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

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Science Advances  06 Jan 2021:
Vol. 7, no. 2, eabc2962
DOI: 10.1126/sciadv.abc2962
  • Fig. 1 Abundances and stable isotopic fractionations of REEs ordered by increasing refractoriness (from the least refractory on the left to the most refractory on the right).

    (A) Abundances of REEs in seven fine-grained CAIs with group II REE patterns [table 2 in (15)] normalized to Sm abundance and chondrites (7). Orange, green, and blue shades are least refractory, moderately refractory, and most refractory REEs, respectively. Each symbol corresponds to one CAI. The dashed line is the average abundance of seven CAIs for each REE. (B) Isotopic fractionations of REEs in the same seven CAIs (Table 1). The dashed line is the average isotopic fractionations of the seven CAIs analyzed. Note that one CAI with a flat REE abundance and isotopic pattern (TS32) is not plotted here (Table 1). See Table 1 caption and Eq. 1 for details on the δφ notation.

  • Fig. 2 Relationship of stable isotopic fractionations of REEs.

    (A) Correlation of isotopic fractionations Eu versus Sr in seven CAIs with group II pattern. (B) Ce and Sm versus Nd. (C) Dy versus Gd. (D) Yb versus Eu. See Table 1 caption and Eq. 1 for details on the δφ notation. The REE data are from Table 1, while the Sr data are from (16).

  • Fig. 3 Equilibrium isotopic fractionations of Eu.

    (A) Calculated reduced partition function ratios (in ‰/amu) of Eu compounds as a function of temperature. (B) Equilibrium isotopic fractionation between gas and solid phases of Eu as a function of temperature. See text for details.

  • Fig. 4 Trajectories of chemical depletion and isotopic fractionation in the evaporation (left) and condensation (right) stages considered to explain the composition of group II CAIs (see text and the Supplementary Materials for details).

    Schematics of the models envisioned for evaporation (A) and condensation (B). (C) Gd and (E) Dy isotopic fractionations and depletions during closed-system evaporation for different heating rates. (D) Eu and (F) Yb isotopic fractionations and depletions during closed-system condensation for different cooling rates. The labels on the curves are the heating rates (evaporation) and cooling rates (condensation) used in the calculations.

  • Fig. 5 Schematics of group II REE fractionation in CAIs.

    (A) Stage 1: Nebular dust with chondritic proportions of the REEs evaporates in an undersaturated medium, which leaves behind an ultrarefractory residue and produces vapor depleted in the heavy most refractory REEs that are also characterized by light isotope enrichments. (B) Stage 2: The vapor from stage 1 partially condenses. The highly refractory (HREEs except Tm and Yb) and moderately refractory (LREEs and Tm) are completely condensed. The least refractory REEs Eu and Yb remain in the gas and are not completely condensed. The condensation during that stage occurs in near-equilibrium conditions, resulting in minimal isotopic fractionation for Eu and Yb.

  • Table 1 Stable isotopic fractionations of REEs in a geostandard and CAIs.

    The δφE values are per mil/amu variations relative to terrestrial standards (OL-REEs) calculated using Eq. 1 applied to 142Ce/140Ce, 146Nd/144Nd, 152Sm/148Sm, 153Eu/151Eu, 158Gd/156Gd, 164Dy/162Dy, 168Er/166Er, and 174Yb/172Yb ratios.

    Isotopic fractionation (%/amu)
    SampleCAI
    name
    δϕCe#*δϕNd#*δϕSm#*δϕEu#*δϕGd#*δϕDy#*δϕEr#*δϕYb
    BCR-20.02±0.0110−0.01±0.02150.00±0.0190.01±0.0340.02±0.03100.02±0.038−0.05±0.0280.02±0.05
    TS320.24±0.061−0.03±0.054−0.01±0.062−0.19±0.052−0.02±0.032−0.02±0.073−0.02±0.1320.04±0.07
    ME-3364-25.2FG-FT-30.01±0.049−0.14±0.019−0.09±0.065−1.09±0.051−0.89±0.031−1.04±0.071−1.00±0.021−0.33±0.07
    ME-2639-16.2FG-FT-40.81±0.04121.1±0.0180.8±0.063−0.01±0.052−0.61±0.032−0.58±0.062−2.89±0.111−0.12±0.07
    ME-2639-49.7FG-FT-6−0.03±0.029−0.57±0.085−0.37±0.062−0.42±0.021−1.03±0.073−1.67±0.043−2.02±0.051±
    ME-2639-51.1FG-FT-70.42±0.039±0.07±0.065−0.58±0.051−1.28±0.033−1.64±0.072−2.24±0.021−0.66±0.07
    AL3S5FG-FT-80.51±0.019−0.02±0.0380.07±0.0190.04±0.112−2.26±0.019−3.07±0.019−1.89±0.1120.01±0.05
    AL4S6FG-FT-9−0.82±0.019−0.93±0.0211−0.97±0.0290.73±0.046−1.05±0.075−1.10±0.0270.08±0.046−0.32±0.01
    AL8S2FG-FT-100.35±0.055−0.16±0.083−0.03±0.051−1.03±0.111−0.35±0.072−0.53±0.041−3.63±0.051±
    ME-2639-16.2FG-FT-40.96±0.0750.68±0.0480.88±0.0650.03±0.064−0.57±0.036−0.55±0.026−2.90±0.112−0.12±0.05
    AL3S5FG-FT-80.70±0.018−0.01±0.01150.11±0.01110.13±0.063−2.28±0.0210−3.08±0.028−1.88±0.112−0.05±0.15
    AL4S6FG-FT-9−0.62±0.075−0.87±0.0113−0.84±0.0270.82±0.063−1.05±0.194−1.15±0.0650.01±0.115−0.32±0.02

    *Number of measurements.

    †Replicates subjected to substantial loss of REEs during Mo chemistry and not used for data interpretation.

    Supplementary Materials

    • Supplementary Materials

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

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

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