Analysis of the distribution, types, industrial application status, and prospecting prospects of gypsum in China
Li Xiaodan, Wang Chunlian, Huang Keke, Shen Lijian, You Chao, Jiang Huihui, Zhao Yuxin
National Key Laboratory of Oil and Gas Reservoir Geology and Development Engineering at Chengdu University of Technology, Institute of Sedimentary Geology at Chengdu University of Technology, Mineral Resources Research Institute of China Geological Sciences, Key Laboratory of Mineralization and Resource Evaluation of the Ministry of Natural Resources, School of Earth and Space Sciences at Peking University, and School of Land and Resources Engineering at Kunming University of Science and Technology
Summary: [Research Objective] Gypsum is one of the advantageous non-metallic minerals with large reserves and wide distribution in China, and its application is very extensive. Summarizing and analyzing the distribution, genesis, application, and prospecting prospects of gypsum in China is of great significance for the sustainable utilization of gypsum. This article starts with the types, spatiotemporal distribution, and applications of gypsum deposits, summarizes previous research results, and collects relevant information. It systematically sorts out the resource reserves and mining output of gypsum in China, providing background knowledge for searching for new gypsum deposits. 【 Research Results 】 In 2022, the reserve of gypsum resources in China was 1.758 billion tons, with Anhui Province having the largest reserve. The types of deposits are sedimentary, epigenetic, hydrothermal gypsum, and hard gypsum deposits, with sedimentary deposits being the main type. China's gypsum resources are mainly used in industries such as building materials, industry, agriculture, and medicine. The recycling and utilization of gypsum is beneficial in alleviating the shortage of gypsum resources in China. However, the problems arising from the utilization of industrial by-product gypsum cannot be ignored, so we should also pay attention to the development, utilization, and protection of natural gypsum. 【 Conclusion 】 The formation of gypsum deposits is mainly controlled by climate, provenance, and structure. Enclosed and semi enclosed basins, arid and semi-arid climate conditions, and abundant materials promote the formation of gypsum deposits. The Qilian metallogenic belt, Tianshan Beishan metallogenic belt, West Kunlun Altun metallogenic belt, and the middle and lower reaches of the Yangtze River metallogenic belt are important prospective areas for gypsum mineralization in China.
Keywords: gypsum deposit; Resource characteristics; Classification of mineral deposits; Prospecting prospects; Application direction; Mineral Exploration Engineering
Innovation points: (1) A review article summarizing the overview of gypsum deposit resources, classification of deposit genesis, and key field applications; (2) Predict prospecting areas based on the genesis and distribution characteristics of gypsum deposits.
1 Introduction
Gypsum (CaSO4 · 2H2O) and hard gypsum (CaSO4) are produced by the evaporation of saltwater from enclosed seawater, lagoons, salt lakes, etc. (Zheng Ximin, 2019). Gypsum is the most widely distributed sulfate mineral, often coexisting with calcite, dolomite, hard gypsum, calcium saltpeter, rock salt, etc. It also appears in some hydrothermal veins and is an important non-metallic mineral resource. Natural gypsum and its products have many characteristics such as light weight, fast setting, flame retardancy, noise resistance, and resistance to electromagnetic radiation. Therefore, they have been widely used in many industries such as construction and building materials, light industry, precision casting, chemical industry, agriculture, and medicine. In addition, gypsum salt rocks can serve as cap rocks and play an important role in petroleum accumulation (Wang Wenqiang et al., 2017; Liao et al., 2020).
China has abundant gypsum resources, but their distribution is uneven and high-quality resources are limited. Currently, China has become the main consumer of gypsum, and in the future development process, with steady economic growth, rapid development of infrastructure and real estate industries, the gypsum industry in China will have great development space (Li Qilin et al., 2022). At the same time, the national policy on the comprehensive utilization of industrial by-product gypsum also promotes the continuous adjustment of the utilization structure of gypsum resources. If industrial by-product gypsum is utilized reasonably, it can not only meet the demand for gypsum, but also avoid environmental pollution caused by industrial by-product gypsum.
However, there are still some problems in the resource utilization of industrial by-product gypsum in China. Industrial by-product gypsum contains various impurities, and the effects of phosphorus and fluoride on gypsum properties need further research (Jiang Chunzhi and Dong Fengzhi, 2016). Therefore, in-depth research on the distribution, genesis, application, and development and utilization of gypsum resources in China is conducive to providing scientific basis for the rational development and efficient utilization of gypsum resources.
Overview of Gypsum Resources
2.1 World resource endowment
The world's gypsum resources are abundant and widely distributed. More than 100 countries and regions have explored and identified gypsum reserves, but there is a lack of accurate statistical data. According to data from the United States Geological Survey (2022), as of 2022, China's reserves ranked first with 1.5 billion tons, accounting for 41% of the world's known reserves, followed by the United States with 70 million tons, and Brazil and Canada with relatively abundant reserves at 450 million tons (Figure 1). In terms of production, the cumulative production of gypsum in China from 2013 to 2022 far exceeds that of other countries. Before 2016, the production of gypsum mines in China was relatively high, but after 2016, it has relatively decreased (Figure 2).
In 2022, the global gypsum mine production was 150 million tons, with the United States leading the world in production, accounting for 14% of global production. Countries with production exceeding 10 million tons include the United States (21 million tons), Iran (16 million tons), China (13 million tons), Oman (12 million tons), and Spain (11 million tons). From the perspective of mineralization periods, gypsum deposits are widely distributed around the world and have undergone many geological periods. Gypsum deposits have been formed in almost all periods since the Proterozoic era, but mineralization periods are mainly concentrated in the Silurian, Devonian, Permian, Triassic, and Tertiary periods (Charola et al., 2007). At present, the Madus Basin in Australia is home to the world's largest pre Cambrian gypsum deposit, with a sedimentary thickness of up to 260 meters (Lai Ruijuan, 2020).
