OXYGEN RESERVOIRS IN THE EARLY SOLAR NEBULA INFERRED FROM AN ALLENDE CAI

Ultraviolet Laser microprobe analyses of a calcium-aluminum-rich inclu sion (CAI) from the Allende meteorite suggest that a Line with a slope of exactly 1.00 on a plot of delta(17)O against delta(18)O represents the primitive oxygen isotope reservoir of the early solar nebula. Mos t meteorites are enriched in O-17 and O-18 relative to this Line, and their oxygen isotope ratios can be explained by mass fractionation or isotope exchange initiating from the primitive reservoir. These data e stablish a Link between the oxygen isotopic composition of the abundan t ordinary chondrites and the primitive O-16-rich component of CAIs.