On the Relationship Between CAI Evolution and Chondrule Formation

The relationship in time and space between CAl formation on the one hand, and chondrule formation on the other is not well understood. It appears that at least compact, coarse-grained CAl were once largely molten. They must have been very depleted in volatiles at that time. However, as now found in Allende they show extensive alteration to volatile rich minerals such as nepheline and sodalite. I have previously argued, partly on the basis of the ubiquitous presence of these volatile rich minerals also in chondrules and matrix, that this alteration probably took place on the Allende parent body (Housley, 1985).