Carbon isotope composition analysis method for gas inclusion in mantle mineral rock

Abstract

The invention provides an innovative method which is used for analyzing the carbon isotope composition of a trace gas inclusion in a mantle mineral rock. Cleaning the cavity of the ball mill and the mineral rock sample in the cavity by adopting protective gas so as to remove possible gas impurities; the method comprises the following steps: putting a mantle mineral rock sample into a micro-cavity of a three-dimensional high-energy vibration ball-milling instrument, and carrying out vibration ball-milling treatment; the released gas inclusion is transferred into a gas chromatography-isotope ratio mass spectrometry system through a sealed rotary three-way valve, and accurate carbon isotope composition analysis is carried out. And the risk of non-native gas pollution can be remarkably reduced through a normal-temperature crushing technology. An ultra-trace gas extraction technology and an efficient pre-concentration technology are combined, and effective recovery and enrichment of trace gas in the gas inclusion of the mantle mineral rock are realized. By adopting a high-sensitivity and high-precision isotope ratio measurement technology, the detection limit is improved, background interference is effectively reduced, and the reliability of an analysis result is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of mantle mineral rocks, and in particular to a method for analyzing the carbon isotope composition of gas inclusions in mantle mineral rocks. Background Art

[0002] The techniques for analyzing gas inclusions in common minerals and rocks currently include thermal explosion and vacuum crushing. These two methods are used in geology, petroleum geology, and mineral deposit research to study the composition of gases, especially trace gas inclusions enclosed in rocks. The following is a brief description of these two techniques:

[0003] Thermal explosion method: This method involves heating ordinary samples containing gas inclusions to high temperatures (usually hundreds to thousands of degrees Celsius), causing the inclusions to break and release the gas inside. The released gas is then collected and analyzed. Advantages: It can handle inclusions that are difficult to break by physical methods and is suitable for studying gas components that may exist under high temperature conditions. Disadvantages: Non-native gas components may be produced during the heating process, such as due to the decomposition of minerals or pyrolysis of organic matter at high temperatures, resulting in contamination of the analysis results and not a true reflection of the original fluid.

[0004] Vacuum crushing method: Mechanically crush ordinary geological samples in a vacuum environment to release gases from gas inclusions, and then collect these gases for analysis while maintaining a vacuum. Advantages: Compared with the thermal explosion method, this method reduces the possibility of pyrolysis reactions, can more truly reflect the original gas composition, and is suitable for the detection of low-content gases. Disadvantages: Although the problem of thermal contamination is reduced, other forms of contamination may still exist, such as contamination from the experimental background. At the same time, for very small or extremely hard inclusions, a strong crushing force may be required, which may be technically difficult to achieve, and it may still be difficult to achieve extremely low levels of analytical sensitivity.

[0005] Existing mineral rock gas inclusion analysis techniques mostly focus on crustal rocks, especially those samples with relatively high gas content, such as sedimentary rocks. For these samples, the commonly used vacuum crushing technology can extract gas inclusions in a low-oxygen environment, reducing oxidation reactions and external contamination, but for the analysis of ultra-trace alkane inclusions in mantle rocks, this technology has certain limitations: ① Cavity background contamination problem: The gas inclusion content in mantle rocks is extremely low, and the use of conventional vacuum crushing technology is very easy to introduce background contamination, because nitrogen in the air is very easy to mix in, especially during the processing process, even a very small amount of contamination may have a significant impact on the analysis results. Tiny gas inclusions in mantle samples are more likely to be exposed to pollution sources during processing, making it difficult for the analysis results to reflect the true composition of the original mantle gas. ② Non-native gas release caused by heating: Heating rock samples to release gas is a common method, but this is particularly tricky in mantle rocks. Mantle rocks have experienced extreme high temperature and high pressure conditions, their structure is compact and may contain high-pressure phase minerals. When heated, in addition to releasing the original inclusion gas, it may also induce the decomposition of organic matter in the mineral structure, leading to the mixing of non-native gases, affecting the accuracy of the analysis results.

