Changes in surface area and morphology and the mechanism of forsterite dissolution

Abstract

Scanning electron microscope (SEM) photographs of olivine grains shown that dissolution of olivine may occur more rapidly on some surfaces than on others and that initial dissolution of freshly crushed grains occurs primarily along lattice imperfections such as dislocations or cleavage planes. The SEM photographs generally do not show the presence of thick or continuous residual or precipitated layers which might render the dissolution reaction diffusion controlled. The specific surface area of olivine grains increased greatly during initial dissolution due to formation of etch features. However, despite the increased surface area the rate of dissolution decreased during the experiments. These observations suggest that some assumptions underlying derivation of the diffusion controlled models are invalid for olivine dissolution and suggest that dissolution is controlled by rates of surface reactions.