Pith. sign in

REVIEW 3 major objections 3 minor 81 references

Origin of moderately volatile elements in Earth inferred from mass-dependent Ge isotope variations among chondrites

T0 review · 3 major / 3 minor · reviewed 2026-08-15 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read The paper argues that germanium isotopes in Earth's mantle record a late influx of volatile-rich carbonaceous material delivered by Moon-sized embryos.

desk verdict Solid new Ge isotope data for chondrites, but the late-accretion story rests on an unmeasured core-formation fractionation that could erase the Ge–Zn distinction. read the letter →

arxiv 2505.06604 v1 pith:PMLMAQ4J submitted 2025-05-10 astro-ph.EP

Elias Wölfer , Christoph Burkhardt , Francis Nimmo , Thorsten Kleine This is my paper · ORCID
classification astro-ph.EP
keywords germaniumisotopesmoderatelyvolatileelementsbulksilicateEarthlateaccretioncarbonaceouschondritesenstatitecoreformationplanetary
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper uses new mass-dependent germanium isotope measurements ($\delta^{74/70}\mathrm{Ge}$) of carbonaceous and enstatite chondrites to identify the source of Earth's moderately volatile elements (elements condensing between roughly 1250 and 650 K). It finds that the germanium isotope composition of the bulk silicate Earth (BSE), $0.60\pm0.02$‰, is indistinguishable from a roughly 2:1 mixture of CI-chondrite-like and enstatite-chondrite-like germanium, meaning about 64% of the BSE's Ge came from carbonaceous (outer Solar System) material. Because germanium partitions strongly into metal, early-delivered Ge would have been removed to the core, so this signature records only the later stages of accretion. The carbonaceous fraction recorded by Ge is more than twice that recorded by zinc, which the authors interpret as the late-stage delivery of volatile-rich carbonaceous bodies to Earth, probably a few Moon-sized embryos. The result matters because it connects the volatile inventory of Earth to the dynamical timing of accretion.

What carries the argument

The central tracer is the mass-dependent germanium isotope ratio $\delta^{74/70}\mathrm{Ge}$, reported in permil relative to a reference standard and measured with a $^{70}\mathrm{Ge}$–$^{73}\mathrm{Ge}$ double spike. The argument is carried by two mixing relations: within carbonaceous chondrites, $\delta^{74/70}\mathrm{Ge}$ and Ge concentration correlate with matrix mass fraction and define a volatile-rich, isotopically heavy CI-like matrix endmember and a volatile-poor, isotopically light chondrule/non-matrix endmember; and at the scale of the whole Earth, the BSE value is treated as a mixture of enstatite-chondrite (non-carbonaceous, NC) and CI-chondrite (carbonaceous, CC) endmembers using the same lever-rule formula previously applied to nucleosynthetic isotope anomalies. The timing information comes from the preference of Ge for metal, quantified by the parameter $x_{95}$ (the fraction of Earth's mass after which the last 95% of an element was added to the mantle), which is about 0.4 for Ge, so the Ge isotope signature is windowed to late accretion. The paper's potential core-formation correction, estimated by scaling experimentally determined silicon metal-silicate isotope fractionation to germanium, is the main auxiliary input that sets the systematic uncertainty.

What would settle it

Measure the equilibrium germanium isotope fractionation between liquid metal and liquid silicate at about 3500 K, the temperature inferred from Ge partitioning during core formation. If $\Delta^{74}\mathrm{Ge}_{\mathrm{metal-silicate}}$ is near zero, the paper's preferred carbonaceous fraction of $0.64\pm0.16$ stands; if it approaches $-0.5$‰, the pre-core BSE would be too light to require a carbonaceous fraction much larger than zinc's, and the claimed late volatile-rich influx would not be resolvable. A second, independent check would be finding any non-carbonaceous chondrite with $\delta^{74/70}\mathrm{Ge} > 0.60$, which would remove the need for a carbonaceous endmember altogether.

Watch

Extended reading notes

Core claim

In its preferred model, the paper claims that the germanium isotope composition of the bulk silicate Earth (BSE) is a two-endmember mixture, with the non-carbonaceous endmember having the $\delta^{74/70}\mathrm{Ge}$ of enstatite chondrites ($-0.17\pm0.42$‰) and the carbonaceous endmember having the composition of CI chondrites, the most primitive volatile-rich meteorites ($1.00\pm0.04$‰). Applying a simple mass balance to the measured BSE value of $0.60\pm0.02$‰ yields a carbonaceous fraction of $0.64\pm0.16$ for Ge, compared with $0.29\pm0.07$ for Zn from nucleosynthetic isotope anomalies. The paper argues this offset is exactly what is expected if volatile-rich carbonaceous bodies were added late in Earth's accretion: siderophile Ge delivered early was stripped into the core, so the Ge in the present-day mantle is dominated by late additions, whereas zinc, which prefers silicates, preserves the whole accretion history. It further argues that the Ge isotope systematics among carbonaceous chondrites are the product of mixing between volatile-rich, isotopically heavy matrix and volatile-poor, isotopically light chondrules, with Ge showing the largest per-amu isotope fractionation of any moderately volatile element yet measured. The paper concludes that the Moon-sized embryos invoked by dynamical models to deliver carbonaceous material to Earth must themselves have been volatile-rich, either because they were undifferentiated, too large to degas, or built from previously volatile-rich objects.

Load-bearing premise

The argument assumes that germanium isotopes were not substantially fractionated when Earth's core formed, because no metal-silicate Ge isotope experiments exist; the authors use silicon as an analogue and acknowledge that the comparison is 'not ideal,' with a possible correction of $-0.3$ to $-0.5$‰ that would lower the inferred carbonaceous fraction from 0.64 to about 0.4 or less.

