The boundary between Qingfeng-Xiangfan-Guangji deep fault and Qinling geosyncline is distributed in the phosphorus accumulation area of western Hubei in an east-west direction. The area south of the fault, including Xingshan County, Shennongjia Forest Region, Xingshenbao Phosphate Mine, Yichang Phosphate Mine and Jingxiang Phosphate Mine in Baokang County, is called Western Hubei Phosphorus Accumulation Area (Figure 3-3).
The geotectonic layer in western Hubei, which consists of Neoproterozoic Wudang Group, Shennongjia Group, Kenling Group and Yangpo Group, formed a relatively open platform edge fold belt after Jinning (Xuefeng) movement. Chengjiang movement not only inherited the compression in NE-SW direction, but also produced the compression stress in SN- direction and NW-SE direction, which made the sedimentary basement structure and landform of Doushantuo period complex and diverse, with the last continental margin. There are ancient land (island) (Wudang ancient island), large short-axis underwater uplift (Shennongjia uplift, Huangling uplift and Xinbaopo uplift), small anticline (fold) or secondary uplift and depression (Figure 3-4). Another notable feature is that there are groups of NW-trending anticlines and synclines connected with them on the east side of the three large-scale underwater uplift, and some of them form a consortium. A large number of phosphate deposits were controlled, and three ore concentration areas, Xingshenbao, Yichang and Jingxiang, were formed respectively. The phosphorus-rich area in western Hubei ranks first among the nine phosphorus-rich areas in the Yangtze block in terms of geographical area and ore reserves.
To sum up, the sedimentary basement structure of Doushantuo Formation in the phosphorus accumulation area of western Hubei is complex and diverse, and it can be roughly divided into three levels (types) according to its nature and scale. The first stage is based on Wudang ancient land (island) and its depressions on the south and north sides, as well as faults in the east-west and northwest directions, and the second stage consists of three large underwater highlands (ancient uplift areas). The third stage is tectonic-paleogeographic landscape (Figure 3-4). On the east side of the above three large underwater highlands, several groups of NW-trending (a few EW-trending) secondary anticlines (folds) are developed, and combined arc structures are formed at the contact parts. When the ocean current rising from east to south arrives, the phosphorus and other substances it carries are retained, especially when it meets the three large uplift ridges of Shennongjia, Huangling and new castle Slope and their group backs on the east side. The anticlinal belt on the east and north sides of Shennongjia uplift forms Xingshenbao ore concentration area, the anticlinal belt on the east side of Huangling uplift forms Yichang ore concentration area, and the anticlinal belt on the east side of Xinbaopo uplift forms Jingxiang ore concentration area. This is a very important ore control (prospecting) model.
Figure 3-3 Regional Geological Map of Phosphorus Accumulation Area in Western Hubei
(According to Hubei Institute of Geology and Mineral Resources 1985)
Figure 3-4 Schematic Diagram of Paleostructure in Doushantuo Period of Late Sinian in Phosphorus Accumulation Area in Western Hubei Province
(According to Hubei Institute of Geology and Mineral Resources 1985, revised and supplemented)
1~ 3 —— East-west structural belt: uplift belt axis, depression belt axis, compression or compression-torsion fault; 4 ~ 6— NW structural belt: uplift belt axis, depression belt axis, compression or compression-torsion fracture; 7 ~ 9— the combined arc structural belt of east-west structure and northwest structure: uplift belt axis, depression belt axis, compression or compression-torsion fault; 10 —— a composite structural belt spanning the NE-trending structure to the NW-trending structure: the axis of the depression belt; 1 1- ancient land; 12- transgression direction; 13- sedimentary isobath; 14- fracture number; 15-number of bulges and depressions; 16-number of large-scale uplift; 17- sedimentary facies boundary
Fault name: ① Mapo fault; ② Baihe-Xiangfan fault; ③ Qingfeng fault; ④ Jiudao-Yangri fault; ⑤ Qingquan fracture; ⑥ Banqiao fracture; ⑦ Wuduhe fault; Attending Tian Yang Ping fault.
