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CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle


Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth’s mantle. Discoveries of some of these minerals in ‘super-deep’ diamonds—formed between two hundred and about one thousand kilometres into the lower mantle—have confirmed part of this picture1,2,3,4,5. A notable exception is the high-pressure perovskite-structured polymorph of calcium silicate (CaSiO3). This mineral—expected to be the fourth most abundant in the Earth—has not previously been found in nature. Being the dominant host for calcium and, owing to its accommodating crystal structure, the major sink for heat-producing elements (potassium, uranium and thorium) in the transition zone and lower mantle, it is critical to establish its presence. Here we report the discovery of the perovskite-structured polymorph of CaSiO3 in a diamond from South African Cullinan kimberlite. The mineral is intergrown with about six per cent calcium titanate (CaTiO3). The titanium-rich composition of this inclusion indicates a bulk composition consistent with derivation from basaltic oceanic crust subducted to pressures equivalent to those present at the depths of the uppermost lower mantle. The relatively ‘heavy’ carbon isotopic composition of the surrounding diamond, together with the pristine high-pressure CaSiO3 structure, provides evidence for the recycling of oceanic crust and surficial carbon to lower-mantle depths.

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Figure 1: Cathodoluminescence image and carbon isotopic composition of the diamond containing the Ca-Pv inclusion.
Figure 2: Backscattered-electron image of the Ca-Pv inclusion and energy-dispersive X-ray spectroscopy elemental maps.
Figure 3: Ewald projections of X-ray diffraction data and Raman spectroscopy results.
Figure 4: EBSD images of the Ca-Pv inclusion in diamond.


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We thank M. Regier for proofreading the paper. F.N. is supported by the European Research Council (ERC) Starting Grant number 307322. M.K.’s work and sample collection was possible thanks to an NSERC Discovery grant. N.K. acknowledges funding from the Dr. Eduard Gübelin Association through a 2015 research scholarship. D.G.P. was funded by an NSERC CERC award. M.A. was supported by the ERC under the European Union’s Horizon 2020 research and innovation programme (grant 714936) ‘TRUE DEPTHS’ and by the SIR-MIUR grant (RBSI140351) ‘MILE DEEp’. We thank L. Litti and M. Meneghetti of the Laboratory of Nanostructures and Optics of the Department of Chemical Sciences, University of Padova for their help in acquiring and interpreting the Raman data. F.N. and D.G.P. were supported by the Deep Carbon Observatory. M.G.P. was supported by NERC grant NE/M015181/1.

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Authors and Affiliations



F.N. conceived the study, wrote the initial manuscript and performed X-ray diffraction and micro-Raman measurements. N.K. found the mineral, made original mineral identifications on a confocal Raman spectrometer, performed microprobe and cathodoluminescence measurements, prepared samples for secondary ion mass spectrometry measurements and assisted with the manuscript preparation. M.K. supervised the study of the Cullinan diamond collection, which was acquired by J.J.G., A.E.M. and J.D., and assisted with the manuscript preparation. D.G.P. made the geochemical interpretations and led the manuscript revisions. M.G.P. assisted with the manuscript preparation and crystallographic interpretations. N.R., M.G.P. and M.A. assisted with the X-ray data interpretation. L.P. collected and interpreted the EBSD data. J.J.G., A.E.M. and J.D. designed the sampling programme.

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Correspondence to F. Nestola.

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Reviewer Information Nature thanks B. Harte and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Figure 1 Baseline-corrected FTIR absorption spectrum of the diamond containing the Ca-Pv inclusion.

The inset shows the absorption peaks of two types of diamond defect: A-aggregate N, in which a pair of nitrogen atoms substitute carbon atoms (the ‘A-centre’), and B-aggregate N, in which four nitrogen atoms replace carbon atoms around a carbon vacancy (the ‘B-centre’). The values in parentheses give the theoretical peak positions (in cm−1).

Extended Data Figure 2 Comparison between the Raman spectrum of CaTiO3 measured in this work (blue) and that reported in the RRUFF database (red).

The spectrum reported in the RRUFF database (card number R050456) is from ref. 23.

Extended Data Table 1 Results of the chemical analysis of the Ca-Pv
Extended Data Table 2 d spacings, their corresponding relative intensities I (with respect to the most intense peak, at I = 100), and h, k, l indices for Ca-Pv, as obtained by single-crystal X-ray micro-diffraction
Extended Data Table 3 Carbon isotopic composition (δ13C, in parts per thousand) and relative uncertainty for the host diamond enclosing the Ca-Pv inclusion

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Nestola, F., Korolev, N., Kopylova, M. et al. CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle. Nature 555, 237–241 (2018).

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