Zhajistan uranium deposit, Xinjiang

Liu Junping Kang Yong served as the king of the ship, Mao Mao, Qiu Yubo and Hao Yize.

(Nuclear Industry 2 16 Brigade, Urumqi, Xinjiang 8300 1 1)

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Structural diagram of Zajistan section in the southern margin of Yili basin.

1-Cretaceous; 2- Shuixigou Group of Middle and Lower Jurassic; 3- Middle Carboniferous Dongtujinhe Formation; 4— Formation unconformity line; 5— Coal seams and sintered rocks; 6- Reverse Fault

2.3 Hydrogeological characteristics

2.3. 1 groundwater recharge conditions

The Paleozoic erosion source area and sand production area on the northern slope of Chabuchar Mountain are groundwater recharge areas of Jurassic Shuixigou aquifer group in the mining area, and the recharge forms mainly include surface water recharge, atmospheric precipitation recharge, Quaternary phreatic water recharge and bedrock fissure water recharge. The Jurassic in the mining area gently dips to the northeast with an inclination angle of 3 ~ 8, and is in unconformity contact with the Quaternary at a micro angle. The opening of Jurassic aquifer group is in direct contact with the bottom of phreatic aquifer, which provides a seepage channel for phreatic recharge. Palaeozoic bedrock fissure water is another source of groundwater recharge in Jurassic aquifer group by infiltrating into Quaternary groundwater from the piedmont.

2.3.2 Groundwater Runoff Conditions

The east boundary of the deposit is F3 water-blocking fault, and the groundwater flow direction is between 355 and 27 (Figure 3). The buried depth of water level is between 134.58 ~ 233.7 1m (table 1), and the head height is less than 50m, which indicates that the bearing capacity of this section is weak, the permeability coefficient is between 0. 10 ~ 0.57m/d, the hydraulic gradient is 0.044, and the groundwater. Among them, the ore bodies of lines 20 ~ 36 and 56 belong to the pressure-bearing area, and most of the ore bodies of lines 40 ~ 44 and 48 are in the non-pressure-bearing area.

2.3.3 Groundwater discharge conditions

According to remote sensing interpretation (Chen Jianchang et al., 1995), there is a hidden fault in the north of Zajistan village, with underground springs exposed on both sides, and the H2S content in the water is high, which constitutes a local drainage source of groundwater in the mining area [7].

Fig. 3 Hydrodynamic field analysis of the western section of Zajistan uranium deposit.

1-the contour line of groundwater level elevation and its value (m); 2— isoline and numerical value (m) of roof elevation of ore-bearing aquifer; 3- the boundary between the confined area and the unconfined area; 4- uranium ore body; 5- groundwater flow direction; 6— Exploration line and serial number (ore bodies of lines 20 ~ 36 and 56 belong to pressure-bearing areas, and ore bodies of lines 40 ~ 44 and 48 are mostly in non-pressure-bearing areas).

Table 1 Hydrogeological Parameters of Ore-bearing Aquifer in Zajistan Deposit

2.3.4 hydrochemical characteristics of groundwater

The types of groundwater are sodium bicarbonate, calcium bicarbonate, calcium bicarbonate, calcium bicarbonate, calcium chloride and calcium bicarbonate (Table 2), the water temperature is 1 1 ~ 15℃, and the pH value U in the water is 7.00×10-7 ~ 2.93. ..

