Oxygen and Hydrogen Diffusion in Minerals

Abstract

This chapter provides a summary and review of experimentally determined oxygen and hydrogen volume diffusion in minerals. A very extensive and detailed review of stable isotope exchange processes including oxygen and hydrogen volume diffusion can be found in Cole and Chakraborty (2001) and a detailed review of hydrogen diffusion in minerals, especially nominally anhydrous minerals, can be found in Ingrin and Blanchard (2006). In addition, a detailed review of oxygen and hydrogen diffusion in silicate melts is provided by Zhang and Ni (2010), and oxygen and hydrogen diffusion rates can also be found in the chapters, in this volume, on specific minerals and mineral groups (e.g., Van Orman and Crispin 2010; Cherniak 2010). Interested readers are encouraged to refer to these reviews for additional information on oxygen and hydrogen diffusion in geological materials. In this chapter only volume diffusion through the crystal lattice will be considered. The majority of the experiments employed isotope tracers (e.g., 18O, 2H). The isotope diffusion of hydrogen in the nominally anhydrous minerals is regarded as an impurity tracer diffusion mechanism, and the effective diffusion coefficients obtained from the hydrogen uptake or extraction experiments correspond to chemical interdiffusion of different species. The relationship between the measured effective diffusivity and the hydrogen diffusivity is governed by the specific reaction involved (e.g., see Kohlstedt and Mackwell 1998). Elsewhere in this volume, a detailed outline and discussion of the experimental methods employed in diffusion studies is presented by Watson and Dohmen (2010). Therefore, only a brief overview of methods commonly employed for oxygen and hydrogen diffusion studies is presented below. ### Bulk exchange experiments #### Hydrothermal bulk exchange. Carefully sized powders of either natural or synthetic crystals of the mineral of interest are loaded into a sealed tube with a known amount of 18O and/or 2H- enriched water. …