Some recent magnetic induced‐polarization developments—Part II: Survey results

Abstract

Because magnetic induced‐polarization (MIP) field measurements reflect polarization current both in the interior of polarizable bodies and in the external medium (return current), an interesting variety of response types, depending upon the distribution of ground conductivities and polarization, has been observed in field surveys. Most of the survey results obtained to date have been amenable to interpretation on the basis of the theoretical and model studies, although some unexplained aspects exist. One interesting type of response is that associated with massive, highly conducting sulfide bodies. These often show reversed polarity anomalies because they provide a channel for the return polarization current due to disseminated sulfides which are adjacent to them. The massive sulfide bodies themselves do not produce appreciable induced‐polarization (IP) effects due to their high‐conductivity contrast with surrounding rocks. The results of ten MIP surveys over known metallic mineral deposits are presented from Australia, and one is presented from Canada. Both time‐domain (transient) and frequency‐domain (complex conductivity) measurements have been made on different deposits.