Bayan'obo Mining District, ( Mongolian: ''Bayan Oboɣ-a Aɣurqai-yin toɣoriɣ'', Баян-Овоо Уурхайн тойрог ( mn, italic=yes, "rich" +

ovoo Ovoo, oboo, or obo ( mn, овоо, bua, обоо, kjh, обаа, Traditional Mongol: , "heap"; Chinese: 敖包 ''áobāo'', lit. "magnificent bundle .e. shrine) are sacred stone heaps used as altars or shrines in Mongolian folk religious p ...

); ), or Baiyun-Obo or Baiyun'ebo, is a mining town in the west of

Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...

, People's Republic of China. It is under the administration of

Baotou Baotou (; mn, Buɣutu qota, Бугат хот) is the largest city by urban population in Inner Mongolia, China. Governed as a prefecture-level city, as of the 2020 census, its built-up (''or metro'') area made up of its 5 urban districts is ...

City, the downtown of which is more than to the south. The mines north of the town are the largest deposits of

rare-earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides ( yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

s yet found and, as of 2005, responsible for 45% of global rare-earth element production. In the satellite image at right, vegetation appears red, grassland is light brown, rocks are black, and water surfaces are green. Two circular open-pit mines are visible, as well as a number of tailings ponds and tailings piles.NASA Bayan Obo image and writeup
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Economic geology

China produced about 81,000 tons of rare-earth metals in 2001; the number jumped to about 120,000 by 2006. According to the Chinese Society of Rare Earths, of waste gas—containing dust concentrate, hydrofluoric acid, sulfur dioxide, and sulfuric acid—are released with every ton of rare metals that are mined. Approximately of acidic wastewater, plus about a ton of radioactive waste residue are also produced.

Mine deposit

Very large rare-earth elements (REE) Fe-Nb deposit (Bayan-Obo type), discovered as an iron deposit in 1927. REE minerals were discovered in 1936, and

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has s ...

-bearing ores in the late 1950s. Reserves are estimated at more than 40 million tons of REE minerals grading at 3–5.4% REE (70% of world's known REE reserves), 1 million tons of Nb₂O₅ and 470 million tons of iron. The deposit also contains an estimated 130 million tons of

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs sca ...

. Bayon Obo is the world's largest known REE deposit. The fluorite content of the ores also makes it the world's largest fluorite deposit. The deposit occurs in an east–west trending

Mesoproterozoic The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic), ...

rift zone along the northern margin of the Sino-Korean Craton. Host strata are quartzite, slate, limestone, and dolomite. Dolomite is the main host rock. The orebodies are stratiform and lenticular, with masses, bands, layers, veins, and disseminations. Besides clear features of

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

mineralization, the deposit also exhibits Mg, Fe, Na and F

metasomatism Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical co ...

. Sm-Nd

monazite Monazite is a primarily reddish-brown phosphate mineral that contains rare-earth elements. Due to variability in composition, monazite is considered a group of minerals. The most common species of the group is monazite-(Ce), that is, the ceriu ...

isochron age for bastnaesite and riebeckite is 1200 to 1300 Ma, whereas Th-Pb and Sm-Nd age of Ba-REE-F carbonates and aeschynite is 474 to 402 Ma. at

Mindat.org Mindat.org is a non-commercial online database, claiming to be the largest mineral database and mineralogical reference website on the Internet. It is used by professional mineralogists, geologists, and amateur mineral collectors alike. The ...

Economic geology

Mine deposit

See also

References

Further reading