Method for predicting pegmatite lithium mineralization potential based on tourmaline spectral characteristics

Abstract

The invention discloses a pegmatite lithium mineralization potential prediction method based on tourmaline spectral characteristics, and belongs to the technical field of mineral exploration, the method comprises the following steps: taking pegmatite samples with different drilling depths, and carrying out microscopic classification on tourmaline samples in the pegmatite samples; performing element measurement on the classified tourmaline; carrying out spectrum measurement on the classified tourmaline by adopting a wavelength dispersive spectrometer to obtain spectrum data; extracting and processing the spectral characteristic parameters; obtaining wave spectrum characteristics of different types of tourmaline, and then establishing a wave spectrum database; based on the spectrum database, establishing a related diagram of the spectrum characteristic value and the lithium content; and finally, obtaining a potential evaluation result of mineralization of pegmatite type lithium based on the spectrum characteristic values of different types of tourmaline. The pegmatite type lithium mineralization can be accurately judged, a large amount of data calculation is not needed, the method has the advantages of being wide in application range, high in precision and the like, and a powerful tool is provided for geological evolution and mineralization mechanism research.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral exploration, and particularly relates to a method for predicting the pegmatite lithium mineralization potential based on the spectral characteristics of tourmaline. Background Art

[0002] Pegmatite is generally formed in the magma stage and is closely related to various plutonic rocks in terms of origin. In pegmatite, there are vein-like or massive rock bodies with coarse to giant grains, and tourmaline exists in the form of coarse to giant crystals in pegmatite. In the early stage of pegmatite mineralization, tourmaline coexists with minerals such as mica, quartz, and feldspar; in the late stage, tourmaline with compositional zoning is formed, which is characterized by being rich in more trace elements and rare elements (such as Li, Be, La, Nb, Ta, W, Sn, U, Th, etc.).

[0003] Pegmatite-type lithium resources have gradually become the main source of lithium due to their advantages such as large thickness, high grade, convenient mining, and high comprehensive development and utilization value. At present, there is a lack of an intuitive judgment method for the evolution process of pegmatite and the corresponding mineralization conditions. Different types of pegmatite tourmaline formation is usually accompanied by rare metal mineralization; based on the above changes, the degree of rare metal mineralization can be discriminated by geochemical methods, geophysical methods, geological modeling and spatial analysis, machine learning and data mining, and comprehensive methods, etc. This can reveal the origin of pegmatite, guide mineral exploration, reflect the geological evolution process, and promote the development of mineral resources. It can also reduce the blind exploration work in the early stage, narrow the exploration scope, delineate the target area rich in mineral resources, and optimize the mining plan.

[0004] (1) Geochemical methods: A series of technical means for studying the chemical properties and geochemical processes of geological bodies by analyzing the chemical elements and their isotope compositions in rocks, soils, waters, and other geological materials, and then identifying mineralization anomalies and predicting the location of ore deposits. Such as: whole-rock analysis, trace element analysis, isotope analysis, fluid inclusion analysis, and soil geochemical survey methods. These methods can help determine the chemical composition of rocks, the distribution law of elements, and the geochemical characteristics related to mineralization: ① Whole-rock analysis: By analyzing the overall chemical composition of pegmatite, the content and distribution of lithium are determined; this method has high test costs, long time consumption, and requires a large number of samples for analysis; ② Trace element analysis: Analyzing trace elements in pegmatite, such as rubidium (Rb), cesium (Cs), etc. These elements are often associated with lithium and can be used as indicator elements for lithium mineralization; however, it requires complex analysis techniques and may require professional knowledge when interpreting the results; ③ Isotope analysis: Using lithium isotopes (such as 7 Li and 6The ratio change of Li is used to identify the source and enrichment process of lithium. Due to the complex technology and high cost, this method requires specialized laboratory equipment for testing.

