A dating method for the insoluble mineral fluorite

Abstract

This invention provides a dating method for the sparingly soluble mineral fluorite. This method directly digests natural fluorite samples using boric acid and hydrochloric acid, and determines the Sm and Nd contents. 143 Nd / 144 The age of fluorite samples is determined by Nd isotope ratios. This invention selects natural fluorite samples from the Bayan Obo rare earth deposit in Inner Mongolia. Selected fluorite particles are digested, separated, and measured using the method described above. The obtained ages are consistent with whole-rock data within the error range, demonstrating that the fluorite dating method of this invention is not only simple to operate and low in cost, but also highly accurate and reliable, making it suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of mineral dating technology, and specifically relates to a dating method for the sparingly soluble mineral fluorite. Background Technology

[0002] Fluorite, also known as fluorite, is a strategic emerging mineral in my country. It is widely used in new energy, new materials, national defense, fluorochemicals, metallurgy, building materials and other fields. It can be produced independently in nature or as gangue minerals in many metallic and non-metallic mineral deposits. It is a non-metallic mineral resource of strategic significance.

[0003] Commonly used methods for dating fluorite include radiometric dating, thermoluminescence dating, and fluorine content dating. Among these, thermoluminescence dating and fluorine content dating are simpler to operate than radiometric dating, but their accuracy is relatively lower. Radiometric dating methods include: ① Uranium-lead (U-Pb) isotope dating: high accuracy, but complex operation and high cost, unsuitable for large-scale sample analysis; ② Rubidium-strontium (Rb-Sr) isotope dating: relatively simple operation compared to uranium-lead dating, but its closed system is easily affected by the external environment, resulting in lower accuracy; ③ Potassium-argon (K-Ar) isotope dating: a commonly used geological dating method applicable to various minerals, but samples are easily affected by later hydrothermal activity, and the obtained ages generally have multiple interpretations, making it unsuitable for precise dating of fluorite; ④ (U-Th) / He method: a newly emerging fluorite dating method in recent years, currently in the exploration and development stage, not yet widely used, and its accuracy and reliability need further verification; ⑤ Samarium-neodymium (Sm-Nd) isotope dating: the system is easy to maintain its closed nature, has strong resistance to weathering and alteration, and is widely used in hydrothermal deposit dating.

[0004] Although natural fluorite samples are high-purity calcium fluoride, their growth inevitably involves a small amount of terrigenous debris (mainly silicates and clay minerals). Traditional dissolution methods (nitric acid + hydrofluoric acid + perchloric acid) are largely ineffective in digesting fluorite. The abundant fluoride ions in the solution inhibit the digestion of calcium fluoride and introduce some elemental information from the debris and clay minerals into the digestion solution, affecting subsequent experimental results. Therefore, this invention considers using boric acid solution as an alternative to traditional methods for digesting fluorite.

[0005] Boric acid leaching for fluorite digestion is an unconventional method. Previous studies have used boric acid primarily to eliminate calcium fluoride precipitates passively formed due to high calcium content in traditional digestion methods, rather than directly digesting natural fluorite minerals. CN117571409A discloses a sample dissolution method for Sm-Nd isotope testing of fluorite ore. This method involves first initially dissolving the fluorite with aqua regia under heating conditions, then adding a mixture of nitric acid and boric acid for further dissolution, thus achieving complete dissolution of the fluorite and forming a clear solution for subsequent analysis. However, this method still suffers from complex operation 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 the sparingly soluble mineral fluorite, which directly uses boric acid + hydrochloric acid digestion method to digest natural fluorite samples and determine their Sm-Nd isotopic composition.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a dating method for the sparingly soluble mineral fluorite, comprising the following steps:

[0008] S1, Sample digestion

[0009] Weigh a natural fluorite sample and place it in a polytetrafluoroethylene container. Add hydrochloric acid solution and boric acid solution, and place it on a hot plate at 100-110℃ for 20-30 hours. Then, open the container and evaporate the sample to dryness. Repeat the digestion process once more with hydrochloric acid solution and boric acid solution to achieve complete digestion. Centrifuge the digested fluorite sample to obtain a sample solution. Divide the sample solution into two parts: one part for the determination of Sm and Nd content, and the other part for... 143 Nd / 144 Nd isotope ratio determination;

[0010] Determination of S2, Sm and Nd content

[0011] The Sm and Nd isotopes in the sample solution obtained from S1 were separated and purified by ion exchange method, and the contents of Sm and Nd were determined by thermal ionization mass spectrometry.

