Fluid inclusion standard sample for in-situ isotope analysis and preparation and application thereof

Abstract

The invention discloses a fluid inclusion standard sample for in-situ isotope analysis as well as preparation and application of the fluid inclusion standard sample. 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 a fluid salt solution with the same mass in a closed Cu-Au tube, taking out a reaction product after the reaction, and drying to obtain the fluid inclusion standard sample for isotope analysis. According to the method, the silicate glass with uniform components can rapidly capture the fluid inclusion, and the Cu isotope in the fluid inclusion is accurately measured and controlled according to the fractionation degree of the Cu isotope between the acid salt melt and the fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ micro-area analysis, and particularly to a standard sample for in-situ analysis of Cu isotopes in fluid inclusions. Background Art

[0002] With the progress of isotope analysis technology, Cu isotope analysis has become an important means for studying geological and geochemical processes. However, the traditional Cu isotope analysis methods have the following two limitations: long sample processing cycle and cumbersome steps: The traditional method usually adopts the sample dissolution method, which requires complete dissolution of the entire sample to be analyzed before testing. This method is not only time-consuming but also complex in operation, affecting the analysis efficiency; selectivity limitation of the analysis object: The traditional method often uses sulfides as the analysis object. However, sulfides in hydrothermal deposits are prone to be modified by later metasomatic alteration, and their isotope compositions are not exactly the same as those of the ore-forming fluid. Under different physical and chemical conditions, sulfides will undergo different degrees of fractionation, resulting in the Cu isotope composition of sulfides being unable to accurately reflect the Cu isotope evolution of the original ore-forming fluid.

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

[0004] However, although significant progress has been made in the application of in-situ micro-area analysis technology in geochemical research, its application in Cu isotope analysis still faces challenges, including: when it is necessary to directly obtain the composition of ore-forming fluid such as element content and isotope ratio, the in-situ micro-area analysis technology of a single fluid inclusion (such as LA-ICP-MS) needs to be adopted. However, at present, there is a lack of technical means for analyzing the Cu isotopes of a single fluid inclusion, and there is a lack of standard samples of single fluid inclusions with determined Cu isotope values, which severely limits the reliability and accuracy of the analysis results. Summary of the Invention

[0005] Aiming at the defects of the prior art, the purpose of the present invention is to provide a standard sample of a single fluid inclusion for in-situ isotope analysis, especially for Cu isotope analysis, and its preparation and application methods. The preparation method can quickly capture fluid inclusions in homogeneous silicate glass, and accurately measure and control the Cu isotopes in the fluid inclusions through the fractionation degree of Cu isotopes between the silicate melt and the fluid.

[0006] The technical solution of the present invention is as follows:

[0007] Method for preparing a fluid inclusion standard sample for in-situ isotope analysis, comprising:

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

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

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

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

[0012] (5) Conducting a closed reaction on the metal capsule under high temperature and high pressure, quenching and taking it out after the reaction to obtain a post-reaction metal capsule; the temperature of the closed reaction is 800-850 °C, the pressure is 150-220 MPa, and the reaction time is 5-14 days;

[0013] (6) Taking out the reaction product from the post-reaction metal capsule and drying it to obtain the fluid inclusion standard sample for isotope analysis;

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

[0015] The above preparation method of the present invention has the following remarkable advantages compared with the traditional preparation method of fluid inclusion samples, such as quartz capturing fluid inclusions: The fluid inclusions captured by silicate are more stable. When performing LA-ICP-MS single fluid inclusion analysis, the fluid inclusions in the silicate glass are not prone to rupture during the laser ablation process, and the overall signal is relatively stable. In contrast, the fluid inclusions captured by traditional quartz are very likely to rupture during laser ablation, resulting in analysis failure; The silicate glass prepared by the present invention also contains a certain amount of Cu, and the Cu content distribution is very uniform. Therefore, when performing in-situ Cu isotope analysis of silicate minerals in microzones, the glass part (avoiding fluid inclusions) can be used as a standard sample; While traditional quartz is used to capture fluid inclusions, the Cu content in quartz is very low, so the host mineral quartz cannot be used as a standard mineral.

[0016] The preparation method of the present invention conducts a fluid-silicate melt reaction under high temperature and high pressure conditions, and a large number of fluid inclusions are captured by quenching the glass. The compositions and isotope compositions of the reacted glass and fluid inclusions are very uniform, and it can be used as a solid standard sample for analyzing the isotopes of mineral microzones and also as an inclusion standard sample for analyzing the isotopes of single fluid inclusions.

