Dating method for indissolvable mineral fluorite

Abstract

The invention provides a dating method of indissolvable mineral fluorite, which is characterized in that boric acid and hydrochloric acid are directly used for digesting a natural fluorite sample, the content of Sm and Nd in the natural fluorite sample and the isotope ratio of 143Nd / 144Nd are measured, and then the age of the fluorite sample is determined. A natural fluorite sample of a Bayan Obo rare earth deposit in Inner Mongolia is selected, the selected fluorite particles are digested, separated and measured by the method, and the obtained age is consistent with the total rock data in an error range, so that the fluorite dating method disclosed by the invention is proved to be simple to operate, relatively low in cost, relatively high in precision and reliable in result; popularization and application are facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of mineral dating, and particularly relates to a dating method for refractory mineral fluorite. Background Art

[0002] Fluorite, also known as fluorspar, is a strategic emerging mineral in China and is widely used in fields such as new energy, new materials, national defense and military, fluorine chemical industry, metallurgy, and building materials. It can occur independently in nature or as gangue minerals in many metal and non-metal ore deposits, and is a non-metallic mineral resource of strategic significance.

[0003] For the dating of fluorite, common methods include radioactive isotope dating, thermoluminescence dating, and fluorine content dating. Among them, thermoluminescence dating and fluorine content dating are relatively simple to operate compared with radioactive isotope dating, but their accuracy is relatively low. Radioactive isotope dating methods include: ① Uranium-lead (U-Pb) isotope dating method: high accuracy, but complex operation process and high cost, not suitable for large-scale sample analysis; ② Rubidium-strontium (Rb-Sr) isotope dating method: relatively simple to operate compared with uranium-lead dating, but its closed system is easily affected by the external environment and has low accuracy; ③ Potassium-argon (K-Ar) isotope dating method: a commonly used geological dating method applicable to various minerals, but the samples are easily affected by late hydrothermal activities, and the obtained ages generally have multiple solutions, not suitable for precise dating of fluorite; ④ (U-Th) / He method: a newly emerging fluorite dating method in recent years, currently in the stage of exploration and development, not widely used yet, and its accuracy and reliability need to be further verified; ⑤ Samarium-neodymium (Sm-Nd) isotope dating method: the system is easy to maintain its closure, has strong weathering resistance and alteration resistance, and is widely used in the dating of hydrothermal deposits.

[0004] Although natural fluorite samples are calcium fluoride with relatively high purity, a small amount of terrigenous clastic materials (mainly composed of silicate and clay minerals) are inevitably enclosed during their growth process. The traditional sample dissolution method (nitric acid + hydrofluoric acid + perchloric acid) is basically ineffective for digesting fluorite. The large amount of fluoride ions in the solution will inhibit the digestion of calcium fluoride and bring some elemental information of the clastic materials and clay minerals into the digestion solution, affecting the subsequent experimental results. Therefore, the present invention considers using boric acid solution to replace the traditional method for digesting fluorite.

[0005] The digestion of fluorite by the boric acid method is an unconventional method. In previous studies, boric acid was mostly used to eliminate the calcium fluoride precipitate formed passively due to the high calcium content in the traditional digestion method, and boric acid was not directly used to digest natural fluorite minerals. CN117571409A discloses a sample dissolution method for Sm-Nd isotope testing of fluorite ore. First, fluorite is preliminarily dissolved with reverse aqua regia under heating conditions, and then a mixed acid of nitric acid and boric acid is added for further dissolution, so as to achieve the full dissolution of fluorite and form a clear solution for subsequent detection. However, there are still problems of complex operation process and high cost. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a dating method for insoluble mineral fluorite in view of the above-mentioned deficiencies of the prior art, directly using the digestion method of boric acid + hydrochloric acid to digest natural fluorite samples and determine their Sm-Nd isotope composition.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: a dating method for insoluble mineral fluorite, comprising the following steps: S1. Sample digestion Weigh a natural fluorite sample and place it in a polytetrafluoroethylene container, add hydrochloric acid solution and boric acid solution, place it on a hot plate at a temperature of 100-110°C for 20-30 hours, then open the lid and evaporate the sample to dryness, and repeat the digestion once with hydrochloric acid solution and boric acid solution to achieve complete digestion; centrifuge the digested fluorite sample to obtain a sample solution, and divide the sample solution into two parts: one part is used for the determination of Sm and Nd contents, and the other part is used for 143 Nd / 144 Nd isotope ratio determination; S2. Sm and Nd content determination Take the sample solution obtained in S1 and use the ion exchange method to separate and purify Sm and Nd isotopes, and use a thermal ionization mass spectrometer to determine the Sm and Nd contents; S3. 143 Nd / 144 Nd isotope ratio determination Take the sample solution obtained in S1 and use the ion exchange method to separate and purify Nd isotopes, and use a multi-receiver inductively coupled plasma mass spectrometer to determine 143 Nd / 144 Nd ratio; S4. Dating According to the Sm and Nd contents measured in S2 and the 143 Nd / 144 Nd ratio measured in S3, determine the isochron age of the fluorite sample.