Name of uplift and sag: ① Yunxi-Danbei-Xiangfan sag belt; ② Wudang Mountain uplift; ③ Xinbaopo uplift belt; ④ Qingquan-Jingmen depression zone; ⑤ Tiejiangya uplift; ⑥ Xiaofeng depression; ⑦ Name of the larger uplift of Liantuo Uplift: Ⅰ Shennongjia Uplift; Ⅱ Huangling uplift; Third, Baoxinpo uplift
The overall geographical landscape of the Doushantuo period in the phosphorus accumulation area in western Hubei is adjacent to Wudang ancient island in the northwest, with high terrain. Maoshanyan in Baokang and the northern wing of Huangling anticline are exposed from time to time, eroded and gradually reduced to the east and south. The Maliang-Xianju area in the middle is a broad and gentle underwater uplift (Baofenpo uplift), and the Doushantuo Formation has only a few tens of meters of sediments, while the sediments on its north and south sides and the eastern depression area are 200-300 meters thick (Figure 3-5). It shows the complexity of the basement structure and paleogeography in the phosphorus accumulation area, which is also very clear in the specific phosphate rock area. Let's take Xingshengbao phosphate mine area as an example to illustrate.
The sedimentary basement of Doushantuo Formation in Xingshenbao Phosphate Mine is the metamorphic rock series of Shennongjia Group. Chengjiang movement formed a wide and gentle uplift belt and fault structure in the northeast of the mining area, formed east-west folds and faults in the north, and formed local small bumps and depressions in the central and western regions. The tectonic movement comes from the compressive stress in SN- direction, which makes the basement structure more complicated, resulting in different and complicated structural patterns in the eastern, western, northern and middle stages of Doushantuo period. Only the local areas in the east and middle of the mining area are selected for overview.
Fig. 3-5 Paleogeographic Diagram of Doushantuo Period in Late Sinian in Western Hubei.
(Modified by Li Yinhou, 1984)
1-argillaceous siltstone; 2- limestone; 3- dolomite; 4- conglomerate; 5- Shale containing potassium and phosphorus; 6- phosphorite layer; 7-phase boundary; 8— Isothickness line of Doushantuo Formation
Within the range of north-south 1 1km and east-west 3.5km, there are three mining areas: Baizhu, Zhengjiahe and Wawu (Figures 3-6 and 37). The three mining areas are close to each other, and the strata composition and thickness of phosphorus-bearing rock series are basically the same. North to Baizhu, south to Zhengjiahe mining area and the middle of Wawu mining area, it is a NE-trending "S"-shaped paleouplift belt. Baizhu and Zhengjiahe mining areas are located in the northwest of the uplift zone, and Wawu mining area is located in the southeast. The silty carbonaceous mudstone at the bottom of phosphorus-bearing rock series gradually thickens along both sides of the uplift zone. Mudstone landslide curl structure was found in Baizhu mining area, and the sliding direction was NNW. Landslide structure has also been found in Wawu mining area, and the sliding direction points to SE. Phosphate rocks are deposited on the two wings of the uplift zone, and the central phase of the uplift zone becomes fine-grained dolomite. The absence of phosphorite only has horizon significance, indicating that the uplift zone is a basement highland, and phosphorite is deposited in the basement depression and its transition zone with basement highland.
In the central area of Wushan, two small depressions with a length of about 4km and a width of about 65438±0.2km were deposited in the Doushantuo Formation of Wushan Phosphate Mine within 25km2 (Figure 3-6).
The complex paleostructure and paleotopography in the eastern and central parts above reflect the tectonic-paleogeographic characteristics of mineralization in the phosphorus accumulation area in western Hubei.
