Preparation method of blocky olivine iron isotope composition standard sample and application thereof

Abstract

The application discloses a preparation method of a blocky olivine iron isotope composition standard sample and application thereof, and the preparation method of the olivine standard sample comprises the following preparation steps: coarsely crushing olivine to obtain olivine coarse bodies; grinding the olivine coarse bodies, and drying to obtain olivine powder; tabletting the olivine powder to obtain an olivine blank; and sintering the blank in a protective atmosphere to obtain a blocky olivine iron isotope composition standard sample. The application proposes a micro-area iron isotope composition standard sample which is uniform in composition, easy to store, suitable for long-term use and capable of being used for in-situ iron isotope analysis of olivine micro-areas without introducing a binder.

Description

Technical Field

[0001] This invention relates to the field of micro-area in-situ metal stable isotope analysis and testing technology, specifically to a method for preparing a standard sample of bulk olivine iron isotope composition and its application. Background Technology

[0002] Peridot is one of the main minerals constituting the Earth's mantle and is the earliest crystallized product formed when magnesium-rich magma reaches the surface. Therefore, olivine is often used as a geochemical and petrological tracer of the physicochemical processes occurring during magma formation or ascent. The structural information and chemical composition of olivine can not only be used to infer the composition of primitive magma, but its compositional zoning also records important information such as the evolution of magma and environmental changes at different stages during its ascent and eruption. Compositional zoning in olivine crystals is evidence of changes in the chemical or physical conditions of the magma system; these changes, existing during evolution, include melt composition, oxygen fugacity, pressure, and volatile matter content. Therefore, the study of olivine is of great significance for inferring primitive magma and magma evolution and time-scale processes. Its elemental and isotopic composition characteristics play an important role in inverting the material composition, properties, and long-term evolution of the lithospheric mantle. With the advancement of analytical techniques and the development of new research methods, accurate determination of olivine iron isotopes has become possible. The geochemical characteristics of iron isotopes in olivine are of great significance for studying the fractionation behavior of iron isotopes in magmatic processes (such as partial melting, mantle metasomatism, and magma differentiation), understanding the processes of magmatism and mantle processes on Earth, and tracing the material sources and mineralization processes of magmatic deposits.

[0003] Laser ablation plasma mass spectrometry (LASMS) is an important method for in-situ isotope analysis of mineral micro-areas. It offers advantages such as high spatial resolution, low sample consumption, low contamination risk, and rapid, economical operation, enabling the acquisition of isotopic information at the micro-area scale. However, because LASMS analysis of isotopes is a relative method—analyzing by comparing the ratio of isotopes in the sample to a standard sample—the lack of olivine solid standard samples with homogeneous iron isotope composition and matching matrix directly limits the application of LASMS for accurate in-situ iron isotope analysis in olivine micro-areas.

[0004] Generally, to prepare standard samples for laser ablation plasma mass spectrometry isotope analysis, natural minerals are selected from nature, broken into small pieces, embedded in resin, polished, and then subjected to homogeneity testing and analytical determination to obtain the finished product. However, olivine in nature has a complex and diverse composition and poor homogeneity, resulting in a small amount of samples that meet the requirements, making it unsuitable for long-term widespread use.

[0005] Traditionally, the method for preparing relatively homogeneous solid standard samples for micro-area analysis is powder compression. This method involves directly compressing powder samples into tablets, which is simple, efficient, and rapid. However, the samples are prone to looseness, cannot be stored for long periods, and the laser beam spot, energy, and frequency have a significant impact on the sample quality during laser ablation, resulting in large errors in iron isotope analysis and failing to meet the requirements for high precision and accuracy. To improve the looseness and low density of the compressed samples, binders are usually introduced into the system to increase the strength of the tablets. However, the binders used in this method are mostly organic and cannot be removed, which can alter the matrix composition of olivine and easily introduce new impurities. Moreover, the tablets prepared by this method are still hygroscopic, cannot be polished or washed, and are difficult to store and use for long periods.