[0012] S3 143 Nd / 144 Nd isotope ratio determination

[0013] The Nd isotopes in the sample solution obtained from S1 were separated and purified by ion exchange, and then analyzed by multi-receiver inductively coupled plasma mass spectrometry. 143 Nd / 144 Nd ratio;

[0014] S4. Dating

[0015] Based on the Sm and Nd contents measured in S2 and the contents measured in S3143 Nd / 144 The Nd ratio determines the isochron age of fluorite samples.

[0016] Preferably, the particle size of the natural fluorite sample in S1 is 40-80 mesh.

[0017] Preferably, the concentration of the hydrochloric acid solution in S1 is 5.9~6.1 mol / L.

[0018] Preferably, the concentration of the boric acid solution in S1 is 0.8~0.85 mol / L.

[0019] Preferably, the ratio of the natural fluorite sample to the hydrochloric acid solution and the boric acid solution in S1 is 0.05~0.25g:3~5mL:3~8mL.

[0020] Preferably, the centrifugation conditions in S1 are: centrifugation at 3000~5000 r / min for 5~8 minutes.

[0021] Preferably, the method for separating and purifying Sm and Nd isotopes by ion exchange as described in S2 is as follows: the sample solution to be tested is added to a container filled with cation exchange resin AG50W×8 (H + In an ion exchange column, the solution was eluted with 4 mol / L hydrochloric acid solution, and the collected Sm and Nd solutions were collected, evaporated to dryness, and then analyzed.

[0022] Preferably, the method for separating and purifying Nd isotopes by ion exchange as described in S3 is as follows: the sample solution to be tested is added to a container filled with cation exchange resin AG50W×8 (H + The solution was eluted with 4 mol / L hydrochloric acid in an ion exchange column, and the collected solution was then added to an ion exchange column packed with HDEHP resin and eluted with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enrichment solution for analysis.

[0023] Compared with the prior art, the present invention has the following significant technical effects:

[0024] 1. This invention provides a dating method for the sparingly soluble mineral fluorite. The natural fluorite sample is digested directly using a boric acid + hydrochloric acid digestion method, and its Sm-Nd isotopic composition is determined to identify the age of the fluorite sample. This method is not only simple to operate and low in cost, but also highly accurate and reliable, making it suitable for widespread application.

[0025] 2. In this invention, natural fluorite samples from the Bayan Obo rare earth deposit in Inner Mongolia are selected. The selected fluorite particles are digested, separated, and measured using the method of this invention. The resulting age is consistent with the whole-rock data within the error range.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is an isochronous plot of the age of the fluorite sample in Example 1 of this invention;

[0028] Figure 2 This is an isochronous plot of the age of the fluorite sample in Example 2 of this invention;

[0029] Figure 3 This is an isochronous plot of the age of the fluorite sample in Example 3 of the present invention;

[0030] Figure 4 This is an isochronous plot of the age of the fluorite sample in Example 4 of this invention. Detailed Implementation

[0031] The digestion of samples and the chemical separation and mass spectrometry analysis of Sm-Nd isotopes in this invention were carried out at the Isotope Laboratory of the Institute of Geology, Chinese Academy of Geological Sciences. The samples, instruments and reagents used are as follows:

[0032] Fluorite samples were selected from natural fluorite samples from the Bayan Obo rare earth deposit in Inner Mongolia.

[0033] The mass spectrometer used for determining the Sm and Nd isotope content was a MAT262 thermal ionization mass spectrometer (Finnigan GmbH, Germany). 143 Nd / 144 The mass spectrometer used for determining the Nd isotope ratio was a Nu Plasma II multi-receiver inductively coupled plasma mass spectrometer (Nu Instruments, UK).

