Répertoire du personnel
Jean-Paul Liégeois
Sciences de la Terre
Géodynamique et ressources minérales
Géodynamique et ressources minérales
Détails
Bardintzeff, J.M., Liégeois, J.P., Bonin, B., Bellon, H. & Rasamimanana, G. 2010. ‘Madagascar volcanic provinces linked to the Gondwana break-up: geochemical and isotopic evidences for contrasting mantle sources’. Gondwana Research. Amsterdam : Elsevier. DOI: DOI:10.1016/j.gr.2009.11.010. I.F. 3.728.
Article dans une revue scientifique / Article dans un périodique
After the Gondwana break-up and Greater India splitting off, Madagascar suffered volcanic episodes. The Cretaceous Morondava flood basalt (CFB) province was emplaced ca. 93 Ma ago. Two coeval high-Ti–P (HTP) and low-Ti–P (LTP) suites are distributed within the alkaline Ankilizato (central) and tholeiitic Manamana (southern) sub-provinces. Sr–Nd isotope compositions display a trend from depleted (åNd=+7.5; Sri=0.7030; Antsoha end-member) to highly enriched products (åNd=−17; Sri=0.7228; Manamana end-member). Antsoha end-member is considered to be located at the lithosphere–asthenosphere boundary while the composition of Manamana end-member implies a location within the Archean to Proterozoic continental lithosphere. Oligocene Ankaratra HTP alkaline province, Miocene Ankilioaka transitional province, Pliocene Ambre Mountain and Pleistocene Nosy Be Island alkaline volcanoes display a restricted isotopic range (åNd=+4 to 0; Sri=0.7032 to 0.7048) forming an array distinct from the Cretaceous trend, implying the enriched pole did not correspond to Manamana end-member. This Cenozoic array could result from mixing between Antsoha end-member and BSE or a pole beyond. The exceptional variation of mantle sources involved in the Cretaceous episode contrasts with the more homogeneous near-BSE source during the Cenozoic. Several lines of evidence dismiss the mantle plume model. Cretaceous volcanism resulted from reactivation of a lithospheric scale shear zone due to plate reorganisation that eventually led to the Madagascar–India continental break-up. The lower lithospheric/asthenospheric melt (Antshoha endmember) was able to melt the most enriched/fusible parts of an upper lithospheric mantle (Manamana end-member); these two melts partly mixed. Long-lasting Neogene volcanic activity was less voluminous. The melting source was restricted to a lower part of the lithospheric mantle.