The tectonic position of the deposit belongs to the eastern part of Changshan-Zhuji Diwa Shengyuan sag of Zhejiang-Jiangxi Diwa System in the southeast diwa area of China in East Asia crust. According to the relationship between mineralization and tectonic-magmatic activation, it belongs to the tectonic-volcanic eruption activation area with strong volcanic activity. The deposit is one of the main volcanic uranium deposits in China, with concentrated ore bodies, shallow burial and rich ore.

Team 265 has done a lot of geological and research work on Xiong Jia deposit and accumulated rich geological data. Chen, Wang, Xie and Team 265 from Beijing Institute of Geology of the Nuclear Industry (1974 ~ 1976) formed a joint scientific research team to make a special study on the geological characteristics and controlling factors of the deposit. It is considered that Xiong Jia deposit is a low-temperature hydrothermal deposit closely related to volcanism. During the Sixth Five-Year Plan period, the East China Geological Bureau organized forces to conduct a multi-method and multi-disciplinary comprehensive study on the volcanic uranium metallogenic belt in Jiangxi-Hangzhou structure, and put forward the genetic viewpoint that the Xiong Jia deposit is superimposed after syngenetic deposition. The author of this book visited the deposit and studied the relevant geological data of the deposit. According to the diwa theory and its polygenetic compound metallogenic theory, Xiong Jia deposit is considered as a typical polygenetic compound uranium deposit.

2. Geological characteristics of the deposit and its multiple genetic evidence.

1) mining strata and ore-bearing surrounding rocks

The strata exposed in the mining area are Sinian to Cambrian, Triassic, Upper Jurassic and Lower Cretaceous, and the distribution of each stratum is shown in Figure 4-3. The Upper Jurassic is a set of pyroclastic sedimentary rocks composed of Daguding Formation, Ehuling Formation and Xishi Formation. See the stratigraphic table of Xiong Jia deposit for details (Table 4- 1).

Table 4- 1 Xiong Jia deposit stratigraphic table

(According to the data of Beijing Institute of Geology and 265 Geological Team of the Ministry of Nuclear Industry)

Uranium mineralization occurs in volcanic-sedimentary clastic rocks in the middle and lower part of Ehuling Formation. The main lithology of ore-bearing rocks is medium-coarse tuff and coarse-grained tuffaceous sandstone, which belongs to lake and river deposits. See Table 4-2 for chemical analysis of volcanic sedimentary rocks in the whole ore-bearing strata. The uranium abundance value of ore-bearing strata is 10 ~ 45g/t, which is rich in adsorbents and reductants such as phosphorus, carbon, clay and pyrite, and the upper and lower Th, P, Yb, Sr, Cu, Pb and Zn are higher, indicating that uranium has been enriched in sedimentary diagenesis. There are aquicludes above and below the ore-bearing strata, the upper part is carbonaceous shale, marl and siltstone above J3E2 ~ 4, the upper part is J3E2 ~ 5, and the lower part is siltstone of Daguding Formation. The ore-bearing strata have high permeability and brittleness. Compared with the upper and lower water-resisting layers, the chemical-mechanical-physical properties are quite different, which is easy to be destroyed by the later tectonic stress, and the formation of interlayer fracture zone and fracture zone is beneficial to the formation of uranium mineralization. At the same time, the ore-bearing strata are rich in reducing agents and adsorbents of uranium such as carbon, clay, phosphorus and pyrite, which provides good uranium enrichment conditions for hydrothermal mineralization in the later stage.

2) the structural form and ore-forming structure of the deposit

The area where the deposit is located has experienced a long geological development history and multi-stage and multi-stage activation, especially in the middle Yanshan period, the continental volcanic activity is extremely strong, forming a complex tectonic-volcanic eruption activation area. The mining area is located in a syncline basin inclined to the southwest on the edge of the fault zone in Sheng Yuan volcanic fault basin. The occurrence of strata in the basin is gentle, and the dip angle is generally 65438+05 ~ 200. There are no obvious large fold structures, but some small fold structures can be seen locally.

