Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

摘要

At 1.0—4.0 GPa and 1123—1473 K and under oxygen fugacity-controlled conditions (Ni+ NiO, Fe + Fe3O4, Fe + FeO and Mo + MoO_2 buffers), a YJ-3000t Model six-anvil solid high-pressure apparatus and a Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (10~3—10~6 Hz), the electrical conductivity of the sample isof great dependence on the frequency; (2) with the rise of temperature ( T), the electrical conductivity (sigma) will increase, and the Arrenhius linear relationship is established between Ig sigma and 1/T; (3) under the control of oxygen buffer Fe + Fe_3O_4, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase, with the activation energy and activation volume of the sample estimated at (1.25 ± 0.08) eV and (0.105 ± 0.025) cm~3/mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and (5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.