[0005] (2) Geophysical methods: A technical means that uses the changes in the geophysical field (such as the gravity field, magnetic field, electric field, etc.) to detect the differences in underground geological structures and physical properties. By measuring and analyzing the anomalies of these physical fields, the types, structures, and distributions of underground rocks can be inferred, as well as the physical characteristics related to mineralization can be identified: ① Magnetic exploration: By identifying the distribution of magnetic minerals in pegmatite bodies through magnetic anomalies, the distribution and structure of pegmatites can be indirectly inferred. The interpretation of magnetic anomalies in this method requires professional knowledge and is greatly affected by the environment; ② Electrical exploration: Using methods such as resistivity and induced polarization to identify the electrical characteristics of pegmatite bodies and evaluate the lithium mineralization potential. This method requires complex equipment and data processing techniques and has a high cost; (3) Geological modeling and spatial analysis: Geological modeling is to use geological data (such as boreholes, outcrops, geophysical and geochemical data, etc.) to construct a three-dimensional geological model to visually display the spatial distribution and structural characteristics of geological bodies. Spatial analysis is to process and analyze geological data through tools such as geographic information system (GIS) to identify the spatial relationships and patterns between geological bodies and provide a basis for predicting mineralization potential: ① Three-dimensional geological modeling: Construct a three-dimensional geological model of pegmatite bodies, integrate geological, geophysical, and geochemical data, and predict lithium mineralization areas. This method requires a large amount of preliminary data and the modeling process is complex; ② GIS spatial analysis: Using geographic information system (GIS) technology to analyze the distribution law of pegmatites and the spatial relationships of geological factors related to lithium mineralization. This method requires high-quality geological data, and data processing and analysis require professional knowledge; ③ Tectonic analysis: Study the tectonic background of pegmatites, such as fault zones, magmatic activities, etc., and identify favorable ore-forming tectonic environments. This method requires detailed geological background knowledge, and the interpretation results may be subjective.

[0006] (4) Remote sensing and spectral analysis: ① Hyperspectral remote sensing: Using hyperspectral remote sensing data to identify the spectral characteristics of specific minerals (such as tourmaline, lepidolite, etc.) in pegmatites and evaluate the lithium mineralization potential. This method has complex data processing and is greatly affected by weather and terrain; ② Thermal infrared remote sensing: By using thermal infrared remote sensing data to identify the thermal anomalies of pegmatites and infer the lithium enrichment areas. This method is easily affected by the external environment and has a low resolution and cannot accurately identify minerals; (5) Machine learning and data mining: Machine learning is an artificial intelligence technology that automatically learns patterns and regularities from a large amount of data by constructing algorithm models. Data mining is the process of extracting useful information and knowledge from a large amount of data. In the prediction of mineralization potential, machine learning and data mining technologies can integrate various geological, geophysical, and geochemical data, identify features and patterns related to mineralization, and establish prediction models: ① Supervised learning: Using geological, geophysical, and geochemical data from known lithium mineralization areas to train machine learning models to predict the lithium mineralization potential of unknown areas; this method requires a large amount of training data and the interpretability of the model is poor; ② Unsupervised learning: Identifying geological features and patterns related to lithium mineralization through methods such as cluster analysis; the interpretation of the results of this method requires professional knowledge and may require multiple iterations; ③ Multi-source data fusion: Integrating multiple data sources (such as geological, geophysical, geochemical, and remote sensing data), and using data mining techniques to identify potential lithium mineralization areas; the data fusion process of this method is complex and requires professional technologies and tools.

[0007] In summary, the current methods for predicting the potential of pegmatite lithium mineralization at least have the following disadvantages: (1) A large amount of data sampling, complex processing and calculations are required, and relevant mathematical models are established based on the processed data; (2) The cost is too high and the data interpretation is subjective; (3) It is unable to accurately reflect and simulate the ore-forming conditions; (4) A large amount of geological information needs to be combined for comprehensive analysis. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for predicting the potential of pegmatite lithium mineralization based on the spectral characteristics of tourmaline to solve the above problems.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for predicting the potential of pegmatite lithium mineralization based on the spectral characteristics of tourmaline, comprising the following steps: 1) Take pegmatite samples at different drilling depths, classify the taken samples under a microscope using a mineralogical microscope, and measure the elements of tourmaline in the classified pegmatite samples; 2) Use a spectrometer to measure the spectrum of tourmaline in the classified pegmatite samples to obtain spectral data; 3) Extract and process spectral characteristic parameters; 4) Obtain the spectral characteristics of different types of tourmaline, and then establish a spectral database; 5) Establish a diagram of the mutual relationship between the spectrum and the lithium content; 6) Based on the mutual relationship diagram obtained in step 5), the potential evaluation result of pegmatite-type lithium mineralization is obtained according to the spectral characteristics of tourmaline.

