Béatrice Luais, Guillaume Florin
Earth and Planetary Science Letters, 672, 119663
Voir en ligne : https://doi.org/10.1016/j.epsl.2025.119663
The warm, reduced, volatile-poor inner Solar System and cold, oxidized, volatile-rich outer Solar System are characterized by neutron-poor and neutron-rich isotopic anomalies, respectively. Nucleosynthetic isotopic anomalies recorded in meteorites, asteroidal bodies, and planets are thus indicative of their regions of formation. However, whether these reservoirs evolved as closed systems or underwent some degree of intermixing remains uncertain. Here, we report new high-precision mass-dependent germanium isotopic compositions revealing that carbonaceous chondrites exhibit higher and more variable δ74/70Ge values than ordinary chondrites, defining a strong continuous trend in both Ge concentrations and isotopic compositions. We highlight that similar strong correlations with matrix mass fraction occur across all chondrite groups, but that the non-carbonaceous (NCC, inner Solar System)–carbonaceous (CC, outer Solar System) dichotomy observed in ε48Ca, ε 54Cr, ε 50Ti, and ε64Ni nucleosynthetic anomalies is maintained. In the δ74/70Ge vs. ε 48Ca, ε 54Cr, ε 50Ti, and ε 64Ni spaces, two distinct mixing lines are resolved within both the NCC and CC reservoirs, between NCC and CC-type chondrules and CI-type matrix. Extending the NCCsingle bondCI chondrite correlation to primitive achondrites, main-group pallasites, and the mantles of Mars and Earth reveals that these silicate reservoirs plot away from the OCsingle bondCI mixing lines, highlighting the possible existence of a neutron-poor matrix component in the inner Solar System. Overall, the Ge isotopic systematics of the Solar System suggest that chondrules and their matrices did not form exclusively in a single reservoir, but rather formed throughout the inner and outer Solar System.
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