Table 2 hydrochemical parameters of ore-bearing aquifer in Zajistan uranium deposit

sequential

2.4 Interlayer Oxidation and Uranium Ore Body

2.4. 1 Spatial distribution characteristics

There are three types of uranium mineralization in Zajistan uranium deposit: sandstone type, mudstone type and coal-rock type, and sandstone type uranium mineralization is absolutely dominant in scale. The occurrence horizon of sandstone-type uranium mineralization can be divided into V 1 and sub-cycle, and ore-bearing sand body is the main ore-bearing horizon of industrial uranium mineralization. The spatial distribution of ore bodies is closely related to the front line of interlayer oxidation zone. The front of interlayer oxidation zone and uranium ore body are "harbor". Due to the barrier of muddy interlayer in the middle of sand body, interlayer oxidation zone is divided into upper and lower layers in the middle of mining area. The lower layer extends far along the dip and is 2000 ~ 2500 meters wide. The front is located within 500 ~ 1600 m north of the upper front. The upper layer is 800 ~ 1200m wide, and the industrial uranium mineralization in the upper and lower layers is well controlled, so two industrial uranium belts are formed in the south and north of the mining area, and the off-balance-sheet ore bodies are distributed at the edge of industrial ore bodies (occasionally inside) (Figure 4) [8 ~ 10].

Plane distribution map of the fifth cycle ore body of Zajistan uranium deposit.

1- exploration line and borehole; 2- Industrial uranium ore bodies; 3-v1or industrial uranium ore body; 4. Off-balance-sheet uranium ore bodies; 5— the front of interlayer oxidation zone; Front line of 6-B interlayer oxidation zone; 7- Reverse failure; 8- Strata Boundary/Coal Seam

2.4.2 Zoning characteristics of interlayer oxidation zone

Zajistan deposit has the general characteristics of sandstone-type uranium deposits in interlayer oxidation zone. According to the geochemical properties and the occurrence space of uranium mineralization, the interlayer oxidation zone in the mining area can be divided into oxidation zone, transition zone and original rock zone. Among them, the oxidation zone can be divided into strong oxidation zone, medium oxidation zone and weak oxidation zone; The transition zone can be divided into fading sub-zone (acidification front) and uranium sub-zone; According to uranium grade, it can be further divided into ore-rich subregion, general ore subregion, poor ore subregion and uranium-bearing interstitial water subregion [1 1]. The characteristics of each partition are shown in Table 3.

Table 3 Zoning of interlayer oxidation zone and its material composition characteristics

The major elements, organic matter, uranium and its associated elements of rocks in each sub-zone of interlayer oxidation zone show a certain change law: Fe2O3 gradually decreases from oxidation zone to primary rock zone, and the reducing agent content in transition zone is high, which makes some iron ions in water reduce and precipitate, and the FeO content in transition zone is the highest [1 1]. The ferrous content in the oxidation zone is 0.07%, the reduction zone is 0.35%, and the transition zone is 0.62%. The trivalent iron content in the oxidation zone is 0.97%, the reduction zone is 0.65%, and the transition zone is the lowest, which is 0.5 1%. The contents of organic carbon and sulfide gradually increase from oxidation zone to primary rock zone, and the transition zone has the highest content and the largest coefficient of variation, showing the characteristics of enrichment and uneven distribution. The reduction zone is slightly reduced, relatively speaking, their content in the oxidation zone is the lowest, and the coefficient of variation is the smallest; The organic carbon content in the transition zone is 8.2 times that of the oxidation zone, 1.4 times that of the reduction zone, and the sulfide content in the transition zone is 3.4 times that of the oxidation zone and 1.2 times that of the reduction zone (Figure 5).

2.4.3 characteristics of ore bodies

Influenced by the exploration scope at that time and the lack of understanding of the characteristics of uranium mineralization, the basic structural unit factors were not considered in the delineation of the Zajistan deposit scope, and the deposit exploration submission scope crossed the Zajistan River fault (F3) and entered the scope of the Mengqigur deposit. Taking the Zajistan River fault as the boundary, the main ore body of Zajistan deposit in the north of the fault is about 3500m long, 50-300m wide, with a buried depth of170.35-308m and an elevation of1028-1130m, and the overall buried depth of the ore body is shallow in the south. The occurrence of ore body is consistent with the ore-bearing sand body, and the dip angle is 2 ~ 9.

