LOW-TEMPERATURE THERMODYNAMIC PROPERTIES OF NATURAL BIOTITE

Abstract

The composition of biotite from igneous and metamorphic rocks reflects the chemical characteristics of the rocks and the P-T-fO2 conditions of their formation. Among the most important parameters of biotites are their total iron content, degree of oxidation, aluminum content, and alkali/aluminum ratio. Many authors showed that these parameters can be used for the characterization of the conditions of mica formation. Knowledge of the thermodynamic data for iron-bearing biotites of a certain composition with the known ratios of Fe2+/Fe3+ and Fe/Al together with experimental phase equilibrium data may help determine the conditions of formation of metamorphic and igneous rocks enriched in ferriferous biotite.