2.2 China's resource endowment
China has abundant gypsum resources. As of 2019, the confirmed reserves of gypsum resources were 82.51 billion tons. According to data from the Ministry of Natural Resources in 2022, China's gypsum reserves were 1.758 billion tons, with Anhui ranking first with 359 million tons, accounting for 20.4% of the country's total reserves. Shandong (14.6%), Sichuan (10.3%), Yunnan (9.4%), and Hubei (8.9%) followed closely. Among them, the gypsum reserves in East China are the highest, accounting for 35.38% of the national total, while the gypsum resources in Northeast China are relatively scarce, only 1.53% (Table 1).
China has abundant types of gypsum deposits, which are distributed throughout the country. Gypsum is distributed in 23 provinces, municipalities, and autonomous regions in China (YaoruLu et al., 1997). The classification of gypsum deposits in our country into four categories: super large, large, medium, and small, is based on the "Classification Standards for Mineral Resource Reserves" according to the reserve of mineral resources. Deposits with a reserve of more than 30 million tons are classified as large, those with a reserve of 10-30 million tons are classified as medium, those with a reserve of less than 10 million tons are classified as small, and 3-5 large deposits are classified as super large. As of 2021, more than 900 gypsum deposits (points) have been discovered in China (Table 1, Figure 3), including 35 super large deposits, mainly distributed in Shandong and Hubei, 217 large deposits, 173 medium deposits, and 537 small deposits, mainly distributed in Shandong, Hunan, Hubei, Sichuan, Ningxia and other places. Shandong has the largest distribution of gypsum deposits, with a total of 104 deposits. The proportion of super large and large gypsum deposits in Anhui is relatively large, while the number of small and medium-sized gypsum deposits is relatively small. The Zaozhuang area in Shandong, Etuoke Banner area in Inner Mongolia, Yingcheng area in Hubei, Nanjing area in Jiangsu, Dawenkou area in Shandong, and Taiyuan area in Shanxi are important distribution areas of gypsum deposits in China.
3 Types and Typical Deposits of Gypsum Deposits
Lu Zhicheng (1983) classified gypsum deposits in China into three types based on their genetic characteristics: hydrothermal type, steam type, post sedimentary type, and mechanical sedimentary type. According to the Geological Exploration Specification for Gypsum, Celestite, and Diatomaceous Earth Minerals, gypsum deposits in China can be divided into three types: sedimentary type, epigenetic type, and hydrothermal metasomatism type, with sedimentary type deposits being the main type. This article adopts the latter classification method for discussion. According to the existing data statistics (Table 2, Figure 4), the types of gypsum deposits in China are mainly sedimentary, widely distributed, and distributed in every province that has been counted, accounting for 89.5%. The total proportion of epigenetic and hydrothermal types is about 10.5%, and the distribution range is small.
3.1 Sedimentary gypsum and hard gypsum deposits
Gypsum deposits are mainly distributed in sedimentary rock formations and coexist with salt deposits, commonly found in evaporite rock sequences in arid and semi-arid regions. The origin models of gypsum containing evaporite rocks can be divided into two categories (Liu et al., 2018): "tidal Sabuha" and "underwater concentrated precipitation" (Figure 5). The three main factors that control the formation and characteristics of evaporite rocks are climate, provenance, and structure (Warren, 2010; Liu Chenglin et al., 2015). Therefore, the production of gypsum precipitation requires the following conditions:
One is a stable sedimentary environment: Comparing the global plate tectonic cycles since the Neoproterozoic with the sedimentation of evaporite rocks, it has undergone processes such as mountain building, plate assembly, and early continental margin fragmentation since the Phanerozoic, during which a considerable amount of evaporite rocks were produced (Wen Hua Guo et al., 2021). The formation of giant evaporite deposits usually occurs at the beginning or end of tectonic cycles (Gong, 2016); Almost all large evaporite deposits precipitate in closed or semi closed basins (Warren, 2010); The stable tectonic environment of passive continental margins provides long-term stable conditions and sufficient space for the formation of evaporite rocks (Fenquan Xie et al., 2021);
The second is the dry and hot climate conditions: ancient climate conditions play a key role in the formation of evaporite rocks (Liu et al., 2010, 2015, 2016). Evaporite rocks are usually deposited under arid climate conditions, and the net inflow of solute containing water has a high evaporation rate (Keskin et al., 2017; Yin&Li, 2022). Continuous climate drought is conducive to the development of salt lakes and the continuous evaporation and concentration of brine;
The third is abundant material sources: seawater, terrestrial materials, volcanic or magmatic processes, natural hot water solutions (involving high temperature, abundant heat flow, and boiling spring water), and deep brine are important material sources for the formation of evaporite rocks (Wang et al., 2013). Through mantle upwelling and energy accumulation, rift processes and related volcanic activity may generate abundant material sources through the emergence of hydrothermal and saline fluids from the upper mantle and deep crust (Xie et al., 2019).
Sedimentary gypsum and hard gypsum deposits are the main types of mineral deposits in China, and the most industrially significant gypsum deposits currently available belong to sedimentary deposits. This type of deposit is widely distributed in China in terms of time and space, with thick ore bodies and good ore quality, mostly distributed in low latitude areas of modern or ancient times. The Early Middle Cambrian, Middle Ordovician, Early Carboniferous, Early Middle Triassic, Early Middle Triassic, Cretaceous Early Third constitute important gypsum deposits sedimentary type deposits (Huazhi Xin, 2018), with significant mineralization and spatial distribution characteristics. According to different sedimentary environments, sedimentary gypsum and hard gypsum deposits can be divided into marine sedimentary gypsum deposits and lacustrine sedimentary gypsum deposits. Marine sedimentary deposits mostly occurred before the Early and Middle Triassic, while from the Jurassic to the Quaternary, lacustrine sedimentary deposits were predominant. Table 3 lists the spatiotemporal distribution of some super large and large-scale sedimentary gypsum deposits in China.
3.1.1 Marine sedimentary gypsum deposits
Marine sedimentary gypsum deposits often occur in lagoons, coastal Sabuha, intertidal zones, intertidal zones, and subtidal zones. In addition to seawater, the ore-forming materials are closely related to factors such as island arcs, hot brines produced by volcanic eruptions, hydrogen sulfide produced after biological death, the supply of terrestrial materials, and the location of ancient land (Chen Guofang and Xie Feiyue, 2007; Liu Qiyong, 2014).
