A new theory to explain some of the geochemistry of “hotspots”

A geochemical journey from the center of the Earth.


Hotspots are plumes of magma that come from deep inside the Earth and erupt at the surface. They are believed to help in the formation of large volcanic islands such as Hawaii and Iceland. These hotspots are popular with geochemical travelers as well.

According to a new study from Yale University, natural processes have carried quantifiable geochemical signals throughout Earth’s history from the metallic core’s deep interior to its thick middle layer and all the way to the surface, where they have been identified as magma “hotspots.”

Amy Ferrick, the lead author of a new study, said, “Magma hotspots are home to some of the most unique geochemistry found on the Earth’s surface.”

“Where hotspots come from, and what makes magma hotspots so unique is not fully understood, but studying their geochemistry can give us clues.”

The tungsten and helium isotopes that are detected in the crystallised magmas near these hotspots are one of those hints.

Isotopes are two or more different kinds of atoms with the same atomic number but different neutron counts.

The ratios of tungsten and helium isotopes at magma hotspots differ from those in the mantle, the planet’s rocky middle layer.

Instead, the ratios align with isotopes discovered much deeper, at the planet’s metallic, tungsten-rich core.

Ferrick and Jun Korenaga, a professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences, noted, “Earth’s mantle convection processes are so vigorous — and were particularly so during Earth’s early years, when it was hotter and partially molten — that it is highly unlikely helium could be trapped in reservoirs originating in the mantle.”

For this study, scientists have developed a computer model that shows how the tungsten and helium isotopes could make the journey from the center of the Earth.

They claim that isotope diffusion, which is the movement of atoms dependent on temperature and the size of the particles being moved, can produce a hotspot highway.

Korenaga said, “I initially thought that diffusion might be too slow to be effective, so I was surprised when Amy showed that this process was more than sufficient to explain the anomalous tungsten and helium compositions of ocean island basalts.”

“The research has far-reaching implications for understanding early Earth conditions such as the extent of magma oceans. It also may help scientists understand the evolution of areas in Earth’s interior that have been hidden from view for billions of years.”

Journal Reference

  1. A. Ferrick and J. Korenaga. Long-term core–mantle interaction explains W-He isotope heterogeneities. PNAS, Jan 17, 2023. DOI: 10.1073/pnas.2215903120
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