What if the secret to cracking the world’s rare earth chokehold lay in the peaceful interiors of dead volcanoes? In a bombshell that upends conventional wisdom, laboratory simulations have shown that iron-rich magmas formerly flowing through long-dead volcanoes can capture rare earth elements as much as 200 times more efficiently than normal magmas. This discovery, which Michael Anenburg of the Australian National University has called “potentially opening a new avenue for rare earth extraction,” could revolutionize geological exploration and the worldwide supply chain for clean technology.
Rare earths like lanthanum, neodymium, and terbium are crucial to the permanent magnets used in electric vehicles, wind turbines, and other digital and defense technologies. While they have deceptive names, these do not pose a shortage issue in and of themselves; the problem lies in their availability in quantities sufficient to make economic extraction possible. The world is still extremely reliant on China, which provides over 60% of REE production and 85% of processing, and whose supply chains can be shocked by geopolitics and are subject to export controls.
The study began with the discovery of a massive REE deposit in the Kiruna district, Sweden, with an unexpected concentration of rare earths in a gargantuan body of iron ore produced by volcanic activity 1.6 billion years ago. In order to determine the origin of the enrichment, researchers at ANU and the University of the Chinese Academy of Sciences modeled conditions in these ancient volcanoes. They melted synthetic rocks in a pressure furnace, mimicking the mysterious iron-enriched magmas that were believed to have erupted from extinct volcanoes in the past. The outcome was breathtaking: the iron-enriched magma absorbed all the rare earth elements from its surrounding environment, with efficiencies that were as much as 200 times larger than those of normal magmas, the research said.
Geochemical experiments have clarified the processes involved in partitioning. Iron oxide-apatite deposits, produced by the immiscible segregation of silicate and iron phosphate melts under conditions of volcanic pressure and temperature, are natural concentrators of REE. Shengchao Yan, who is at the Chinese Academy of Sciences and lead researcher on the study, stated that “the concentrations of the rare earth elements can be up to 200 times larger than in the silicate melts.” The light REEs, including lanthanum, are particularly enriched in FeP melt, with heavy REEs including lutetium being highly enriched but less than the light REEs. It is geochemical selectivity critical to successful targeting of the appropriate deposits and optimizing the extraction processes in IOA-rich regions.
The diversification of the supply chain and mining consequences are extreme. In some of the world’s largest iron-ore mines those in the United States, Chile, and Australia beneath each of them rests one of these now-extinct, iron-enriched volcanoes. “Those mines are mining iron oxide. They’re mining magnetite. They never looked [to see] if they even have any rare earth elements.” They didn’t even bother [to look] to see if they even contain any rare earth elements in them, Anenberg said. By backsliding and looking again at their current iron-ore mines for REE potential, companies can bring more value out with little new environmental impact. “It’s a win-win,” Anenberg said. “The company gets more value out of the stuff they’re mining anyway. And then the environment wins, because we don’t need to put a new hole in the ground.”
Nonetheless, the guarantee of novel sources does not eliminate the industry’s paralyzing environmental and social problems. Conventional REE mining has been marred by the utilization of toxic chemicals, radioactive byproducts, and allegations human rights abuses in supply chains. Extraction methods like pyrometallurgy and hydrometallurgy are energy- and pollution-intensive, and recycling as hopeful as it looks is on the sidelines due to technical and economic limitations. Options that are less environmentally demanding are in the newer advances in bioleaching and biosorption, which employ microorganisms to extract REEs from waste streams. Application of Acidithiobacillus thiooxidans in bioleaching, for example, has the potential to reclaim neodymium and praseodymium from electronic waste at recovery rates over 50%, and such procedures are also being tested for mining tailings and phosphogypsum to reduce ecological footprint.
The message to the mining engineers and geoscientists is clear: iron-rich extinct volcanoes that are already defined and mined on a regular basis for iron are the potential future source of rare earth supply. Geochemical modeling, remote sensing, and focus sampling are now the unlocking keys to these previously untapped resources. “They start from the laboratory and then try to mimic a natural environment, to understand how these rare earths could actually accumulate in a small place in the entire crust,” Vrije Universiteit Amsterdam’s Lingli Zhou explained.
As the world demand for REEs is estimated to rise fivefold by 2030, the race is on to find, mine, and refine the elements economically as well as environmentally. The quiet volcanoes of yesteryear might yet energize the technologies of tomorrow.
