Modern technologies, such as those producing green energy from renewable resources like wind and water, require many tonnes of rare, so-called e-tech metals. Mining of e-tech metals can be costly, environmentally challenging and energy intensive. Most of the world’s high-value ‘heavy’ rare earths are found in ‘Ion Adsorption Deposits’ in Southern China, but so far no-one has identified precisely how the rare earths are hosted within these materials from China.
Anouk led the project which included group members Adrian Finch and Nicky Horsburgh as well as other members of the SoS RARE consortium team, particularly from the University of Brighton. The group used high energy synchrotron x-rays from the Diamond synchrotron source to identify the local surroundings around the rare earths, using the method of X-Ray Absorption Fine Structure (XAFS) modelling. Her work has now been published in the journal Nature Communications, 11, 4386
Using an intense synchrotron x-ray source, we reveal at the atomic scale where the rare earths are in the soil. Anouk found that the rare earths are loosely stuck to the surfaces of clay particles and was able further to refine precisely which clays and where on the crystal the majority of the rare earths were adhered. By comparing samples from a weathered volcanic complex in Madagascar to those mined in China, the study showed that they were mineralogically identical, providing key insights into how nature produces these easily-leachable, economically viable, rare earth deposits.
Anouk has been lead author of the study which answers the question of whether the Southern Chinese adsorption deposits are unique. Our study confirms that the Chinese soils are identical to deposits found in Madagascar, and that they formed in similar ways. The race is now on to find other deposits elsewhere in the world. This information will be an impetus to global exploration for critical metal resources outside China.
The paper has attracted a University Press Office and media attention for its impact on global heavy rare earth element production including a press release by the Diamond Synchrotron and phys.org. It was also the lead article in the Rare Earth Industries Association newsletter. Through the publication, we have also made contact with the research group of Professor Yushio Takahashi at the University of Japan who has been similarly using XAFS to study regoliths. Their results and interpretations on materials from Japan (Yamaguchi et al. (2018) Geochem. J, 52, 415-425) independently align with ours on materials from China and Madagascar. IAD deposits are likely to be more widely spread globally than previously thought.
Full Reference: Borst AM, Smith MP, Finch AA, Estrade G, Villanova-de-Benavent C, Nason P, Marquis E, Horsburgh NJ, Goodenough KM, Xu C, Kynický J & Geraki K (2020) Adsorption of Rare Earth Elements in Regolith-Hosted Clay Deposits, Nature Communications, 11, 4386.
Raw data from this study is deposited on the University of St Andrews data repository PURE.