2. Wengfu Phosphate Mine in the phosphorus accumulation area in central Guizhou.
Phosphate rock is distributed in the two wings of Baiyan-Gaoping anticline (basement highland), and the anticline is NNE-SSW direction. The North Baiyan mining area includes five mining areas, namely Yuhua, Wangjiayuan, Datang, Chuanyandong and Xinqiao, and the South Baiyan mining area includes four mining areas, namely Mofang, Xiaoba, Dazhai and Yingping (Figure 38). The dip angle of coal seam in the north of Baiyan mining area is 25 ~ 35 in the west wing of anticline and 60 ~ 75 in the east wing. The dip angle of coal seam in the south of Gaoping mining area is small, and the two wings of anticline are similar, both less than 20. The lower coal seam of Yuhua ore block in the north of Baiyan mining area becomes thinner to the south, and it is missing in the north of Wangjiayuan and Datang ore blocks, indicating that the lower coal seam was raised as an ancient topographic uplift area when it was deposited.
Figure 3-6 Geological Map of Phosphate Rock in Xingshengbao Area, Western Hubei Province
Figure 3-7 Structure and Paleogeography of Baizhu-Wawu Mining Area
1-presumption of coastline or uplift; 2- direction of underwater landslide; 3— the direction of water flow reflected by asymmetric wave marks; 4— Oblique bedding tendency; 5- stromatolite tendency
3. Kaiyang phosphate rock in the phosphorus accumulation area in central Guizhou.
Phosphate rocks are distributed in the two wings of Yangshan anticline (basement highland), and the anticline is NNE-SSW-oriented, including seven ore sections: Wenquan, Liangchahe, Ji Le, Shabatu, Yongshaba, Maluping and Niuchongchong (Figure 3-9). The whole mining area is 17.5km long from north to south and 4.5 ~ 5.7 km wide from east to west. Metamorphic rocks of Qingjiang Formation in Banxi Group are exposed in the core of anticline, and the two wings are Sinian and Cambrian in turn. The phosphorus-bearing rock series is represented by the section of Maluping ore section, which is merged into two lithologic sections, and the lower section is sandstone section, and its thickness gradually becomes thinner and thicker from north to south. The thickness of the hot spring ore section in the north is close to 18m, the thickness of the Jile ore section in the middle is 1 1m, and the thickness of the Shaba ore section in the south is 7m, indicating that the paleotopography in the south is higher than that in the north.
Figure 3- 10 shows that Kaiyang Phosphate Mine is a semi-closed depression bounded by Qianzhong Uplift, and there is a primary NNE-trending Xiangyang Water Uplift in the middle of the depression. The overall tectonic palaeogeographic landscape is a pattern of three ridges and two depressions distributed in the northeast. The Shui Yang uplift is asymmetric, with steep west wing and gentle east wing, so the sedimentary scale formed in the eastern sag is much larger than that in the western sag. The underwater uplift in central Guizhou emerged from the water surface at the initial stage of phosphorus-containing rock series deposition, providing terrigenous sand and forming sandstone formations in the lower part of phosphate rock layer; In the upper phosphorite section, the average thickness of the seam in the whole area is about 7m, and the thickness has no obvious change, indicating that the lower sandstone section is deposited in the depression area. After "leveling", a 7m thick phosphorite layer was deposited in the whole area, forming a thick and high-grade ore layer, and the average grade of the whole ore (P2 O5) was between 34% and 36%.
Fig. 3-8 Schematic diagram of ore segment division of Wengfu Phosphate Mine in Guizhou.
Figure 3-9 Geological Schematic Diagram of Kaiyang Phosphate Mine in Guizhou
Four. East Yunnan ore concentration area
The eastern Yunnan ore concentration area starts from Qiaojia in the north and reaches Huaning in the south, which is a huge ore concentration area. The basement structure and topography in the area are complex, and there are many groups of protrusions and depressions, which control the geometric shape of phosphorus-bearing rock series sediments (Figure 3- 1 1).
