Transport properties obtained from magnetotelluric sounding of a granite

The magnetotelluric (MT) technique is a deep exploration method that is undergoing rapid development. Theoretical investigations concerning new exploitations of the electromagnetic wavefield (e.g. Lee et al. 1989) form one leading edge to which field data acquisition and processing are gradually responding. Despite such developments it is probably true that even conventional MT is a poorly understood technique. Case histories using conventional methods and resolutions can, therefore, provide a useful foundation for assessing the role of the technique in present and future exploration programmes.