The purpose and task of detailed investigation is to basically find out the metallogenic geological conditions in this area on the basis of collecting and studying previous geological, geophysical and hydrological environment data; Basically find out the shape, scale, occurrence, thickness, distribution and ore quality of concealed ore bodies; Find out the technical conditions of mineral deposit exploitation basically: study the technical performance of ore processing and briefly study the economic significance of mineral deposit exploitation; Compile the detailed investigation report of Tuntou Iron Mine in Zhaicun Mining Area, Yanzhou City, Shandong Province, and provide geological basis for the next exploration or development and utilization of the mining area.
1. Regional Geology
(1) structural position
This area is located in the southeast edge of North China Plate (Ⅰ), the middle of Luxi Uplift (Ⅱ), the eastern end of Heze-Yanzhou Fault Depression (Ⅲ), the eastern edge of Jiaxiang-Yanzhou Semi-submersible Fault Arch (Ⅳ), the junction of Yanzhou Semi-submersible Syncline Fault Block (Ⅴ) and the northern end of Jining Syncline Fault Depression (Ⅴ). Regional bedrock strata are exposed sporadically, covered by Quaternary loose sediments in a large area, with developed fault structures and weak magmatic activity.
(2) Regional level
The strata in this area belong to Jinan-Tengzhou stratigraphic division of Luxi stratigraphic division of Shanxi-Hebei-Shandong-Henan stratigraphic division of North China stratigraphic division. The regional bedrock strata are all covered by Quaternary loose sediments except Guanyangshan, which is about 0.6km2 exposed. The regional bedrock strata mainly include the Neoarchean Jining Group from old to new; Paleozoic Changqing Group Zhushadong Formation and Mantou Formation, Jiulong Group Zhangxia Formation, Gushan Formation, Chaomidian Formation, Sanshanzi Formation and Majiagou Formation, Yuemengou Group benxi formation, Taiyuan Formation, Shanxi Formation and Shihezi Formation; Santai Formation of Mesozoic Zibo Group and Shuinan Formation of Laiyang Group; Luchang Formation and Dawenkou Formation of Gongzhuang Group in Cenozoic. Jining Formation is found in boreholes and mainly distributed near the mining area, belonging to a set of greenschist facies shallow metamorphic rock series. Its original rock formation belongs to neutral-intermediate acid volcanic rock-sandstone-mudstone-ferrosilicon sedimentary formation, which is the ore-bearing rock series in this area.
(3) Structure
This area is located at the intersection of Yanzhou semi-submersible syncline fault block and Jining syncline fault depression, bordering the Dian fault in the east and the Jining syncline fault depression in the west. The basement strata are mainly monoclinic structures, which tend to the southwest with a steep dip angle of 55 ~ 65. The caprock is developed by fold structure and fault structure.
1) discount. The caprock folds are developed in this area, and the main fold structures are Yandian anticline, Yanzhou syncline and Jining syncline. Yandian anticline: Located in Yandian-Xinbeizhuang area, it is a broad and gentle anticline structure. The axis of the anticline is 60 ~ 70, the core stratum is Paleozoic Majiagou Formation, and the strata in the northwest and southeast wings are late Paleozoic Carboniferous-Permian coal-bearing strata. The northwest wing is cut off by Yuncheng fault, and the stratum occurrence is 330 ~ 340 ∠ 10 ~ 20. The strata in the southeast wing tend to the southeast with an inclination of 5 ~ 10. Yanzhou syncline: Located in the southeast of Yandian anticline, near Pingyangsi town, the core strata are mainly composed of Carboniferous-Permian coal-bearing strata and Jurassic-Cretaceous strata. The northwest wing is composed of Ordovician strata with a dip angle of 350 and a dip angle of 5 ~ 10. The southeast wing was cut by Yishan fault. Jining syncline: it is mainly composed of Carboniferous-Permian strata in late Paleozoic and Cretaceous strata in Mesozoic. Generally, it is an axial NE composite syncline. The northeast and southwest of syncline were cut by Sun Shi Dian fault and Jiaxiang fault respectively, and the near core was invaded by olivine gabbro in the late Yanshan period. The two wings of the syncline are composed of a series of small folds near the northeast.
