Hengfeng Ge Yuan Tantalum and Niobium Ore Field

The ore field is located in Huai Yu sag, which is more than kilometers away from the structural ophiolite melange belt 10 in northeast Jiangxi. The exposed strata mainly include South China-Sinian shallow metamorphic sandstone, phyllite, carbonaceous slate and impure limestone, Cambrian shale and calcareous shale mixed with marl and nodular limestone, Triassic continental conglomerate, glutenite, sandstone and Jurassic volcanic lava. The direction of regional tectonic line is ne and NE, and the secondary faults are mainly divided into four groups: NE, NE, NE and NW. The Yanshanian Lingshan complex granite body is exposed in the middle of the ore field, with an oval plane and a long axis nearly east-west, covering an area of 200km2. According to the analysis and calculation of geophysical data, the lower part of the rock mass extends gently from east to west, showing a huge lenticular shape, and the floor disappears below the surface 7km. The isotopic age of the main rock mass is 140 ~ 107 Ma, which is the product of the late Yanshan period. From morning till night, the sequence is gray medium-grained amphibole biotite monzodiorite → gray fine-grained amphibole biotite monzogranite → geode alkali feldspar granite vein → gray fine-grained amphibole biotite syenite → fleshy red medium-coarse biotite alkali feldspar granite, with huge geodes, which are distributed from the edge to the middle from morning till night. The rock mass contains more granular diorite deep-source inclusions and surrounding rock inclusions. According to Li Changnian's research, it is considered that it has the characteristics of basaltic magma jet mixing. Vein-like irregular albite granite (γ A Ⅰ) in zinc-blende diorite is developed in the contact zone inside and outside the rock mass, with high niobium content and isotopic age of 127 ~ 109 Ma. In the middle of the main rock mass, there are fine-grained porphyritic granitoids in the late Yanshanian along the NE-trending fault zone, and the rock wall is beaded, with isotopic age of 105 ~ 95 Ma.

In Songshugang area, 2 kilometers west of Lingshan rock mass, a concealed granite strain was found at a depth of 200 meters. Its lithology is mainly medium-fine grained zinc-aluminum garnet albite granite (γ A Ⅱ), with isotopic age of 1 16 ~ 109 Ma, with strong alteration, local crystal cave structure and niobium, tantalum, tungsten, tin and molybdenum mineralization. In addition, diorite vein, granite vein, granite porphyry vein, fine-grained vein and pegmatite vein are also developed in the ore field, among which granite pegmatite vein is distributed in the inner and outer contact zone of Lingshan rock mass, and Huangshan section is the most developed (Figure 4-45).

From the petrochemical composition of different intrusions such as Lingshan, Huangshan and Songshugang (Table 4-23), there is an evolution trend from biotite granite in early emplacement to albite granite in metallogenic period, and from acidic granite slurry to alkaline granite slurry. The chemical composition of rock mass is converted into standard mineral molecules by CIPW method, and then projected on the Or-Ab-Q classification diagram (Figure 4-46). It can be seen that Songshugang concealed granite, Huangshan niobium-bearing granite and Lingshan rock mass have obvious stages in diagenetic time, but they show inheritance in petrochemical composition. Lingshan rock mass consists of sodalite granite and sodalite granite, while Songshugang and Huangshan rock mass consists of sodalite granite and sodalite.

Figure 4-45 Geological Schematic Diagram of Lingshan Complex Rock Mass

Table 4-23 Comparison of Chemical Composition (%) of Granite between China and Ore Field

Figure 4-46 Granite Rock Types in Ore Field (Zhang Jintong et al., 1985)

Isotopic test results of Lingshan complex granite body: δ34S‰ is +0.6 ~ 6.3, δ 18O‰ is +7.2 ~ 9.9, δD‰ is -83.64 ~- 120.33, and the initial value of 87Sr/86Sr is 0.7024. The content of rare earth element ∑REE is 60.6/kloc-0 /×10-6 ~ 513.6×10-6, and the average value of ∑Ce/∑Y is 4.2 1, which is mainly light rare earth. From the early biotite granite to the late alkali-feldspar granite, the total amount of rare earths has been greatly reduced.

According to the above petrochemistry analysis, some macroscopic features of petrochemistry and petrology (such as ringspot structure, miarolitic structure, deep inclusions, etc. ), Lingshan (including Huangshan and Songshugang) complex granite body is not only different from S-type granite remelted in continental crust, but also obviously different from I-type granite mixed with crust and mantle, but has the main characteristics of A-type granite (Qi Jianzhong, 2000).

