Mahan, Brandon, Moynier, Frédéric, Siebert, Julien, Gueguen, Bleuenn, Agranier, Arnaud, Pringle, Emily A., Bollard, Jean, Connelly, James N., and Bizzarro, Martin (2018) Volatile element evolution of chondrules through time. Proceedings of the National Academy of Sciences of the United States of America, 115 (34). pp. 8547-8552.

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Abstract

Chondrites and their main components, chondrules, are our guides into the evolution of the Solar System. Investigating the history of chondrules, including their volatile element history and the prevailing conditions of their formation, has implications not only for the understanding of chondrule formation and evolution but for that of larger bodies such as the terrestrial planets. Here we have determined the bulk chemical composition—rare earth, refrac- tory, main group, and volatile element contents—of a suite of chon- drules previously dated using the Pb−Pb system. The volatile element contents of chondrules increase with time from ∼1 My after Solar System formation, likely the result of mixing with a volatile-enriched component during chondrule recycling. Variations in the Mn/Na ratios signify changes in redox conditions over time, suggestive of decoupled oxygen and volatile element fugacities, and indicating a decrease in oxygen fugacity and a relative increase in the fugacities of in-fluxing volatiles with time. Within the context of terrestrial planet formation via pebble accretion, these obser- vations corroborate the early formation of Mars under relatively oxidizing conditions and the protracted growth of Earth under more reducing conditions, and further suggest that water and volatile elements in the inner Solar System may not have arrived pairwise.

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