Fluid inclusion standard samples for in-situ isotopic analysis and their preparation and use

Abstract

The application discloses a fluid inclusion standard sample for in-situ isotopic analysis and a preparation and application thereof. The preparation method comprises the following steps: obtaining silicate glass powder with uniform components, carrying out high-temperature and high-pressure reaction on the glass powder and an equal mass of a fluid salt solution in a closed Cu-Au tube, taking out a reaction product after the reaction and drying the reaction product, and obtaining the fluid inclusion standard sample for isotopic analysis. The application can rapidly capture fluid inclusions in the silicate glass with uniform components, and accurately measure and control Cu isotopes in the fluid inclusions by the degree of Cu isotope fractionation between the acid salt melt and the fluid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of in-situ microanalysis, and particularly relates to a standard sample for in-situ analysis of Cu isotopes in fluid inclusions. BACKGROUND

[0002] With the advancement of isotopic analysis technology, Cu isotope analysis has become an important means of studying geological and geochemical processes. However, the traditional Cu isotope analysis method has the following two limitations: long sample processing period and complex steps: the traditional method usually adopts a sample dissolution method, which requires complete dissolution of the entire sample to be analyzed before testing. This method not only takes time, but also is complex to operate, affecting the analysis efficiency; the selectivity of the analysis object is limited: the traditional method often takes sulfides as the analysis object. However, sulfides in hydrothermal deposits are easily reformed by later metasomatism and alteration, and their isotopic composition is not completely consistent with that of the ore-forming fluid. Under different physical and chemical conditions, sulfides will undergo different degrees of fractionation, resulting in that the Cu isotope composition of the sulfides cannot accurately reflect the Cu isotope evolution of the original ore-forming fluid.

[0003] In recent years, the rapid development of in-situ microanalysis technology provides new possibilities for solving the limitations of traditional methods. In-situ microanalysis technology can directly analyze samples at the micron or even nanometer scale, avoiding the destructive treatment of samples in traditional sample dissolution methods, thereby significantly shortening the sample processing period and simplifying the operation steps. In addition, in-situ microanalysis technology can perform high-precision analysis on specific microareas, avoiding errors caused by sample homogeneity problems in traditional methods.

[0004] However, although in-situ microanalysis technology has made significant progress in geochemical research, its application in Cu isotope analysis still faces challenges, including: when the composition of the ore-forming fluid such as element content and isotope ratio needs to be directly obtained, in-situ microanalysis technology of a single fluid inclusion (such as LA-ICP-MS) is required. However, there is currently a lack of technical means for Cu isotope analysis of a single fluid inclusion, and there is a lack of a single fluid inclusion standard sample with a determined Cu isotope value, which seriously limits the reliability and accuracy of the analysis results. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a single fluid inclusion standard sample for in-situ isotope analysis, particularly Cu isotope analysis, and a preparation and application method thereof. The preparation method can rapidly capture fluid inclusions in a compositionally uniform silicate glass, and accurately measure and control the Cu isotopes in the fluid inclusions by the degree of Cu isotope fractionation between the silicate melt and the fluid.

[0006] The technical scheme of the present application is as follows:

[0007] A method for preparing a fluid inclusion standard sample for in-situ isotopic analysis, comprising:

[0008] (1) mixing and melting raw material components of a silicate glass to obtain a molten mixture;

[0009] (2) quenching and grinding the molten mixture to obtain a silicate glass powder;

[0010] (3) repeating steps (1)-(2) until the components in the silicate glass powder are uniformly distributed to obtain a uniform glass powder;

[0011] (4) sequentially loading the uniform glass powder and an equal amount of a fluid salt solution into a Cu-Au tube with one end closed and the other end closed to obtain a metal capsule;

[0012] (5) performing a closed reaction on the metal capsule at high temperature and high pressure, quenching and removing the metal capsule after the reaction to obtain a reacted metal capsule; the closed reaction is performed at a temperature of 800-850℃, a pressure of 150-220MPa, and a reaction time of 5-14 days;

