Heating events in the nascent solar system recorded by rare earth element isotopic fractionation in refractory inclusions

Creators: Hu, J. Y.; Dauphas, N.; Tissot, F. L. H.; Yokochi, R.; Ireland, T. J.; Zhang, Z.; Davis, A. M.; Ciesla, F. J.; Grossman, L.; Charlier, B. L. A.; Roskosz, M.; Alp, E. E.; Hu, M. Y.; Zhao, J.

Abstract

Equilibrium condensation of solar gas is often invoked to explain the abundance of refractory elements in planets and meteorites. This is partly motivated, by the observation that the depletions in both the least and most refractory rare earth elements (REEs) in meteoritic group II calcium-aluminum–rich inclusions (CAIs) can be reproduced by thermodynamic models of solar nebula condensation. We measured the isotopic compositions of Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb in eight CAIs to test this scenario. Contrary to expectation for equilibrium condensation, we find light isotope enrichment for the most refractory REEs and more subdued isotopic variations for the least refractory REEs. This suggests that group II CAIs formed by a two-stage process involving fast evaporation of preexisting materials, followed by near-equilibrium recondensation. The calculated time scales are consistent with heating in events akin to FU Orionis– or EX Lupi–type outbursts of eruptive pre–main-sequence stars.

Additional Information

© 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 16 April 2020; Accepted 16 November 2020; Published 6 January 2021. CAI samples were provided by P. R. Heck and the Robert A. Pritzker Center for Meteoritics and Polar Studies at the Field Museum (FG-FT-3, 4, 6, 7, 8, 9, and 10) and S. Simon (TS32) (see full catalog numbers in Table 1). Discussions with F. M. Richter, P. R. Heck, N. X. Nie, C. Chen, H. Zeng, S. M. Aarons, and A. W. Heard were greatly appreciated. We are grateful to H. Palme and an anonymous reviewer for thorough and constructive reviews, which greatly improved the quality of the manuscript. This work was supported by NASA grants NNX17AE86G, NNX17AE87G, 80NSSC17K0744, and 80NSSC20K0821; NSF grant EAR-2001098 to N.D.; and NASA grant 80NSSC17K0251 to A.M.D. Author contributions: J.Y.H., N.D., and F.L.H.T. conceived the study; F.L.H.T. and L.G. selected the samples in a previous study; F.L.H.T. characterized, extracted, and digested the samples; J.Y.H. established the measurement protocol, carried out the isotopic analyses of REEs, did the modeling, and wrote a first draft of the manuscript under the guidance of N.D.; Z.Z. and J.Y.H. carried out the isotopic analyses of Ti; A.M.D. helped with thermodynamic modeling; F.J.C. provided some input on the possible astrophysical setting for CAI formation; N.D., F.L.H.T., R.Y., T.J.I., and J.Y.H. developed the FPLC system; B.L.A.C. helped with comparison of the data with previous Sr isotopic results; N.D., M.R., E.E.A., M.Y.H., and J.Z. helped with interpretation of previously published Eu NRIXS data. All authors contributed to data interpretation and writing of the manuscript. Competing interests: N.D., F.L.H.T., R.Y., T.J.I., and J.Y.H. are inventors on a patent related to this work filed by Orlab Chromatography LLC (no. US9884266B2, filed on 8 July 2014, published on 8 January 2015). The authors declare no other competing interests. Data and materials availability: The OL-REE series of isotope standards used in this study are stored at the Origins Laboratory, The University of Chicago and are available upon request from J.Y.H. or N.D. All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

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