The fault structures in the mining area are well developed, mainly including three groups: east-west, northeast and northwest. The east-west fault is the largest, mainly distributed in the northern edge of the mining area and the eastern and southern parts of the mining area (Figure 4-4). The east-west fault in the northern margin is a gentle dip overthrust fault, which caused local inversion of late Jurassic strata in the basin margin. Two east-west faults (F2) in the east and two east-west faults (F 1) in the south controlled the distribution of the late Triassic faulted basins. NE-trending faults mainly include F4, F5 and F6 (Figure 4-4), which are a group of compression-torsion faults, strike 40 ~ 60, southeast or northwest, and dip angle 60 ~ 88, all of which are silicified and crushed out of the ground along F, and fault hydrothermal clay is widely developed. The NW-trending faults are a group of extensional or extensional shear faults, mainly F3. This group of faults is small in scale, generally tens of meters long and tens of centimeters wide to 1 meter.

Uranium mineralization is mainly distributed in two east-west fault-depression zones F 1 and F2 in Xiong Jia, which are controlled by east-west faults. The location of uranium ore body is controlled by horizon and some bedding fracture zones and fracture zones with gentle occurrence and small scale. Seen from the profile (Figure 4-5), these fracture zones or the positions where fracture zones occur are all the positions where the occurrence of ore-bearing strata changes. The occurrence change of ore-bearing strata is related to the NE-trending fault, which often occurs near this group of fault zones, and the intersection of bedding fracture zone or fracture zone and NE-trending fracture zone is usually the concentrated place of rich ore and large ore bodies.

3) Volcanic rocks and their relationship with uranium mineralization

Beijing Institute of Geology, Nuclear Industry (1977) divided the middle and late Jurassic volcanic activities in Sheng Yuan Basin into two major periods and six volcanic activities, namely Daguding period and Ehuling period. At the top of the drum, it is further subdivided into three volcanic activities. The first time was J3d2, where dozens of meters thick volcanic bombs were accumulated in lava bodies and lava bodies. The second time is J3D3 ~ 4 crystalline tuff, and the third time is J3d4 andesite magma eruption. During the Ehuling period, three volcanic activities were also divided. The first was ignimbrite in J3e2, the second was tuff and tuff in J3e3, and the third was ignimbrite or crystalline glass tuff in J3e4, which was characterized by the strongest for the first time.

Due to frequent eruption in the intense eruption stage, the volcanic rocks formed by one eruption and overflow are relatively thick, accompanied by more uranium sources, mineralizers and hydrothermal fluids. Therefore, the volcanic rocks formed in the middle and strong eruption stage of the eruption-sedimentary cycle have obvious control over uranium mineralization. J3E2 ~1and J3E2 ~ 3 tuffs in the occurrence horizon of uranium mineralization in Xiong Jia mining area are the products of the first strong eruption of volcanic activity during the Ehuling period. In addition, the intermittent time of volcanic eruption is also closely related to uranium mineralization. The volcanic rock series formed by intermittent eruption has many sedimentary rock interlayers, and the petrophysical and mechanical properties of sedimentary rock interlayers are obviously different from those of volcanic rocks. Under the action of late tectonic stress, fractured zones are easily formed in volcanic rocks, which provides favorable space for mineralization.

Figure 4-4 Geological Schematic Diagram of Xiong Jia Deposit

(Based on the data of Beijing Geological Research Institute of Nuclear Industry and Team 265)

1. Alluvial and slope deposits; 2. Siltstone and fine sandstone with tuff; 3. ignimbrite, tuff, tuff sandstone and siltstone; 4. Siltstone with tuff; 5. feldspar timely sandstone containing coal seam; 6. Shallow metamorphic sandstone, phyllite and schist; 7. biotite granite; 8. Compressive fracture; 9. Compression-shear fracture; 10. Tensile fracture; 1 1. Fracture of unknown nature

4) the shape of ore body and the change of surrounding rock near the mine

The shape of uranium ore bodies is mainly controlled by lithology and composition of host rocks, bedding fracture zone, fracture zone and NE shear layer fracture zone. The ore bodies are mainly lenticular, thick cake, pod and layered (Figure 4-6). All industrial mineralization occurs in the middle and lower part of Ehuling Formation, but it is not strictly limited by horizon, and cross-layer ore bodies often appear. Especially in the late stage of uranium-molybdenum mineralization transformation and superposition, the shape of ore body is more complicated, the thickness increases and the grade increases, and the highest grade reaches 65438 0.6%.

