Abstract

Rare earth elements (REE) are indispensable to infrastructure, technology, and modern lifestyles, which has led to an increasing demand for these elements. The current global rare earth oxides (REO) market is dominated by Chinese production, which peaked in 2006 at 133,000 tonnes REO per year, accounting for some 97.1% of global production, causing concern about the long-term supply of REE resources. Although the REE consist of 17 individual elements (15 lanthanides plus scandium and yttrium) that are hosted by numerous types of mineralization, the relatively modest scale of the global REE mining sector has limited our knowledge of REE mineral resources and mineralizing systems compared to metals such as copper and iron, which are produced in much larger quantities.

In order to quantitatively analyze the mineralogy, concentrations, and geologic types of REE deposits, we compiled a global dataset of REE mineral resources based on the most recently available data (2013–2014). This compilation yields minimum global contained total rare earth oxides plus yttrium oxide (TREO + Y) resources of 619.5 Mt split between 267 deposits. Deposits with available grade and tonnage data (260 of the 267 deposits in our database) contain some 88,483 Mt of mineral resources at an average concentration of 0.63% TREO + Y, hosting 553.7 Mt TREO + Y. Of the 267 total deposits in our database, some 160 have mineral resources reported using statutory mining codes (e.g., JORC, NI43-101, SAMREC), with the remaining 107 projects having CRIRSCO-noncompliant mineral resources that are based on information available in the industry literature and peer-reviewed scientific articles.

Approximately 51.4% of global REO resources are hosted by carbonatite deposits, and bastnäsite, monazite, and xenotime are the three most significant REE minerals, accounting for >90% of the total resources within our database. In terms of REE resources by individual country, China dominates currently known TREO + Y resources (268.1 Mt), accounting for 43% of the global REO resources within our database, with Australia, Russia, Canada, and Brazil having 64.5, 62.3, 48.3, and 47.1 Mt of contained TREO + Y resources, respectively. Some 84.3 Mt TREO + Y is hosted within tailings (dominated by tailings from Bayan Obo but with smaller resources at Palabora, Steenkampskraal, and Mary Kathleen) and 12.4 Mt TREO + Y is hosted by monazite within heavy mineral sands projects, illustrating the potential for REO production from resources other than traditional hard-rock mining.

Global REE resources are dominated by the light REE, having an average light REO (LREO; La-Gd) to heavy REO (Tb-Lu and Y) ratio of 13:1. These REE deposits contain an average of 81 ppm Th and 127 ppm U, indicating that radioactive waste associated with REE extraction and refining could be a concern. Modeling the 2012 global production figures of 110 kt TREO + Y combined with an assumed 5% annual growth in REE demand indicates that known REE resources could sustain production until 2100 and that geologic scarcity is not an immediate problem. This suggests that other issues such as environmental, economic, and social factors will strongly influence the development of REE resources.

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