In the ore field, there are more than ten large and small endogenetic deposits and occurrences around Lingshan complex. The main ore-forming elements are tantalum and niobium, followed by tungsten, tin, molybdenum, lithium, ruthenium, zirconium, hafnium, thorium, copper, lead, zinc and iron. Among them, Huangshan Tantalum-Niobium Mine and Songshugang Tantalum-Niobium Mine have large-scale potential.

Huangshan Tantalum-Niobium Mine is located in the southwest edge of Lingshan rock mass. There are irregular albite granite, granite pegmatite nodules and dikes in the contact zone inside and outside the rock mass, in which ore bodies occur. Niobite is the main rare metal mineral, followed by zircon, thorite and titanium tantalum niobium ore. It can be divided into two types of ore bodies: granite and pegmatite. The former is distributed on the edge of the main rock mass, mostly concealed, limited to the exploration depth (most of the boreholes are the final boreholes of the ore body), and the shape and scale of the ore body have not been fully ascertained; Pegmatite-type ore bodies are distributed in the contact zone outside the main rock and occur in the limestone of Yangliugang Formation in Cambrian. Their occurrence is parallel to the contact zone of rock mass and inclined to rock mass with an inclination angle of 25 ~ 40. More than 70 pegmatite veins have been discovered, with a single vein length of 175 ~ 600 meters, a thickness of 2 ~ 19 meters and a depth of 20 meters. Both these two types of ore bodies are subjected to albitization and zinc-aluminum mineralization, and the stronger the alteration, the better the mineralization. The reserves calculation involves 16 ore bodies, mostly lenticular and veined. The main ore body is 590 m long, 232 m wide along the dip, with an average thickness of 465,438 0.3 m, dip angle of 30 ~ 45 and buried depth of 62 ~ 308 m. The main beneficial components are Nb, Ta, Zr, Hf and Th. The deposit has medium reserves of Nb2O5 and high grade (Nb2O5 0.0437%). Tantalum reserves reach a large scale, but the grade is low (Ta2O50.0044%%).

Figure 4-47 Distribution Patterns of Rare Earth Elements in Various Rocks in Lingshan Area (According to White Pigeon, 1989)

Songshugang Ta-Nb deposit is located at the top and edge of concealed granite body 2 km west of Lingshan rock body. The exposed strata in the mining area are sandy phyllite, tuffaceous slate, tuff and fine-grained feldspar timely sandstone of Tang Zhi Formation in the early Nanhua period. Generally speaking, it is a anticline structure with the northeast as the axis and the northwest wing reversed to the southeast. The faults developed in the northeast, northwest and east-west directions. The concealed rock mass intrudes into metamorphic rock in the form of rock bell, which is located in the deep part of veinlet-reticulate vein type tungsten-tin ore body. The highest elevation of the top surface of rock mass is 4 12m, which is 180m away from the surface. The occurrence around the upper part of the rock mass is steep, and the lower part gradually slows down to the southeast. The horizontal projection area of the concealed rock mass controlled by drilling is 0.85km2, and the rock mass has strong alteration and obvious vertical zoning, which can be divided into five zones from top to bottom (Figure 4-48).

1) pegmatite belt (γ ρ): occurring at the top of rock mass, it is composed of coarse-grained red microcline (> 80%), timely and green-brown zinc-blende diorite. The length of microcline is about 5 cm, the duration should be 3 ~ 4 cm, and the diameter of iron-lithium mica sheet is 2 cm. Secondary minerals and rare metal minerals are scarce. 0 ~ 18m thick.

2) Micro-plagioclase zone (γ κ): The rocks are almost entirely composed of autotype-semi-autotype micro-plagioclase. Deep down, albite stripes gradually appear in microcline, and albite also appears among particles. Due to greisenization, the residual thickness of this zone is 0 ~ 40 cm.

Figure 4-48 Schematic diagram of mineralization zoning inside and outside Songshugang rock mass (according to Baige 1989)

3) greisenized granite belt (γg): mainly composed of zinc amphibole, Yingshi and topaz. Rare metal minerals include niobite, columbite-tantalite, spar and tetragonal tantalite; Nonferrous minerals include cassiterite, galena, wolframite, sphalerite and a small amount of molybdenite. The metasomatism residue of microcline can be seen in the belt. The maximum thickness is120m.

4) Micro-plagioclase albitization granite belt (γAκ): The rocks are mainly composed of micro-plagioclase, quartz and albite, followed by topaz and zinc olivine. The rock has fine-grained porphyritic structure, and local crystal cave structure can be seen. The content of spar, columbite-tantalite, cassiterite, sphalerite and pyrite is relatively high. The maximum thickness of the belt is140m.

