Letter | Published:

Carbon and sulfur budget of the silicate Earth explained by accretion of differentiated planetary embryos

Nature Geoscience volume 9, pages 781785 (2016) | Download Citation

Abstract

The abundances of volatile elements in the Earth’s mantle have been attributed to the delivery of volatile-rich material after the main phase of accretion1,2,3. However, no known meteorites could deliver the volatile elements, such as carbon, nitrogen, hydrogen and sulfur, at the relative abundances observed for the silicate Earth4. Alternatively, Earth could have acquired its volatile inventory during accretion and differentiation, but the fate of volatile elements during core formation is known only for a limited set of conditions4,5,6,7,8. Here we present constraints from laboratory experiments on the partitioning of carbon and sulfur between metallic cores and silicate mantles under conditions relevant for rocky planetary bodies. We find that carbon remains more siderophile than sulfur over a range of oxygen fugacities; however, our experiments suggest that in reduced or sulfur-rich bodies, carbon is expelled from the segregating core. Combined with previous constraints9, we propose that the ratio of carbon to sulfur in the silicate Earth could have been established by differentiation of a planetary embryo that was then accreted to the proto-Earth. We suggest that the accretion of a Mercury-like (reduced) or a sulfur-rich (oxidized) differentiated body—in which carbon has been preferentially partitioned into the mantle—may explain the Earth’s carbon and sulfur budgets.

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Acknowledgements

Y.L. thanks A. Boujibar for discussion on topics related to the present work. NASA grant NNX13AM51G to R.D. supported this work. R.D. also acknowledges a NSF grant EAR-1053816 that established the Rice University’s multi-anvil facility used in this study.

Author information

Author notes

    • Yuan Li

    Present address: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.

Affiliations

  1. Department of Earth Science, Rice University, 6100 Main Street, MS 126, Houston, Texas 77005, USA

    • Yuan Li
    • , Rajdeep Dasgupta
    •  & Kyusei Tsuno
  2. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

    • Brian Monteleone
    •  & Nobumichi Shimizu

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Contributions

Y.L. and R.D. conceived the project. Y.L. performed all the experiments, FTIR and Raman analyses of experimental glasses. B.M., Y.L. and N.S. performed the SIMS analyses. K.T. performed the electron microprobe analyses. Y.L. and R.D. analysed and interpreted all the data and co-wrote the paper. All authors commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Yuan Li or Rajdeep Dasgupta.

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DOI

https://doi.org/10.1038/ngeo2801

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