Method for analyzing distribution characteristics and restricting factors of rare earth elements in weathered section of granite

Abstract

The invention discloses a method for analyzing distribution characteristics and restricting factors of rare earth elements in a granite weathering profile, and belongs to the field of mineral resource analysis, the analysis method comprises the following specific steps: I, recording the layering condition of the granite weathering profile, and collecting and analyzing each layer of sample; iI, analyzing the element enrichment degree in each sample, and evaluating the weathering degree of each sample; iII, recording the content and weathering characteristics of major elements in each sample; iV, analyzing influence factors of migration and enrichment of rare earth elements in various granite weathering crust according to a recorded result; according to the method, migration and enrichment behaviors of the rare earth elements in the vertical section can be comprehensively mastered, background differences are effectively eliminated, the scientificity of behavior comparison of the rare earth elements between different layers is improved, the enrichment and distribution mechanism of the rare earth elements under the medium weathering degree is revealed, and the mineral stability can be judged.

Description

Technical Field

[0001] The present invention relates to the field of mineral resource analysis, and particularly to a method for analyzing the distribution characteristics and restricting factors of rare earth elements in granite weathering profiles. Background Art

[0002] Chemical weathering is a key process of surface processes, affecting soil formation and regulating climate, and is also an important behavior connecting the interaction between spheres and the cyclic migration of key elements in the surficial environment. Rare earth elements (REEs) consist of 17 elements including the lanthanide elements of Group IIIB and scandium (Sc) and yttrium (Y). Their geochemical behaviors are similar, and they are generally considered to be stable in the processes of weathering and alteration, and are widely used in the study of sediment provenance tracing. However, there are slight differences in the physical and chemical properties among the rare earth elements, resulting in different degrees of fractionation in the surficial environment. Studying the geochemical behavior of REEs under weathering can reveal the migration and enrichment laws of REEs, which is of great scientific significance for understanding the chemical processes in the Earth's surface layer and the behavioral changes of key elements under the influence of climate environment. Granite (including granodiorite) accounts for about 77% of the volume of the upper crust. The content of rare earth elements in granite is relatively high. Especially in the coastal areas, which have experienced a long-term humid climate environment, chemical weathering is strong, and a large area of granite weathering crust has developed. The fractionation characteristics of light and heavy elements during the process of granite weathering into soil are affected by chemical weathering intensity, redox conditions, and climate environment changes. Research shows that the content of rare earth elements in the weathering crust in South China is positively correlated with the weathering intensity. However, the chemical weathering intensity is significantly affected by temperature and rainfall. When the weathering degree is relatively high, strong leaching will also cause the relative leaching of heavy rare earths. Therefore, there may be a threshold effect of weathering intensity on the enrichment of rare earth elements. Strengthening the study of the distribution characteristics of rare earth elements in the weathering crust under medium weathering degree is crucial for understanding the surficial enrichment and even the metallogenic mechanism of rare earth elements. Therefore, we propose a method for analyzing the distribution characteristics and restricting factors of rare earth elements in granite weathering profiles. Summary of the Invention

[0003] The purpose of the present invention is to solve the defects existing in the prior art, and to propose a method for analyzing the distribution characteristics and restricting factors of rare earth elements in granite weathering profiles.

[0004] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for analyzing the distribution characteristics and restricting factors of rare earth elements in granite weathering profiles, the specific steps of the analysis method are as follows:

[0006] Ⅰ. Record the layering situation of the granite weathering profile, and collect and analyze samples of each layer;

[0007] II. Analyze the element enrichment degree in each sample and evaluate the weathering degree of each sample;

[0008] III. Record the content of major elements and weathering characteristics in each sample;

[0009] IV. Based on the recording results, analyze the influencing factors of the migration and enrichment of rare earth elements in various granite weathering crusts.

[0010] As a further scheme of the present invention, the stratification of the granite weathering profile in step I specifically includes the surface soil layer A, the weathered layer B, and the parent material layer C;

[0011] Among them, the range of layer A is from the ground surface down to 0 - 30 cm, the brightness L* is 59.30 - 63.08, the redness a* is 9.21 - 11.39, the yellowness b* is 24.61 - 27.95, and the top of layer A is a brown humus layer, containing a small amount of plant roots, with a loose structure and fine particle size;

[0012] The range of layer B is from the ground surface down to 30 - 210 cm, the brightness L* is 61.39 - 65.50, the redness a* is 11.31 - 14.22, the yellowness b* is 28.40 - 30.75, and layer B is red and earthy, with fine particles, relatively compact texture, and no original rock structure;

[0013] The range of layer C is from the ground surface down to 210 - 300 cm, the brightness L* is 65.78 - 67.51, the redness a* is 9.17 - 10.63, the yellowness b* is 27.34 - 28.59, and the color of layer C gradually transitions from red to yellowish-brown, with a compact texture, containing a gravel structure, the original rock form can be seen, and it is in a semi-rock and semi-soil state.