Editorial extensions

If this is right

  • If the preferred model is right, Earth's late-stage accretion involved volatile-rich carbonaceous bodies, and those bodies were Moon-sized or larger, since smaller planetesimals would have been accreted earlier and would have made Mars too carbonaceous-rich.
  • The carbonaceous fraction recorded by Ge (about 0.64) should be higher than the carbonaceous fraction recorded by lithophile volatile elements such as Zn (about 0.29), providing a testable fingerprint of late addition rather than early mixing.
  • The BSE's position on the chondrite $\delta^{74/70}\mathrm{Ge}$–$\delta^{128/126}\mathrm{Te}$ mixing line implies a similar carbonaceous fraction for Te (about 0.57), though the large uncertainty currently prevents using Te isotopes to constrain the late veneer.
  • The Ge isotope spread among carbonaceous chondrites places germanium on the same matrix-chondrule mixing trend as Zn, Te, Rb, and Cd, so the same volatility-driven fractionation process that shapes other moderately volatile elements also shaped Ge, with Ge showing the largest per-amu effect.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If future metal-silicate experiments show that Ge isotopes fractionate as strongly as the silicon analogue suggests ($-0.3$ to $-0.5$‰), the inferred carbonaceous fraction for Ge would fall to roughly 0.4 or below, bringing Ge into agreement with Zn and undercutting the late-addition claim; the paper's scenario is therefore directly testable by experiment.
  • The same $\delta^{74/70}\mathrm{Ge}$ tracer could be applied to Mars and Vesta to ask whether their siderophile volatile inventories also require volatile-rich late embryos; the main obstacle would be establishing the core-formation correction for each body.
  • Because the Ge–Te isotope correlation in chondrites is tight, measuring mass-dependent Te isotopes in additional BSE samples with better precision could decide whether the late veneer was carbonaceous or non-carbonaceous, a question the current data leave open.
  • The model predicts a stochastic relationship between planet mass and Ge isotope composition among terrestrial planets; a survey of Martian meteorites and lunar impact-melt rocks could test the Moon-sized-embryo delivery mechanism.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 3 minor

Summary. The paper presents the first mass-dependent Ge isotope data (δ74/70Ge) for carbonaceous and enstatite chondrites, measured by double-spike MC-ICP-MS with full analytical validation. It finds that Ge isotope and concentration variations among carbonaceous chondrites correlate with matrix mass fraction and with other moderately volatile elements, consistent with two-component mixing of a heavy, CI-like matrix and a light, non-matrix (chondrule-rich) component. Enstatite and ordinary chondrites define a narrow, relatively light range. Using a BSE value of δ74/70Ge = 0.60 ± 0.02 and Eq. (1) with enstatite and CI endmembers, the authors infer a CC-derived Ge fraction of 0.64 ± 0.16, larger than the Zn-based value of 0.29 ± 0.07. They interpret this difference as evidence for late-stage accretion of volatile-rich CC bodies to Earth, consistent with Moon-sized embryo delivery models.

Significance. The analytical contribution is strong: the double-spike method, full data tables, reproducibility on standards, and agreement with previous terrestrial reference materials give confidence in the new chondrite data. If the geochemical interpretation holds, the paper offers a new siderophile, moderately volatile tracer for reconstructing Earth's accretion, complementing nucleosynthetic isotope tracers. The paper also provides a coherent, falsifiable framework linking Ge isotope systematics in chondrites to mixing, and it presents a quantitative prediction for the CC fraction of Ge versus Zn that can be tested by future experiments. The central limitation is that the headline interpretation depends on an unmeasured core-formation isotope effect, and the paper's own uncertainty analysis admits a correction large enough to erase the key Ge-Zn distinction.

major comments (3)
  1. [Section 5.1 and 5.2 (Eq. 1, Fig. 7)] The central claim of a ~2:1 CC:NC ratio for Ge, distinct from Zn, uses the measured BSE δ74/70Ge of 0.60 ± 0.02 without applying the core-formation correction estimated in Section 5.1. Section 5.1 states that the pre-core BSE may have been up to ~0.3–0.5‰ lighter than today's value. Substituting δ74/70Ge = 0.30‰ and 0.10‰ into Eq. (1), with EC = –0.17‰ and CI = 1.00‰, yields f_CC ≈ 0.40 and 0.23, respectively. Both values overlap with the Zn-based f_CC of 0.29 ± 0.07, eliminating the 2:1 versus 1:2 distinction that is the basis for the late-stage volatile-rich CC delivery claim. The paper's qualitative statement that a lower CC fraction could be offset by invoking additional CC sources with lower δ74/70Ge is not quantified and is not a substitute for constraining the actual Ge metal–silicate fractionation factor. Please provide a quantitative sensitivity analysis of f_CC to the core-formation correction and condition the conclusions on this uncertainty.
  2. [Section 5.1] The use of Si as an analogue for Ge is acknowledged as 'not ideal,' yet the derived correction range of –0.3 to –0.5‰ is subsequently used as if it were a plausible bound on the true effect. Because the entire late-accretion interpretation hinges on this correction being small, the authors should either (a) obtain or cite direct experimental metal–silicate Ge isotope fractionation data, (b) provide a theoretical estimate based on Ge bonding and coordination, or (c) explicitly state that the late-accretion conclusion remains unevaluated until such data become available. As written, the conclusions overstate the certainty of the preferred model.
  3. [Section 5.2, Fig. 7] The x95 value for Ge (~0.4) is model-dependent, being calculated assuming single-stage core formation and a fixed equilibration factor k = 0.2. The degree of agreement between the measured Ge CC fraction and the Zn-fitted model curve depends on this assumed value. The paper should show how f_CC(Ge) and the comparison to Zn change for plausible variations in k and D, rather than adopting a single set of parameters. Without such a sensitivity test, the consistency shown in Fig. 7 is less compelling than implied.
minor comments (3)
  1. [Section 4.1] The reported non-matrix component δ74/70Ge value of –2.62!"... contains garbled formatting in the manuscript; please render the value and its error properly (e.g., –2.62 ± 0.24/–0.28‰) so that the regression output is clear.
  2. [Table 1 and Section 5.2] The two basalts analyzed in this study (BHVO-2: 0.53 ± 0.03; BCR-2: 0.58 ± 0.07) give a mean δ74/70Ge of ~0.54 ± 0.03, which is slightly lower than the adopted BSE value of 0.60 ± 0.02. Please clarify whether this offset is analytically significant and justify the use of the literature BSE value in Eq. (1), or discuss the effect of using 0.54 instead of 0.60 on the derived CC fraction.
  3. [Supplementary Information, Mo discussion] The supplementary argument that the BSE's Mo is mixed NC-CC relies substantially on a single IAB iron meteorite analysis (Campo del Cielo) and a proposed non-exponential mass fractionation artifact. This argument is presented as a definitive demonstration, but it is contentious and based on limited data; consider framing it more cautiously as an assessment of the existing literature.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the Ge CC fraction is a direct mass-balance of measured isotope ratios, and the Fig. 7 model curve is fitted to independent Zn data and is not adjusted to Ge.

