A relict refractory inclusion in a ferromagnesian chondrule from the Allende meteorite

Abstract

CARBONACEOUS chondrites such as the Allende meteorite are composed of abundant ferromagnesian chondrules and (Ca, Al)-rich inclusions (CAIs) embedded in a fine-grained matrix. The chondrules were formed by melting of pre-existing solid precursor materials¹, whereas CAIs formed either by direct condensation from the nebular gas or by high-temperature processing of solids in the nebula². These two components usually appear as discrete objects in chondrites, and are believed³ to have formed independently before agglomeration of the chondrite parent bodies. However, elemental analyses of some Al-rich chondrules^4–8 suggest that there was a refractory component—such as CAIs—in the chondrule precursor material. We report here the discovery of a ferromagnesian chondrule from the Allende meteorite that contains an intact CAI fragment. This finding confirms that some CAIs coexisted with the precursor material of ferromagnesian chondrules, and helps to constrain the timing of the formation events of these two components.