Australian Exploration Geophysics—Current Performance and Future Prospects1
The roles of temporal and spatial noise in Australian geophysics are outlined. Of the two, temporal noise is more amenable to suppression without increasing the cost of geophysical surveys, whereas the reduction of spatial noise is either labor- or computer-intensive. Up to 1976 the ability to see deep targets in Australia was limited by temporal noise in ground electromagnetics (EM) and radiometrics, and by spatial noise for induced polarization (IP), magnetics, and gravity. Consequently, the greatest opportunities for rapid technological advance existed for the first two techniques.
The exploitation of deep targets was made possible through the development of a new ground EM instrument, SIROTEM. The r.m.s. noise in the field data was decreased tenfold compared to contemporary instruments by more efficient use of the time domain. Surveys across two moderately difficult geophysical targets—the massive sulfide deposits at Elura and Teutonic Bore—yield anomalies that are 38 and 20 times greater than the ambient noise at 10 msec. It is predicted that the Elura deposit would be detectable with the presently marketed SI ROTEM if the upper boundary were at a depth of 150 m. A high-current version would detect the Elura target at a depth of 210 m with a 100 by 100 m loop, or at 240 m for a 200 by 200 m loop. Survey costs of A$12.50 per station, or A$500 per sq km for a first pass reconnaissance survey are reported.
Figures & Tables
The energy and mineral resources of the vast Pacific basin and its neighboring land areas play a vital role in meeting the ever-growing needs of society worldwide. Building on the foundation of a highly successful conference held in 1978, this volume contains 51 of the 135 papers presented there. Subjects included are general and specific in nature--oil, gas, and coal resources; geothermal fields, uranium; tin; evaporites, trace elements; water resources; magma energy and fuels from magma. Geological and geophysical techniques, and also the new tool of remote sending for petroleum and minerals exploration are represented. Tectonics, structure fundamentals, subsurface hazards, international treaties and the law of the deep sea are discussed. Seventeen countries and regions are represented in these papers: Thailand, Nicaragua, the United States, Japan, Peru, Antarctica, El Salvador, Australia, Mexico, Taiwan, New Zealand, China, Chile, Indonesia, Canada, and the Pacific Ocean.