Kinetics of pressure solution creep in quartz: theoretical considerations

Abstract

The kinetics of pressure solution creep are formulated using chemical potentials generalized to nonhydrostatic states. Solving a coupling equation of diffusion and reaction on a spherical quartz grain with diameter d and grain boundary width w, the flow law of pressure solution creep is derived. As extreme cases, the flow law becomes: ϵ ̇ = (αν 2 SiO 2 KDw)(ν H 2O RTd 3) −1σ for the diffusion-controlled case and becomes: ϵ ̇ = (βν 2 SiO 2 κ +)(ν H 2O RTd) −1σ for the reaction-controlled case, where ϵ is strain rate, σ is deviatoric stress, ν is the molar volume, D is the diffusion coefficient through a wet grain boundary, K is the equilibrium constant, κ + is the rate constant of dissolution, R is the gas constant, T is temperature, and α and β are shape factors. Using the reaction constants determined by Rimstidt and Barnes (1980) and the grain boundary diffusion coefficients estimated by Nakashima (1995), the strain rate of pressure solution creep in metamorphic conditions for quartzose rocks is estimated as 10 −9∼13, 10 −8∼11, and 10 −7∼11 s −1 at 150, 250, and 350°C, respectively. These values, compared with the duration of regional metamorphism, suggest rapid pressure solution and dewatering in subduction zones followed by fluid-absent metamorphism.