MEASUREMENTS OF ELECTRICAL CONDUCTIVITY OF BASALT AT TEMPERATURES UP TO 1500℃ AND PRESSURES TO ABOUT 20 KILOBARS

Abstract

The electrical conductivity of basalt was studied by means of the AC technique at temperatures up to 1500℃ and pressures to about 20 Kb. From the sharp changes in the slope of the conductivity curve, melting temperatures were determined. As pressure increases, the melting temperatures of dry basalt increase, and the melting intervals are shorter than those determined for the same sample by differential thermal analysis and the quenching method. Complete melting of dry basalt increases the electrical conductivity by a factor of about 10 at most not only at atmospheric pressure but also at high pressures up to about 20 Kb. The pressure effect up to about 20 Kb is small compared with the effect of temperature. Water pressure increases the electrical conductivity to a much greater extent than partial melting. Therefore, structure models of electrical conductivity for western Canada will be interpreted by the difference in water content.