We have studied porphyritic olivine-rich chondrules of the carbonaceous chondrite Kaba (CV3) by combined highresolution X-ray mapping, quantitative electron microprobe analyses, and oxygen isotopic analyses via secondary ion mass spectrometry. These chondrules contain smaller inner-chondrule olivine grains characterized by low refractory element (Ca, Al, Ti) contents, and larger outer-chondrule olivine crystals that are enriched in refractory elements and show complex Ti and Al oscillatory zonings. Our O isotopic survey revealed that many of the inner-chondrule olivines are 16 O-richer than the relatively isotopically uniform outer-chondrule olivines. Inner-chondrule olivine crystals-only a minority of which may be derived from earlier generations of chondrules-are likely mostly inherited from nebular condensates similar to AOAs, as they share similar isotopic and chemical features and are thus interpreted as relict grains. Still, being 16 O-poorer than most AOAs, they may have experienced significant exchange with a 16 O-poor reservoir prior to chondrule formation (even if to a lesser degree than relicts in CM2 and ungrouped C2 chondrites). Subsequent incomplete melting of the relict grains produced Ca-Al-Ti-rich melts that engulfed the remaining relict olivine grains. The complex Ti and Al zoning patterns in outer chondrule (host) olivines, in particular the systematic dilution near the margin, seem to reflect gas-melt interactions (with e.g. SiO (g), Mg (g)) which also buffered the O isotopic composition of chondrule hosts. Together, these results demonstrate that important episodes of recycling of nebular condensates occurred in the solar protoplanetary disk.

FeO-poor (type I) porphyritic chondrules formed by incomplete melting of solid dust precursors via a yet-elusive mechanism. Two settings are generally considered for their formation: (i) a nebular setting where primordial solids were melted, e.g. by shock waves propagating through the gas and (ii) a collisional planetary setting. Here we report a method combining high-current electron microprobe X-ray mapping and quantitative measurements to determine the chemical characteristics of relict olivine grains inherited from chondrule precursors. We find that these olivine crystals are Ca-Al-Ti-poor relative to host olivine crystals. Their variable  17 O, even in individual chondrule, is inconsistent with derivation from planetary interiors as previously argued from 120° triple junctions also exhibited by the