Strontium is widely used in such fields as electronic, chemical, military and light industries and the production of medicines and optical instruments.

      With the uninterrupted growth of the world industry, strontium has found more and more application fields. From the end of the 19th century to the beginning of the 20th century, strontium oxide was used to sugar production to purify beet syrup. During World War II , strontium compounds were widely used to the production of fireworks and signal flares. In the 1920s and 1930s, strontium carbonate was used as a desulfurizing reagent in making steel to remove harmful impurities such as sulfur and phosphorus. In the 1950s strontium carbonate was utilized to refine zinc in the production of electrolytic zinc so that the zinc purity could be as high as 99.99%. At the end of the 1960s, strontium carbonate was widely used as a magnetic material. Strontium titanate was used for producing memories of electronic computers and strontium chloride was used as rocket fuels. In 1968 strontium was found to be capable of shielding X-ray and thus used as screen glass of color TV sets. Its consumption has been increased drastically today. Strontium has found many new applications. Therefore, strontium carbonate and other strontium compounds, which are important inorganic materials, have attracted wide-ranging attention from relevant sectors. Strontium resources are not only of strategic significance for the world, but also become more and more important in the national economy of China.

3.21.1 Resources

3.21.1.1 Reserves and Resources

      By the end of 1997, 13 strontium (celestite) ore districts had been explored in China and the retained reserves of celestite had reached 32.762 million tons with 5.0375 million tons (15.4%) belonging to categories A+B+C in addition to 1.6477 million tons of out-of-balance reserves. The retained reserves can be converted to 15.0706 million tons of metallic strontium, 2.3172 million tons of which belong to categories A+B+C.

      In 1985, the reserves of celestite were only 4.7216 million tons and this figure had been increased by seven times in a period of 10 years since 1985 (Table 3.21.1).

Table 3.21.1 Strontium reserves in 1985~1997(¡Á106 t)

      According to Mineral Commodity Summaries (1996), published by the USA Bureau of Mines, the total strontium reserves of the world were 6.8 million tons and the reserve base was 12 million tons. Such countries as the USA, Mexico, Turkey, Iran and Spain are relatively rich in strontium, but their strontium reserves were far less than those of China. Even the USA, which is most abundant in strontium among the above countries, has reserves of only 1.36 million tons. It can thus be seen that China is the richest country in strontium resources in the world.

3.21.1.2 Characteristics

      The explored strontium deposits are distributed in six provinces, among which Qinghai holds the largest portion of the strontium reserves of China, 15.9115 million tons, amounting to 48.4% of the total retained reserves; Shaanxi comes next, 5.0417 million tons, amounting to 15.3%; and the third is Hubei, 4.7493 million tons, amounting to14.4%, followed by Yunnan, Sichuan and Jiangsu  Provinces (Table 3.21.2).

Table 3.21.2 Major strontium deposits in China

      China has abundant strontium resources and diversified types of strontium ore, occurring in various geological environments with particular patterns.

(1) Huayingshan Sr metallogenic belt in southeastern Sichuan Province

      Sr deposits, characterized by a simple ore type, in southeastern Sichuan are obviously controlled by an anticlinal system related to the ¦Í-shaped Huayingshan folded zone, but industrial Sr deposits occur mainly in the composite anticlinal belt close to the east side of the large Huayingshan fault. The ore-bearing horizons lie in Triassic strata. The Lower Triassic Jialingjiang Formation was formed in the second and fourth members of the Sabkha environment. Some large-sized Sr deposits were explored or found in the aforesaid horizons in the south segment of the Huayingshan ore belt, such as the Gangou deposit in Hechuan, Yuxia deposit in Tongliang and Xinglong deposit in Dazu.

      The Gangou Sr deposit is located in the northwestern branch of the ¦Í-shaped Huayingshan folded system with the ore-bearing belt being 650 m in length and 5~25 m in horizontal thickness. Altogether 5 main orebodies, 10 secondary orebodies and 9 residual orebodies were outlined. The main orebodies are generally stratified or lenticular in form, 50~275 m in length and 20~130 m in downward extension, greatly variable in thickness with the varying coefficients changing from 0.49 to 0.90. It is a large-sized Sr deposit and the explored reserves (SrSO4) are 382,300 tons. It is a deposit of the sedimentary-hot brine superposition (stratabound) type

      The Yuxia deposit is located in the southern segment of the Huayingshan Sr ore belt and its orebodies are controlled by a saddle d¨¦collement structure. It is a large-sized deposit with the explored reserves (SrSO4) of 2.1288 million tons. The metallogenesis is related to sedimentary-structural dynamic reworking.

(2) Yunlong-Lanping-Weixi Sr metallogenic belt

      This belt lies in the northern segment of the Yunlong-Jiangcheng folded zone and the middle part of the Lanping-Simao folded zone, which form a nearly N-S-stretching narrow area between the NNW-striking Deqin-Xuelongshan fault and the Huachangshan fault to the west. There occur deposits or occurrences such as the Hexi Sr (simple ore) deposit and Jinding (simple ore and by-product Sr) deposit in Lanping, Yunnan Province.

(3) Sr metallogenic belt in the western Qaidam basin in Qinghai Province

      The belt is located in areas to the west of the Lenghu-Da Qaidam-Golmud line in the Qaidam basin, i.e. the western part of the Qaidam basin.