[0008] Preferably, the particle size of the natural fluorite sample in S1 is 40-80 mesh.

[0009] Preferably, the concentration of the hydrochloric acid solution in S1 is 5.9 - 6.1 mol / L.

[0010] Preferably, the concentration of the boric acid solution in S1 is 0.8 - 0.85 mol / L.

[0011] Preferably, the ratio of the natural fluorite sample to the hydrochloric acid solution and the boric acid solution in S1 is 0.05 - 0.25 g : 3 - 5 mL : 3 - 8 mL.

[0012] Preferably, the centrifugation conditions in S1 are: centrifuging at a rotational speed of 3000 - 5000 r / min for 5 - 8 minutes.

[0013] Preferably, the method for separating and purifying Sm and Nd isotopes by ion exchange method in S2 is: adding the sample solution to be measured into an ion exchange column filled with cation resin AG50W×8 (H + ), eluting with a hydrochloric acid solution with a concentration of 4 mol / L, receiving the Sm and Nd collecting solutions, and evaporating to dryness for measurement.

[0014] Preferably, the method for separating and purifying Nd isotopes by ion exchange method in S3 is: adding the sample solution to be measured into an ion exchange column filled with cation resin AG50W×8 (H + ), eluting with a hydrochloric acid solution with a concentration of 4 mol / L, receiving the collecting solution, then adding it to an ion exchange column filled with HDEHP resin, and eluting with a hydrochloric acid solution with a concentration of 0.2 mol / L to obtain a Nd isotope enrichment solution for measurement.

[0015] The present invention has the following remarkable technical effects compared with the prior art: 1. The present invention provides a dating method for refractory mineral fluorite, directly using the digestion method of boric acid + hydrochloric acid to digest natural fluorite samples, measuring their Sm - Nd isotope composition, and determining the age of the fluorite samples. This method is not only simple to operate, low in cost, but also has high precision, reliable results, and is suitable for popularization and application.

[0016] 2. The present invention selects natural fluorite samples from the Bayan Obo rare earth deposit in Inner Mongolia, digests, separates, and measures the selected fluorite particles by the method of the present invention, and the obtained age is consistent with the whole - rock data within the error range.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0018] Figure 1 is the isochron diagram of the age of the fluorite sample in Example 1 of the present invention; Figure 2 It is the isochron diagram of the age of the fluorite sample in Example 2 of the present invention; Figure 3 It is the isochron diagram of the age of the fluorite sample in Example 3 of the present invention; Figure 4 It is the isochron diagram of the age of the fluorite sample in Example 4 of the present invention. Detailed implementation manners