[0013] (6) removing the reaction product from the reacted metal capsule and drying to obtain the fluid inclusion standard sample for isotopic analysis;

[0014] wherein, in terms of mass percentage, the raw material components of the silicate glass include 4-6wt% of Na2O, 2-3wt% of K2O, 1-2wt% of CaO, 1-2wt% of MgO, 1-2wt% of FeO, 15-17wt% of Al2O3, and 72-73wt% of SiO2; and the components of the fluid salt solution include NaCl, KCl, HCl, RbCl, CsCl, and water, wherein the content of RbCl and CsCl is 100-1000ppm.

[0015] Compared with a traditional preparation method of a fluid inclusion sample, such as a quartz captured fluid inclusion, the above preparation method of the present application has the following obvious advantages: the silicate captured fluid inclusion is more stable, and during LA-ICP-MS single fluid inclusion analysis, the fluid inclusion in the silicate glass is not easy to break during the laser ablation process, and the overall signal is relatively stable, while the traditional quartz captured fluid inclusion is very easy to break during laser ablation, resulting in analysis failure; the silicate glass prepared by the present application also contains a certain amount of Cu, and the Cu content is very uniform, so when performing in-situ analysis of Cu isotope in a silicate mineral micro area, the glass part (avoiding the fluid inclusion) can be used as a standard sample; and the traditional quartz used to capture fluid inclusions has very low Cu content, so the host mineral quartz cannot be used as a standard mineral.

[0016] The preparation method of the present application carries out a fluid-silicate melt reaction under high temperature-high pressure conditions, and through quenching, a large amount of fluid inclusions are captured in the glass, and the composition and isotope composition of the reacted glass and fluid inclusions are very uniform, which can be used as a solid standard sample for analyzing mineral micro area isotopes, and also can be used as an inclusion standard sample for analyzing single fluid inclusion isotopes.

[0017] In addition, the inventors have unexpectedly found that the composition of the silicate glass has a relatively obvious influence on whether fluid inclusions can be synthesized. For example, when a peralkaline (aluminum saturation index ASI = 0.83) silicate glass component such as 6-7wt% Na2O, 2-3wt% K2O, 1-2wt% CaO, 1-2wt% MgO, 1-2wt% FeO, 13-14wt% Al2O3 and 72-73wt% SiO2 is selected for synthesis, there are few or no fluid inclusions distributed in the quenched glass. Only the quasi-alumina (ASI = 1.03) or peralumina (ASI = 1.23) silicate glass component is more conducive to synthesizing stable standard samples containing fluid inclusions. ASI is the aluminum saturation index of the silicate glass, and the calculation method is ASI = nAl2O3 / (nNa2O + nK2O + nCaO), wherein nAl2O3, nNa2O, nK2O and nCaO are the mole content percentages of Al2O3, Na2O, K2O and CaO in the silicate glass, respectively.

[0018] According to some preferred embodiments of the present application, the obtaining of the molten mixture comprises: mixing raw material components of the silicate glass with water to obtain a mixed slurry, and heating and drying the mixed slurry to obtain a dry component mixture; and heating and melting the dry component mixture to obtain the molten mixture.

[0019] According to some preferred embodiments of the present application, the heating rate of the melting is 4-6℃ / min, and the melting temperature is 1500-1700℃.

[0020] According to some preferred embodiments of the present application, the molar ratio of NaCl, KCl and HCl in the fluid salt solution is 1:1:0.05-0.55.

[0021] According to some preferred embodiments of the present application, the raw material components of the silicate glass include 5.45wt% of Na2O, 2.47wt% of K2O, 1.71wt% of CaO, 1.06wt% of MgO, 1.662wt% of FeO, 15.08wt% of Al2O3 and 72.57wt% of SiO2.

