Radiogenic chromium isotope evidence for the earliest planetary volcanism and crust formation in the solar system

Abstract Erg Chech (EC) 002 is a meteorite with andesitic composition, potentially recording the lava crystallization and crust formation of its parent body. Nucleosynthetic Cr isotope composition (ε54Cr = −0.35 ± 0.06) for EC 002 suggests a non-carbonaceous region of the solar system, and possibly represents the crustal composition of the brachinite parent body. The 53Mn-to-53Cr decay system shows it crystallized at 4566.6 ± 0.6 Ma, i.e. 0.7 ± 0.6 Ma after solar system formation (only considering the cogenetic matrix fractions with similar ε54Cr values). This age represents the earliest recorded evidence for planetary melting and volcanism in the solar system, suggesting that the planetary crust formation occurred very early, only within the first few hundred thousand years of solar system history. However, the 53Mn-53Cr age does not overlap with 26Al-26Mg dating results, which might indicate that non-carbonaceous achondrites have lower initial 26Al/27Al than the canonical value defined by refractory inclusions in carbonaceous chondrites.