Method and system for correcting pyrrholite sulfur isotope measurements based on sims

Abstract

The application provides a method and system for correcting pyrrhotite sulfur isotope measurement value based on SIMS, and belongs to the field of mineral geology element measurement and correction. The method comprises the following steps: preparing pyrite standard sample, first and second pyrrhotite standard samples and a to-be-measured sample into sample targets; measuring the standard sample analysis points and sample test points in the targets by using SIMS 34 S / 32 S ratio R M ; calculating the sulfur isotope measurement value according to R M ; calculating the average value of the pyrite standard sample measurement value, querying the recommended value, and subtracting the first fractionation value; similarly, the second fractionation value of each analysis point of the first and second pyrrhotite standard samples is obtained, and the difference between each second fractionation value and the first fractionation value is calculated; taking Δ IMF Std,j as the dependent variable y IMF Std,j / R M,j as the independent variable x , a regression equation y kx + b is constructed, and then the difference of the fractionation value of each test point is obtained by reverse solving, and the recommended value of each test point is calculated. The application improves the accuracy of the pyrrhotite sulfur isotope measurement value.​​​

Description

TECHNICAL FIELD

[0001] The application belongs to the field of mineral geologic element measurement and correction, and particularly relates to a method and system for correcting pyrrhotite sulfur isotope measurement values based on SIMS. BACKGROUND

[0002] Sulfur is the 10th most abundant element in the universe and the 14th most abundant element in the crust, and is widely distributed in the atmosphere, hydrosphere, biosphere, lithosphere and various layers of the earth interior. Sulfur has four stable isotopes, and is an important tracer for the study of atmospheric activity, microbial action, biological extinction events, rock and mineral formation processes, early surface environment evolution, early evolution of terrestrial planets, and subduction zone sulfur cycle. The sulfur isotope composition of natural substances is determined by the ratio of 34 S / 32 S values. δ 34 In geological materials such as rocks, atmospheric aerosols, water, ice and meteorites, the ratio of 34 S / 32 S values is affected by different geological, atmospheric, biological and hydrological processes, and has a large variation range. The sulfur isotope composition analysis method is often used to analyze the sulfur isotopes in pyrrhotite. Pyrrhotite is widely present in meteorites, Archean sediments on Earth and various magmatic-hydrothermal deposits, such as copper-nickel sulfide deposits. The variation of pyrrhotite sulfur isotopes can be used to interpret the evolution history of planets, the Archean atmospheric environment of the Earth and the genesis of metal deposits. Therefore, accurate measurement of the sulfur isotope composition of pyrrhotite is a key prerequisite for geological analysis based on pyrrhotite.

[0003] Methods for analyzing sulfur isotope composition include macroscopic analysis and micro-area analysis. While macroscopic analysis offers high precision, it requires cumbersome chemical pretreatment processes, large sample volumes, and cannot distinguish individual mineral grains, making it difficult to obtain sulfur isotope compositions of different mineral structures. Micro-area analysis, on the other hand, can identify the sulfur isotope composition of different zonations within the same mineral grain, providing detailed information on in-situ geological events in micro-areas that cannot be obtained through whole-rock analysis. This provides strong geochemical evidence for major scientific questions such as magmatic-hydrothermal mineralization, paleoclimate evolution, and the sulfur cycle. In many geological bodies, pyrrhotite has a small grain size; for example, in meteorites and melt inclusions, pyrrhotite grains are only about 30 μm in size. Therefore, micro-area analysis is necessary when analyzing the sulfur isotope composition of pyrrhotite. Micro-area in-situ isotope analysis typically includes ion probe microanalysis (SIMS) and laser ablation multiple receiver inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). For measuring the sulfur isotope composition of pyrrhotite, SIMS offers higher precision, sensitivity, and spatial resolution compared to LA-MC-ICP-MS, and is therefore more commonly used. While SIMS boasts superior spatial resolution, precision, and sensitivity, its accuracy is affected by matrix effects. Furthermore, pyrrhotite exhibits non-stoichiometry and develops into a series of polymorphs, such as troilite (FeS), monoclinic pyrrhotite (Fe7S8), and hexagonal pyrrhotite (Fe9S8). 10 Fe 10 S 11 and Fe 11 S 12 Pyrrhotite, with its extremely complex chemical composition and crystal structure, exhibits a wide variety of minerals, which affects the accuracy of obtaining its sulfur isotope composition. Therefore, when using SIMS to measure the sulfur isotope composition of pyrrhotite, it is necessary to correct the measured values ​​to improve accuracy.

[0004] In existing technologies, the calibration method for measuring the sulfur isotope composition of pyrrhotite using SIMS generally corrects the isotope ratio measurements of unknown samples by using matrix-matched reference materials (RMs) (minerals with the same chemical composition and structure) to eliminate the influence of matrix effects during SIMS analysis. However, in actual experiments, it is impossible to use RMs that perfectly match the chemical composition and crystal structure of the sample to completely eliminate the influence of matrix effects. Therefore, the correction effect on the measured values ​​is poor, the improvement in measurement accuracy is limited, and results close to the true values ​​cannot be obtained. Summary of the Invention

[0005] In view of the above defects or deficiencies in the prior art, the present application aims to provide a method and system for correcting pyrrholite sulfur isotope measurement values based on SIMS, which adopts pyrite and pyrrholite standards to jointly correct the matrix effect caused by the crystal structure of pyrrholite, so as to obtain more accurate pyrrholite sulfur isotope composition and improve the measurement accuracy.

