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The non-chondritic Ni isotopic composition of the Earth's mantle

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The non-chondritic Ni isotopic composition of the Earth's mantle. / Klaver, Martijn; Ionov, Dmitri; Takazawa, Eiichi; Elliott, Tim.

In: Geochimica et Cosmochimica Acta, Vol. 268, 01.01.2020, p. 405-421.

Research output: Contribution to journalArticle (Academic Journal)

Harvard

Klaver, M, Ionov, D, Takazawa, E & Elliott, T 2020, 'The non-chondritic Ni isotopic composition of the Earth's mantle', Geochimica et Cosmochimica Acta, vol. 268, pp. 405-421. https://doi.org/10.1016/j.gca.2019.10.017

APA

Klaver, M., Ionov, D., Takazawa, E., & Elliott, T. (2020). The non-chondritic Ni isotopic composition of the Earth's mantle. Geochimica et Cosmochimica Acta, 268, 405-421. https://doi.org/10.1016/j.gca.2019.10.017

Vancouver

Klaver M, Ionov D, Takazawa E, Elliott T. The non-chondritic Ni isotopic composition of the Earth's mantle. Geochimica et Cosmochimica Acta. 2020 Jan 1;268:405-421. https://doi.org/10.1016/j.gca.2019.10.017

Author

Klaver, Martijn ; Ionov, Dmitri ; Takazawa, Eiichi ; Elliott, Tim. / The non-chondritic Ni isotopic composition of the Earth's mantle. In: Geochimica et Cosmochimica Acta. 2020 ; Vol. 268. pp. 405-421.

Bibtex

@article{6bf4bfb36b7d48aab39c9e41d5b9be66,
title = "The non-chondritic Ni isotopic composition of the Earth's mantle",
abstract = "Nickel is a major element in the Earth. Due to its siderophile nature, 93% of Ni is hosted in the core and the Ni isotope composition of the bulk silicate Earth might inform on the conditions of terrestrial core formation. Whether Earth{\textquoteright}s mantle is fractionated relative to the chondritic reservoir, and by inference to the core, is a matter of debate that largely arises from the uncertain Ni isotope composition of the mantle. We address this issue through high-precision Ni isotope measurements of fertile- to melt-depleted peridotites and compare these data to chondritic meteorites. Terrestrial peridotites that are free from metasomatic overprint display a limited range in δ60/58Ni (deviation of 60Ni/58Ni relative to NIST SRM 986) and no systematic variation with degree of melt depletion. The latter is consistent with olivine and orthopyroxene buffering the Ni budget and isotope composition of the refractory peridotites. As such, the average Ni isotope composition of these peridotites (δ60/58Ni = 0.115 ± 0.011‰) provides a robust estimate of the δ60/58Ni of the bulk silicate Earth. Peridotites with evidence for melt metasomatism range to heavier Ni isotope compositions where the introduction of clinopyroxene appears to drive an increase in δ60/58Ni. This requires a process where melts do not reach isotopic equilibrium with buffering olivine and orthopyroxene, but its exact nature remains obscure. Chondritic meteorites have variability in δ60/58Ni due to heterogeneity at the sampling scale. In particular, CI1 chondrites are displaced to isotopically lighter values due to sorption of Ni onto ferrihydrite during parent body alteration. Chondrites less extensively altered than the CI1 chondrites show no systematic differences in δ60/58Ni between classes and yield average δ60/58Ni = 0.212 ± 0.013‰, which is isotopically heavier than our estimate of the bulk silicate Earth. The notable isotopic difference between the bulk silicate Earth and chondrites likely results from the segregation of the terrestrial core. Our observations potentially provide a novel constraint on the conditions of terrestrial core formation but requires further experimental calibration.",
keywords = "Ni mass-dependent isotope variations, Bulk silicate Earth, Peridotites, Chondrites, Core formation",
author = "Martijn Klaver and Dmitri Ionov and Eiichi Takazawa and Tim Elliott",
year = "2020",
month = jan,
day = "1",
doi = "10.1016/j.gca.2019.10.017",
language = "English",
volume = "268",
pages = "405--421",
journal = "Geochimica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier",

