Recurrent evacuation of mantle mush in ocean islands revealed by clinopyroxene from La Palma.

Temporal variations in magma plumbing influence eruption priming and the interpretation of unrest signals, yet remain poorly constrained in low-flux ocean island volcanoes. Here, we examine temporal changes in the active volcanic system beneath La Palma, Canary Islands, using clinopyroxene zoning from the 1712, 1971, and 2021 eruptions. Combining quantitative trace element mapping, thermobarometry, and cluster analysis, we show that preceding all eruptions, an evolved phonolitic crystal mush resided in the upper mantle (∼18-25 km depth) under relatively cool (1000-1025 °C) conditions. At least one week before eruption, basanitic recharge (1100-1150 °C) recycled this mush and promoted magma ascent, potentially with brief stalling in the crust (∼5-10 km). Mafic recharge was critical in unlocking the mush, yet may not represent the immediate eruption trigger. Globally, upper mantle evolved mushes may be common in ocean island basalt volcanoes, and their occurrence is likely controlled by the island evolutionary stage and magma flux.