[0006] In order to achieve the above-mentioned purpose, the embodiments of the present application adopt the following technical solutions:

[0007] In the first aspect, the embodiments of the present application provide a method for correcting pyrrholite sulfur isotope measurement values based on SIMS, which comprises the following steps:

[0008] Step S1, pyrite standards, first pyrrholite standards, second pyrrholite standards and samples to be measured are made into an ion probe SIMS sample target with the same particle size;

[0009] Step S2, the SIMS is used to measure the ratios of N+2 analysis points in the pyrite standards, P and Q analysis points in the two pyrrholite standards respectively, and X test points in the sample target; 34 S / 32 S ratio R M ; there are T=N+P+Q+X+2 points in total;

[0010] Step S3, the sulfur isotope measurement values of all points are calculated according to the following formula: R M

[0011] Step S4, the average value of the sulfur isotope measurement values of N or N+2 analysis points in the pyrite standards is calculated, and the recommended value of the pyrite standards is inquired at the same time, so that the recommended value is subtracted from the average value to obtain the instrument fractionation value of the pyrite standards, and a first fractionation value is obtained;

[0012] Step S5, the recommended values of the first and second pyrrholite standards are inquired respectively, and the recommended values are subtracted from the sulfur isotope measurement values of each analysis point of the corresponding standards respectively, so that the instrument fractionation values of each analysis point of the two pyrrholite standards are obtained, and P+Q second fractionation values are obtained;

[0013] Step S6, the difference between the P+Q second fractionation values and the first fractionation value is calculated, and P+Q Δ IMF Std,j ;

[0014] Step S7, Δ IMF Std,j of each corresponding analysis point is calculated according to the following formula: IMF Std,j / R M,j ; and Δ​IMF Std,j as the dependent variable y , with Δ IMF Std,j / R M,j as the independent variable x , a regression equation is constructed using linear fitting y = kx + b , and the regression coefficients k and b are solved

[0015] Step S8, taking the instrument fractionation value difference Δ IMF Sam,d as the dependent variable y , with Δ IMF Sam,d / R M,d as the independent variable x , the instrument fractionation value difference Δ y = kx + b is solved according to the regression equation IMF Sam,d ;

[0016] Step S9, the instrument fractionation value of each test point of the pyrrhotite sample is calculated according to the instrument fractionation value difference Δ IMF Sam,d of each test point of the pyrrhotite sample and the first fractionation value, and the recommended value of each test point of the sample is obtained according to the measured value of the corresponding test point.

[0017] As a preferred embodiment of the present application, in step S1, the pyrite sample uses one of the Sonora, PPP-1, Balmat and Ruttan standard samples.

[0018] As a preferred embodiment of the present application, in step S1, the first pyrrhotite standard sample and the second pyrrhotite standard sample are selected from one of Po-10, JC-Po, YP136, Anderson and Alexo, and the first pyrrhotite standard sample and the second pyrrhotite standard sample are different.

[0019] As a preferred embodiment of the present application, in step S1, the particle size of the standard sample and the sample is 100-150 μm.

[0020] As a preferred embodiment of the present application, the measurement process of step S2 includes: first, continuously measuring the instrument fractionation value of N analysis points in the pyrite standard sample R M ; then continuously measuring the instrument fractionation value of P analysis points in the first pyrrhotite standard sampleR M After the measurement, one analysis point in the pyrite sample is measured again R M ; then Q analysis points in the second sample of pyrrhotite are continuously measured R M After the measurement, one analysis point in the pyrite sample is measured again R M ; finally, X test points in the sample of pyrrhotite are continuously measured R M .

[0021] As a preferred embodiment of the present application, the calculation formula of the measured value in step S3 is as follows:

[0022] (1)

[0023] In formula (1), represents the measured value of the tth point in T points; R M ; represents the measured value of the tth point in T points; i = Py or Pyh , wherein, Py represents pyrite, Pyh represents pyrrhotite.

[0024] As a preferred embodiment of the present application, the calculation formula of the first fractionation value in step S4 is as follows:

[0025] (2)

[0026] In formula (2), represents the average value of the sulfur isotope measured values of N or N+2 analysis points of the pyrite sample, represents the recommended value of the sulfur isotope of the pyrite sample, represents the instrument fractionation value of the pyrite sample; wherein, or .

[0027] As a preferred embodiment of the present application, the formula for calculating the difference value in step S6 is:

[0028] Δ IMF Std,j (4).

[0029] In formula (4), represents the instrument fractionation value of the pth point in P+Q analysis points; j ​Indicates the first fractionation value; Δ IMF Std,j In the P+Q analysis points, the first... j The instrument fractionation difference at each point.

[0030] As a preferred embodiment of the present invention, the formula for calculating the instrument fractionation value of each test point of the pyrrhotite sample in step S9 is as follows:

[0031] (5)

[0032] In equation (5), This indicates the Xth test point in the pyrrhotite sample. d Instrument fractionation values ​​at each point;

[0033] The formula for calculating the recommended value for each test point of the sample is as follows:

[0034] (6)

[0035] In equation (6), This indicates the Xth test point in the pyrrhotite sample. d Recommended value per point, This indicates the Xth test point in the pyrrhotite sample. d Measurement values ​​at each point.

