Sorbadere F., Schiano Pierre, Metrich N., Garaebiti E. (2011). Insights into the origin of primitive silica-undersaturated arc magmas of Aoba volcano (Vanuatu arc). Contributions to Mineralogy and Petrology, 162 (5), p. 995-1009. ISSN 0010-7999.
Titre du document
Insights into the origin of primitive silica-undersaturated arc magmas of Aoba volcano (Vanuatu arc)
Sorbadere F., Schiano Pierre, Metrich N., Garaebiti E.
Source
Contributions to Mineralogy and Petrology, 2011,
162 (5), p. 995-1009 ISSN 0010-7999
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.
