The quantification of the effect of hydrogen on the kinetics of Fe-Mg interdiffusion in olivine was discussed. It was found that diffusion couples composed of crystals with Mg/ (Mg+Fe) ratios of 0.91 and 0.83 were annealed under water-saturated conditions at T = 1373 K and P = 300 MPa. It was observed that the resulting interdiffusivity was approximately one order of magnitude larger thatn that measured under anhydrous conditions. Analysis shows that the enhancement in diffusivity in the presence of water results from an increase in the concentration of cation vacancies associated with the introduction of high concentrations of protons as point defects into the olivine structure.
Bibliographical noteFunding Information:
This research was supported by the NSF Grant No. EAR-0106981 and by a postdoctoral fellowship (for one of the authors T.H.) from the Japanese Society for the Promotion of Science. A critical review by Steve Mackwell combined with detailed discussions with Saswata Hier-Majumder and Steve Mackwell greatly improved this manuscript. This letter was completed while one of the authors (D.L.K.) was a Moore Visiting Scholar at the California Institute of Technology.
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