Rare earth elements: a new scope of mining for saving energy and environment
|Location||International Geological Congress,oslo 2008|
|Holding Date||08 October 2008|
Dissemination of hybrid and electric vehicles is important for reduction of hydrocarbon fuel consumption, which can contribute the decrease of CO2 dispersion as well as NOx and SOx dispersion into the atmosphere. Production of hybrid vehicles is enabled by installing a motor with Dy-bearing NdBFe magnets (rare earth magnets) in the engine. NdBFe magnets are also equipped in many other parts of a modern vehicle, in addition to the use of light rare earth elements (REEs) in the nickel-hydrogen battery. Thus, REEs are indispensable for the production of environment-friendly vehicles, as well as other modern energy-saving electric products. For this reason, the demand of REEs is increasing year by year, resulting in the increase of REEs prices and shortage of some REEs such as Dy and Nd. Now rare earth mining has an important role to realize the energy-saving society by supplying REEs, and presents a new scope for the mining industry, which is generally regarded as "against environment".
The total production REEs since 1900 is only about 2.2 million tons as rare earth oxides, but the demand of REEs is expected to increase dramatically up to 8-10 million tons in the next 30 years. The production of REEs has been nearly monopolized by China since late 1990s due to low REEs production costs and presence of REE-smelting and utilization industries, despite an estimation of huge REEs reserves in many other countries in the world. The present major sources of light REEs are bastnäsite and monazite from the Bayan Obo iron oxide-REE deposit in Inner Mongolia and bastnäsite from the carbonatite and/or alkaline rock deposits in Sichuan. Heavy REEs are mainly supplied from ion-adsorption deposits related to weathering of reduced-type granites in southern China. However, the production of REEs in China, especially that from the ion-adsorption deposits, will be limited for the preservation of natural environment and protection of mineral resources.
To respond the increasing demand of REEs, development of rare earth deposits in other parts of the world, such as high-grade carbonatites at Mountain Pass in the USA and Mount Weld in Australia, is indispensable, although these deposits are depleted in heavy REEs. Possible sources of heavy REEs are 1) magmatic-hydrothermal apatite, 2) xenotime in placer deposits, 3) ion-adsorption and laterite deposits, and 4) REEs-enriched peralkaline igneous complex. Among these four types, the first two types may supply REEs in a shorter period, because they can produce REEs as the byproduct of other minerals. Peralkaline igneous complex may become the ultimate source for REEs in future, because of their huge potential.