4.8.1.1 Reserves and Resources

China is very rich in salt resources. It has not only abundant sea salt resources but huge, densely distributed saline lakes and numerous underground brine and rock salt deposits with plentiful reserves.

China's salt resources show a basic distribution pattern of sea salt resources in the easte-rn part, lake salt resources in the western part, and well salt and mineral salt resources in the middle part.

(1) Sea salt resources

China's sea salt resources are mainly distributed in the eastern coastal areas. China has a long coastline, which stretches for 18,000 km from the Yalu River estuary, Liaoning Pro-vince in the north through to the Beichang River mouth, Guangxi Zhuang Autonomous Region in the south, involving 11 provinces (autonomous regions and municipalities). Should the coastline of offshore islands be included, the total length of China's coastline would reach 21,000 km. The principal coast type of the Chinese continent is the plain coast, which is favorable for drawing water from the sea to make salt.

By the end of 1997, beach salterns of 43.45 km2 had been built. They constitute two sea salt zones: northern and southern. The northern zone, the principal sea salt producing zone, consists of the salt fields in 5 provinces (municipalities): Liaoning, Hebei, Tianjin, Shangdong and Jiangsu, which have an aggregate area of 38.75 km2, making up 89.18% of the total area of China's saltfields. Among these saltfields, those in Shandong are the largest in area, accounting for 30.52% of the aggregate area of the saltfields in the northern sea salt zone, while the saltfields in Jiangsu and Hebei comprise 23.22% and 21.55%, respectively. The important saltworks in this zone are the Yingkou Saltworks in Liaoning, the Fuzhouwan Saltworks in Dalian, the Tanggu Saltworks in Tianjin, the Nanbao Saltworks in Hebei, the Jiangsu Salt Industry Company, etc. The southern sea salt zone involves Zhejiang, Fujian, Guangdong and Hainan Provinces and the Guangxi Zhuang Autonomous Region, with an aggregate area of saltfields reaching 4.70 km2, whichconstitute only 10.82% of the country's total area of saltfields. In the southern sea salt zone, the saltfields in Zhejiang, Fujian and Guangdong are the major producers. The large-sized salterns in the southern zone include the Yinggehai Saltern in Hainan and the Putian Saltern in Fujian. Besides, there also exist saltfields in Tunghsiao, Lukang, Peimen, Hsikang  and Tainan along the west coast of Taiwan Province.

(2) Salt mineral resources

By the end of 1997 China had verified 151 mineral occurrence localities of salt, including those of lake salt, brine and rock salt and owned retained NaCl reserves of 384,339 million tons and ore reserves of 20,643 million tons. These reserves are widely distributed in 18 provinces (regions). Among them, Qinghai, Jiangxi, Hubei, Yunnan and Sichuan are pro-vinces, each of which is possessed of NaCl reserves exceeding 10,000 million tons (Table 4.8.1).

Table 4.8.1 Retained Reserves of Salt Ores of China (1979)

In the salt mineral resources of China, the saline lake resources are mainly distributed in the modern arid and semi-arid climatic zones of 74¡ã~125¡ãE and 25¡ã~50¡ãN in the western part of China. The lake salt reserves verified in the saline lakes are concentrated in Qinghai Province and autonomous regions such as Xinjiang, Inner Mongolia and Tibet, and the well-known lake salt occurrence localities include the Qarhan and Dalangtan Salt Lakes in Qinghai and the Jarantai Salt Lake in Inner Mongolia.

As part of the salt mineral resources of China, the rock salt and brine salt resources are widespread and abundant in reserves. Their occurrence localities are mainly distributed in 14 provinces (regions), including Jiangxi, Hubei, Sichuan, Yunnan, Jiangsu, Hunan, Shandong, etc., predominantly in the central part of China. The major rock salt and brine salt occurrences are the Qinjiang and Zhoukou salt deposits in Jiangxi, the Yunying salt deposit

