Zinc isotope anomalies in primitive meteorites identify the outer solar system as an important source of Earth’s volatile inventoryOPEN ACCESS
Paul S. Savage, Frédéric Moynier, Maud Boyet
In Press, Journal Pre-proof, Available online 1 July 2022
• Chondrites exhibit a range of Zn isotopic anomalies compared to Earth.
• Earth’s Zn inventory is distinct from both CC and NC meteorites.
• 30% of Earth’s Zn must have CC (outer solar system) origin.
• Zinc isotopes reveal an outer solar system origin for volatile elements.
• ~6% of Earth’s material must have a CC (outer solar system) origin.”
“The source of and timing of delivery of the volatile elements to Earth is a question that is fundamental to understanding how our planet evolved. Here, we show that primitive meteorites have resolved mass-independent Zn isotope anomalies from the terrestrial reservoir. Carbonaceous chondrites (CC), likely originating from the outer Solar System are distinct from non-CC, and Earth is intermediate between these two components. Modelling based on these data indicates that around 30% of Earth’s budget of Zn and other moderately volatile material derives from the participation of 6% of CC-like materials during Earth’s accretion, with the remaining coming from NC meteorites. This implies that, despite the relatively minor mass of Earth thought to derive from CC-like material, the CC component of Earth was relatively and significantly volatile-enriched; this is in line with the observation that the terrestrial elemental abundance pattern of moderately volatile elements could be explained by a carbonaceous source, and with the carbonaceous chondrite-like isotopic budget of more volatile-rich material accreted later in Earth’s accretion history (e.g. Hg, Se, N, noble gases).”