Generally, in enclosed sedimentary basins, there are reefs or other natural barriers that separate the ocean from the confined sea or lagoon environment. After seawater evaporates, saturated saltwater is left behind, and various minerals can precipitate from the saltwater according to their solubility: first is carbonate, followed by gypsum (a type of calcium sulfate), then rock salt (sodium chloride), and finally bitter magnesium salt residue and potassium salt residue (Figure 6).
China's marine gypsum mines are mainly produced in the Middle and Lower Triassic, Lower Carboniferous, Middle Ordovician, and Lower Cambrian (Zheng Tao, 2013). The Triassic marine gypsum deposit is the youngest, and its geological features of sedimentation, diagenesis, and epigenetic changes are relatively well preserved (Tao Weiping, 1983). The Middle Ordovician in North China is a set of marine carbonate sedimentary rocks, and gypsum deposits are widely distributed in the central region of North China, covering the central and southern parts of Shanxi and Hebei, western Shandong, eastern Shaanxi, and northern Henan (Xue Ping, 1985). Gypsum in the Northeast region mainly occurs in the Lower Cambrian, mainly distributed in the eastern part of Liaoning and the southern part of Jilin. It is produced in the Dongre, Wangou, Xiasiping Hunjiang, Fusong areas of Jilin and the Liaoyang Benxi area of Liaoning, respectively (Zheng Tao and Wen Canguo, 2013). The gypsum in the northwest Qilian Mountains area is found in the Lower Carboniferous, concentrated in the upper part of the Shule Nanshan Chengchenggou Formation in the western section and the Pre Heishan Formation of the Lower Carboniferous in the Tianzhu and Jingtai areas in the eastern section (Gansu Geology, 1987). Due to the expansion of oceanic crust and the movement of tectonic plates, the Early Carboniferous Paleo Tethys seawater flooded the marginal active zone of Qilian through the Tarim Plate, resulting in the formation of gypsum salt flats in the Qilian marginal active zone (Guan Shaozeng et al., 1996). The Yangtze River Basin mainly occurs in the Lower and Middle Triassic (Xue Wu, 1986). The gypsum resources of the Triassic in this region are extremely abundant and widely distributed, from west to east, including eastern Sichuan, Hubei, northern Hunan, southern Anhui, and southern Jiangsu (Bai Shouchang, 1984). The eastern Sichuan region refers to the area east of Huaying Mountain and the eastern part of the Sichuan Basin, and is an important production area for gypsum salt mines in southern China (Xu Xingguo and Xiong Changquan, 1987). The distribution of gypsum deposits from the Cambrian to Triassic periods shifted from north to south, and the distribution area became increasingly wide. The main production areas of marine sedimentary gypsum deposits include Qu County in Sichuan, Nanjing in Jiangsu, Taiyuan in Shanxi, Tianzhu in Gansu, Liaoyang in Liaoning, and Xixiang in Shaanxi.
3.1.2 lacustrine sedimentary gypsum deposits
The formation environment of terrestrial evaporite rocks in geological history is similar to that of Quaternary terrestrial evaporite rocks, mainly formed in mountain basins and desert edge areas with relatively closed hydrogeological conditions (usually in an inland environment), and the basin altitude is generally higher than sea level.
Most of the world's large continental evaporites were formed during the Eocene to Pleistocene periods, and the alternation of rainy and dry seasons in the Neogene glacial environment created favorable conditions for the formation of large continental evaporites.
The terrestrial evaporation environment includes inland Sabha and lakes. The sources of diagenetic brine are complex, including residual seawater, atmospheric precipitation, river inflow, and deep source recharge (Warren, 2016). The material sources include continental weathering products, deep sources, and locally short-lived seawater. The ancient structure is composed of secondary fault blocks and multi-level basins within the basin, and the ancient climate is mostly semi-arid with occasional brief dampness.
During the process of lacustrine sedimentation, faults play an important role in communication and replenishment. The activity and development of fault structures determine the occurrence, development, and formation of gypsum bearing basins. The Tan Lu, Yin Kun, and Da Hinggan Mountains Taihang Mountains Xuefeng faults running in a north northeast direction are the main reasons controlling the formation of the Chenggao fault basin. The intracontinental rift formed by the intersection of these three fault zones and secondary faults plays an important role in the Cretaceous Paleogene salt deposition in eastern China. To the west of the Tanlu Fault, there are gypsum basins such as Dawenkou, Zaozhuang, Dingyuan, and Hengyang; The Yinkun Fault zone includes gypsum bearing basins such as Hangjin, Tongxin, Dayi, and Honghe; Within the Daxing'anling Taihang Mountain Xuefeng fault zone, there are three gypsum basins including Sanmenxia, Miyang, Zaoyang, Yuqing, Huangping, etc. (Huazhi Xin, 2018).
China's lacustrine sedimentary gypsum deposits occur in the Lower and Middle Triassic, Cretaceous, and Paleogene (Ye Lixin, 1980), mainly in large and medium-sized forms. The lacustrine sedimentary gypsum deposits are clearly controlled by their stratigraphy, with gypsum occurring in the Cretaceous Paleogene strata having the most industrial significance. Its distribution range is almost throughout the country, with more concentrated areas in the eastern and northwestern regions of China (Xue Wu, 1986). The gypsum deposit in the Dawenkou Basin of Shandong Province is an important occurrence area of the early third gypsum deposit (Wang Yanting et al., 2014). The distribution area of gypsum in the basin is about 204 square kilometers, and it contains abundant gypsum mineral resources with an economic value of 66.742 billion tons, ranking first in the country in terms of resource reserves (Qin Shouping et al., 2008). The lacustrine sedimentary gypsum produced by the Late Oligocene Qingshuiying Formation in Ningxia was developed in the Tongxin Haiyuan metallogenic area in central and southern Ningxia (including large deposits such as Hejiakouzi and Nigou) and the Yanchi metallogenic area east of Ningxia (including large deposits such as Houjiahe, Chenjiaquan, and Shijichang) (Ma Zhiqiang, 2000).
