Simultaneous Measurements of the Compressional-Wave Velocity and the Electrical Conductivity in a Partially Molten Material.

Abstract

Geophysical Institute, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan Both the compressional-wave velocity and the electrical conductivity were measured on a partially molten material. An H2O ice and KCl aqueous solution system was used as an analog of partially molten Earth's materials; the melt has a triangular tube shape at the edge and corner regions of solid grains. Both the velocity and the conductivity showed discontinuous change at the onset of partial melting. A melt fraction less than 5% causes the conductivity to increase by 1.5-3 orders of magnitude, while the velocity decreases only a few percent. This result is consistent with the geometry and connectivity of melt in the KCl-H2O system. The large conductivity increase suggests that there will be a high-conductivity partially molten region where a low velocity anomaly is difficult to detect.