Petrology and geochemistry of the 2014–2015 Holuhraun eruption, central Iceland

The 2014–2015 Holuhraun eruption in Iceland was one of the most closely monitored and sampled basaltic fissure eruptions to have ever taken place. In this paper lead by Sæmundur A. Halldórsson and many other scholars from Iceland and beyond we present a comprehensive collection of glass, mineral and whole-rock data. The geochemistry of the eruption products firmly locate it within the Bárðarbunga volcanic system. By carrying out careful geothermobarometry, we infer that the magma was stored at 8 ± 5 km prior to eruption, in excellent agreement with independent petrological, geophysical and geodetic observations (e.g., Hartley et al., 2018; Gudmundsson et al., 2016). Although the erupted magma is extremely homogeneous in composition, complexity in its crystal cargo reveals that the it was ultimately assembled from heterogeneous mantle melts that underwent crystallisation and mixing in the lower- to mid-crust.

Backscattered electron (BSE) image of a complexly zoned clinopyroxene from the 2014–2015 Holuhraun lava.

Publication

Halldórsson, S.A., Bali, E., Hartley, M.E., Neave, D.A., Peate, D.W., Gudfinnson, G., Bindeman, I., Whitehouse, M., et al. Petrology and geochemistry of the 2014–2015 Holuhraun eruption, central Iceland: Compositional and mineralogical characteristics, temporal variability and magma storage. Contributions to Mineralogy and Petrology,173:64.

Melt inclusion constraints on petrogenesis of the 2014–2015 Holuhraun eruption, Iceland

The 2014–2015 Holuhraun eruption in Iceland was the largest volume eruption on the island since the 1783–1784 Laki erution (e.g., Neave et al., 2013; 2017), and was one of the most closely monitored eruptions ever to have taken place (Gudmundsson et al., 2016). In this paper, lead by Margaret Hartley and Enikö Bali (who also recently published an associated paper), we present melt inclusion data from a suite of samples collected throughout the eruption.

Variability in melt inclusion compositions indicates that the erupted magma evolved from diverse primary melts by concurrent mixing and crystallisation. Using a refined method of olivine–plagioclase–augite–melt (OPAM) barometry, we place this evolution at mid-crustal depths, in agreement with geophysical indicators of magma storage. Re-equilibration of melt inclusion H2O contents indicates that crystals spent at least 1–12 days in their carrier liquid before eruption, consistent with lateral transport in a mid-crustal dyke from the Bárðarbunga central volcano to the eruption site.

A conceptual model for the entrapment of melt inclusions erupted during the 2014–2015 Holuhraun eruption. Figure from Hartley et al. (2018).

Publication

Hartley, M.E., Bali, E., Maclennan, J., Neave, D.A. & Halldórsson, S.A. 2018. Melt inclusion constraints on petrogenesis of the 2014–2015 Holuhraun eruption, Iceland. Contributions to Mineralogy and Petrology, 173: 10. <Open Access>