[0022] According to some preferred embodiments of the present application, the raw material components of the silicate glass include 4.61wt% of Na2O, 2.42wt% of K2O, 1.70wt% of CaO, 1.08wt% of MgO, 1.71wt% of FeO, 16.40wt% of Al2O3 and 72.10wt% of SiO2.

[0023] According to some preferred embodiments of the present application, the mass of Na2O and K2O added in step (1) is 1.1-1.2 times of the mass of Na2O and K2O in the raw material components of the silicate glass.

[0024] According to some preferred embodiments of the present application, the mass percentage of Cu and Au in the Cu-Au tube is 3% and 97% respectively.

[0025] According to some preferred embodiments of the present application, the preparation method comprises:

[0026] (1) adding deionized water to the raw material components of the silicate glass and mixing uniformly to obtain a mixture slurry, heating and drying the mixture slurry to obtain a dry component mixture, and heating the dry component mixture to 1600℃ at a heating rate of 5℃ / min to obtain a completely melted component mixture;

[0027] (2) quenching the completely melted component mixture in water to obtain a glass-like product, grinding the glass-like product to obtain the silicate glass powder;

[0028] (3) repeating the melting and quenching process of steps (1)-(2) until the glass composition is completely uniform, to obtain a uniform glass powder;

[0029] (4) welding the one end of the Cu-Au tube with uniform chemical composition, loading the uniform glass powder and the same mass of the fluid salt solution into the other end of the Cu-Au tube in sequence, then pressing the other end and welding it to form a closed metal capsule, wherein the Cu-Au tube has an outer diameter of 3.0 mm, an inner diameter of 2.8 mm and a length of 20 mm, and the mass percentage of Cu and Au is 3% and 97% respectively;

[0030] (5) reacting the closed metal capsule at 850±1℃ and 200±2MPa for 7 days with water as the pressure medium, then quenching, taking out and drying the reacted metal capsule;

[0031] (6) soaking the dried reacted metal capsule in a dilute hydrochloric acid solution, then rinsing, drying, liquid nitrogen cooling, taking out the obtained silicate glass fluid inclusion and heating in deionized water at 80℃ for 3h to obtain the fluid inclusion standard sample for isotope analysis.

[0032] The application further provides the fluid inclusion standard sample for in-situ isotope analysis prepared according to the preparation method.

[0033] The standard sample has a spherical shape and is a light brown transparent glass, and under a microscope, it can be found that the silicate glass uniformly distributes round or ellipsoidal fluid inclusions, the size of the fluid inclusions is about 50 microns, the fluid inclusions contain both gas and liquid phases, and the volume ratio of the gas and liquid phases of all the fluid inclusions is very close.

[0034] The standard sample is transparent, so after being prepared into a resin target, it is very easy to locate different fluid inclusions on the LA-ICP-MS instrument, and the size of the fluid inclusions is very suitable for in-situ LA-ICP-MS test analysis (too large or too small fluid inclusions are not conducive to in-situ LA-ICP-MS analysis, too large size leads to that the laser beam spot cannot cover the inclusion, and too small size leads to too low analysis signal intensity).

[0035] The application further provides the application of the fluid inclusion standard sample for in-situ isotope analysis as a Cu isotope in-situ analysis standard sample.

[0036] According to some preferred embodiments of the application, the application comprises obtaining the Cu isotope analysis result in the fluid inclusion by the Cl element concentration in the fluid inclusion and the Cu isotope value of the silicate glass in the fluid inclusion.