Figure 4-5 No.9 Profile of Xiong Jia Deposit

(According to the information of the 265th Brigade)

1. Carbonaceous shale and siltstone; 2. Sandstone; 3. Gravel and gravel sandstone; 4. Ore bodies; 5. Cluster sandstone; 6. Layer tuff; 7. Crystal flake-glass flake tuff; 8. Gravel tuffaceous sandstone

The surrounding rocks near the ore body are altered and developed, mainly including Dikai Petrochemical, hydromica, kaolinite, silicification, fluorite and carbonation. There are two stages of wall rock alteration related to uranium mineralization, namely early hydrothermal argillization and late silicification. Early hydrothermal clay rocks are characterized by large area, simple altered minerals and lax zoning. Clay formation is mainly produced in the interlayer fracture zone, fracture zone and permeable stratum of pyroclastic sedimentary rocks near the northeast or northwest fault in the middle and lower part of Ehuling Formation. The most characteristic mineral in the alteration zone is dickite, followed by chalcedony, hydromica, kaolinite and carbonate. According to the mineral assemblage, Beijing Institute of Geology of Nuclear Industry (1977) has divided the dickite-microsecond zone (central zone) and the hydromica-carbonate zone (peripheral zone). Uranium phosphorization is mainly distributed on the side between the above two zones near the dickite-microseismic zone (Figure 4-7), and thick and rich uranium phosphorite bodies are often formed, and the mineralization range is wider than the alteration bandwidth of hot liquid clay. Late silicification is carried out by using the channel and alteration space of early hydrothermal clay, which is strictly superimposed on early hydrothermal clay, but the scope is much smaller than that of clay. In some boreholes in the mineralized area, it can be seen that there is weak silicification in uranium phosphating, accompanied by the formation of purple fluorite and metal sulfide, which leads to the increase of uranium grade. On the other hand, in areas with strong late silicification (such as110 hole), it can be seen that the late silicification strongly transformed the early clay, and showed obvious overlapping zoning (Wang et al., 1980). The center of the alteration zone is the chronotropic zone, the two sides are the chronotropic-dikaishi zone, and the outer side is the water cloud mother zone. A large number of fluorite, molybdenite, pyrite and diaspore are produced in the Yingshi-dickite belt. The superposition of uranium-molybdenum mineralization related to late silicification transformed the early uranium-phosphorus mineralization. In the mineralization center, the grade of uranium reaches 1.06% ~ 1.6%. Therefore, rich and thick uranium-phosphorus-uranium-molybdenum mixed ore bodies are often formed in areas where silicification is strongly superimposed and reformed in the later stage (Figure 4-6).

Fig. 4-6 1 1 joint profile of Xiong Jia deposit.

(According to Beijing Institute of Geology, Ministry of Nuclear Industry)

1. siltstone; 2. Layer tuff and siltstone; 3. tuff of crystalline clastic layer; 4. Clustered siltstone; 5. Sandy shale and siltstone; 6. Contact boundary of stratigraphic unconformity; 7. Contact boundary of stratigraphic false integration; 8. Contact boundary of stratigraphic integration; 9. Industrial deposits; 10. Number of holes drilled; 1 1. Drilling depth (m)

5) Ore structure and composition

According to different ore types, the structure of ore has different characteristics. The structure of uranium ore is related to the structure of ore-bearing rocks. The tuff ore in the clastic layer has cemented structure and massive structure, and the phosphorite containing uranium appears in the form of cement, while the phosphorite in the rich ore exists in the form of sieve. In tuffaceous sandstone ore, collophanite is distributed in the ore in the form of gel blocks; In siltstone ore, collophanite distributes along micro-bedding, forming micro-bedding structure; However, vein-like and reticular vein-like structures often appear in the ore transformed by uranium and molybdenum mineralization in the later stage.