The ore bodies are rolled and plate-shaped, and a few are lenticular. Typical rolled ore bodies are mainly distributed near the line 16, with a head length of 50 ~ 100 m, a thickness of 5.0 ~1.2 m, a wing length of 50 ~ 200 m and a thickness of1.9 ~ 3.9 m; Plate orebodies are mainly distributed in most sections of 12 line, 0 line and Zanan line. The thickness of the ore body is generally 1.0~4.0m ~ 4.0m, and the extension length on the profile is 150 ~ 450m. Lenticular ore bodies are distributed on the N7 line, which are "isolated islands" in plane, and most of them are produced by single hole. Generally, the length is less than 100m, and the thickness is 2.7 ~ 5.5m. The ore body will be extinguished soon (Figure 6).

Fig. 5 Variation relationship of uranium and associated elements in each subzone of interlayer oxidation zone

Fig. 6 Typical ore body shape in Zajistan mining area.

The thickness of ore bodies ranges from 0.90 to14.75m, with an average of 5.13m and a coefficient of variation of 56. 1 1%. The variation range of single project grade is 0.0 106% ~ 0.3272%, with an average of 0.0379% and a coefficient of variation of 1 14.64%. The uranium content per square meter of a single project is generally 1.00 ~ 37.73 kg/m2, with an average of 4.00kg/m2 and a coefficient of variation of 1 12.02%.

2.5 ore characteristics

The natural type of ore is loose sandstone uranium deposit in interlayer oxidation zone. The minerals in the ore are mainly chronological, accounting for 69. 1% of the total minerals, clay minerals accounting for 20.4%, potash feldspar accounting for 9.7%, and other components are albite, carbonate, hematite and pyrite. The average content is less than 0.5%. Clay minerals include kaolinite, chlorite, illite and illite-montmorillonite mixture, with kaolinite accounting for 53.6% of the total clay. Followed by illite, accounting for 23.2%; The mixed layer of illite and montmorillonite accounts for 14.2%, chlorite accounts for 8.8% and does not contain montmorillonite.

Heavy sand analysis shows that the ore contains trace heavy minerals, such as anatase, ilmenite, pyrrhotite, zircon, spinel and garnet chalcopyrite. In addition to mineral components, the ore also contains a small amount of organic matter, mainly carbonized plant debris, followed by humus, humic acid, H2S, CH4 and other gases formed by decomposition of plant debris. The average content of organic carbon in ore is 0.35%.

Uranium in ore mainly exists in two forms: independent uranium ore and dispersed adsorption state, and a small amount exists in other minerals in the form of isomorphism. Uranium minerals mainly exist in the form of pitchblende, which accounts for more than 80% of the samples. There are a small amount of ilmenite, ilmenite-like uranium ore and uranium ore.

2.6 Associated minerals

The analysis results of associated elements show that the associated elements in the ore mainly include selenium, molybdenum, rare earth, germanium, gallium and vanadium. The overall trend is to increase from oxidation zone to transition zone, but there are differences in enrichment sites. The mineralization or anomaly of molybdenum and vanadium occurs in the reduction zone near the uranium ore belt. Rare earths are distributed in the uranium ore belt, which is basically consistent with the spatial position of uranium mineralization; Selenium mineralization occurs in the front of interlayer oxidation zone, close to weak oxidation zone; Ga mineralization is widely distributed in the whole uranium ore belt (Figure 7).

Fig. 7 Comparison curves of U with Se, Mo, Re and Ga on borehole profile 0 16 14.

1-yellow gravelly coarse sandstone; 2— Gray gravelly coarse sandstone; 3— Yellow medium-fine sandstone; 4— Gray medium-fine sandstone; 5-u element; 6-Se element; 7-Mo element; 8-Re element; 9- gallium element

2.7 metallogenic age and metallogenic period

The No.216 Brigade of the Nuclear Industry cooperated with Nanjing University to study the ore composition and metallogenic age, and determined that the metallogenic age of sandstone uranium deposit was (11.7 0.3) Ma (whole rock U-Pb age, and the uranium content in the sample reached 2.7 1% after separation and enrichment).

