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Recycled selenium in hot spot–influenced lavas records ocean-atmosphere oxygenation

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Science Advances  23 Sep 2020:
Vol. 6, no. 39, eabb6179
DOI: 10.1126/sciadv.abb6179
  • Fig. 1 Selenium isotope and concentration data for marine sediments and mantle samples.

    (A) Colored boxes show the mean δ82Se [± 95% confidence interval (CI)] and Se contents (log-normal mean ± 1s) of sediments (N = 759) sorted by age intervals. The group means are calculated over sediment data averaged by depositional age (color-coded filled circles). Top: Gaussian kernel density estimations of sediment δ82Se for each age interval and average isotopic shift (dashed lines). (B) Igneous inventory (N = 87). The shaded field represents the depleted mantle estimate (Table 1). See section S1 for related references.

  • Fig. 2 Radiogenic isotope data for the studied MAR glasses.

    (A to D) Shown for comparison are a global compilation of MORB (44) and ocean island basalt (OIB; PetDB database) data and a more complete dataset for the entire MAR [S- and N-MAR basalts; precompiled by (15, 45)] and PAR sample suites [(21, 46) and references therein]. Solid lines denote the average composition of the Pacific and North Atlantic ambient depleted mantle (22). (D) 208Pb*/206Pb* is the time-integrated Th/U ratios [see (44)].

  • Fig. 3 δ82Se, δ34S, and 87Sr/86Sr data for MORB and the two-component mixing model.

    (A to C) The linear mixing lines are calculated using the most depleted MAR basalt or average Pacific depleted mantle (Table 1) as an anchor and the best-fit sediment end-member composition (δ82Se and Se content; A and C) from a Yorkfit regression (Isoplot; section S5). External uncertainty on each isotopic value is considered for the regression, and shaded area indicates 95% CI error envelope. The S-Sr isotopic variation (B) is shown for comparison [δ34S and S content of sediment in accordance with (15)]. Each tick mark on the mixing line denotes 0.1 weight % (wt %) sediment addition to the depleted mantle. See table S3 for model parameters. (C) also shows the frequency histogram of δ82Se and δ34S data (N = 41 and 44, respectively) across the MAR/PAR depleted MORB and Discovery plume-influenced MORB.

  • Fig. 4 Two-component mixing model with parameters from 1- to 2-Ga-old pelagic sediments.

    (A) displays segments of the mixing curves in (B) for the MORB data range. Symbols and the linear mixing array (±95% CI envelope) are the same as in Fig. 3. Black curves: Mixing trends using the well-constrained end-member parameters (δ82Se, 87Sr/86Sr, and Se/Sr of depleted mantle; 87Sr/86Sr and Sr content of sediment) and observed sediment averages (δ82Se and Se content) between mean and +1s. This indicates that the δ82Se and Se content of recycled sediment in the S-MAR source must be both at least close to the +1s upper bound of observed sediment averages. Thin blue/green mixing trends are calculated at fixed upper bound δ82Se of 1s and 2s above the mean; the curvature of the trend is controlled by R = (Se/Sr)sediment/(Se/Sr)mantle, which is calculated by error-weighted least-squares fitting of the mixing hyperbola (short-dashed lines correspond to ±95% CI on R). See table S3 and section S5 for model parameters and details.

  • Fig. 5 Selenium geochemical record and atmospheric oxygenation through time.

    (A to C) Sediment Se record and our model results for ~1- to 2-Ga-old recycled sediment/pyrite (boxes; mean ± 95% CI for δ82Se and 1s for Se content). Literature data are plotted as moving averages (large circles) of 11 individual sample data (small open circles) to highlight long-term evolution trends, with thick horizontal lines and shaded areas indicating mean ± 1s of each age interval. Igneous inventory: mean δ82Se (−0.09 ± 0.12‰) and Se content (0.1200.057+0.107 μg/g) of all mantle samples shown in Fig. 1. Right panel of (A): Gaussian kernel density estimates of sediment δ82Se data for Proterozoic and 1- to 2-Ga interval (N = 210 and 76, respectively). (D) Temporal evolution of juvenile continental crust volume after (47). (E) Schematic illustration of atmospheric oxygen models of Large et al. (7) and Lyons et al. (8).

  • Table 1 Selenium, sulfur, and radiogenic isotope compositions of the MAR glasses.

    Uncertainties on the sample δ82Se are 95% CI if the number of analyses ni > 3, or the 2sp external reproducibility of 0.08‰ (estimated for glass matrices) if ni ≤ 3. n = number of sample digestions (number in parentheses refers to ni). See the Supplementary Materials and Methods for the sample literature data.

    SampleTypeδ82Se (‰)nδ34S (‰)87Sr/86Sr143Nd/144Nd
    S-MAR
      EW9309 41D-1gDepleted MORB−0.06 ± 0.082−1.040.7032730.513048
      EW9309 40D-1g−0.18 ± 0.082 (3)−1.210.7029970.513033
      EW9309 34D-1gDiscovery anomaly−0.07 ± 0.081−1.230.7035440.512868
      EW9309 33D 1g−0.03 ± 0.082−0.580.7044750.512726
      EW9309 28D-1g−0.14 ± 0.082−0.830.7030280.513077
      EW9309 25D-1g+0.09 ± 0.084+1.050.7057280.512430
      EW9309 2D-1g−0.08 ± 0.043 (4)−0.140.7041270.512652
      EW9309 4D-3g−0.04 ± 0.082−0.620.7037620.512732
      EW9309 5D 5g−0.06 ± 0.082−0.420.7039760.512594
      EW9309 7D-1gLOMU anomaly+0.14 ± 0.083+0.030.7050930.512489
      EW9309 8D-1g−0.05 ± 0.083−0.480.7042860.512752
      EW9309 9D-3g−0.03 ± 0.046−0.500.7042840.512873
      EW9309 15D-1gShona anomaly−0.13 ± 0.082−1.380.7027410.513008
      EW9309 21D-1g−0.12 ± 0.082−1.060.7031150.512818
      EW9309 23D-1g−0.15 ± 0.082−0.910.7030580.512886
      EW9309 22D-3g−0.08 ± 0.081 (2)−0.590.7035760.512893
    N-MAR
      TR138 09D-2gDepleted MORB−0.17 ± 0.0810.702680.513203
      TR138 08D-1g−0.19 ± 0.0820.702510.513226
    Pacific depleted mantle*−0.16 ± 0.03−1.4 ± 0.50.70248 ± 0.000030.51311 ± 0.00001
    Depleted mantle−0.16 ± 0.03−1.4 ± 0.50.70211–0.702630.51310–0.51328

    *Average δ82Se (±95% CI, N = 27) and Sr-Nd isotopic ratios (±95% CI, N = 66) of PAR glasses [(21, 46) and references therein]; δ34S (±1s) from (46).

    †δ82Se (±95% CI, N = 31) is estimated using all the depleted MORBs from the MAR and PAR; δ34S (±1s) and Sr-Nd isotopic ratios from (15, 27, 48).

    Supplementary Materials

    • Supplementary Materials

      Recycled selenium in hot spot–influenced lavas records ocean-atmosphere oxygenation

      Aierken Yierpan, Stephan König, Jabrane Labidi, Ronny Schoenberg

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      • Supplementary Materials and Methods
      • Sections S1 to S6
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      • Tables S1 to S3
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