[0014] As a further scheme of the present invention, the specific steps of collecting and analyzing the weathered samples of each layer in step I are as follows:

[0015] S1.1: After removing the surface floating soil of the outcropping granite profile, continuously sample at 10 cm intervals from the top to the bottom of the granite profile, a total of 31 samples are collected, among which, there are 4 samples in layer A, respectively marked as ND01 - ND04, 18 samples in layer B, respectively marked as ND05 - ND22, 9 samples in layer C, respectively marked as ND23 - ND31. Then, after the collected samples of each group are naturally air-dried, pick out the excess plant roots in the samples, and then grind the dried samples with an agate mortar to less than 200 meshes;

[0016] S1.2: Weigh 4 g of the sample powders of layer A, layer B, and layer C respectively. Place the sample powders of each layer into the tablet press in sequence. Then, use boric acid as the binder, apply a pressure of 30 t in the tablet press, and press the weighed sample powders of each layer into smooth sample wafers. Use an X-ray fluorescence spectrometer to obtain the percentage content of major elements in each sample wafer, and express the results in the form of elemental oxides.

[0017] S1.3: Weigh 40 mg of the sample powders of layer A, layer B, and layer C respectively, and place them into Teflon sealed digestion vessels. Add 0.3 mL of nitric acid and 1 mL of hydrofluoric acid. After mixing and sealing, place the Teflon sealed digestion vessels in an environment at 120 °C for digestion for 24 h. After digestion is completed, open the Teflon sealed digestion vessels and evaporate to dryness.

[0018] S1.4: After evaporation to dryness in the open vessel, add 0.3 mL of nitric acid, 1 mL of hydrofluoric acid, and 0.5 mL of perchloric acid to the Teflon sealed digestion vessel again, and then place it in a sealed state for heating at 120 °C to dissolve all minerals. After the sample dissolution is completed, transfer and make up the volume, and then use an ELEMENT XR high-resolution inductively coupled plasma mass spectrometer to perform parallel sample analysis and standard substance determination on each layer of samples respectively.

[0019] S1.5: Set the working voltage of the X-ray diffractometer to 40 Kv, the working current to 40 Ma, use copper target radiation, and perform scanning on each sample wafer according to the parameter settings of a scanning range of 5° to 80° and a scanning speed of 3° / min to generate corresponding scanning spectra. Then, use MDI JADE 9.0 software to smooth, subtract the background, find peaks, and perform phase retrieval on the experimentally measured spectra in sequence, and use the K-value method to perform semi-quantitative calculation of the mineral content.

[0020] As a further solution of the present invention, the specific steps for analyzing the element enrichment degree in each sample in step II are as follows:

[0021] S2.1: Select the stable element Ti as the reference element, and then collect the content information of the reference element and major elements in various samples obtained through experiments. Then, calculate the corresponding Δ value based on the major element content and the reference element.

[0022] S2.2: If the Δ value is positive, it indicates that the element in the weathered crust is enriched relative to the bedrock; if the Δ value is negative, it indicates that the element in the weathered crust is depleted relative to the bedrock.

[0023] S2.3: Divide the rare earth elements into 2 - 3 groups. Among them, the light rare earth group ranges from lanthanum (La) to europium (Eu), the middle rare earth group ranges from samarium (Sm) to holmium (Ho), and the heavy rare earth group ranges from gadolinium (Gd) to lutetium (Lu). Then, use chondrites to standardize various samples, and indicate the migration and enrichment of rare earth elements in the profile by calculating the enrichment factor of various samples relative to the bedrock.

[0024] As a further solution of the present invention, the specific calculation formula of the Δ value in S2.1 is as follows:

[0025]

[0026] In the formula, X s represents the content of the element to be measured in the sample; X rock represents the content of the reference element in the sample; I s represents the content of the element to be measured in the bedrock; I rock represents the content of the reference element in the bedrock;

[0027] The specific calculation formula of the enrichment factor in S2.1 is as follows:

[0028]

[0029] In the formula, EF; [REE / Ti] sample represents the normalized difference between the content of rare earth elements REE and Ti content in the sample; [REE / Ti] rock represents the normalized difference between the content of rare earth elements REE and Ti content in the bedrock.