[0017] Moreover, the inventors unexpectedly found that the composition of the silicate glass has a relatively obvious influence on whether fluid inclusions can be synthesized. For example, when using a peralkaline (aluminum saturation index ASI = 0.83) silicate glass composition such as 6-7 wt% Na2O, 2-3 wt% K2O, 1-2 wt% CaO, 1-2 wt% MgO, 1-2 wt% FeO, 13-14 wt% Al2O3, and 72-73% SiO2 for synthesis, there are few or no fluid inclusions distributed in the quenched glass. Only meta-aluminous (ASI = 1.03) or peraluminous (ASI = 1.23) silicate glass compositions are 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), where nAl2O3, nNa2O, nK2O, and nCaO are the molar content percentages of Al2O3, Na2O, K2O, and CaO in the silicate glass, respectively.

[0018] According to some preferred embodiments of the present invention, the obtaining of the molten mixture includes: 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 dried component mixture; heating and melting the dried component mixture to obtain the molten mixture.

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

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

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

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

[0023] According to some preferred embodiments of the present invention, in step (1), the masses of the added Na2O and K2O are both 1.1 - 1.2 times their masses in the raw material components of the silicate glass.

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

[0025] According to some preferred embodiments of the present invention, the preparation method includes:

[0026] (1) Add deionized water to the raw material components of the silicate glass and mix evenly to obtain a mixture slurry. Heat and dry the mixture slurry to obtain a dry component mixture. Heat the dry component mixture at a heating rate of 5 °C / min to 1600 °C until a completely molten component mixture is obtained;

[0027] (2) Quench the completely molten component mixture in water to obtain a glassy product, and grind it to obtain the silicate glass powder;

[0028] (3) Repeat the melting and quenching processes of the above steps (1) - (2) until the glass composition is completely homogeneous to obtain a homogeneous glass powder;

[0029] (4) One end of a Cu-Au tube with uniform chemical composition is welded and sealed. From the other end, the uniform glass powder and an equal mass of fluid salt solution are sequentially loaded. Then, the other end is compacted and welded and sealed to form a sealed metal capsule. Among them, the outer diameter of the Cu-Au tube is 3.0 mm, the inner diameter is 2.8 mm, and the length is 20 mm. The mass percentage contents of Cu and Au are 3% and 97% respectively;

[0030] (5) Using water as the pressure medium, the sealed metal capsule is subjected to high-temperature and high-pressure reaction at 850 ± 1 °C and 200 ± 2 MPa for 7 days. Then, it is quenched, and the reacted metal capsule is taken out and dried;

[0031] (6) The dried reacted metal capsule is immersed in dilute hydrochloric acid solution, then rinsed clean, dried, cooled by liquid nitrogen, and the obtained silicate glass fluid inclusions are taken out and heated in deionized water at 80 °C for 3 h to obtain the fluid inclusion standard sample for isotope analysis.

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

[0033] The standard sample is spherical in shape, a light brown and transparent glass. When observed under a microscope, it can be found that rounded or ellipsoidal fluid inclusions are evenly distributed in the silicate glass. The size of the fluid inclusions is close to about 50 microns. The fluid inclusions contain both gas and liquid phases, and the volume ratios of the gas and liquid phases of all fluid inclusions are very close.

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

[0035] The present invention further provides the application of the above 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 present invention, the application includes: obtaining the Cu isotope analysis result in the fluid inclusion through the Cl element concentration in the fluid inclusion of the standard sample and the Cu isotope value of the silicate glass therein.

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

[0038] δ65 Cu fluid = (-013 × 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] × 1000‰;

[0040] wherein, δ 65 Cu fluid is the Cu isotope value in fluid inclusions 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 inclusions in the standard sample, ( 65 Cu / 63 Cu sample represents the 65 Cu and 63 Cu ratio of silicate glass in the standard sample, ( 65 Cu / 63 Cu NIST 976 represents the Cu isotope value of the international Cu isotope standard sample NIST 976. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0042] The technical solutions in the present invention will be further described below in conjunction with the embodiments of the present invention. The following described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the protection scope of the present invention.

[0043] Example 1

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

[0045] (1) Weigh out 10 g of analytical pure silicate components in total according to Table 1. Among them, to compensate for the volatilization loss of Na2O and K2O during high-temperature firing, the weighed masses of Na2O and K2O are approximately 1.1 times the corresponding masses in Table 1;

[0046] (2) Add the weighed silicate components into an agate mortar, and add deionized water and stir for about 1 h to obtain a uniformly mixed mixture slurry. Heat it to 110 °C and dry it to obtain a dry component mixture;

[0047] (3) Add the dry component mixture into a platinum crucible, heat it to 1600 °C at a heating rate of 5 °C / min in a high-temperature muffle furnace and hold for 12 h to obtain a completely molten component mixture. Then quickly take out the platinum crucible and put it into deionized water for rapid quenching to obtain a light brown, transparent glassy product. Crush and grind it into powder in an agate mortar to obtain glass powder;

