3.22.1.1 Reserves and Resources

      There are abundant REE resources in China and now 193 mines have been explored with cumulative reserves of more than 100 million tons (referring to TR2O3, hereinafter). By the end of 1997 the retained reserves had been 90.8003 million tons (the percentages used to convert xenotime and monazite to TR2O3 are 62% and 65%, respectively), of which categories A+B+C reserves are 28.2331 million tons. It is known by comparing China's categories A+B+C reserves of REE with the reserve base of foreign countries of the same period that China ranks first, the former USSR second (21 million tons) and the USA third (14 million tons) (Mineral Commodity Summaries, 1999).

      China is also rich in resources of dispersed metals. The retained Ge reserves are 3,782 tons, 98,907 tons for Ga, 13,378 tons for In, 8,302 tons for Tl, 16,715 tons for Se, 13,331 tons for Te, 261 tons for Re and 401,931 tons for Cd.

3.22.1.2 Characteristics

      In China, REE resources have a fairly wide distribution and there are 193 ore districts possessing explored reserves, which are distributed in 17 provinces and autonomous regions: Inner Mongolia, Jilin, Shandong, Jiangxi, Fujian, Henan, Hubei, Hunan, Guangdong, Guangxi, Hainan, Guizhou, Sichuan, Yunnan, Shaanxi, Gansu, and Qinghai. The reserves of Inner Mongolia amount to 93.2% of the China's total; Guizhou, 1.6%; Hubei, 1.3%; and Sichuan, 1.1%. The reserves of the other provinces and regions amount to 2.8% of the total REE reserves of China. Table 3.22.1 presents the major REE deposits and related information.

Table 3.22.1 Major REE deposits in China

Note: Large deposit:>500,000 tons for primary REE (TR2O3);>10,000 tons for placer and monazite;>5,000 tons for xenotime;>5,000 tons for fergusonite.

      Dispersed metals are distributed in the following regions. There are 33 germanium ore districts in 11 provinces or autonomous regions, of which Guangdong, Yunnan, Jilin, Shanxi, Sichuan, Guangxi and Guizhou have reserves constituting 96% of the China's total; 112 gallium ore districts in 21 provinces and autonomous regions, including Shanxi (amounting to 26% of the total reserves of gallium of China), Jilin (20%), Henan (15%), Guizhou (13%), Guangxi (9%) and Jiangxi (5%); 59 indium ore districts in 15 provinces and autonomous regions, including Yunnan (40%), Guangxi (31.4%), Inner Mongolia (8.2%), Qinghai (7.8%) and Guangdong (7%); 12 thallium ore districts in 7 provinces and autonomous regions, including Yunnan, Guangdong, Gansu, Hubei, Guangxi, Liaoning and Hunan, among which Yunnan makes up 94% of the total reserves of thallium; 53 selenium ore districts in 18 provinces and autonomous regions, including Gansu (41.2%), Heilongjiang (10%), Guangdong (8.9%), Qinghai (8.8%), Hubei (8.7%) and Sichuan; 26 tellurium ore districts in 15 provinces and autonomous regions, including Jiangxi (41.6%), Guangdong (41.3%) and Gansu (10.7%); 11 rhenium ore districts in 9 provinces, including Shaanxi (44.3%), Heilongjiang (31.6%), Henan (12.7%), Hunan, Hubei, Liaoning, Guangdong, Guizhou and Jiangsu; 148 cadmium ore districts in 24 provinces and autonomous regions, among which the following 9 provinces and autonomous regions each have 10,000~100,000 tons of reserves: Yunnan (45.7%), Guangxi (7.7%), Sichuan (7.1%), Guangdong (6.2%), Jiangxi, Gansu, Inner Mongolia, Hunan and Qinghai.

      The development of REE resources of China has the following features.

      1) The resources of REE, especially LREE, are highly concentrated. Although such ores are found in North China, Northeast China, East China, South-Central China, Southwest China and Northwest China, they are mainly distributed in the Fe-Nb and REE ore districts in Bayan Obo, Inner Mongolia, where the reserves of REE account for 95% of China's total. This area is the major LREE production base of China.

