Porphyritic olivine chondrules with enstatite chondrite isotopic composition as a main building block of Earth

The nature and origin of the Earth's building blocks remain intensely debated. While enstatite chondrites (ECs) were formed from a reservoir with an isotopic composition of major elements similar to that of the Earth, they nevertheless exhibit significant chemical differences. Specifically, the Earth is enriched in refractory elements and depleted in moderately volatile elements compared to ECs. By reevaluating the budget of rare earth elements in enstatite chondrites, we show that EC chondrule precursors correspond to early condensates formed in the inner protoplanetary disk. Taking condensation models into account, we propose that these condensates consist primarily of olivine, which was subsequently transformed into enstatite due to gas-melt interactions during chondrule formation. We show that the accretion of the Earth from olivine-rich EC chondrules, which underwent shorter gas-melt interactions compared to those present in ECs, satisfactorily reproduces its chemical ratios (i.e., Mg/Si, Al/Si, Na/Si, Ti/Si, Ca/Si) and oxygen isotopic composition. This difference in the duration of gas-melt interactions in the protoplanetary disk had thus major consequences on the chemical composition of the planetesimals accreted by planetary embryos. Our approach thus addresses the chemical divergence between Earth and ECs without altering their isotopic compositions, while also supporting planet formation models involving large embryos formed in the inner protoplanetary disk.