[0030] As a further solution of the present invention, the specific steps for evaluating the weathering degree of each sample in step II are as follows:

[0031] S3.1: Correct CaO in phosphate with P2O5, and then compare it with Na2O to correct carbonate, that is, CaO * =CaO–P2O5×10 / 3. If the remaining number of moles is less than the number of moles of Na2O, it can be used as CaO * , otherwise CaO * is equal to Na2O;

[0032] S3.2: Calculate the chemical alteration index CIA of various samples based on the corrected carbonate and Na2O. If the CIA result is between 50 - 65, it indicates a primary weathering degree; if it is between 65 - 85, it indicates a medium weathering degree; if it is between 85 - 100, it indicates a high weathering degree; [[ID=??]]

[0033] S3.3: After the judgment is completed, calculate the weathering index WIG of various samples. The smaller the calculated value of the granite weathering index WIG, the higher the degree of weathering and the more thorough the decomposition of the rock. At the same time, based on the principle that the decomposition of silicate minerals causes a large amount of silicon to be leached, while iron and aluminum oxides are relatively enriched, calculate the IOL index of various samples;

[0034] S3.4: According to the calculation results of the IOL index, various samples are classified into kaolinization, weak, medium, and strong laterization classifications, and with the increase of IOL, the degree of laterization becomes stronger.

[0035] As a further solution of the present invention, the specific calculation formula of the chemical alteration index CIA described in S3.2 is as follows:

[0036]

[0037] In the formula, CIA represents the chemical alteration index;

[0038] The specific calculation formula of the granite weathering index WIG described in S3.3 is as follows:

[0039]

[0040] In the formula, WIG represents the granite weathering index;

[0041] The specific calculation formula of the IOL index described in S3.3 is as follows:

[0042]

[0043] In the formula, IOL represents the liquidity index.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] After cleaning the granite outcrop, the method for analyzing the distribution characteristics and restricting factors of rare earth elements in the granite weathering profile collects 31 samples at 10 cm intervals. After air drying, impurity removal, and grinding, they are respectively used for X-ray fluorescence to measure major elements, ICP-MS to measure rare earth elements, and X-ray diffraction to analyze mineral composition. Using Ti as a reference element, calculate the enrichment or depletion degree of elements, and perform normalization analysis based on rare earth grouping and chondrite standards. Calculate the CIA, WIG, and IOL indexes through major elements to judge the weathering degree and laterization classification of samples, which is beneficial to comprehensively master the migration and enrichment behavior of rare earth elements in the vertical profile, effectively eliminate background differences, improve the scientificity of rare earth element behavior comparison between different horizons, reveal the enrichment and distribution mechanism of rare earth elements under medium weathering degree, and help judge mineral stability. Brief Description of the Drawings

[0046] The accompanying drawings are used to provide a further understanding of the present invention and form a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation to the present invention.

[0047] Figure 1 It is a flowchart of the analysis method for the distribution characteristics and restrictive factors of rare earth elements in the granite weathering profile proposed by the present invention. Detailed implementation manners

[0048] Refer to Figure 1 , for the analysis method of the distribution characteristics and restrictive factors of rare earth elements in the granite weathering profile, the specific steps of this analysis method are as follows:

[0049] Record the layering situation of the granite weathering profile and collect and analyze samples of each layer.

