REE Exploration

Exploration

Exploration for REE experienced a boom, which started in 2010, after China placed export restrictions on their supply of REE to the rest of the world. This boom has developed over the past decade, further fuelled by increased prices and increased demand for certain REE.

Exploration for REE occurs on every continent on Earth with the exception of Antarctica. Some of the projects and target areas are at the very early stages of exploration, whilst others are more progressed having published resource and reserve estimates.

Global map of REE mines, deposits and occurrences, with approximate locations indicated. source: Deady (2021).

Deposits, occurrences and mines that contain REE are known across the globe. They occur in a range of deposit types in a variety of geological settings, the most important deposits are associated with carbonatites, ion adsorption clays and alkaline igneous rocks. Carbonatites are igneous rocks that contain more than 50% modal carbonate and are typically enriched in the LREE. Ion adsorption clays typically occur as tropical weathering crusts on top of igneous lithologies such as alkaline granites. During weathering the REE are released from primary igneous minerals and are then adsorbed or bonded to secondary clays, creating an easily processed REE-rich deposit. The REE content of ion adsorption clay deposits can be variable but currently most of the world's HREE are extracted from these deposit types. Alkaline igneous rocks can be important hosts for REE mineralisation, for example REE are extracted from a large igneous complex in northern Russia. Other deposits associated with igneous rocks, that contain the mineral eudialyte, could be a potential future source of REE if appropriate processing technologies are developed. REE are also sourced from mineral sands and placers across the globe. Monazite and xenotime are the main minerals produced from these particular deposit types.

Reserves of Contained

Rare earth oxides (REO)

Publicly available data released by exploration and mining companies, and published historic data indicate that there are significant global resources and in some cases reserves of REE. These data have been converted to contained rare earth oxides (REO) to make them comparable. However, due to the lack of available data for the majority of known deposits and operating mines in China it's difficult to make a true comparison, with China having some of the most significant resources and reserves in the world. Some deposits will have a higher grade of (heavy) HREE or (light) LREE, depending on the geology of the deposit, but this is, in the majority of cases, indistinguishable from the available public data.

Global distribution of rare earth element reserves expressed as tonnes of REO (rare earth oxides). Diagram shows global distribution of reserves, with RoW (rest of world) comprising countries with resources of less than 2 Mt, including Canada, South Africa, Tanzania and Greenland. Data source: USGS (2023).

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