Possible compositional effects on the electrical conductivity of olivine: A preliminary study

Volatile sensitive probes of the upper mantle, such as magnetotellurics, are being developed to overcome insensitivities in seismic and gravity subsurface mapping as part of an effort to identify the location of deeply buried ore deposits, in addition to more broadly understanding mantle temperature and water contents. An understanding of the conductivity of mantle minerals is an essential prerequisite to the full interpretation of magnetotelluric data. Current proton conduction models for simple mineral systems, such as olivine, show large discrepancies. The material used for these determinations, San Carlos peridotite, is not a single mineral phase and may have compositional variations. This could be one of the origins of these discrepancies. To test this hypothesis, a sample of San Carlos olivine was taken and separated out the mineral components using a combination of electrostatic rock disaggregation, magnetic susceptibility as well as manual separation. The separated fractions were characterised using petrography. Impedance data were collected as a function of temperature and pressure in a multi-anvil press from both the separated olivine material and the original mixture. Comparison of these values with literature data has been made.