[0006] Although technology has made significant progress in the past few decades, the extraction of gases (especially trace gases) from mantle minerals and rocks and their isotopic analysis are still complex technologies. The main reasons include: ① Difficulty in sample acquisition: It is difficult to directly obtain mantle samples, which limits the scope and repeatability of the research. ② Trace gas capture and preservation: The gas content in mantle gas inclusions is extremely low. How to effectively extract these trace gases and prevent external contamination is a major technical problem. ③ Isotope analysis accuracy: The isotope ratio of mantle gas can provide key geochemical information, but requires the analysis technology to have extremely high sensitivity and accuracy. Isotope analysis technology, especially for high-precision isotope ratio determination of alkane gases such as methane, still faces challenges.

[0007] The current technical challenges of methane gas inclusions in mineral rocks: mainly include two core difficulties: ① The content of methane inclusions in mantle rocks is low, which requires highly sensitive and precise extraction technology to ensure that a sufficient amount of gas is effectively separated for analysis. This not only tests the sophistication of sampling and processing technology, but also requires innovative pre-concentration strategies to enrich these tiny gas components. ② Strict pollution control: Since nitrogen is the main component of the atmosphere, it is an extremely difficult task to avoid modern atmospheric nitrogen pollution during collection, processing and even analysis. Any tiny contamination may cause distortion of the analysis results and seriously affect the judgment of the true gas composition and isotope ratio of the mantle. This requires that the experimental environment must be highly pure, and strict nitrogen-free or ultra-clean operating procedures must be adopted, as well as isotope tracing and blank tests. Methods such as testing and correcting possible contamination. Summary of the invention

[0008] The present invention aims to solve the above technical problems and provides a method for analyzing the carbon isotope composition of gas inclusions in mantle mineral rocks.

[0009] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0010] A method for analyzing the carbon isotope composition of gas inclusions in mantle mineral rocks comprises the following steps:

[0011] S1. Sample preparation:

[0012] Select mantle mineral rocks, which should be of uniform size, with a particle size of 0.5-1 mm;

[0013] S2. Preparation of high energy micro-cavity vibration ball mill:

[0014] Grinding balls are added to the high-energy micro-cavity vibration ball mill, dispersant is added before grinding, and mantle mineral rocks are put into the high-energy micro-cavity vibration ball mill for grinding;

[0015] S3, inert gas flushing:

[0016] Use inert gas to repeatedly flush the cavity of the high-energy micro-cavity vibration ball mill for 10-30 minutes to completely replace the original air in the cavity;

[0017] S4. Gas analysis:

[0018] After the ball milling process, the crushed samples are collected and the gas inclusions that may be released are recovered through separation technology. The gas inclusions are transferred to the gas chromatography-isotope ratio mass spectrometry analysis system through a closed three-way rotary valve for precise analysis of the composition and isotope ratio.

[0019] Preferably, the ratio of the grinding balls to the mantle mineral rock is 1:3.

[0020] Preferably, the purity of the inert gas is 99.9999%.

[0021] Preferably, the mantle mineral rock is olivine, pyroxene or garnet.

[0022] Preferably, the grinding balls are stainless steel balls, ceramic balls or zirconium balls. The grinding balls are high hardness grinding balls.

[0023] Preferably, the gas chromatography-isotope ratio mass spectrometry analysis system is a system in which gas inclusions pass through a gas chromatography, an oxidation furnace, a water removal device and an isotope ratio mass spectrometer in sequence through a closed three-way rotary valve.

[0024] Preferably, the parameters of the gas chromatography are: initial temperature of 30-40°, maintained for 3-7 min, heating rate of 8-12° / min, final temperature of 200°C, maintained for 26-32 min, split ratio: 5:1, carrier gas is helium, flow rate is 5 ml / min, and enters isotope ratio mass spectrometry monitoring 12 CO2 / 13 CO2 ratio, calculate δ 13 C value.

[0025] Preferably, the high-energy micro-cavity vibration ball mill includes a bottom plate and a motor and a bearing seat connected to the bottom plate, a rotating shaft is installed in the bearing seat, the motor and the rotating shaft are connected by a belt and a pulley, one end of the rotating shaft is connected to a rocker, a fixed plate is installed on one side of the rocker, a ball mill is installed in the fixed plate, and a spring is installed between the rocker and the bottom plate.