[0037] More preferably, the Cu isotope analysis result in the fluid inclusion is obtained by the following calculation model:

[0038] δ65 Cu fluid = (-0.13 x C f-p + 0.17) + δ 65 Cu glass

[0039] wherein δ 65 Cu glass = [( 65 Cu / 63 Cu) sample / ( 65 Cu / 63 Cu) NIST 976 - 1] x 1000 ‰;

[0040] wherein δ 65 Cu fluid is the Cu isotope value in fluid inclusion in the standard sample, δ 65 Cu glass is the Cu isotope value in silicate glass in the standard sample, C f-p is the Cl content in fluid inclusion in the standard sample, ( 65 Cu / 63 Cu) sample represents the ratio of Cu and 65 Cu in silicate glass in the standard sample, ( 63 Cu / 65 Cu) 63 NIST 976 represents the Cu isotope value of international Cu isotope standard sample NIST 976. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a microscopic image of a silicate glass fluid inclusion observation sample obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the present application will be further described below in combination with the embodiments of the present application. The embodiments described below are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present application.

[0043] Example 1

[0044] A single fluid inclusion standard sample for Cu isotope analysis is prepared by the following steps:

[0045] ​(1) According to Table 1, a total mass of 10 g of analytically pure silicate components was weighed. To compensate for the volatilization loss of Na2O and K2O during high-temperature firing, the weighed masses of Na2O and K2O were approximately 1.1 times the corresponding masses in Table 1.

[0046] (2) adding the weighed silicate component into an agate mortar, adding deionized water and stirring for about 1 hour to obtain a uniformly mixed mixture slurry, heating the mixture to 110° C. and drying it to obtain a dry component mixture;

[0047] (3) adding the dried component mixture into a platinum crucible, heating it to 1600°C in a high-temperature muffle furnace at a heating rate of 5°C / min and maintaining it for 12 hours to obtain a completely melted component mixture, then quickly taking out the platinum crucible and placing it into deionized water for rapid quenching to obtain a light brown, transparent glassy product, which was crushed and ground into powder in an agate mortar to obtain glass powder;

[0048] (4) Repeat the melting and quenching process of step (3) above until the glass composition is completely uniform to obtain a uniform glass powder;

[0049] (5) One end of a Cu-Au tube with uniform chemical composition was welded closed, and about 20 mg of uniform glass powder (particle size <200 mesh) and equal amounts of fluid solutions of different salinities shown in Table 2 were sequentially loaded from the other end (the fluid solution was prepared by first preparing a pure aqueous solution containing NaCl, KCl, and HCl, then passing N2 gas for 1 hour to eliminate O2 in the solution, and then adding 200 ppm of RbCl and CsCl). The other end was then pressed tightly and sealed by carbon arc welding to form a closed metal capsule. The closed metal capsule was left to stand at a pressure of 200 MPa for 2 hours, then taken out and weighed to check for leakage, and the capsule with no mass loss was selected to proceed to step (6); wherein the outer diameter of the Cu-Au tube was 3.0 mm, the inner diameter was 2.8 mm, and the length was 20 mm, and the mass percentages of Cu and Au were 3% and 97%, respectively;

[0050] (6) placing the sealed metal capsule in a cold-sealed autoclave, using water as the pressure medium, and reacting at 850±1°C and 200±2 MPa for 7 days, then quickly quenching the autoclave, taking out the reacted metal capsule, heating it in an oven at 110°C for 2 hours, and then weighing it to check for leakage. Selecting the reacted metal capsule with no mass loss to proceed to step (7);

[0051] (7) The post-reaction metal capsule obtained in step (6) is soaked in a dilute hydrochloric acid solution for half an hour, washed with deionized water, dried, cooled by liquid nitrogen, and then opened and placed in a Teflon beaker containing deionized water. 10-20 ml of deionized water is added, and heated at 80°C for 3 hours to obtain a silicate glass fluid inclusion;

[0052] (8) The silicate glass fluid inclusion is taken out and repeatedly washed and dried, and all the washing solutions are collected during the process to obtain a dried silicate glass fluid inclusion, which is the single fluid inclusion standard sample for isotope analysis.

