Oxygen Isotopes of Anhydrous Minerals within Micrometeorites Show Connections to Volatile-Rich Parent Bodies

Chondritic materials retain isotopic signatures of protoplanetary disk gas and provide insights into disk chemistry and evolution during planet formation. We present mineralogy and oxygen isotope compositions of Antarctic micrometeorites (MMs) from the 1994 Cap Prud'homme collection, analysed by electron probe micro-analysis and nanoscale secondary ion mass spectrometry. Mineralogical and isotopic data link CP94-050 MMs to the carbonaceous chondrites (CCs), representing water-rich asteroidal and cometary materials. Olivine and pyroxene grains exhibit O isotopes that overlap with silicate inclusions in ordinary and carbonaceous chondrites. A majority of the minerals have values consistent with Type I and Type II chondrules (Δ ¹⁷ O ≈ -5 ‰ to +5 ‰), with the lowest Δ ¹⁷ O value being -30.5 ‰ (Particle #60), which is consistent with formation in the earliest, ¹⁶ O-rich disk reservoir. Particle #60 has the strongest affinities to olivine in CR chondrites, while particle #22 with an ¹⁶ O-rich composition has no definitive link to known chondrite types. Together, these results show that MMs sample a mixture of mostly hydrated outer-disk materials and, less abundant, refractory inner-disk silicates. The MMs in CP94-050 preserve primitive isotopic reservoirs despite post-accretionary alteration and offer critical constraints on the oxygen isotope reservoirs in the protoplanetary disk.