[0036] Secondly, embodiments of the present invention also provide a system for calibrating sulfur isotope measurements of pyrrhotite based on SIMS. The system includes: a SIMS measurement ratio input module, a measurement value calculation module, a first fractionation value calculation module, a second fractionation value calculation module, a difference calculation module, a regression equation construction module, a sample difference calculation module, and a sample recommended value calculation module; wherein...

[0037] The SIMS measurement ratio input module is used to acquire N+2 analysis points in the pyrite standard, P and Q analysis points in each of the two pyrrhotite standards, and X test points in the sample using SIMS measurement. 34 S / 32 S ratio R M ;

[0038] The measurement value calculation module is used to calculate based on R M Calculate the sulfur isotope measurements at all points;

[0039] The first fractionation value calculation module is configured to calculate the average value of the sulfur isotope measurement values of N or N+2 analysis points of the pyrite standard sample, query the recommended value of the sulfur isotope of the pyrite standard sample, and obtain the instrument fractionation value of the pyrite standard sample by subtracting the average value from the recommended value, thereby obtaining the first fractionation value;

[0040] The second fractionation value calculation module is configured to query the recommended values of the first and second magnetite-pyrrhotite standard samples respectively, subtract the sulfur isotope measurement values of each analysis point of the corresponding standard sample from the recommended values respectively, and obtain the instrument fractionation values of each analysis point of the two magnetite-pyrrhotite standard samples, thereby obtaining P+Q second fractionation values;

[0041] The difference value calculation module is configured to calculate the difference values between the P+Q second fractionation values and the first fractionation value, thereby obtaining P+Q Δ IMF Std,j ;

[0042] The regression equation construction module is configured to take Δ IMF Std,j as the dependent variable IMF Std,j / R M,j , take Δ IMF Std,j as the independent variable y , construct a regression equation IMF Std,j / R M,j by linear fitting, and solve the regression coefficients x = y + kx and b ; k b ;

[0043] The sample difference value calculation module is configured to take the instrument fractionation value difference Δ IMF Sam,j of each test point of the magnetite-pyrrhotite sample as the dependent variable y , take Δ IMF Sam,j / R M,j as the independent variable x , and solve the instrument fractionation value difference Δ y kx of each test point of the magnetite-pyrrhotite sample according to the regression equation b = IMF + ;

[0044] IMF The sample recommended value calculation module is configured to solve the instrument fractionation value difference Δ ​Sam,j and the first fractionation value, calculate the instrument fractionation value of each test point; and according to the measured value of the corresponding test point, obtain the recommended value of each test point.

[0045] The technical scheme provided by the embodiment of the present application has the following beneficial effects:

[0046] The method and system for correcting the measurement value of pyrrholite sulfur isotope based on SIMS provided by the embodiment of the present application adopts a combination of multiple standard samples of pyrite and pyrrholite to jointly correct the matrix effect of SIMS sulfur isotope analysis of pyrrholite, can significantly eliminate the matrix effect caused by the crystal structure difference of pyrrholite, effectively reduce the isotope value deviation caused by the matrix effect, and improve the accuracy of the measurement value of the sulfur isotope composition of pyrrholite. In actual measurement, the correction value is different from the recommended value obtained by gas chromatography mass spectrometry by up to 1.13‰ when a single standard sample is used for correction; after correction using the correction method of the present application, the difference between the correction value and the recommended value is reduced to 0.21‰, and the deviation is reduced by about 80%. The present application can be applied to the correction of different pyrrholite sulfur isotope δ 34 S values in celestial samples, magmatic-hydrothermal deposits and other geological bodies, and has a broad application prospect.

[0047] Of course, implementing any product or method of the present application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0049] Figure 1 The method flowchart for correcting the measurement value of pyrrholite sulfur isotope based on SIMS in the embodiment of the present application;

[0050] Figure 2 The sample target schematic diagram of the epoxy resin-based in the specific application example of the present application;

[0051] Figure 3 The correlation between the instrument fractionation value and the 34 S / 32 S ratio of pyrrholite standard samples JC-Po, YP136 and the sample to be measured SY-Po and pyrite standard sample Sonora in the specific application example of the present application;

[0052] Figure 4 The regression equation function graph with ΔIMF as the dependent variable and ΔIMF / R as the independent variable constructed in the specific application example of the present application;

[0053] Figure 5 The results of the matrix effect correction of SY-Po by JC-Po and YP136 respectively and the results of the matrix effect correction of SY-Po by JC-Po and YP136 together are compared in the following table. DETAILED DESCRIPTION

