Extinct Volcanoes Could Harbor Valuable Rare Earth Deposits for a Promising Future

What if our energy future was based on our planet's past? More precisely, its volcanic past. That's what a team from theAustralian National University wanted to demonstrate in a study published on September 24, 2024 in the journal Geochemical Perspectives Letters. So, by making the most of the Earth's extinct volcanoes to extract rare earths, we could take another step towards an energy transition where fossil fuels would be ancient history.

What are rare earths?

In detail, these are chemical elements. There are 17 rare earths: Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium, Scandium and Yttrium.

Unless you have already studied physics and chemistry extensively, these names will mean absolutely nothing to you. Yet today, “They are omnipresent, especially in four industrial sectors that represent 10% of the global economy.” explains Vie-Publique.

These rare earths are an integral part of objects that we use every day. They are found in smartphones and screens, but also in the energy sector to manufacture wind turbines, electric or hybrid car engines, in the medical sector as well as in armaments.

Although these elements are present in considerable quantities on the planet, they are considered rare elements. And the reason for this lies in the difficulty of extracting and refining them, as Vie-Publique specifies. If China and the United States share the largest deposits of rare earths, France has some sites of interest, notably located in Brittany, Guyana and Polynesia.

However, it seems, according to a recent discovery, that deposits currently used for any other purpose would contain large quantities of rare earths. And for that, we must look in volcanoes.

Extinct volcanoes could be potential deposits.

Today, extinct volcanoes are formidable deposits of iron. Indeed, according to Michael Anenburg, co-author of the study in an article in The Conversation“There is an enigmatic magma that contains unusually high amounts of iron.“The latter would have come from the volcanic activity of the Earth which took place several million years ago. This is no longer the case today.

In this sense, extinct volcanoes are currently being exploited for their large quantity of iron. The scientist mentions in particular two major representatives of this exploitation: El Laco in Chile and Kiruna in Sweden.

However, when the Kiruna operators recently announced that this extinct volcano was, in addition to being an exceptional iron deposit, “Europe's largest rare earth resource“, this led scientists to explore a particular hypothesis. If Kiruna is a rare earth deposit, why not others?

Creating volcanism in the laboratory

To try to answer this question, which could be a major discovery regarding the exploitation of very important resources for the future of the energy transition, scientists therefore wanted to recreate a particular volcanic eruption.

In fact, it was not a school experiment or the one you do in the canteen with your mashed potatoes (even if sometimes, it is particularly successful). No, it was necessary for the team of researchers of theAustralian National University to recreate volcanic activity that had not occurred for several million years.

“We placed synthetic materials close to volcanic rocks and magmas in small capsules or “bottles” made of noble metals such as platinum. We then pressurized them to depths equivalent to 15 kilometers into the Earth’s crust and heated them to 1100°C, melting them into a liquid.” explains Michael Anenburg.

And the results are clear: when magma forms, it absorbs rare earths from the liquid obtained by melting volcanic rocks. But even more, the results of their study demonstrated that the absorption of rare earths by iron-rich magma, resulting from volcanic eruptions of several million years, was particularly effective.

In other words, extinct volcanoes of the same ilk as Kiruna, whose iron ore content is known, would surely all be impressive deposits of rare earths. Enough to hope for a simpler and larger-scale exploitation of these elements that have accumulated over several million years of volcanic activity.

Source : The Conversation