[0053] The obtained dried silicate glass fluid inclusion is fixed in epoxy resin and finely polished by diamond paste to obtain an observation sample, which is observed by a microscope, as shown in FIG. 2, wherein the silicate glass is uniformly distributed with fluid inclusions with a diameter of about 30-50 μm, which is suitable for LA-ICP-MS in-situ analysis test. Figure 1

[0054] Table 1 Silicate glass composition

[0055] Ingredients Content (wt%) Na2O 5.45 K2O 2.47 CaO 1.71 MgO 1.06 FeO 1.66 Al2O3 15.08 SiO2 72.57 Total 100.00 ASI (Aluminum Saturation Index) 1.02

[0056] Table 2 Fluid composition

[0057]

[0058] Example 2

[0059] The observation sample obtained in Example 1 is subjected to LA-ICP-MS in-situ detection analysis, and the glassy product therein is subjected to electron probe (EPMA) detection analysis.

[0060] Among them, the analysis points of LA-ICP-MS detection analysis are distributed from the edge of the silicate glass to the center of the glass, covering different regions of the sample, and the major and trace elements analyzed include: Na2O, K2O, CaO, FeO, Al2O3, SiO2, Cu, Rb, Cs;

[0061] ​The elements detected by EPMA include the major elements and Cl element of the glassy product. The content of Na and K in the major elements is first detected in the analysis, using a peak counting time of 10 seconds and a background counting time of 5 seconds to minimize the loss of the two elements in the detection process, and other major elements are analyzed using a peak counting time of 20 seconds and a background counting time of 10 seconds; the detection conditions of the major elements are 15 kV accelerating voltage, 5 nA beam current and 15 μm beam spot diameter; the detection conditions of the Cl element are 15 kV accelerating voltage, 20 nA beam current and 15 μm beam spot diameter, and the counting times are 120 seconds for the peak and 60 seconds for the background, respectively. When detecting the content of the Cl element, a glass standard sample as a known sample is measured periodically to control the long-term relative accuracy to 2%.

[0062] In the detection analysis, the following judgment standard is used to judge whether the element distribution of the single fluid inclusion standard sample for isotope analysis in the observed sample is uniform: the variation range of the element content from the edge to the center is less than 5%.

[0063] The detection results show that the composition distribution of the major elements and trace elements of the silicate glass fluid inclusion synthesized in Example 1 is very uniform from the core to the edge, and the elements such as Rb, Cs and Cl that are difficult to diffuse in the fluid inclusion also have a very uniform distribution, for example, the content variation ranges of Rb and Cs in the sample with a fluid salinity of 20 wt.% in Example 1 (Table 2, the third sample) from the core to the edge are 72.3-73.5 ppm and 57.5-58.1 ppm, respectively, proving that the temperature and pressure conditions and reaction time selected in Example 1 can ensure that the fluid-melt reaction reaches complete equilibrium, and the obtained silicate glass fluid inclusion can be used as a standard sample.

[0064] Example 3

[0065] The Cu isotope composition of the silicate glass is tested by the following process:

[0066] The Cu isotope composition of the silicate glass has been uniform, so part of the silicate glass in the silicate glass fluid inclusion can be directly selected for testing; the obtained silicate glass powder is dissolved in a closed Savillex beaker containing double-distilled concentrated hydrofluoric acid and nitric acid, hydrochloric acid and nitric acid are added in turn, and then hydrochloric acid is added to ensure that the sample is completely dissolved;

[0067] The Cu element in the dissolved sample is chemically separated and purified from the matrix elements by cation exchange chromatography;

[0068] The purified samples were dissolved in 2 wt.% nitric acid and introduced into a Thermo-Fisher Neptune Plus MC-ICP-MS instrument via an ESIPFA microflow nebulizer at a suction rate of 50 μl / min, using low mass resolution mode for Cu isotope ratio analysis;

[0069] The δ 65 Cu values were the average of three analyses, where δ 65 Cu = [(

[0070] δ 65 Cu = [( 65 Cu / 63 Cu) sample / ( 65 Cu / 63 Cu) NIST 976 -1] x 1000‰, (1)

[0071] where δ 65 Cu represents the Cu isotope value of the sample being analysed, ( 65 Cu / 63 Cu) sample represents the ratio of 65 Cu and 63 Cu in the sample being analysed, ( 65 Cu / 63 Cu) NIST 976 and

[0072] The δ 65 Cu value of the sample obtained under the condition of a fluid salinity of 20 wt.% (Table 2, 3rd experiment) in Example 1 was calculated to be +0.776‰.

