Phosphate minerals in pallasite meteorites

Abstract

SummaryPhosphate minerals are widespread minor constituents of the pallasites. Both anhydrous primary and hydrous decomposition/alteration phosphates occur. The primary minerals, in decreasing order of abundance, are whitlockite, stanfieldite, and farringtonite, as well as a possibly new phosphate. The decomposition phosphates are compositionally heterogeneous and thus complex. Some may be new minerals. The phosphate minerals serve as the major repository for the alkali elements in pallasites, with individual crystals containing up to several percent of Na+K. Equilibrium established between coexisting phosphide and phosphate defines a relatively narrow range of ƒO2 values.