BORON

Boron is a nonmetallic element. It exists only in the form of compounds in nature, but boron in a dispersive state is ubiquitous in the crust, and it is also an ubiquitous element in surface water, subsurface water, magmatic emanations, mineral spring water and fluid inclusions in all strata.

Boron minerals are versatile chemical mineral materials. They are used in the manufacture of borax, boric acid and elemental boron. Boron is indispensable in glasses, metallurgy, medicines, porcelain enamels, paints, daily chemicals, agriculture and defense industry. Therefore the development and utilization of boron resources have played a more and more important role in the development of modern industry.

China is one of main boron-producing countries in the world and also the country that first found and used boron minerals. As early as 720 A.D., the use of boron minerals as a medicine for curing illness had been recorded in the Tibetan Four Medical Categories. In 1563 China had set up a workshop in Tibet for mining and processing natural borax and the products were marketed to Europe. From the middle part of the 1950s to the present, the boron mineral exploitation has developed rapidly. Several boron mines have been constructed in eastern Liaoning and southern Jilin, and a number of plants of producing boron chemicals such as borax and boric acid have been set up. At present this region is China's most important production base of boron raw materials.

4.10.1 Resources

4.10.1.1 Resources and Reserves

Up to the end of 1997, China had explored 63 boron occurrences with retained B2O4 reserves of 47.009 million tons, of which the occurrences in Liaoning had the most abundant boron mineral reserves, accounting  for 56.7% of the national total reserves and the occurrences in Qinghai are second, accounting for 24.5% of the total. According to the Mineral Commodity Summary 1997, the world's boron mineral reserves were 170 million tons of B2O3 and the reserve base was 470 million tons of B2O3. In 1997 China's categories A+B+C B2O3 reserves were 25.188 million tons. In comparison with the reserve bases of other countries, China ranked fifth in boron mineral reserves in the world.

4.10.1.2 Characteristics of Resources

(1) Geographic distribution

    Boron mineral occurrences of China are distributed very unevenly, mainly in the eastern Liaoning-southern Jilin metamorphosed sedimentary boron minerogenetic belt, the saline lake boron minerogenetic belt of the Qinghai-Tibet Plateau and the skarn-type boron minerogenetic belt from Yeshan, Liuhe, Jiangsu to Huangbao, Zhongshan, Guangxi, and the reserves are concentrated in Liaoning, Jilin, Qinghai and  Tibet. The distribution of boron mineral occurrences in China is shown in Fig. 4.10.1.

(2) Characteristics of boron resources

    1) Many genetic types of boron deposit

    Boron deposits of China have a variety of genetic types, dominated by the metamorphosed sedimentary type, modern saline lake type, skarn salt type and marine sedimentary type.

    Metamorphosed sedimentaty type deposits of China occur in the Neo-archean Kuandian Group in the eastern Liaoning-southern Jilin region in the northeastern part of the Sino-Ko-rean paraplatform. The boron minerals and boron-iron orebodies in the boron-bearing layer of the Kuandian Group formed simultaneously with magnesian carbonate rocks in this layer and

Fig. 4.10.1Distribution of boron deposits of China

1. Gaotaigou boron deposit, Ji'an, Jilin; 2. Zhuanmiao boron deposit, Kuandian County, Liaoning; 3. Wudaoling boron deposit, Kuandian County, Liaoning; 4. Yangmugan, Kuandian County, Liaoning; 5. Hancongweizi boron deposit, Kuandian County, Liaoning; 6. Daxicha boron deposit, Kuandian County, Liaoning; 7. Laohongdingzi boron deposit, Hongshilazi Township, Kuandian County, Liaoning; 8. Wengquangou iron-boron deposit, Fengcheng, Liaoning; 9. Ertaizi boron deposit, Fengcheng, Liaoning; 10. Houxianyu boron deposit, Yingkou, Liaoning; 11. Yilinping lithium-boron deposit, Qaidam, Qinghai; 12. West Taijnar Lake lithium-boron deposit, Qaidam, Qinghai; 13. Da Qaidam Lake boron deposit (including solid and liquid phases), Qaidam, Qinghai; 14. Xiao Qaidam Lake boron deposit (including solid and liquid phases), Qaidam, Qinghai; 15. East Taijnar Lake lithium-boron deposit, Qaidam, Qinghai; 16. Qaidam Playa polassium-magnesium salts-boron deposit, Qaidam, Qinghai; 17. Chalaka boron deposit, G¨º'gyai County, Tibet; 18. Zhacang Caka boron-magnesium deposit, G¨º'gyai County, Tibet; 19. Bangyu Caja salt-boron deposit, Xainza County, Tibet; 20. Zabuye Caka salt-boron deposit, Zhongba County, Tibet; 21. Dujiali Lake boron deposit, Xainza County, Tibet; 22. Qiuli Nam boron deposit, Zhongba County, Tibet; 23. Bangkog Co boron deposit, Baingoin County, Tibet.