      2) LREE is distributed mainly in northern China, while HREE in southern China. Especially in the Nanling Mountains area, there occur considerable amounts of ion-adsorbed middle REE, HREE ores, which can be mined and extracted without difficulty and this area has thus become an important production base of middle and heavy REE. Moreover, in southern China weathering crust deposits and beach sedimentary placer are also found, some of which are rich in xenotime (HREE mineral material). In southern Jiangxi (e.g. Xihuashan and Dangping), some vein tungsten deposits are associated with xenotime, gadolinite, yttrofluorite and fergusonite, which can be recovered and utilized during the dressing and smelting processes of tungsten ore.

      3) Over two thirds of the discovered 100-odd REE districts are associated or by-product deposits, which are good for multipurpose utilization. However, most of them are difficult for ore dressing due to very complicated compositions and fine imbedded grains. For instance, there are more than 70 elements and over 170 minerals discovered in the Bayan Obo deposit, which is a superlarge deposit of REE and rare metals in the world with huge reserves of REE, Nb and Ta. In this deposit, iron ores are associated with monazite, bastnaesite, cordylite and huanghoite. Despite complicated textures and fine imbedded grains, the grades and recovery ratios of these minerals have been greatly improved after repeated tests and analyses of ore dressing and smelting. This ore district has become one of the most important REE bases in China.

     4) China has enormous reserves and complete varieties of REE metals, which provide superior resources for the development of REE metals industry. The explored REE reserves are over 100 million tons. Minerals and ores of 16 REE elements have been found in China with promethium being the only exception. In all explored deposits, 16 REE metals have been extracted from ores or minerals by means of dressing and smelting processes. At present hundreds of varieties and over thousands of specifications of REE products have been produced, which can meet domestic demands and at the same time are exported in great quantity, thus becoming major commodities for earning foreign exchange.

      One of the distinct features of China's dispersed ore resources is the comparatively concentrated distribution, hence such elements are sometimes considered "not dispersed". Over 80% of Ge reserves are distributed in Guangdong, Yunnan, Jilin, Sichuan and Shanxi, occurring mainly in Pb-Zn and Cu deposits and coal mine and 82% of Ga reserves in Shanxi, Henan, Guangxi and Guizhou, occurring mainly in bauxite deposits. Indium ore deposits occur concentratedly in Yunnan, Guangxi, Inner Mongolia and Qinghai, amounting to 87% of the total indium reserves of China. Re occurs almost in Mo ore deposits, mainly in the Jinduicheng Mo deposit in Shaanxi, Luanchuan Mo deposit in Henan, Daheishan Mo deposit in Jilin, and Duobaoshan Cu (MO) deposit in Heilongjiang, amounting to 90% of China's total. More than 90% of Tl reserves are concentrated in the Jinding Pb-Zn deposit in Lanping, Yunnan Province. Te occurs as a by-product metal mainly in the Dabaoshan polymetallic sulfide deposit in Guangdong, Chengmenshan Cu deposit in Jiangxi and Jinchuan Cu-Ni deposit in Gansu, accounting for 94% of China's total. However, a Te deposit was discovered recently in Dashuigou of Shimian County, Sichuan Province. In contrast, Cd and Se have a relatively sporadic distribution, found in 24 and 18 provinces and autonomous regions respectively.

      Two evident geological features can be seen with China's REE deposits. First, the deposits are characterized by multistage telescoped mineralization. For instance, the Bayan Obo Fe-Nb-REE deposit in the Inner Mongolia metallogenic belt is a superlarge REE deposit featuring multistage telescoped mineralization, which is rarely seen in the world. Recent study in regard to the metallogenic epoch of this deposit done by Yuan Zhongxin et al. shows that the REE minerals were formed mainly in the middle Proterozoic (1,400~1,600 Ma) and that the ores were formed by way of sedimentation. In the Caledonian, secondary mineralization of REE took place in company with the invasion of alkaline carbonatite magma and possible alkaline gabbro magma. In the Hercynian, the deposited ores were subjected to transformation due to the invasion of granite magma in the southern part to form new late-stage REE ores. The second feature shows that the Yanshanian is the major metallogenic age of the deposits of rare and rare earth elements in China. Especially in the south China metallogenic belt, such deposits were mostly formed in the Yanshanian. These deposits are of granite type, pneumatolytic-hydrothermal and hydrothermal type, pegmatite type, alkaline rock and alkaline granite type, and volcanogenic hydrothermal type. Besides, the Maoniuping REE deposit found in Mianning County, Sichuan Province, is considered to be formed in the Himalayan Age.

