Chemical kinetics of water‐rock interactions

TLDR

The study reviews recent literature on water‑rock interaction kinetics, extends data to a quantitative weathering framework, and examines the kinetic importance of the water‑rock ratio. A framework combining laboratory dissolution experiments and thermodynamics yields a rate law up to equilibrium, which, when coupled with fluid‑flow treatment, models weathering profiles such as bauxite formation from nepheline syenites. Experimental data confirm the silicate mineral stability series, indicate that carbonic‑acid hydration limits water‑rock interactions, and validate the kinetic significance of the water‑rock ratio.

Abstract

The recent literature on the kinetics of water‐rock interactions is reviewed. The data are then extended to provide a quantitative framework for the description of weathering and alteration. The available experimental data on dissolution of silicates verifies quantitatively the usual mineral stability series in sedimentary petrology. The rate of hydration of carbonic acid is shown to be a possible limiting factor in water‐rock interactions. The framework is developed to enable use of laboratory dissolution experimental results and thermodynamics to arrive at a rate law applicable up to equilibrium and therefore applicable to natural systems. The kinetic justification for the significance of a water‐rock ratio is discussed. With a proper treatment of fluid flow, the equations are applied to the weathering profile leading to the development of bauxites from nepheline syenites.