The No.203 Institute of Nuclear Industry conducted a whole-rock U-Pb isochron dating of the rich ore in Zajistan deposit, and the result was 8Ma.

At the same time, Qin Mingkuan of Beijing Institute of Nuclear Industry Geology determined the whole rock uranium and lead age of the ore in Zhajistan deposit, Taihe, Kutter. The age of uranium mineralization ranges from 158Ma (equivalent to JBOY3) to 0.7Ma, and * * has six groups of ages, of which 156Ma is the mudstone alteration age (phreatic oxidation age). 66Ma, 30 ~ 51ma and 25 ~15ma are the sandstone alteration ages. The ore ages are concentrated in 12 ~ 2ma (Pliocene) and 2 ~ 0.7ma (transformation and enrichment period).

The results of the above three units are basically the same, belonging to Pliocene. The interlayer oxidation zone in Zajistan profile developed in many stages, and the mineralization was reformed many times and gradually enriched.

3 Main achievements and innovations

3. 1 main achievements

1) basically found out the characteristics of uranium mineralization, ore composition and main ore-controlling factors; The geophysical characteristics of the deposit and the equilibrium failure law of uranium, radium and radium radon in the ore body are found out in detail. The proven reserves of in-situ leachable sandstone-type uranium resources have reached medium scale.

2) The structural and stratigraphic characteristics of the west side of Zajistan River Fault (F3) have been basically ascertained, and the spatial distribution, formation time and activity form of Zajistan River Fault (F3) have been clearly understood. For the first time, the metallogenic geological conditions in the east of the Zajistan River fault (Mengqi Gul area) have been proved, which provides clues for prospecting and exploration in Mengqi Gul area.

3) Find out the hydrogeological structure of the deposit and the structure, distribution, scale and buried depth of the ore-bearing aquifer through the hydrogeological hole pumping (injection) test and preliminary data sorting and research. The hydrogeological and hydrogeochemical parameters of the ore-bearing aquifer are obtained, which provides an important basis for the feasibility evaluation of in-situ leaching mining.

3.2 Main innovation points

3.2. 1 Deepening the innovation of metallogenic theory

As the second deposit discovered and explored in the southern margin of Yili basin, the project team initially realized the difference between the main controlling factors and the secondary factors in the metallogenic factors of Kujiertai sandstone-type uranium deposit in the southern margin of Yili basin. In this paper, the simplified ore-controlling factors and genesis of Zajistan deposit are put forward, and it is considered that:

Lithofacies and lithology are the basic factors. The ore-bearing sand body of Zajistan uranium deposit is distributary channel deposit in the transition stage from fan delta plain to front edge, which has ideal sand body structure, physical and mechanical properties and reductant content, and is a favorable facies area for sandstone-type uranium mineralization. Lithologically, the clastic materials of ore-bearing main lithic sandstone and feldspar lithic sandstone mainly come from acid volcanic rocks, pyroclastic rocks and granite in the erosion source area, which have high uranium background value.

2) Interlayer oxidation zone is the dominant factor of mineralization. When the interlayer oxidation zone develops in the primary reduced sand body, it not only causes the rocks to undergo different degrees of oxidation alteration, but also causes a series of changes in the geochemical environment (pH value and Eh value) of the rocks, forming an oxidation-reduction geochemical barrier at the front of the oxidation zone. Uranium is activated in strongly altered rocks and then enriched on geochemical barriers through migration and precipitation. The output of uranium ore body is strictly controlled by interlayer oxidation zone, and the ore body occurs in oxidation-reduction transition zone.

