Techniques and Methods of Geological Prospecting of Iron Ore

1. Geological exploration types of iron ore and the density of prospecting projects In iron ore geological prospecting, prospecting projects are used to control ore bodies in accordance with economic principles. The first thing to do is to determine the density of prospecting projects. According to the ore body distribution range, size, shape change, structural complexity and ore quality change, that is, according to the difficulty of controlling the ore body, iron ore deposits are divided into four types of exploration, I, II, III, and IV. Then, different exploration types adopt different engineering density layout projects to control the change of iron ore body and delineate the ore body.
In my country’s iron ore geological exploration work, empirical methods, analogy methods, survey line profile accuracy analysis methods, rare air methods, and exploration data comparison methods are often used to determine the type of exploration and the degree of exploration engineering. In recent years, mathematical statistical analysis methods have been used to determine the degree of exploration network of mineral deposits, among which geological analogy is a frequently used method. Among the known iron ore deposits in China, the first type is the Nanfen iron ore derived from metamorphic sedimentation, and the Pangjiabao iron ore derived from marine sedimentary origin; the second type has magmatic origin Panzhihua iron ore, Shuichang, Meishan and Dading Iron ore is also of this type due to its simple shape and small grade changes; Type III includes Daye Tieshan, Jinling, Xishimen, Gushan iron deposits, etc., generally contact metasomatic and continental volcanic iron deposits; Type IV iron ore is small in scale, complex in shape, changes in occurrence, and the distribution of ore quality and quantity is unstable and discontinuous. …

2. The degree and depth of iron ore geological exploration The depth of iron ore exploration should be determined according to the actual requirements of mine construction and production.

According to my country’s current mining technical conditions, the exploration depth of iron ore is generally 300-500m, and ore bodies with a vertical depth of more than 500m use sparse boreholes to control their reserves and provide information for the overall planning of the mine. The depth determined in the iron ore exploration specifications is calculated based on the mining decline rate of 10m per year and the service life of 30 years. Therefore, the depth of the ore deposit extends down to 300m from the outcrop, which is the exploration depth of the ore deposit. Large-scale mineral deposit exploration should be carried out in phases and phases to prevent premature exploration and waste; the geological exploration of mineral deposits should be based on the principle of proving all levels of reserves required by the design scale of the first phase of the mine. In the geological exploration of iron ore, to meet the requirements of mine design for geological data and mineral reserves, different levels of exploration control should be determined for different parts of the ore body. Iron ore reserves are usually divided into four levels: A, B, C, and D: A-level reserves are used by mines to prepare mining plans and are generally explored by the mine production department; B-level reserves are high-level reserves obtained during the geological exploration stage and are distributed in mines. The first mining area under construction; C-level reserves are the basis for mine design, and its exploration engineering density is less controlled than B-level reserves; D-level reserves are controlled by sparse prospecting engineering and can only be used as a basis for prospective mine planning or further exploration. In different stages of geological exploration and different types of deposits, the requirements for the reserve ratio of various levels are different: in the mining area exploration stage, the B-level reserves of iron ore deposits must reach 10%-20%, and the B+C-level reserves must reach 50%; The detailed investigation stage generally does not require B-level reserves. Among them, C-level reserves account for the main proportion, and D-level reserves account for 10% to 30%; for more complex ore deposits, only proven C+D-level reserves are required, and C-level reserves account for 40% of the total reserves is enough. In the main exploration section or the ore bodies or sections outside the mining scope of the first phase, only the sparse engineering complex geophysical prospecting method is used to roughly find out the size, shape and distribution range of the ore body, and control the D-class reserves as a future expansion and extension of the mine scale The basis for the service life of the mine. …

