Tephra Sampled from the Intraplate-Oceanic Island Volcano, Cumbre Vieja: The 2021 Eruption.

Comprehensive mineralogical and geochemical studies were conducted in application to a representative sample of tephra from Cumbre Vieja Volcano (the 2020–2021 eruption). The tephra has a gravel-psammitic grain-size distribution, and is characterized by an anomalously high degree of particle vesicularity. The whole-rock composition of this tephra is consistent with the transition from alkaline picrobasalts to alkaline basalts, while being essentially different from the tephra ashes discharged by marginal continental volcanoes. The tephra was studied to detect 45 trace elements with whole-rock compositions occasionally reaching 2333 g/t, above the respective figure for the tephra of island arc volcanoes. Judging by the relationship among geochemical criteria, the Cumbre Vieja tephra is consistent with the average parameter values for intraplate volcanoes in oceans. One geochemical feature of this tephra consists in a strong enrichment in lanthanoids, as well as in noble and platinoid metals. The lithogenic gas phase which was obtained by heating the tephra sample was found to contain H₂, CO, CO₂, H₂O, CH₄, C₂H₄, C₂H₆, C₃H₆, and С₃H₈. The proportions among inorganic components in the gas phase as a whole correspond to the boundary region between crustal and mantle–crustal derivates, but water is in relatively low amounts. Microlites were found to contain Fo_73–84 olivine; this contains dominantly diopside clinopyroxene, andesine–bytownite plagioclase, chrome-spinellids, phase-homogeneous solid solutions of ilmenite in magnetite, phases of Ni-Cu bearing native iron, quartz, and sodic hydroxyl-chlorides. In addition, the Cumbre Vieja tephra was found to contain dispersed scattered carbonaceous material with δ¹³С_PDB = –30...–24‰ as the isotopic composition of carbon, which is consistent with the isotopic composition of carbon in abiogenic carbonaceous materials of volcanogenic origin. The entire set of results of these mineralogical and geochemical studies characterizes Cumbre Vieja Volcano as a typical intraplate-oceanic plume volcano. [ABSTRACT FROM AUTHOR]