DETERMINATION OF THE RATE-LIMITING MECHANISM FOR QUARTZ PRESSURE DISSOLUTION

Abstract

A model of quartz pressure dissolution via grain boundary diffusion through an adsorbed water layer, incorporating the effects of silica precipitation kinetics is used to derive a simple expression indicating whether densification by pressure dissolution is rate-limited by mass transport of precipitation kinetics. Using values of the diffusivity of thin films derived from pressure dissolution experiments, it is shown that at temperatures normally associated with pressure dissolution in sedimentary environments kinetics will be rate-limiting for most fine-grained sandstones and for coarser sediments, where quartz precipitation is inhibited. However, due to the strong temperature dependence of the quartz precipitation rate constant, it is demonstrated that at the elevated temperatures used in pressure dissolution experiments (typically >300°C) surface reactions are unimportant for particles > 2–6 μm in size.