The effect of deep weathering on geophysical exploration in Australia—A review

Abstract

Abstract A long period of weathering of the Australian continent and a subdued tectonic history for much of it has produced an ancient deeply weathered mantle over large areas. This mantle has had the effect of reducing geophysical signals from buried targets and also increasing the background (geological) noise in the data. This is particularly so for electrical methods of exploration. Mathematical modelling for various methods is made more difficult. However, the development of more sophisticated instruments, some with microprocessor control, digital recording, filtering and automatic stacking of data and, in particular, the development of transient (pulse) electrical methods, has allowed much better separation of target from weathered overburden anomalies. The discoveries at Elura (NSW) and Roxby Downs (SA) of bodies at depths of 100 m and 350 m, respectively, are excellent examples of the type of exploration which will probably become more common. Magnetic survey remains the most generally useful geophysical method in the exploration for metals. High resolution magnetic surveys are becoming more popular to aid mapping of lithology and structure (e.g. for gold).