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

[0049] (5) Weld and seal one end of a Cu-Au tube with uniform chemical composition. Sequentially load about 20 mg of the homogeneous glass powder (particle size < 200 mesh) and an equal mass of fluid solutions with different salinities shown in Table 2 from the other end (the fluid solution is prepared by first preparing a pure aqueous solution containing NaCl, KCl, and HCl, then introducing N2 gas for 1 h to remove O2 in the solution, and then adding 200 ppm of RbCl and CsCl). Then press the other end tightly and seal it by carbon arc welding to make a sealed metal capsule. Let the sealed metal capsule stand at a pressure of 200 MPa for 2 h, then take it out and weigh it to check for leakage. Select the capsules without mass loss for step (6); among them, the outer diameter of the Cu-Au tube is 3.0 mm, the inner diameter is 2.8 mm, and the length is 20 mm, and the mass percentages of Cu and Au are 3% and 97% respectively;

[0050] (6) Put the sealed metal capsule into a cold-sealed autoclave, use water as the pressure medium, carry out a high-temperature and high-pressure reaction at 850 ± 1 °C and 200 ± 2 MPa for 7 days. Then quickly quench the autoclave. Take out the reacted metal capsule and heat it in an oven at 110 °C for 2 h. Then weigh it to check for leakage. Select the reacted metal capsules without mass loss for step (7);

[0051] (7) Immerse the reacted metal capsules obtained in step (6) in a dilute hydrochloric acid solution for half an hour, rinse thoroughly with deionized water, dry, cool using liquid nitrogen, then open and place in a Teflon beaker containing deionized water, add 10 - 20 ml of deionized water, and heat at 80 °C for 3 h to obtain silicate glass fluid inclusions;

[0052] (8) Take out the silicate glass fluid inclusions, rinse repeatedly and then dry. During this process, collect all the rinsing solutions to obtain the dried silicate glass fluid inclusions, which are the single fluid inclusion standard samples for isotope analysis.

[0053] Fix the obtained dried silicate glass fluid inclusions in epoxy resin and perform fine polishing with diamond paste to obtain an observation sample, and observe it through a microscope. As shown in the appendix Figure 1 , where fluid inclusions with a diameter of about 30 - 50 μm are evenly distributed in the silicate glass, suitable for in-situ analysis and testing by LA-ICP-MS.

[0054] Table 1 Composition of Silicate Glass

[0055] Component Content (wt%) <![CDATA[Na2O]]> 5.45 <![CDATA[K2O]]> 2.47 CaO 1.71 MgO 1.06 FeO 1.66 <![CDATA[Al2O3]]> 15.08 <![CDATA[SiO2]]> 72.57 Total 100.00 ASI (aluminum saturation index) 1.02

[0056] Table 2 Fluid Composition

[0057]

[0058] Example 2

[0059] Perform in-situ detection and analysis by LA-ICP-MS on the observation sample obtained in Example 1 and perform electron probe (EPMA) detection and analysis on the glassy products therein.

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

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

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

[0063] The detection results show that the compositional distributions of major and trace elements in the silicate glass fluid inclusions synthesized in Example 1 are very uniform from the core to the edge. In particular, elements that are difficult to diffuse in the fluid inclusions, such as Rb, Cs, and Cl, etc., also show very uniform distributions. For example, in the sample with a fluid salinity of 20 wt.% (the 3rd sample in Table 2) in Example 1, from the core to the edge, the variation ranges of the contents of Rb and Cs are 72.3 - 73.5 ppm and 57.5 - 58.1 ppm respectively, proving that the temperature, pressure conditions, reaction duration, etc. selected in Example 1 can ensure that the fluid-melt reaction reaches complete equilibrium, and the obtained silicate glass fluid inclusions can be used as standard samples.

[0064] Example 3

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

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

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

[0068] The purified sample was dissolved in 2 wt.% nitric acid and introduced into a Thermo-Fisher Neptune Plus MC-ICP-MS instrument at an aspiration rate of 50 μl / min through an ESIPFA micro-flow nebulizer. The Cu isotope ratio analysis was carried out in the low mass resolution mode;

[0069] The δ 65 Cu value of each analyzed sample was the average of three analyses. Among them, the calculation method of δ 65 Cu is as follows:

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

[0071] Among them, δ 65 Cu represents the Cu isotope value of the analyzed sample, and ([[]] 65 Cu / 63 Cu) sample represents the ratio of 65 Cu and 63 Cu in the analyzed sample, and ([[]] 65 Cu / 63 Cu) NIST 976 represents the Cu isotope value of the international Cu isotope standard sample NIST 976.

