A method for determining lead isotope of extraterrestrial sample based on ion probe jump peak method

Abstract

The application discloses an extraterrestrial sample lead isotope determination method based on an ion probe jump peak method, belongs to the technical field of ion probe mass spectrum analysis and planetary sample isotope testing, and solves the problem that an existing determination method is not applicable to extraterrestrial samples and it is difficult to obtain accurate and reliable test data. The extraterrestrial sample lead isotope determination method adopts a single-receiver jump peak mode, combines a beam spot of different mineral scales, a scanning time and a cycle group optimization scheme, reduces the dependence on multi-receiver gain matching and a complex correction process, and reduces additional errors caused by receiver differences and small particle area changes. Through the secondary polishing and repeated screening steps for small particle size target minerals, the minerals with reduced cross-sectional areas are excluded, and false isotope ratio deviation caused by effective bombardment area changes in the jump peak analysis process is avoided. The application realizes the determination of the lead isotope of the extraterrestrial sample, and the test result is accurate and reliable.

Description

Technical Field

[0001] This invention belongs to the field of ion probe mass spectrometry analysis and planetary sample isotope testing technology. Specifically, it relates to a method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method, which is applicable to the ion probe peak-hopping lead isotope analysis of lunar, Martian and small celestial body samples. Background Technology

[0002] With the deepening of research on lunar, asteroid, and future Martian samples, establishing high-precision, high-spatial-resolution, and low-loss analytical and testing methods for extraterrestrial samples has become a key technical issue that urgently needs to be addressed to support my country's lunar exploration program, planetary exploration program, future deep space resource exploration and application, and scientific research on extraterrestrial samples.

[0003] Lead (Pb) isotope analysis is one of the key techniques in planetary sample research. Lead has four stable isotopes. 204 Pb, 206 Pb, 207 Pb and 208 Lead isotope analysis can not only determine the formation age (crystallization age and impact alteration age) of minerals or material components in extraterrestrial samples, but also reveal the source region attributes and evolutionary history of the samples through their isotopic composition characteristics. This provides important evidence for understanding the formation and evolution of parent celestial bodies, crust-mantle differentiation, and changes in their internal reservoirs. Therefore, lead isotope composition has both "dating" and "tracing" significance, and is of great application value in the study of extraterrestrial samples, especially those from the Moon, Mars, and small celestial bodies.

[0004] Existing lead isotope analysis techniques for extraterrestrial samples can be broadly classified into two categories. The first category is solution-based methods, which primarily employ thermal ionization mass spectrometry (TIMS) or multiple receiver inductively coupled plasma mass spectrometry (MC-ICPMS) to perform high-precision isotope determination of lead solutions after separation and purification. While these methods offer high overall accuracy, they typically require the complete dissolution of the sample, resulting in results that represent the average information of the overall or separated phases. This makes it difficult to preserve the original mineral occurrence state, micro-regional structural relationships, and spatial correspondences between different minerals. Therefore, they have significant limitations in studying extraterrestrial samples with complex compositions, small mineral scales, and heterogeneous structures. Furthermore, solution-based methods can almost never simultaneously obtain information on age and initial lead isotope composition. The second category is micro-region in-situ analysis methods, mainly including secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Compared to solution-based methods, micro-area in-situ methods can directly perform lead isotope analysis on specific minerals, glasses, or microfacies while preserving the mineralogical and petrological background. This allows for simultaneous acquisition of age information and initial lead isotope composition information, making it more suitable for extraterrestrial samples with small mineral grain sizes, complex phase assemblages, and multi-stage evolution. However, existing micro-area lead isotope analysis methods still have limitations. For conventional LA-ICP-MS, 204 The accurate determination of Pb has long been subject to the influence of the mass-to-charge ratio. 204 The limitation of Hg interference leads to 204 Pb is difficult to measure accurately, which in turn limits basic lead correction and initial lead composition inversion.

[0005] Compared to other micro-area analysis methods, ion probes offer a combination of high spatial resolution, mass resolution, and detection sensitivity, and can directly obtain... 204 The Pb signal provides an irreplaceable advantage in in-situ micro-area analysis of lead isotopes in extraterrestrial samples. Current technologies for ion probe lead isotope testing mostly employ a multi-receiver static mode, simultaneously receiving Pb signals. 204 Pb, 206 Pb, 207 Pb and 208 To improve analytical accuracy, this method relies heavily on instrument conditions and receiver performance. It typically requires continuous tracking of gain, background values, linear response, and lifetime changes of multiple receivers, and correction for mass fractionation, isotope ratio deviations, and receiver drift using standard samples. Due to the significant differences in the abundance of lead isotopes, receivers, especially electron multipliers, often experience varying loads during long-term use, leading to inconsistent aging and response drift, thus complicating the testing process, data processing, and quality control.

