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Carbon isotopic signatures of super-deep diamonds mediated by iron redox chemistry

J. Liu1,

1Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78712, USA

W. Wang2,

2Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China

H. Yang3,

3Center for High Pressure Science and Technology Advanced Research (HPSTAR), Pudong, Shanghai 201203, China

Z. Wu2,4,

2Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China
4CAS Center for Excellence in Comparative Planetology, China

M.Y. Hu5,

5Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

J. Zhao5,

5Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

W. Bi5,6,

5Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
6Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

E.E. Alp5,

5Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA

N. Dauphas7,

7Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA

W. Liang8,

8Key Laboratory for High Temperature and High Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550002, China

B. Chen9,

9Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, HI 96822, USA

J.-F. Lin1,

1Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78712, USA

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Liu, J., Wang, W., Yang, H., Wu, Z., Hu, M.Y., Zhao, J., Bi, W., Alp, E.E., Dauphas, N., Liang, W., Chen, B., Lin, J.-F. (2019) Carbon isotopic signatures of super-deep diamonds mediated by iron redox chemistry. Geochem. Persp. Let. 10, 51–55.

Strategic Priority Research Program of the Chinese Academy of Sciences (XDB18000000); the Natural Science Foundation of China (41721002); Deep Carbon Observatory (DCO); the National Science Foundation for Young Scientists of China (41802044); the Consortium for Materials Properties Research in Earth Sciences under NSF Cooperative Agreement EAR 1606856; NSF grants EAR-1555388 and EAR-1565708.

Geochemical Perspectives Letters v10  |  doi: 10.7185/geochemlet.1915
Received 28 May 2018  |  Accepted 09 April 2019  |  Published 24 May 2019
Copyright © The Authors

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




Figure 1 Partial phonon density of states (PDOS) of 57Fe (a, b) and 12C (c, d) in FeCO3 at high pressures. In (a) and (b), the open cycles are PDOS of Fe measured by NRIXS; the blue curves are calculated PDOS of Fe by DFT + U. The red curves in (c) and (d) are calculated PDOS of C. The lowest energy peak at 20-40 meV can be attributed to the acoustic phonons. According to previous high pressure Raman and infrared studies of FeCO3 (Santillán and Williams, 2004

Santillán, J., Williams, Q. (2004) A high-pressure infrared and X-ray study of FeCO3 and MnCO3: comparison with CaMg(CO3)2-dolomite. Physics of the Earth and Planetary Interiors 143–144, 291–304.

; Lin et al., 2012

Lin, J.-F., Liu, J., Jacobs, C., Prakapenka, V.B. (2012) Vibrational and elastic properties of ferromagnesite across the electronic spin-pairing transition of iron. American Mineralogist 97, 583–591.

), the other peaks can be assigned to librational mode (L), translational mode (T) and in-plane bending mode (v4), out of plane bending vibration (v2) and asymmetric stretch (v3) of CO32- (marked as dashed vertical lines). The energies of v2 and v3 modes (marked as dotted vertical lines) at 60 GPa are linearly extrapolated from those measured up to 50 GPa for FeCO3 (Santillán and Williams, 2004

Santillán, J., Williams, Q. (2004) A high-pressure infrared and X-ray study of FeCO3 and MnCO3: comparison with CaMg(CO3)2-dolomite. Physics of the Earth and Planetary Interiors 143–144, 291–304.

). In the PDOS of Fe at 60 GPa (b), the splitting of v4 mode at approximately 100-120 meV has also been observed in a previous Raman study (Lin et al., 2012

Lin, J.-F., Liu, J., Jacobs, C., Prakapenka, V.B. (2012) Vibrational and elastic properties of ferromagnesite across the electronic spin-pairing transition of iron. American Mineralogist 97, 583–591.

), which is explained as a result of the enhanced interaction between low-spin Fe2+ and neighbouring CO32- units.
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Figure 2 Comparison of the histogram for δ13C of super-deep diamonds (left axis) and the probability density functions (PDFs, right axis) of δ13CDia derived from metallic melt for different P-T conditions. The red, green and black solid curves are calculated PDFs by using Δ13CDia-FeC melt at 250 km, 660 km and 1500 km depths along a cold slab geotherm (Yang et al., 2017

Yang, D., Wang, W., Wu, Z. (2017) Elasticity of superhydrous phase B at the mantle temperatures and pressures: Implications for 800 km discontinuity and water flow into the lower mantle. Journal of Geophysical Research: Solid Earth 122, 5026–5037.

), respectively. The yellow dotted curve is calculated by using Δ13CDia-FeC melt at 250 km along the modern mantle geotherm (Yang et al., 2017

Yang, D., Wang, W., Wu, Z. (2017) Elasticity of superhydrous phase B at the mantle temperatures and pressures: Implications for 800 km discontinuity and water flow into the lower mantle. Journal of Geophysical Research: Solid Earth 122, 5026–5037.

), which may be similar to the Archean mantle geotherm (Santosh et al., 2010

Santosh, M., Maruyama, S., Komiya, T., Yamamoto, S. (2010) Orogens in the evolving Earth: from surface continents to ‘lost continents’ at the core–mantle boundary. Geological Society, London, Special Publications 338, 77–116.

). The pink dashed curve is for diamonds forming from C-H-O fluids, which is calculated using the largest reported value of Δ13CDia-COH (-2.9 ‰) (Cartigny et al., 2014

Cartigny, P., Palot, M., Thomassot, E., Harris, J.W. (2014) Diamond Formation: A Stable Isotope Perspective. Annual Review of Earth and Planetary Sciences 42, 699–732.

). The inset figure shows the negative tailings of these three PDFs. δ13C data of super-deep diamonds are from Cartigny et al. (2014)

Cartigny, P., Palot, M., Thomassot, E., Harris, J.W. (2014) Diamond Formation: A Stable Isotope Perspective. Annual Review of Earth and Planetary Sciences 42, 699–732.

.
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