3.1.3 Typical mineral deposits
1) Tokyo Mausoleum Gypsum Deposit
The Dongjingling Gypsum Mine is located in Luodatai Town, Dengta City, Liaoning Province, and Dongling Town, Taizihe District, Liaoyang City (Pei Yongwan, 2010). It is 7km southwest of Liaoyang City and 13km northeast of Dengta City. The tectonic position of this area belongs to the Sino Korean Quasi Platform (I), Jiaoliao Platform (II), Taizihe Hunjiang Platform Depression (III), and Liaoning Benxi Depression (IV) (Song Chunzhen, 2009). The upper part of the Lower Cambrian Mantou Formation and Jianchang Formation in the mining area is an ore bearing zone with large reserves and good grade. The predicted intrinsic economic resources (333) is 106.51 million tons. There are five gypsum groups (layers) in the mining area, of which the II and III gypsum groups are meaningless because they do not meet the requirements of industrial indicators. The I gypsum group and the IV gypsum group are both hosted under the dolomitic mudstone of the Mantou Formation, the V gypsum group is hosted in the upper part of the Jianchang Formation (Wu, 2019), and the IV gypsum group has three layers of ore that meet the mining standard. The I, IV, and V gypsum groups are introduced as follows (Table 4). Since the Cambrian period, this area has experienced long-term subsidence. At the end of the alkali plant period, the seawater in the coastal lagoon gradually became concentrated, and the concentration of salts increased. Some gypsum and hard gypsum were differentiated and deposited, making it the earliest evaporite rock segment of the Lower Cambrian in this area (Pei Yongwan and Lu Jie, 2007). In the Mantou period, the basement movement was intense, the climate was hot, and the evaporation was large. The regressive sedimentary sequence represented by the terrigenous red bed was deposited. Almost all gypsum layers are controlled by the lithological sequence of dolomite gypsum or brick red dolomitic mudstone (Song Chunzhen, 2009). The primary structure of the ore is fibrous and cryptocrystalline, with a uniform structure. The secondary structures include scale, granular, spotted crystalline structures, as well as fibrous granular crystalline structures, with angular gravel like structures and locally mixed structures (Wu Yun, 2019).
(2) Gypsum deposit in Dawenkou Basin, Shandong Province
The Dawenkou Basin in Shandong Province is a famous lacustrine evaporite sedimentary basin in the early Tertiary period, and also the largest sedimentary and mineral rich basin in the western part of Shandong Province (Zhu Zhongde, 1988). The Dawenkou Basin is connected to the east by the Wendong Depression, Mengyin Depression, and Tailai Depression (Figure 7). The basin is rich in evaporite minerals such as gypsum, potassium salts, and natural sulfur (Cheryl et al., 2023). At present, the proven gypsum resources have reached 15.1 billion tons and potassium salts have reached 9 million tons (Wang et al., 2003; Zhu Meng, 2015; Shi Houli, 2016). In the Dawenkou Basin, gypsum deposits mainly occur in the middle section of the Dawenkou Formation of the Paleogene Guanzhuang Group. This formation is a set of river lake facies clastic rock chemical rock clastic rock deposits (Hao Rui'e, 2023), developed in the gypsum salt facies area, and generally elliptical in shape. It is relatively wide from east to southeast, with an area of about 204 km2, accounting for 64% of the total basin area (Wang Ziju et al., 2003). The lithology consists of gypsum interbedded with mudstone, mudstone, and shale. The ore minerals are mainly gypsum and hard gypsum, while the vein minerals are mainly calcite and clay minerals, with very small amounts of quartz and trace amounts of pyrite (Hao Rui'e et al., 2023).
3.2 Epigenetic gypsum and hard gypsum deposits
Epigenetic gypsum and hard gypsum deposits are formed by the migration, sedimentation, and filling of fractures or caves in ore bearing rock layers after the dissolution of primary ore bodies or secondary changes with limestone (Lv Xianhe, 2011). They are mainly distributed in Guangxi, Hubei, Yunnan, Hunan, Guizhou, and other places in China. According to its filling form, it can be divided into interlayer cracks, oblique bedding, and cave filling.
3.2.1 Interlayer crack filling type
The formation of interlayer fissure filled gypsum deposits is closely related to the degree of fissure development in the strata. Under the combined influence of sedimentation and tectonic processes, a series of fractures with different directions and sizes will develop within calcium bearing rock layers such as limestone. These fissures allow fluids rich in sulfates to migrate between rock layers (Machel H G, 1985). When these fluids encounter reducing conditions or react with other chemical components, minerals such as gypsum will precipitate and gradually fill these cracks.
The interlayer fissure filling type gypsum deposit is characterized by the distribution of ore bodies parallel to the rock layers in terms of geological features. The ore body is generally thin, lens shaped or irregular, and the gypsum morphology ranges from coarse plate-like and columnar crystals to fine needle shaped and fibrous crystals.
The occurrence layer of gypsum is in the Paleogene, the ore type is fibrous gypsum, and the mineral combination is fibrous gypsum, clay minerals, quartz, etc.
High quality fiber gypsum is mainly distributed in Yingcheng and Jingmen in Hubei, Hengyang in Hunan, Xingning in Guangdong, Qinzhou in Guangxi, and other places. Its reserves are relatively small, accounting for only a few percent of the total natural gypsum in the country. The interlayer fissure filling gypsum deposits are mainly large and medium-sized, such as the Yunmeng Stone Gypsum Mine in Yingcheng, Hubei.
3.2.2 Oblique bedding fracture filling type
The formation of inclined bedding fracture filled gypsum deposits is closely related to the action of tectonic stress fields. When the strata are subjected to stress in different directions, it is easy to form a fracture system that intersects with the bedding planes in the rock. These fracture systems enable the migration and precipitation of mineralized fluids at different geological levels. When mineralized fluids containing sulfates migrate along these oblique fractures, the precipitation of sulfate minerals such as gypsum occurs due to chemical reactions or changes in physical conditions in the formation.
These minerals subsequently filled the fractures, forming a deposit of oblique bedding fracture filling type. This type of gypsum ore body occurs in the Paleogene strata, and the scale of the deposit is mostly mineral occurrences, such as Hongmei in Jiuzhou, Huangping, Guizhou.