[0034] All chemical reagents used in the experiment were electronically pure. Hydrochloric acid was purified twice using a PFA sub-boiling still manufactured by Savilex, USA. Water used in isotope testing, sample digestion, and chemical separation was purified using an Elga water purifier, achieving a conductivity better than 18.2 MΩ·cm. Boric acid was produced by Fisher Chemical with a purity of 99.999%, and a boric acid solution was prepared using ultrapure water. The ion exchange resin was AG50W×8 (H2O). + Cation exchange resin (38~74μm, Bio-Rad, USA) and di(α-ethylhexyl) orthophosphoric acid + polytetrafluoroethylene powder-coated extraction resin (HDEHP) (Sigma-Aldrich).

[0035] Example 1

[0036] This embodiment describes a dating method for the sparingly soluble mineral fluorite. The fluorite sample is from the Early Paleozoic era and occurs in disseminated, massive, and banded forms, associated with fine-grained dolomite. The sample was collected from the Bayan Obo West Mine at a depth of 1774m. The method specifically includes the following steps:

[0037] 1. Sample digestion

[0038] 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 on a hot plate at 100℃ for 24 hours, then open the lid and evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once more to achieve complete digestion of the sample.

[0039] The digested fluorite sample was transferred to a 5 mL centrifuge tube and centrifuged at 4000 rpm for 6 minutes to obtain the sample solution. The sample solution was divided into two portions: one portion was used for Sm and Nd content determination using isotope dilution mass spectrometry; the other portion was used for… 143 Nd / 144 Determination of Nd isotope ratios.

[0040] 2. Determination of Sm and Nd content

[0041] Sm and Nd isotopes were separated and purified using an ion exchange separation method, which involved only one step. The method was as follows: AG50W×8 (H) cation exchange resin was used for the separation and purification of Sm and Nd isotopes. + The sample was added to a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After washing with 50% hydrochloric acid and equilibrating with 4 mol / L hydrochloric acid, 1 mL of the sample supernatant was added to the exchange column and eluted with 4 mol / L hydrochloric acid. After receiving Sm and Nd, the collected solution was evaporated to dryness and the contents of Sm and Nd were determined using a thermal ionization mass spectrometer.

[0042] 3. 143 Nd / 144 Nd isotope ratio determination

[0043] The Nd isotopes were separated and purified using an ion exchange separation method. The method was as follows: AG50W×8 (H) cation exchange resin was used to separate and purify Nd isotopes. + The sample was added to a quartz ion exchange column (0.6 cm inner diameter, 25 cm resin height), washed with 50% hydrochloric acid and equilibrated with 4 mol / L hydrochloric acid. 1 mL of the supernatant sample was added to the column, eluted with 4 mol / L hydrochloric acid, and the collected solution was then added to an ion exchange column packed with HDEHP resin (0.5 cm inner diameter, 10 cm resin height) and eluted with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enrichment solution. This solution was then analyzed using a multi-detector inductively coupled plasma mass spectrometry (ICP-MS). 143 Nd / 144 Nd ratio.

[0044] Table 1. Sm-Nd isotope analysis results of fluorite samples

[0045]

[0046] The measured 143 Nd / 144 Nd and 147 Sm / 144 By plotting the Nd values ​​on a graph and fitting a straight line equation (i.e., an isochronous line), as shown... Figure 1 As shown, the isochron age of the fluorite sample in this embodiment is 380±87 Ma (n=4). 143 Nd / 144 The initial Nd ratio was 0.511208±0.000035, and MSWD=0.33. The age obtained by this method is consistent with the whole-rock data within the error range. Reference for whole-rock data: Zhu Xiangkun, Sun Jian. Rare earth mineralization ages and periods in the Bayan Obo deposit in Inner Mongolia. Acta Geologica Sinica, 2012, 33(6):845-856. This article provides a relatively systematic summary of the whole-rock ages of samples from the Bayan Obo area.

[0047] Example 2

[0048] This embodiment describes a dating method for the sparingly soluble mineral fluorite. The fluorite sample is from the Mesoproterozoic era, occurring in veins associated with fine-grained dolomite. The sample was collected from the Bayan Obo West Mine at a depth of 1650m. The method specifically includes the following steps:

[0049] 1. Sample digestion

[0050] Weigh 0.1g of natural fluorite sample (60-80 mesh) into a polytetrafluoroethylene container, add 3mL of 6.1mol / L hydrochloric acid solution and 3mL of 0.83mol / L boric acid solution, place on a hot plate at 110℃ for 20 hours, then open the lid and evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once more to achieve complete digestion of the sample.