later were reworked by regional metamorphism and migmatization. Saline lake boron deposits occur on the Qinghai-Tibet Plateau. The en-bloo uplift and differential sinking of the Meso-Cenozoic fold belts and basins on the Qinghai-Tibet Plateau resulting from the collision with the Indian plate brought about the upwelling of boron-bearing hydrothermal fluids from deep levels of the crust and the disintegration of boron-bearing rocks such as Cenozoic boron-bea-ring intermediate-acid volcanic rocks and accumulation of boron. Then the climate of these basins on the plateau at elevations of 4,000 to 5,000 m above sea level became dry progressively, so boron minerals were able to be accumulated to form boron deposits. Endogenic skarn boron deposits were mainly formed in the Yanshanian period. Influenced by the plate movement, repeated magmatic activities took place in the NE-trending fold belt of the South China platform. Then metasomatic anatexis occurred between aluminosilicate solutions and carbonate rocks, thus forming magnesian skarn and calcareous skarn in the contact zone. Magnesium borate (szaibelyite-ludwigite) deposits just occur in magnesium skarn.

     2) Many species of boron minerals and many associated minerals

     The main constituent minerals of metamorphosed sedimentary boron deposits include magnesium borate minerals (szaibelyite, ludwigite etc.), silicate minerals (forsterite, humite, ilmenite, hematite, uraninite etc.), sulfides (pyrrhotite, pyrite, chalcopyrite etc.), sulfate minerals (gypsum, apatite etc.) and phosphate minerals.

    Boron minerals of saline lake boron deposits on the Qinghai-Tibet Plateau are closely associated with a few dozens of elements such as sodium, lithium, potassium, chlorine and sulfur.

    The ore composition of endogenic skarn boron deposits is also relatively complex, and useful boron minerals such as ludwigite and szaibelyite are associated with a large amount of magnetite.

   3) Large reserves but poor ore quality

   There are appreciable quantities of boron ore reserves in China, but the greater majority of boron ores are low-grade and the boron ores with a boron content lower than 12% contribute about 90.74% of the country's retained reserves. Boron ores of metamorphosed sedimentary boron deposits may be divided into three ore types, szaibelyite ore, ludwigite ore and szaibelyite-ludwigite ore on the basis of their useful components. Their average grade is only 8.27%. Of the three ore types, szaibelyite ore is relatively easy to dress, whereas for boron minerals of the other two ore types, their processing problem has not been completely solved now because they are intimately associated with iron and other minerals and occur as very fine-grained disseminations. The saline lake boron deposits of the Qinghai-Tibet Plateau are divided into solid and liquid deposits. The average B2O3 content of the solid boron deposits is only 3.33%, while that of the liquid boron deposits (brines from saline lakes) is 866.16 mg/L. The ores of endogenic skarn boron deposits has an average grade of only 6.6%.

   At present more than 95% of boron materials processed are szaibelyite ore, but it only contributes 6.64% of the total reserves. The ludiwigite ore that accounts for 58.54% of the total reserves is scarcely used because its processing technology has not been completely solved. Saline lake boron ore that takes up 33.13% of the reserves has basically not been developed and utilized now because of limitations of transport and mining conditions of the Qinghai-Tibet Plateau.

   4) Overconcentrated distribution of boron occurrences

   Most of boron deposits and reserves of China are concentrated in Liaoning, Jilin, Qinghai and Tibet. The retained boron ore reserves of the four regions account for almost 90% of the national total, and the rest less than 10% of reserves are scattered in Hubei, Hunan etc.