Mantle source characteristics and magmatic processes during the 2021 La Palma eruption

The 2021 eruption of La Palma (September 19-December 13) was the first subaerial in Canary Islands 50 years. Approximately 0.2 km3 lava erupted from a newly formed, broadly basaltic composite volcanic edifice on northwestern flank Cumbre Vieja ridge. Comprehensive sampling olivine- and clinopyroxene-phyric lavas over period reveals temporal changes mineralogy bulk rock geochemistry tephrite to basanite. Initial have low MgO (?6 wt.%) elevated TiO2 (?4 contain amphibole crystals gabbroic micro-xenoliths. In contrast, with progressively more mafic compositions approximately day 20 thereafter remained as basanite (?8 wt.% MgO; 3.7 TiO2) until termination. Temporal chemistry reflect initial fractionated magmas that crystallized 5-10% olivine clinopyroxene, well minor spinel, sulfide, magnetite, followed by later deeper-sourced primitive magma. Vanadium-in-olivine oxybarometry indicates parental were oxidized (fO2 = +1.5 +2 FMQ) 8.2 ±0.8 generated between 2.5-3% partial melting mantle source potentially containing pyroxenite component (Xpx 0.31 ±0.12). Day 1-20 tephrites radiogenic 187Os/188Os (0.143-0.148) lower Pd, Pt, Ir Os contents than post basanites (187Os/188Os 0.141-0.145). Combined available seismic data, provide high-resolution record eruptive evolution. magma stored upper lithosphere up four years prior eruption, consistent pre-cursor seismicity presence partially reacted fed basanitic likely sourced deeper portion storage system is underplating island. Precursor events involved emplacement, differentiation, which mobilisation, eventual exhaustion melts. This magmatic progression similar documented 1949 1971 eruptions. Ocean islands limited supply show similarities evolution observed large silicic systems, where emplacement differentiation remobilisation induces activity.