Figure 4-7 Schematic Diagram of Alteration Zoning of Surrounding Rock of Xiong Jia Deposit 1 1

(According to Beijing Institute of Geology, Ministry of Nuclear Industry)

1. Sandy shale; 2. Siltstone; 3. Sandstone siltstone interlayer; 4. Cluster sandstone; 5. Tufted sandstone; 6. tuff of crystalline clastic layer;

7. Layer tuff; 8. Tufted conglomerate; 9. Interlayer fracture zone; 10. Microseismic-Dikai stone belt; 1 1. hydromica carbonate belt;

12. hydromica; 13. Industrial ore bodies; 14. The second stage mineralized alteration zone

The material composition of ore varies with the age of its formation. See Table 4-3 for the chemical analysis results of two kinds of uranium mineralized ores. Early uranium deposits were mainly composed of quartz, dickite, collophanite, hydromica, calcite and pyrite. The late uranium-molybdenum mineralization is usually superimposed on the early uranium-phosphorus mineralization and belongs to the mixed uranium-phosphorus-molybdenum ore. Its mineral assemblage is complex. Besides collophanite, timely and dickite, there are a lot of fluorite, diaspore and metal mineralization. See Table 4-4 for details. The early uranium phosphorite is widely distributed, which is the product of the main mineralization period and main mineralization of the deposit. The late uranium molybdenum mineralization was superimposed on the early uranium phosphorization, forming a polygenetic compound uranium deposit with complex mineral composition and rich uranium grade. Uranium exists in different ore types in different forms. In uranium phosphate ore, uranium mainly exists in uranium-bearing collophane in the form of adsorption, accounting for about 90% of this kind of ore. In uranium-molybdenum ore, uranium mainly exists in collophanite, collophanite and fluorite in the form of adsorption or fine pitchblende.

Phosphorus exists in uranium ore in the form of collophanite. Collophanite is yellowish brown to grayish white, with gel-like structure, sometimes with clear dry cracks, in the form of blocks, parallel strips and screens. Collophanite is not an amorphous mineral, but a crystalline mineral with hexagonal columnar crystal apatite structure. This may indicate that collophanite was originally deposited in the form of amorphous calcium phosphate colloid, and then it began to aggregate and crystallize after dehydration and hardening, forming an aggregate of ultramicroscopic apatite crystals, but it still retained its colloidal structure and morphology. In uranium-molybdenum ore, phosphorus occurs in the form of coarse columnar apatite. It is the product of recrystallization and intense hydrothermal transformation after the formation of early collophanite.

Table 4-2 Total Chemical Analysis of Ore-hosting Rocks in Xiong Jia Deposit (%)

(According to Beijing Institute of Geology, Ministry of Nuclear Industry)

Table 4-3 Total Analysis of Ore Chemistry of Xiong Jia Deposit (%)

(According to Beijing Institute of Geology, Ministry of Nuclear Industry)

Table 4-4 Mineral Composition Table of Two Ore Types in the Deposit

According to Zhang Wanliang's research, there is an obvious positive correlation between uranium and phosphorus, and the correlation coefficient is 0.8 ~ 0.9. However, the relationship between uranium and phosphorus in uranium-molybdenum ore is not obvious, because the early uranium-bearing phosphorite was purified by recrystallization (Figure 4-8).

Figure 4-8 Relationship between Uranium and Phosphorus in Two Different Ores

(According to Zhang Wanliang)

1. phosphate uranium ore; 2. Uranium-molybdenum ore

6) Isotope Geology

The study of uranium and lead isotopes in uranium ore shows that there are two periods of uranium mineralization age (Beijing Third Hospital, 1977). The result of uranium-bearing collophanite determined by uranium-lead method is 127 ~ 136 Ma, which is equivalent to the lower limit age of early Cretaceous, indicating that uranium-phosphorization began after the formation of Ehuling Formation. Uranium-lead method is used to determine colloidal sulfur-molybdenum ore mineralized by uranium and molybdenum. The metallogenic age is 65438±006ma, which is equivalent to the formation of the Late Cretaceous. Combined with the mineral assemblage characteristics of the two metallogenic periods, it is considered that the formation of Xiong Jia deposit has experienced two obvious hydrothermal metallogenic periods, and the main metallogenic period is 136 ~ 127 Ma.

