Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions

The lead-lead isochron age of chondrules in the CR chondrite Acfer 059 is 4564.7+/-0.6 million years ago (Ma), whereas the lead isotopic age of calcium-aluminum-rich inclusions (CAIs) in the CV chondrite Efremovka is 4567.2+/-0.6 Ma. This gives an interval of 2.5+/-1.2 million years (My) between formation of the CV CAIs and the CR chondrules and indicates that CAI- and chondrule-forming events lasted for at least 1.3 My. This time interval is consistent with a 2- to 3-My age difference between CR CAIs and chondrules inferred from the differences in their initial Al-26/Al-27 ratios and supports the chronological significance of the Al-26-Mg-26 systematics.