[0050] Specifically, after removing the surface floating soil of the outcropping granite profile, continuous sampling was carried out at 10-cm intervals from the top to the bottom of the granite profile, and a total of 31 samples were collected. Among them, there were 4 samples in layer A, marked as ND01 to ND04 respectively; 18 samples in layer B, marked as ND05 to ND22 respectively; and 9 samples in layer C, marked as ND23 to ND31 respectively. After the collected samples of each group were air-dried naturally, the excess plant roots in the samples were picked out, and then the dried samples were ground in an agate mortar to less than 200 meshes. 4 g of sample powders of layer A, layer B, and layer C were weighed respectively. The sample powders of each layer were placed in a tablet press in turn, and boric acid was used as an adhesive. The pressure in the tablet press was increased to 30 t, and the weighed sample powders of each layer were pressed into smooth sample wafers. An X-ray fluorescence spectrometer was used to obtain the percentage content of major elements in each sample wafer, and the results were expressed in the form of elemental oxides. 40 mg of sample powders of layer A, layer B, and layer C were weighed respectively and placed in a Teflon sealed digestion tank, and 0.3 mL of nitric acid and 1 mL of hydrofluoric acid were added. After mixing and sealing, the Teflon sealed digestion tank was placed in an environment at 120 °C for digestion for 24 h. After digestion was completed, the Teflon sealed digestion tank was opened and evaporated to dryness. After evaporation to dryness, 0.3 mL of nitric acid, 1 mL of hydrofluoric acid, and 0.5 mL of perchloric acid were added to the Teflon sealed digestion tank again, and then it was sealed and heated at 120 °C to dissolve all minerals. After the sample dissolution was completed, transfer and volume fixation were carried out. Then, an ELEMENT XR high-resolution inductively coupled plasma mass spectrometer was used to perform parallel sample analysis and standard substance determination on each layer of samples. The working voltage of the X-ray diffractometer was set at 40 Kv, the working current was set at 40 Ma, copper target radiation was used, and according to the parameter settings of a scanning range from 5° to 80° and a scanning speed of 3° / min, each sample wafer was scanned to generate a corresponding scanning pattern. Then, the experimentally measured patterns were smoothed, background subtracted, peak searched, and phase retrieved in turn through MDIJADE 9.0 software, and the K-value method was used for semi-quantitative calculation of the mineral content.

[0051] It should be further noted that the stratification of the granite weathering profile specifically includes the surface soil layer A, the weathered layer B, and the parent material layer C;

[0052] Among them, the A layer ranges from 0 to 30 cm below the ground surface, with a brightness L* of 59.30 - 63.08, a redness a* of 9.21 - 11.39, and a yellowness b* of 24.61 - 27.95. The top of the A layer is a brown humus layer, containing a small amount of plant roots, with a loose structure and fine particle size. The B layer ranges from 30 to 210 cm below the ground surface, with a brightness L* of 61.39 - 65.50, a redness a* of 11.31 - 14.22, and a yellowness b* of 28.40 - 30.75. The B layer is red and soil-like, with fine particles, relatively compact texture, and no original rock structure. The C layer ranges from 210 to 300 cm below the ground surface, with a brightness L* of 65.78 - 67.51, a redness a* of 9.17 - 10.63, and a yellowness b* of 27.34 - 28.59. The color of the C layer gradually transitions from red to yellowish-brown, with a compact texture, containing a gravel structure, and the original rock morphology can be seen, presenting a semi-rock and semi-soil state.

[0053] Analyze the enrichment degree of elements in each sample and evaluate the weathering degree of each sample.

[0054] Specifically, select the stable element Ti as the reference element, and then collect the content information of the reference element and major elements in various samples obtained through experiments. Then, based on the content of major elements and the reference element, calculate the corresponding Δ value. If the Δ value is positive, it indicates that the element in the weathering crust is enriched relative to the bedrock; if the Δ value is negative, it indicates that the element in the weathering crust is depleted relative to the bedrock. Divide the rare earth elements into 2 - 3 groups. Among them, from lanthanum La to europium Eu is the light rare earth group, from samarium Sm to holmium Ho is the middle rare earth group, and from gadolinium Gd to lutetium Lu is the heavy rare earth group. Then, standardize various samples with chondrites, and indicate the migration and enrichment of rare earth elements in the profile by calculating the enrichment factor of various samples relative to the bedrock.

[0055] Specifically, correct CaO in phosphate with P2O5, and then compare and correct carbonate with Na2O, that is, CaO * = CaO–P2O5×10 / 3. If the remaining number of moles is less than the number of moles of Na2O, it can be used as CaO * , otherwise CaO *Equal to Na2O, calculate the Chemical Index of Alteration (CIA) for various samples based on the corrected carbonates and Na2O. If the CIA result is between 50 and 65, it indicates a low degree of weathering; if it is between 65 and 85, it indicates a moderate degree of weathering; if it is between 85 and 100, it indicates a high degree of weathering. After the judgment is completed, calculate the Weathering Index of Granite (WIG) for various samples. The smaller the calculated value of the Weathering Index of Granite (WIG), the higher the degree of weathering and the more complete the rock decomposition. At the same time, based on the principle that the decomposition of silicate minerals causes a large loss of silicon and the relative enrichment of iron and aluminum oxides, calculate the IOL index for various samples. Various samples are classified into kaolinization, weak, moderate, and strong laterization categories according to the calculated results of the IOL index, and the degree of laterization increases with the increase of IOL.