[0010] As a preferred technical solution, in step 1), the ore phase microscope is a digital polarizing microscope. Different types of tourmaline are classified through microscopic characteristics, and element measurements are carried out on different types of tourmaline; the element measurements include major element measurements and trace element measurements; among them, the microscopic characteristics include interference color, structure, texture, associated minerals, etc.

[0011] As a further preferred technical solution, the measurement of major elements is carried out using a JXA-iSP100 type electron probe microanalyzer of JEOL, Japan, and the measurement of trace elements is carried out using an inductively coupled plasma mass spectrometer FininganMAT LA-ICP-MS (Element Ⅰ type).

[0012] As a preferred technical solution, in step 2), the specific method of analysis is as follows: Before testing, the sample needs to be washed and dried in the sun to avoid the influence of impurities on the spectral characteristics; a CSD350 full-spectrum ground object spectrometer is used to perform fixed-point spectral measurements on the classified tourmaline samples, and at least three spectral measurements are carried out on the samples. It is preferred to test three times and take the average value to ensure the accuracy of the sample data.

[0013] As a preferred technical solution, in step 3), a mineral spectral analysis expert system (hereinafter referred to as MSA) developed by the Institute of Spectral Detection and Intelligent Sensing Technology, Jiangsu, China, and a spectral geologist analysis software (hereinafter referred to as TSG) developed by the Commonwealth Scientific and Industrial Research Organization of Australia and first introduced by Zhongke Remote Sensing Information Technology Co., Ltd. are used to extract and process spectral characteristic parameters. The spectral data is processed by MSA to obtain spectral characteristics and reflectivity values, and the absorption depth values are obtained using TSG.

[0014] As a preferred technical solution, in step 4), based on MSA and TSG, the spectral characteristics of different types of tourmaline are obtained, and their spectral databases are established; the spectral characteristics of different types of tourmaline obtained are statistically analyzed, and the spectral bands with indicative significance for different types of tourmaline are summarized.

[0015] As a preferred technical solution, in step 5), the method for establishing the diagram of the mutual relationship between the spectrum and lithium content is as follows: First, a coupling relationship between different indicative bands and lithium content is established, that is, the spectral characteristic values of different types of tourmaline are studied for the coupling relationship with lithium content, and then a quantitative inversion model of the spectral characteristic values of different indicative bands and lithium content is obtained, that is, the diagram of the mutual relationship between the spectrum and lithium content.

[0016] As a preferred technical solution, in step 6), the method for evaluating the potential of pegmatite-type lithium mineralization is as follows: Based on the said diagram, by classifying tourmalines with different lithium contents, the classification is re-divided according to lithium content, divided into tourmalines without ore, poor ore and rich ore, and the potential evaluation of pegmatite-type lithium mineralization is obtained from the spectral characteristics of tourmaline.

[0017] The formation of tourmaline is affected by geological conditions such as temperature and pressure. Under different geological conditions, the chemical composition and short-wave infrared spectral characteristics of tourmaline will change accordingly. The increase in the lithium content in tourmaline results in a larger absorption peak in its short-wave infrared, and the wavelength of H 2 O (1900 nm) shifts towards the long-wave direction, and the wavelength of Al-OH (2200 nm) shifts towards the short-wave direction. By measuring and analyzing the short-wave infrared spectral characteristics of tourmaline, identifying the characteristic absorption bands related to lithium content, establishing a quantitative relationship between the spectral characteristics and lithium content, and predicting the lithium mineralization potential of pegmatite.

[0018] The method of the present invention can establish a more intuitive revelation of the geological process of pegmatite formation, study the mineral formation conditions and evolutionary history in pegmatite, and the metallogenic law of rare metal minerals through the calculation of the spectral characteristics and lithium content of pegmatite-type tourmaline.

