Modelling the electrical conductivity of iron-rich minerals for planetary applications

In the framework of in situ exploration of planetary interiors, electromagnetic survey is one of the geophysical methods constraining the structure and composition of the mantle. One of the main parameters which governs the internal structure is the bulk iron content of the mantle. Unfortunately, the effect of iron on the electrical conductivity of mantle minerals is only known through a few high-pressure and high-temperature experiments. Reliable measurements on samples with different iron contents were reported for olivine, pyroxene, magnesiowustite and perovskite/magnesiowustite assemblage. In a first part, we parameterize the effect of iron on the electrical conductivity of these minerals. In a second part, we propose assumptions to extend this formulation to all minerals considered by the review of Xu et al. [2000b. Laboratory-based electrical conductivity in the Earth's mantle. J. Geophys. Res. 105, 27865-27875], in order to extrapolate the conductivity of terrestrial samples (i.e. with iron fraction close to 10%) to the conductivity of iron-rich minerals (up to 40%). In a third part, we apply this formulation to the computation of a synthetic electrical conductivity profile of the Martian mantle. The computed conductivity profile is 1-1.5 order of magnitude higher than terrestrial profiles, because of the higher iron content of the Martian mantle. This result highlights the possible application of electrical conductivity for constraining the composition of planetary mantles. (c) 2006 Elsevier Ltd. All rights reserved.