Sunda arc mantle source δ18O value revealed by intracrystal isotope analysis

The hidden depths of volcanic eruptions

26 November 2021

Conditions deep beneath volcanoes can be analysed by measuring oxygen isotope ratios within individual crystals of erupted magma.

Volcanic eruptions give ready access to magma that originated in Earth’s mantle. However, magma stored in the crust prior to an eruption can undergo mixing with crustal rocks, altering its chemical composition and obscuring information about the mantle itself.

Now, a team that included University of Cape Town researchers has shown that oxygen isotope ratios in magma samples are not significantly altered by local subduction processes.

They used samples of magma from a string of volcanoes in Indonesia called the Sunda Arc, generated by the subduction of the Indo-Australian plate beneath the Eurasian plate. The team disentangled the crustal contribution to magma composition using a high-precision technique called secondary ion mass spectrometry (SIMS) to measure atomic ratios at sub-10 micrometre-sized sites within individual magma crystals.

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References

1. Nature Communications 12, 3930 (2021). doi: 10.1038/s41467-021-24143-3