[0051] The digested fluorite sample was transferred to a 5 mL centrifuge tube and centrifuged at 4000 rpm for 7 minutes to obtain the sample solution. The sample solution was divided into two portions: one portion was used for Sm and Nd content determination using isotope dilution mass spectrometry; the other portion was used for… 143 Nd / 144 Determination of Nd isotope ratios.

[0052] 2. Determination of Sm and Nd content

[0053] Sm and Nd isotopes were separated and purified using an ion exchange separation method, which involved only one step. The method was as follows: AG50W×8 (H) cation exchange resin was used for the separation and purification of Sm and Nd isotopes. + The sample was added to a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After washing with 50% hydrochloric acid and equilibrating with 4 mol / L hydrochloric acid, 1 mL of the sample supernatant was added to the exchange column and eluted with 4 mol / L hydrochloric acid. After receiving Sm and Nd, the collected solution was evaporated to dryness and the contents of Sm and Nd were determined using a thermal ionization mass spectrometer.

[0054] 3. 143 Nd / 144 Nd isotope ratio determination

[0055] The Nd isotopes were separated and purified using an ion exchange separation method. The method was as follows: AG50W×8 (H) cation exchange resin was used to separate and purify Nd isotopes. + The sample was added to a quartz ion exchange column (0.6 cm inner diameter, 25 cm resin height), washed with 50% hydrochloric acid and equilibrated with 4 mol / L hydrochloric acid. 1 mL of the supernatant sample was added to the column, eluted with 4 mol / L hydrochloric acid, and the collected solution was then added to an ion exchange column packed with HDEHP resin (0.5 cm inner diameter, 10 cm resin height) and eluted with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enrichment solution. This solution was then analyzed using a multi-detector inductively coupled plasma mass spectrometry (ICP-MS). 143 Nd / 144 Nd ratio.

[0056] Table 2. Sm-Nd isotope analysis results of fluorite samples

[0057]

[0058] The measured 143 Nd / 144 Nd and 147 Sm / 144 By plotting the Nd values ​​on a graph and fitting a straight line equation (i.e., an isochronous line), as shown... Figure 2 As shown, the isochron age of the fluorite sample in this embodiment is 1337±201 Ma (n=6). 143 Nd / 144 The initial Nd ratio was 0.510880±0.000064, and MSWD=0.86. The age obtained by this method is consistent with the whole-rock data within the error range.

[0059] Example 3

[0060] This embodiment describes a dating method for the sparingly soluble mineral fluorite. The fluorite sample was collected from a fluorite mine in Zhejiang Province and is relatively young. The method specifically includes the following steps:

[0061] 1. Sample digestion

[0062] Weigh 0.15g of natural fluorite sample (40-60 mesh) into a polytetrafluoroethylene container, add 3mL of 5.9mol / L hydrochloric acid solution and 6mL of 0.8mol / L boric acid solution, place on a hot plate at 105℃ for 30 hours, then open the lid and evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once more to achieve complete digestion of the sample.

[0063] The digested fluorite sample was transferred to a 5 mL centrifuge tube and centrifuged at 3000 rpm for 8 minutes to obtain the sample solution. The sample solution was divided into two portions: one portion was used for Sm and Nd content determination using isotope dilution mass spectrometry; the other portion was used for… 143 Nd / 144 Determination of Nd isotope ratios.

[0064] 2. Determination of Sm and Nd content

[0065] Sm and Nd isotopes were separated and purified using an ion exchange separation method, which involved only one step. The method was as follows: AG50W×8 (H) cation exchange resin was used for the separation and purification of Sm and Nd isotopes. + The sample was added to a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After washing with 50% hydrochloric acid and equilibrating with 4 mol / L hydrochloric acid, 1 mL of the sample supernatant was added to the exchange column and eluted with 4 mol / L hydrochloric acid. After receiving Sm and Nd, the collected solution was evaporated to dryness and the contents of Sm and Nd were determined using a thermal ionization mass spectrometer.

