Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Contributions to Mineralogy and Petrology 995-1009 Picrite Vanuatu arc Aoba Island Si-undersaturated melts Melt inclusions 2011 PAR00007997 ENG Contributions to Mineralogy and Petrology 0010-7999 ISI:000295677500007 5 10.1007/s00410-011-0636-1 https://www.documentation.ird.fr/hor/PAR00007997 162 Horizon (IRD) Aoba picrites in Vanuatu arc (Southwestern Pacific) offer the opportunity to address the question of the origin of Si-undersaturated arc magmas, through the geochemical study of their olivine-hosted melt inclusions. These latter delineate a differentiation trend of calc-alkaline silica-undersaturated basalts, with typical trace-element patterns of arc magmas. The most primitive melt inclusions, preserved in olivines with Fo a parts per thousand yen 89, have normative nepheline compositions with CaO/Al2O3 > 0.8, but belong to three distinct populations differing in their enrichment or depletion in LILE, Cl, and alkalis (Rb, K). The dominant population is characterized by medium-LILE concentrations (La/Yb similar to 7-8) and represents the parental magma of the Aoba lavas. The two others (La/Yb similar to 20 and 2) are either significantly enriched or extremely depleted in LILE, Cl, and alkalis. This compositional variability of primitive magma batches requires the multi-stage mixing between melts generated by partial melting of both peridotite and clinopyroxene-rich lithologies. Medium-LILE magma derives from the mixing between peridotite- and clinopyroxenite-derived melts, whereas the high- and low-LILE melts involve amphibole-bearing and amphibole-free clinopyroxenite sources, respectively. 064 UR163 Vanuatu