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dc.contributor.authorMikhail, Sami
dc.contributor.authorGuillermier, Christalle
dc.contributor.authorFranchi, Ian
dc.contributor.authorBeard, Andrew
dc.contributor.authorKrispin, Catherine
dc.contributor.authorVerchovsky, Alexander
dc.contributor.authorJones, Adrian
dc.contributor.authorMilledge, H Judith
dc.identifier.citationMikhail , S , Guillermier , C , Franchi , I , Beard , A , Krispin , C , Verchovsky , A , Jones , A & Milledge , H J 2014 , ' Empirical evidence for the fractionation of carbon isotopes between diamond and iron carbide from the Earth’s mantle ' , Geochemistry, Geophysics, Geosystems , vol. 15 , no. 4 , pp. 855–866 .
dc.identifier.otherPURE: 232148902
dc.identifier.otherPURE UUID: 5cf57f05-1f07-4cf4-a952-5cae1fa60d69
dc.identifier.otherScopus: 84901371800
dc.identifier.otherORCID: /0000-0001-5276-0229/work/37274388
dc.descriptionS.M. would like to thank the Engineering and Physical Sciences Research Council, the Diamond Trading Company, and the Department of Physical Sciences, The Open University (UK) for financial support during his time as a PhD student at University College London (UK). Date of Acceptance: 01/01/2014en
dc.description.abstractWe have studied two samples of mantle diamond containing iron carbide inclusions from Jagersfontein kimberlite, South Africa. Syngenetic crystal growth is inferred using morphological characteristics. These samples provide an opportunity to investigate the isotopic partitioning of 13C in a terrestrial natural high-pressure and high-temperature (HPHT) system. The difference for the δ13C values between the diamond and coexisting iron carbide averaged 7.2 ± 1.3‰. These data are consistent with available data from the literature showing iron carbide to be 13C-depleted relative to elemental carbon (i.e., diamond). We infer that the minerals formed by crystallization of diamond and iron carbide at HPHT in the mantle beneath the Kaapvaal Craton. It is unclear whether crystallization occurred in subcratonic or sublithospheric mantle; in addition, the source of the iron is also enigmatic. Nonetheless, textural coherence between diamond and iron carbide resulted in isotopic partitioning of 13C between these two phases. These data suggest that significant isotopic fractionation of 13C/12C (Δ13C up to >7‰) can occur at HPHT in the terrestrial diamond stability field. We note that under reducing conditions at or below the iron-iron wustite redox buffer in a cratonic or deep mantle environment in Earth, the cogenesis of carbide and diamond may produce reservoirs of 13C-depleted carbon that have conventionally been interpreted as crustal in origin. Finally, the large Δ13C for diamond-iron carbide shown here demonstrates Δ13C for silicate-metallic melts is a parameter that needs to be constrained to better determine the abundance of carbon within the Earth's metallic core.
dc.relation.ispartofGeochemistry, Geophysics, Geosystemsen
dc.rightsCopyright 2014. American Geophysical Union. All Rights Reserved. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at:
dc.subjectCarbon isotope fractionationen
dc.subjectDeep carbon cycleen
dc.subjectIron carbideen
dc.subjectQE Geologyen
dc.titleEmpirical evidence for the fractionation of carbon isotopes between diamond and iron carbide from the Earth’s mantleen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews.Earth and Environmental Sciencesen
dc.contributor.institutionUniversity of St Andrews.St Andrews Isotope Geochemistryen
dc.description.statusPeer revieweden

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