full rationale

The paper's central derivation chain is self-contained with respect to the new Ge isotope data. The CC fraction for Ge in the BSE (0.64±0.16) is obtained by solving the lever-rule equation (1) using measured δ74/70Ge values for the BSE, enstatite chondrites, and CI chondrites; no parameter in this calculation is fitted to the Ge isotope data. The Fig. 7 model curve is taken from Nimmo et al. (2024) and is fitted to the CC fraction recorded by Zn, not to Ge, so the agreement between the predicted and measured Ge CC fractions is a genuine out-of-sample consistency check rather than a construction. The choice of EC and CI as endmembers is justified partly by reference to Nimmo et al. (2024), a paper co-authored by two of the present authors, but it is also independently supported by the observation that only CI-like volatile-rich carbonaceous chondrites have δ74/70Ge heavier than the BSE. The acknowledged lack of Ge metal-silicate partitioning experiments and the possible -0.3 to -0.5‰ core-formation correction are explicit limitations affecting the robustness of the interpretation, but they are not circular steps: they concern uncertainty in an input correction, not the derivation of the result from its own output. The Supplementary Information defense of the BSE's mixed NC-CC Mo heritage re-analyzes published Mo isotope data, including the disputed Campo del Cielo analysis, and does not reduce to a self-citation chain. No equation is defined in terms of the result it is used to predict, and no fitted parameter is renamed as a prediction.

Assumptions & free parameters 5 free parameters · 7 assumptions · 0 invented entities

The central CC-fraction calculation depends on assumed endmember compositions, a model for x95, and the absence of core-formation Ge isotope fractionation. The paper provides new measurements, but the interpretive steps rely on priors from the same research group (Nimmo et al. 2024) and on literature values.

free parameters (5)
  • Non-matrix component Ge concentration = 8.5 ± 1.5 μg/g
    Y-intercept of Ge vs matrix mass fraction regression (Fig. 2a); used to characterize the chondrule component.
  • Non-matrix component δ74/70Ge = -2.62 (+0.09/-0.11) ‰
    Intercept of δ74/70Ge vs 1/Ge regression (Fig. 2b); the inferred chondrule composition.
  • Enrichment factor for Zn in late-delivered CC material = 12
    From Nimmo et al. (2024), fitted to the Zn CC fraction; used to generate the model curve that 'predicts' the Ge CC fraction in Fig. 7.
  • x95 for Ge = ~0.4
    Computed from assumed bulk Earth Ge ~10 ppm, BSE 1.2 ppm, D=24, k=0.2 (Fig. 7 caption); determines the model-predicted CC fraction.
  • Potential core-formation isotope shift Δ74Ge = -0.3 to -0.5 ‰
    Scaled from Si metal-silicate fractionation experiments; applied as a correction to BSE δ74/70Ge in the uncertainty discussion.
assumptions (7)
  • domain assumption Two-component mixing of CI-like matrix and non-matrix component explains MVE isotope variations in carbonaceous chondrites.
    Invoked in Section 4.1 to interpret the Ge trends; supported by prior work on Zn, Te, Rb, Cd.
  • domain assumption Ge isotope compositions of enstatite and ordinary chondrites are not significantly modified by parent body metamorphism.
    Used to define bulk parent-body values; based on Florin et al. (2020) and the narrow range observed here.
  • ad hoc to paper Si metal-silicate isotope fractionation is a valid analogue for Ge during core formation.
    Section 5.1 explicitly states no Ge experiments exist and the comparison 'is not ideal'; used to estimate a possible core-formation correction.
  • domain assumption The NC material accreted by Earth had an enstatite-chondrite-like isotopic composition.
    Assumed in Section 5.2 for the mass balance; based on nucleosynthetic isotope studies (Dauphas 2017, Burkhardt et al. 2021).
  • domain assumption CI chondrites are the appropriate CC endmember for the BSE mixing calculation.
    Adopted from Nimmo et al. (2024); justified because CI has the heaviest δ74/70Ge among CC and is the only CC endmember that can produce the BSE value in a two-component mix.
  • domain assumption Single-stage core formation and k=0.2 for x95 calculations.
    Fig. 7 caption; these model choices set the x95 value on which the late-stage prediction depends.
  • domain assumption The BSE δ74/70Ge of 0.60±0.02 (n=42) is well defined and not affected by magmatic fractionation.
    Taken from Rouxel et al. (2006), Luais (2012), Rouxel and Luais (2017), Meng and Hu (2018); underpins the mass balance.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Origin of moderately volatile elements in Earth inferred from mass-dependent Ge isotope variations among chondrites." pith.science (2026). https://pith.science/paper/PMLMAQ4J