[0026] Preferably, the rotation speed of the high-energy micro-cavity vibration ball mill is 1500-1800 r / min, the temperature in the ball mill does not exceed 60°, and the frequency is 20-50 Hz.

[0027] Preferably, the gas inclusion gas chromatography-isotope ratio mass spectrometry analysis system analyzes methane, nitrogen, hydrogen, carbon dioxide, ethane components and their respective isotope ratios.

[0028] After adopting the above method, the present invention has the following advantages:

[0029] The present invention safely collects gas inclusions from trace and ultra-trace mantle rock samples that are difficult to obtain, while reducing the risk of sample damage and external contamination. Combining ultra-trace extraction with high-efficiency pre-concentration technology, it can effectively recover and enrich trace gases from very small amounts of mantle gas inclusions, and use high-sensitivity and high-precision isotope ratio measurement technology for mantle gases, using isotope ratio mass spectrometry or improved mass spectrometry analysis to improve detection limits, reduce background interference, and ensure data accuracy.

[0030] The above summary is intended to provide illustration only and is not intended to be limiting in any form. In addition to the exemplary aspects, embodiments and features described above, other embodiments and features of the present invention will become more apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is a diagram showing the detection results of gas inclusions of the present invention;

[0033] Figure 2 Schematic diagram of the high-energy micro-cavity vibration ball mill of the present invention;

[0034] Figure 3 It is a structural schematic diagram of the closed three-way rotary valve of the present invention;

[0035] Figure 4 It is a schematic diagram of the gas chromatography-isotope ratio mass spectrometry analysis system of the present invention.

[0036] As shown in the figure: 1. Base plate; 2. Motor; 4. Bearing seat; 5. Rocker; 6. Belt; 7. Fixed plate;

[0037] A. Rotating handle; B. Syringe port; C. Three-way side outlet; D. Three-way valve body; E. Three-way valve front outlet; F. Needle. DETAILED DESCRIPTION

[0038] Specific embodiments of the present invention will now be mentioned in detail. Although the present invention is described in conjunction with these specific embodiments, it should be appreciated that it is not intended to limit the present invention to these specific embodiments. On the contrary, these embodiments are intended to cover substitutions, changes or equivalent embodiments that may be included in the spirit and scope of the invention defined by the claims. In the following description, a large number of specific details are set forth in order to provide a comprehensive understanding of the present invention. The present invention can be implemented without some or all of these specific details. In other cases, in order not to make the present invention unnecessarily obscure, well-known process operations are not described in detail.

[0039] When used in conjunction with "including," "methods comprising," or similar language in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0040] The present invention is further described in detail below in conjunction with the full text.

[0041] Combined with Figure 1-Figure 4, a method for analyzing the carbon isotope composition of gas inclusions in mantle mineral rocks, comprising the following steps:

[0042] S1. Sample preparation:

[0043] Select mantle mineral rocks, which should be of uniform size, with a particle size of 0.5-1 mm;

[0044] S2. Preparation of high energy micro-cavity vibration ball mill:

[0045] Grinding balls are added to the high-energy micro-cavity vibration ball mill, dispersant is added before grinding, and mantle mineral rocks are put into the high-energy micro-cavity vibration ball mill for grinding;

[0046] S3, inert gas flushing:

[0047] Use inert gas to repeatedly flush the cavity of the high-energy micro-cavity vibration ball mill for 10-30 minutes to completely replace the original air in the cavity; the inert gas can be helium, hydrogen or other.

[0048] S4. Gas analysis:

[0049] After the ball milling process, the crushed samples are collected and the gas inclusions that may be released are recovered through separation technology. The gas inclusions are transferred to the gas chromatography-isotope ratio mass spectrometry analysis system through a closed three-way rotary valve for precise analysis of the composition and isotope ratio.

[0050] The ratio of the grinding balls to the mantle mineral rocks is 1:3.

[0051] The purity of the inert gas is 99.9999%.

[0052] The mantle mineral rock is olivine, pyroxene or garnet, etc.

[0053] The grinding balls are stainless steel balls, ceramic balls or zirconium balls, and the grinding balls are high-hardness grinding balls.

