An unusual layered mineral in chondrules and aggregates of the Allende carbonaceous chondrite

Olivine-rich chondrules and aggregates in the Allende C3(V) carbonaceous chondrite are characterized by abundant opaque spherules of metal, sulphide and magnetite grains. This assemblage has been explained as resulting from the crystallization of immiscible metal-sulphide-oxide liquids, suspended as droplets within the chondrules¹. Petrographic evidence indicates a significant metasomatic effect in a highly oxidizing condition in a later cooled stage^2,3. We have found that an unusual Fe-, Ni-and O-rich layered mineral, related to serpentine, occurs within the opaque assemblage; it is formed by alteration of olivine. The textural and compositional features are clearly distinct from terrestrial phyllosilicates. This is the first report of a serpentine-related mineral in the Allende meteorite. Our observations suggest that aqueous conditions occurred in Allende before the final stage of meteorite formation.