@misc{pith2026250506604,
  author       = {Pith},
  title        = {Pith review of: Origin of moderately volatile elements in Earth inferred from mass-dependent Ge isotope variations among chondrites},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/PMLMAQ4J}},
  note         = {Machine review of arXiv:2505.06604}
}
read the original abstract

The bulk silicate Earth (BSE) is depleted in moderately volatile elements, indicating Earth formed from a mixture of volatile-rich and -poor materials. To better constrain the origin and nature of Earth's volatile-rich building blocks, we determined the mass-dependent isotope compositions of Ge in carbonaceous (CC) and enstatite chondrites. We find that, similar to other moderately volatile elements, the Ge isotope variations among the chondrites reflect mixing between volatile-rich, isotopically heavy matrix and volatile-poor, isotopically light chondrules. The Ge isotope composition of the BSE is within the chondritic range and can be accounted for as a ~2:1 mixture of CI and enstatite chondrite-derived Ge. This mixing ratio appears to be distinct from the ~1:2 ratio inferred for Zn, reflecting the different geochemical behavior of Ge (siderophile) and Zn (lithophile), and suggesting the late-stage addition of volatile-rich CC materials to Earth. On dynamical grounds it has been argued that Earth accreted CC material through a few Moon-sized embryos, in which case the Ge isotope results imply that these objects were volatile-rich, presumably because they were either undifferentiated or accreted volatile-rich objects themselves before being accreted by Earth.

Figures

Figures reproduced from arXiv: 2505.06604 by the authors.

Figure 8
Figure 8. δ128/126Te versus δ74/70Ge for carbonaceous chondrites (blue circles), enstatite chondrites (red circles), and the bulk silicate Earth (green circle). Group averages for enstatite chondrites are based solely on samples of petrological type 3 and 4. Tellurium data are from Hellmann et al. (2020) and Hellmann et al. (2021). As in [PITH_FULL_IMAGE:figures/full_fig_p036_8.png] view at source ↗

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

81 extracted references · 55 canonical work pages

  1. [1]

    no double spike and Hydride generator instead of Aridus II)

    as prior studies [δ74/70Ge = 0.53±0.12 for BHVO-2 (Escoube et al., 2012; Rouxel and Luais, 2017); δ74/70Ge = 0.55±0.13 for BCR-1 (Rouxel et al., 2006; Escoube et al., 2012; Luais, 2012)], which used different analytical setups (i.e. no double spike and Hydride generator instead of Aridus II). 3 Results Germanium concentrations and δ74/70Ge values of the c...

    2012

  2. [2]

    The carbonaceous chondrite groups exhibit variable Ge concentrations and isotopic compositions, ranging from ~10 ppm Ge and δ74/70Ge ≈ –1.5 for CR chondrites to ~35 ppm Ge and δ74/70Ge ≈ 1 for CI chondrites (Fig. 1,2). Despite these variations, samples from a given carbonaceous chondrite group exhibit similar Ge concentrations and indistinguishable δ74/70...

    work page 2020

  3. [4]

    /23!#)$%&’()(23!

    Tellurium data are from Hellmann et al. (2020) and Hellmann et al. (2021). As in Fig. 2, linear regressions were calculated using Isoplot (Ludwig, 2012). TD: Tarda. TL: Tagish Lake. The fraction of CC-derived Te in the BSE can be calculated using the lever rule [equation (1)] along the correlation line. For mixing between enstatite chondrites and CI chond...

    work page 2020

  4. [6]

    For Ge, however, Florin et al

    tend to show larger elemental and isotopic variations (e.g., Luck et al., 2005; Moynier et al., 2007, 2011; Hellmann et al., 2021; Braukmüller et al., 2025). For Ge, however, Florin et al. (2020) showed that ordinary chondrites of all petrologic types display rather homogeneous δ74/70Ge values, indicating that Ge isotope fractionation during parent body m...

    work page 2020

  5. [7]

    Also shown in Fig. 7 is a model for how the CC fraction in the BSE evolved for MVEs, fitted to the CC fraction recorded for Zn and with the late-added CC-rich material enriched in Zn by a factor of 12 (Nimmo et al., 2024). For Zn, CC fractions of between ~0.3 and ~0.5 have been reported, depending on the assumed compositions of the NC and CC endmembers (S...

    work page 2024

  6. [8]

    suggest a predominantly NC late veneer. Moreover, the results of this study, together with prior results on nucleosynthetic Zn isotope anomalies, show that the MVEs in the BSE are unlikely to derive from a single source, but more likely are contributed from a mix of NC and CC bodies. This raises the question of whether mass-dependent Te isotope variations...

    work page 2021

  7. [13]

    Moderately volatile elements in chondrites record chondrule formation, two-component mixing and redistribution on parent bodies. Geochim. Cosmochim. Acta 393, 43–62. https://doi.org/10.1016/j.gca.2025.02.001 Budde, G., Burkhardt, C., Brennecka, G.A., Fischer-Gödde, M., Kruijer, T.S., Kleine, T.,

    work page doi:10.1016/j.gca.2025.02.001 2025

  8. [16]

    Terrestrial planet formation from lost inner solar system material. Sci. Adv. 7, eabj7601. https://doi.org/10.1126/sciadv.abj7601 Dauphas, N.,

    doi:10.1126/sciadv.abj7601

Show all 81 references
  1. [17]

    Nature 541, 521–524

    The isotopic nature of the Earth’s accreting material through time. Nature 541, 521–524. https://doi.org/10.1038/nature20830 Dauphas, N., Chen, J.H., Zhang, J., Papanastassiou, D.A., Davis, A.M., Travaglio, C.,

    doi

  2. [22]

