The pressure dependence of Fe–Mg interdiffusion coefficients, as well as of the diffusion coefficients of the trace elements Ni and Mn in olivine, were determined from diffusion anneals carried out using oriented single crystals in multi-anvil presses. This was the first determination of the activation volumes for the diffusion of trace elements (Ni, Mn) in olivine. The results of isothermal polybaric (1673K, 6 to 12GPa) and isobaric polythermal (1623 to 1823K, 12GPa) sets of experiments were combined in order to constrain an internally consistent set of Arrhenius parameters for the diffusion processes. It was found that, within the uncertainty of the data, the diffusion rates of Fe–Mg, Mn and Ni were very similar to each other under all conditions. This was consistent with more detailed observations resulting from 1-atmosphere experiments (Petry et al., 2004). The apparent activation volumes, obtained using various fitting methods, lay between 4 and 7cm3/mol, but a value of 5.3cm3/mol (Misener, 1974; Farber et al., 2000), adequately described the pressure-dependence of the diffusivity of these elements in olivine over its entire stability range (in pressure) along the Ni–NiO fO2 buffer. The activation volume at constant fO2 was higher (about 7cm3/mol). At depths corresponding to the lowest stability of olivine (about 12GPa), the activation energies for diffusion were about 100kJ/mol higher than under ambient conditions.

Effect of Pressure on Fe–Mg, Ni and Mn Diffusion in (FexMg1−x)2SiO4 Olivine. C.Holzapfel, S.Chakraborty, D.C.Rubie, D.J.Frost: Physics of The Earth and Planetary Interiors, 2007, 162[3-4], 186-98