3. Analysis of deposit formation conditions

1) Source of ore-forming materials

Wang et al. (1980) think that the uranium source of the deposit mainly comes from some low-grade contemporaneous phosphorus uranium layers in ore-bearing rock series and relatively dispersed uranium in rocks. The special group of Ganhang District of East China Geological Bureau (1988) believes that uranium mainly comes from the ancient basement outside the deposit, especially the carbonaceous shale of the Lower Cambrian, with an average uranium content of 5 1g/t and a thickness of several tens of meters, which can provide more uranium after weathering. In view of the characteristics of multi-stage mineralization and multi-stage mineralization, we think that the uranium source of mineralization is multi-source. In the diagenetic stage of the Upper Jurassic, the erosion source area contained uranium from both Cambrian carbonaceous slate and Caledonian granite, as well as uranium from ejecta, which led to the diagenetic enrichment of uranium in pyroclastic sedimentary rocks of 10 ~ 45g/t, which provided sufficient uranium sources for supergene hydrothermal superimposed transformation and mineralization, and also had the original nature of multi-stage mineralization. In addition, in the subsequent hydrothermal mineralization process, some deep uranium sources and uranium dispersed in ore-bearing rock series will be brought, which will be superimposed and enriched in favorable metallogenic positions.

2) Physical and chemical conditions of mineralization

Judging from the alteration of the main mineralization period in the mineralization zone-uranium phosphating period, it can be considered that the main mineralization was carried out at medium and low temperatures. The temperature of purple fluorite in the late stage of uranium-molybdenum mineralization was measured by uniform method, and the result was 150 ~ 190℃. In the strongly silicified zone of the mineralization center, there is diaspore formed at medium and high temperature. In addition, hydrothermal clay alteration and uranium-molybdenum mineralization occurred at the same time, indicating that the hydrothermal activity of uranium-molybdenum mineralization was formed in the late stage of Xiongjia deposit and experienced an evolution process from medium-high temperature to medium-low temperature. Mineralization mainly occurs in the bedding fracture zone of tuff with gentle occurrence. According to the profile analysis of the ore body, the overlying strata are not thick, the cumulative thickness is less than 350 ~ 400 m, and the mineral assemblage is mainly low-temperature It can be inferred that the depth of the main metallogenic period is medium-shallow and the metallogenic pressure is medium-low.

3) metallogenic space and dynamic conditions

The spatial conditions of the deposit are very favorable, which is manifested in the close proximity to the favorable tectonic geochemical interface and rock geochemical interface on the metallogenic profile. From the lithology, composition and profile distribution of uranium mineralization of ore-bearing rock series, it can be seen that the ore bodies are mainly produced in medium-coarse tuff and coarse-grained tuffaceous sandstone in the middle and lower part of Ehuling Formation, belonging to brittle rock strata with good water permeability, and the upper and lower rock strata are relatively flexible water-resisting layers. Because of their different physical and mechanical properties, they are easy to fracture under the action of tectonic stress, forming interlayer fracture zone, causing the development of various structural fractures in ore-bearing rock series, thus forming favorable mineralization.

The activation of Yanshanian tectonic magma provided hydrothermal and driving conditions for uranium mineralization. The upper Jurassic in Sheng Yuan volcanic basin is divided into two periods and six volcanisms, and Yanshanian biotite granite is distributed in the east of the mining area, which indicates that the crust of the mining area was in a state of intense activation in Yanshan period, providing sufficient hydrothermal solution and power source for uranium mineralization, so that uranium in the pre-existing strata is activated, forming ore bodies, then activated, enriched and precipitated, forming large-scale uranium deposits.

4. Mineralization evolution

1) Metallogenic tectonic evolution

The tectonic evolution of metallogenic areas and regions has experienced three tectonic stages: geosyncline, platform and diwa. During the sedimentary period of geosyncline stage, a set of clastic rocks and marine volcanic rocks characterized by flysch rhythm from Neoproterozoic to Early Paleozoic were formed. The Caledonian tectonic movement at the end of Middle Silurian made the geosyncline return, which made the pre-existing strata generally undergo shallow regional metamorphism, accompanied by the intrusion of Caledonian granitoids. There is no platform structure in the mining area, but from Devonian to Middle Triassic, continental clastic rocks were deposited in the early stage, and a set of shallow-sea carbonate rocks with large thickness was formed in the middle and late stage. Finally, the coal-bearing strata between land and sea are deposited to form the platform structure layer.