2) fracture. Faults are developed in this area, which can be divided into three groups according to strike: near east-west, near north-south and northwest. ① Near east-west fault. Yuncheng fault: The distribution area is in the north, starting from Zhang Ying in the west, passing through Yangcun, Xinyi and Baijiadian to Qufu East, with a length of 88 km. The fault oscillates in a zigzag pattern in the east-west direction, and its cross section is inclined to the north with an inclination of about 70, and the fault distance is more than1000 m. It is a large concealed fault, and the geophysical data such as gravity and magnetism show clearly. This fault is a tensional normal fault. ② Near north-south fault. Near-north-south fault is the main fault structure in the area, which forms a checkerboard lattice structure with near-east-west faults in the area. The larger faults in this area are Jiaxiang Fault and Sun Shi Branch Fault from west to east. Jiaxiang Fault: It starts from Jinxiang County in the middle of the distribution area and passes through Jihu Town, Mengmiao Town, Changgou Town, Wang Nan Town and Xu Jidong, with a length of 84 km. It extends in a nearly N-S wave shape, with an overall strike of 350, an inclination of 80 and a fault distance of 400-2,000m. The fault cuts the Wenshang-Ningyang fault depression, which controls the formation of the convex fault and the fault depression on both sides, and generally shows the characteristics of tensile fault. Sun Shi store fault: starting from Weishan county in the south, passing through Shiqiao and Yandian to Baita. The area is 75km long, with a fault bandwidth of 10 ~ 100m, and it bends and swings along the strike like waves. The overall strike is 345, the dip angle to the west is 70 ~ 80, and the fault distance is greater than1000 m. On the Bouguer gravity anomaly map, it is a normal anomaly with a nearly north-south twist distribution. ③ NW-trending fault. The scale of NW-trending faults in this area is generally small, and Xuji fault, Xindian fault, Dongwusi fault and Yanzhou fault are developed from west to east. The representative fault is Yanzhou fault. Yanzhou fault: it is located in the east of the distribution area, with the northwest end from Caohe River in Baishi East longitude and south of Yanzhou, and the regional length is about 5 1 km. It bends in a wave shape along the strike, with an overall strike of 340 ~ 350 and a dip angle of 70 ~ 80 to the northeast. The fault in Shu Dong area is confirmed by geophysical prospecting and drilling data of Ningyang coalfield survey, and it is a tensile fault with the west plate rising and the east plate falling. Magmatic activity in this area is weak, and magmatic rocks are mostly distributed in coal measures strata and Jining Group strata in the form of dikes. The main rock types are fine-grained olivine gabbro, diorite porphyrite and diorite.
2. Geology of mining area
(1) stratum
There are few bedrock outcrops in this area, only about 0.6km2 of bedrock outcrops are found in Guyangshan, northwest of the mining area. The outcrop is limestone and marl in Wuyangshan section of Majiagou Formation of Ordovician, and other areas are covered by Quaternary. According to the drilling data in the mining area, the strata in the mining area are mainly Neoarchean Jining Formation, Paleozoic Changqing Formation Zhushadong Formation and Mantou Formation, Jiulong Formation Zhangxia Formation, Gushan Formation, Chaomidian Formation, Sanshanzi Formation and Majiagou Formation, as well as Cenozoic strata. Jining rock group is the ore-bearing bed of iron ore.
In 2009, Zhang and Jiao Xiumei of Shandong Geological Exploration Bureau systematically catalogued and sampled the drilled cores of Jining Group in Yandian mining area for the purpose of "Study on Geological Characteristics and Mineralization of Jining Group". On the basis of preliminary comprehensive analysis and research, Jining Formation is divided into Zhaicun Formation, Yandian Formation and Hongfusi Formation from bottom to top.
Zhaicun Formation: Metamorphic pyroclastic rock formation. It is mainly composed of metamorphic dacite or andesite pyroclastic rock and fine sandstone containing volcanic breccia, with metamorphic siltstone, carbonaceous phyllite and metamorphic dacite. The top part is bounded by metamorphic dacite and Yandian Formation, and the thickness changes greatly. The bottom part is exposed at the end of the borehole, with the maximum thickness of 474 m.
Yandian Formation: Iron-bearing strata. Magnetite quartzite and chlorite phyllite interbedded with chlorite sericite phyllite, carbonaceous phyllite, metamorphic siltstone, locally intercalated dacite or tuffaceous clastic rock containing volcanic breccia. The exposed thickness of borehole is about 252 ~ 531m.
Hongfusi Formation: carbonaceous phyllite mixed with siltstone formation. Mainly carbonaceous phyllite mixed with carbonaceous phyllite, sericite phyllite and metamorphic siltstone. No top or bottom was found during drilling, and the maximum thickness was about 562 m.
(2) Structure
Quaternary system is developed in this area, and the rock strata are poorly exposed. Based on the collection and utilization of previous geophysical data, CSAMT profile of controlled source audio magnetotelluric sounding is laid in the abnormal area, and the internal structure of the area is studied in combination with borehole data. The structure in this area is dominated by faults, mainly including faults F 1, F4, F5, F6 and F7.
(3) Magmatic rocks
Magmatic rocks are not developed in this area, and it is found that diorite and diabase are distributed in the metamorphic rocks of Jining Group in layers, mainly in veins. From the situation of engineering control, diabase is small in scale and has not caused damage to coal seam. The diorite is slightly larger in scale, which damages the joints. ZK3502 on Line 35 is about 38 m thick, extends about 400 m along the strike, and the dip angle is about 200 m, which has destructive effect on No.20 ore body. Line 39 ZK3906 and ZK3907 control the same diorite vein, and the pulse width is 32 ~ 83m. The strike extends to ZK430 1, and the dip extends for more than 500 meters, napping No.33 and No.34 ore bodies along the strike. Diorite is light gray, with semi-authigenic granular structure and massive structure remaining. It is mainly composed of plagioclase, chlorite and calcite, with a small amount of opaque minerals, quartz and tourmaline. The accessory minerals are apatite. Plagioclase in rocks is mostly semi-self-shaped plate, which consists of fragments of different sizes, and the fragments are filled with chlorite and calcite.
