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Fig. 9. Depiction of the sequence and processes of Si isotope fractionation in chondrule silicates from the Allende meteorite. The chondrule formation process produced melt from which early silicates with high δ30Si and Mg/Fe crystallized. Because of evaporation of chondrule melt, the nebular gas became slightly enriched in 28Si and Fe. Caused by density differences, chondrules were separated from the gas and associated dust, which may have formed a tail behind partially or fully crystallized chondrules. This early-formed ‘main chondrule population’ comprises non-porphyritic and porphyritic metal-poor and metal-bearing type I chondrules. Remaining evaporated material in the tail was more oxidized and richer in volatiles compared to the solidifying non-porphyritic and porphyritic type I chondrules. Interaction of this gas (specifically Fe, SiO, and O) with 30Si- and Mg-rich chondrules may have formed type II chondrules and minerals with lower δ30Si and Mg/Fe. Finally, parent body metamorphism may have overprinted these processes locally in altered chondrules.