important in some geologic environments. Changes in electrolyte activity greatly influence rock IP. Membrane and disseminated electrode polarization decrease while connected (veined) electrode IP increases with increasing activity. This fact may be useful in interpretation of depth variations of IP in the field, particularly over oxidizing sulfide bodies.