[0019] The digestion of samples, chemical separation of Sm-Nd isotopes, and mass spectrometry testing of the present invention were carried out in the Isotope Laboratory of the Institute of Geology, Chinese Academy of Geological Sciences. The samples, instruments, and reagents used are as follows: The fluorite samples were selected from natural fluorite samples of the Bayan Obo rare earth deposit in Inner Mongolia; The mass spectrometer used for the determination of the contents of Sm and Nd isotopes was a MAT262 thermal ionization mass spectrometer (Finnigan Company, Germany); 143 Nd / 144 The mass spectrometer used for the determination of the Nd / All chemical reagents used in the experimental process were of electronic pure grade. Hydrochloric acid was purified 2 times through a PFA sub-boiling distiller produced by Savillex Corporation of the United States; the water used in isotope testing, sample digestion, and chemical separation was purified by a pure water machine produced by Elga Company, and the conductivity was better than 18.2 MΩ·cm; boric acid was produced by Fisher Chemical Company with a purity of 99.999%, and was made into a boric acid solution with ultrapure water; the ion exchange resins were AG50W×8 (H + ) cation exchange resin (38 - 74 μm, Bio-Rad Company, United States) and bis(α-ethylhexyl) phosphoric acid + polytetrafluoroethylene powder-coated extraction resin (HDEHP) (Sigma-Aldrich Company).

[0020] Example 1 This example is a dating method for a refractory mineral fluorite. The fluorite sample is from the Early Paleozoic. The fluorite is disseminated, massive, and banded, and is associated with fine-grained dolomite. The sample collection location is the west ore pit of Bayan Obo, with a mining depth of 1774 m. This method specifically includes the following steps: 1. Sample digestion Weigh 0.05 g of natural fluorite sample (60 - 80 mesh) into a polytetrafluoroethylene container, add 3 mL of 6 mol / L hydrochloric acid solution and 3 mL of 0.82 mol / L boric acid solution, place it on an electric hot plate at 100 °C for 24 hours, then open the lid to evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once, and the sample can be completely digested.

[0021] Transfer the digested fluorite sample into a 5 mL centrifuge tube and centrifuge it at 4000 r / min for 6 minutes to obtain a sample solution. Divide the sample solution into two parts: one part of the solution is used for the determination of Sm and Nd contents and analyzed by isotope dilution mass spectrometry; the other part of the solution is used for 143 Nd / 144 the determination of Nd isotope ratio.

[0022] 2. Determination of Sm and Nd Contents Adopt the ion exchange separation method to separate and purify Sm and Nd isotopes. Only one-step separation is carried out. The method is as follows: Add the cation resin AG50W×8 (H + ) into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After cleaning with 50% hydrochloric acid and equilibration with 4 mol / L hydrochloric acid, add 1 mL of the clear solution of the sample to be measured into the exchange column, elute with 4 mol / L hydrochloric acid, receive Sm and Nd, evaporate the collected solution to dryness, and use a thermal ionization mass spectrometer to determine the Sm and Nd contents.

[0023] 3. 143 Nd / 144 Determination of Nd Isotope Ratio Adopt the ion exchange separation method to separate and purify Nd isotopes. The method is as follows: Add the cation resin AG50W×8 (H + ) into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After cleaning with 50% hydrochloric acid and equilibration with 4 mol / L hydrochloric acid, add 1 mL of the clear solution of the sample to be measured into the exchange column, elute with 4 mol / L hydrochloric acid, receive the collected solution, and then add it into an ion exchange column filled with HDEHP resin (inner diameter 0.5 cm, resin height 10 cm), elute with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enriched solution, and use a multi-receiver inductively coupled plasma mass spectrometer to determine the 143 Nd / 144 Nd ratio.

[0024] Table 1 Analysis Results of Sm-Nd Isotopes of Fluorite Samples Plot the measured 143 Nd / 144 Nd and 147 Sm / 144 Nd values on a graph and fit a straight line equation (i.e., isochron). As Figure 1 shown, the isochron age of the fluorite sample in this example is 380 ± 87 Ma (n = 4), 143 Nd / 144The initial Nd ratio is 0.511208 ± 0.000035, MSWD = 0.33. The age measured by this method is consistent with the whole-rock data within the error range. References for the whole-rock data: Zhu Xiangkun, Sun Jian. Rare earth mineralization age and stages of the Bayan Obo deposit in Inner Mongolia. Acta Geoscientica Sinica, 2012, 33(6): 845-856., which systematically summarizes the whole-rock ages of samples in the Bayan Obo area.

