%0 Journal Article %T A " high 4 He/ 3 He " mantle material detected under the East Pacific Rise (15°4′N) %+ Institut de Physique du Globe de Paris (IPGP) %+ Domaines Océaniques (LDO) %A Mougel, Berengere %A Moreira, Manuel %A Agranier, Arnaud %< avec comité de lecture %@ 0094-8276 %J Geophysical Research Letters %I American Geophysical Union %V 42 %N 5 %P 1375–1383 %8 2015-03-16 %D 2015 %R 10.1002/2014GL062921 %Z Sciences of the Universe [physics]/Earth Sciences/GeochemistryJournal articles %X 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°4′N) where the ridge interacts with the Mathematician seamounts. Samples locations are separated by only few hundred meters across a 15 km 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 4 He/ 3 He 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)/ 3 He fractionation, likely due to some ancient degassing during the formation of deep continental pyroxenites. %G English %2 https://insu.hal.science/insu-01141460/document %2 https://insu.hal.science/insu-01141460/file/grl-mougel.pdf %L insu-01141460 %U https://insu.hal.science/insu-01141460 %~ INSU %~ UNIV-BREST %~ UNIV-PARIS7 %~ AFRIQ %~ CNRS %~ IPGP %~ LGO %~ CMM %~ UNIV-PARIS %~ GEO-OCEAN