Fig. 4.8.1Map of the distribution of salt deposits in China

1. Aqikesu, Xinjiang; 2. Yanshankou, Xinjiang; 3. Aydingkol Lake, Xinjiang; 4. Baytik Mountain Salt Lake, Xinjiang; 5. Lop Nur Lake, Xinjiang; 6. Gomo Caka, Tibet; 7. Dogyaling Lake, Tibet; 8. Chabyer Caka, Tibet; 9. Dalangtan, Qinghai; 10. Kunteyi Salt Lake, Qinghai; 11. West Taijnar Lake, Qinghai; 12. East Taijnar Lake, Qinghai; 13. Qarhan Salt Lake, Qinghai; 14. Hoh Salt Lake, Qinghai; 15. Caka Salt Lake, Qinghai; 16. Yabrai Salt Lake, Inner Mongolia; 17. Jarantai Salt Lake, Inner Mongolia; 18. Eren Salt Lake, Inner Mongolia; 19. Laizhou Saltfield, Shandong; 20. Dawenkou salt deposit, Shandong; 21. Yuncheng salt deposit, Shanxi; 22. Huaiying salt deposit, Jiangsu; 23. Dongxing salt deposit, Anhui; 24. Wucheng salt deposit, Henan; 25. Wangcheng salt deposit, Hubei; 26. Xiaoban salt deposit, Hubei; 27. Yunying salt deposit, Hubei; 28. Qianjiang salt deposit, Hubei; 29. Hengyang salt deposit, Hunan; 30. Qinjiang salt deposit, Jiangxi; 31. Zhoutian salt deposit, Jiangxi; 32. Longgui salt deposit, Guangdong; 33. Jiangyou salt deposit, Sichuan; 34. Chengdu-Pujiang salt deposit, Sichuan; 35. Weixi salt deposit, Sichuan; 36. Chuanzhong salt deposit, Sichuan; 37. Dianjiang salt deposit, Sichuan; 38. Changning salt deposit, Sichuan; 39. Zigong salt deposit, Sichuan; 40. Anning salt deposit, Yunnan; 41. Wenka salt deposit, Yunnan; 42. Mengyejing salt deposit, Yunnan; 43. Zhengdong salt deposit, Yunnan; 44. Mengla salt deposit, Yunnan; 45. Xiangli salt deposit, Hunan.

4.8.1.2 Characteristics

(1) Characteristics of sea salt resources

The surface-layer salinities of the offshore waters of China show a distribution regularity: low in near-shore zones, high in open sea areas and even higher in Kurushio zones, and have a close relationship with seasons: high in winter and low in summer. In winter, the surface-layer seawater salinities average 31.5¡ë in the Bohai Sea, 34¡ë in its central part and less than 26¡ë in its coastal zone; they are in the range of 31¡ë~32¡ë in the northern part of the Yellow Sea and 31.5¡ë~32.5¡ë in the southern part; they are 33¡ë~34¡ë in the most part of the East China Sea, lower than 20¡ë in the area of the Yangtze River estuary, and 34.5¡ë in the zone the Kuroshio flows through. In summer, they average 25¡ë~30¡ë in the Bohai Sea and 30¡ë~32¡ë in the Yellow Sea, and are the lowest, down to below 5¡ë, at the Yangtze River estuary but remain to be around 34¡ë in the Kuroshio zone of the East China Sea. The seawater salinities along the coast of China vary in the range of 26.0¡ë~31.0¡ë in the Bohai and Yellow Seas, 24.0¡ë~32.0¡ë in the East China Sea and 27.0¡ë~34.0¡ë in the South China Sea, and they are very low in all estuary areas.

China's coastline consists of 3 types of coasts. The first type is plain coasts, i.e., the continental coasts of the Bohai and Yellow Seas distributed to the north of the Hangzhou Bay. They are mostly made up of enormously thick but loose sandy or silty sediments, belonging to the "puddly coast", and are favorable for constructing large and medium-sized saltfields. The second type is embayed coasts, which are mainly distributed along the East China Sea's continental coasts of Fujian and Zhejiang Provinces to the south of the Hangzhou Bay. They are mostly composed of bedrocks and therefore are also called "bedrock coasts". Coasts of this type are characterized by indented fjords, steep slopes and great water depths but along them there exist plain type coasts of small sizes in river-mouth areas which are good for building medium-sized and small saltfields. The third type is biogenic coasts, which may be subdivided into two subtypes: coral-reef coasts and mangrove coasts. The coasts of this type are distributed along the Taiwan Straits and South China Sea's coasts of southern Fujian, Taiwan, Guangdong, Guangxi and Hainan provinces and the South China Sea Islands. Along the coastal zones of this type there occur plain-type coasts where it is possible to construct salterns.

