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Hadean protocrust reworking at the origin of the Archean Napier Complex (Antarctica)

M. Guitreau1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

M. Boyet1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

J.-L. Paquette1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

A. Gannoun1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

Z. Konc1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

M. Benbakkar1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

K. Suchorski1,

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

J.-M. Hénot1

1Université Clermont Auvergne, IRD, CNRS, OPGC, Laboratoire Magmas et Volcans, UMR 6524, F-63000 Clermont-Ferrand, France

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Guitreau, M., Boyet, M., Paquette, J.-L., Gannoun, A., Konc, Z., Benbakkar, M., Suchorski, K., Hénot, J.-M. (2019) Hadean protocrust reworking at the origin of the Archean Napier Complex (Antarctica). Geochem. Persp. Let. 12, 7–11.

Région Auvergne, the French Agence Nationale de la Recherche (ANR) through LabEx ClerVolc (ANR-10-LABX-0006) and project Zircontinents (ANR-17-CE31-0021), and the European Union’s Horizon 2020 research and innovation program (Grant Agreement N° 682778).

Geochemical Perspectives Letters v12  |  doi: 10.7185/geochemlet.1927
Received 28 June 2019  |  Accepted 19 September 2019  |  Published 8 November 2019
Copyright © The Authors

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




Figure 1 Cathodoluminescence images of representative crystals from Napier zircon populations with details of textures with and without annealing. This figure illustrates the CL signal enhancing effect of zircon annealing which, in turn, allows three groups to be identified based on internal textures (see text for details). Thick white bars represent 50 μm.
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Figure 2 ɛHf versus 207Pb/206Pb age diagrams for Mount Sones and Gage Ridge zircons. Black dashed lines represent the time-evolution of a CHUR reservoir (Iizuka et al., 2015

Iizuka, T., Yamaguchi, T., Hibiya, Y., Amelin, Y. (2015) Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth. Proceedings of the National Academy of Science 112, 5331-5336.

) formed at 4568 Ma (Bouvier and Wadhwa, 2010

Bouvier, A., Wadhwa, M. (2010) The age of the Solar System redefined by the oldest Pb-Pb age of a meteoritic inclusion. Nature Geoscience 3, 637-641.

). Black dotted lines correspond to reservoirs that started with group 1 initial 176Hf/177Hf and evolved with 176Lu/177Hf ratios that are indicated on the left of the diagrams (e.g., 0.025). The values of 0.002 and 0.0016 correspond to 176Lu/177Hf measured in whole rock powders of Mount Sones and Gage Ridge orthogneisses, respectively. The grey fields encompass evolutions of Napier zircons based on highest and lowest 176Lu/177Hf measured in Mount Sones and Gage Ridge zircon populations. The general positive correlation of data for group 1 highlights typical artefacts of ancient Pb loss (e.g., Guitreau et al., 2012

Guitreau, M., Blichert-Toft, J., Martin, H., Mojzsis, S.J., Albarède, F. (2012) Hafnium isotope evidence from Archean granitic rocks for deep-mantle origin of continental crust. Earth and Planetary Science Letters 337, 211-223.

). Therefore, the original Hf isotope signatures of corresponding zircon populations are indicated by the oldest (and most concordant) crystals, which happen to be sub-chondritic for both samples. Data are fully consistent between annealed and not-annealed zircons, hence, demonstrating that annealing did not influence any of the measured systematics.
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Figure 3 Coupled 146Sm-142Nd and 147Sm-143Nd plot showing the data obtained for Mount Sones orthogneiss (78285007) as well as the coupled evolution of μ142Nd and ɛ143Nd signatures for lithologies with various Sm/Nd ratios. Solid lines represent isochrons with respective ages indicated by ∆T, which means time after 4568 Ma. Dashed curves correspond to the coupled evolution of μ142Nd and ɛ143Nd signatures according to specific 147Sm/144Nd values that are indicated next to the curves (i.e. 0.14-0.19). Mount Sones μ142Nd and ɛ143Nd isotope signatures are compatible with a mafic source (147Sm/144Nd = 0.17) that separated from a reservoir with a chondritic REE pattern ~150 Myr after Solar System formation (i.e. ~4400 Myr ago). Here we assume that the initial 142Nd/144Nd ratio of the Earth is similar to that measured in the modern terrestrial mantle (μ142Nd = 0), which is equivalent to the signature measured in enstatite chondrites from the EL sub-group (Boyet et al., 2018

Boyet, M., Bouvier, A., Frossard, P., Hammouda, T., Garçon, M., Gannoun, A. (2018) Enstatite chondrites EL3 as building blocks for the Earth: the debate over the 146Sm-142Nd systematics. Earth and Planetary Science Letters 488, 68-78.

).
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