[0019] The present invention adopts methods such as short-wave external spectral technology, microscopic observation, electron probe, etc., establishes relevant diagrams and quantitative inversion schematic diagrams of lithium content, and judges the coupling relationship between spectral characteristics and lithium content based on the physical model method.

[0020] Compared with the prior art, the advantages of the present invention are as follows: the short-wave infrared prediction method has the ability of on-site rapid measurement; through the combination of MSA and TSG, spectral data can be converted into intuitive charts and models, thereby simplifying data interpretation and reducing subjectivity. Through spectral characteristic analysis, mineral and wall rock information can be effectively extracted without relying on dating or element analysis steps; a quantitative relationship between spectral characteristics and lithium content is established to realize the inversion and speculation of lithium content, so as to effectively evaluate the lithium mineralization potential. Compared with other traditional methods, the inversion process of the short-wave infrared prediction method of the present invention is more efficient and direct, the result interpretation is simple and easy to understand, not restricted by the environment, thereby reducing unnecessary on-site verification workload, reducing more than 85% of lithological sampling and experimental analysis, and increasing the prediction accuracy by more than 35%, as shown in Table 1.

[0021] Table 1 Comparison of different prediction methods for lithium content . Brief Description of the Drawings

[0022] Figure 1 is the flow chart of the present invention; Figure 2 Relationship diagram between the H 2 O wavelength (1900 nm) and lithium content of different types of tourmaline in pegmatite-type lithium deposits in the embodiments of the present invention; Figure 3 Relationship diagram between the Al-OH wavelength (2200 nm) and lithium content of different types of tourmaline in pegmatite-type lithium deposits in the embodiments of the present invention; Figure 4 Diagram for distinguishing ore-bearing types of tourmaline with different wavelength characteristics in the embodiments of the present invention. Specific implementation manners

[0023] The present invention will be further described below in conjunction with embodiments and drawings.

[0024] Embodiment: A method for predicting the pegmatite lithium mineralization potential based on the spectral characteristics of tourmaline successively includes the following steps: 1) Take pegmatite samples at different drilling depths, conduct microscopic classification and element measurement on the taken samples. The microscopic instrument is a digital polarized light microscope. According to the microscopic characteristics, tourmaline is divided into three categories: magmatic stage, magmatic-hydrothermal stage; the measurement of major elements is completed by a JXA-iSP100 type electron probe microanalyzer, and the measurement of trace elements is carried out by an inductively coupled plasma mass spectrometer Finingan MAT LA-ICP-MS (Element Ⅰ type); among them, the cation numbers of different types of tourmaline are shown in Table 2; Table 2 Cation numbers of different types of tourmaline , 2) Before testing, the samples need to be washed and dried to avoid the influence of impurities on the spectral characteristics; use a CSD350 full-spectrum ground object spectrometer to conduct fixed-point spectral measurement on the classified tourmaline samples, and conduct three spectral measurements on the samples to ensure the accuracy of the sample data. The spectral information is recorded according to the sorting of the drilling depths where the samples are located; 3) Use MSA and TSG to extract and process the spectral characteristic parameters. Through MSA, the spectral characteristics and reflectance values are obtained from the spectral data, and the absorption depth values are obtained by using TSG; the spectral wavelength characteristics of different classified tourmaline are shown in Table 3; Table 3 Spectral characteristics of different types of tourmaline , 4) Based on MSA and TSG, obtain the spectral characteristics of different types of tourmaline, and establish its spectral database; conduct statistics on the spectral characteristics of different types of tourmaline obtained, and summarize the bands with indicative significance for different types of tourmaline, 5) Establish the coupling relationship between different indicative wavelength bands and lithium content, that is, study the coupling relationship between the spectral characteristic values of different types of tourmaline and lithium content (Table 4), and obtain the inversion model diagram of the spectral characteristic values of different indicative wavelength bands and lithium content; Table 4 Spectral characteristics and lithium content of different types of tourmaline ; 6) According to the results obtained in step 5), the potential evaluation of pegmatite-type lithium mineralization based on the spectral characteristics of tourmaline is as follows: if the wavelength of Al-OH in the short-wave infrared spectrum of the tourmaline sample is greater than 2200.8 nm, it indicates that the pegmatite in the area where the sample is located has no potential for lithium mineralization, that is, it shows no lithium mineralization; if the wavelength of Al-OH is between 2198.7 nm and 2199.8 nm, it indicates that the pegmatite in the area where the sample is located has a small potential for lithium mineralization, that is, it shows poor lithium mineralization; if the wavelength of Al-OH is less than 2198.6 nm, it indicates that the pegmatite in the area where the sample is located has a large potential for lithium mineralization, that is, it shows rich lithium mineralization; however, the spectral characteristic boundary of tourmaline with poor lithium mineralization and rich lithium mineralization at 1900 nm does not show a good correlation ( Figure 2 , 3). Therefore, a spectral metallogenic model diagram of tourmaline is constructed based on the spectral characteristics at 2200 nm ( Figure 4 ), and this model diagram and prospecting criteria provide strong support for the further exploration of pegmatite-type lithium deposits.