[0054] After discovering the above problems, the present inventors have conducted in-depth research on the existing correction method for SIMS measurement of pyrrhotite sulfur isotope composition. Research has found that the current technology generally uses a single standard sample to correct the measured value of the SIMS measurement of pyrrhotite sulfur isotope composition. However, pyrrhotite has diversity in chemical composition and crystal structure, and it is difficult for a single standard sample to accurately represent or match pyrrhotite samples, thereby making the correction less accurate. The RMs used include: Po-10 (Document 1: Gilbert, S. E., Danyushevsky, L. V., Rodemann, T., Shimizu, N., Gurenko, A., Meffre, S., Thomas, H., Large, R. R., and Death, D., 2014, Optimisation of laser parameters for the analysis of sulphur isotopes in sulphide minerals by laser ablation ICP-MS: Journal of Analytical Atomic Spectrometry, v. 29, no. 6, p. 1042-1051.), JC-Po (Document 2: Chen, L., Liu, Y., Li, Y., Li, Q. L., and Li, X. H., 2021, New potential pyrrhotite and pentlandite reference materials for sulfur and iron isotope microanalysis: Journal of Analytical Atomic Spectrometry, v. 36, no. 7, p. 1431-1440.), YP136 (Document 3: Li, R., Xia, X., Yang, S., Chen, H., and Yang, Q., 2019, Off-Mount Calibration and One New Potential Pyrrhotite Reference Material for Sulfur Isotope Measurement by Secondary Ion Mass Spectrometry: Geostandards and Geoanalytical Research, v. 43, no. 1, p.177-187.) and SY-Po (document 4: Liu, X., Chen, L., Zhao, F., Huang, F., Li, Q., Yu, H., Cui, Z., and Li, X., 2019, A new potential synthetic pyrrhotite reference material for Fe-S isotope microanalysis: Journal of Analytical Atomic Spectrometry, under review.).

[0055] It should be noted that the defects in the above prior art solutions are the result of the inventors' practice and careful study, so the discovery process of the above problems and the solutions proposed by the embodiments of the present application to solve the above problems should be the contribution of the inventors to the present application.

[0056] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. It should be noted that the embodiments and features in the embodiments can be combined with each other without conflict.

[0057] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the description of the present application, the terms "first", "second", "third", "fourth" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0058] After the above in-depth analysis, the embodiments of the present application provide a method and system for correcting pyrrhotite sulfur isotope measurement values based on SIMS, which uses pyrite and pyrrhotite standards to jointly correct the matrix effect caused by the crystal structure of pyrrhotite, and obtains more accurate pyrrhotite sulfur isotope composition. By using the correction method of pyrite+pyrrhotite multi-external standard, the matrix effect caused by the crystal structure difference of pyrrhotite can be significantly eliminated, and the data precision of pyrrhotite sulfur isotope analysis is obviously improved.

[0059] As shown in Figure 1 The method for correcting pyrrhotite sulfur isotope measurement values based on SIMS includes the following steps:

[0060] Step S1: Prepare a SIMS sample target by combining pyrite standard, first pyrrhotite standard, second pyrrhotite standard and the pyrrhotite sample to be tested, all of which have the same particle size.

[0061] In this step, the pyrite sample can be one of the following standards: Sonora, PPP-1, Balmat, Ruttan, etc.; the first and second pyrrhotite standards are selected from one of the following: Po-10, JC-Po, YP136, Anderson, Alexo, etc., and the first and second pyrrhotite standards are different. When preparing the sample target, the substrate can be epoxy resin. The target has the same particle size, preferably 100~150μm.

[0062] Step S2, use SIMS to measure the sample target. 34 S / 32 S ratio R M This includes: first, continuously measuring N analytical points in a pyrite standard sample. R M Then, P analytical points in the first pyrrhotite standard sample were continuously measured. R M After that, test one analytical point in a pyrite standard sample. R M Then, continuously measure Q analytical points in the second pyrrhotite standard sample. R M After that, test one analytical point in a pyrite standard sample. R M Finally, X analytical points in the pyrrhotite sample were continuously measured. R M There are a total of T = N + P + Q + X + 2 points.

[0063] In this step, N analytical points in the pyrite standard are measured continuously. R M To ensure instrument signal stability, when performing continuous point analysis on pyrrhotite standard and pyrrhotite sample respectively, one pyrrhotite standard analysis point is inserted to monitor instrument stability.

[0064] Step S3, according to R M Calculate the sulfur isotope measurements at all points for all standards and samples.

[0065] In this step, the formula for calculating the measured value is as follows:

[0066] (1)

[0067] In equation (1), This represents the t-th point among T points. R M value; This represents the measurement value of the t-th point out of T points; i = Py or Pyh ,in, Py It represents pyrite. Pyh It refers to pyrrhotite.

[0068] Step S4: Calculate the average value of sulfur isotope measurements at N or N+2 analysis points of the pyrite standard sample. At the same time, look up the recommended sulfur isotope values ​​for the pyrite standard sample. Subtract the average value from the recommended value to obtain the instrument fractionation value of the pyrite standard sample, thus obtaining the first fractionation value.

[0069] The specific calculation formula for this step is as follows:

[0070] (2)

[0071] In equation (2), This represents the average sulfur isotope measurements from N or N+2 analysis points of a pyrite standard sample. This indicates the recommended sulfur isotope values ​​for pyrite standards. This represents the instrument fractionation value of the pyrite standard sample; among which, or .

[0072] It should be noted that the first fractionation value has only one value.

[0073] Step S5: Query the recommended values ​​of the first and second pyrrhotite standards respectively, and subtract the sulfur isotope measurement value of each analysis point of the corresponding standard from the recommended value to obtain the instrument fractionation value of each analysis point of the two pyrrhotite standards, thus obtaining P+Q second fractionation values.