[0006] The melting method is also a commonly used method for preparing solid standard samples, but it is mainly used for elemental analysis. Because it is difficult to ensure completely uniform internal and external temperatures during the cooling and solidification process of the molten standard material, differences in solidification time occur in different regions. This leads to significant iron isotope fractionation, making it difficult to obtain a sample with homogeneous iron isotopes. Furthermore, the melting and cooling process easily causes the oxidation of ferrous iron in olivine, resulting in a fundamental change in the olivine phase.

[0007] Therefore, developing a standard sample that is homogeneous in composition, easy to store, and suitable for long-term use in micro-area analysis will be a key research objective in this field. Summary of the Invention

[0008] The main objective of this invention is to propose a method for preparing a standard sample of iron isotope composition of bulk olivine and its application. The aim is to prepare a standard sample that is homogeneous in composition, easy to store, and suitable for long-term use for in-situ iron isotope composition analysis of olivine micro-areas without introducing a binder.

[0009] To achieve the above objectives, this invention proposes a method for preparing a standard sample of iron isotope composition from bulk olivine, comprising the following preparation steps:

[0010] S1: Coarsely crush the olivine to obtain coarse olivine material;

[0011] S2: The olivine is coarsely ground and dried to obtain olivine powder;

[0012] S3: Press the olivine powder into tablets to obtain an olivine blank;

[0013] S4: The blank is sintered in a protective gas to obtain a blocky olivine iron isotope composition standard sample.

[0014] Optionally, step S2 includes adding anhydrous ethanol, isopropanol, or n-butanol to the crude olivine, followed by grinding and drying to obtain olivine powder.

[0015] Optionally, in step S2, the grinding time is 9 to 11 hours.

[0016] Optionally, in step S2, the drying temperature is 70–110°C.

[0017] Optionally, in step S3, the pressure during tablet compression is 4 to 6 MPa.

[0018] Optionally, in step S4, the sintering temperature is 1000–1300 °C; and / or the heating rate is 1–3 °C / min.

[0019] Optionally, the sintering time in step S4 is 4 to 6 hours.

[0020] Optionally, in step S4, the protective gas is argon with a volume fraction of not less than 99.999%; and / or, the protective gas is nitrogen with a volume fraction of not less than 99.999%.

[0021] Furthermore, this invention also proposes the application of a bulk olivine iron isotope composition standard sample, which is prepared by the method described above for preparing a bulk olivine iron isotope composition standard sample, and is used for quantitative analysis of olivine iron isotopes by laser ablation plasma mass spectrometry.

[0022] In the technical solution provided by this invention, olivine powder does not require the introduction of a binder during the tableting process; it is directly sintered in an atmosphere tube furnace. The resulting iron isotope standard sample is an olivine block, which is dense and not easily damaged, with a hardness higher than 370 HV, similar to the hardness of glass. It has a dense internal structure, high strength, and is not easily damaged, with a uniform iron isotope composition and δ¹⁸O⁻. 56 The 2-standard deviation (2SD) of Fe is less than 0.1‰, which meets the requirements for quantitative analysis of olivine iron isotopes by laser ablation plasma mass spectrometry. In addition, compared with samples prepared by powder pressing method, this sample can be washed and polished, is not easy to absorb moisture, and is convenient to store. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of an embodiment of the method for preparing a standard sample of the iron isotope composition of bulk olivine provided by the present invention.

[0025] Figure 2 X-ray diffraction patterns of the standard samples of iron isotope composition of bulk olivine prepared in Examples 1 to 5 of the present invention and the bulk olivine samples prepared in Comparative Examples 1 to 3.

[0026] Figure 3 This is a scanning electron microscope image of the blocky olivine iron isotope composition standard sample prepared in Example 3 of the present invention;

[0027] Figure 4 The results are the micro-area in-situ iron isotope composition analysis results of the blocky olivine iron isotope composition standard samples prepared in Examples 1 to 5 of this invention and the blocky olivine sample prepared in Comparative Example 1.

