New high-pressure Fe-Ti oxide minerals in the Shergotty Martian meteorite: Feiite, Fe2+2(Fe2+Ti4+)O5, liuite, FeTiO3, and tschaunerite, (Fe2+)(Fe2+Ti4+)O4

Abstract

High-pressure oxides like perovskite-type FeTiO₃, CaTi₂O₄-type Fe₂TiO₄, and ferrous-ferric oxides that form polysomes between wüstite and CaFe₂O₄-type Fe₃O₄ are potential carriers of Fe, Ti, and other transition metals in the mantle and may play an important role in the redox budget of the deep Earth. Here, we report the occurrence of three of these phases as the new minerals: feiite (Sr₂Tl₂O₅-type Fe²⁺₂(Fe²⁺Ti⁴⁺)O₅), liuite (FeTiO₃ with a GdFeO₃-type perovskite structure), and tschaunerite (CaTi₂O₄-type (Fe²⁺)(Fe²⁺Ti⁴⁺)O₄), along with wangdaodeite (LiNbO₃-type FeTiO₃) in a transformed ulvöspinel clast entrained in a shock melt pocket in the Shergotty Martian meteorite. We show that reaction between the shocked ulvöspinel precursor and melt occurred at pressures between 20 and 25 GPa. The high-pressure Fe-, Ti-minerals lost Fe and O to the surrounding shock melt in exchange for Si, Mg, and Ca. Concentrations of Si and Mg in all of these clast phases and of Na in liuite are significant. They substantiate chemical interaction of the clast with melt during the shock event and highlight potential elemental distributions in complex Fe- and Ti-rich lithologies at pressures of the deep transition zone to shallow lower mantle.