3) Pyrite and organic matter are important factors in precipitation of uranium. With the development of interlayer oxidation zone and pyrite oxidation, H+ dissociated from H2SO4 can reduce the pH value of environmental medium, which is beneficial to uranium precipitation. With the participation of microorganisms, the slightly metamorphic plant debris that can reduce uranium produces hydrocarbon gases such as H2S and CH4 through a series of decomposition reactions, which leads to a sharp decline in the Eh value around organic matter, which makes the medium change from alkaline to neutral, and finally reduces and precipitates U6+ in the aqueous solution.

4) Fracture controls uranium mineralization. Although the research and exploration on the east side of Zajistan River Fault (F3) is low, and the project team doesn't fully understand the metallogenic conditions in Mengqigur area on the east side of the fault, the project team has realized that the development of Zhahe Fault is earlier than the main metallogenic period, and its own hydrodynamic conditions and interlayer oxidation zones are formed on the east and west sides of the fault. The scale, shape and location of interlayer oxidation zone and uranium ore body on both sides of the fault are completely different.

5) Modern inherited water system is of positive significance to mineralization. The Zajistan River developed in the piedmont of the mining area is a perennial river with a modern average flow of 33,000m3/d, and its riverbed has been swinging along the 20 ~ 0 line of the mining area since the Quaternary, which has a positive effect on the recharge of groundwater, the full development of interlayer oxidation zone and the superposition and enrichment of uranium mineralization in the mining area.

3.2.2 Innovation of exploration methods

For the first time, the patented technology of "a redox potential logging tool for uranium reduction, precipitation and mineralization determination" was applied to successfully predict the change trend of interlayer oxidation zone, provide a basis for uranium ore body positioning, accurately predict and narrow the target area, locate the spatial position of uranium ore body and improve the prospecting efficiency.

3.2.3 Innovation of in-situ leaching mining method

During the general survey in Zajistan area, it was found that the groundwater level between the 20 ~ 70 exploration lines was deep, and the groundwater in the ore-bearing aquifer was in a pressureless state, so the conventional in-situ leaching mining technology could not be adopted.

In 2000, Xinjiang CNNC Tianshan Uranium Industry Co., Ltd. officially started the in-situ leaching mining technology test of Zajistan deposit. In the mining test stage, a lot of research work has been done on the full utilization of uranium resources, especially in the 36 ~ 58 line of the deposit, through artificial intervention of the groundwater level of the ore-bearing aquifer, the pressure-bearing nature of groundwater has been changed. By artificially raising and controlling the groundwater level, the in-situ leaching uranium ore body in the unconfined area of groundwater was successfully mined.

4 Development and utilization status

During the period of 1995, Xinjiang Mining and Metallurgy Bureau of the Nuclear Industry and the Sixth Research Institute of the Nuclear Industry conducted field condition tests and indoor leaching tests on the exploration line N0 in Zhanan (volkov geological enterprises participated in the indoor leaching tests). The results show that the leaching rate of uranium, uranium concentration in leaching solution, single hole injection and liquid extraction by acid leaching method are ideal.

From 2000 to 2003, CNNC Tianshan Uranium Industry Co., Ltd. carried out in-situ leaching feasibility test and industrial test on 16 exploration line, and achieved success.

Since 2002, 9 mining areas have been developed in the deposit 16 ~ 7 line.

5 concluding remarks

Zhajistan deposit is the second in-situ leachable sandstone-type uranium deposit found in the uranium metallogenic belt in the southern margin of Yili basin, with a medium scale. Through the exploration and study of Kujiertai deposit, the first sandstone-type uranium deposit in China, Chinese sandstone-type uranium geologists have a preliminary understanding and understanding of the theory of in-situ leachable sandstone-type uranium deposits. The exploration of Zajistan deposit is not only a successful application of sandstone-type uranium deposit theory, but also a process of deepening theoretical understanding. In the process of deposit exploration, the project team pays attention to simplifying the ore-controlling factors and distinguishing the primary and secondary relations of each ore-forming factor. Through the comparative study with Kujiertai deposit, the similarities and differences between the two deposits are preliminarily revealed, and the theory of sandstone-type uranium deposits is further summarized and deepened, which is of great significance to uranium prospecting and exploration in Yili Basin.