3.2.3 Cave filling type
The formation of cave filled gypsum deposits is closely related to karstification. In limestone areas, caves of varying sizes are often formed in rocks due to the dissolution of groundwater. These caves provide storage space for mineralized fluids and, under specific geological conditions, lead to the precipitation of sulfate minerals such as gypsum in the caves, thereby forming cave filled mineral deposits (Kirkland D W, 1982).
Cave filling gypsum deposits are typically characterized by mineral filling layers deposited on the inner walls or bottom of caves (Galdenzi S&Maruoka T, 2003). The mineral layer may be layered, lens shaped, or irregular, and the scale of the deposit is usually small. However, due to the enclosed space inside the cave, the mineral filling is often dense, and the grade of the deposit is relatively high. Gypsum can take the form of crystal clusters, fibers, powders, etc. The occurrence layer of gypsum is in the upper Cambrian, and the scale of mineral deposits is mostly mineral occurrences, such as Shuanghe in Suiyang, Guizhou.
3.2.4 Typical mineral deposits
(1) Fiber gypsum mine in Yunying Basin
The Yunying Basin is a basin formed by the activity of the Xiang (Fan) - Guang (Ji) fault zone since the Cretaceous period. The main ore bearing layer of the fibrous gypsum layer vein is the lower gypsum bearing rock section of the Paleogene Eocene gypsum salt formation, which is divided into upper and lower ore bearing layers. White fiber gypsum is enriched into layers due to secondary hydration, and exists in thin layer groups, with a single layer thickness of several centimeters to more than ten centimeters, and some up to 20 centimeters thick. The primary minerals are hard gypsum and some muddy gypsum (Zhu Dejun, 1980). The genesis model of the syngenetic sedimentary fibrous gypsum layer vein deposit in Yunying area (Figure 8) is shown below. Fibrous gypsum appears milky white, sometimes slightly reddish, with a fibrous structure and fibers that are nearly perpendicular to the crack walls. Vein like, reticular, radial, thin layered, and layered structures. The formation of veins cannot be separated from the material basis, vein formation space, hydrothermal transport, and filling precipitation crystallization mechanism (Fang Ming et al., 2022).
(2) Guizhou Suiyang Shuanghe Cave gypsum crystal cave
The exploration length of Shuanghe Cave in Suiyang, Guizhou is 257.4km, with 34 entrances, making it the longest cave discovered in China (Luo Shuwen et al., 2019). The gypsum crystal cave is a branch of the Shuanghe Cave system. Secondary chemical sediments of gypsum caves are distributed in the gypsum crystal cave, presenting various forms. They are widely distributed in the cave, with a large range and an overall pure and transparent appearance. They are extremely rare and different from gypsum caves in other regions. They cannot be touched or easily dropped inside the cave. The gypsum crystal cave is located on the southeast side of the inner nitrate cave in the skin nitrate cave. The tunnel passage is relatively closed, and the cave contains a large amount of gypsum, which is formed by a large amount of secondary leaching, forming a gypsum body (Zhang Shaoyun et al., 2017). The top and walls of the cave, which are about 800 meters long, are covered with gypsum layers. There are various types of gypsum deposits, such as gypsum, stalagmites, stalactites, stone pillars, and gypsum curled stones. The ore body is mainly enriched in the accumulation layer at the bottom of the cave. Due to the limitation of the cave floor, the thickness of the ore body ranges from 0-0.53 meters, with the thickest reaching 3.45 meters. The ore body extends by 40-150 meters and has a width of 10-20 meters. The main types of gypsum ore are dense and earthy, followed by crust like, snowflake like, and fibrous.
3.3 Hydrothermal metasomatism gypsum and hard gypsum deposits
Hydrothermal metasomatism type gypsum deposits are mainly formed by endogenous processes. When sulfides in the rock mass and sulfates in the surrounding rock undergo hydrothermal metasomatism, crystalline gypsum and hard gypsum are formed due to the participation of hot water and natural precipitation (Peng Daming, 1996). The material originates from deep magma and brine, closely coexisting with endogenous metal deposits, and is mainly distributed in the middle and lower reaches of the Yangtze River in China. The distribution of gypsum is comprehensively controlled by three conditions: fracture structures, calcareous surrounding rocks, and intrusive bodies containing metal sulfides and their hydrothermal fluids (Figure 9). According to their location of occurrence, they can be divided into gypsum and hard gypsum deposits related to neutral intrusive rocks and neutral extrusive rocks.
3.3.1 Gypsum and Hard Gypsum Deposits Related to Neutral Intrusive Rocks
The formation of mineral deposits is related to deep magma intrusion, during which high-temperature magma can provide a large amount of heat and mineralized elements. Due to the cooling process of magma, hydrothermal fluids are released, which are rich in various mineralized elements, including sulfates. When these hydrothermal fluids rise, migrate, and cool in the crust, they undergo metasomatism with the surrounding rocks, leading to chemical reactions between sulfates and calcium ions in the rocks, forming gypsum. Due to the fact that intrusive rocks typically form at deeper levels of the crust, gypsum deposits associated with them may form by filling deep fissures or near the contact zone of the intrusive rock mass. These gypsum deposits may coexist with other types of deposits, such as porphyry copper deposits, molybdenum deposits, etc. The occurrence layer of gypsum is in the lower Triassic Yanshanian neutral magma intrusion layer, and the ore body is produced along the contact zone. The ore body is often lens shaped (Lv Xianhe et al., 2011); The scale of the deposit is medium to small, with typical deposits including Chengchao in Echeng, Hubei and Zhang Jingjian in Shandian, Hubei.
3.3.2 Gypsum and Hard Gypsum Deposits Related to Neutral Igneous Rocks
The formation of mineral deposits is related to volcanic activity, usually formed in island arcs or other tectonic environments. Neutral eruptive rocks may be related to geothermal systems, which can generate large amounts of hydrothermal fluids. These fluids may rise along volcanic pipelines, fissures, or faults and undergo metasomatism with surrounding rocks at shallow crustal levels, forming gypsum deposits. The gypsum occurrence layer is a neutral ejecta rock in the early Yanshan period (corresponding to Jurassic strata), and the deposit scale is mainly small. Typical deposits include Xiangshan in Ma'anshan City, Anhui Province and Luohe in Lujiang, Anhui Province.