[0066] 3. 143 Nd / 144 Nd isotope ratio determination

[0067] The Nd isotopes were separated and purified using an ion exchange separation method. The method was as follows: AG50W×8 (H) cation exchange resin was used to separate and purify Nd isotopes. + The sample was added to a quartz ion exchange column (0.6 cm inner diameter, 25 cm resin height), washed with 50% hydrochloric acid and equilibrated with 4 mol / L hydrochloric acid. 1 mL of the supernatant sample was added to the column, eluted with 4 mol / L hydrochloric acid, and the collected solution was then added to an ion exchange column packed with HDEHP resin (0.5 cm inner diameter, 10 cm resin height) and eluted with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enrichment solution. This solution was then analyzed using a multi-detector inductively coupled plasma mass spectrometry (ICP-MS). 143 Nd / 144 Nd ratio.

[0068] Table 3. Sm-Nd isotope analysis results of fluorite samples

[0069]

[0070] The measured 143 Nd / 144 Nd and 147 Sm / 144 By plotting the Nd values ​​on a graph and fitting a straight line equation (i.e., an isochronous line), as shown... Figure 3 As shown, the isochron age of the fluorite sample in this embodiment is 74.4 ± 9.4 Ma (n = 6). 143 Nd / 144 The initial Nd ratio was 0.511952 ± 0.000032, MSWD = 1.2, and the age obtained by this method was consistent with the whole-rock data within the error range.

[0071] Example 4

[0072] This embodiment describes a dating method for the sparingly soluble mineral fluorite. The fluorite sample was collected from a fluorite mine in Jiangsu Province and is relatively young. The method specifically includes the following steps:

[0073] 1. Sample digestion

[0074] Weigh 0.25g of natural fluorite sample (40-60 mesh) into a polytetrafluoroethylene container, add 5mL of 6mol / L hydrochloric acid solution and 8mL of 0.85mol / L boric acid solution, place on a 102℃ hot plate for 27 hours, then open the lid and evaporate the sample to dryness; repeat the hydrochloric acid + boric acid digestion once more to achieve complete digestion of the sample.

[0075] The digested fluorite sample was transferred to a 5 mL centrifuge tube and centrifuged at 5000 rpm for 5 minutes to obtain the sample solution. The sample solution was divided into two portions: one portion was used for Sm and Nd content determination using isotope dilution mass spectrometry; the other portion was used for… 143 Nd / 144 Determination of Nd isotope ratios.

[0076] 2. Determination of Sm and Nd content

[0077] Sm and Nd isotopes were separated and purified using an ion exchange separation method, which involved only one step. The method was as follows: AG50W×8 (H) cation exchange resin was used for the separation and purification of Sm and Nd isotopes. + The sample was added to a quartz ion exchange column (inner diameter 0.6 cm, resin height 25 cm). After washing with 50% hydrochloric acid and equilibrating with 4 mol / L hydrochloric acid, 1 mL of the sample supernatant was added to the exchange column and eluted with 4 mol / L hydrochloric acid. After receiving Sm and Nd, the collected solution was evaporated to dryness and the contents of Sm and Nd were determined using a thermal ionization mass spectrometer.

[0078] 3. 143 Nd / 144 Nd isotope ratio determination

[0079] The Nd isotopes were separated and purified using an ion exchange separation method. The method was as follows: AG50W×8 (H) cation exchange resin was used to separate and purify Nd isotopes. + The sample was added to a quartz ion exchange column (0.6 cm inner diameter, 25 cm resin height), washed with 50% hydrochloric acid and equilibrated with 4 mol / L hydrochloric acid. 1 mL of the supernatant sample was added to the column, eluted with 4 mol / L hydrochloric acid, and the collected solution was then added to an ion exchange column packed with HDEHP resin (0.5 cm inner diameter, 10 cm resin height) and eluted with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enrichment solution. This solution was then analyzed using a multi-detector inductively coupled plasma mass spectrometry (ICP-MS). 143 Nd / 144 Nd ratio.