[0025] Example 2 This example is a dating method for refractory mineral fluorite. The fluorite sample is from the Mesoproterozoic. The fluorite occurs in veins and is associated with fine-grained dolomite. The sample collection location is the western ore pit of Bayan Obo, with a mining depth of 1650 m. This method specifically includes the following steps: 1. Sample digestion Weigh 0.1 g of natural fluorite sample (60-80 mesh) into a polytetrafluoroethylene container, add 3 mL of 6.1 mol / L hydrochloric acid solution and 3 mL of 0.83 mol / L boric acid solution, place it on a hot plate at 110 °C for 20 hours, then open the lid to evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once, and the sample can be completely digested.

[0026] Transfer the digested fluorite sample to a 5 mL centrifuge tube, centrifuge at 4000 r / min for 7 minutes to obtain a sample solution. Divide the sample solution into two parts: one part of the solution is used for the determination of Sm and Nd contents, and analyzed by isotope dilution mass spectrometry; the other part of the solution is used for 143 Nd / 144 Nd isotope ratio determination.

[0027] 2. Determination of Sm and Nd contents Adopt the ion exchange separation method to separate and purify Sm and Nd isotopes, only perform one-step separation, and the method is: Add cation resin AG50W×8 (H + ) into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After cleaning with 50% hydrochloric acid and equilibration with 4 mol / L hydrochloric acid, add 1 mL of the clear solution of the sample to be measured into the exchange column, elute with 4 mol / L hydrochloric acid, collect Sm and Nd, evaporate the collected solution to dryness, and use a thermal ionization mass spectrometer to determine the Sm and Nd contents.

[0028] 3. 143 Nd / 144 Nd isotope ratio determination Adopt the ion exchange separation method to separate and purify Nd isotopes, and the method is: Add cation resin AG50W×8 (H +Add it into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After cleaning with 50% hydrochloric acid and equilibration with 4 mol / L hydrochloric acid, add 1 mL of the clear solution of the sample to be measured into the exchange column, elute with 4 mol / L hydrochloric acid, collect the eluate, and then add it into an ion exchange column filled with HDEHP resin (inner diameter 0.5 cm, resin height 10 cm), elute with 0.2 mol / L hydrochloric acid to obtain an enriched solution of Nd isotopes, and measure it using a multi-receiver inductively coupled plasma mass spectrometer. 143 Nd / 144 Nd ratio.

[0029] Table 2 Analysis results of Sm-Nd isotopes of fluorite samples The measured 143 Nd / 144 Nd and 147 Sm / 144 Nd values are plotted on the graph, and a linear equation (i.e., isochron) is fitted. As Figure 2 shown, the isochron age of the fluorite sample in this example is 1337 ± 201 Ma (n = 6), 143 Nd / 144 The initial Nd ratio is 0.510880 ± 0.000064, MSWD = 0.86, and the age measured by this method is consistent with the whole-rock data within the error range.

[0030] Example 3 This example is a dating method for refractory mineral fluorite. The fluorite sample is collected from a fluorite mine in Zhejiang Province. The sample is relatively young. The method specifically includes the following steps: 1. Sample digestion Weigh 0.15 g of natural fluorite sample (40 - 60 mesh) into a polytetrafluoroethylene container, add 3 mL of 5.9 mol / L hydrochloric acid solution and 6 mL of 0.8 mol / L boric acid solution, place it on a hot plate at 105 °C for 30 hours, and then open the lid to evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once, and the sample can be completely digested.

[0031] Transfer the digested fluorite sample to a 5 mL centrifuge tube, centrifuge at 3000 r / min for 8 minutes to obtain a sample solution. Divide the sample solution into two parts: one part of the solution is used for the determination of Sm and Nd contents and analyzed by isotope dilution mass spectrometry; the other part of the solution is used for 143 Nd / 144 Nd isotope ratio determination.

[0032] 2. Determination of Sm and Nd contents The ion exchange separation method is adopted to separate and purify Sm and Nd isotopes. Only one-step separation is carried out. The method is as follows: The cation resin AG50W×8 (H + ) is added into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After being washed with 50% hydrochloric acid and balanced with 4 mol / L hydrochloric acid, 1 mL of the clear liquid of the sample to be measured is added into the exchange column and eluted with 4 mol / L hydrochloric acid. After receiving Sm and Nd, the collected liquid is evaporated to dryness, and the contents of Sm and Nd are measured using a thermal ionization mass spectrometer.