[0056] It should be further noted that the specific calculation formula of the Δ value is as follows:

[0057]

[0058] In the formula, X s represents the content of the element to be measured in the sample; X rock represents the content of the reference element in the sample; I s represents the content of the element to be measured in the bedrock; I rock represents the content of the reference element in the bedrock;

[0059] The specific calculation formula of the enrichment factor is as follows:

[0060]

[0061] In the formula, EF; [REE / Ti] sample represents the normalized difference between the content of rare earth elements REE and the content of Ti in the sample; [REE / Ti] rock represents the normalized difference between the content of rare earth elements REE and the content of Ti in the bedrock;

[0062] The specific calculation formula of the Chemical Index of Alteration (CIA) is as follows:

[0063]

[0064] In the formula, CIA represents the Chemical Index of Alteration;

[0065] The specific calculation formula of the Weathering Index of Granite (WIG) described in S3.3 is as follows:

[0066]

[0067] In the formula, WIG represents the Weathering Index of Granite;

[0068] The specific calculation formula of the IOL index is as follows:

[0069]

[0070] In the formula, IOL represents the liquidity index.

[0071] Record the contents of major elements and weathering characteristics in each sample.

[0072] Based on the recorded results, analyze the influencing factors of the migration and enrichment of rare earth elements in various granite weathering crusts.

Claims

1. Method for analyzing distribution characteristics and restrictive factors of rare earth elements in granite weathering profile, characterized in that, The specific steps of this analysis method are as follows: Ⅰ. Record the stratification of the granite weathering profile and collect and analyze samples from each layer; Ⅱ. Analyze the element enrichment degree in each sample and evaluate the weathering degree of each sample; Ⅲ. Record the content of major elements and weathering characteristics in each sample; Ⅳ. Based on the recorded results, analyze the influencing factors of rare earth element migration and enrichment in various granite weathering crusts.

2. The method for analyzing the distribution characteristics and restricting factors of rare earth elements in the granite weathering profile according to claim 1, wherein The stratification of the granite weathering profile described in step Ⅰ specifically includes the topsoil layer A, the weathered layer B, and the parent material layer C; Among them, the range of layer A is from the ground surface to 0 - 30 cm downward, the brightness L* is 59.30 - 63.08, the redness a* is 9.21 - 11.39, the yellowness b* is 24.61 - 27.95, and the top of layer A is a brown humus layer, containing a small amount of plant roots, with a loose structure and fine particle size; The range of layer B is from the ground surface to 30 - 210 cm downward, the brightness L* is 61.39 - 65.50, the redness a* is 11.31 - 14.22, the yellowness b* is 28.40 - 30.75, and layer B is red and earthy, with fine particles, relatively compact texture, and no original rock structure; The range of layer C is from the ground surface to 210 - 300 cm downward, the brightness L* is 65.78 - 67.51, the redness a* is 9.17 - 10.63, the yellowness b* is 27.34 - 28.59, and the color of layer C gradually transitions from red to yellowish-brown, with a compact texture, containing a gravel structure, visible original rock morphology, and being semi-rock and semi-soil.

3. The method for analyzing the distribution characteristics and influencing factors of rare earth elements in the granite weathering profile according to claim 2, wherein, The specific steps of collecting and analyzing weathering samples from each layer described in step Ⅰ are as follows: S1.1: After removing the surface floating soil of the outcropping granite profile, continuously sample at intervals of 10 cm from the top to the bottom of the granite profile, and a total of 31 samples are collected. Among them, 4 samples from layer A are respectively marked as ND01 - ND04, 18 samples from layer B are respectively marked as ND05 - ND22, and 9 samples from layer C are respectively marked as ND23 - ND31. Then, after the collected samples in each group are naturally air-dried, pick out the excess plant roots in the samples, and then grind the dried samples with an agate mortar to less than 200 meshes; S1.2: Weigh 4 g of sample powders from layer A, layer B, and layer C respectively. Place the sample powders of each layer into a tablet press in turn, and then use boric acid as a binder. Pressurize the tablet press to 30 t to press the weighed sample powders of each layer into smooth sample discs. Use an X-ray fluorescence spectrometer to obtain the percentage content of major elements in each sample disc, and express the results in the form of elemental oxides; S1.3: Weigh 40 mg of sample powders from layer A, layer B, and layer C respectively, and place them in Teflon sealed digestion tanks respectively. Add 0.3 mL of nitric acid and 1 mL of hydrofluoric acid. After mixing and sealing, place the Teflon sealed digestion tanks in an environment of 120 °C for digestion for 24 h. After digestion is completed, open the Teflon sealed digestion tanks and evaporate to dryness; S1.4: After opening the can and evaporating to dryness, add 0.3 mL of nitric acid, 1 mL of hydrofluoric acid, and 0.5 mL of perchloric acid into the Teflon sealed digestion tank again, and then place it in a sealed state for heating at 120 °C to dissolve all minerals. After the sample dissolution is completed, transfer and make up the volume, and then use the ELEMENT XR high-resolution inductively coupled plasma mass spectrometer to conduct parallel sample analysis and standard substance determination on each layer of samples respectively; S1.5: Set the working voltage of the X-ray diffractometer to 40 Kv, the working current to 40 Ma, use copper target radiation, and scan each sample wafer according to the parameter settings of a scanning range from 5° to 80° and a scanning speed of 3° / min to generate corresponding scanning spectra. Then, use the MDI JADE 9.0 software to smooth, background subtract, peak search, and phase retrieval the experimentally measured spectra in sequence, and use the K-value method to conduct semi-quantitative calculation of the mineral content.

