The noble gas and carbon isotopic signature of the 2021 Tajogaite eruption (La Palma, Canary Islands)

• ANDRÉS SANDOVAL-VELÁSQUEZ ^[1] ; ANDREA L. RIZZO ; FEDERICO CASETTA ; TEO NTAFLOS ; ALESSANDRO AIUPPA ; MAR ALONSO ; ELEAZAR PADRÓN ; MATTHEW PANKHURST ; ANDREA MUNDL-PETERMEIER ; VITTORIO ZANON ; MASSIMO COLTORTI ; MARIA LUCE FREZZOTTI ; NEMESIO M. PÉREZ
  1. [1] University of Palermo

     University of Palermo

     Palermo, Italia

     
• Localización: Cosmológica, ISSN 2792-7423, Nº. Extra 1 (Conferencia Internacional: Erupción del Tajogaite (Los Llanos de Aridane, noviembre de 2025)), 2025, págs. 277-279
• Idioma: inglés
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  • The 2021 Tajogaite eruption on La Palma provided a unique opportunity to investigate the temporal evolution of magmatic volatiles and mantle source characteristics beneath the Canary Islands. We analyzed the elemental (He-Ar-CO2- N2) and isotopic (He-Ar-Ne) compositions of fluid inclusions (FI) in olivine and clinopyroxene phenocrysts from Tajogaite lavas, tracking significant temporal changes during the eruption (Fig. 1). From mid-October, we observed increasing He-CO2-N‚ concentrations in FI, paralleled by elevated 40Ar/36Ar ratios (>500) and a shift in lava composition toward more primitive signatures, including higher Mg# (up to 59), elevated CaO/Al2O3, and increased Ni and Cr contents.

    These geochemical changes indicate a growing contribution of deeper, less-degassed magma sourced from the mantle (15-30 km), corroborated by mineral thermobarometry and FI barometry. Despite these compositional shifts, 3He/4He ratios (Rc/Ra) remained constant throughout the eruption at MORB-like values (7.38 ± 0.22 Ra), suggesting an isotopically homogeneous magma source. The He isotopic signature aligns with those from the 1677 San Antonio eruption (7.37 ± 0.17 Ra) but is more radiogenic than the >9 Rc/Ra values recorded in the Caldera de Taburiente. Modeling indicates that the He isotope composition reflects three-component mixing among MORB-like mantle, a radiogenic source, and a minor high-3He/4He (>9 Ra) endmember. The simultaneous presence of both MORB-like and high-3He/4He signatures across La Palma points to small-scale mantle heterogeneities. To further characterize carbon behavior, we analyzed δ13C values and CO2/3He ratios in FI from Tajogaite and San Antonio lavas, and ultramafic xenoliths. δ13C values ranged from -4.94 ‰ to -2.71 ‰ with CO2/3He ratios of 3.37-6.14 × 109. Comparable isotopic signatures in xenoliths and previous data from the Taburiente Caldera suggest island-wide carbon isotope homogeneity...