Rare Earth Element Deposits: Sources, and Exploration Strategies

Abstract

Rare earth elements (REE) include the lanthanide series (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) plus Sc and Y. All these metals occur together in different types of REE deposits such as carbonatites, alkali syenites and monazite-rich placers, and are found in more than 250 minerals in the Earth’s crust. The future of the world’s green technologies depends upon their availability and supply. At present, China is responsible for 80% of global REE production. However, countries such as USA, Australia, India, and Kazakhstan also extract and refine significant quantities of REE. These metals occur in primary deposits associated with igneous and hydrothermal processes, and secondary deposits concentrated by sedimentary processes and weathering. However, other types of resources such as ocean bottom sediments, waste rocks in closed mines, river sediments, industrial wastes like red mud, coal, and fly ash have proved to be containing significant amounts of these elements. Besides the beach sand deposits, the Amba Dongar carbonatite complex, and carbonatite plugs hosting REE deposits at Kamthai have been recognized as a potential REE resource in India. Significant concentrations of REE were identified in the deep-sea sediments of Afanasy Niktin Seamount in the Indian Ocean. Integrated exploration methods are playing a key role in the search for new REE mineral deposits. During geochemical exploration studies, portable analytical instruments such as pXRF, pLIBS, portable Raman spectrometer, and a couple of nuclear techniques have enabled successful results in recent times both on and off the land at lower costs, and allowing rapid decision-making on exploration strategies directly in the field.

Potential Future Alternative Resources for Rare Earth Elements: Opportunities and Challenges

“…REE deposits are divided into primary (formed by magmatic, hydrothermal and/or metamorphic processes) and secondary deposits (formed by weathering and sedimentary transport) depending on their form of occurrence, genetic associations, and mineralogy [12]. Figure 1 Illustrative view of different types of REE resources including the potential alternate future resources [13] ,…”

“…Primary deposits of REE are commonly associated with carbonatites and alkaline igneous rocks, pegmatites, iron oxide copper-gold deposits, and vein and skarn deposits. Of these carbonatites and peralkaline silicate rocks with appreciable concentrations of REE are the most important REE resources [13,14]. These REE deposits in igneous rocks have played an important role in meeting the industrial demand for decades.…”

Development of a simple and efficient two-step microwave-assisted digestion method for the determination of REEs, HFSEs and other elements in granite samples by ICP-OES

“…The demand for REEs as well as Y and Sc is drastically increasing worldwide because of their extensive utilization in a wide range of high technology applications in various strategic sectors such as defence, atomic energy, space, oil, electronics, etc. 1–5 REEs are also increasingly important in low-carbon emission applications which include hybrid/electric vehicles, wind energy generators for electrical energy production and alloying additions in steel making. 6,7 According to the 2023 reports, India is the world's sixth-largest producer of rare earths with an estimated production of 2900 metric tons of rare earth oxide equivalent.…”

Mineralogy and Geochemistry of some Phosphate Deposits for Possible Rare Earth Elements Mineralization Potentials within Sokoto Basin, Northwestern Nigeria

“…All these sources are being explored in the production of REEs globally, with China being the world's largest producer accounting for about 62%, followed by the United States (12.2%), Myanmar (10.3%), Australia (9.9%), India (1.4%) and other countries (4.2%),. The increasing demand for REEs has led researchers into more exploration works on alternative sources to Carbonatites, with phosphates being one of such (3) .The Nigerian Phosphate deposits are dominantly found within the Sokoto and Dahomey basins in the Northwestern and Southwestern parts of the country (Figure 1). The Sokoto Basin is characterized by a gently undulating plain with an average elevation of between 250 to 400m above sea level and origin believed to be the subsidence of the cratons because of change in mantle thermal regime and flexural of the lithosphere in response to sediments and water loading (4)(5)(6) .…”