Verb (abbreviation of verb) Kunyang-Haikou phosphate rock
1) In the lower part of the upper coal seam (equivalent to the sixth layer of the standard section in the first section of Chapter 4) in Mingyihe ore section of Haikou Phosphate Mine, the curled structure formed by landslide can be seen locally, and the direction of landslide is about NNE20, indicating that there are paleogeomorphic bulges in SSW direction here when phosphorus-containing rock series are deposited.
2) Underwater uplift. There is an underwater uplift belt between Kunyang Phosphate Mine and Haikou Phosphate Mine, and its modern feature is Xiangtiaochong anticline (Figure 3- 12). It has been proved by exploration that the thickness of phosphorus-bearing layer in the two places gradually increases along the slope direction of underwater uplift zone, and the ore layer increases by 1 ~ 2m( 1000m per extension 1 ~ 2m). 1987), but the lower coal seam near the axis of underwater uplift in Kunyang phosphate mine area is missing, and the weathering crust is seen on the top surface of the floor, indicating that the underwater uplift has partially exposed the horizontal plane and settled to accept deposition.
3) There is a dome-shaped highland between Kunyang Second Street and Shu Mei Village, which lacks the lower coal seam and the following layers (see standard section 1 ~ 4 in the first section of Chapter 4). The fifth layer is the interlayer between the upper and lower coal seams, which contains hydromica clay rock containing pozzolanic phosphorus, directly covering the underlying small failed mountain section, and the bottom plate has a thin layer of iron weathering crust (Zhang Zhaoxian,1988).
Figure 3- Schematic diagram of phosphate basin bounded by Qianzhong Uplift 10
(According to Sinochem Guizhou Geological Exploration Institute, 2009)
Comparing the three NW-SE profiles of Mingyi River, Kunyang and Wangjiawan, the thickness of Mingyi River is 22.5m, that of Zhongyi Village in Kunyang is 1 1.6m, and that of Wangjiawan is 54 m. According to the ore-controlling principle of geoid, taking the top surface of the sea section as the leveling surface, it is clearly indicated that Kunyang area is an ancient landform highland, and its NW and SE are high.
4) The phosphate rock in Kunyang is locally within 28m, and the pit with 2m depth is filled with phosphate rock (Figure 3- 13).
6. Caopu Phosphate Mine in Anning County, Yunnan Province
The basement topography of Caopu Phosphate Mine is complex. In some areas, phosphorite is directly deposited on the karst landform formed by dolomite. Karst caves are generally several meters deep, and the deepest reaches 18m. The thickness of phosphorite represents the depth of the dissolution pit. The thickness of phosphorite in some areas varies from 0m to several meters, and the thickness within 2m can reach 7m, showing the characteristics of ancient topography and geomorphology.
Seven. Liaodong-Jinan phosphorus accumulation zone
The above-mentioned specific phosphorite metallogenic structure-paleogeographic environment is not only unique to the phosphorite in Doushantuo and Meishucun periods in the upper Yangtze region, but also has similar characteristics to the phosphorite (phosphorite) in the early Proterozoic Jinping period in the southeast margin of North China platform. The early Proterozoic Jinping phosphorite period in the southeastern margin of North China Platform is one of the three major phosphorite periods in China, which stretches for 4000km along the eastern Hubei-northern Jiangsu-Liaodong-southern Jilin (and then extends eastward to Jin Ce, North Korea). The thickness of phosphorus-bearing rock series in eastern Hubei and southern Anhui is 850 ~ 1280m, that in Dawu area of eastern Hubei is 250~850m, that in Haizhou area of northern Jiangsu is 230~450m, that in sweet water in eastern Liaoning is 604m, and that in Hunjiang area of southern Jilin is 428.1m. This kind of structural uplift and depression, as well as topographic uplift and depression, is not only in the huge metallogenic belt of several hundred to several Qian Qian meters, but also in the mining area of several tens of kilometers or even hundreds of meters. For example, Pearl Gate Formation (equivalent to Jinping Formation) on the north bank of Hunjiang River in southern Jilin Province, there are six ancient topographic depressions within 30 kilometers from west to east along the mining area, forming six mining areas (Figure 3 14). The thickness of phosphorus-bearing rock series in Ganconggou is 30 ~ 40m, that in Heigou is 200m, that in Dadingzi-Pearl Gate is 240~260m, and that in Banshigou is 450~550m, which shows the difference of paleotopography and depression. Even in a certain phosphorite area, the control of paleotopographic depression on phosphorite deposition is often obvious. For example, the sweet water phosphate deposit in Liaodong is accumulated in a small depression with a length of 800 meters and a depth of 190 meters (Figure 3- 15), and it is determined to be a medium-sized deposit by exploration. This small depression is a depression of paleotopography, not a depression formed by synsedimentary subsidence.
