2009 年 38 巻 2 号 p. 33-38
The electrical conductivity of the major upper mantle minerals, namely, olivine, wadsleyite and ringwoodite is reviewed in this paper. There are mainly three electrical conduction mechanisms for the major upper mantle minerals, namely, ionic, hopping and proton conductions. The charge carriers for these mechanisms are electron hole in Fe ion, vacancy in the Mg site and proton, respectively. An electron hole in an Fe ion forms a small polaron, which causes a higher activation energy (1.4-1.6 eV) than mere transfer of electron holes (0.1 eV). Hopping conduction is the most essential conduction mechanisms for the major upper mantle minerals. Ionic conduction is a dominant conduction mechanism only at high temperatures, because ionic conduction has high activation energy (4.3 eV for olivine). Proton conduction could play an important role because the major upper mantle minerals can contain certain amount of water. Proton conduction contributes more at lower temperatures because of its low activation energies (0.5-1.0 eV). If the mantle minerals contain large amount of water (>0.1 wt%), proton conduction can be a dominant conduction mechanism of the mantle minerals even at high temperatures.