[0074] The specific calculation formula for this step is as follows:

[0075] (3)

[0076] In equation (3), This represents the P+Qth analytical point of the pyrrhotite standard. j Measurement values ​​at each point; Indicates the first j The recommended value for each point corresponds to the standard sample; In the P+Q analysis points, the first... j The instrument fractionation values ​​at each point.

[0077] Step S6: Calculate the differences between the P+Q second fractionation values ​​and the first fractionation values ​​to obtain P+Q Δ values. IMFStd,j .

[0078] In this step, the formula for calculating the difference is:

[0079] (4);

[0080] In equation (4), In the P+Q analysis points, the first... j Instrument fractionation values ​​at each point; Indicates the first fractionation value; Δ IMF Std,j In the P+Q analysis points, the first... j The instrument fractionation difference at each point.

[0081] Step S7, according to Δ IMF Std,j Calculate Δ for each corresponding analysis point IMF Std,j / R M,j ; with Δ IMF Std,j Dependent variable y , with Δ IMF Std,j / R M,j as independent variable x A regression equation was constructed using linear fitting. y = kx + b And solve for the regression coefficients k and b .

[0082] Step S8, using the instrument fractionation difference Δ at each test point of the pyrrhotite sample. IMF Sam,d Dependent variable y , with Δ IMF Sam,d / R M,d as independent variable x According to the regression equation y = kx + b The difference Δ between the instrument fractionation values ​​at each test point of the pyrrhotite sample was obtained by solving the problem. IMF Sam,d ; d For the X test points, the first one is the first one. d One point.

[0083] Step S9, based on the difference Δ between the instrument fractionation values ​​at each test point of the pyrrhotite sample... IMF Sam,dCombined with the first fractionation value, calculate the instrument fractionation value for each test point of the sample; then, based on the measured value of the corresponding test point, obtain the recommended value for each test point of the sample.

[0084] In this step, the formula for calculating the instrument fractionation value of each test point of the pyrrhotite sample is as follows:

[0085] (5)

[0086] In equation (5), This indicates the Xth test point in the pyrrhotite sample. d The instrument fractionation values ​​at each point.

[0087] The formula for calculating the recommended value for each test point of the sample is as follows:

[0088] (6)

[0089] In equation (6), This indicates the Xth test point in the pyrrhotite sample. d Recommended value per point, This indicates the Xth test point in the pyrrhotite sample. d Measurement values ​​at each point.

[0090] Based on the same idea, this invention also provides a system for calibrating pyrrhotite sulfur isotope measurements using SIMS. The system includes: a SIMS measurement ratio input module, a measurement value calculation module, a first fractionation value calculation module, a second fractionation value calculation module, a difference calculation module, a regression equation construction module, a sample difference calculation module, and a sample recommended value calculation module; wherein...

[0091] The SIMS measurement ratio input module is used to acquire N+2 analysis points in the pyrite standard, P and Q analysis points in each of the two pyrrhotite standards, and X test points in the sample using SIMS measurement. 34 S / 32 S ratio R M ;

[0092] The measurement value calculation module is used to calculate based on R M Calculate the sulfur isotope measurements at all points;

[0093] The first fractionation value calculation module is used to calculate the average value of sulfur isotope measurements at N or N+2 analysis points of the pyrite standard sample, and at the same time query the recommended sulfur isotope value of the pyrite standard sample. The instrument fractionation value of the pyrite standard sample is obtained by subtracting the average value from the recommended value, thus obtaining the first fractionation value.

[0094] The second fractionation value calculation module is configured to respectively query the recommended values of the first and second magnetite samples, subtract the sulfur isotope measurement values of each analysis point of the corresponding samples from the recommended values, obtain the instrument fractionation values of each analysis point of the two magnetite samples, and obtain P+Q second fractionation values;

[0095] The difference value calculation module is configured to calculate the difference values between the P+Q second fractionation values and the first fractionation values, and obtain P+Q Δ IMF Std,j ;

[0096] The regression equation construction module is configured to take Δ IMF Std,j as the dependent variable IMF Std,j / R M,j , take Δ IMF Std,j as the independent variable y , construct a regression equation IMF Std,j / R M,j using linear fitting, and solve the regression coefficients x y = kx + b ; k b ;

[0097] The sample difference value calculation module is configured to take the instrument fractionation value difference Δ IMF Sam,j of each test point of the magnetite sample as the dependent variable y , take Δ IMF Sam,j / R M,j as the independent variable x , and solve the instrument fractionation value difference Δ y kx = b of each test point of the magnetite sample according to the regression equation IMF Sam,j ;

[0098] The sample recommended value calculation module is configured to calculate the instrument fractionation value of each test point according to the instrument fractionation value difference Δ IMF Sam,j of each test point of the magnetite sample and the first fractionation value, and obtain the recommended value of each test point according to the measurement value of the corresponding test point.

[0099] ​​​The modules in the embodiments are implemented by a processor, and a memory is appropriately increased when storage is needed. The processor can be, but is not limited to, a microprocessor (MPU), a central processing unit (CPU), a network processor (NP), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, and the like. The memory can include a random access memory (RAM) and can also include a non-volatile memory (NVM), such as at least one disk memory. Optionally, the memory can also be at least one storage device located away from the aforementioned processor.

