Metallurgy of Key Minerals - Thanatia: The Destiny of the Earth's Mineral Resources - page 230

As the temperature rises, liquefaction proceeds and the concentration of incompat-
ible trace elements attenuates to the point of complete melting. This explains why
partial melting of the mantle concentrates rare earths. Additionally, the lanthanide
contraction sheds light on why the lighter rare earths (LaEu) are more abundant
than the heavier ones (Ho to Lu), being La +3 the largest ion and Lu +3 the smallest
one. Consequently, a low percentage of mantle melting implies larger concentrations
of light rare earths, which penetrate and crystallise in the crustal hollows (Nelson,
2012).
8.13.3 MainREEdeposits
As already mentioned, the largest bastnaesite deposits, which also contain other
types of REE minerals, occur at Bayan Obo, Inner Mongolia (5% ore grade) and
the Maoniuping deposit (4% ore grade), in Sichuan province, China, as well as
Mountain Pass in the United States. Monazite deposits from marine sands are found
in Australia, Brazil or India and form large rock veins in South Africa. Additional
and smaller rare earth deposits exist in Malaysia, Sri Lanka, Thailand, elsewhere in
the United States, Russia, Kazakhstan and Kyrgyzstan. The ion adsorption clays,
providing the world's primary source of yttrium production, can be found in the
southern Chinese provinces of Jiangxi, Guangdong, Hunan and Jiangsu. Some of the
concentrate ores here contain as much as 65% yttrium oxide which is accompanied
by the heavy lanthanides. Jiangxi clays frequently contain the rare earth oxides
(REO) of Y (60%), Dy (8%), Er (5%), Y b (3.5%), Ho (1.5%), Tm (1%)
and light REO of Gd (7%), La (2-5%), Nd (5%), Sm (4%), Pr (1-2%), Tb
(1.5%), Ce (1%) and the remaining REO which account for less than 1% (Gupta
and Krishnamurthy, 2005).
According to USGS (2012) rare earth global reserves are increasing yearly 27
with the number currently standing at around 114 million tonnes. China with
48% of all commercially exploitable rare earth, ranks first followed by the ex-Soviet
states 17%, the U.S. 11%, India 2.7%, Australia 1.4%, and others - a category
including the Indochinese countries and Greenland 19%. These reserves are 877
times greater than current world production (130,000 tonnes in 2012). Whilst there
may be reserves, world demand which is rising 7.1% annually greatly outstrips
supply. Risk to further supplies is at a critical stage given that 97% of current REO
production originates from China, a country which since 2005 has imposed strict
export quotas. According to Chinese authorities, exports have been decreased in
response to natural resource depletion, increased illegal mining activity, detrimental
environmental impacts and the desire to promote domestic markets involved in
downstream processing industries. The world's response has since been an unbridled
race towards the opening of new mines across the face of planet. According to
Gibson and Parkinson (2011), in less than 5-10 years, new REE mine projects
27 In 2008, reserves were estimated at 99 million tonnes - see Table 6.10 on page 162.