      Celestite often occurs beneath gypsum layers and the local structural uplifts (brachyanticlines) are positions favorable for ore formation. The discovered Sr deposits include the large-sized Dafengshan and medium-sized Jiandingshan deposits in Huatugou in addition to some occurrences in Youquanzi, Nanyishan, Huanggualiang, Heiliangzi, Shuangqiquan, Ahati, Cunji and Bageyawuru.

      The Dafengshan Sr deposit in Huatugou is situated on both wings of the Dafengshan composite brachyanticline in the western part of the Qaidam fault basin, where there outcrops the Pliocene Shizigou Formation, which is regional ore-bearing strata. There are four Sr ore districts in this area, composed of two ore-bearing layers and almost a hundred large or small orebodies. Now prospecting is still in progress. Detailed work was done for Ore District IV and the other three districts have not been explored completely. By the year 1996 the explored reserves had been 14.0301 million tons, thus this deposit is classified as a superlarge one. The explored reserves of Ore District IV had been 0.1529 million tons. The metallogenesis is related to inland-lake chemical sedimentation.

(4) Sr metallogenic belt in eastern Hubei Province

      The major segment of the belt is in the Huangshi area. So far one large-sized deposit (in Shizili Mountain) and some occurrences and mineralized localities have been found.

(5) Sr metallogenic belt in southern Jiangsu Province

      The Mesozoic Lishui-Ningwu (IV-order) fault volcanic basin in the Lower Yangtze depression zone (II -order) sits in the Lishui and Nanjing areas in southern Jiangsu. One large-sized deposit (in Aijingshan, Lishui) and one medium-sized deposit (in Wolongshan, Lishui) were explored and one small-sized deposit (in Taishan, Nanjing) was found. Besides, some occurrences, mineralized spots and anomalous areas of strontium ore were discovered in many places, such as Daishan, Xiaoshan, Zutangshan, Jilongshan and Yuntaishan, in the Ningwu basin.

      The Aijingshan Sr deposit lies on the northeastern side of the Mesozoic Lishui continental volcanic fault basin to the south of the Lower Yangtze depression zone. It is a large-sized deposit with explored reserves (categories B+C+D) of 1.2070 million tons. It is of the volcanic hydrothermal filling type.

      In addition to the above deposits and occurrences that are characterized by a simple ore type, there are many by-product Sr deposits. The typical one is the Sr ore district in the middle part of the Longmen Mountains in Sichuan Province. This strontium ore district is associated with phosphorus ore and the Sr-bearing mineral is svanbergite.     

      This ore district is situated in the western part of the Sichuan basin and crosses Shifang and Mianzhu Counties. It is tectonically ascribed to the Pengguan (III-order) upwarping faulted zone in the middle section of the Longmenshan platform-margin folded zone (II -order) of the Yangtze paraplatform. This is one of the major prospective phosphor metallogenic areas in China. The total resources (SrO) are 4.425 million tons. The explored reserves of the Wangjiaping ore district, including the Majiaping and Yanziyan ore blocks, are 2.78 million tons and the other 6 districts (Yuejiashan, Macaotan, Yiangxiongya, Maipengzi, Shisunguangbao and Zaiping) have predicted reserves of 1.64 million tons.

      The Wangjiaping P deposit is the major deposit in the Shifang P ore district in Sichuan Province. It is located on the eastern limb of the Dashuizha anticline in the northeastern part of the Pengguan upwarping faulted zone and phosphor layers are composed mainly of such orebodies as phosphorite and svanbergite. The latter is concentrated in the Majiaping and Yanziyan ore blocks and strontium can be extracted as a by-product from the svanbergite. The Wangjiaping P deposit is a large by-product strontium deposit and belongs to the marine phosphate sedimentary type. Its industrial application has not been finally valued and is temporarily classified as a deposit with non-commercial reserves.

      Among all Sr reserves in China, by-product Sr ores have the largest proportion. According to statistics, the total reserves of by-product Sr ores were 13.2234 million tons in 1996, accounting for 40.2% of the total retained reserves of the whole country. Some major Sr associated deposits are the Shizilishan-Fenglishan Pb-Zn-Sr deposit in Huangshi City, Hubei Province, the Jinding Pb-Zn deposit in Yunnan Province and its Jiayashan and Paomashan ore blocks, and the Huanglongpu Mo deposit in Luonan County, Shaanxi Province.

      The simple ores all have grades lower than 60% (Table 3.21.2) and there are very few rich ores. Such deposits are composed mainly of medium- and low-grade strontium ores, and by-product Sr deposits have even lower grades: 8% of SrSO4 on average for the Jinding Pb-Zn deposit and 4% for the Huanglongpu Mo deposit.

      The explored Sr deposits in China are all large- or medium-sized ones. In light of the classification criteria for the sizes of ore deposits formulated by the National Committee on Mineral Reserves (NCMR) (large-sized Sr deposits refer to SrSO4 reserves larger than 200,000 tons; medium-sized, 50,000~200,000 tons; small-sized, lower than 50,000 tons), all discovered Sr deposits are large-sized ones and the Dafengshan Sr deposit is even an exceptionally superlarge deposit in the world except the Hexi Sr deposit in Lanping, Yunnan Province, and Ore District IV of the Dafengshan Sr deposit in Huatugou, Qinghai Province, which are medium-sized ones.

      So far a rather low degree of geological exploration has ever been done for strontium deposits in China. Only 6.9% of the explored reserves come up to the exploration level, while 72.2% of the reserves to the level of detailed reconnaissance and 20.9% to the level of reconnaissance.