4. The method for analyzing the distribution characteristics and restrictive factors of rare earth elements in the weathered profile of granite according to claim 3, wherein The specific steps for analyzing the element enrichment degree in each sample described in Step II are as follows: S2.1: Select the stable element Ti as the reference element, and then collect the content information of the reference element and major elements in various samples obtained through experiments. After that, calculate the corresponding Δ value based on the major element content and the reference element; S2.2: If the Δ value is positive, it indicates that the element in the weathered crust is enriched relative to the bedrock. If the Δ value is negative, it indicates that the element in the weathered crust is depleted relative to the bedrock; S2.3: Divide the rare earth elements into 2 - 3 groups. Among them, from lanthanum La to europium Eu is the light rare earth group, from samarium Sm to holmium Ho is the middle rare earth group, and from gadolinium Gd to lutetium Lu is the heavy rare earth group. Then, standardize various samples using chondrites, and indicate the migration and enrichment of rare earth elements in the profile by calculating the enrichment factor of various samples relative to the bedrock.

5. The method for analyzing the distribution characteristics and restrictive factors of rare earth elements in the granite weathering profile according to claim 4, wherein The specific calculation formula for the Δ value described in S2.1 is as follows: Wherein, X s represents the content of the element to be measured in the sample; X rock represents the content of the reference element in the sample; I s represents the content of the element to be measured in the bedrock; I rock represents the content of the reference element in the bedrock; The specific calculation formula for the enrichment factor described in S2.1 is as follows: In the formula, EF; [REE / Ti] sample Represents the normalized difference between the REE content and the Ti content in the sample; [REE / Ti] rock Represents the normalized difference between the REE content and the Ti content in the bedrock.

6. The method for analyzing the distribution characteristics and restrictive factors of rare earth elements in the granite weathering profile according to claim 4, characterized in that The specific steps for evaluating the weathering degree of each sample described in Step II are as follows: S3.1: Calibrate CaO in phosphate with P2O5, and then compare it with Na2O to calibrate carbonate, i.e., CaO * = CaO – P2O5 × 10 / 3. If the remaining number of moles is less than the number of moles of Na2O, it can be used as CaO * , otherwise CaO * is equal to Na2O; S3.2: Calculate the chemical alteration index CIA of various samples based on the corrected carbonate and Na2O. If the CIA result is between 50 - 65, it indicates a primary weathering degree. If it is between 65 - 85, it indicates a moderate weathering degree. If it is between 85 - 100, it indicates a high weathering degree; S3.3: After the judgment is completed, calculate the weathering index of granite WIG for various samples. When the calculated result value of the granite weathering index WIG is smaller, it represents a higher weathering degree and more thorough rock decomposition. At the same time, based on the principle that the decomposition of silicate minerals causes a large amount of silicon leaching and the relative enrichment of iron and aluminum oxides, calculate the IOL index of various samples; S3.4: Various samples are divided into classifications of kaolinization, weak, moderate, and strong laterization according to the calculated results of the IOL index, and with the increase of IOL, the laterization degree becomes stronger.

7. The method for analyzing the distribution characteristics and restrictive factors of rare earth elements in the granite weathering profile according to claim 6, wherein The specific calculation formula for the chemical alteration index CIA described in S3.2 is as follows: In the formula, CIA represents the chemical alteration index; The specific calculation formula for the weathering index of granite WIG described in S3.3 is as follows: In the formula, WIG represents the granite weathering index; The specific calculation formula of the IOL index described in S3.3 is as follows: In the formula, IOL represents the liquidity index.

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