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The xenon isotopic signature of the mantle beneath Massif Central

M. Moreira1,

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

V. Rouchon2,

2IFP Energies Nouvelles, 1 et 4 avenue de Bois-Préau, 92852 Rueil-Malmaison Cedex, France

E. Muller1,

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

S. Noirez2,

2IFP Energies Nouvelles, 1 et 4 avenue de Bois-Préau, 92852 Rueil-Malmaison Cedex, France

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Moreira, M., Rouchon, V., Muller, E., Noirez, S. (2018) The xenon isotopic signature of the mantle beneath Massif Central. Geochem. Persp. Let. 6, 28–32.

Labex UnivEarthS

Geochemical Perspectives Letters v6  |  doi: 10.7185/geochemlet.1805
Received 21 September 2017  |  Accepted 29 January 2018  |  Published 22 February 2018
Copyright © The Authors

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

Keywords: noble gases, Central European Volcanic Province, xenon, Massif Central




Figure 1 Three-neon isotope diagram. MORB data are from Moreira et al. (1998)

Moreira, M., Kunz, J., Allègre, C.J. (1998) Rare gas systematics on popping rock : estimates of isotopic and elemental compositions in the upper mantle. Science 279, 1178-1181.

and define the MORB-AIR mixing line (Sarda et al., 1988

Sarda, P., Staudacher, T., Allègre, C.J. (1988) Neon isotopes in submarine basalts. Earth and Planetary Science Letters 91, 73-88.

), which has a different slope than the OIB mixing lines (Honda et al., 1991

Honda, M., McDougall, I., Patterson, D.B., Doulgeris, A., Clague, D. (1991) Possible solar noble-gas component in Hawaiian basalts. Nature 349, 149-151.

; Moreira et al., 2001

Moreira, M., Breddam, K., Curtice, J., Kurz, M. (2001) Solar neon in the Icelandic mantle: evidence for an undegassed lower mantle. Earth and Planetary Science Letters 185.

). The OIB mixing lines are from Mukhopadhyay (2012)

Mukhopadhyay, S. (2012) Early differentiation and volatile accretion recorded in deep mantle Neon and Xenon. Nature 486, 101-104.

and Peron et al. (2016)

Peron, S., Moreira, M., Colin, A., Arbaret, L., Putlitz, B., Kurz, M.D. (2016) Neon isotopic composition of the mantle constrained by single vesicles analyses. Earth and Planetary Science Letters 449, 145–154.

. The MORB source has a 20Ne/22Ne ~12.5. The neon in Lignat spring comes from the mixture of mantle-derived (~12 %) and atmospheric neon (~88 %). Data from the Eifel area are also reported (Brauer et al., 2013

Brauer, K., Kampf, H., Niedermann, S., Strauch, G. (2013) Indications for the existence of different magmatic reservoirs beneath the Eifel area (Germany): A multi-isotope (C, N, He, Ne, Ar) approach. Chemical Geology 356, 193-208.

).
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Figure 2 Xenon isotopes in the Lignat gas (aliquots: small red dots; mean: large red dot), compared to MORB (Kunz et al., 1998

Kunz, J., Staudacher, T., Allègre, C.J. (1998) Plutonium-Fission Xenon Found in Earth's Mantle. Science 280, 877-880.

; Parai et al., 2012

Parai, R., Mukhopadhyay, S., Standish, J.J. (2012) Heterogeneous upper mantle Ne,Ar and Xe isotopic compositions and a possible Dupal noble gas signature recorded in basalts from the Southwest Indian Ridge. Earth and Planetary Science Letters 359-360, 227-239.

; Tucker et al., 2012

Tucker, J.M., Mukhopadhyay, S., Schilling, J.-G. (2012) The heavy noble gas composition of the depleted MORB mantle (DMM) and its implications for the preservation of heterogeneities in the mantle. Earth and Planetary Science Letters 355-356, 244-254.

) and Iceland basalts (Mukhopadhyay, 2012

Mukhopadhyay, S. (2012) Early differentiation and volatile accretion recorded in deep mantle Neon and Xenon. Nature 486, 101-104.

). The Eifel gas is shown for comparison (small blue squares: aliquots, large blue square: mean) (Caracausi et al., 2016

Caracausi, A., Avice, G., Burnard, P., Furi, E., Marty, B. (2016) Chondritic xenon in the Earth’s mantle. Nature 533, 82-85.

). The inserts represent the global scale of variation in mantle-derived samples.
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Figure 3 Xenon isotopic ratios in the Lignat gas expressed in ‰ deviation relative to the atmospheric composition. Assuming the xenon composition reflects mixing between air and MORB (or CO2-well gas; Holland and Ballentine, 2006

Holland, G., Ballentine, C.J. (2006) Seawater subduction controls the heavy noble gas composition of the mantle. Nature 441, 186-191.

), one can estimate the proportion of atmospheric xenon. Using the 136Xe/130Xe ratio, 95 % of the 130Xe in the Lignat source is sourced from the air. The other isotopic ratios can be estimated using this mixing proportion. Two patterns are given for the result of this mixing: violet using CO2-well gas and green using the mean MORB-source ratios (Table S-2). The Lignat gas satisfies a simple binary mixture between air and MORB. Although the Eifel gas (blue circles) shows the same pattern for fissiogenic isotopes, it exhibits notable excesses in light Xe isotopes that are unaccounted for by the MORB-AIR mixing model.
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