The diffusion of H in San Carlos olivine single crystals was studied by performing experiments under hydrothermal conditions. The experiments were carried out at 1.5GPa, 1000C for 1.5h in a piston cylinder apparatus, or at 0.2GPa, 900C for 1 or 20h in a cold-seal vessel. Polarized Fourier transform infrared spectroscopy was used to quantify the hydroxyl distributions. At high temperatures, hydrogenation was dominated by the coupled diffusion of protons and octahedrally coordinated metal vacancies. From the experimental data, Arrhenius expressions were determined:

D(m2/s) = 3.2 x 10-5exp[-204(kJ/mol)/RT]

for diffusion along [100] and [010], and

D(m2/s) = 0.04 exp[-258(kJ/mol)/RT]

for diffusion along [001].

S.Demouchy, S.Mackwell: Physics and Chemistry of Minerals, 2006, 33[5], 347-55