[0033] 3. 143 Nd / 144 Nd isotope ratio determination The ion exchange separation method is adopted to separate and purify Nd isotopes. The method is as follows: The cation resin AG50W×8 (H + ) is added into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After being washed with 50% hydrochloric acid and balanced with 4 mol / L hydrochloric acid, 1 mL of the clear liquid of the sample to be measured is added into the exchange column and eluted with 4 mol / L hydrochloric acid. The collected liquid is received and then added into an ion exchange column filled with HDEHP resin (inner diameter 0.5 cm, resin height 10 cm) and eluted with 0.2 mol / L hydrochloric acid to obtain a Nd isotope enriched liquid, and the 143 Nd / 144 Nd ratio is measured using a multi-receiver inductively coupled plasma mass spectrometer.

[0034] Table 3 Sm-Nd isotope analysis results of fluorite samples The measured 143 Nd / 144 Nd and 147 Sm / 144 Nd values are plotted on a graph, and a straight line equation (i.e., isochron) is fitted. As Figure 3 shown, in this embodiment, the isochron age of the fluorite sample is 74.4 ± 9.4 Ma (n = 6), 143 Nd / 144 The initial Nd ratio is 0.511952 ± 0.000032, MSWD = 1.2, and the age measured by this method is consistent with the whole rock data within the error range.

[0035] Example 4 This embodiment is a dating method for a refractory mineral fluorite. The fluorite sample is collected from a fluorite mine in Jiangsu Province. The sample is relatively young. The method specifically includes the following steps: 1. Sample digestion Weigh 0.25 g of natural fluorite sample (40 - 60 mesh) into a polytetrafluoroethylene container, add 5 mL of 6 mol / L hydrochloric acid solution and 8 mL of 0.85 mol / L boric acid solution, place it on an electric hot plate at 102 °C for 27 hours, then open the lid and evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once, and the sample can be completely digested.

[0036] Transfer the digested fluorite sample to a 5 mL centrifuge tube, centrifuge at 5000 r / min for 5 minutes to obtain the sample solution. Divide the sample solution into two parts: one part of the solution is used for the determination of Sm and Nd contents, and analyzed by isotope dilution mass spectrometry; the other part of the solution is used for 143 Nd / 144 Nd isotope ratio determination.

[0037] 2. Determination of Sm and Nd Contents Adopt the ion exchange separation method to separate and purify Sm and Nd isotopes, only perform one-step separation, and the method is as follows: Add cation resin AG50W×8 (H + ) into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After cleaning with 50% hydrochloric acid and equilibration with 4 mol / L hydrochloric acid, add 1 mL of the clear solution of the sample to be measured into the exchange column, elute with 4 mol / L hydrochloric acid, after receiving Sm and Nd, evaporate the collected solution to dryness, and use a thermal ionization mass spectrometer to determine the Sm and Nd contents.

[0038] 3. 143 Nd / 144 Nd Isotope Ratio Determination Adopt the ion exchange separation method to separate and purify Nd isotopes, and the method is as follows: Add cation resin AG50W×8 (H + ) into a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After cleaning with 50% hydrochloric acid and equilibration with 4 mol / L hydrochloric acid, add 1 mL of the clear solution of the sample to be measured into the exchange column, elute with 4 mol / L hydrochloric acid, receive the collected solution, and then add it to an ion exchange column filled with HDEHP resin (inner diameter 0.5 cm, resin height 10 cm), elute with 0.2 mol / L hydrochloric acid to obtain the Nd isotope enrichment solution, and use a multi-receiver inductively coupled plasma mass spectrometer to determine 143 Nd / 144 Nd ratio.

[0039] Table 4 Analysis Results of Sm-Nd Isotopes in Fluorite Samples The measured 143 Nd / 144 Nd and 147 Sm / 144The Nd values are plotted on the graph to fit a straight line equation (i.e., the isochron), as Figure 4 shown. In this embodiment, the isochron age of the fluorite sample is 29.3 ± 4.4|15.7 Ma (n = 5), 143 Nd / 144 the initial Nd ratio is 0.512239 ± 0.0000017|0.000061, MSWD = 4.8, and the age measured by this method is consistent with the whole-rock data within the error range.

