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TitleGeological constraints on rare earth element resources and their availability: a non-partisan view
AuthorSimandl, G J
SourceInternational workshop geology of rare metals; by Simandl, G J (ed.); Lefebure, D V (ed.); 2010-10, 2010 p. 7-8
Alt SeriesEarth Sciences Sector, Contribution Series 20120527
PublisherGeological Survey of Canada
MeetingInternational Workshop on the Geology of Rare Metals; Victoria; CA; November 9-10, 2010
Mediapaper; on-line; digital
File formatpdf
Subjectsrare earths geochemistry; rock analyses, rare earth elements; minerals; mineral exploration; pegmatites; carbonatites; placer deposits; rare earth oxides (REO); metasomatic vein deposits
ProgramRare-Metal Ore Systems, Targeted Geoscience Initiative (TGI-4)
LinksOnline - En ligne
AbstractThe term "rare earth elements" (REE) includes Y, Sc and the lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). Historically, REE were believed to occur only within uncommon mineral species and were very difficult to isolate, hence the name "rare". In fact, REE are nearly as abundant in the Earth's upper crust as the common industrial metals, such as Cu, Pb, Mo, and Zn. Even lutetium, the least abundant of the REE, is approximately 200 times as abundant as Au. The REE are traded mainly as rare earth oxides (REO), pure metals, mischmetal or in the form of chemicals. Anomalous concentrations of REE have been reported from a variety of mineral deposit-types including carbonatites and related deposits, peralkaline igneous complexes, peraluminous igneous complexes, pegmatites, metasomatic veins, Iron Oxide Cu-Au (IOCG) or "Olympic Dam" style deposits and weathered crusts overlying granitic rocks.
Currently, Bayan Obo (a carbonatite-associated deposit mined for Fe, Nb and REE), together with two carbonatite-hosted deposits in China, supply most of world's light rare earth elements (LREE), whereas ion adsorption clay deposits (weathered crusts overlying granites) supply a large proportion of the global heavy rare earth elements (HREE). Rare earth element-bearing minerals also may be obtained from the mining of placer and metasomatic vein deposits, and from the processing of uranium ores and phosphate fertilizers.
Rare earth element production in China started in the early 1980s and since then China has become the dominant producer of REE/REO supplier (> 95% of the world REE in 2009). During this same period, all of the REE mining and REE by-product recovery operations in the western world closed, including the venerable Mountain Pass (USA) deposit that dominated the global REE market from the early 1960s to the early 1980s. The rapid expansion of the Chinese economy during thedemand for REE. To secure supply and provide a competitive edge for its domestic high technology industries, the Chinese government introduced export taxes and export quotas on REE. Not surprisingly, this resulted in rapid global price increases and created uncertainty of REE supply for industrial users outside of China. The United States government considers REE essential for the healthy development of its high technology industries, for its efforts to reduce greenhouse gas emissions, and for its national security. Similarly, REE are now highlighted within the 2010 "Review of Critical Raw Materials for Europe", spearheaded by the European Commission. In general, HREE are more expensive than LREE, although the market is also now experiencing short term price increases of LREE. This spectacular rise in LREE prices is due to a combination of factors including (1) increasing demand, and (2) attempts to stockpile REO by the users to avoid uncertainty and shrinking of the Chinese export quotas.
Over 100 grassroots exploration projects for rare metals are active across Canada. A number of these projects have been tested by diamond drilling. Some of deposits are considered as potential sources of LREE and HREE. Nb, Zr, phosphate, fluorite and/or Fe are potential co-products in some of the deposits. The stricter reporting guidelines for reserve/resource estimations in Canada compared with many other jurisdictions has resulted in fewer Canadian projects in the most recent worldwide REE market/REE resource assessments.
As is the case with most industrial minerals and rare metals, the size of the market, the growth-rate in the use of specific REE, and the prices will strongly influence which exploration stage projects will advance to the development stage. The discovery and development of a single giant and high-grade REE deposit, such as Bayan Obo in Inner Mongolia, would invalidate any of the recent medium to long-term supply/demand projections. Under normal conditions it takes approximately 10 years to move from grassroots exploration to mining. Consequently, short-term predictions would not be affected.
The REE market is global in nature and any new producer will have to be economically competitive on the world-scale. The most attractive primary REE development targets are located in politically stable jurisdictions such as Canada, are close to infrastructure,and have acceptable grade and tonnage characteristics. The latter is important to allow the producer to survive periodic fluctuations in REE prices. Permissive metallurgy, simple coarse-grained homogeneous ores preferably consisting of REE carbonates (such as bastnaesite ± other REE carbonates and fluorocarbonates without Th), REE-bearing phosphates (such as monazite with low Th content), or ion adsorption clays (no breakdown of crystal structure required) is an important component of production cost. Complex REE-bearing silicates (e.g. allanite) are more difficult to crack using conventional, low-cost metallurgical methods. Some of the deposits containing eudialyte group minerals hosted by peralkaline igneous complexes , have been considered potential sources of Zr and HREE since the early 1980s. They still await metallurgical breakthroughs. Favourable market conditions, grade, and metallurgy of individual deposits could allow for REE to be derived as a byproduct of phosphate fertilizer production or uranium processing. It is also theoretically possible that some fluorspar deposits, Ti-Zr-bearing placers, and Olympic Dam-type (IOCG) deposits could enter into the supply-demand equation.