[0054] The gas chromatography-isotope ratio mass spectrometry analysis system is a system in which gas inclusions pass through a gas chromatography, an oxidation furnace, a water removal device and an isotope ratio mass spectrometry in sequence through a closed three-way rotary valve.

[0055] The gas chromatography method is as follows: the initial temperature of the chromatography is 30-40°, maintained for 3-7 minutes, the heating rate is 8-12° / min, the final temperature is 200 degrees, maintained for 26-32 minutes, the split ratio is 5:1, the carrier gas is helium, the flow rate is 5ml / min, and the isotope ratio mass spectrometry is monitored. 12 CO2 / 13 CO2 ratio, calculate δ 13 C value.

[0056] The high-energy micro-cavity vibration ball mill comprises a bottom plate and a motor and a bearing seat connected to the bottom plate, a rotating shaft is installed in the bearing seat, the motor and the rotating shaft are connected through a belt and a pulley, one end of the rotating shaft is connected to a rocker, one side of the rocker is installed with a fixed plate, a ball mill is installed in the fixed plate, and a spring is installed between the rocker and the bottom plate. When the motor works, the rocker is driven to rotate through the rotating shaft, the fixed plate is fixedly connected to the ball mill through a flange, and the ball mill and the rotating shaft are set at an inclined angle.

[0057] The core of the high-energy vibration ball milling technology of the high-energy micro-cavity vibration ball mill lies in its unique vibration mechanism, which ensures that the grinding balls and samples in the ball mill cavity are always in a highly dynamic state of motion. This continuous, high-intensity motion is the key to achieving efficient grinding. Specifically, this state of motion is mainly reflected in the following aspects: ① Three-dimensional motion: Different from the single axial rotation of the traditional high-energy micro-cavity vibration ball mill, the high-energy vibration ball mill of the high-energy micro-cavity vibration ball mill usually adopts a three-dimensional motion mode, that is, the grinding balls not only rotate around the central axis of the container, but also perform complex vibrations and swings in the vertical and horizontal directions. This multi-dimensional motion greatly increases the collision frequency and energy between the grinding balls and accelerates the grinding process. ② High-frequency vibration: Driven by a motor, high-frequency vibration is generated, causing the grinding balls to continuously jump, roll and collide in the ball mill cavity. High-frequency vibration not only improves the grinding efficiency, but also reduces the formation of large particles, ensuring more uniform grinding.

[0058] The grinding balls not only revolve with the entire container in the ball mill chamber, but also ensure that each grinding ball surface can contact the sample, thus improving the comprehensiveness and uniformity of grinding. ④ Dynamic balance: Although the grinding balls and samples are in high-speed motion, a well-designed high-energy vibration ball mill can ensure that the collision between the grinding balls and between the grinding balls and the chamber wall is carried out in a relatively gentle state, avoiding excessive wear and equipment damage, while also ensuring the stability and safety of the grinding process. ⑤ Continuously updating the contact surface: Due to the continuous movement of the grinding balls and samples, new contact surfaces are constantly created, which helps to break the structure of the material more quickly, promote the generation of fine particles, and improve grinding efficiency and fineness.

[0059] The rotation speed of the high-energy micro-cavity vibration ball mill is 1500-1800r / min, the temperature in the ball mill does not exceed 60°, and the frequency is 20-50Hz. The procedure for starting the ball mill and how to monitor the key temperature indicators during the grinding process (temperature, using an infrared thermometer to monitor the tank body does not exceed 60 degrees) ensures that the temperature does not rise too fast during the grinding process, stops grinding when it exceeds 60 degrees, avoids the generation of interfering gases, and ensures safe operation and achieves the expected grinding effect.

[0060] The gas inclusion gas chromatography-isotope ratio mass spectrometry analysis system analyzes the components of methane gas, nitrogen gas, hydrogen gas, carbon dioxide, ethane and their respective isotope ratios.

