¹Béatrice Luais, ²Guillaume Florin
Earth and Planetary Science Letters 672, 119663 Link to Article [https://doi.org/10.1016/j.epsl.2025.119663]
¹Université de Lorraine, CNRS, CRPG, Nancy, F-54000, France
²Laboratoire Magmas et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, F-63000, Clermont-Ferrand, France
Copyright Elsevier

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.

¹Dustin Trail, ²Mélanie Barboni, ¹Miki Nakajima, ^1,3Kim A. Cone
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.10.043]
¹Department of Earth & Environmental Sciences, University of Rochester, Rochester, NY, USA
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
³Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
Copyright Elsevier

The Moon underwent extensive internal and external modification following the crystallization of a global magma ocean. However, the isotopic record from this formative period remains poorly constrained. Here, we present the first comprehensive study of coupled δ18OVSMOW and δ30SiNBS28 compositions in 67 lunar zircons from Apollo 14 samples, spanning crystallization ages from 4.34 to 3.93 Ga, a critical 400-million-year window of early lunar history. The zircons exhibit remarkably uniform isotopic compositions throughout this interval, with δ18O = 5.66 ± 0.23 ‰ (1 s.d.) and δ30Si = –0.30 ± 0.16 ‰ (1 s.d.). These values are consistent with both bulk silicate Moon estimates and whole-rock analyses, suggesting minimal isotopic fractionation between zircon-forming melts and their source reservoirs. Importantly, we find no systematic isotopic variations with age, sample, or crystallization temperature. This isotopic uniformity persisted despite large-scale geological processes, including crustal formation, basin-forming impacts, and possible mantle overturn. This implies that neither primary differentiation processes nor later reworking produced detectable Si or O isotope heterogeneities in the zircon source regions, at least within the nearside Procellarum KREEP Terrane. Taken together, these results are consistent with lunar silicate reservoirs being well mixed and isotopically equilibrated by ∼4.3 Ga within Fra Mauro, and possibly more broadly, setting a stringent constraint for models of lunar differentiation.