Abstract:

Deep magmatic processes occurring at the crust-mantle boundary (or “Moho”) are generally geochemically studied using either materials brought up by magmas in past eruptions or by investigation of fossil ophiolite sequences. Although powerful, these approaches do not offer precise constraints on the rates of magmatic processes. The recent eruptions of Fagradalsfjall provide, for the first time, a third way to geochemically study these deep processes using high-frequency sampling of a volcanic eruption sourced from the near-Moho. Geochemical investigation of the Fagradalsfjall eruption products reveals magmatic processes on day-to-weeks timescales and interaction between multiple near-Moho magma bodies. Using the geochemical results as a basis, it is possible to construct a tentative model for events occurring in the Fagradalsfjall magma plumbing system during the 2021 eruption.

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