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 2μm small beam. The three anhydrous IDPs show Δ ¹⁷O 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 Δ ¹⁷O values. Anhydrous IDPs are loose aggregates of fine-grained silicates (≤3μm in this study), with only a few coarse-grained silicates (2-20μm in this study). On the other hand, Wild 2 particles analyzed so far show relatively coarse-grained (≥ few μm) igneous textures. If anhydrous IDPs represent fine-grained particles from comets, the similar Δ 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 Δ 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.