摘要：Graphical abstractDisplay OmittedHighlights•Ionic conductivity in olivine has a positivefO2dependence.•Ionic mechanism has large contribution to the upper mantle conductivity profile.•High conductivity in the asthenosphere can be explained by olivine only.AbstractThe oxygen fugacity (fO2) may affect the ionic conductivity of olivine under upper mantle conditions because Mg vacancies can be produced in the crystal structure by the oxidization of iron from Fe2+to Fe3+. Here we investigated olivine ionic conductivity at 4 GPa, as a function of temperature, crystallographic orientation, and oxygen fugacity, corresponding to the topmost asthenospheric conditions. The results demonstrate that the ionic conductivity is insensitive tofO2under relatively reduced conditions (fO2below Re-ReO2buffer), whereas it has a clearfO2-dependence under relatively oxidized conditions (fO2around the magnetite-hematite buffer). The ionic conduction in olivine may contribute significantly to the conductivity anomaly in the topmost asthenosphere especially at relatively oxidized conditions.