3. Technical requirements for iron ore exploration In order to ensure the degree of iron ore geological research and provide reliable geological data, all geotechnical work must comply with relevant exploration specifications, so that the quality of exploration work is guaranteed to be rule-based and meet the required indicators. For example, the scale of the geological map of the mining area should reach 1/1000～1/5000, the geological base map must adopt the corresponding scale of the national geodetic coordinate system and the regular topographic base map; the filling density of the geological survey must meet the requirements of the corresponding scale, combined with the complex geology of the mining area The extent of observation points per square kilometer is determined; magnetic iron ore deposits must use magnetic survey methods to conduct geomagnetic surveys with different accuracy on the mining area (body), and use three-component magnetic logging for boreholes; prospecting projects, including exploration trenches, shallow wells, Tunnels and boreholes must be used correctly and reasonably distributed according to the ore body’s occurrence, shape and topographical conditions. Each type of project should penetrate the ore body at the maximum angle of intersection; the drilling project must have strict quality requirements, such as the core rate (including the top , The surrounding rock within 5m of the floor) shall not be less than 75%, and the average core sampling rate shall not be less than 65%. Identifying the quality of iron ore is the most important geological task in exploration. The purpose of all exploration projects is to cut through the ore body as much as possible and systematically take mineral samples.

Therefore, the sampling, processing and testing of ore samples have clear regulations to ensure the reliability and representativeness of samples and test results. in:

(1) The basic analysis mainly finds out the iron content of the ore. It requires continuous sampling according to the type of ore. Generally, the sample length is 1～2m. The grooved well and tunnel sampling are generally carried out by the groove method. The section specification is 5cm×2cm or 10cm×3cm. . The basic analysis item is total iron (TFe), but when the content of iron silicate, iron sulfide and iron carbonate reaches 5%, magnetic iron (mFe) should be added, mFe is used to delineate the ore body, and used to delineate the boundary of the oxide ore body. For the associated useful components, harmful impurities, slagging components, etc. in the ore, it should be determined whether to do basic analysis or combined analysis according to their content changes and industrial index requirements. To

(2) Combination analysis Identify the content and distribution of beneficial and harmful components, and calculate the content of associated components. The combined sample shall be divided into ore body, ore type, etc. according to the engineering combination, and the weight is generally 100-200g, which shall be extracted in proportion to the length of the sample from the secondary sample of the basic analysis sample. The analysis items are generally determined based on the results of the full spectrum analysis and the full chemical analysis. The analysis items are mainly SiO2, S, P, etc. To

(3) Spectral full analysis and chemical full analysis The former is to understand the elements and their approximate contents in ore and surrounding rock as the basis for determining chemical full analysis items. Samples are taken from different parts of the ore body and samples of different ore types. The latter is to quantitatively determine the content of the main elements and their components in various ore types to determine the properties and characteristics of iron ore. It is carried out on the basis of full spectrum analysis and rock and mineral identification. Samples can be extracted from combined analysis sub-samples, or representative samples can be collected separately. Generally, 1 to 3 pieces are required for each ore type, and the total analysis should be within the range of 99.3% to 100.7%. To

(4) Phase analysis mainly uses physical and chemical phase analysis methods to determine the occurrence state, content and distribution rate of iron in iron ore, to determine the natural zoning of the ore, and to provide a basis for determining the ore beneficiation process and conditions. Iron mineral phase analysis generally analyzes five types of magnetic iron, iron silicate, iron carbonate, iron sulfide and hematite. To

(5) Single mineral analysis To find out the chemical composition of iron minerals in the ore, and the occurrence and distribution of associated useful components, mainly to determine the process of beneficiation and smelting for industrial use. The single mineral sample that is easy to sort generally weighs 2-20g. The processing of iron ore samples shall be carried out according to the Q=Kd2 formula, and 3% to 5% of samples shall be drawn for internal inspection, and the sample reduction error shall not exceed 3%. The quality of chemical testing should be inspected internally and externally to determine accidental and systematic errors in basic analysis. The number of internal inspections must reach 10%, and the number of external inspections must reach 3% to 5%. When the total number of samples is small, it must be no less than 30. The chemical analysis and phase analysis of iron ore allow accidental errors not to exceed the “standard” requirements. In order to determine the utilization performance of the ore industry and the process flow of beneficiation and smelting, all ore beneficiation samples shall be tested for beneficiation. Optional tests and process tests should be carried out in both the detailed census stage and the mining area exploration stage. The beneficiation test results are the basis for evaluating the industrial value of iron ore deposits and determining the content and calculating industrial indicators. The beneficiation test samples must be sufficiently representative. The weight of samples for continuous laboratory expansion is generally several tons, and the weight of samples required for semi-industrial and industrial tests depends on the production scale and test time of the experimental plant. The beneficiation test is generally carried out by the exploration unit, the semi-industrial test is carried out by the cooperation of the exploration unit and the industrial department, and the industrial test is carried out by the industrial department. The identification and research of technical conditions for mining deposits is an important part of the iron ore exploration work. In the work, the physical and technical properties of the ore and the surrounding rock near the ore should be measured to provide the necessary technical parameters for iron ore mining: including weight, lumpiness, humidity, porosity, looseness coefficient and angle of repose, etc. Among them, the large and small weights of iron ore are also important parameters for the calculation of reserves. According to the “standards”, the weight of iron ore shall be determined, and the small weight shall not be less than 30 pieces of each type of ore; the large weight shall be measured per piece (time) The volume must not be less than 0.125m