[0100] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be transferred from one website, computer, server or data center to another website, computer, server or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.).

[0101] In addition, it should be noted that the system for correcting pyrrholite sulfur isotope measurement value based on SIMS and the method for correcting pyrrholite sulfur isotope measurement value based on SIMS are corresponding. The description and limitation of the method are also applicable to the system, which will not be described here.

[0102] The method and system for correcting pyrrholite sulfur isotope measurement value based on SIMS are applied to the correction of pyrrholite sulfur isotope composition measurement value. Taking pyrite standard sample Sonora, pyrrholite standard sample JC-Po, YP136 and pyrrholite sample SY-Po as examples, the present application is further described in detail.

[0103] The operation of preparing the sample in step S1 includes:

[0104] Step S101, dip a 10cm*5cm double-sided tape on a 10cm*10cm glass sheet, and stick 7~10 pyrite samples Sonora, each with a particle size of 100~150μm, and 7~10 samples of magnetite JC-Po, YP136 and SY-Po, each with a particle size of 100~150μm, on the double-sided tape in a circle with a diameter of about 1cm;

[0105] Step S102, as shown in the figure, place a polyethylene hollow column (with a diameter of about 25.40mm) with a smooth surface vertically on the double-sided tape, and make sure that the 10mm diameter circle where the samples are stuck is in the center of the polyethylene hollow column. Slowly inject the vacuumized epoxy resin cold inlay (STRUERS EpoFix cold inlay imported from Denmark) along the inner surface of the polyethylene hollow column, vacuumize again and let the mixture solidify to obtain a solidified magnetite sample round target that can be taken out of the polyethylene hollow column; polish the magnetite round target with fine sandpaper and a polishing disc in sequence to make the standard sample and the sample to be measured both exposed on one side of the target; Figure 2

[0106] Step S103, clean the sample target material: first, clean the surface of the sample with deionized water; second, place the sample in a beaker containing alcohol and clean the sample with an ultrasonic instrument for three minutes; third, place the sample in a drying oven and dry it at 50~60℃ for one hour;

[0107] Step S104, plate conductive material: specifically, use a Q150TE model gold plating instrument of Quorum Company to plate a continuous gold film on the exposed side surface of the cleaned round target sample, and the thickness of the plating layer is 20nm~50nm to ensure good electrical conductivity of the sample.

[0108] Step S2, use SIMS to measure the 34 S / 32 S ratio of the sample target R M , and the specific operation steps are as follows:

[0109] Step S201, use Cs + as the primary ion beam, with a voltage of 10kV and an intensity of 2.5nA; use the primary ion beam mode of Gaussian illumination to focus on the sample and excite secondary ions; the scanning area of the secondary ions is 10~20μm;

[0110] Step S202, the negatively charged secondary ions are repelled and accelerated by a voltage of-10kV into a double-focusing magnetic mass spectrometer, which uses a multi-receiving mode and uses Faraday cups to receive 32 S and 34 ​S, with a mass resolution (MRP) set to 2400 to ensure flat-top mass peaks for all signals, and corresponding entrance slit width of 60 μm and energy slit width of 25 eV;

[0111] Before each measurement, the sample surface was pre-etched for about 30 s using a primary ion beam to remove the micro-area surface coating and reduce contamination during target preparation, and then a secondary ion beam was automatically focused for 60 s to reduce analysis errors caused by different sample surface topographies, and energy peaks and mass peaks were scanned in turn to eliminate analysis errors caused by sample charge accumulation and correct the drift of the magnetic field over time; when collecting sulfur isotope signals, each point included 40 measurements, each measurement time was 4 s, and the single-point analysis time for each point was 250 s (including pre-etching for 30 s and secondary ion beam automatic focusing for 60 s).

[0112] The present inventors found through multiple experiments that there is a large difference between the sulfur isotope value of the measured pyrrholite sample obtained by using a pyrrholite external standard for correction and the recommended value. The reason is that pyrrholite has a polytype structure, and the instrument mass fractionation IMF of pyrrholite with different crystal structures is different when SIMS sulfur isotope analysis is performed. The inventors found that the IMF of different pyrrholites and the IMF of pyrite in the same experiment and the correlation between the 34 S / 32 S ratio and the construction of the fitting function found that, as shown in Figure 3 , the difference between the IMF of different pyrrholites and the IMF of pyrite in the same experiment and the IMF of pyrrholite 34 S / 32 S value has a linear correlation, and the linear fitting lines of different pyrrholites are parallel to each other; as shown in Figure 4 , the present application designs a binary scatter plot with different pyrrholites as the horizontal axis, as the vertical axis, and the and of all pyrrholites have a positive correlation. Through this linear relationship, the sulfur isotope of pyrrholite can be accurately corrected. Therefore, when using an ion probe to analyze the sulfur isotope of pyrrholite, at least two pyrrholite external standards and one pyrite external standard are needed to correct the matrix effect in order to obtain accurate sulfur isotope composition.