    Meteorit

    Condensation and evaporation processes during CB chondrite formation: Insights from Ge isotopes and highly siderophile element abundances. Meteorit. Planet. Sci. 56, 1191–1211. https://doi.org/10.1111/maps.13698 Florin, G., Luais, B., Rushmer, T., Alard, O.,

    doi

  3. [25]

    Tellurium isotope cosmochemistry: Implications for volatile fractionation in chondrite parent bodies and origin of the late veneer. Geochim. Cosmochim. Acta 309, 313–328. https://doi.org/10.1016/j.gca.2021.06.038 Hellmann, J.L., Hopp, T., Burkhardt, C., Kleine, T.,

    2021 doi

  4. [26]

    Earth Planet

    Origin of volatile element depletion among carbonaceous chondrites. Earth Planet. Sci. Lett. 549, 116508. https://doi.org/10.1016/j.epsl.2020.116508 Hellmann, J.L., Schneider, J.M., Wölfer, E., Drążkowska, J., Jansen, C.A., Hopp, T., Burkhardt, C., Kleine, T.,

    2020

  5. [28]

    Earth Planet

    Experimental evidence for Mo isotope fractionation between metal and silicate liquids. Earth Planet. Sci. Lett. 379, 38–48. https://doi.org/10.1016/j.epsl.2013.08.003 Hin, R.C., Coath, C.D., Carter, P.J., Nimmo, F., Lai, Y.-J., Pogge Von Strandmann, P.A.E., Willbold, M., Leinh...

    2013 doi

  6. [29]

    Nature 549, 511–515

    Magnesium isotope evidence that accretional vapour loss shapes planetary compositions. Nature 549, 511–515. https://doi.org/10.1038/nature23899 Hin, R.C., Fitoussi, C., Schmidt, M.W., Bourdon, B.,

    doi

  7. [30]

    Earth Planet

    Experimental determination of the Si isotope fractionation factor between liquid metal and liquid silicate. Earth Planet. Sci. Lett. 387, 55–66. https://doi.org/10.1016/j.epsl.2013.11.016 Kato, C., Moynier, F.,

    2013 doi

  8. [31]

    Earth Planet

    Gallium isotopic evidence for the fate of moderately volatile 26 elements in planetary bodies and refractory inclusions. Earth Planet. Sci. Lett. 479, 330–339. https://doi.org/10.1016/j.epsl.2017.09.028 Kleine, T., Steller, T., Burkhardt, C., Nimmo, F.,

    2017 doi

  9. [32]

    Icarus 397, 115519

    An inner solar system origin of volatile elements in Mars. Icarus 397, 115519. https://doi.org/10.1016/j.icarus.2023.115519 Koefoed, P., Barrat, J.-A., Pravdivtseva, O., Alexander, C.M.O., Lodders, K., Ogliore, R., Wang, K.,

    2023

  10. [33]

    The potassium isotopic composition of CI chondrites and the origin of isotopic variations among primitive planetary bodies. Geochim. Cosmochim. Acta 358, 49–60. https://doi.org/10.1016/j.gca.2023.07.025 Kruijer, T.S., Burkhardt, C., Budde, G., Kleine, T.,

    2023 doi

  11. [34]

    Age of Jupiter inferred from the distinct genetics and formation times of meteorites. Proc. Natl. Acad. Sci. 114, 6712–6716. https://doi.org/10.1073/pnas.1704461114 Labidi, J., Cartigny, P., Moreira, M.,

    doi

  12. [35]

    Nature 501, 208–211

    Non-chondritic sulphur isotope composition of the terrestrial mantle. Nature 501, 208–211. https://doi.org/10.1038/nature12490 Labidi, J., König, S., Kurzawa, T., Yierpan, A., Schoenberg, R.,

    doi

  13. [40]

    A history of violence: Insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes and water contents. Geochim. Cosmochim. Acta 220, 19–35. https://doi.org/10.1016/j.gca.2017.09.027 Marrocchi, Y., Piralla, M., Regnault, M., ...

    doi

  14. [42]

    Science 379, 369–372

    Nucleosynthetic isotope anomalies of zinc in meteorites constrain the origin of Earth’s volatiles. Science 379, 369–372. https://doi.org/10.1126/science.abn1021 Martins, R., Morton, E.M., Kuthning, S., Goes, S., Williams, H.M., Rehkämper, M.,

    doi

  15. [43]

    27 Primitive asteroids as a major source of terrestrial volatiles. Sci. Adv. 10, eado4121. https://doi.org/10.1126/sciadv.ado4121 Meisel, T., Walker, R.J., Morgan, J.W.,

    doi

  16. [46]

    Icarus 365, 114497

    Accretion and differentiation of early planetary bodies as recorded in the composition of the silicate Earth. Icarus 365, 114497. https://doi.org/10.1016/j.icarus.2021.114497 Morton, E.M., Pickard, H., Wombacher, F., Huang, Y., Palk, E., Martins, R., Kuthning, S., Schönbächler...

    2021

  17. [48]

    Comparative stable isotope geochemistry of Ni, Cu, Zn, and Fe in chondrites and iron meteorites. Geochim. Cosmochim. Acta 71, 4365–4379. https://doi.org/10.1016/j.gca.2007.06.049 Moynier, F., Paniello, R.C., Gounelle, M., Albarède, F., Beck, P., Podosek, F., Zanda, B.,

    2007 doi

  18. [50]

    Nature 615, 854–857

    Degassing of early-formed planetesimals restricted water delivery to Earth. Nature 615, 854–857. https://doi.org/10.1038/s41586-023-05721-5 Nie, N.X., Chen, X.-Y., Hopp, T., Hu, J.Y., Zhang, Z.J., Teng, F.-Z., Shahar, A., Dauphas, N.,

    doi

  19. [52]

    Earth Planet

    Mechanisms and timing of carbonaceous chondrite delivery to the Earth. Earth Planet. Sci. Lett. 648, 119112. https://doi.org/10.1016/j.epsl.2024.119112 Palme, H., O’Neill, H.St.C.,

