CHANGE IN VALENCE AND LATTICE ENVIRONMENT OF FE IONS DURING THE MELTING OF KIRCHSTEINITE (CAFESIO4)

Abstract

It is important to know the valence state and structure of iron ions in magmatic melts in order to understand the reactions controlling the redox environment of petrogenesis. The voluminous literature on Moessbauer spectroscopy of silicate glasses presents data on the effect of the composition of the system, the temperature, pressure and oxygen fugacity on the coordination and relationship of ions of di- and trivalent iron. This work was done on glasses generated from a mixture of oxides, often at temperatures much higher than the liquidus temperatures of the systems. The authors therefore investigate the state of iron ions in glasses prepared by melting minerals, as in that case one can describe the structural changes by direct comparison of data on the crystal and glass. In this report they present the results of Moessbauer and X-ray investigations of the behavior of iron ions in the melting of kirchsteinite (CaFeSiO4), a mineral with an olivine lattice.