      The REE deposits of China can be grouped into the following 10 types.

       1) Bayan Obo type Fe-Nb and REE deposit

      This is a unique superlarge REE deposit in the world, well known for its large size, huge reserves and high grade of cerium group REE. It is an important base of great economic value for REE production. There have been several views as for the genesis of the deposit. It is considered as a deposit of different types, such as special hypothermal, metamorphosed sedimentary-hydrothermal metasomatic, magmatic carbonatitic, volcanic carbonatite sedimentary, stratabound or hot-brine sedimentary deposit or a deposit of composite genesis.

        2) Granite type Nb-REE deposits

      These are magmatic deposits related to granitoid, distributed mainly in southern Jiangxi, northern Guangdong, southern Hunan and eastern Guangxi. They generally have large reserves and stable grade with good prospects, but these deposits have rather low grade and fine grain size. So far large-scale exploitation or utilization has not been carried out. Over these deposits, however, weathering crust deposits and alluvial placers are often developed, which are easy to be mined and dressed and have a significant industrial value. In the 1950s and 1960s, mining was undertaken mainly for such REE minerals as monazite, xenotime and fergusonite.

        3) Granite pegmatite type REE deposits

      These deposits are rich in rare elements such as lithium, beryllium and tantalum, but there are few deposits containing rich REE. Only in Jiangxi have REE-Nb-Ta-Li pegmatite type deposits been discovered. Deposits of this category are characterized by high grade of REE and large grain size and are easy to mine and dress, but they generally do not have large scales.

       4) REE-bearing fluorine carbonate hydrothermal vein deposits

      Deposits of this type are LREE ones of great economic value. At present the Maoniuping REE deposit (large-sized) in Mianning, Sichuan Province and the Xishan REE deposit (medium-sized) in Weishan, Shandong Province have been explored. These deposits are often related to alkaline intrusive rocks with large sizes and rich REE. The major ore mineral is bastnaesite. They are rich in cerium, praseodymium and neodymium. The ores are free-milling with large embedded grain sizes. The above two deposits have been mined to yield considerable economic and social profits.

       5) Nb-REE-bearing syenite-carbonatite type deposits

      These deposits are characterized by large size and numerous associated or by-product components and are of high value for multipurpose utilization. 1,215,000 tons of LREE oxides and 929,500 tons of Nb2O5 were explored in the large-sized Miaoya Nb-REE deposit in Zhushan, Hubei Province, located in eastern Qinling area around the border of Hubei and Shaanxi and awaiting development and utilization.

      6) Weathering crust REE deposits

      Deposits of this category are extensively distributed in granite and migmatite areas and some REE-bearing volcanic terrains in the Nanling region and Fujian Province. There are two types of weathering crust REE deposits: monomineral type and iron adsorption type. For the former, rare earth elements appear generally as rare earth minerals and the type of industrial minerals is dependent on the protolith. Some deposits are predominated by fergusonite and some by xenotime and monazite. These deposits are easy to exploite and have become major sources of HREE. The latter is a new type, whose REEs are adsorbed as ions on the surface of clay minerals. They are easy to extracte and have large scales and have become major sources of heavy and middle REE in China. Deposits of this type are of great economic and social value and widely distributed in many areas in southern China.

       7) Alluvial placer of monazite and xenotime and beach place

      Monazite and xenotime placer deposits are commonly found in Quaternary alluviums in eastern and central China and southwestern Yunnan. The parent rocks are ore-bearing granite and migmatite and the newer the geomorphologic unit, the higher the concentration and grade of placers. They have small sizes, but are easy to mine and have a great economic value, distributed mainly in the coastal areas in Guangdong and Hainan.

      In addition, there are three more types, namely chemical-sedimentary REE-bearing phosphorite deposits, metamorphosed sedimentary Nb-REE-P deposits and migmatite type REE deposits,  which are of less significance compared with the above seven types.