An evolutionary condensation sequence revealed by mineralogically-distinct nodules in fine-grained, spinel-rich inclusions from CV3 chondrites: Implications for the genetic links between different types of non-igneous refractory inclusions

Fine-grained, spinel-rich inclusions (FGIs) are abundant in CV3 chondrites and exhibit textures compositions that consistent with a condensation origin. We have conducted systematic investigation of FGIs from two reduced chondrites, Leoville Efremovka, which has revealed number microscale variations the primary mineralogies nodules, provided further insights into origins FGIs. Nodules individual vary size their mineralogical zonation, resulting significant heterogeneity within each FGI. In FGIs, nodules small (typically < 10 μm) commonly form clusters, whereas larger (often > 20 either embedded mass or occur as shells surrounding clusters nodules. The difference is associated mineralogy: typically contain single few spinel/melilite grains cores, while cores large polycrystalline more compact. Transmission Electron Microscope observations show complex microstructures, including presence fine-grained spinel, close association Al-Ti-diopside crystallographic orientation relationship between adjacent clinoenstatite diopside grains. Our microstructural indicate disequilibrium played an important role formation some previous studies. Specifically, spinel-cored melilite-dominant well different occurrences spinel (in on periphery), suggest these occurred under conditions, may be caused by physical isolation condensates. textural compositional similarities other types non-igneous CAIs: hibonite-spinel fluffy Type A CAIs. mineralogically-distinct micrometer-sized counterparts CAIs record evolutionary sequence solar nebula. It likely formed same gaseous reservoir, but at times. mechanism condensates probably controlled accretion behavior sizes, observed distribution patterns On hand, mineralogically-zoned Mg-rich core Ca-rich mantle, can better explained condensation, followed transport to region protoplanetary disk.