Calcium-aluminum-rich inclusions from enstatite chondrites: Indigenous or foreign?

The primary mineral assemblages and initial Al-26/Al-27 ratios of rare calc ium-aluminum-rich inclusions (CAIs) from enstatite (E) chondrites are simil ar to those of CAIs from other chondrite classes. CAIs from all chondrite c lasses formed under oxidizing conditions that are much different from the r educing conditions under which the E chondrites formed. Either CAIs formed at an earlier, more oxidizing epoch in the region where E chondrites ultima tely formed, or they formed at a different place in the solar nebula and we re transported into the E chondrite formation region.