A "high He-4/He-3" mantle material detected under the East Pacific Rise (15 degrees 4 ' N)

Type Article
Date 2015-03
Language English
Author(s) Mougel Berengere1, 2, Moreira Manuel1, Agranier Arnaud2
Affiliation(s) 1 : Inst Phys Globe Paris, Sorbonne Paris Cite, CNRS, UMR, Paris, France.
2 : IUEM, Lab Domaines Ocean, UMR6538, Plouzane, France.
Source Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2015-03 , Vol. 42 , N. 5 , P. 1375-1383
DOI 10.1002/2014GL062921
WOS© Times Cited 9
Note This article also appears in: 2015 GRL Editor Highlights
Keyword(s) helium, isotopes, mantle geochemistry, MORB, hot spot, EPR

We investigate in details helium isotope data reported in Mougel et al. (2014) for 14 basaltic samples collected on the East Pacific Rise by submersible (15 degrees 4N) where the ridge interacts with the Mathematician seamounts. Samples locations are separated by only few hundred meters across a 15km along-axis profile. The data reveal a strong geochemical variability that has never been observed at such high spatial resolution for helium isotope compositions. Moreover, they reveal an unusually high He-4/He-3 mantle component also characterized by unradiogenic lead, atypical in oceanic basalts. He-Pb systematics suggests a mixture between a nonradiogenic lead and radiogenic helium pyroxenitic component, recycled from the deep continental lithosphere and the ambient peridotitic mantle. The He isotope difference between these two end-members can be interpreted as a time evolution of two distinct mantle sources after a slight (U+Th)/He-3 fractionation, likely due to some ancient degassing during the formation of deep continental pyroxenites.

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