Helium isotopes on the Pacific-Antarctic ridge (52.5°–41.5°S)

A. Moreira Manuel (1) , Laure Dosso (2) , Hélène Ondréas (3)

1 IPGP - Institut de Physique du Globe de Paris
2 LDO - Domaines Océaniques
3 GM - Unité Géosciences Marines

The first isotopic data and concentrations of helium are reported for the Pacific-Antarctic ridge between 52.5°S and 41.5°S. The 4He/3He ratio is extremely homogeneous over more than 1200 km, with a mean ratio of 99,275 (R/Ra = 7.29) and a standard deviation of 2719 (0.19), which is the lowest dispersion observed for the global mid oceanic ridge system. Moreover, the Menard T.F. is a frontier between two mantles with slightly different helium isotopic ratios (96,595 ± 1520 and 100,347 ± 2330). No difference in the helium concentration between the two ridge segments defined by the Menard T.F. can be observed, as well as no significant difference in the U and Th contents suggesting that the difference in helium isotopic ratio is old (>500 My) and may represent a slight difference in degassing or/and trace element depletion history

Mots clés: helium isotopes; mantle geochemistry; Pacific-Antarctic ridge

Domaines: Géochimie; Milieux et Changements globaux

A. Moreira Manuel, Laure Dosso, Hélène Ondréas. Helium isotopes on the Pacific-Antarctic ridge (52.5°–41.5°S). Geophysical Research Letters, 2008, 35, pp.L10306. ⟨10.1029/2008GL033286⟩. ⟨insu-00305185⟩