[0073] During the analysis, two single element reference materials, ERM-AE-647 and AAS, were used to monitor instrument drift and seven international rock standards, namely AGV-2, BHVO-2, BCR-2, BIR-la, GSP-2, W-2a and PCC-1, were processed with the samples to check the accuracy of the δ 65 Cu values.

[0074] The results of the analysis show that the long-term external reproducibility of the δ 65 Cu measurements in this example is better than ±0.05‰.

[0075] Example 4

[0076] The Cu isotope composition in the silicate glass fluid inclusion is calculated by the following process:

[0077] Method (1): The Cu isotope composition of the quenched fluid product is analyzed, which can represent the Cu isotope composition in the silicate glass captured fluid inclusion; the Cu isotope of the fluid after the experiment with the fluid salinity of 20wt.% (Table 2, the third experiment) is analyzed in this embodiment, and the analysis result shows that the δ 65 Cu value of the fluid after the reaction is +0.416‰;

[0078] Method (2): The Cu isotope composition of the glass after the experiment is calculated according to the change of the composition of the silicate glass and the fluid before and after the reaction;

[0079] The calculation formula is as follows:

[0080] δ 65 Cu fluid = (-0.13 × C f-p + 0.17) + δ 65 Cu glass (2)

[0081] Wherein, δ 65 Cu fluid is the Cu isotope value in the fluid inclusion, 65 Cu glass is the Cu isotope value in the silicate glass, and C f-p is the Cl content in the fluid after the reaction.

[0082] The sample with the fluid salinity of 20wt.% in Table 2, the third sample, is calculated in this embodiment, and the δ 65 Cu value of the fluid inclusion is 0.426‰, which is consistent with the Cu isotope value of the fluid directly measured by method 1, and the error between them is less than 20%, which indicates that the Cu isotope value in the silicate glass fluid inclusion prepared in embodiment 1 is stable, and can be used as a standard sample for in-situ analysis of Cu isotope.

[0083] Comparative Example 1

[0084] The fluid inclusion standard sample is prepared according to the process of embodiment 1, and only the component ratio of the silicate glass is adjusted as shown in Table 3, wherein the ratio 1 represents the peralkaline glass, and the ratio 2 represents the peraluminous glass:

[0085] Table 3 Component ratio of silicate glass in comparative example 1

[0086]

[0087]

[0088] The results show that the peralkaline glass cannot effectively synthesize the sample rich in fluid inclusions, and the glass in the obtained product is transparent and has few fluid inclusions; the peraluminous glass can also obtain the standard sample rich in fluid inclusions, and the number of fluid inclusions increases with the increase of the aluminum saturation degree.

[0089] It should be noted that the above only describes the preferred embodiments of the present application, which should not limit the protection scope of the technical solutions of the present application. Any modification made by those skilled in the art to the technical solutions described in the foregoing embodiments, equivalent replacement of technical features, etc. should be included in the protection scope of the present application.

