Diffusion-limited crystal growth in silicate systems: similarity with high-pressure liquid-phase sintering

Abstract

In natural partially molten silicate systems as well as in material systems, textural adjustments occur to reduce the total free energy of the system, including those contained in surfaces and interfaces. To assess the effect of water content on textural equilibration and crystal growth in solid–liquid silicate systems we conducted wetting-angle and diffusion experiments. These experiments provide information about the extent of the interfacial energy reduction associated with dissolution along grain edges. The wetting angle exhibits a constant median value of ca. 50°, reflecting overall reduction of interfacial energy of the two-phase silicate system during melt penetration. The nature and extent of the breakdown reaction, the proportion of the new phases, and the crystallographic development are related to the initial water content. The solid was initially impermeable, so the liquid–solid equilibration involves dissolution producing crystallite rearrangements on a local scale, with immediate and nearby reprecipitation. Because the process of dissolution/precipitation requires transport of the atomic components, liquid penetration, and the rate-limited growth of the new phases are found to be consistent with capillary-driven diffusion.