海洋リソスフェアにおける蛇紋岩化作用の速度：水熱反応実験からの制約

抄録

  Serpentinization is a hydration process that causes significant changes in physical and chemical properties of the oceanic lithosphere. Based on hydrothermal experiments, the reaction rates of serpentinization have been empirically obtained for typical reaction (i.e., Olivine+H₂O → Serpentine+Brucite) as a function of temperature and initial grain size of the reactant mineral. However, the rate equations used for these analyses take quite empirical forms, in which the solution chemistry (saturation state) is not taken into consideration; therefore, it is difficult to extrapolate the results to different conditions and to predict evolution of the fluid chemistry in the hydrothermal systems. Serpentinization reactions are characterized by coupled dissolution of primary minerals (Olivine, Pyroxenes) and formation of secondary minerals (Serpentine, Brucite, Talc, Magnetite); therefore, the rates of elementary reactions between individual minerals and solution will be required for estimating the rate of overall hydration reaction. I also discuss the effects of competitive processes among grain surface reactions, element diffusion, water supply and structural development during serpentinization.