Significance of iron-rich silicates in the Mezö-Madaras chondrite

Several chondrules in the Mezo-Madaras chondrite contain the disequilibrium mineral assemblage: ferrous olivine--magnesian pyroxene--merrihueite (approximately (K> or = Na)2 (Fe> or = Mg)5 Si12O30) plus or minus metallic nickel-iron. The ferrous silicates in this assemblage were probably formed by introduction of FeO into an earlier igneous assemblage which consisted or enstatite or clinoenstatite, a magnesian analogue of merrihueite, and silica. Textural and chemical evidence indicate that this alteration of the chondrules took place before they were incorporated in the chondrite. (Author).