ELECTRICAL-CONDUCTIVITY OF POLYCRYSTALLINE OLIVINE CONTAINING A SILICATE GLASS

The complex impedance of a polycrystalline sample of San Carlos olivin e including 5 vol% of a synthetic silicate glass containing sodium, ma gnesium, and iron has been measured as a function of temperature under controlled oxygen fugacity at a.c. frequencies of 10(2), 10(3), and 1 0(4) Hz. Below approximately 800-degrees-C, the conductivity of the sa mple is at least 5 to 10 times higher than that of single crystal and polycrystalline San Carlos olivine, respectively, and has an activatio n energy half that of the single crystal. The sample conductivity incr eases dramatically as a function of the measurement frequency. Hystere sis and time-dependent changes in sample conductivity are observed abo ve the liquidus of the glass (approximately 900-degrees-C). The data s uggest that the electrical conductivity of partially molten samples is characterized by parallel conduction of the solid and melt phases and is a sensitive indicator of melt distribution as well as the kinetics of melt re-equilibration.