3.3.3 Typical mineral deposits
(1) Dongcheng Chengchao Mining Area
The Chengchao mining area is located in Ezhou, Hubei Province, in a hilly area. The direction of the ridge line is basically consistent with the direction of the structural line, extending in a northwest southeast direction. The overall terrain trend is high in the northeast and low in the southwest (Deng Yangyang et al., 2019). The magmatic activity in the mining area is extremely strong, mainly dominated by the Yanshanian magmatic activity, strictly controlled by the tectonic pattern formed by the Indosinian Yanshan movement. The active period was mainly in the late Yanshan period, and the magmatic activity in the late Yanshan period mainly occurred in the depression zone. The formation of Chengchao Iron Mine and its surrounding iron deposits is closely related to regional stratigraphy, structure, and magmatic intrusion. The hard gypsum deposits in this area belong to the category of post magmatic medium low temperature hydrothermal filling and metasomatism (Huang Limei et al., 2021). The surrounding rock of the lower wall of the ore body is granite, and the surrounding rock of the upper wall near the ore body is diorite. The surrounding rocks of the upper and lower sides are metamorphic rock belts composed of angular rocks and marble. The gypsum mine in Ezhou City is mainly associated with Chengchao Iron Mine, and the proven reserves of hard gypsum mine are 37.52 million tons. The main mineral resources in the area are hard gypsum rock and iron ore, which are distributed in a vein like and lens like manner near the contact zones between granite and marble, granite and amphibolite, and diorite and granite. The typical profile of the mining area is shown in Figure 10 (Song Xugen et al., 2018)
Hard gypsum ore is mainly developed in the western section of the mining area. Among the 13 known larger ore bodies, five ore bodies, namely No. 1, No. 6, No. 7, No. 9, and No. 10, have larger scales and are the main bodies of coexisting hard gypsum (see Table 6).
4. Gypsum application
4.1 Main purpose
Gypsum is a widely used industrial and building material. Can be used for cement retarders, gypsum building products, model making, medical food additives, sulfuric acid production, paper fillers, paint fillers, etc.
Gypsum is mainly used in the building materials industry and is one of the raw materials for manufacturing building materials such as cement and concrete. Gypsum can be used to produce building gypsum, gypsum boards, and masonry blocks (Jia et al., 2021; Sultana et al., 2022). It has the advantages of low energy consumption, high cost-effectiveness, good fire resistance, and efficient insulation and sound insulation (Fantilli et al., 2021; Li et al., 2023), and can be recycled in appropriate preparation processes. Gypsum has low thermal conductivity and good bonding properties. It is used as a retarder and important cement additive in the cement industry, effectively controlling the setting time, preventing rapid solidification, and improving strength and frost resistance. In the chemical industry, it can be used to produce raw materials for sulfuric acid and ammonium sulfate fertilizers.
In the field of medicine, gypsum has a certain inhibitory effect on the temperature regulation center and sweating center, so it can be used as an antipyretic medicine. Professor Xu Fuye (Huang Bin, 2005) used gypsum to treat external high fever, and there are cases of using gypsum to treat external high fever in his experience collection. Gypsum also has antispasmodic, anti osmotic, anti allergic, and anti-inflammatory effects. Due to its excellent gelling properties, gypsum is also commonly used as a fixing material in orthopedic treatment (Yang Hui, 2022). The microporous structure and heating dehydration characteristics of gypsum and its products make it have good sound insulation, thermal insulation, fire resistance and other properties. This is particularly widespread in construction and biomedical applications, such as as as insulation boards and bone implants (Gao K, 2021).
It is also widely used in decoration. It has the properties of fire prevention, moisture-proof, sound insulation, heat insulation, anti-aging, mothproof, anti-corrosion, light weight and high strength. Its products are bright and white, including high strength, moisture-proof, sound absorption, and radiation prevention. Decorative products such as gypsum decorative boards, gypsum lines, lamp panels, door posts, door and window arches that are fire-resistant and environmentally friendly. Gypsum is used as a filler in the paper, rubber, paint, plastic, textile, and chemical industries. Used as an additive in tofu production in daily life, and also used as chalk, sculpture, art crafts, etc.
In agriculture, it is used as a fertilizer, desalination agent, and soil pH calibrator. When used as soil amendments, gypsum and hard gypsum can produce beneficial effects. They reduce the salinity of saline soils, improve the permeability of clay, and provide sulfur, calcium, and catalytic support, thereby reducing the use of fertilizers and maximizing the economic benefits of crop production. In terms of industrial molds, gypsum can be used as precision manufacturing molds, gold and silver jewelry and aluminum alloy molds, high standard molds in the aircraft, automotive, and machine tool industries, daily ceramic molds, and high-end sanitary ceramic molds (Li Yichen, 2019).
Strengthening the deep processing technology of gypsum and the application of its products can alleviate the problem of low development and utilization of gypsum in China. The deep processing products of gypsum include ultra-high strength gypsum, ultra-fine gypsum powder, and calcium sulfate whiskers (Han Yuexin, 1998). Ultra high strength gypsum materials are mainly used in gypsum ceramic mother molds, precision casting, manufacturing of arts and crafts, toys, permanent building templates, decorative panels, isolation panels, and plastic product vacuum forming molds (Li Ailing, 2004; Zhang Fanfan et al., 2017; Duan Qingkui et al., 2001).
Calcium sulfate whiskers are widely used in rubber, plastics, catalysts, and wear-resistant materials, significantly improving the tensile strength and elastic modulus of the materials (Niu Xiaochao et al., 2022). They can also replace asbestos (which is highly toxic) in friction materials, building materials, sealing materials, insulation materials, and other fields. Gypsum ultrafine powder can be used as a filler for plastics and rubber, improving the mechanical strength, heat resistance, and deformability of high polymers. It can also be used as a white coating for papermaking to improve paper quality.
4.2 Application of industrial by-product gypsum
The comprehensive utilization of industrial by-product gypsum can not only save land resources for landfill and effectively control secondary pollution, but also make full use of resources. China started relatively late in the research on the utilization of industrial by-product gypsum, and most of it is low-end utilization, which is lower than the gypsum utilization rate in Europe, America, Japan and other regions internationally. Higher requirements have been placed on the utilization of industrial gypsum resources.
