The influence of silica on reaction rates and molecular hydrogen (H2) generation during olivine hydrothermal alteration

Hydrothermal alteration of olivine greatly influences geodynamics and the recycling of volatiles (such as water and carbon) in subduction zones. Silica is an important component of geological fluids, and its influence on the hydrothermal alteration of olivine remains poorly constrained. In this study, we performed experiments at 300–515°C and 3.0 kbar (1 bar=105 Pa) by reacting well homogenized mixtures of olivine and silica powders with saline solutions (0.5 mol L−1 NaCl). Silica greatly influences the reaction pathways, reaction rates, and molecular hydrogen (H2) formation during olivine hydrothermal alteration. In experiments at 300°C and 3.0 kbar with mixtures of olivine and 10 wt