Sr-Nd and Pb isotopic portrait of the Crozet plume

• Published in: Mineralogical Magazine
• Main Authors: MEYZEN, CHRISTINE MARIE, MARZOLI, ANDREA, BELLIENI, GIULIANO, G. Levresse
• Other Authors: Meyzen, CHRISTINE MARIE, Marzoli, Andrea, Bellieni, Giuliano, G., Levresse
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: Crozet Islands
• Online Access: http://hdl.handle.net/11577/2684866; https://doi.org/10.1180/minmag.2013.077.5.13; http://goldschmidt.info/2013/

New Sr, Nd and Pb isotope data are presented for alkali basalts of the sub-aerial eruptive stage of East Island. This landmass is the second largest of the easternmost and oldest island group of Crozet archipelago. Its lavas are remarkably isotopically homogeneous in spanning a narrow range of isotopic variability. They occupy an intermediate position among the isotopic variability spectrum defined by Earth’s oceanic island basalts. They fall in a mixing triangular shape formed by the end-member mantle components: a Depleted Mantle (DM) component, an Enriched Mantle (EM) component and a common component. The mixture domination by a large fraction of the common component suggests an isolation of the East island mantle source from homogenizing effects of convection mixing and recycling processes for Ga timescales. A possible inter-island source heterogeneity, such as those identified in the Pacific and Atlantic oceans, could exist at Crozet islands, as the younger western group is more isotopically depleted in Sr-Nd than the eastern one. Overall, lavas from Crozet islands share Pb-Sr-Nd isotopic affinities with their Reunion-Mauritius counterparts, but differ from those of Marion-Prince Edward and Kerguelen volcanoes. However, we cannot reject the seismic inference that Crozet volcanism is a secondary expression of Kerguelen hotspot, if its compositional bottom layer is heterogeneous. Finally, the Sr-Nd-Pb isotopic signatures of basalts north of the Crozet Bank along the Southwest Indian Ridge show no affinity with those of East island. The seismically ridgeward flow identified must thus be composed of isotopically distinct material from that of feeding East island volcanism.