    2024

  20. [54]

    Elsevier, pp

    Cosmochemical Estimates of Mantle Composition, in: Treatise on Geochemistry. Elsevier, pp. 1–39. https://doi.org/10.1016/B978-0-08-095975-7.00201-1 Paquet, Marine, Moynier, F., Yokoyama, T., Dai, W., Hu, Y., Abe, Y., Aléon, J., O’D. Alexander, C.M., Amari, S., Amelin, Y., Bajo...

    doi

  21. [55]

    Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis. Nat. Astron. 7, 182–189. https://doi.org/10.1038/s41550-022-01846-1 Paquet, M., Sossi, P.A., Moynier, F.,

    doi

  22. [56]

    Earth Planet

    Origin and abundances of volatiles on Mars from the zinc isotopic composition of Martian meteorites. Earth Planet. Sci. Lett. 611, 118126. https://doi.org/10.1016/j.epsl.2023.118126 Poitrasson, F.,

    2023

  23. [57]

    Silicon Isotope Geochemistry. Rev. Mineral. Geochem. 82, 289–344. https://doi.org/10.2138/rmg.2017.82.8 Pringle, E.A., Moynier, F., Beck, P., Paniello, R., Hezel, D.C.,

    2017 doi

  24. [58]

    Earth Planet

    The origin of volatile element depletion in early solar system material: Clues from Zn isotopes in chondrules. Earth Planet. Sci. Lett. 468, 62–71. https://doi.org/10.1016/j.epsl.2017.04.002 Righter, K., King, C., Danielson, L., Pando, K., Lee, C.T.,

    2017 doi

  25. [59]

    Earth Planet

    Experimental determination of the metal/silicate partition coefficient of Germanium: Implications for core and mantle differentiation. Earth Planet. Sci. Lett. 304, 379–388. https://doi.org/10.1016/j.epsl.2011.02.015 Rouxel, O., Galy, A., Elderfield, H.,

    2011 doi

  26. [63]

    High-temperature Si isotope fractionation between iron metal and silicate. Geochim. Cosmochim. Acta 75, 7688–7697. https://doi.org/10.1016/j.gca.2011.09.038 Shahar, A., Ziegler, K., Young, E.D., Ricolleau, A., Schauble, E.A., Fei, Y.,

    2011 doi

  27. [65]

    Stochastic accretion of the Earth. Nat. Astron. 6, 951–960. https://doi.org/10.1038/s41550-022-01702-2 29 Spitzer, F., Burkhardt, C., Budde, G., Kruijer, T.S., Morbidelli, A., Kleine, T.,

    doi

  28. [67]

    Icarus 386, 115171

    Nucleosynthetic zinc isotope anomalies reveal a dual origin of terrestrial volatiles. Icarus 386, 115171. https://doi.org/10.1016/j.icarus.2022.115171 Wang, Z., Becker, H.,

    2022

  29. [68]

    Nature 499, 328–331

    Ratios of S, Se and Te in the silicate Earth require a volatile-rich late veneer. Nature 499, 328–331. https://doi.org/10.1038/nature12285 Warren, P.H.,

    doi

  30. [69]

    Earth Planet

    Stable-isotopic anomalies and the accretionary assemblage of the Earth and Mars: A subordinate role for carbonaceous chondrites. Earth Planet. Sci. Lett. 311, 93–100. https://doi.org/10.1016/j.epsl.2011.08.047 Wasson, J.T., Kallemeyn, G.W.,

    2011 doi

  31. [72]

    The condensation temperatures of the elements: A reappraisal. Am. Mineral. 104, 844–856. https://doi.org/10.2138/am-2019-6852CCBY Worsham, E.A., Kleine, T.,

    2019 doi

  32. [73]

    Late accretionary history of Earth and Moon preserved in lunar impactites. Sci. Adv. 7, eabh2837. https://doi.org/10.1126/sciadv.abh2837 Ziegler, K., Young, E.D., Schauble, E.A., Wasson, J.T.,

    doi

  33. [75]

    and Spitzer et al. (2020). Linear regressions and error envelopes (95% CI) were calculated using Isoplot (Ludwig, 2012). Tarda was excluded from the regression in (b). TD: Tarda. TL: Tagish Lake. BHVO-2BCR-2Sahara 97072 (EH3) LAR 12001 (EH3)GRO 95517 (EH3)MIL 07028 (EH3)LAR 06...

    2020

  34. [76]

    and Spitzer et al. (2020). Black lines and associated error envelopes are mixing lines between CI chondrite-like matrix and the non-matrix component. TD: Tarda. TL: Tagish Lake. Fig. 6: δ74/70Ge variations among carbonaceous (blue) and non-carbonaceous (red) meteorites. Chondr...

    2020

  35. [78]

    Most of these data plot on the NC-line defined by Spitzer et al

    and MC-ICPMS (Marti et al., 2023; Poole et al., 2017). Most of these data plot on the NC-line defined by Spitzer et al. (2020) (solid red line) and slightly below the NC-line as defined by Bermingham et al. (2025). The Mo isotope anomalies among these IABs define a broad trend...