The sea-salt producing region of China is divided into two zones: northern and southe-rn. The northern one is the principal sea salt zone, which consists of the sea salt producing areas along the coastal zones of Liaoning, Hebei, Tianjin, Shandong and Jiangsu to the north of the Yangtze River. This zone has an annual precipitation of about 500~900 mm, which is concentrated in June-August, and an annual evaporation of about 1,500~1,800 mm. The salt production season of the northern zone consists of the spring sun-drying period and the autumn sun-drying period. The southern sea salt zone covers the coastal areas of Zhejiang, Fujian, Guangdong, Guangxi, Hainan and Taiwan to the south of the Yangtze River. The southern zone is characterized by high air temperature, plentiful precipitation and great evaporation. In this zone, the method of evaporating the seawater in the sun to make salt in consecutive fine days is adopted and the salt production can be carried out all the year round, but due to the great difference in precipitation, evaporation and climatic condition the seasonal sun-drying salt production periods also differ slightly from area to area (Table 4.8.2).

Table 4.8.2 Precipitation, evaporation and salt production peak season of the sea-salt producing region

(2) Characteristics of lake salt mineral resources

The lake salt mineral resources of China mainly occur in the saline lakes scattered all over the arid-semiarid zones in the western part of the country. The salt deposits were formed in the Quaternary and commonly have not experienced any exogenetic geological process. Salt deposits may occur in the state of solid, liquid and solid-liquid phases. When subjected to the lixiviation by surface water, groundwater and atmospheric precipitation, the solid-phase salt bodies may change to brine (liquig phase); the saline lake brine may gradually get concentrated and crystallized to give rise to solid-phase salt bodies. Such a solid-liquid transformation is a major characteristic feature of lake salt deposits.

Lake salt deposits may be classified into the following three types in terms of the mode of occurrence:

1) Solid-phase lake salt deposits.

    They refer to the completely dried, brineless playas and the lake salt deposits dominated by solid Na-salt deposits. Solid lake-salt deposits are commonly exposed to the surface or buried at a shallow depth. The salt bodies occur in the stratified or stratoid forms, spreading over a large area, up to scores or hundreds of square kilometers with a thickness of several meters. The salt ores are dominated by halite in mine-ral composition and have a NaCl content exceeding 70% in most cases, and they usually contain various saline minerals such as mirabilite, gypsum, trona, sylvite, carnallite, magnesian salt and borates. The salt ores have a low hardness and are easily mineable. Solid-phase lake salt deposits are the principal targets of exploitation. They are represented by the Qarhan Silatu Lake in Qinghai, the Jarantai Salt Lake in Inner Mongolia, etc.

2) Liquid-phase lake salt deposits (otherwise termed brine salt lake deposits)

    They refer to brine lakes without any sedimentary bed of halite or brine lakes with salt deposits below the indices of industrial exploitation. Brine salt lake deposits are rich in Na, K, Ca, Mg, B, Li, Br, I, Rb, Cs, Sr and other elements, but no large-scale development and utilization of such deposits have been carried out so far, except for the small-scale intermittent exploitation of only some individual brine lakes. Their representative deposits include the Ebinur Lake in Xinjiang and the Kunteyi Salt Lake in the Qaidam Basin of Qinghai.3) Mixed phase lake salt deposits with the solid and liquid  phases in coexistence    In salt deposits of this type solid-phase and liquid-phase salt bodies coexist and the solid salt and li-quid salt can be simultaneously mined. Such salt deposits are represented by the Eren Nur Salt Lake in Inner Mongolia and the Qijiaojing Salt Lake in Xinjiang.