[0080] Table 4. Sm-Nd isotope analysis results of fluorite samples

[0081]

[0082] The measured 143 Nd / 144 Nd and 147 Sm / 144 By plotting the Nd values ​​on a graph and fitting a straight line equation (i.e., an isochronous line), as shown... Figure 4 As shown, the isochron age of the fluorite sample in this embodiment is 29.3±4.4|15.7 Ma (n=5). 143 Nd / 144 The initial Nd ratio was 0.512239±0.0000017|0.000061, MSWD=4.8, and the age obtained by this method was consistent with the whole-rock data within the error range.

[0083] Comparative Example

[0084] Digestion of natural fluorite samples using only boric acid revealed that the samples swelled into a gel-like state during digestion, with the fluorite particles at the bottom becoming separated from the boric acid, thus affecting the digestion effect. This result demonstrates that adding an appropriate amount of hydrochloric acid can dissolve some non-boron tetrafluoride components (the unstable and volatile product of the reaction between boric acid and calcium fluoride at high temperatures) while simultaneously digesting the fluorite sample with boric acid, thereby allowing for more thorough contact between the fluorite minerals and boric acid and achieving a better reaction effect.

[0085] Three issues need attention during the fluorite digestion process in this invention: 1. Boric acid powder is not easily soluble in water at room temperature, requiring repeated heating and shaking; heating and shaking are also necessary each time boric acid solution is used; 2. Fluorite particles do not undergo significant changes under hydrochloric acid + boric acid leaching, and the actual digestion of the sample occurs after opening the container. Therefore, to ensure complete reaction, the hot plate temperature should be appropriately lowered to ensure sufficient digestion time after opening the container; 3. After evaporation, the sample is a white powder. After dissolving in hydrochloric acid, observe if a small amount of fluorite particles remain at the bottom of the container that have not been completely digested. In this case, the leaching and digestion process needs to be repeated once to ensure complete sample digestion. The ion exchange separation method and instrumental measurement procedure are no different from those for conventional samples.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A dating method for the sparingly soluble mineral fluorite, characterized in that, Includes the following steps: S1, Sample digestion Weigh a natural fluorite sample and place it in a sealed container. Add hydrochloric acid solution and boric acid solution, and heat at 100~110℃ for 20~30 hours. Then open the lid and evaporate the sample to dryness. Repeat the digestion with hydrochloric acid solution and boric acid solution once to achieve complete digestion. After centrifugation, obtain the sample solution. The concentration of the hydrochloric acid solution is 5.9~6.1 mol / L; The concentration of the boric acid solution is 0.8~0.85 mol / L; The ratio of the natural fluorite sample to hydrochloric acid solution and boric acid solution was 0.05~0.25g: 3~5mL: 3~8mL; Determination of S2, Sm and Nd content The Sm and Nd isotopes in the sample solution obtained from S1 were separated and purified by ion exchange method, and the contents of Sm and Nd were determined by thermal ionization mass spectrometry. S3 143 Nd / 144 Nd isotope ratio determination The Nd isotopes in the sample solution obtained from S1 were separated and purified by ion exchange, and then analyzed by multi-receiver inductively coupled plasma mass spectrometry. 143 Nd / 144 Nd ratio; S4. Dating Based on the Sm and Nd contents measured in S2 and the contents measured in S3 143 Nd / 144 The Nd ratio determines the isochron age of 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 centrifugation conditions described in S1 are: centrifugation at 3000~5000 r / min for 5~8 minutes.

4. The method according to claim 1, characterized in that, The method for separating and purifying Sm and Nd isotopes using the ion exchange method described in S2 is as follows: The sample solution to be tested is added to a container filled with cation exchange resin AG50W×8 (H... + In an ion exchange column, the solution was eluted with a 4 mol / L hydrochloric acid solution, and the collected Sm and Nd solutions were collected, evaporated to dryness, and then analyzed.

5. The method according to claim 1, characterized in that, The method for separating and purifying Nd isotopes using the ion exchange method described in S3 is as follows: The sample solution to be tested is added to a container filled with cation exchange resin AG50W×8 (H... + The solution was eluted with 4 mol / L hydrochloric acid in an ion exchange column, and the collected solution was then added to an ion exchange column packed with HDEHP resin and eluted with 0.2 mol / L hydrochloric acid to obtain an Nd isotope enrichment solution for analysis.

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