Several years of accumulating complex resistivity spectral measurements have indicated that there are still many unexplored areas in induced polarization surveying that need to be investigated for a more complete understanding of the polarization process. In addition to providing mineral discrimination capabilities, complex resistivity spectra can be used to differentiate between various barren host rock responses, to facilitate the complete removal of electromagnetic coupling, and to identify pipeline, fence, and various other cultural coupling effects. Results of field measurements are presented in an effort to demonstrate the utility of and necessity for making complete spectral measurements for serious geophysical interpretation. Correlation of field measurements with laboratory measurements on core samples from the same area demonstrates that strong electromagnetic coupling can be accurately removed from complete spectra without removing the important rock response. Recent field and laboratory measurements indicate that most, if not all, induced polarization responses attributed to magnetite are not really due to this mineral but can be traced to a host rock alteration response. Also, characteristic host rock signatures for sulfide environments appear to vary according to locality and type of deposits making it impossible to provide a universal set of signatures for sulfide deposits.
The effect of electrode contact resistance and capacitive coupling on complex resistivity measurements
