Magnetotelluric Studies across the Tasman Geosyncline, Australia

Four magnetotelluric soundings have been made across the Tasman Geosyncline, a major tectonic feature of south-east Australia. The sites of the soundings lie in a line traversing the syncline approximately 150 km apart. Reliable data were procured for each site covering the period range from 103 to 104 and following the usual methods of magnetotelluric interpretation, information on electrical conductivity is obtained at upper mantle depths. The conclusion is drawn that at these depths, the conductivity is higher, by an order of magnitude, beneath the geosyncline than to the west of it. This result is interpreted as indicating higher temperatures which are due to, or perhaps cause, the tectonic activity which has characterized the geosyncline, and which is still evident in seismicity studies of the present day. A heat flow contrast to the west of the geosyncline is predicted.