5) Strong albite granite belt (γAs): This belt is characterized by white and cryolite, with porphyritic structure and massive structure. The rocks are mainly composed of microcline (15% ~ 25%), albite (35% ~ 60%), Yanshi (15% ~ 30%), zinc-aluminum garnet (2% ~ 6%) and topaz (2% ~ 4%).

Tantalum-niobium ore bodies mainly occur in alteration zones such as greisen granite, plagioclase albitization granite and strong albitization granite at the top edge of concealed granite bodies. The occurrence elevation of the ore body is between 412m and-202m, and the buried depth is below180m from the surface. After detailed investigation, the length 1320 m, width 640 m and maximum thickness (false thickness) 450 m of the ore body are controlled (the ore body is not exposed). Rare metal minerals, such as columbite-tantalite, niobite, tantalite, spar, tetragonal tantalite, etc. Most of them are embedded in lepidolite, albite and other minerals, some of them are wrapped in rock-forming minerals, and the particle size is 0.02 ~ 0.31mm. The content of niobium and tantalum in independent minerals accounts for 60% ~ 70% of the total niobium and tantalum in the ore, and the rest are dispersed in cassiterite, topaz, wolframite and other minerals. In addition, the ore also contains galena, sphalerite, molybdenite, chalcopyrite, pyrite, monazite, thorium, arsenopyrite and other metal minerals. After detailed investigation, the reserves/resources of tantalum in the mining area are very large; Niobium has a medium scale; Rubidium also has a very large scale.

The surrounding rock at the top of Songshugang concealed rock mass is strongly greisenized, containing greisen type and veinlet disseminated W-Sn-Mo ore body. The surface of greisen is saccular, and the deep part is mostly lenticular or banded, which extends parallel to the contact zone of concealed rocks, with the maximum thickness exceeding 20m. The rocks are mainly composed of syenite, zinc-aluminum garnet and topaz, in which cassiterite and wolframite are embedded, and there are a large number of pyrite, galena and sphalerite in some areas. The ore grade is 0.214% tin and 0.65438 WO3. Near-surface time-dependent fine (reticular) vein type W-Sn-Mo deposit is superimposed on the greisen type W-Sn deposit, and the ore-bearing fine (reticular) vein is in a dense strip shape, with a single vein length of tens of centimeters to tens of meters and a pulse width of 1 m m to several centimeters. The wall rock alteration includes greisenization, topaz, zinc-aluminum garnet and silicification. The delineated length of the ore body is 345 meters and the total thickness is 650 meters.

In Jiaoling, Yangmeigang, Miaojiao and other places far away from the concealed rock mass, there are time-dependent tungsten-tin polymetallic deposits and lead-zinc mines. The mineralization zone is 2700 meters long and 320 meters wide, and the mineralization is extremely uneven. The ore bodies occur in veins with pulse width of 0. 1 ~ 0.55 m and single pulse length of several meters to 300 m. The metal minerals are galena, sphalerite, pyrite, chalcopyrite, wolframite, cassiterite, pyrrhotite and arsenopyrite, and tungsten, tin, zinc and lead are all small-scale.

It can be seen that Hengfeng Ge Yuan ore field is a super-large rare metal ore field related to Yanshanian alkaline granite magma activity, accompanied by or rich in non-ferrous metal minerals, and its mineralization has obvious zoning, especially in Songshugang area: vertically, from deep rocky Ta-Nb-Rb mineralization to greisen-type tungsten-tin mineralization in the contact zone (mainly in the outer contact zone) and timely veinlet-type tungsten-tin mineralization far from the contact zone. In the horizontal direction, from tin, tungsten and molybdenum mineralization in the surrounding rock at the top of the rock mass to tin mineralization on both sides and lead-zinc mineralization on the periphery, a metallogenic series of late magmatism-post-magmatic metasomatism-gas-generated high-temperature hydrothermal solution-medium-low-temperature hydrothermal solution was formed.

Two large tantalum-niobium deposits, Huangshan and Songshugang, were found in the ore field, but the breadth and depth of geological exploration were not enough. The drilling depth in mountainous areas is mostly within 500 meters, and most of them have not exposed ore bodies. In addition, around Lingshan complex granite body, there are primary tantalum-niobium mines (spots) such as Daling, Songshujing, Li Tang, Nanshan and Shirendian, and a number of alluvial tantalum-niobium placers, which are important prospecting clues and have great resource potential.