[0028] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Generally, to prepare standard samples for laser ablation plasma mass spectrometry isotope analysis, natural minerals are selected from nature, broken into small pieces, embedded in resin, polished, and then subjected to homogeneity testing and analytical determination to obtain the finished product. However, olivine in nature has a complex and diverse composition and poor homogeneity, resulting in a small amount of samples that meet the requirements, making it unsuitable for long-term widespread use.

[0031] Traditionally, the method for preparing relatively homogeneous solid standard samples for micro-area analysis is powder compression. This method involves directly compressing powder samples into tablets, which is simple, efficient, and rapid. However, the samples are prone to looseness, cannot be stored for long periods, and the laser beam spot, energy, and frequency have a significant impact on the sample quality during laser ablation, resulting in large errors in iron isotope analysis and failing to meet the requirements for high precision and accuracy. To improve the looseness and low density of the compressed samples, binders are usually introduced into the system to increase the strength of the tablets. However, the binders used in this method are mostly organic and cannot be removed, which can alter the matrix composition of olivine and easily introduce new impurities. Moreover, the tablets prepared by this method are still hygroscopic, cannot be polished or washed, and are difficult to store and use for long periods.

[0032] The melting method is also a commonly used method for preparing solid standard samples, but it is mainly used for elemental analysis. Because it is difficult to ensure completely uniform internal and external temperatures during the cooling and solidification process of the molten standard material, differences in solidification time occur in different regions. This leads to significant iron isotope fractionation, making it difficult to obtain a sample with homogeneous iron isotopes. Furthermore, the melting and cooling process easily causes the oxidation of ferrous iron in olivine, resulting in a fundamental change in the olivine phase.

[0033] In view of this, the present invention provides a method for preparing a standard sample of iron isotope composition of bulk olivine. The bulk olivine standard sample prepared by this method has a uniform distribution of iron isotope composition, and the sample is easy to store and suitable for long-term use; combined with Figure 1 The diagram shows a flowchart of an embodiment of a method for preparing a standard sample of iron isotope composition from massive olivine. The method for preparing the iron isotope standard sample includes the following steps:

[0034] Step S1: Crush the peridot to obtain coarse peridot.

[0035] Before proceeding to step S1, peridot needs to be selected. When selecting peridot, it is preferable to choose peridot with uniform texture and color distribution as the sample. Peridot with uniform texture and color distribution has less or no impurity mineral content. Using peridot to make the sample will have less interference with the test results, making the test results more reliable.

[0036] In step S1, the following steps can be taken: Select peridot with uniform texture and color distribution, crush the peridot into peridot blocks, select high-purity peridot blocks, and coarsely crush the peridot blocks to 200 mesh to obtain a coarse peridot sample.

[0037] Step S2: The olivine is coarsely ground and dried to obtain olivine powder.

[0038] In this step, the grinding method is not limited. This embodiment uses wet ball milling to obtain olivine powder, which is more efficient, produces a more uniform powder texture, and takes less time. It yields a slurry with a uniform composition, and the slurry particles are mainly spherical rather than flaky, which facilitates rapid slurry flow and results in uniform olivine powder. During wet ball milling, the added grinding aids, such as water or organic solvents, not only make the coarse olivine sample easier to grind but also prevent the grinding material from adhering to the grinding balls, thereby improving grinding efficiency.

[0039] When performing step S2, the following steps can be followed: place the olivine coarse material, small grinding balls and large grinding balls into a grinding jar, add organic solvent until the olivine coarse material, small grinding balls and large grinding balls are submerged, grind for 9 to 11 hours, and dry at a temperature of 70 to 110°C. Under the above conditions, the obtained olivine powder is more uniform.

[0040] It should be noted that in step S2, the organic solvent is not limited and can be any one of anhydrous ethanol, isopropanol or n-butanol. The purpose of adding organic solvent is to improve the dispersibility of the crude olivine sample, prevent it from agglomerating into lumps during the grinding process, and speed up the grinding effect. At the same time, the organic solvent is required to have high volatility so that the powder after ball milling is easier to dry.

