Historical eruptions of lanzarote, canary islandsinference of magma source and melt generation from olivine and its melt inclusions

Résumé

The study of oceanic island basalts (OIB) reveals the complexity of the mantle, which compositionis highly variable. Deciphering the source lithologies and processes involved in the OIB formation ischallenging since the magmas are transformed on their way to the surface.This is especially criticalat Canary Islands where the lithosphere is thought to be remarkably thick (>110 km Fullea et al.,2015). In order to better constrain the composition of primitive magmas and the plausible mantlelithologies involved, two historical eruptions recorded at Lanzarote island, Timanfaya 1730-1736 and1824 eruptions have been investigated. Indeed, these two eruptions offer a unique opportunity toinvestigate the mechanisms of magma generation and composition in the context of mantle heterogeneity.The Timanfaya, 1730-1736 historical eruption emitted magmas that evolved from basanites throughalkali basalts, finally reaching tholeiitic compositions at the end of the eruption. In 1824 the last eruptionon the island produced extremely volatile-rich basanite. The heterogeneity of the mantle is demonstratedto the extreme in Lanzarote where a single eruption exhibit compositional variations similar to the span ofthe OIB worldwide. The extreme heterogeneity is systematic from whole rock lava and tephra at eruptionscale but amplified at mineral and melt inclusion scale within a single tephra sample of the eruption...