The down-hole magnetometric resistivity (DHMMR) method

Abstract

The down-hole magnetometric resistivity method (DHMMR) is a pseudo-DC grounded dipole geophysical survey technique which allows absolute direction to a conductor from a borehole to be established. Anomalies produced by elongated block conductors are similar in shape and can be modelled in a similar way to gravity anomalies produced by block-shaped bodies having a density contrast. The anomalies are therefore simpler in shape than TEM anomalies and are easier to recognize in areas of geological complexity. The DHMMR technique is faster and more directional than down-hole TEM but has poorer resolution of conductor size and shape, and hence its ideal role is as a complement to down-hole TEM surveys. Case histories from two volcanogenic base metal prospects, near Charters Towers, Queensland, demonstrate the directivity of the method in the search for off-hole massive sulphides.