Characterization of mineral-solution interface and its implications for water-rock interactions

Olivine-water interface under hydrothermal conditions (600-790degC, 1kb) are characterized by SEM, XPS and hydrogen depth profiling using nuclear reaction. The near surface region is rich in H and depleted with Mg. The chemical shift of XPS peaks indicates structural reconstruction at the near surface. The present results and the previous studied indicate the formation of the hydrogen rich surface layer depends on various factors including mineral structure, solution composition and temperature. It is correlated with dissolution rate. Probably, permeation of water into mineral through defects or micropore space and diffusion in the permeating water are important processes in water-rock interactions. (author)