Sr-Nd-Hf isotopes along the Pacific Antarctic Ridge from 41 to 53°S

C. Hamelin (1, 2) , Laure Dosso (1) , B. Hanan (3) , Jean-Alix J-A Barrat (1) , Hélène Ondréas (4)

1 LDO - Domaines Océaniques
2 IPGP - Institut de Physique du Globe de Paris
3 Geological Sciences
4 IFREMER - Institut Français de Recherche pour l'Exploitation de la Mer

Major, trace element and Sr-Nd-Hf isotope data in basalts collected along the Pacific-Antarctic Ridge (PAR) axis between 53 and 41°S, far from any hotspot influence, reveal tight coherent geochemical variations within the depleted MORB mantle. All samples are located below the Pacific reference line defining two sub-oceanic mantle domains on each side of the Easter microplate. The data extend the PAR 66-53°S field towards more radiogenic Sr (0.70264), less radiogenic Nd (ɛ = 7.7) and Hf (ɛ = 11.4) values. The along ridge geochemical variability is closely related to the morphological segmentation of the ridge. Anomalous geochemical features are attributed to the atypical morphology of two segments due to the presence of off-axis magmatism. The first order ridge discontinuity defined by the Menard transform fault separates two slightly different mantle domains, each with its own history.

Mots clés: Pacific-Antarctic; depleted mantle; Sr-Nd-Hf isotopes

Domaines: Géochimie; Milieux et Changements globaux

C. Hamelin, Laure Dosso, B. Hanan, Jean-Alix J-A Barrat, Hélène Ondréas. Sr-Nd-Hf isotopes along the Pacific Antarctic Ridge from 41 to 53°S. Geophysical Research Letters, 2010, 37, pp.L10303. ⟨10.1029/2010GL042979⟩. ⟨insu-00563384⟩