[0041] In some embodiments, the large grinding ball has a diameter of 4-5 mm, and the small grinding ball has a diameter of 1.5-2 mm. Furthermore, the material of the grinding balls is not limited. In a preferred embodiment, the grinding balls are made of agate, as agate grinding balls are harder and prevent the introduction of impurities during grinding. The small agate balls have a diameter of 2 mm, and the large agate balls have a diameter of 5 mm; this selection is more conducive to grinding coarse olivine.

[0042] In some embodiments, the mass ratio of the coarse natural peridot material, large grinding beads, and small grinding beads is (0.5–1):(1.5–2):(1.5–2), meaning that 1.5–3 kg of large grinding beads and 1.5–3 kg of small grinding beads are added to every 1 kg of coarse peridot sample. In a preferred embodiment, 2 kg of small agate spheres and 2 kg of large agate spheres are added to every 1 kg of coarse peridot sample. It should be noted that in this embodiment, the mass ratio of a single large grinding bead to a single small grinding bead is 1:1. This ratio results in a more uniform peridot powder.

[0043] In some embodiments, the olivine powder has a particle size of 0.5-4 μm. This particle size range is beneficial for thoroughly mixing the olivine powder, resulting in a more uniform distribution of iron isotope composition in the final standard sample.

[0044] S3: Press the olivine powder into tablets to obtain an olivine blank.

[0045] It should be noted that in step S3, during the process of pressing the olivine powder into tablets using the direct powder pressing process, no binder is added. The pressure used during tableting is 4 to 6 MPa, preferably 4 MPa. Under these conditions, the resulting green body has a uniform texture and a smooth surface.

[0046] Step S4: Sinter the blank in a protective gas to obtain a blocky olivine iron isotope composition standard sample.

[0047] In step S4, in order to avoid the sample from reacting with oxygen during sintering, sintering needs to be carried out under the condition of a protective gas. Usually, argon or nitrogen is selected as the protective gas. Preferably, the volume fraction of argon or nitrogen is not less than 99.999% to prevent the ferrous iron in olivine from being oxidized to ferric iron during sintering.

[0048] In some embodiments, an atmosphere tube furnace sintering method is used, which has a fast heating rate and does not sinter the olivine blank into a traditional molten glass state. While preserving the properties of the sample itself, it maximizes the uniformity and stability of the iron isotope standard sample, makes it easy to store, reduces the analytical error of olivine iron isotopes caused by the loosening of the iron isotope standard sample during laser ablation, and ensures the accuracy of iron isotope analysis.

[0049] Olivine powder can be sintered directly in a tubular furnace without the need for a binder during tableting. The resulting iron isotope standard samples are dense, durable olivine blocks with a hardness exceeding 370 HV (similar to glass), a dense internal structure, high strength, and uniform iron isotope composition. 56 The 2-standard deviation (2SD) of Fe is less than 0.1‰, which meets the requirements for quantitative analysis of olivine iron isotopes by laser ablation plasma mass spectrometry. In addition, compared with samples prepared by powder pressing method, this sample can be washed and polished, is not easy to absorb moisture, and is convenient to store.

[0050] In step S4, the following steps can be used: place the blank into an alumina crucible, then place the alumina crucible in a tube furnace, extract the air from the furnace and introduce argon gas, then heat it to 1000-1300℃ at a heating rate of 1-3℃ / min and hold it for 4-6 hours. Under the above conditions, the obtained blocky olivine iron isotope composition standard sample is dense, not easily damaged, and has high hardness.

[0051] Furthermore, in order to obtain a better uniformity and harderness of the blocky olivine iron isotope composition standard sample, the sintering temperature in the atmosphere tube furnace is 1300℃ and the sintering time in the atmosphere tube furnace is 4h.

