Deep mafic recharge priming ocean island basalt volcanoes: clinopyroxene evidence from La Palma, Canary Islands

Temporal variations in magma plumbing architecture and magmatic processes can modulate eruption priming, with direct implications for the interpretation of pre- and syn-eruptive signals. However, the mechanisms in which these processes operate in low-flux volcanoes remains poorly constrained, limiting our understanding of eruption precursors. Here we investigate the temporal evolution of magmatic processes at La Palma (Canary Islands), a low-flux ocean-island basaltic system, by examining clinopyroxene zoning from three historical eruptions that record a transition from tephritic to basanitic lava compositions: El Charco 1712, Teneguía 1971, and Tajogaite 2021. By integrating major and trace element data from clinopyroxene crystals and carrier melts with textural observations, thermobarometry, quantitative trace element mapping, and cluster analysis, we reconstruct the magmatic processes and storage conditions preceding these eruptions. Both tephritic and basanitic magmas were stored in the upper mantle (18–25 km depth) together with an evolved tephritic-to-phonolitic crystal mush, preserved in clinopyroxene antecryst cores. This phonolitic mush was stored at lower temperatures and likely formed through >80% fractional crystallization of a basanitic melt. Prior to each eruption, repeated injections of basanitic recharge melts progressively eroded and remobilized the mush, after which the recharge magma experienced ~10–20% fractional crystallization, generating the tephritic melt. Despite its central role in priming the system, mafic recharge did not act as the immediate trigger for the historical La Palma eruptions. The lack of recharge-related signatures in inner rims of early-erupted tephrite-hosted clinopyroxenes shows that eruption onset was likely controlled by internal reservoir processes rather than by mafic recharge events.