FeO-rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

Abstract

We report the mineralogy and oxygen isotopic compositions of FeO-rich silicates in the Sahara 97159 EH3 chondrite. This component is referred to as FeO-rich because it contains substantially more FeO than the characteristic FeO-poor silicates in the highly reduced enstatite meteorites. These FeO-rich silicates are mostly low-Ca pyroxene (Fs535) and their compositions suggest an origin under more oxidizing conditions, like those for the ordinary chondrites. However, the mafic silicates in ordinary and carbonaceous chondrites are dominantly olivine, and the FeO-rich silicates in the E chondrites are less commonly olivine. The oxygen isotopic compositions of the FeO- rich silicates are indistinguishable from those of FeO-poor silicates in Sahara 97159. These observations suggest that both the FeO-rich silicates and the FeO-poor silicates in EH chondrites formed from the same oxygen reservoir where redox conditions varied widely.