[0052] In some embodiments, after the billet is placed into the tube furnace, it is necessary to evacuate the tube furnace for 15 minutes in order to keep the oxygen fugacity in the tube furnace at a low level.

[0053] Furthermore, this invention also proposes an application of a bulk olivine iron isotope composition standard sample. This bulk olivine iron isotope composition standard sample is prepared using the method described above. The bulk olivine iron isotope composition standard sample is used for quantitative analysis of olivine iron isotopes by laser ablation plasma mass spectrometry. The application of the above-mentioned iron isotope standard sample possesses all the beneficial effects of the aforementioned iron isotope standard sample, which will not be elaborated further here.

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0055] Example 1

[0056] (1) Coarse crushing of olivine gravel: Select high-purity olivine minerals and crush them into 80μm powder to obtain coarse olivine material;

[0057] (2) Place the rough peridot, small agate spheres and large agate spheres into an agate ball milling jar in a weight ratio of 1:1.5:1.5, add anhydrous ethanol until the rough peridot, small agate spheres and large agate spheres are submerged, grind for 9 hours, and dry at 70°C to obtain peridot powder.

[0058] (3) Weigh a certain amount of olivine powder and put it into a tablet press, press it into tablets at 4MPa to obtain olivine preforms;

[0059] (4) The pressed blank is placed in a crucible and heated to 1200℃ in a tube furnace at a heating rate of 3℃ / min in an inert gas atmosphere at normal pressure. The temperature is held for 4 hours to obtain iron isotope standard samples.

[0060] Example 2

[0061] (1) Coarse crushing of olivine gravel: Select high-purity olivine minerals and crush them into 60μm powder to obtain coarse olivine material;

[0062] (2) Place the peridot rough sample, small agate spheres and large agate spheres into an agate ball milling jar in a weight ratio of 1:2:2, add anhydrous ethanol until the peridot rough sample, small agate spheres and large agate spheres are submerged, grind for 10 hours, and dry at 80℃ to obtain peridot powder.

[0063] (3) Weigh a certain amount of olivine powder and put it into a tablet press. Press it into tablets under a pressure of 5MPa to obtain olivine preforms.

[0064] (4) The pressed blank is placed in a crucible and heated to 1200℃ in a tube furnace at a heating rate of 1℃ / min in an inert gas atmosphere at normal pressure. The temperature is held for 5 hours to obtain iron isotope standard samples.

[0065] Example 3

[0066] (1) Coarse crushed olivine gravel: Select high-purity olivine minerals and crush them into 74μm powder to obtain coarse olivine material;

[0067] (2) Place the peridot rough sample, small agate spheres and large agate spheres into an agate ball milling jar in a weight ratio of 1:1.5:1.5, add anhydrous ethanol until the peridot rough sample, small agate spheres and large agate spheres are submerged, grind for 10 hours, and dry at 90°C to obtain peridot powder.

[0068] (3) Weigh a certain amount of olivine powder and put it into a tablet press, press it into tablets at 4MPa to obtain olivine preforms;

[0069] (4) The pressed blank is placed in a crucible and heated to 1300℃ in a tube furnace at a heating rate of 2℃ / min in an inert gas atmosphere at normal pressure. The temperature is held for 4 hours to obtain iron isotope standard samples.

[0070] Scanning electron microscopy results of the surface and internal cross-section of the obtained massive olivine iron isotope composition standard sample are as follows: Figure 3 As shown in the figure, the olivine standard sample has a dense accumulation of fine, rounded grains inside, indicating that the sintered body is dense. Moreover, the grains themselves have not completely melted, but rather the grains are fused and cemented together.

[0071] Example 4

[0072] (1) Coarse crushing of olivine gravel: Select high-purity olivine minerals and crush them into 80μm powder to obtain coarse olivine material;

[0073] (2) Place the peridot rough sample, small agate spheres and large agate spheres into an agate ball milling jar in a weight ratio of 1:1.8:1.8, add anhydrous ethanol until the peridot rough sample, small agate spheres and large agate spheres are submerged, grind for 11 hours, and dry at 100°C to obtain peridot powder.