[0040] Comparative example When only boric acid is used to digest the natural fluorite sample, it is found that: during the digestion process, the sample will present an expanded colloidal state, and the fluorite particles at the bottom will be separated from the boric acid, affecting the digestion effect. This result proves that adding an appropriate amount of hydrochloric acid can dissolve a part of the non-boron tetrafluoride (the reaction product of boric acid and calcium fluoride at high temperature, unstable and volatile) component while boric acid digests the fluorite sample, so that the fluorite mineral can be in full contact with boric acid, achieving a better reaction effect.

[0041] There are three issues to note during the fluorite digestion process in the present invention: First, boric acid powder is not easily soluble in water at room temperature and needs to be heated and shaken repeatedly; each time the boric acid solution is used, it also needs to be heated and shaken well. Second, the fluorite particles do not change significantly under the leaching of hydrochloric acid + boric acid, and the actual digestion of the sample occurs after opening the lid. Therefore, to ensure complete reaction, the temperature of the hot plate should be appropriately lowered to ensure sufficient digestion time after opening the lid. Third, after evaporation to dryness, the sample is in the form of white powder. After adding hydrochloric acid to dissolve and observing, if there are still a small amount of undigested fluorite particles remaining at the bottom of the vessel, the leaching and digestion process needs to be repeated once to ensure complete digestion of the sample. The ion exchange separation method and the on-machine determination process are the same as those of conventional samples.

[0042] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A dating method for the insoluble mineral fluorite, characterized in that: The following steps are involved: S1. Sample digestion Weigh a natural fluorite sample and place it in a sealed container. Add hydrochloric acid solution and boric acid solution. Heat at 100-110°C for 20-30 hours. Then open the lid and evaporate the sample. Repeat the digestion with hydrochloric acid solution and boric acid solution until complete digestion is achieved. Centrifuge to obtain the sample solution. Determination of S2, Sm and Nd contents The sample solution obtained from S1 was used to separate and purify Sm and Nd isotopes by ion exchange method, and the Sm and Nd contents were determined by thermal ionization mass spectrometry; S3, 143 Nd / 144 Nd isotope ratio determination The sample solution obtained from S1 was separated and purified by ion exchange method, and the Nd isotopes were determined by multi-receiver inductively coupled plasma mass spectrometry. 143 Nd / 144 Nd ratio; S4. Dating According to the Sm and Nd contents measured by S2 and the 143 Nd / 144 The Nd ratio determines the isochron age of the fluorite samples.

2. The method according to claim 1, characterized in that The particle size of the natural fluorite sample described in S1 is 40~80 mesh.

3. The method according to claim 1, characterized in that The concentration of the hydrochloric acid solution in S1 is 5.9-6.1 mol / L.

4. The method according to claim 1, characterized in that: The concentration of the boric acid solution in S1 is 0.8-0.85 mol / L.

5. The method according to claim 1, characterized in that: The ratio of the natural fluorite sample to the hydrochloric acid solution and the boric acid solution described in S1 is 0.05~0.25g:3~5mL:3~8mL.

6. The method according to claim 1, characterized in that The centrifugation conditions described in S1 are: centrifugation at a speed of 3000-5000 r / min for 5-8 minutes.

7. The method according to claim 1, characterized in that The method for separating and purifying Sm and Nd isotopes by ion exchange method described in S2 is as follows: adding the sample solution to be tested into a solution filled with cationic resin AG50W×8 (H + ) was placed in an ion exchange column and eluted with a 4 mol / L hydrochloric acid solution to collect Sm and Nd, and evaporated to dryness for testing.

8. The method according to claim 1, characterized in that The method for separating and purifying Nd isotopes by ion exchange method described in S3 is as follows: adding the sample solution to be tested into a solution filled with cationic resin AG50W×8 (H + ) is added to an ion exchange column, washed and eluted with a hydrochloric acid solution with a concentration of 4 mol / L, the collected liquid is received, and then added to an ion exchange column filled with HDEHP resin, washed and eluted with a hydrochloric acid solution with a concentration of 0.2 mol / L to obtain a Nd isotope enriched solution for testing.

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