Thematic Issue: Rare Earth Resources: Are They Sufficient or Deficient?

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This thematic issue is composed of the papers presented at the symposium “Rare Metals–Rare Earth Resources” of the annual meeting of the Society of Resource Geology held in Tokyo, Japan, on 19 July 2007. The symposium was organized by Shunso Ishihara, Hajime Hishida and Yasushi Watanabe. Seven of the 11 topics presented in the symposium were related to rare earth elements (REE), reflecting their recent increasing demand and prices (Fig. 1). The Japanese REE market and industry expect new REE suppliers to develop outside China, because of the decreased availability of rare earth materials for import from China. Production of rare earth elements (REE) and prices of dysprosium (Dy), neodymium (Nd) and neodymium-praseodymium (Nd-Pr) in the last two decades. CIF, cost, insurance and freight; REO, rare earth oxides. The articles in this thematic issue include a review of rare earth deposits in North America (Castor, 2008), a recent interpretation of the genesis of the world’s largest Bayan Obo deposit in China (Wu, 2008), and two papers and a note that describe the relationship between rare earth mineralization and granite (Ishihara, 2008; Ishihara et al., 2008; Murakami & Ishihara, 2008). This issue also includes a review article on the rare earth magnet by Minowa (2008), and an article on rare earth enrichment in stratabound manganese deposits in India (Moriyama et al., 2008). Minowa (2008) provides basic information on recent demand for neodymium and dysprosium, which is caused mainly by the production of dysprosium-bearing neodymium magnets in China and Japan. He estimates that 16,000 t of neodymium and 2600 t of dysprosium will be necessary to produce alloys for the magnets in 2010 for the world market. The review of rare earth deposits of North America by Castor (2008) concludes that world reserves are sufficient to meet international demand for most REE commodities in the 21st century and the development of new REE deposits in North America is unlikely in the near future because Chinese producers, especially those at Bayan Obo, are capable of large REE production at low prices. Details of Bayan Obo are reviewed by Wu (2008), who suggests a hydrothermal origin related to carbonatite magmatism for the deposit. Ishihara et al. (2008) describe the mineralogical and geochemical characteristics of the granites related to ion-adsorption REE deposits in southern China, which are the current source for heavy REE. Ishihara (2008) also discusses the occurrence of REE-enriched zircon in the Naegi granite in Japan. Murakami and Ishihara (2008) investigate REE abundance in the weathered crust and clay sediment above granitic rocks in Japan and China, and describe the ore grade and composition of the currently mined Dingnan deposit in southern China. Moriyama et al. (2008) explore manganese deposits for a new heavy REE source. They have found REE enrichment up to 975 ppm in stratabound or stratiform manganese deposits in Orissa, India, and suggest that this enrichment was caused by hydrothermal activity during deposition. The papers in the present issue conclude collectively that heavy REE such as dysprosium will become scarce in the future despite the large reserves of total REE in the world, because the current supply source of heavy REE is limited to ion adsorption deposits in China. I am convinced that the studies of the geneses of the ion adsorption deposits and related granites, some of which are presented in this issue, will be utilized for future world exploration of this type of deposit.