Electrical conductivity of partial molten carbonate peridotite

In order to investigate the effect of carbonate-content in partial melt on bulk conductivity under high pressure, electrical conductivity measurements were performed on carbonate melt-bearing peridotites using a Kawai-type multi-anvil apparatus. The starting materials were composed of spinel lherzolite (KLB1) with small amounts of dolomite (1 and 3 wt.%). To obtain various melt fractions, annealing experiments were performed at different temperatures above 1400 K at 3 GPa. At low temperatures (⩽1500 K), the conductivity was distinctly higher than that of carbonate-free peridotite and close to that of the carbonatite melt-bearing olivine aggregates. Although the sample conductivity increased with increasing temperature, the rate at which the conductivity increases was small and the conductivity approached that of silicate melt-bearing peridotite. CO2 concentration in the partial melt decreased with increasing annealing temperature. Thus, the small increase of the conductivity with annealing temperature is attributed to a decrease of the melt conductivity due to a decrease in carbonate content in the partial melt. As the carbonate concentration in the melt decreases, the estimated melt conductivity approaches that of the basaltic melt. Therefore, conductivity enhancement by the carbonate-bearing melt is very effective at temperature just above that of the carbonate peridotite solidus.

► We investigated electrical conductivity of partially molten carbonate peridotite.
► On the solidus, the conductivity was markedly higher than that of carbonate-free peridotite.
► Electrical conductivity is not markedly increased by higher melting degree.
► The moderate increase is attributed to a decrease in carbonate content in the partial melt.
► The conductivity in the upper mantle is enhanced by very small degree of melting.