Novel technique to control oxygen fugacity during high-pressure measurements of grain boundary conductivities of rocks.

This paper describes the development and application of a novel method for the measurement of grain boundary electrical conductivity of rock at high temperature and pressure. In this method, the metal electrodes, the corresponding metal shielding case, and the sleeves are altered in order to appropriately adjust and monitor the oxygen fugacity in a sample cavity in a high-pressure apparatus. As an example, a series of oxygen buffers including Fe(3)O(4) + Fe(2)O(3), Ni + NiO, Fe + Fe(3)O(4), Fe + FeO, and Mo + MoO(2) was selected and tested, and the oxygen fugacity was confirmed as adjusted during the process of electrical conductivity measurements. Application of this method provides a powerful means of restricting specific thermodynamic conditions at high temperature and pressure.