    2020

  36. [79]

    The non-carbonaceous nature of Earth’s late-stage accretion. Geochim. Cosmochim. Acta S0016703724005751. https://doi.org/10.1016/j.gca.2024.11.005 Budde, G., Burkhardt, C., Kleine, T.,

    2024 doi

  37. [80]

    Molybdenum isotopic evidence for the late accretion of outer Solar System material to Earth. Nat. Astron. 3, 736–741. https://doi.org/10.1038/s41550-019-0779-y Budde, G., Tissot, F.L.H., Kleine, T., Marquez, R.T.,

    doi

  38. [81]

    Geochemistry 83, 126007

    Spurious molybdenum isotope anomalies resulting from non-exponential mass fractionation. Geochemistry 83, 126007. https://doi.org/10.1016/j.chemer.2023.126007 Escoube, R., Rouxel, O.J., Luais, B., Ponzevera, E., Donard, O.F.X.,

    2023

  39. [82]

    Geostand

    An Intercomparison Study of the Germanium Isotope Composition of Geological Reference Materials. Geostand. Geoanalytical Res. 36, 149–159. https://doi.org/10.1111/j.1751-908X.2011.00135.x Florin, G., Luais, B., Rushmer, T., Alard, O.,

    2011 arXiv

  40. [83]

    Influence of redox processes on the germanium isotopic composition of ordinary chondrites. Geochim. Cosmochim. Acta 269, 270–291. https://doi.org/10.1016/j.gca.2019.10.038 Luais, B.,

    2019 doi

  41. [84]

    Germanium chemistry and MC-ICPMS isotopic measurements of Fe–Ni, Zn alloys and silicate matrices: Insights into deep Earth processes. Chem. Geol. 334, 295–311. https://doi.org/10.1016/j.chemgeo.2012.10.017 Luais, B.,

    2012 doi

  42. [85]

    Earth Planet

    Isotopic fractionation of germanium in iron meteorites: Significance for nebular condensation, core formation and impact processes. Earth Planet. Sci. Lett. 262, 21–36. https://doi.org/10.1016/j.epsl.2007.06.031 Marti, K., Fischer-Gödde, M., Proksche, C.,

    2007 doi

  43. [86]

    https://doi.org/10.3847/1538-4357/acee81 Meng, Y.-M., Hu, R.-Z.,

    doi

  44. [87]

    Minireview: Advances in Germanium Isotope Analysis by Multiple Collector–Inductively Coupled Plasma–Mass Spectrometry. Anal. Lett. 51, 627–647. https://doi.org/10.1080/00032719.2017.1350965 Morton, E.M., Pickard, H., Wombacher, F., Huang, Y., Palk, E., Martins, R., Kuthning, S...

    2017

  45. [88]

    https://doi.org/10.3847/1538-4357/ad87ed Nie, N.X., Chen, X.-Y., Hopp, T., Hu, J.Y., Zhang, Z.J., Teng, F.-Z., Shahar, A., Dauphas, N.,

    doi

  46. [89]

    Imprint of chondrule formation on the K and Rb isotopic compositions of carbonaceous meteorites. Sci. Adv. 7, eabl3929. https://doi.org/10.1126/sciadv.abl3929 Poole, G.M., Rehkämper, M., Coles, B.J., Goldberg, T., Smith, C.L.,

    doi

  47. [90]

    Earth Planet

    Nucleosynthetic molybdenum iso-tope anomalies in iron meteorites – new evidence for thermal processing of solar nebula material. Earth Planet. Sci. Lett. 473, 215–226. https://doi.org/10.1016/j.epsl.2017.05.001 Rouxel, O., Galy, A., Elderfield, H.,

    2017 doi

  48. [91]

    Germanium isotopic variations in igneous rocks and marine sedi-ments. Geochim. Cosmochim. Acta 70, 3387–3400. https://doi.org/10.1016/j.gca.2006.04.025 Rouxel, O.J., Luais, B.,

    2006 doi

  49. [92]

    Germanium Isotope Geochemistry. Rev. Mineral. Geochem. 82, 601–656. https://doi.org/10.2138/rmg.2017.82.14 47 Siebert, C., Nägler, T.F., Kramers, J.D.,

    2017 doi

  50. [93]

    Determination of molybdenum isotope fractionation by double‐spike multicollector inductively coupled plasma mass spectrometry. Geochem. Geophys. Geosystems 2, 2000GC000124. https://doi.org/10.1029/2000GC000124 Spitzer, F., Burkhardt, C., Budde, G., Kruijer, T.S., Morbidelli, A...

    doi

  51. [94]

    Astrophys

    Isotopic Evolution of the Inner Solar System Inferred from Molybdenum Isotopes in Meteorites. Astrophys. J. 898, L2. https://doi.org/10.3847/2041-8213/ab9e6a Wölfer, E., Burkhardt, C., Kleine, T.,

    doi

  52. [95]

    Germanium stable isotope measurements by double-spike MC-ICPMS. J. Anal. At. Spectrom. 40, 1023–1036. https://doi.org/10.1039/D4JA00359D Worsham, E.A., Bermingham, K.R., Walker, R.J.,

    doi

  53. [96]

    Earth Planet

    Characterizing cosmochemical materials with genetic affinities to the Earth: Genetic and chronological diversity within the IAB iron meteorite complex. Earth Planet. Sci. Lett. 467, 157–166. https://doi.org/10.1016/j.epsl.2017.02.044

    doi

  54. [1988]

    Compositions of chondrites. Philos. Trans. R. Soc. Lond. Ser. Math. Phys. Sci. 325, 535–544. https://doi.org/10.1098/rsta.1988.0066 Wölfer, E., Burkhardt, C., Kleine, T.,

    1988

  55. [1996]

    Nature 383, 517–520

    The osmium isotopic composition of the Earth’s primitive upper mantle. Nature 383, 517–520. https://doi.org/10.1038/383517a0 Meng, Y.-M., Hu, R.-Z.,

    doi

  56. [2001]

    Earth Planet

    In search of lost planets – the paleocosmochemistry of the inner solar system. Earth Planet. Sci. Lett. 192, 545–559. https://doi.org/10.1016/S0012-821X(01)00479-4 Hellmann, J.L., Hopp, T., Burkhardt, C., Becker, H., Fischer-Gödde, M., Kleine, T.,

    doi

  57. [2005]