[0074] (3) Weigh a certain amount of olivine powder and put it into a tablet press, press it into tablets under a pressure of 6MPa to obtain olivine preforms;

[0075] (4) The pressed blank is placed in a crucible and heated to 1300℃ in a tube furnace at a heating rate of 2℃ / min in an inert gas atmosphere at normal pressure. The temperature is held for 6 hours to obtain iron isotope standard samples.

[0076] Example 5

[0077] (1) Coarse crushing of olivine gravel: Select high-purity olivine minerals and crush them into 100μm powder to obtain coarse olivine material;

[0078] (2) Place the peridot rough sample, small agate spheres and large agate spheres into an agate ball milling jar in a weight ratio of 1:1.5:1.5, add anhydrous ethanol until the peridot rough sample, small agate spheres and large agate spheres are submerged, grind for 9 hours, and dry at 110℃ to obtain peridot powder.

[0079] (3) Weigh a certain amount of olivine powder and put it into a tablet press, press it into tablets at 4MPa to obtain olivine preforms;

[0080] (4) The pressed blank is placed in a crucible and heated to 1000℃ in a tube furnace at a heating rate of 3℃ / min in an inert gas atmosphere at normal pressure. The temperature is held for 4 hours to obtain iron isotope standard samples.

[0081] Comparative Example 1

[0082] Except for performing only steps (1), (3) and (4), the other conditions remain the same as in Example 3.

[0083] Comparative Example 2

[0084] The sintering temperature in step (4) was changed to 900℃, while other conditions remained the same as in Example 3.

[0085] Comparative Example 3

[0086] In step (4), the sintering temperature was changed to 1400℃, while other conditions remained the same as in Example 3.

[0087] Performance testing

[0088] (1) Phase testing

[0089] Phase analysis was performed on the sintered sheets of the blocky olivine standard samples prepared in Examples 1 to 5 and the olivine samples prepared in Comparative Examples 1 to 5 using X-ray diffraction (XRD). The results are shown in Table 1.

[0090] Table 1 Test Results

[0091] Example 1 No changes were observed; the diffraction peak intensity was high. High density, not easily damaged Example 2 No changes were observed; the diffraction peak intensity was high. High density, not easily damaged Example 3 No changes were observed; the diffraction peak intensity was high. High density, not easily damaged Example 4 No changes were observed; the diffraction peak intensity was high. High density, not easily damaged Example 5 No changes were observed; the diffraction peak intensity was high. High density, not easily damaged Comparative Example 1 No changes were observed; the diffraction peak intensity was high. High density, not easily damaged Comparative Example 2 No changes were observed; the diffraction peak intensity was high. Loose and easily damaged Comparative Example 3 No changes were observed; the diffraction peak intensity was high. Localized melting occurred, resulting in dark patches.

[0092] From Table 1, Figure 2 It can be concluded that the phase composition of the blocky olivine iron isotope standard samples prepared in Examples 1 to 5 did not change. In addition, the phase composition of the olivine samples prepared in Comparative Examples 1 to 3 also did not change, indicating that the solid-state sintering method under protective gas does not affect the phase composition of the samples.

[0093] (2) Hardness test

[0094] The hardness of the blocky olivine iron isotope composition standard samples prepared in Examples 1 to 5 was tested using a Vickers hardness tester. The test results are shown in Table 2.

[0095] Table 2 Test Results

[0096] Example 1 52.78 46.76 49.77 374.32 Example 2 50.98 48.20 49.59 377.05 Example 3 53.75 46.15 49.95 371.62 Example 4 51.58 47.60 49.59 377.05 Example 5 53.39 45.79 49.59 377.05

[0097] Table 2 shows that the hardness of the blocky olivine iron isotope composition standard samples prepared in Examples 1 to 5 is all higher than 370 HV. The blocky olivine standard samples prepared by the preparation method provided by this invention have high hardness, similar to that of glass, dense internal structure, and high strength, making them less prone to breakage.

