ABSTRACT

Routine EPMA analyses of homogeneous amphiboles in amphibolites indicate significant compositional variation between sections with two cleavages and those with a single cleavage parallel to the c axis. Sections with two cleavages are enriched in SiO₂, MgO, MnO and CaO relative to sections with a single cleavage which are enriched in Al₂O₃, FeO_(total), TiO₂, Na₂O, and K₂O (i.e. ∑ of tschermakiteedenite substitutions). The degree of compositional variation between the different amphibole sections may, in part, be related to the extent of equilibrium attained in the rocks during recrystallization.