An appraisal of the VLF ground resistivity technique as an aid to mineral exploration

To assist the Department of Industry Mineral Reconnaissance Program (DIMRP) limited research has been undertaken to provide guidelines on new geophysical prospecting systems, field techniques and general exploration methodology. A short study has been made of the ground VLF resistivity (VLF-R) method to assess its potential for mineral prospecting and geological mapping. Field trials confirm that the method is well suited for mapping broad mineralised zones, flat lying conductors of limited lateral extent, or abrupt changes in conductivity associated with geological contacts. In resistive terrains the method offers distinct operational advantages over galvanic resistivity methods. The principal disadvantages of the technique relate to interpretational ambiguities associated with the complex behaviour of surface impedance at VLF and the fact that the operator has no effective control over the depth of investigation. Theoretical model studies show that too small and too large a penetration can both result in non-detection of a resistive target, but that excessive penetration will not seriously affect the resolution of conductive targets.