New Tools to Unearth Rare Earth Metals

The study, led by a team from the University of St. Andrews' School of Earth and Environmental Sciences and published in the journal Geology, sheds new light on how hot volcanic fluids concentrate rare earth metals and how these metals leach out of magma bodies.

These rare metals, including elements such as niobium and tantalum, are essential for the production of alloys, batteries, magnets, and superconductors, and are vital to modern technologies from cell phones and laptops to MRI machines. These metals are also essential for green technologies, and the transition to a low-carbon economy must involve finding new sources of rare earth metals.

Rare earth deposits are associated with alkaline volcanoes. These volcanoes are unusual and are only exposed in specific areas around the world, such as southern Greenland.

A team of researchers from the University of St. Andrews wanted to understand why some volcanoes produce large deposits of metals, while others do not mineralize. By studying a metal-poor volcano in Greenland, the researchers were able to show that fluids that leak from the magma body into the surrounding rock can carry large amounts of rare earth metals. Rather than concentrating the metals, these fluids spread them over large areas, greatly reducing the chances of forming economically viable deposits.

“By measuring the chemical composition of the rocks surrounding the magma chamber, we show that metals have been carried out of the chamber and into the surrounding rocks," said Krzysztof Sokół, principal investigator at the School of Earth and Environmental Sciences. “This is the first estimate of the mass of material transported through this process. We also present a new method to visualize the distribution of metals in the surrounding rocks."

"Our research shows that during volcanic activity, melt at shallow depths of the Earth's crust can form separate hot fluids rich in key metals that subsequently leak from magma chambers into surrounding rocks, carrying large amounts of metals across the globe."

The team estimates that the total tonnage of key metals transported into the surrounding rocks by this process is about 40 megatons, which is comparable to the mass of rare earth metals present in some of the world's largest metalliferous deposits.

Prof. Adrian Finch and Dr. Will Hutchison, also from the St. Andrews School of Earth and Environmental Sciences, added, "Fluids can 'leak' out of magma systems that would otherwise crystallize within the magma chamber to form large critical metal deposits. Now that we understand this process more fully, we can more effectively predict how deposits under these types of volcanoes are formed. Armed with this information, we can provide better guidance for the next generation of green technology exploration."

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