    Zn and Cu isotopic variations in chondrites and iron meteorites: Early solar nebula reservoirs and parent-body processes. Geochim. Cosmochim. Acta 69, 5351–5363. https://doi.org/10.1016/j.gca.2005.06.018 Ludwig, K.R.,

    2005 doi

  58. [2006]

    Volatile evolution and loss. Meteor. Early Sol. Syst. Vol II Univ. Ariz. Press. https://doi.org/10.2307/j.ctv1v7zdmm Escoube, R., Rouxel, O.J., Luais, B., Ponzevera, E., Donard, O.F.X.,

    doi

  59. [2009]

    Earth Planet

    Experimentally determined Si isotope fractionation between silicate and Fe metal and implications for Earth’s core formation. Earth Planet. Sci. Lett. 288, 228–234. https://doi.org/10.1016/j.epsl.2009.09.025 Siebert, C., Nägler, T.F., Kramers, J.D.,

    2009 doi

  60. [2010]

    Earth Planet

    Metal–silicate silicon isotope fractionation in enstatite meteorites and constraints on Earth’s core formation. Earth Planet. Sci. Lett. 295, 487–496. https://doi.org/10.1016/j.epsl.2010.04.030 30 Table 1: Ge isotopic and concentration data for chondrites and terrestrial sampl...

    2025 doi

  61. [2011]

    Nature of volatile depletion and genetic relationships in enstatite chondrites and aubrites inferred from Zn isotopes. Geochim. Cosmochim. Acta 75, 297–307. https://doi.org/10.1016/j.gca.2010.09.022 Newcombe, M.E., Nielsen, S.G., Peterson, L.D., Wang, J., Alexander, C.M.O., Sa...

    2010 doi

  62. [2012]

    Geochemistry of CI chondrites: Major and trace elements, and Cu and Zn Isotopes. Geochim. Cosmochim. Acta 83, 79–92. https://doi.org/10.1016/j.gca.2011.12.011 Bermingham, K.R., Tornabene, H.A., Walker, R.J., Godfrey, L.V., Meyer, B.S., Piccoli, P., Mojzsis, S.J.,

    2011 doi

  63. [2013]

    and Si (Hin et al., 2014), but no such experiments have yet been performed for Ge. In ordinary chondrites and pallasites, Ge in silicates is isotopically light compared to co-existing metal, likely reflecting isotope fractionation during subsolidus cooling (Luais, 2007, 2012; ...

    2014

  64. [2014]

    Earth Planet

    Calcium-48 isotopic anomalies in bulk chondrites and achondrites: Evidence for a uniform 25 isotopic reservoir in the inner protoplanetary disk. Earth Planet. Sci. Lett. 407, 96–108. https://doi.org/10.1016/j.epsl.2014.09.015 Dauphas, N., Hopp, T., Nesvorný, D.,

    2014 doi

  65. [2015]

    Earth Planet

    Composition of the core from gallium metal–silicate partitioning experiments. Earth Planet. Sci. Lett. 427, 191–201. https://doi.org/10.1016/j.epsl.2015.06.063 Braukmüller, N., Wombacher, F., Funk, C., Münker, C.,

    2015 doi

  66. [2016]

    Earth Planet

    Molybdenum isotopic evidence for the origin of chondrules and a distinct genetic heritage of carbonaceous and non-carbonaceous meteorites. Earth Planet. Sci. Lett. 454, 293–303. https://doi.org/10.1016/j.epsl.2016.09.020 Budde, G., Burkhardt, C., Kleine, T.,

    2016 doi

  67. [2017]

    or Te (Hellmann et al., 2020). 22 Consistent with their chondrule-rich nature, enstatite chondrites, like ordinary chondrites (Florin et al., 2020), have lighter Ge isotope compositions than the more volatile-rich carbonaceous chondrites. However, differences in nucleosyntheti...

    2020

  68. [2018]

    Earth Planet

    The selenium isotopic variations in chondrites are mass-dependent; Implications for sulfide formation in the early solar system. Earth Planet. Sci. Lett. 481, 212–222. https://doi.org/10.1016/j.epsl.2017.10.032 Luais, B.,

    2017 doi

  69. [2019]

    Earth’s volatile element depletion pattern inherited from a carbonaceous chondrite-like source. Nat. Geosci. 12, 564–568. https://doi.org/10.1038/s41561-019-0375-x Braukmüller, N., Funk, C., Abouchami, W., Pickard, H., Rehkämper, M., Bragagni, A., Galer, S.J.G., Münker, C., Be...

    doi

  70. [2021]

    "$%&.’( (Fig. 2b), corresponding to an isotopic fractionation relative to the CI chondrite-like matrix of Δ74Ge = 3.62!

    or is a condensation signature inherited from chondrule precursors (Hellmann et al., 2020). The composition of the non-matrix component can be inferred from the correlations of MVE concentration and isotopic composition with the mass fraction of matrix. We followed the approac...

    2020

  71. [2022]

    Earth Planet

    Isotopic evidence for two chondrule generations in CR chondrites and their relationships to other carbonaceous chondrites. Earth Planet. Sci. Lett. 593, 117683. https://doi.org/10.1016/j.epsl.2022.117683 Martins, R., Kuthning, S., Coles, B.J., Kreissig, K., Rehkämper, M.,

    2022

  72. [2023]

    Astrophys

    Origin of Isotopic Diversity among Carbonaceous Chondrites. Astrophys. J. Lett. 946, L34. https://doi.org/10.3847/2041-8213/acc102 Hin, R.C., Burkhardt, C., Schmidt, M.W., Bourdon, B., Kleine, T.,

    doi

  73. [2024]

    Icarus 408, 115805

    Bayesian inference on the isotopic building blocks of Mars and Earth. Icarus 408, 115805. https://doi.org/10.1016/j.icarus.2023.115805 Davis, A.M.,

    2023

Pith tools

Reviewed August 15, 2026 · model on record in the stance chip above.