The 2021 Fagradalsfjall eruption, the first on the Reykjanes Peninsula in 781 years, provides a unique opportunity to study Iceland's mantle composition, particularly its oxygen isotope composition (δ¹⁸O). Basalts from the eruption show compositional variations in Zr/Y, Nb/Zr, and Nb/Y, indicating involvement of Icelandic plume (OIB) and Enriched Mid-Ocean Ridge Basalt (EMORB) components. However, δ¹⁸O values are remarkably invariant (mean 5.4 ± 0.3‰), indistinguishable from "normal" upper mantle, unlike significantly lower δ¹⁸O values found elsewhere in Iceland. This suggests that despite differing trace element characteristics, the melts show no evidence for ¹⁸O-depleted mantle or interaction with low-δ¹⁸O crust, providing a useful mantle reference value for this region.

I. N. Bindeman, F. M. Deegan, V. R. Troll, T. Thordarson, Á. Höskuldsson, W. M. Moreland, E. U. Zorn, A. V. Shevchenko, T. R. Walter