Magmatic evolution and source variations at the Nifonea Ridge (New Hebrides Island Arc)

摘要: The Nifonea submarine volcano rises 1000 m above the seafloor of Vate Trough back-arc basin behind New Hebrides island arc. This large volcanic edifice has a caldera ∼8 km diameter and is connected to two ∼20 km long rift zones in basin. We present new chemical isotope data for glasses whole-rocks from both its zones. Lavas show an evolution towards more incompatible element enrichment, with most enriched lavas being youngest eruption products on floor. These are significant fractional crystallization, minor contamination by hydrothermal fluids (<0·3%) reflect mixing melts derived depleted upper mantle source similar those occurring North Fiji Basin. enrichment Nb these comparable that some arc (e.g. Mota Lava island), where coexist typical basalts. erupted along relatively elements, indicating melting addition sediment-derived fluid. Our observations suggest beneath heterogeneous small scale (<20 km) occurrence fertile portions stronger control processes than influx subducting slab, as all samples were recovered at distance trench.