[0061] Operation process: ① Sample preparation: First, carefully select the suitable parts for analysis from the rock samples of the mantle source to ensure that the selected samples are representative and of research value. ② Micro-chamber: The selected mineral rock samples are broken into appropriate particle sizes. The chamber is designed to minimize the contact between the sample and the external environment. The chamber is filled with inert gas to exclude oxygen and moisture and protect the sample from oxidation or hydrolysis. ③ High-energy vibration ball milling: At room temperature, a micro-chamber vibration ball mill equipped with hard grinding balls is used to perform high-intensity mechanical vibration and rotation on the sample in the micro-chamber. Through the high-frequency collision and friction between the balls, the mineral rock is gradually physically broken into smaller particles, and even the gas inclusions inside are released. ④ Collection and analysis: After the ball milling process is completed, the crushed samples are collected, and the gas inclusions that may be released are recovered through appropriate separation techniques (such as centrifugation and screening). Subsequently, the chemical composition of these gases is analyzed to reveal geological information deep in the mantle, such as the composition, temperature, pressure conditions of the mantle, and the early evolution history of the Earth.

[0062] When the present invention is implemented, Figure 4 As shown in Figure 1, for the carbon isotope ratio analysis of methane (CH4) in gas inclusions (focusing on δ13C), the experimental conditions can be summarized as follows when using the gas chromatography-isotope ratio mass spectrometry (GC-IRMS) method: Ensure that the gas sample is free of moisture and impurities that may interfere with the analysis before injection. Standard preparation: Prepare a methane standard with a known δ13C value for instrument calibration.

[0063] Chromatographic conditions (GC part): Use a permanent gas analysis column (chromatographic column model: J&W HP-PLOT-Q; 30m, 0.53mm, 40.00μm) Column temperature: Set the initial temperature of the chromatographic column to 35 degrees, maintain for 5 minutes, heating rate 10 degrees / min, final temperature 200 degrees, maintain for 30 minutes, split ratio: 5:1, carrier gas: high-purity helium, flow rate 5ml / min, to ensure that the sample is effectively transmitted to the mass spectrometer. Isotope ratio mass spectrometry conditions (model: DELTAVPlus) or similar high-precision isotope ratio mass spectrometer. Isotope ratio monitoring 44 / 45 (corresponding to 12 CO2 / 13 CO2) ratio, calculate δ 13 C value. Calibration: Run standards before and after analysis to calibrate the instrument and ensure the accuracy of the results.

[0064] In order to avoid pollution, the present invention adopts inert gas protection to effectively avoid chemical contamination of samples during the processing process. High-energy vibration ball milling carried out under room temperature conditions can achieve efficient and fine physical crushing and release gas inclusions therein without changing the chemical properties of the sample. It helps to better preserve the original state of the gas inclusions and improve the accuracy and reliability of subsequent gas composition analysis. This method is applicable to the study of a variety of mantle minerals and is of great significance for understanding the deep processes of the earth. In short, this technology is an important tool for exploring the secrets of the deep earth. It can help scientists obtain key information about the composition of mantle materials and geodynamic processes without destroying the original characteristics of the samples.

[0065] The micro-chamber design is particularly suitable for processing extremely small amounts of samples, reducing sample loss and improving the sensitivity and accuracy of gas analysis.

[0066] The closed micro-cavity environment and efficient vibration grinding are conducive to the release, concentration and enrichment of trace gases in the sample, which is crucial for the analysis of rare or trace gases. The micro-cavity structure is easy to connect directly to the gas chromatography-mass spectrometry instrument, which simplifies the sample processing process and reduces contamination and loss during the transfer process.

[0067] As an inert gas, helium can effectively isolate oxygen and other active gases, avoid unnecessary chemical reactions during the grinding process, and maintain the original state of the sample. The helium environment helps to create a stable grinding condition, especially for samples that are sensitive to oxygen, such as easily oxidized substances, to obtain purer grinding products. In some cases, the flow of helium can also help promote the release of gas inclusions in the sample, improving the efficiency and recovery rate of gas analysis. Facilitate the transfer and analysis of gas inclusion samples: The micro-chamber design simplifies the transition process from sample processing to analysis. The sample can be directly transferred to the analysis system under a protective atmosphere, reducing external interference. Due to the reduction of sample processing steps and external contact, the original information of the gas inclusions can be better preserved, improving the accuracy and reliability of the final analysis results. The high-energy micro-chamber vibration ball milling technology combined with the helium protective atmosphere not only improves the efficiency and accuracy of ultra-trace gas processing.

