Helium isotopes on the Macdonald seamount (Austral chain): constraints on the origin of the superswell
Abstract
We present new helium isotope data from the Macdonald seamount (Austral chain). The helium isotopic ratio varies from 4He/ 3He=45 000 (R/Ra=16.0) to 200 170 (R/Ra=3.6). The helium content is between 1.5×10 -8 and 1.1×10 -5 ccSTP/g. These helium results show clearly the presence of primitive mantle material in the source of the Austral chain. Macdonald has the lowest 4He/ 3He ratio among the Polynesian submarine volcanoes, except Hawaii (Loihi). The simplest explanation for the primitive helium signature is the presence under Macdonald of a mantle plume that derives either from the 670 km or 2900 km boundary layers, or, eventually, from the top of a large mantle dome resulting from a stratified two-layer convection. This plume contains less-degassed material with low 4He/ 3He ratio. To cite this article: M. Moreira, C. Allègre, C. R. Geoscience 336 (2004).
- Publication:
-
Comptes Rendus Geoscience
- Pub Date:
- August 2004
- DOI:
- 10.1016/j.crte.2004.04.006
- Bibcode:
- 2004CRGeo.336..983M