The recent eruption of Fagradalsfjall in southwest Iceland captivated the world, including nature lovers and scientists. The eruption was particularly significant because it provided geologists with a unique opportunity to study magmas accumulated in a deep crustal magma reservoir but ultimately derived from the Earth’s mantle (below 20 km).
A research team from the University of Oregon, Uppsala University, University of Iceland, and Deutsches GeoForschungsZentrum (GFZ) took advantage of this unique opportunity to collect lava samples every few days in order to build a catalog of samples integrated over time and to monitor the geochemical evolution throughout the period. the eruption to a degree of detail rarely achieved before. Usually, when volcano scientists examine past eruptions, they work with a limited view of the erupting materials – for example, older lava flows may be fully or partially buried by newer ones. However, at Fagradalsfjall, the eruption was so well monitored and sampled that scientists were lucky enough to capture the progress of an Icelandic eruption in near real time.
The team focused on oxygen isotopes. Why? Because oxygen makes up about 50% of all volcanic rocks and its isotope ratios are very sensitive tracers of mantle and crustal materials. In this way, oxygen isotopes can help scientists determine whether magma is derived from the mantle or has interacted with materials in the crust on its way to the surface. However, in addition to oxygen, the other vast suite of elements that make up volcanic rocks held some surprises. For example, the team observed that this single eruption contains about half of the total diversity of mantle-derived magmas previously recorded for all of Iceland.
In short, the geochemical results show that the last Icelandic eruption was fueled by magmas from multiple sources in the Earth’s mantle, each with its own distinctive elemental characteristics. To the amazement of scientists, each of these domains had identical oxygen isotope ratios. This result was remarkable and had never been observed before during an active eruption. The study provides compelling new evidence for distinct mantle-derived magmas having uniform oxygen isotope ratios, which may help us better understand mantle dynamics and refine mantle models for Iceland.
The research has been published in Nature Communication.
The research team discovers that some magmas come from portions of the mantle containing remnants of the Earth’s oldest crust
IN Bindeman et al, Various mantle components with invariant oxygen isotopes during the 2021 Fagradalsfjall eruption, Iceland, Nature Communication (2022). DOI: 10.1038/s41467-022-31348-7
Provided by Uppsala University
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