[0113] Based on the obtained ratio R M , steps S3-S9 are performed. Using the recommended value of Sonora 1.61 ‰, subtracting the average value of 4.71 ‰ of , the instrument fractionation value of Sonora is obtained The value is -3.10‰; by subtracting the measured value of each JC-Po analysis point from the recommended value of 0.06‰ of JC-Po, the value of each point is obtained. Similarly, the values ​​for each analysis point of YP136 can be calculated. ; using JC-Po and YP136 respectively IMF value minus Sonora IMF A value of -3.10‰ yields the values ​​for each analysis point of JC-Po and YP136. IMF Values; based on the set dependent and independent variables, construct a linear regression equation to obtain the regression coefficients. k The value is 0.04365. b The value was 0.04292; further, the regression equation was used to calculate the SY-Po value for each test point of the pyrrhotite sample. Value difference and The values ​​are then used to determine the sulfur isotope values ​​at each test point of SY-Po.

[0114] like Figure 5 As shown, using the correction method of this embodiment, compared with the traditional single-standard-sample correction result, the SY-Po sulfur isotope values ​​all fall within the recommended range (-1.16±0.53‰ (2SD)) using the multi-standard-sample correction method. Simultaneously, the 2SD value of the correction result decreases from 0.40‰ in the traditional single-standard-sample method to 0.19‰, and the data accuracy is significantly improved. With single-standard-sample correction, the difference between the corrected value and the recommended value reaches a maximum of 1.13‰; after correction using the correction method of this invention, the difference between the corrected value and the recommended value decreases to 0.21‰, a reduction of approximately 80%.

[0115] As can be seen from the above technical solutions, the method and system for correcting pyrrhotite sulfur isotope measurements based on SIMS provided in this invention uses a combination of multiple standards of pyrite and pyrrhotite to jointly correct the matrix effect in SIMS sulfur isotope analysis of pyrrhotite. This can significantly eliminate the matrix effect caused by differences in the crystal structure of pyrrhotite, effectively reduce the isotope value deviation caused by the matrix effect, and improve the accuracy of pyrrhotite sulfur isotope composition measurements. In actual measurements, using a single standard for correction, the correction value differed from the recommended value obtained by gas chromatography-mass spectrometry by up to 1.13‰; after correction using the correction method of this invention, the difference between the correction value and the recommended value decreased to 0.21‰, and the deviation was reduced by approximately 80%. This invention can be applied to different pyrrhotite sulfur isotope δ¹⁸ ppm in geological bodies such as astronomical samples and magmatic-hydrothermal deposits. 34 The correction of S-values ​​has broad application prospects. It should be noted that this invention is generally used for SIMS-based correction of matrix effects arising from sulfur isotope analysis of pyrrhotite with different crystal structures.

[0116] The above description is only the preferred embodiment of the present application and the explanation of the technical principles applied, and is not intended to limit the scope of the application claimed, but only represents the preferred embodiment of the present application. Those skilled in the art should understand that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by the combinations of the above technical features or their equivalent features without departing from the inventive concept. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

Claims

1. A method for correcting pyrrholite sulfur isotope measurements based on SIMS, characterized in that, The method comprises the following steps: Step S1, pyrite standard sample, first magnetite standard sample, second magnetite standard sample and to-be-tested magnetite sample with the same particle size are made into an ion probe SIMS sample target; Step S2, SIMS is used to measure N+2 analysis points in the pyrite standard sample, P and Q analysis points in each of the two pyrrhotite standard samples, and X test points in the sample 34 S / 32 S ratio R M ; a total of T=N+P+Q+X+2 points; Step S3, according to R M Calculate the sulfur isotope measurements for all points; Step S4, the average value of the sulfur isotope measurement values of the N or N+2 analysis points of the pyrite standard sample is calculated, the recommended value of the sulfur isotope of the pyrite standard sample is inquired at the same time, the recommended value is subtracted from the average value to obtain the instrument fractionation value of the pyrite standard sample, and a first fractionation value is obtained; Step S5, the recommended values of the first and second magnetite standard samples are inquired respectively, the recommended values are subtracted from the sulfur isotope measurement values of each analysis point of the corresponding standard sample respectively, the instrument fractionation values of each analysis point of the two magnetite standard samples are obtained, and P+Q second fractionation values are obtained; Step S6, calculate the difference between the P+Q second fractional values and the first fractional value, resulting in P+Q delta values IMF Std,j ; Step S7, according to Δ IMF Std,j Calculate Δ IMF Std,j / R M,j ; Δ IMF Std,j as the dependent variable y , Δ IMF Std,j / R M,j as the independent variable x , a regression equation is constructed by linear fitting y = kx + b , and the regression coefficients k and b are solved; Step S8, the difference Δ of the instrument fractionation value of each test point of the sample of pyrrhotite is calculated again IMF Sam,d as the dependent variable y , Δ IMF Sam,d / R M,d as the independent variable x , according to the regression equation y = kx + b the difference Δ of the instrument fractionation value of each test point is solved IMF Sam,d ; Step S9, calculating the instrument fractionation value of each test point of the sample pyrrhotite sample according to the difference Δ of the instrument fractionation values of each test point of the sample IMF Sam,d and the first fractionation value, calculating the instrument fractionation value of each test point of the sample The recommended value of each test point of the sample is obtained according to the measurement value of the corresponding test point.