The late Triassic was diwa stage, and a set of continental coal-bearing clastic rocks was deposited in the late Triassic. A set of volcanic sedimentary clastic rocks was formed in the late Jurassic, and thick red beds were deposited in the early Cretaceous, which filled the Sheng Yuan volcanic basin and formed diwa structural layer. The main feature of this structural layer is the development of a set of upper Jurassic acid pyroclastic sedimentary rocks, which cover the geosyncline structural layer in an unconformity form. During the intense diwa stage (middle and late Yanshanian movement), there were Yanshanian biotite granite intrusion and large-scale intermediate-acid volcanic activity in the area, indicating that tectonic-magmatic activation developed strongly.

2) Evolution of uranium mineralization

According to the geological characteristics of Xiong Jia deposit and the brief history of mining area and regional geological evolution, the formation of the deposit has experienced the initial enrichment of uranium in bedrock of volcanic basin, the diagenetic enrichment of uranium in diwa stage, the transformation of diwa stage and hydrothermal mineralization in superimposed enrichment stage.

Preliminary enrichment of uranium in basement rocks of volcanic basin. In the geosyncline structural layer, there is a set of black shale series in the Cambrian strata, and the uranium abundance value is relatively high, with an average of 5 1g/t, which becomes the original enrichment layer in the sedimentary diagenetic stage of the geosyncline and provides an important uranium source for subsequent mineralization.

Enrichment of uranium in diwa stage in sedimentary-diagenetic stage. There are rocks or rock masses with high uranium content in the shallow metamorphic rock series and Caledonian granite bodies formed in the geosyncline period in and around the mining area. Under the strong tectonic-magmatic activation in the diwa period, uranium-rich erosion source areas with strong geomorphologic contrast were formed. At the same time, a large-scale volcanic eruption occurred in the Sheng Yuan fault basin, forming adsorbents and reductants rich in carbon, clay, phosphorus and pyrite, and forming ore-bearing beds (10 ~ 45g/t) rich in uranium diagenesis in the middle and lower parts of the Ehuling Formation, with a cumulative thickness of 80 ~100 m. Therefore, the volcanoes in the middle and lower parts of the Ehuling Formation,

Hydrothermal mineralization in diwa stage reconstruction and superimposed enrichment stage is a series of hydrothermal mineralization under the influence of tectonic-magmatic activation in the middle and late diwa stage after uranium enrichment in basement rocks of volcanic basin and uranium diagenesis in volcanic-sedimentary rocks of basin cover rocks. According to the uranium age, the symbiotic combination of ores and minerals, combined with the analysis of geological characteristics and metallogenic conditions, the hydrothermal mineralization period of Xiong Jia deposit can be divided into two metallogenic generations, namely, the middle-low temperature volcanic hydrothermal mineralization in the middle Yanshanian period and the hydrothermal superimposed enrichment ore in the late Yanshanian period. Volcanic hydrothermal mineralization is the most important uranium mineralization. It is a mixed hydrothermal solution dominated by volcanic hydrothermal solution and mixed with ancient surface groundwater. Under the action of tectonic driving force, it rose to the favorable tectonic-lithologic position in the middle and lower part of Ehuling Formation in the mining area for mineralization, represented by uranium phosphorization construction, and the ore age was 127 ~ 136 Ma. In the late Yanshanian period, hydrothermal solution superimposed on enriched ore, represented by uranium-molybdenum mineralization, with ore age of 106Ma. Uranium-molybdenum mineralization is usually only superimposed on early uranium-phosphorus mineralization, which makes the ore body rich and thick. Judging from the mineral assemblage of the mineralization center (Table 4-4), there is diaspore formed at medium and high temperature, which indicates that the initial temperature of the ore-forming solution is quite high. The abundant occurrence of fluorite in ore and the development of collophane indicate that the ore-bearing hydrothermal solution may mainly come from the deep. We tend to think that the uranium-molybdenum mineralization in the late Yanshan period is related to the abnormal mantle in this area (the study area is located in the composite part of the Ganhang depression belt and Wuyi uplift belt), and the ore-forming fluids rich in F and ∑CO: differentiated in the late Early Cretaceous. This ore-forming fluid usually inherits the ascending channel of existing volcanic magma and superimposes mineralization in volcanic basins.

To sum up, the formation of Xiong Jia deposit is the result of multi-stage structure, multiple uranium sources and multiple uranium mineralization. We believe that the genesis of Xiong Jia deposit belongs to polygenetic compound uranium deposit, which has the characteristics of multi-source, multi-stage, multi-genesis and accumulation, with volcanic hydrothermal mineralization as the main factor.