Industrial by-product gypsum includes desulfurization gypsum, phosphogypsum, titanium gypsum, fluorogypsum, lemon gypsum, etc. Among them, the production of desulfurization gypsum and phosphogypsum accounts for more than 80% of the total production of industrial by-product gypsum. The following mainly introduces the applications of phosphogypsum and desulfurization gypsum.
Phosphogypsum accounts for about 40% of the total production of industrial by-product gypsum and is a key focus of industrial by-product gypsum recovery and treatment. In 2022, the production of phosphogypsum in China will be about 75.1 million tons, with a comprehensive utilization of 36 million tons and a comprehensive utilization rate of 47.9%. From the production, utilization, and forecast chart of phosphogypsum in China from 2010 to 2022 (Figure 11), it can be seen that due to the influence of relevant industries and environmental policies in China in recent years, the comprehensive utilization rate has increased to a certain extent (Li Yichen, 2019). Zhou et al. (2020) conducted an experimental study aimed at producing paper and fiberless gypsum board using only phosphogypsum as raw material. The final gypsum board has high bulk density and mechanical strength, and has the potential to become a new type of wall material with good fire resistance, cost-effectiveness, and environmental friendliness. Mesic et al. (2016) found that PG has beneficial effects on soil, water, and plants. Xiao et al. (2022) conducted research on how to recover gypsum from phosphogypsum. The results indicate that gypsum with a purity of 99% can be obtained from phosphogypsum, with a recovery rate of 80% for CaSO4 · 2H2O and a whiteness of 37.05. This gypsum can be used as a high-quality raw material for producing alpha hemihydrate high-strength gypsum or beta hemihydrate building gypsum.
According to the chart of desulfurization gypsum production and utilization from 2010 to 2019 (Figure 12), we can know that the utilization rate of desulfurization gypsum in China has been above 75% since 2013. In 2018, the production was 72Mt and the utilization rate was 57.9Mt, the highest in nearly a decade, at 80.5%. In 2019, the production was 71.5Mt, the utilization rate was 54.4Mt, and the utilization rate was 76.1%. As an auxiliary material or a substitute for natural gypsum, it can be widely used in concrete, waterproofing materials, cement retarders, walls, cementitious materials, roadbed backfilling, etc. (Sen Liu, 2021; Pedreno Rojas et al., 2020). Desulfurized gypsum and natural gypsum are similar in physical properties, chemical properties, and mineral composition. Desulfurized gypsum can replace natural gypsum as a cement retarder, and the appropriate dosage can improve the compressive and flexural strength of cement (Guo Dajiang, 2010). One of the most important characteristics of desulfurization gypsum is its high purity. The purity of desulfurization gypsum usually exceeds 90% of natural gypsum, with very few impurities. This high purity makes desulfurization gypsum very suitable for various manufacturing processes, such as the production of cement and wall panels (Maiti et al., 2023). It can be used in agriculture and soil as a source of high-quality sulfur and calcium resources, which is beneficial for increasing plant yield (Tao et al., 2019) and improving soil salinity (Wang et al., 2021). The synthesis of high value-added materials using flue gas desulfurization gypsum is also one of the current research hotspots. The main synthetic materials include alpha hemihydrate gypsum dihydrate, calcium carbonate, adsorbent materials, and composite materials (Wang et al., 2019; Wang et al., 2020; Yang et al., 2019). Synthetic materials are an effective way to achieve high-value utilization of flue gas desulfurization gypsum. But most of them are on a laboratory scale, and the industrial production scale is relatively small, so it is impossible to achieve large-scale utilization of desulfurization gypsum (Sen Liu, 2021).
5. Current situation and prospects for exploration and utilization of gypsum industry
5.1 Current situation of gypsum industry
In 2022, the import amount of gypsum in China was 58.5943 million US dollars, and the export amount was 30.7172 million US dollars. According to the data chart of gypsum import and export by the General Administration of Customs from 2016 to 2022 (Figure 13), the import volume of China's gypsum industry is generally on the rise, while the export volume is generally on the decline, and it continues to be in a trade deficit state, indicating that the gypsum produced in China is mainly used domestically. This indicates that the demand for gypsum in China is increasing, and the degree of external dependence is also increasing. Therefore, it is necessary to further increase the exploration efforts.
In recent years, with the continuous expansion of gypsum production scale, by the end of 2020, there was a production scale of 4.78 billion square meters of gypsum board. In addition, the company's layout in the gypsum industry is also accelerating, and gypsum production projects are gradually being put into operation. The anhydrous gypsum project produced by Guizhou Phosphate Group Kaidi Green Building Materials Co., Ltd. was officially put into operation on June 29, 2021. Annual production of 300000 tons of anhydrous gypsum and annual consumption of 420000 tons of phosphogypsum. With the increase of gypsum production projects, not only will the demand for natural gypsum increase, but it will also promote the continuous improvement of the utilization rate of industrial by-product gypsum. However, the problems inherent in industrial gypsum cannot be solved temporarily, so it is even more necessary to make rational use of natural gypsum.