[0068] Embodiment 1:

[0069] Take a typical mantle peridotite as an example: ① Sample preparation: Pre-process the mantle peridotite sample to an appropriate size to ensure that it meets the feed particle size requirements of the high-energy micro-cavity vibration ball mill, 1mm, to reduce the damage of the ball mill cavity by oversized particles and improve the grinding efficiency. ② Reasonable selection of grinding media: Use grinding balls of appropriate size, density and hardness. Grinding balls should be made of zirconium oxide. Too large will cause excessive impact force and cause agglomeration; too small will result in low grinding efficiency. At the same time, the material of the grinding medium should be compatible with the sample to avoid introducing impurities or reactions. ③ Optimize the ball-to-material ratio: The ball-to-material ratio (the mass ratio of grinding balls to samples) directly affects the grinding effect. Too high a ratio may lead to over-grinding and agglomeration, while too low a ratio will result in insufficient grinding. The optimal ball-to-material ratio was determined to be 1:3 by experiment. ④ Use dispersant: For samples that are easy to agglomerate, an appropriate amount of dispersant can be added before grinding to increase the lubricity between samples and reduce agglomeration; ⑤ Set atmosphere conditions: Ensure that the ball mill cavity is well sealed, and use 99.9999% pure inert gas to flush the sample to exclude oxygen, nitrogen and other gas interference in the air, and prevent the sample from oxidizing during the grinding process; ⑥ Adjust vibration parameters: Appropriately adjust the vibration frequency and ball milling time to find the grinding conditions that best suit the sample characteristics. High-frequency vibration helps reduce the mutual attraction between particles and reduce the risk of agglomeration.

[0070] High-energy three-dimensional vibration parameters: According to the properties and goals of mantle peridotite (such as releasing nitrogen inclusions), set appropriate vibration frequency and amplitude, and three-dimensional vibration accelerates this process to make gas release easier, avoid sample agglomeration, and make inclusions easier to release.

[0071] Subsequent processing and analysis: After ball milling, samples are collected and the released gases are detected and analyzed by appropriate methods (such as gas chromatography and mass spectrometry) to understand the composition and distribution characteristics of gas inclusions in mantle peridotite.

[0072] Embodiment 2:

[0073] Gas isotope analysis process steps:

[0074] Step 1: gas chromatography separation;

[0075] Injection: The purified and concentrated gas sample is injected into the gas chromatograph through the closed three-way rotary valve technology.

[0076] Chromatographic column separation: The gas components are separated by a chromatographic column by utilizing the differences in the distribution coefficients of different gases on the stationary phase.

[0077] Step 4: Online conversion:

[0078] For gases that need to be converted (such as methane to CO2), chemical reactions are carried out online through a catalytic converter. For gases that do not need to be converted (such as nitrogen), they are directly sent to a mass spectrometer.

[0079] Step 5: Isotope ratio mass spectrometry analysis

[0080] Helium carrier gas: Helium is used as carrier gas to carry the gas sample into the ion source.

[0081] Ionization: Sample molecules are ionized in the ion source and converted into charged ions.

[0082] Mass analysis: Ions are separated by a magnetic or electric field based on their mass-to-charge ratio (m / z).

[0083] Isotope ratio determination: measure the abundance of ions with different isotopes and calculate the isotope ratio.

[0084] like Figure 1 As shown in the figure, the horizontal axis of the isotope analysis spectrum of mantle peridotite gas inclusions is the retention time / second; the vertical axis represents the peak height (unit: millivolt mv).

[0085] In the field of isotope research, especially in stable isotope geochemistry and environmental science, "δ" (delta) is a commonly used symbol to express the deviation of isotope ratios relative to a standard sample, usually expressed in parts per thousand (‰, permil). This representation method allows data from different laboratories to be compared.

[0086] Rsample is the ratio of two isotopes in the sample (such as 13C / 12C),

[0087] Rstandard is an internationally recognized standard material.

[0088] The calculation formula of δ value is as follows:

[0089]

[0090] The isotopic analysis data of methane and carbon dioxide gas inclusions (PDB,‰) are shown in the following table.