Claims

1. A method for preparing a fluid inclusion standard sample for in situ isotope analysis, characterized in that: It includes: (1) Mixing and melting raw material components of silicate glass to obtain a molten mixture; (2) quenching and grinding the molten mixture to obtain silicate glass powder; (3) Repeating steps (1)-(2) until the components in the silicate glass powder are evenly distributed to obtain a uniform glass powder; (4) The uniform glass powder and an equal mass of fluid salt solution are successively loaded into a Cu-Au tube with one end closed and the other end closed to obtain a metal capsule; (5) subjecting the metal capsule to a sealing reaction at high temperature and high pressure, quenching and removing the metal capsule after the reaction, and obtaining a metal capsule after the reaction; the sealing reaction temperature is 800-850°C, the pressure is 150-220 MPa, and the reaction time is 5-14 days; (6) removing the reaction product from the metal capsule after the reaction and drying it to obtain the fluid inclusion standard sample for isotope analysis; The raw material components of the silicate glass include, by mass percentage, 5.45 wt% Na2O, 2.47 wt% K2O, 1.71 wt% CaO, 1.06 wt% MgO, 1.662 wt% FeO, 15.08 wt% Al2O3 and 72.57% SiO2, or 4.61 wt% Na2O, 2.42 wt% K2O, 1.70 wt% CaO, 1.08 wt% MgO, 1.71 wt% FeO, 16.40 wt% Al2O3 and 72.10% SiO2; the components of the fluid salt solution include NaCl, KCl, HCl, RbCl, CsCl and water, wherein the contents of RbCl and CsCl are 100-1000 ppm.

2. The preparation method according to claim 1, characterized in that The molten mixture is obtained by mixing the raw material components of the silicate glass with water to obtain a mixed slurry, heating and drying the mixed slurry to obtain a dry component mixture; and heating and melting the dry component mixture to obtain the molten mixture.

3. The preparation method according to claim 2, characterized in that The heating rate of the heating and melting is 4-6°C / min, and the melting temperature is 1500-1700°C.

4. The preparation method according to claim 1, characterized in that In the fluid salt solution, the molar ratio of NaCl, KCl and HCl is 1:1:0.05-0.

55.

5. The preparation method according to claim 1, characterized in that The mass fractions of Na2O and K2O added in step (1) are both 1.1 to 1.2 times of their mass in the raw material components of the silicate glass.

6. The preparation method according to claim 1, characterized in that The mass percentages of Cu and Au in the Cu-Au tube are 3% and 97% respectively.

7. The preparation method according to claim 1, characterized in that It includes: (1) adding deionized water to the raw material components of the silicate glass and mixing them uniformly to obtain a mixture slurry, heating and drying the mixture slurry to obtain a dry component mixture, and heating the dry component mixture to 1600° C. at a heating rate of 5° C. / min to obtain a completely melted component mixture; (2) placing the completely melted component mixture into water for quenching to obtain a glassy product, and grinding the product to obtain the silicate glass powder; (3) Repeat the melting and quenching process of steps (1)-(2) above until the glass composition is completely uniform and a uniform glass powder is obtained; (4) Welding one end of a Cu-Au tube with uniform chemical composition to seal it, and sequentially loading the uniform glass powder and an equal mass of a fluid salt solution into the other end, and then pressing the other end tightly and welding it to seal it to form a closed metal capsule, wherein the Cu-Au tube has an outer diameter of 3.0 mm, an inner diameter of 2.8 mm, and a length of 20 mm, and the mass percentages of Cu and Au are 3% and 97%, respectively; (5) Using water as the pressure medium, the sealed metal capsule was subjected to high temperature and high pressure reaction at 850±1℃ and 200±2 MPa for 7 days, followed by quenching. The metal capsule after reaction was taken out and dried; (6) The dried metal capsule after the reaction is immersed in a dilute hydrochloric acid solution, then rinsed, dried, and cooled with liquid nitrogen. The silicate glass fluid inclusions obtained therein are taken out and heated in deionized water at 80°C for 3 hours to obtain the fluid inclusion standard sample for isotope analysis.

8. A fluid inclusion standard sample for in situ isotope analysis prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the fluid inclusion standard sample for in-situ isotope analysis according to claim 8 as a standard sample for in-situ analysis of Cu isotopes.

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