Electrical conductivity anomalies and their relationship with the tectonics of South Australia

Summary. Geomagnetic variation studies have been conducted in the Gawler Craton and Adelaide Geosyncline of South Australia. The magnetometer stations extend from the coast up to the southern edge of the 1970 array of Gough, McElhinny & Lilley. The coast effect is the dominant feature of the data but use is made of the hypothetical event technique to identify two zones of telluric current concentration. Both of them appear to be associated with linear zones of enhanced electrical conductivity within the crust. The Southern Eyre Peninsula anomaly lies within the Gawler Craton and may identify a major fracture or shear in the upper crust. The conductivity anomaly within the Adelaide Geosyncline appears to be the continuation of the Flinders anomaly discovered by the 1970 array study. It correlates well with the arcuate fold pattern of the Southern Flinders Zone of the Geosyncline and with the local pattern of seismicity. In both anomalies the enhanced conductivity is probably caused by saline waters within fractured crustal rocks.