Figure 3- 1 1 Early Cambrian topography and phosphorite sedimentary profile in eastern Yunnan
Horizontal scale1:2000000; Vertical ratio 1: 1000
(According to the Sixth Geological Team of Yunnan Geological Bureau 1977)
Figure 3- 12 Geological Schematic Diagram of Kunyang Ore Belt and Haikou Ore Belt
(According to Qian Zuoguo 198 1)
1- four yuan; 2- Tertiary (Paleogene, Neogene); 3- Jurassic; 4- Permian; 5- Carboniferous; 6- Devonian; 7-Dahai Section and Zhong Yi Village Section; 8- Xiaowaitou Mountain Section and Baiyan Section; 9- Qianzhusi Formation; 10-Canglangpu Formation; 1 1- light and shadow group; 12-Kunyang Group; 13- transgression direction
Figure 3- 13 Schematic Diagram of Mining Pit of Kunyang Phosphate Mine
(According to Qian Zuoguo 1984)
① siliceous dolomite; ② Gravel phosphorite; ③ granular phosphorite; ④ Quaternary system
Figure 3- 14 Regional Geological Map of Phosphate Mine on the North Bank of Hunjiang River in Jilin Province
Fig. 3- 15 Geological Profile of No.3 Orebody in the East of Sweet Water Phosphate Mine in Liaodong.
(According to He Shuhong et al., 1982)
1-carbonaceous slate and marble; 2- metamorphic gabbro; 3- Phosphate rock and phosphorite ore bodies; 4- dolomite marble; 5- metamorphic tuff; 6- Fault; 7- Drilling
The concept of continental margin and its tectonic palaeogeography is not fictitious, but summarized from a large number of practical data, and it is only an example to clarify the palaeogeographic characteristics of phosphorite metallogenic structure. In the following chapters, there are many contents related to and demonstrated the unique continental margin tectonic paleogeography, which may be common in the world industrial phosphorite. Mesozoic and Cenozoic phosphorites from Florida to southern Virginia on the east coast of the United States are deposited in the structural depressions on the flanks of uplift domes (James et al., 1980). M. S. Yusef( 1965) pointed out that groups of anticlines, synclines and non-structural depressions developed on the seabed when phosphorus-containing structures were deposited. Australian Middle Cambrian phosphorite is mainly deposited in the southwest of Precambrian old land, and Florida phosphorite is located in the southeast of Okala anticline. Wang Dongfang (1975) analyzed the paleogeography of phosphate rocks in the world and pointed out that the formation of specific deposits was mainly in secondary depressions or small synclines. According to the data analysis, Zhu Shangqing (1974) thinks that phosphorite often occurs in the submarine syncline depression (Figure 3- 16). O K muniyev (1979) thinks that due to the great fluidity of seawater, most sedimentary materials "gallop" across the continental shelf, and the accumulation on the continental shelf is mainly confined to depressions and basins on the seabed topography.
Figure 3- 16 Paleogeomorphological Map of Phosphate Deposit
(According to Zhu Shangqing 1974)