5.2 Prospects for Exploration and Utilization of Sedimentary Mineral Deposits
Sedimentary gypsum deposits account for a large proportion in China and are also the most industrially valuable type of deposits. However, other types of gypsum deposits have little industrial utilization value. Therefore, this article only analyzes the prospecting and utilization prospects of sedimentary gypsum deposits. The formation conditions of sedimentary gypsum deposits mainly include: (1) being located in closed or semi closed basins; (2) Arid and semi-arid climate conditions; (3) Adequate material sources. Based on the above resource characteristics, predict the prospecting prospects of gypsum mines in China. Gypsum deposits are widely distributed in China. Marine sedimentary gypsum and anhydrite deposits are mainly distributed in Liaoning Jilin region, North China region, northwest Qilian Mountain region, Xinjiang, Xizang, Sichuan, Yunnan, Hubei, Hunan, Anhui, Jiangsu, Guizhou, Shaanxi and other provinces; The lacustrine gypsum and hard gypsum deposits are mainly distributed in the eastern and northwestern regions, as well as in provinces such as Shandong, Inner Mongolia, and Hebei. They are controlled by fault basins near rift valleys and occur in the gypsum bearing formations of the Paleogene Neogene variegated clastic rocks (Qin Zhi'an and Li Junjian, 2005). The super large and medium-sized mineral deposits discovered in the exploration work are mainly located in the Qilian metallogenic belt, Tianshan Beishan metallogenic belt, West Kunlun Altun metallogenic belt, Jin Ji metallogenic area, eastern and western edges of the Yangtze River, and middle and lower reaches of the Yangtze River metallogenic belt, mainly distributed in Shandong, Hubei, Anhui, and Hunan. Among them, most of the gypsum minerals in Shandong are from the Cambrian, Ordovician, and Paleogene periods, and the quality of gypsum ore in the Paleogene period is the best. Gypsum bearing basins in the Paleogene period were mostly developed and utilized, and the main mineral is gypsum, with rare occurrences of hard gypsum. The Jurassic Cretaceous period in Shandong region was characterized by a terrestrial arid climate. By the early Eocene, the arid climate intensified, leading to continuous precipitation of ore-forming materials. Since the Late Cretaceous, the western Shandong region has been dominated by fault block uplifts, with some subsidence in the central part, forming a series of inland fault basins. Under the influence of sedimentary structures within the basin, secondary depressions are formed, providing favorable conditions for the sedimentation of mineral deposits. Therefore, from the perspectives of mineralization era, climate, and structural conditions, the inland fault basins of the Paleogene in Shandong are promising areas for searching for lacustrine sedimentary deposits.
The formation of marine carbonate gypsum deposits is strictly controlled by geological structures (Xiao Bingjian et al., 2010). During the Middle Ordovician period, the Shanxi region was located in a continental margin sea environment and experienced multiple occurrences of sea invasions from north to south. When the seawater recedes, the intertidal zone in the southwest is in a dry and hot environment, forming gypsum deposits of the Sabha facies (Chen Guofang and Xie Feiyue, 2007). The tectonic depression zone of the Middle Ordovician in southwestern Shanxi Province is conducive to the search for gypsum. In the exploration of ore in northeast China, where the Lower Cambrian Mantou Formation and Jianchang Formation are developed, the lithology is mainly brick red dolomitic mudstone, purple red argillaceous dolomite, and gray gypsum dolomite. Fracture and fold structures are not developed, and areas with deep burial depth have gypsum prospecting prospects (Wu, 2019). The Cambrian marine areas in North China and Southern Northeast China have the characteristics of large and relatively stable continental shallow sea edge platforms. The tectonic positions of the Chenggao Basin are all located in the depression areas within the Sino Korean paraplatform, such as the Liaoyang Depression, Benxi Depression, Datuoyu Depression, Jilin Hunjiang Depression, and Liuhaihui Depression in the Liaodong Taizihe Complex Syncline, as well as the Liaoxi Depression and Liaonan Depression with mineralization prospects (Luo Dayou, 1985). In some areas of North China, marine evaporites have also been found in the Early Cambrian Mantou Formation, and in layers corresponding to the Taizihe District Jianchang Formation, such as the Zhushadong Formation (Lushan, Henan, Yuanjiazhuang) and Houjiashan Formation (Xuzhou, northern Jiangsu), providing a basis for looking for gypsum. Nine gypsum basins including Jiannan, Lichuan, Enshi, Yuan'an, Puqi, Huangshi, Guichi, Wuwei in Nanjing, and Changzhou in the middle and lower reaches of the Yangtze River have all been found to contain gypsum layers. Their common characteristics are shallow burial, large thickness, and good quality. These gypsum bearing basins are the main directions for future mineral exploration (Bai Shouchang, 1984). The Lengshuijiang Basin, Longhui Basin, and Shuangfeng Basin in the central Hunan region are gypsum basins with abundant reserves (Liu Weihong et al., 1993).
6 Conclusion
(1) Gypsum deposits in China are distributed in Shandong, Hunan, Hubei, Sichuan, and Ningxia. Among them, Shandong has the largest distribution of gypsum deposits. In 2022, the gypsum reserves were 1.758 billion, with Anhui having the largest reserves, and Shandong, Sichuan, Yunnan, and Hubei also having relatively abundant reserves. According to its region, the East China region has the highest reserves, while the North China region is relatively lacking in gypsum resources. The world's gypsum deposits are mainly distributed in the Permian and Triassic strata. China ranks first in reserves, while the United States, Brazil, and Canada have abundant reserves. In 2022, countries with abundant global gypsum mine production include the United States, Iran, China, Oman, and Spain.
(2) According to the genesis of gypsum deposits, gypsum and hard gypsum deposits can be divided into sedimentary type, epigenetic type, and hydrothermal metasomatism type. Among them, sedimentary type is the most important and can be divided into marine sedimentary gypsum deposits and lacustrine sedimentary gypsum deposits. Sedimentary gypsum deposits are determined by climate, provenance, and structure. The formation age of marine sedimentary deposits is early to middle Triassic and earlier, and from Jurassic to the fourth, they are mostly lacustrine sedimentary deposits.
(3) Gypsum is widely used in construction, medicine, decoration, chemical industry, agriculture, and other fields. It can also be processed into ultra-high strength materials, used as gypsum whiskers, and prepared into ultrafine powder. The application of industrial by-product gypsum, especially phosphogypsum and flue gas desulfurization gypsum, is also conducive to alleviating the shortage of high-quality gypsum resources in China.
(4) Extra large and medium-sized mineral deposits are mainly distributed in Shandong, Hubei, Anhui, and Hunan provinces, mainly located in the Qilian metallogenic belt, Tianshan Beishan metallogenic belt, West Kunlun Altyn metallogenic belt, Jin Ji metallogenic area, eastern and western edges of the Upper Yangtze, and middle and lower reaches of the Yangtze River metallogenic belt. The inland fault basin of the Paleogene is a prospective area for searching for lacustrine sedimentary deposits in the Shandong region.
Reprinted: China Construction Research Institute Gypsum Industry Branch
