Date of this Version
Andersen, D. (2023). Modeled uranium series disequilibria in a heterogeneous mantle underlying Iceland. Undergraduate Honors Thesis. University of Nebraska-Lincoln.
Regional lithologic heterogeneities in Earth’s mantle may significantly contribute to variations in magma productivity and crustal generation. Such heterogeneities may be a key factor in the anomalously high rates of magmatism and thickened crust of Iceland, which are not fully explained by the presence of a mantle plume. However, the exact lithologic composition of the mantle underlying Iceland is largely unknown. Recent trace element modeling has suggested a two-component melt source beneath Iceland, consisting of a typical upper mantle peridotite mixing with one of several compositions of pyroxenitic material. This study further investigates these potential melt sources by calculating U-series disequilibria in partial melts of these compositions and comparing these results to measured geochemical data from Icelandic basalts, including a new measurement from the 2021 eruption of Fagradalsfjall. This study found that high proportions of hybridized pyroxenitic material, when mixed with peridotite, replicate Icelandic lava geochemistry reasonably well. These results suggest Iceland is underlain by upwelling peridotitic mantle with entrained pockets or veins of hybridized pyroxenite, perhaps drawn upwards by the Iceland mantle plume.