In situ Si isotope and chemical constraints on formation and processing of chondrules in the Allende meteorite

Chondrules in undifferentiated meteorites are former silicate melt droplets of variable texture and composition. Although widely studied, the chondrule formation mechanisms conditions that explain all properties chondrules yet to be identified. To further constrain processes affected solar nebula on meteorite parent body, we determined situ Si isotope ratios major trace element compositions minerals types sizes from Allende CV3 chondrite. The δ30Si ranges −1.28 ± 0.19 0.55 0.20‰ (2SE). shows no direct relationship with or distance between core rim. Barred olivine-rich record highest δ30Si, likely because faster cooling less interaction isotopically light nebular gas. Type I non-porphyritic some porphyritic show overall higher compared type II chondrules. Furthermore, Mg-rich olivine pyroxene have systematically Fe-rich pyroxene. silicates (Mg-rich) (Fe-rich) may explained by gas nebula. We envision a combination equilibrium kinetic fractionation Fe-poor (such as forsterite, anorthite, enstatite mesostasis) orthopyroxene. Petrographic evidence suggests enrichment Fe highly altered at rims was caused hydrothermal alteration body. Therefore, correlation might serve an indicator for extent secondary processing minerals. sum these observations occurred oxidation originally reduced, metal-rich chondrules, both later Remaining 30Si depleted contributed isotopic composition matrix silicates. favours settings rather than asteroid impacts.