Towards a process-based understanding of rare-earth element deposits

This research relates to a set of 17 elements called the rare-earth elements (REEs), which form an essential component of the high-tech devices on which modern society depends. Perhaps most importantly, REEs are integral to emerging green technologies such as wind turbines, batteries and photovoltaic cells; technologies that will be crucial in addressing the climate crisis, since the energy sector is the largest single contributor to human greenhouse gas emissions. Our reliance on electronics and the development of renewable energy sources is driving rapid increases in the demand for REEs. However, global production is restricted to relatively few REE deposits, with 90% originating in China. Consequently, there are significant concerns over both the capacity to respond to increased REE demand, and the security of access to these vital resources. Finding new and diverse sources of REEs is therefore essential to maintain our way of life and facilitate our transition to a low-carbon future. The most important sources of REEs are within 'carbonatite' and 'alkaline' igneous rocks. These rocks form deep in the Earth as magmas, which then ascend and solidify at shallower depths, concentrating REEs that eventually become exposed on the Earth's surface. However, the exact formation processes that lead to their enrichment in REEs are poorly understood, and their small size on the surface makes them extremely hard to find. This project will increase our understanding of these rocks, and develop a novel tool to efficiently locate future REE deposits associated with these rock types, using a three-step process. The first step in my research project will develop a computational tool to model how carbonatite and alkaline igneous rocks form. This tool can be used to improve our understanding of, and predict the distribution of, these REE-bearing igneous rocks on Earth. The second step of my research will lay the foundations for locating REE deposits, by analysing the characteristic 'patterns' that their formation leaves on the surrounding geology. When carbonatite and alkaline rocks solidify at shallower depths they alter the surrounding 'country rock', creating alteration zones termed 'fenites'. These fenites have complex structures and textures and are not well understood. By developing a robust understanding of fenites, we can use them as 'signposts' for elusive REE deposits, as the fenite zones are larger and easier to find than the REE-bearing igneous rocks that create them. To accomplish this, I will conduct a detailed study of two well-known fenite zones that exhibit varying structures and textures. By combining structural and chemical observations with my computational models, I will build a holistic understanding of their formation and REE enrichment. This new understanding of the emplacement of REE-bearing igneous rocks and the formation of fenites will enable the final stage of my project: developing new ways of finding REE deposits using remote sensing (airborne) techniques. These techniques, which I will develop alongside industrial partners, will search for fenite zones as signposts for the REE deposits that are associated with them. This methodology is likely to be particularly beneficial in locating REE deposits in hitherto poorly explored, but emerging frontiers, such as the Arctic and East Africa.