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

[0073] In the analysis, two single-element reference materials ERM-AE-647 and AAS were used to monitor instrument drift, and seven international rock standards (i.e., AGV-2, BHVO-2, BCR-2, BIR-1a, GSP-2, W-2a and PCC-1) were processed together with the samples to detect the accuracy of the δ 65 Cu value.

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

[0075] Example 4

[0076] The Cu isotope composition in fluid inclusions of silicate glass is calculated through the following process:

[0077] Method (1): Analyze the Cu isotope composition of the quenched fluid product, which can represent the Cu isotope composition in the fluid inclusions captured by the silicate glass; in this example, Cu isotope analysis was performed on the fluid after the experiment with a fluid salinity of 20 wt.% (the 3rd experiment in Table 2), and the analysis result shows that the δ 65 Cu value of the reacted fluid is +0.416‰;

[0078] Method (2): Calculate based on the changes in the compositions of the silicate glass and the fluid before and after the reaction, from the Cu isotope composition of the glass after the experiment;

[0079] The calculation formula is as follows:

[0080] δ 65 Cu fluid = (-013×C f-p +0.17) + δ 65 Cu glass (2)

[0081] Among them, δ 65 Cu fluid is the Cu isotope value in the fluid inclusions, 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] In this example, calculations were performed on the 3rd sample in Table 2 with a fluid salinity of 20 wt.%, and according to formula (2), the δ 65 Cu value of the fluid inclusions was calculated to be 0.426‰, which is relatively consistent with the directly measured fluid Cu isotope value by Method 1, and the mutual error is less than 20%, indicating that the Cu isotope value in the fluid inclusions of the silicate glass prepared in Example 1 is stable and can be used as a standard sample for in-situ Cu isotope analysis.

[0083] Comparative Example 1

[0084] Prepare a fluid inclusion standard sample according to the process of Example 1, only adjust the component ratios of the silicate glass as shown in Table 3, where Ratio 1 represents peralkaline glass and Ratio 2 represents peraluminous glass:

[0085] Table 3 Component Ratios of Silicate Glass in Comparative Example 1

[0086]

[0087]

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

[0089] It should be noted that the above are only the preferred embodiments of the present invention, and they should not limit the protection scope of the technical solution of the present invention. Any modifications made by those of ordinary skill in the art to the technical solutions recorded in the foregoing embodiments, and any equivalent replacements of technical features, etc., should be included in the protection scope of the present invention.

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) to (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 a fluid salt solution are successively loaded into a Cu-Au tube with one end sealed, and the other end sealed to obtain a metal capsule; (5) subjecting the metal capsule to a closed reaction at high temperature and high pressure, and quenching and removing the metal capsule after the reaction to obtain a metal capsule after the reaction; the closed reaction temperature is 800-850° C., the pressure is 150-220 MPa, and the reaction time is 5-14 days; (6) taking out the reaction product from the metal capsule after the reaction and drying it to obtain the fluid inclusion standard sample for isotope analysis; Wherein, the raw material components of the silicate include, by mass percentage, 4-6wt% Na2O, 2-3wt% K2O, 1-2wt% CaO, 1-2wt% MgO, 1-2wt% FeO, 15-17wt% Al2O3 and 72-73% SiO2; 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.

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 4, characterized in that: In terms of mass percentage, the raw material components of the silicate include 5.45wt% Na2O, 2.47wt% K2O, 1.71wt% CaO, 1.06wt% MgO, 1.662wt% FeO, 15.08wt% Al2O3 and 72.57% SiO2 or 4.61wt% Na2O, 2.42wt% K2O, 1.70wt% CaO, 1.08wt% MgO, 1.71wt% FeO, 16.40wt% Al2O3 and 72.10% SiO2.

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

7. 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.

8. 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 molten component mixture; (2) placing the completely molten component mixture into water for quenching to obtain a glassy product, and grinding the product to obtain the silicate glass powder; (3) Repeating the melting and quenching process of steps (1) to (2) above until the glass composition is completely uniform to obtain a uniform glass powder; (4) welding and sealing one end of a Cu-Au tube with uniform chemical composition, and sequentially loading the uniform glass powder and an equal mass of a fluid salt solution from the other end, and then pressing the other end tightly and welding and sealing 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 is subjected to high temperature and high pressure reaction at 850±1°C and 200±2MPa for 7 days, followed by quenching, and the reacted metal capsule is taken out and dried; (6) Soaking the dried metal capsule after the reaction in a dilute hydrochloric acid solution, then rinsing it, drying it, and cooling it with liquid nitrogen. Taking out the silicate glass fluid inclusions obtained therein, heating them in deionized water at 80° C. for 3 h, and obtaining the fluid inclusion standard sample for isotope analysis.

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

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

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