High precision oxygen three-isotope analyses of anhydrous chondritic interplanetary dust particles

Oxygen three-isotope ratios of three anhydrous chondritic interplanetary dust particles (IDPs) were analyzed using an ion microprobe with a 2 lm small beam. The three anhydrous IDPs show DO values ranging from )5& to +1&, which overlap with those of ferromagnesian silicate particles from comet Wild 2 and anhydrous porous IDPs. For the first time, internal oxygen isotope heterogeneity was resolved in two IDPs at the level of a few per mil in DO values. Anhydrous IDPs are loose aggregates of fine-grained silicates (£3 lm in this study), with only a few coarse-grained silicates (2–20 lm in this study). On the other hand, Wild 2 particles analyzed so far show relatively coarse-grained (‡ few lm) igneous textures. If anhydrous IDPs represent fine-grained particles from comets, the similar DO values between anhydrous IDPs and Wild 2 particles may imply that oxygen isotope ratios in cometary crystalline silicates are similar, independent of crystal sizes and their textures. The range of DO values of the three anhydrous IDPs overlaps also with that of chondrules in carbonaceous chondrites, suggesting a genetic link between cometary dust particles (Wild 2 particles and most anhydrous IDPs) and carbonaceous chondrite chondrules.