Magnetotelluric data have been obtained over the obscured contact between the Precambrian Willyama Complex and Palaeozoic, Mesozoic and Cainozoic sediments of the Murray‐Darling Basin. Major structural elements can be identified from the resulting resistivity pseudosections for two traverses to the northeast and to the south of Broken Hill. Resistivities exceeding 1000 ohm m are obtained for the Precambrian basement, contrasting with values in the range 1–200 ohm m obtained for the sediments of the Murray‐Darling basin. Two‐dimensional forward modelling suggests a semi‐vertical contact for these units consistent with previous magnetotelluric surveys in the same area. Resistivities of 100 ohm m in the lower crust are attributed to partial melting of hydrated granites at depths of 20–30 km.