3. The final work of geological exploration of iron ore deposits requires reserves calculation. The industrial indicators used in the calculation of reserves in the exploration phase are different from the general indicators used in the census and detailed investigation phases, and the geological exploration department must determine the boundary grade, industrial grade, recoverable thickness, and rock inclusion thickness based on the actual geological data of each deposit. The ore body is delineated and the ore reserves are calculated according to the approved index issued by the industrial utilization department and the relevant superior department. Generally, ore bodies should be delineated strictly according to the indicators, and the most reasonable and correct reserves calculation method should be selected. Various boundaries and blocks should be divided according to the ore body and ore types, and their reserves and average grades should be calculated separately. At the same time, the comprehensive recycling group should be calculated According to the reserves, delimit the mined-out area and the depth of the oxidation zone. To

4. Technical requirements for hydrogeological exploration in mining areas Hydrogeological work is required at all stages of iron ore geological exploration. In the census stage, based on the analysis of regional hydrogeological conditions, combined with the hydrology, geomorphology and geological characteristics of the mining area, the hydrogeological conditions of the mining area are generally reviewed; the detailed census stage requires the corresponding hydrogeological survey of the mining area and simple hydrological observations; the exploration stage of the mining area Need to deploy detailed hydrogeological surveys and special hydrogeological work in mining areas. The hydrogeological work of the mining area is based on the study of the hydrogeological conditions of the area, to find out the reasons for the water filling of the ore deposit, the complexity of the hydrogeological conditions of the ore deposit, and the various characteristics and water richness of the aquifer in the mining area. Through special hydrogeological engineering and pumping tests, reliable hydrological data can be obtained. Correctly calculate and predict the maximum water inflow of the pit (well) in order to provide research on the development plan, mining method, mine water and waterproof measures. To

5. Research requirements for mining technical conditions This research is mainly carried out during the exploration stage of the mining area. It is required to ascertain the impact of rock and ore properties and structural fracture zones on mining; determine the mechanical and physical properties of the ore body and the top and bottom rocks of the ore body, including the technical and physical properties of the ore, the stability of the top and bottom rocks of the ore body, and the hardness of the rock , Compressive, tensile and shear strength; determine and calculate the mining stripping ratio, slope angle, dilution rate; determine the oxidation zone and other unfavorable mining conditions. It is necessary to analyze and determine the type and complexity of the engineering geology of the ore deposit based on the geological conditions of the iron ore area in order to further carry out the engineering geological survey work. The prediction and evaluation of environmental pollution and man-made disasters that may be caused by mines, as well as all factors that affect the production and construction of mines, must be fully estimated and predicted during the geological exploration stage.

6. Requirements for technical and economic evaluation of mineral deposits Based on the geological data provided by geological exploration, proven reserves and technical and economic conditions of the mineral deposit, a comprehensive, systematic and accurate evaluation of the economic value of the future industrial development and utilization of the mineral deposit, as well as the rationality of mine construction, shall be conducted. Ensure the reliability of infrastructure investment in iron ore mines, and estimate the economic value and economic effects of future development and utilization of the ore deposit. In the technical and economic evaluation of iron ore deposits, comprehensive utilization of symbiotic and associated minerals, protection of mineral resources, and environmental pollution should be fully considered