Origin of native silicon and iron silicides in the Dhofar 280 lunar meteorite

Abstract

Native silicon and iron silicides were studied in the Dhofar 280 lunar anorthositic meteorite representing an impact-melt breccia. Such rocks are widespread in the highland crust of the Moon. It was established that cryptocrystalline objects containing native silicon are close in composition to the silicon monoxide SiO. Experimental data demonstrate that this compound is the main component of the vapor forming during vaporization of an anorthitic melt. It is suggested that the formation of native silicon was related to the condensation of SiO from an impact-derived vapor cloud. Reducing conditions are determined by the mass-fractionation of silica monoxide and oxygen in the expanding vapor cloud in the gravity field of the Moon. Gaseous SiO may be condensed directly into a solid phase or a mixture of silicon with silica. The condensed SiO phase incorporated into an impact melt should be decomposed into silicon and silica. Interaction of Si, SiO, and SiO 2 solid condensates with an impact melt could lead to the observed enrichment of the surrounding liquid in silica. The formation of iron silicides is provided by the reaction of native silicon with FeO presenting in an impact melt. The other iron source could be a meteoritic component, which is identified in silicides by elevated Ni contents. Obtained mineralogical and experimental data show that metallic silicon can be obtained under lunar conditions by distillation of anorthositic melts and can be used for production of solar batteries to provide lunar settlements with energy.