}

RIS - suitable for import to EndNote

TY - JOUR

T1 - The non-chondritic Ni isotopic composition of the Earth's mantle

AU - Klaver, Martijn

AU - Ionov, Dmitri

AU - Takazawa, Eiichi

AU - Elliott, Tim

PY - 2020/1/1

Y1 - 2020/1/1

N2 - Nickel is a major element in the Earth. Due to its siderophile nature, 93% of Ni is hosted in the core and the Ni isotope composition of the bulk silicate Earth might inform on the conditions of terrestrial core formation. Whether Earth’s mantle is fractionated relative to the chondritic reservoir, and by inference to the core, is a matter of debate that largely arises from the uncertain Ni isotope composition of the mantle. We address this issue through high-precision Ni isotope measurements of fertile- to melt-depleted peridotites and compare these data to chondritic meteorites. Terrestrial peridotites that are free from metasomatic overprint display a limited range in δ60/58Ni (deviation of 60Ni/58Ni relative to NIST SRM 986) and no systematic variation with degree of melt depletion. The latter is consistent with olivine and orthopyroxene buffering the Ni budget and isotope composition of the refractory peridotites. As such, the average Ni isotope composition of these peridotites (δ60/58Ni = 0.115 ± 0.011‰) provides a robust estimate of the δ60/58Ni of the bulk silicate Earth. Peridotites with evidence for melt metasomatism range to heavier Ni isotope compositions where the introduction of clinopyroxene appears to drive an increase in δ60/58Ni. This requires a process where melts do not reach isotopic equilibrium with buffering olivine and orthopyroxene, but its exact nature remains obscure. Chondritic meteorites have variability in δ60/58Ni due to heterogeneity at the sampling scale. In particular, CI1 chondrites are displaced to isotopically lighter values due to sorption of Ni onto ferrihydrite during parent body alteration. Chondrites less extensively altered than the CI1 chondrites show no systematic differences in δ60/58Ni between classes and yield average δ60/58Ni = 0.212 ± 0.013‰, which is isotopically heavier than our estimate of the bulk silicate Earth. The notable isotopic difference between the bulk silicate Earth and chondrites likely results from the segregation of the terrestrial core. Our observations potentially provide a novel constraint on the conditions of terrestrial core formation but requires further experimental calibration.

AB - Nickel is a major element in the Earth. Due to its siderophile nature, 93% of Ni is hosted in the core and the Ni isotope composition of the bulk silicate Earth might inform on the conditions of terrestrial core formation. Whether Earth’s mantle is fractionated relative to the chondritic reservoir, and by inference to the core, is a matter of debate that largely arises from the uncertain Ni isotope composition of the mantle. We address this issue through high-precision Ni isotope measurements of fertile- to melt-depleted peridotites and compare these data to chondritic meteorites. Terrestrial peridotites that are free from metasomatic overprint display a limited range in δ60/58Ni (deviation of 60Ni/58Ni relative to NIST SRM 986) and no systematic variation with degree of melt depletion. The latter is consistent with olivine and orthopyroxene buffering the Ni budget and isotope composition of the refractory peridotites. As such, the average Ni isotope composition of these peridotites (δ60/58Ni = 0.115 ± 0.011‰) provides a robust estimate of the δ60/58Ni of the bulk silicate Earth. Peridotites with evidence for melt metasomatism range to heavier Ni isotope compositions where the introduction of clinopyroxene appears to drive an increase in δ60/58Ni. This requires a process where melts do not reach isotopic equilibrium with buffering olivine and orthopyroxene, but its exact nature remains obscure. Chondritic meteorites have variability in δ60/58Ni due to heterogeneity at the sampling scale. In particular, CI1 chondrites are displaced to isotopically lighter values due to sorption of Ni onto ferrihydrite during parent body alteration. Chondrites less extensively altered than the CI1 chondrites show no systematic differences in δ60/58Ni between classes and yield average δ60/58Ni = 0.212 ± 0.013‰, which is isotopically heavier than our estimate of the bulk silicate Earth. The notable isotopic difference between the bulk silicate Earth and chondrites likely results from the segregation of the terrestrial core. Our observations potentially provide a novel constraint on the conditions of terrestrial core formation but requires further experimental calibration.

KW - Ni mass-dependent isotope variations

KW - Bulk silicate Earth

KW - Peridotites

KW - Chondrites

KW - Core formation

U2 - 10.1016/j.gca.2019.10.017

DO - 10.1016/j.gca.2019.10.017

M3 - Article (Academic Journal)

VL - 268

SP - 405

EP - 421

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

SN - 0016-7037

ER -