An experimental study of the influence of graphite on the electrical conductivity of olivine aggregates

Presence of graphite is one of the mechanisms to explain enhanced electrical conductivity. Because the conductivity of graphite is highly anisotropic and the connectivity of graphite depends strongly on the geometry of the crystals, the key issue is the geometry of graphite in a rock including their crystallographic orientation and the shape of graphite crystals. We explored the role of graphite on electrical conductivity in olivine‐rich aggregates. To obtain well‐defined results, we conducted an experimental study at high pressure and temperature conditions. Olivine aggregates containing diamonds were annealed to transform diamond to graphite with nearly equilibrium morphology. Graphite formed by the transformation from diamond has thin disk‐shape morphology, the plane being the highly conductive (0001) plane. When the concentration of graphite exceeds the percolation threshold (~ 1 wt%), electrical conductivity is significantly enhanced. Some of the observed high conductivity regions may represent regions of high concentration of graphite. Key Points Graphite formed from diamond at high P,T has thin disk‐shape morphologyFor graphite to enhance conductivity depends on volume fraction and geometryHigher carbon content may explain the observed high conductivity in some regions