[0091] Number of analyses Methane peak area (vs) <![CDATA[δ 13 C CH4 ]]> <![CDATA[C02 peak area (vs)]]> <![CDATA[δ 13 C CO2 ]]> 1 0.66 -42.35 0.26 -19.07 2 0.53 -42.04 0.26 -18.72 3 0.61 -43.09 0.22 -19.08

[0092] The present invention safely collects gas inclusions from trace, ultra-trace and difficult-to-obtain mantle rock samples, while reducing the risk of sample damage and external contamination. Combined with ultra-trace extraction and high-efficiency pre-concentration technology, it is possible to effectively recover and enrich trace gases, such as methane, from very small amounts of mantle gas inclusions, ensuring that the purity and concentration of the gas before analysis meet the requirements of high-precision isotope analysis, and using high-sensitivity, high-precision isotope ratio measurement technology for mantle gases (especially methane), using isotope ratio mass spectrometry or improved mass spectrometry to improve detection limits, reduce background interference, and ensure data accuracy. The present invention will greatly advance the boundaries of mantle fluid and gas inclusion research, provide richer and more accurate data support for understanding the deep processes of the Earth, material circulation, mantle dynamics, and the early history of the Earth, and also open up new ways to explore cutting-edge scientific issues such as the origin of life on Earth and climate change.

[0093] The present invention and its embodiments are described above, and such description is not restrictive. What is shown in the full text is only one of the embodiments of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for analyzing the carbon isotope composition of gas inclusions in mantle mineral rocks, characterized in that: The following steps are involved: S1. Sample preparation: Select mantle mineral rocks, which should be of uniform size, with a particle size of 0.5-1 mm; S2. Preparation of high energy micro-cavity vibration ball mill: Grinding balls are added to the high-energy micro-cavity vibration ball mill, dispersant is added before grinding, and mantle mineral rocks are put into the high-energy micro-cavity vibration ball mill for grinding; S3, inert gas flushing: Use inert gas to repeatedly flush the cavity of the high-energy micro-cavity vibration ball mill for 10-30 minutes to completely replace the original air in the cavity; S4. Gas analysis: After the ball milling process, the crushed samples are collected and the gas inclusions that may be released are recovered through separation technology. The gas inclusions are transferred to the gas chromatography-isotope ratio mass spectrometry analysis system through a closed three-way rotary valve for precise analysis of the composition and isotope ratio.

2. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The ratio of the grinding balls to the mantle mineral rocks is 1:

3.

3. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The purity of the inert gas is 99.9999%.

4. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The mantle mineral rock is olivine, pyroxene or garnet.

5. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The grinding balls are stainless steel balls, ceramic balls or zirconium balls.

6. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The gas chromatography-isotope ratio mass spectrometry analysis system is a system in which gas inclusions pass through a gas chromatography, an oxidation furnace, a water removal device and an isotope ratio mass spectrometry in sequence through a closed three-way rotary valve.

7. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 6, characterized in that: The gas chromatography parameters are as follows: initial temperature of 30-40°C, maintained for 3-7 min, heating rate of 8-12° / min, final temperature of 200°C, maintained for 26-32 min, split ratio: 5:1, carrier gas is helium, flow rate is 5 ml / min, and enters isotope ratio mass spectrometry monitoring 12 CO2 / 13 CO2 ratio, calculate δ 13 C value.

8. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The high-energy micro-cavity vibration ball mill includes a bottom plate and a motor and a bearing seat connected to the bottom plate, a rotating shaft is installed in the bearing seat, the motor and the rotating shaft are connected by a belt and a pulley, one end of the rotating shaft is connected to a rocker, one side of the rocker is installed with a fixed plate, a ball mill is installed in the fixed plate, and a spring is installed between the rocker and the bottom plate.

9. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 8, characterized in that: The rotation speed of the high-energy micro-cavity vibration ball mill is 1500-1800r / min, the temperature in the ball mill does not exceed 60°, and the frequency is 20-50Hz.

10. The method for analyzing carbon isotope composition of gas inclusions in mantle mineral rocks according to claim 1, characterized in that: The gas inclusion gas chromatography-isotope ratio mass spectrometry analysis system analyzes the components of methane, nitrogen, hydrogen, carbon dioxide, ethane and their respective isotope ratios.

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