ULTRAREFRACTORY INCLUSION FROM THE H3 ORDINARY CHONDRITE CHUG CHUG 072

Ultrarefractory Ca,Al-inclusion (UR CAI) CC072-1 was found in the ordinary H3 chondrite Chug Chug 072 (CC 072). This meteorite is a polymict microbrecia containing a chondrule-bearing clast and a carbonaceous chondrite clast in addition to the UR inclusion. CC072-1 has nodular texture with mineralogical zoning. The core of nodules consists of a erovskite+warkite+kangite assemblage, and the mantle mostly consists of Sc-rich davisite+spinel. This mineralogical zoning suggests that this UR CAI was formed by gas-solid reactions in a cooling nebular gas in the CAI-forming region. Enrichment in FeO of all minerals of the UR CAI most likely resulted from metasomatic alteration and thermal metamorphism in an asteroidal setting. This UR CAI is isotopically heterogeneous: spinel is 16O-rich, whereas warkite, perovskite, and davisite are 16O-depleted. It seems likely that CC072-1 originated in a 16O-rich gas of approximately solar composition, and subsequently experienced post-crystallization O-isotope exchange with an aqueous fluid. Since Δ17O of aqueous fluids in type 3 ordinary chondrites determined from Δ17O of secondary magnetite and fayalite are ~ +5‰, significantly higher than the Δ17O of 16O-depleted minerals in CC072-1, the oxygen isotope exchange experienced by CC072-1 could have occurred prior to incorporation of the UR CAI into the CC072 parent asteroid, possibly in a carbonaceous CM-like chondrite parent body. Then after migration and impact events the UR CAI was incorporated in the H3 chondrite during brecciation.