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Loss of immiscible nitrogen from metallic melt explains Earth’s missing nitrogen

J. Liu1,

1Department of Earth and Environmental Sciences, Michigan State University, MI 48824, USA

S.M. Dorfman1,

1Department of Earth and Environmental Sciences, Michigan State University, MI 48824, USA

M. Lv1,

1Department of Earth and Environmental Sciences, Michigan State University, MI 48824, USA

J. Li2,

2Department of Earth and Environmental Sciences, University of Michigan, MI 48109, USA

F. Zhu2,

2Department of Earth and Environmental Sciences, University of Michigan, MI 48109, USA

Y. Kono3,4

3HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, IL 60439, USA
4Geodynamics Research Center, Ehime University, Ehime 790-8577, Japan

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Liu, J., Dorfman, S.M., Lv, M., Li, J., Zhu, F., Kono, Y. (2019) Loss of immiscible nitrogen from metallic melt explains Earth’s missing nitrogen. Geochem. Persp. Let. 11, 18–22.

S.M. Dorfman acknowledges funding from Michigan State University, the Sloan Foundation’s Deep Carbon Observatory, and NSF EAR-1751664.

Geochemical Perspectives Letters v11  |  doi: 10.7185/geochemlet.1919
Received 2 January 2019  |  Accepted 8 June 2019  |  Published 30 July 2019
Copyright © The Authors

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0




Figure 1 Representative X-ray radiographic images showing the evolution of the miscibility gap in Fe-N-C system under high pressure and high temperature conditions (run 4-17). This in situ X-ray radiography experiment starts at 0.4 GPa with Fe3N as the starting material. (a) The sample is below solidus at 0.4 GPa and 1483 K. (b) Around 1729 K, immiscible N-rich supercritical fluid coexists with metallic liquid. (c) At higher temperatures, N-rich supercritical fluid partially dissolves into metallic liquid. (d) Lowering temperature re-exsolves N-rich supercritical fluid from metallic liquid. The corresponding movie is shown in Video S-1.
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Figure 2 The pressure dependence of N solubility in Fe-N-C melt. The solid circles are for Fe-N starting materials; the open circles are for Fe-N-C starting materials. Symbol sizes are proportional to the temperatures (1400-2300 K) at which the experiments are quenched and colours indicate initial compositions (see legend). The blue and red curves are modelled N solubilities in Fe-N-C melt at 2000 K and 2300 K, respectively, from Speelmanns et al. (2018)

Speelmanns, I.M., Schmidt, M.W., Liebske, C. (2018) Nitrogen Solubility in Core Materials. Geophysical Research Letters 45, 7434–7443.

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Figure 3 The evolution of the BSE C/N ratio with the degree of re-equilibration between alloy and silicate melts during core formation. The blue curve is calculated at oxidised conditions (ΔIW-0.5 to ΔIW-1.0); the red curve is for reduced conditions (ΔIW-1.8 to ΔIW-2.2) and the black curve is for very reduced conditions (ΔIW-3.4 to ΔIW-3.6). The horizontal yellow bar marks the range of the estimated present BSE C/N ratio (Bergin et al., 2015

Bergin, E.A., Blake, G.A., Ciesla, F., Hirschmann, M.M., Li, J. (2015) Tracing the ingredients for a habitable earth from interstellar space through planet formation. Proceedings of the National Academy of Sciences 112, 8965–8970.

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