[0098] Comparative Example 2, however, was sintered at an insufficient temperature, resulting in low overall density and a loose texture, causing it to break upon removal from the sintering apparatus. Comparative Example 5, on the other hand, was sintered at an excessively high temperature, leading to dark patches on the sample surface caused by partial melting.

[0099] (3) Homogeneity of iron isotope composition

[0100] Laser ablation plasma mass spectrometry was used to uniformly distribute and analyze the iron isotope composition of the blocky olivine iron isotope composition standard samples prepared in Examples 1 to 5 and the olivine sample of Comparative Example 1. The uniformity was determined by two standard deviations (2SD). The test results are shown in Table 3.

[0101] Table 3 Test Results

[0102] Example 1 0.02±0.06‰ Example 2 0.02±0.08‰ Example 3 -0.02±0.07‰ Example 4 -0.02±0.07‰ Example 5 0.01±0.07‰ Comparative Example 1 0.01±0.76‰

[0103] From Table 3 and Figure 4 It can be concluded that the iron isotope composition of the blocky olivine iron isotope standard samples prepared in Examples 1 to 5 is uniform, and the δ¹⁸ ... 56 The 2SD of Fe is less than 0.1‰. The iron isotope composition of the olivine standard sample in Comparative Example 1 has poor homogeneity and is not suitable as a standard sample.

[0104] In summary, the blocky olivine iron isotope composition standard sample prepared by the method provided by this invention has a hardness higher than 370 HV, similar to that of glass, a dense internal structure, high strength, and is not easily damaged. It also exhibits a uniform iron isotope composition and δ¹⁸O⁻. 56 The 2-standard deviation (2SD) of Fe is less than 0.1‰, which meets the requirements for quantitative analysis of iron isotopes by laser ablation plasma mass spectrometry, making it suitable as a standard sample for in-situ iron isotope composition testing in olivine micro-area.

[0105] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing a standard sample of iron isotope composition from massive olivine, characterized in that, Includes the following steps: S1: Coarsely crush the olivine to obtain coarse olivine material; S2: The olivine is coarsely ground and dried to obtain olivine powder; S3: Press the olivine powder into tablets to obtain an olivine blank; S4: The green body is heated to 1000-1300 ℃ in a protective gas at a heating rate of 1-3 ℃ / min and sintered for 4-6 h to obtain a blocky olivine iron isotope composition standard sample. In step S3, the pressure during tableting is 4-6 MPa. In step S2, the particle size of the olivine powder is 0.5-4 μm.

2. The method for preparing a standard sample of iron isotope composition of massive olivine as described in claim 1, characterized in that, In step S1: The coarse olivine particles have a grain size of less than or equal to 100 μm.

3. The method for preparing a standard sample of iron isotope composition of massive olivine as described in claim 1, characterized in that, Step S2 includes: Anhydrous ethanol, isopropanol, or n-butanol are added to the crude olivine, followed by grinding and drying to obtain olivine powder.

4. The method for preparing a standard sample of iron isotope composition of massive olivine as described in claim 1, characterized in that, In step S2: The grinding time is 9~11 hours.

5. The method for preparing a standard sample of iron isotope composition of massive olivine as described in claim 1, characterized in that, In step S2: The drying temperature is 70~110℃.

6. The method for preparing a standard sample of iron isotope composition of massive olivine as described in claim 1, characterized in that, In step S4: The protective gas is argon with a volume fraction of not less than 99.999%; and / or, The protective gas is nitrogen with a volume fraction of not less than 99.999%.

7. The application of a standard sample of iron isotope composition from massive olivine, characterized in that, The bulk olivine iron isotope composition standard sample is prepared by the method described in any one of claims 1-6, and the bulk olivine iron isotope composition is used for quantitative analysis of olivine iron isotopes by laser ablation plasma mass spectrometry.

Images