RANGE OF MASS TRANSFER THROUGH THE CONTACT BETWEEN A METAPELITE AND A METAMAFIC ROCK

Abstract

The best sources of information on the range over which mass transfer occurs in the course of metamorphism are data from the zones of contact (interface zones) between rocks that differ strongly in composition, but contain common components. The concentration gradients at their interfaces are generating gradients of the chemical potentials across these interfaces, which then lead to countercurrent flows of matter (mass transfer). We found instances of these phenomena in Salgelen (Tuva ASSR) when studying the relationships between kyanite-containing schist and amphibolite. The data presented unambiguously indicate that there was a chemical reaction between the metapelites and metamafites. The thickness of the reaction zone, as determined ranges from 5.5 to 8.5 cm. The counter-current transport of the albite and anorthite components occurs over the same range. Thus, we have obtained the first specific figures for the range of mass transfer through the contacts between metapelites and mafites, have estimated the duration of the mineral generation process, and have determined the effective diffusion coefficients of the albite and anorthite components of the rocks.