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 mu m small beam. The three anhydrous IDPs show Delta 17O values ranging from -5 parts per thousand to +1 parts per thousand, 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 Delta 17O values. Anhydrous IDPs are loose aggregates of fine-grained silicates (=3 mu m in this study), with only a few coarse-grained silicates (220 mu m in this study). On the other hand, Wild 2 particles analyzed so far show relatively coarse-grained (= few mu m) igneous textures. If anhydrous IDPs represent fine-grained particles from comets, the similar Delta 17O 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 Delta 17O 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.