WATER SATURATION AND HIGH ELECTRICAL CONDUCTIVITY IN LOWER CONTINENTAL CRUST

Recent geomagnetic depth sounding and magnetotelluric measurements indicate that in young tectonically active continental areas there is a layer of high electrical conductivity at depths of about 20 to 40 km. Comparison with published experimental results shows that the lower crust in these areas will have the required high conductivity if it is water saturated. In stable shield areas, the crust has become dehydrated through metamorphic processes and the high conductivity layer is absent. Geomagnetic depth sounding and magnetotelluric measurements should provide valuable information on the present stage of development, and on the conditions at depth, in the crust for different continental areas. © 1968.