Abstract: Australian Geophysics--Current Performance and Future Prospects

K. G. McCracken

The Australian continent poses some difficult problems for the exploration geophysicist. The existence of a thick oxidized layer (in many places of high electrical conductivity) over many mineralized areas has been a major impediment. Electrical and electromagnetic techniques exhibit high false-color rates, and they frequently have failed to respond to buried mineralization as a result of the screening effect of the overburden. A research and development program has been designed to alleviate these problems. The initial work has concentrated on techniques for the conduct of detailed surveys of targets selected by regional surveys. Theoretical and experimental studies showed that a fifty-fold improvement in the sensitivity of electromagnetic surveys could be obtained by ca eful optimization to the Australian situation. A series of three field prototypes of an instrument were built, and tested over 20 test sites throughout Australia. Clear detection of an orebody buried below a 100-m thick 10-ohm m oxidized zone has been demonstrated. On the basis of these tests, it is predicted that the instrument, now known as Sirotem, will be extremely effective in exploration of the zone between 100 and 200 m below surface. Field tests have demonstrated the utility of the method, and can predict its false-alarm rate. Sirotem shows that a modest research and development program, devoted to the optimization of a technique, can result in a major improvement in the geophysical tools available to the exploration industry. CSIRO believes that other areas of hard- and soft-roc geophysics will be amenable to such optimization based on the Australian environmental model.

AAPG Search and Discovery Article #90962©1978 AAPG 2nd Circum-Pacific Energy and Minerals Resource Conference, Honolulu, Hawaii