With the success of in-situ leaching test between Zajistan deposit 16 ~ 70 exploration lines, the exploration work of 20 13 Zajistan deposit 18 ~ 70 began. Through exploration, the ore body extends along the line of 58 ~ 70, and there is a trend of extending to the northwest. Combined with the exploration results of Wu Curzi deposit in the northwest of Zajistan deposit and its periphery, it is considered that the vast area between Zajistan deposit and Wu Curzi deposit has certain metallogenic potential.

refer to

[1] Zhang Jindai, Xu Gaozhong, et al. Indicative significance of six new sandstone-type uranium deposits in northern China to uranium resource potential [J]. Geology of China, 20 10/0,37 (5):1434-1449.

Wang Baoqun. Major breakthrough of in-situ leachable sandstone-type uranium deposits in the southern margin of Yili Basin [J]. Geology of Xinjiang, 2002,20 (2):106-109.

[3] Wang Cheng, Wang Baoqun. Summary of the project "Exploration and resource evaluation of in-situ leachable sandstone-type uranium deposits in the southern margin of Yili Basin, Xinjiang" [J]. Academic seminar to commemorate the 20th anniversary of Li Siguang's birth14 and the 20th anniversary of Li Siguang Geological Science Prize, 2009,308-314.

Li Hezhe, Li Yanlong, A, et al. Evaluation of uranium mineralization prospect in the southern margin of Yili Basin [R]. Urumqi: No.216 Nuclear Industry Brigade, 1995.

Ken Wang. Formation of Xinjiang orogenic basin and sandstone-type uranium mineralization [J]. Geology of Xinjiang, 2002,20 (2):110/4.

Ken Wang, Wang Cheng. Some thoughts on uranium prospecting in the junction of Tianshan orogenic belt and basin [J]. Proceedings of the 9th National Conference on Mineral Deposits, 2008,21-212.

Huang Xianfang, Chang, et al. Remote sensing exploration technology of sandstone uranium deposits in interlayer oxidation zone of Yili Basin [M]. Beijing: Atomic Energy Press, 1999.

Wang Zhengqi, et al. General Survey Report of Uranium Mine on Line 70 ~ 16 in Zajistan Area, Chabuchar County, Xinjiang [R]. Urumqi: No.216 Nuclear Industry Brigade, 1998.

Yin Jianhua, Chen Fenxiong, et al. Geological report on exploration of Zajistan uranium deposit1line 6 ~ 7 in Chabuchar County, Xinjiang [R]. Urumqi: No.216 Nuclear Industry Brigade, 2003.

[10] Wang Maomao, Kang Yong, et al. Geological Report of Deep Exploration Resource Project (Zajistan Uranium Mine Line 0 18 ~ 070) in Yili Demonstration Base of Xinjiang [R]. Urumqi: 2nd16 Brigade of Nuclear Industry, 20 13.

Huang Shijie. Prospecting criteria for sandstone-type uranium deposits in interlayer oxidation zone [J]. Uranium Geology, 1994, 10 (1): 6-3.

Significant progress and breakthrough in uranium exploration in China —— Examples of newly discovered and proven uranium deposits since the new century.

[Author Brief Introduction] Liu Junping, male, born in 1970, is a senior engineer. 1993 graduated from the Department of Geology of East China Institute of Geology (now East China University of Science and Technology) with a major in uranium exploration. From 20 13 to now, he is the captain of the first team of the 216 th brigade of the nuclear industry, engaged in uranium geological exploration and scientific research. Won the second prize of national defense science and technology 1, the third prize 1, "Top Ten Geological Prospecting Achievements in China" 1, the second prize of scientific and technological progress of China National Nuclear Corporation 1, and the second prize of geological survey achievements of China 1.