The mining area is located in Xiangtan Bay Basin of Sinian system on the southeast edge of Jiangnan axis of Yangtze paraplatform, belonging to Au-Ag-Pb-ZnW-Mn-V- fluorite ore belt in the east of Jiangnan uplift. The basement structure of the mining area was formed in Xuefeng period, and it is generally distributed in the east-west direction, mainly with gentle and open folds, with a wide range and large scale, which plays an important role in controlling the formation and distribution of manganese ore.
1. Brief description of mine geology
(1) stratum
The exposed strata in the mining area are relatively simple. Except Quaternary, the main exposed strata are: gray-green slate of Banxi Group in Yuanguyu; Lower Sinian clastic rocks of He Ling Formation, black shale with carbonate rocks of Nantuo Formation and Meng Xiang Formation, clastic rocks of Shangjinjiadong Formation, siliceous rocks of Liuhapo Formation, etc.
The manganese-bearing rock series of the deposit occurs in Meng Xiang Formation of Lower Sinian, and consists of black shale and manganese carbonate layer rich in carbon, organic matter and pyrite. The top is black slate, the middle is manganese carbonate-containing section, and the bottom is clastic section. Generally, there is only one main ore bed in manganese-bearing rock series, and there is an interlayer ore and a lenticular manganese carbonate ore bed above the main ore bed in some areas.
(2) Structure
The whole area is monoclinic structure with faults and secondary folds developed. Strata strike northeast-southwest, inclined northwest, dip angle 10 ~ 88, and some sections are vertical or even inverted. The strata along the 40 ~ 46 line developed in an S shape, forming an inverted recumbent fold. The shallow stratum to the west of Line 46 is steep, and the deep stratum fluctuates gently. Xiangtan manganese mine is located in the northern wing of Xianshan anticline. The axis of fairy mountain anticline is close to the east and west, and Banxi Group is exposed on the axis. The outcrop in the northern part of the anticline completely controls the distribution of He Ling, Qingshan, Huangfengsi and Shi Chong ore sections. After mineralization, faults developed in Xiangtan manganese ore field, and 25 large and small faults have been found, which can be divided into strike faults, oblique faults and transverse faults according to their occurrence. Among the three types of faults, strike fault is the most developed and largest, and it is also the main ore-breaking structure; Oblique fault is the second; The scale of transverse fault is the smallest.
(3) Magmatic rocks
No magmatic rocks are exposed in this area.
2. A brief description of the characteristics of the deposit
(1) ore body characteristics
The ore bodies in this area occur in the lower middle part of the ore-bearing black shale section of Lower Sinian, with linear black shale as the floor and foliated black shale as the roof. The main ore body is one layer, which is continuous as a whole and stable in horizon. The scale of ore bodies is medium, with a total length of 8800m, and the length and width of each ore body are 1900 ~ 2700 m and 105 ~ 580 m (the maximum width is 2000m). The orebody strike is 50, and the dip angle is 65438+08 ~ 25. The occurrence of ore body is consistent with the surrounding rock, and it is layered and quasi-layered. The thickness of ore body is 0.3 ~ 5.33 m, and the average thickness is 1. 18 m, which is controlled by secondary folds and the shape of ore body changes greatly. The highest manganese grade is 24.09%, the lowest is 15.88%, with an average of 20.88%. TFe content is generally 2% ~ 4%.
(2) Ore type and structure
Manganese carbonate ore in this area can be divided into three types according to its structural characteristics: interlayer ore, fractured ore and banded ore. The main ore type in the area is banded ore with aphanitic-fine grain structure. The higher the manganese content, the smaller the grain size. Broken ore is located on banded ore, usually with fine-grained structure, and the particle size is about 0.0 1 mm. Interlayer ore is located in the upper part of the main ore bed, mainly in the shallow part, but rare in the deep part.
Specimen name Manganese carbonate ore number DB0 16- 1 Precambrian formation age.
Atlas of large ore specimens from typical mines in China
The ore specimen was collected from Xiangtan mining area. The surface of the specimen is gray-gray-black, with cryptocrystalline texture and massive structure. Ore minerals mainly include manganese carbonate, rhodochrosite, calcium rhodochrosite and so on. Gangue minerals are quartz, calcite and kaolinite. The manganese grade is 20.5%
Genetic types of Xiangtan manganese mine in Xiangtan city, Hunan province marine sedimentary genesis