[0025] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for predicting the lithium mineralization potential of pegmatite based on the spectral characteristics of tourmaline, characterized in that: The steps include: 1) Take pegmatite samples from different drilling depths, classify the tourmaline in the pegmatite samples under the microscope using a mineral phase microscope, and measure the elements of the classified tourmaline; 2) Use a spectrometer to measure the spectrum of the classified tourmaline to obtain spectrum data; 3) Extract and process spectral characteristic parameters; 4) Obtain the spectral characteristics of different types of tourmaline and then establish a spectral database; 5) Establish a graphical representation of the relationship between the spectrum and lithium content; 6) Based on the correlation diagram obtained in step 5), the potential evaluation results of pegmatite-type lithium mineralization based on the spectral characteristics of tourmaline are obtained.

2. The method according to claim 1, characterized in that In step 1), the mineralogy microscopic instrument is a digital polarizing microscope, and different types of tourmaline are classified by their characteristics under the microscope, and elemental measurements are performed on the different types of tourmaline; the elemental measurements include major element measurements and trace element measurements.

3. The method according to claim 2, characterized in that The measurement of major elements was carried out using JXA-iSP100 electron probe microanalyzer produced by JEOL, and the measurement of trace elements was carried out using Finingan MAT LA-ICP-MS, Element Ⅰ type, inductively coupled plasma mass spectrometry.

4. The method according to claim 1, characterized in that: In step 2), the specific method of the analysis is: wash and dry the samples before testing; use CSD350 full spectrum ground feature spectrometer to perform fixed-point spectrum measurement on the classified tourmaline samples, and perform spectrum measurement on the samples at least three times.

5. The method according to claim 1, characterized in that In step 3), the mineral spectral analysis expert system developed by Jiangsu Spectral Detection and Intelligent Perception Technology Research Institute of China and the Spectral Geologist Analysis Software developed by the Commonwealth Scientific and Industrial Research Organization of Australia, which was first introduced by China Science Remote Sensing Information Technology Co., Ltd., are used to extract and process the spectral characteristic parameters. The spectral data are processed by the mineral spectral analysis expert system to obtain the spectral characteristics and reflectivity values, and the spectral geologist analysis software is used to obtain the absorption depth value.

6. The method according to claim 1, characterized in that In step 4), the spectral characteristics of different types of tourmaline are obtained based on the mineral spectrum analysis expert system and the spectrum geologist analysis software, and a spectrum database thereof is established; the spectral characteristics of the obtained different types of tourmaline are statistically analyzed, and the spectral bands with indicative significance for different types of tourmaline are summarized.

7. The method according to claim 1, characterized in that In step 5), the method for establishing a graphical representation of the relationship between the spectrum and the lithium content is: The coupling between the spectral characteristic values ​​and lithium content of different types of tourmaline was studied, and a quantitative inversion model of the spectral characteristic values ​​in different indicative bands and lithium content was obtained, that is, a graphical illustration of the relationship between the spectrum and lithium content.

8. The method according to claim 1, characterized in that In step 6), the potential evaluation method for pegmatite-type lithium mineralization is: Based on the diagram of the relationship, tourmalines with different lithium contents are classified and reclassified according to the lithium content into tourmalines with no ore, poor ore and rich ore, and the potential of tourmaline spectral characteristics for pegmatite-type lithium mineralization is evaluated.

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