A CHONDRULE ORIGIN FOR DUSTY RELICT OLIVINE IN UNEQUILIBRATED CHONDRITES

We address the origin of ''dusty,'' metal-bearing relict olivine grain s in chondrules. It has been suggested previously that these grains ma y be either primitive condensates or derived from a previous generatio n of chondrules. In this paper, we infer the original composition of d usty olivine grains, before they were reduced, and examine the possibi lity that they were derived from a previous generation of chondrules. Original compositions of dusty grains, including their estimated initi al FeO contents and their minor element contents, match closely with c ompositions of olivines from chondrules in unequilibrated chondrites. In addition, the cores of some dusty grains are unaltered, and the com positions of these cores are also consistent with a chondrule origin. Therefore, we conclude that a derivation from a previous generation of chondrules is a plausible origin for these relicts. Although alternat ive origins, such as condensates or interstellar grains, cannot be rul ed out on the basis of the available data, chondrules are an obvious s ource, and we suggest that this is the most likely interpretation. If this is the case, it is additional evidence for the importance of recy cling of chondrule material in the chondrule-forming region.