3. Ore body geology
(1) ore body characteristics
Zhaicun Iron Mine is a concealed deposit. There are 44 iron ore bodies delineated in the deposit, numbered as 1, 2, 3, …, 44 in turn, of which 20, 4, 38 and 19 are the main ore bodies, with a resource of 77074.7× 104t, accounting for 332+. Others are small mines, and the ore source accounts for 27.338+0%(332+333) of the deposit resources. Ore bodies occur in metamorphic rocks of the Neoarchean Jining Group, and the overlying strata are Cambrian to Ordovician strata. The ore body is layered and quasi-layered, and the occurrence of the ore body is consistent with the surrounding rock. 1 ~ 8 ore bodies are distributed between 0 ~ 15 lines, and the ore-bearing rocks are magnetite chlorite sericite phyllite, with an overall strike of 342 ~ 354, and a dip angle of 58 ~ 65. Orebodies 9 ~ 44 are distributed between lines 23 ~ 47, and the ore-bearing rocks are banded magnetite quartzite. The overall strike is 326 ~ 359, and it tends to the southwest with an inclination of 54 ~ 70.
No.20 ore body is one of the main ore bodies in the deposit, with a resource of 38,938.0×104t, accounting for 36.77% of the (332+333) resource of the deposit. Orebodies are distributed in layers between Line 23 and Line 43, with the occurrence elevation of-1830 ~-1076m and the buried depth of118 ~1567m. The ore body is controlled by 9 holes, the length of the ore body is controlled at 2 134m, the dip depth is controlled at 290 ~ 888 m, the ore body strike is 326 ~ 338, and it tends to southwest and west, and the dip angle is 54 ~ 68. The dip angle of ore body gradually expands from the middle to both sides along the strike, and the dip angle of 39 line is 68. The ore body extends along the strike to Yandian mining area north of Line 23, but it is not closed in the south. Ore bodies are characterized by obvious extension and contraction along strike and dip, branching and compounding, and pinching out. The ore bodies of Line 39 and Line 43 are single-layered, and the ore bodies to the north of Line 23 are divided into 3 ~ 5 layers, and the lithology between layers is chlorite sericite phyllite, magnet timing, etc.
The thickness of a single engineering ore body is 26.4 1 ~ 198.39 m, the average thickness is 97.49m, the thickness variation coefficient is 5 1.29%, and the thickness variation is stable. The thickness of the orebody in Line 39 is the largest, and it gradually becomes thinner towards the south and north along the strike, and gradually becomes thinner towards the deep along the dip, but it is still not closed. TFE content in a single sample is 20.68% ~ 42.92%, MFE 15.0 1% ~ 37.33%, and TFE content in a single engineering ore body is 26.64% ~ 36.30%. mFe 20.52% ~ 24.83%； The average content of ore body is TFe 32.60% and mFe 23.06%. The coefficient of variation of TFe 15.75% and mFe 2 1.06% are consistent.
(2) Ore quality
The metal minerals in the ore body mainly include magnetite, hematite, limonite, pyrite, chalcopyrite, pyrrhotite and sphalerite. Non-metallic substances include quartz, chlorite, sericite, carbonate (iron-bearing calcite, ankerite and siderite) and a small amount of epidote, feldspar, biotite and kaolinite.
According to the basic analysis results, the main useful component of ore is iron. The average content of TFe 3 1.09%, mFe 22.44% and mFe/TFe 72. 18% in the deposit (332+333) indicate that the iron in the ore mainly exists in the form of magnetic iron. Spectral analysis shows that the ore does not contain beneficial elements, and the average content of harmful components S and P is lower than the standard.
(3) Ore structure
The ore structure is authigenic-heteromorphic granular structure, inclusion structure and fragmented structure.
Ore structures are mainly banded structures and banded dense disseminated structures.
(4) Characteristics and genesis of ore types.
The natural type of ore in this deposit is mainly timely banded magnetite, followed by chlorite-sericite banded magnetite. The industrial type is weakly magnetic iron ore; The genetic type is sedimentary metamorphic iron ore.
4. Physical data collection
ZK3903 drilling, final hole footage 1834.438+05 m. 19, No.20 and multi-layer iron ore bodies were respectively penetrated, and there were spotted limestone, limestone, dolomite, argillaceous limestone, breccia marl, breccia dolomite, dolomite containing flint nodules (zones), banded limestone, massive limestone with shale, oolitic limestone, algal limestone, sandstone. The ore bed is magnetite quartzite with granular metamorphic structure and banded structure. The main mineral components are timely magnetite and calcite. Its magnetism is stable and continuous.
5. Relevant information
1) Geological map of bedrock in Zhaicun iron mine area, Yanzhou City, Shandong Province;
2) Geological profile of exploration line 39 of Tuntou Iron Mine in Zhaicun iron mine area;
3)ZK3903 borehole histogram;
4)ZK3903 borehole geological record;
5) Brief introduction of Tuntou Iron Mine in Zhaicun Mining Area, Yanzhou City, Shandong Province.