2. The method of claim 1, wherein, In step S1, the pyrite sample adopts one of the Sonora, PPP-1, Balmat and Ruttan standard samples.

3. The method of claim 1, wherein, In step S1, the first magnetite standard sample and the second magnetite standard sample are selected from one of the Po-10, JC-Po, YP136, Anderson and Alexo, and the first magnetite standard sample and the second magnetite standard sample are different.

4. The method of claim 1, wherein, In step S1, the particle size of the standard sample and the sample is 100-150 μm.

5. The method of claim 1, wherein, The measurement process of step S2 includes: first, continuously measuring the of N analysis points in the pyrite standard sample R M ; then, continuously measuring the of P analysis points in the first pyrrhotite standard sample R M , and after the measurement, measuring the of one analysis point in one pyrite standard sample R M ; then, continuously measuring the of Q analysis points in the second pyrrhotite standard sample R M , and after the measurement, measuring the of one analysis point in one pyrite standard sample R M ; finally, continuously measuring the of X test points in the pyrrhotite sample R M .

6. The method of claim 1, wherein, The calculation formula of the measurement value in step S3 is as follows: (1) In formula (1), denotes the measurement value of the t-th point of the T points; R M value; denotes the measurement value of the t-th point of the T points; i = Py or Pyh wherein, Py represents pyrite, Pyh represents pyrrhotite.

7. The method of claim 1, wherein, The calculation formula of the first fractionation value in step S4 is as follows: (2) In formula (2), represents the average of the sulfur isotope measurements of N or N+2 analysis points of the pyrite standard, represents the recommended value of the sulfur isotope of the pyrite standard, represents the instrumental fractionation value of the pyrite standard; wherein, or .

8. The method of claim 1, wherein, The formula for calculating the difference value in step S6 is: (4)； in formula (4), represents the instrument fraction value of the P+Qth analysis point; j represents the first fraction value; Δ IMF Std,j represents the instrument fraction value of the P+Qth analysis point; j represents the instrument fraction difference value of the P+Qth analysis point.​ 9. The method of claim 1, wherein, The calculation formula of the instrument fractionation value of each test point of the magnetite sample in step S9 is as follows: (5) In formula (5), represents the instrument fractionation value for the Xth test point of the pyrrhotite sample; and d represents the instrument fractionation value for the Xth test point of the pyrrhotite sample; and The formula for calculating the recommended value of each test point of the sample is as follows: (6) In formula (6), represents the recommended value of the i-th point of the pyrrhotite sample X test points, d represents the measured value of the i-th point of the pyrrhotite sample X test points, d represents the measured value of the i-th point of the pyrrhotite sample X test points,​ 10. A system for correcting pyrrholite sulfur isotope measurements based on SIMS, characterized in that, The system comprises a SIMS measurement ratio input module, a measurement value calculation module, a first fractionation value calculation module, a second fractionation value calculation module, a difference value calculation module, a regression equation construction module, a sample difference value calculation module and a sample recommended value calculation module; wherein, The SIMS measurement ratio input module is configured to acquire N+2 analysis points in a pyrite standard sample, P and Q analysis points in each of two magnetite standard samples, and X test points in a sample in a sample target by using SIMS measurement 34 S / 32 S ratio R M ; The measurement value calculation module is configured to calculate the sulfur isotope measurement value of all points according to R M calculating the sulfur isotope measurement value of all points; The first fractionation value calculation module is used for calculating the average value of the sulfur isotope measurement values of the N or N+2 analysis points of the pyrite standard sample, inquiring the recommended value of the sulfur isotope of the pyrite standard sample at the same time, subtracting the recommended value from the average value to obtain the instrument fractionation value of the pyrite standard sample, and obtaining a first fractionation value; The second fractionation value calculation module is used for inquiring the recommended values of the first and second magnetite standard samples respectively, subtracting the recommended values from the sulfur isotope measurement values of each analysis point of the corresponding standard sample respectively, obtaining the instrument fractionation values of each analysis point of the two magnetite standard samples, and obtaining P+Q second fractionation values; The difference calculation module is configured to calculate the difference between the P+Q second fractional values and the first fractional value, to obtain P+Q Δ IMF Std,j ; The regression equation construction module is configured to construct a regression equation according to Δ IMF Std,j Calculate Δ IMF Std,j / R M,j of each corresponding analysis point IMF Std,j with Δ y as the dependent variable IMF Std,j / R M,j and Δ x as the independent variable y = kx + b , and solve the regression coefficients k and b ; The sample difference calculation module is configured to calculate the instrument fractionation value difference Δ of each test point of the pyrrhotite sample IMF Sam,d as the dependent variable y , and Δ IMF Sam,d / R M,d as the independent variable x , according to the regression equation y = kx + b , the instrument fractionation value difference Δ of each test point of the pyrrhotite sample is solved IMF Sam,d ; d as the Xth test point in X test points d ; The sample recommendation value calculation module is configured to calculate the instrument fractionation value of each test point of the sample according to the difference Δ of the instrument fractionation values of each test point of the pyrrhotite sample IMF Sam,d and the first fractionation value, to obtain the instrument fractionation value of each test point of the sample; and to obtain the recommendation value of each test point of the sample according to the measured value of the corresponding test point.

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