Mantle and Crustal Xenoliths in a Tephriphonolite From La Palma (Canary Islands): Implications for Phonolite Formation at Oceanic Island Volcanoes

The occurrence of mantle-derived peridotite xenoliths in phonolitic melts is a rare phenomenon, and commonly ascribed to mantle origin the phonolite. alternative possibility, that are transported into evolving phonolite by mafic magmas, has received little attention. A unique tephriphonolite lava with groundmass composition, from active Cumbre Vieja volcano La Palma (Canary Islands), allows test these models. contains abundant inclusions represent island’s major xenolith types: kaersutite-dominated cumulates, gabbros lower oceanic crust, peridotites mantle. Our petrological investigations indicate magma contained 3–4 wt% H 2 O was stored crust at around 250–350 MPa 900–950°C, oxidized conditions (?NNO 2–3). mantled complex polyphase selvages, adjacent up 1.6 mm wide zonations where olivine compositions change Fo 78-86 selvage contact 89-91 inside xenoliths. We carried out diffusion modelling for Fe-Mg exchange found had intermediate evolved alkaline over decades centuries. This timescale comparable inferred basanite-hosted Vieja. following model proposed: differentiation occurs accumulation zone lowermost beneath Palma. receive periodic recharge magmas intervals on order few centuries, historic eruption recurrences (80 years average). Some pulses carry fragments become deposited zone. Thus, do not reflect formation Final ascent triggered some weeks before its eruption, resulting entrainment thorough mingling mixed population (cumulates, gabbros, peridotites). infer phonolites island volcanoes, subsequent requires balance between rates volumes eruptive events.