Magmas from multiple mantle sources outcrop at a volcano in Iceland

June 29. () –

The Fagradalsfjall eruption in Iceland provided a unique opportunity to study magmas accumulated in a crustal reservoir but originating in the mantle. more than 20 km. deep.

A research team from the University of Oregon, Uppsala University, the University of Iceland, and Deutsches GeoForschungsZentrum (GFZ) took advantage of this exceptional recent eruption to collect lava samples every few days to build a time-integrated sample catalog. and to monitor the geochemical evolution of the eruption with a degree of detail rarely achieved before.

Typically, when volcano scientists look at past eruptions, they work with a limited view of the erupted materials; for example, older lava flows may be completely or partially buried by newer ones. However, at Fagradalsfjall, the eruption was monitored and sampled so well that scientists they had the opportunity to capture the evolution of an Icelandic eruption in near real time.

The team was interested in isotopes of oxygen. Why? Because oxygen makes up about 50% of all volcanic rocks and its isotopic ratios are very sensitive tracers of mantle and crustal materials. In this way, oxygen isotopes can help scientists determine whether the magma was derived from the mantle or interacted with crustal materials as it moved toward the surface.

In addition to oxygen, however, the other broad set of elements that make up volcanic rocks yielded some surprises. For example, the team noted that this single eruption contains about half of all the diversity from magmas derived from the mantle previously registered for all of Iceland.

In summary, the geochemical results show that Iceland’s last eruption was supplied by magmas derived from multiple sources in the Earth’s mantle, each with its own distinctive elemental characteristics. To the astonishment of scientists, each of these domains had identical ratios of oxygen isotopes.

This result was remarkable and had never before been observed in an active eruption. The study provides compelling new evidence for distinct mantle-derived magmas that have uniform oxygen isotope ratios, which may help us better understand mantle dynamics and refine mantle models for Iceland.

The research was published in Nature Communications.