(3) Characteristics of rock salt mineral resources

Rock salt mineral resources refer to the ancient solid salt mineral deposits formed prior to the Quaternary in general. For China's ancient salt mineral deposits, the essential salt-forming epochs are the Sinian, Triassic, Cretaceous and Tertiary and those of secondary importance are the Middle Ordovician, Early Permian, and Jurassic.

According to such factors as the depositional environment and material source, rock salt deposits can be classified into two types: marine sedimentary and continental sedimentary.

1) Marine sedimentary rock salt deposits.These deposits were formed by the evaporation and deposition of saline materials derived from the seawater in closed and semi-closed bays and lagoonal basins over a long period of time. Their salt-bearing rock series are mainly made up of carbonate formations in addition to the arenaceous and argillaceous rock formations of littoral lake facies. The marine salt deposits are characterized by large size, deep burial, unitary ore composition, high NaCl content (commonly 80%~95%), and abundant reserve. Over 10 rock salt deposits in China are known to have an explored NaCl reserve of over 10 billion tons each. The representative deposits are the Weixi salt deposit in Sichuan and the Middle Ordovician salt deposits in Linfen of Shanxi and Yanchang of Shaanxi. The explored salt reserves of the marine rock salt deposits of China amount to 85% of the country's total reserves of all salt mineral deposits.

2) Continental sedimentary rock salt deposits.    These rock salt deposits were formed by the prolonged evaporation and deposition of saline materials after they had been brought by the surface water and groundwater to and accumulated in inland basins. The salt-bearing rock series are all composed of arenitic and pelitic rock formations. The continental facies rock salt deposits are characterized by shallower burial depth, smaller mineralization area and lower NaCl content (commonly 70%~80%) than those of the marine facies salt deposits, large number of salt beds, small single-bed thickness, presence of many associate components and frequent facies variation. The continental rock salt deposits of China were primarily formed posterio to the Jurassic and are concentrated in Yunnan, Hunan, Henan, Jiangxi and other provinces. They are represented by the Yunying salt deposit in Hubei.

Rock salt deposits are preliminarily divided into 3 industrial types with 9 subtypes in accordance with their industrial significance, and the requirements of geological exploration and production technology with comprehensive consideration of the genesis, salt ore composition, tectonic deformation and other features of the deposits. For details see Table 4.8.3.

Table 4.8.3 Industrial Types of Rock Salt Deposits of China

(4) Characteristics of subsurface brine salt deposits

     Subsurface brine salt deposits refer to salt deposits occurring in a liquid-phase state in subsurface strata. They can be formed in both ancient and modern times. The subsurface brine salt deposits formed in modern times have been discussed in the previous paragraphs pertaining to liquid-phase saline-lake salt deposits.

      The ancient subsurface brine salt deposits will be dealt with in the following text.The anicent subsurface brine salt deposits of China are mainly distributed in Sichuan, Hubei and other provinces in the central part of China and are most concentrated in the Zigong area of Sichuan Province.

      The subsurface brine salt deposits can be divided into 3 genetic types:

      1) Sedimentary type brine deposits.

     The subsurface brine with a high total solinity, also termed the primary connate brine, was formed as a result of the concentration and metamorphism of the fossil seawater that had been stored between sand grains in the diagenetic process or had entered pores and fissures after the diagenesis of sedimentary rocks.

       2) Leaching type brine deposits.
    The subsurface brine was formed as a result of accumulation of the ground water that had dissolved the saline materials in rock beds or mineral deposits in the process of its movement.

       3) Mixed sedimentary-leaching type brine deposits.

       The subsurface brine was formed by the mixing of the sedimentary type brine with the leaching type brine in the process of their underground migration.

       Subsurface brine salt deposits are divisive into 3 groups as follows:

       1) Porous type subsurface brine deposits.

       They are represented by the Qianjiang subsurface brine salt deposit in Hubei Province.

       2) Fissure type subsurface brine deposits.

      The representative deposit is the Zizhong subsurface brine salt deposit in Sichuan.

      3) Combined pore-fissure type subsurface brine deposits.

       The Baimuqiao mirabilite-brine deposit in Danling County, Sichuan is their representative.