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Bridging the depleted MORB mantle and the continental crust using titanium isotopes

Z. Deng1,

1Institut de Physique du Globe de Paris, Université Paris Diderot, Université Sorbonne Paris Cité, CNRS UMR 7154, 1 rue Jussieu, 75005, Paris, France

F. Moynier1,2,

1Institut de Physique du Globe de Paris, Université Paris Diderot, Université Sorbonne Paris Cité, CNRS UMR 7154, 1 rue Jussieu, 75005, Paris, France
2Institut Universitaire de France, Paris, France

P.A. Sossi1,

1Institut de Physique du Globe de Paris, Université Paris Diderot, Université Sorbonne Paris Cité, CNRS UMR 7154, 1 rue Jussieu, 75005, Paris, France

M. Chaussidon1

1Institut de Physique du Globe de Paris, Université Paris Diderot, Université Sorbonne Paris Cité, CNRS UMR 7154, 1 rue Jussieu, 75005, Paris, France

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Deng, Z., Moynier, F., Sossi, P.A., Chaussidon, M. (2018) Bridging the depleted MORB mantle and the continental crust using titanium isotopes. Geochem. Persp. Let. 9, 11–15

Research funded by the ERC under H2020 framework program/ERC grant agreement #637503 (Pristine), the UnivEarthS Labex program at Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02), and IGPG multidisciplinary program PARI, and by Region Île-de-France SESAME Grant no. 12015908.

Geochemical Perspectives Letters v9  |  doi: 10.7185/geochemlet.1831
Received 23 July 2018  |  Accepted 27 October 2018  |  Published 13 December 2018
Copyright © The Authors

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




Figure 1 Positive correlation between δ49Ti and (La/Sm)N values for the komatiite and MORB samples.
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Figure 2 The change of δ49Ti values with time for the komatiite and MORB samples. The average δ49Ti values for the depleted and primitive groups are indicated. Also shown are the average of 12 chondrite groups with 2 sd uncertainty from Deng et al. (2018)

Deng, Z., Moynier, F., van Zuilen, K., Sossi, P.A., Pringle, E.A., Chaussidon, M. (2018) Lack of resolvable titanium stable isotopic variations in bulk chondrites. Geochimica et Cosmochimica Acta 239, 409−419.

and the continental crust value inferred from shale data from Greber et al. (2017b)

Greber, N.D., Dauphas, N., Bekker, A., Ptáček, M.P., Bindeman, I.N., Hofmann, A. (2017b) Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago. Science 357, 1271−1274.

.
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Figure 3 Modelling the Ti isotopic fractionations in the partial melts and residues from partial melting of the mantle or the crust. The grey area in (a) indicates the remaining Ti fraction in the residual mantle after ≈ 8-9 % partial melting (DTi ≈ 0.132; Prytulak and Elliott, 2007

Prytulak, J., Elliott, T. (2007) TiO2 enrichment in ocean island basalts. Earth and Planetary Science Letters 263, 388−403.

), i.e. process (i) illustrated in (b). The orange field in a shows the Ti fraction after 20-30 % partial melting of a basaltic crust to produce the felsic melts equivalent to tonalite-trondhjemite-granodiorite (TTGs) (DTi ≈ 3.2-3.3; Martin et al., 2014

Martin, H., Moyen, J.F., Guitreau, M., Blichert-Toft, J., Le Pennec, J.L. (2014) Why Archean TTG cannot be generated by MORB melting in subduction zones. Lithos 198, 1−13.

), i.e. process (ii) in b. The Δ49Tiresidue−source values of TTGs and corresponding residues were calculated using the Ti isotope data of TTG samples from Greber et al. (2017b)

Greber, N.D., Dauphas, N., Bekker, A., Ptáček, M.P., Bindeman, I.N., Hofmann, A. (2017b) Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago. Science 357, 1271−1274.

and assuming E-MORBs as their sources.
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