[0006] Compared to the aforementioned multi-receiver static analysis method, peak jumping uses a single receiver to sequentially acquire signals from different elements or isotopes by switching magnetic fields or adjusting the receiver position. The main advantages of this method are that it eliminates the need to address gain matching issues between multiple receivers, reducing additional errors introduced by background differences, response drift, and lifetime inconsistencies among multiple receivers. It also eliminates the need for instrument fractionation, isotope ratio deviation correction, and receiver drift correction using standard samples. Furthermore, this method simplifies instrument setup, analysis procedures, and routine calibration. Existing research indicates that ion probe peak jumping analysis has been used for routine U-Pb system analysis. However, existing ion probe peak jumping analysis methods are primarily designed for larger U-bearing mineral particles in terrestrial or meteorite samples. Their primary ion beam spot size, mass scan sequence, integration time, and data correction procedures all presuppose a large sample cross-section, strong signal, and relatively stable analytical region. However, existing peak-hopping analysis methods cannot be directly applied to lead isotope analysis of extraterrestrial samples. This is because target mineral particles in extraterrestrial samples are typically small and lack U-bearing minerals; simultaneously, the Pb content in silicate phases is extremely low, resulting in weak key signals. Directly employing conventional peak-hopping analysis methods in existing technologies can easily lead to a series of problems, including beam spot size exceeding the target analytical domain, continuous changes in sample cross-section during analysis, insufficient signal intensity, unstable peak identification and background subtraction, and increased mass fractionation correction errors. Consequently, it becomes difficult to obtain accurate and reliable lead isotope determination data.

[0007] In summary, existing ion probe peak-jumping analysis methods are not suitable for the determination of extraterrestrial samples. They cannot solve the technical problems in the analysis of lead isotopes in extraterrestrial samples, such as the lack of small-particle target minerals containing U, low key signals, and easy changes in the analytical domain, which make it difficult to guarantee the accuracy and reliability of the obtained data. Summary of the Invention

[0008] In view of the above analysis, the present invention aims to provide a method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method, in order to solve the technical problems that existing ion probe peak-hopping analysis methods cannot solve in the analysis of lead isotopes in extraterrestrial samples due to the lack of small-particle target minerals containing U minerals, low key signals, and easy changes in the analytical domain, which makes it difficult to guarantee the accuracy and reliability of the obtained data.

[0009] The objective of this invention is achieved as follows: A method for determining lead isotopes in extraterrestrial samples based on ion probe peak-hopping method, comprising: Step S1: The target is made by embedding the sample to be tested and the standard sample together. After the initial polishing, the initial target of the sample to be tested is obtained. Step S2: Conduct conductivity processing and scanning imaging are performed on the target sample to be tested for the first time to identify and calibrate the target minerals in the scanning area; Step S3: Perform secondary polishing on the initial sample target to remove small target minerals with reduced area among those with a particle size ≤10 micrometers, and obtain candidate target minerals; use the candidate target minerals and target minerals with a particle size >10 micrometers as key target minerals; perform secondary identification and calibration on the key target minerals to obtain the relative spatial position information of all key target minerals; Step S4: The primary test sample target is subjected to two stages of fine polishing, cleaning, drying, and coating treatment to obtain the secondary test sample target. Step S5: Based on the relative spatial location information of all key target minerals, select multiple key target minerals located at different positions on the Pb–Pb isochron and with different Pb isotope ratio characteristics as test points; first, configure different ion probe main ion beam spots and beam current conditions according to the particle size of each key target mineral; then, set the peak jumping acquisition time and cycle number differently according to the type of each key target mineral; perform differentiated ion probe peak jumping lead isotope analysis on the secondary test sample target after coating to obtain the lead isotope determination results of the extraterrestrial sample.

[0010] Furthermore, in step S5, different ion probe main ion beam spots and beam current conditions are configured according to the particle size of each key target mineral, including: For target minerals with a particle size of 30 micrometers or larger, an O-type beam with a beam diameter of 30 micrometers and a beam current of 15 nA is used. 2- Main ion beam; For target minerals with a particle size of 10-30 micrometers, an O-type beam with a beam diameter of 15 micrometers and a beam current of 6 nA is used. 2- Main ion beam; For target minerals with a particle size of less than 10 micrometers, an O-type beam with a beam diameter of 5 or 7 micrometers and a beam current of 0.5 nA is used. 2- Main ion beam.

[0011] Furthermore, in step S5, the peak-hopping collection time and the number of cycle groups are set differently according to the type of each key target mineral, including: For zirconium minerals and phosphates, the single scan time for each lead isotope is 5-10 seconds, and the number of cycles is ≥20. For plagioclase, pyroxene, potassium feldspar, potassium glass, and troilite, the single scan time for each lead isotope is 60-120 seconds, with 10 cycles.

[0012] Furthermore, step S5 also includes: Based on the beam size and ion current intensity used for the target mineral, differentiated standard samples were used to correct the peak positions of each lead isotope and control data quality, as follows: For target minerals with a particle size ≤10 micrometers, NIST-610 glass standard samples were used for peak position correction and monitoring; among them, for 204 For the Pb peak center, the peak scanning time is 5 seconds, and the signal reception integration time is 40 seconds; for 206 Pb, 207 Pb and 208 The peak center of Pb was scanned with a peak scanning time of 1 second and the signal receiving integration time was 20 seconds.

[0013] Furthermore, the two-stage fine polishing process in step S4 includes: polishing for 1 minute each with diamond polishing pastes of 0.5 micrometers and 0.25 micrometers in particle size, at a polishing speed of 100 rpm; and / or The cleaning process in step S4 includes: sequentially cleaning the sample target after two-stage fine polishing with analytical grade alcohol, deionized water, and ultrapure water three times under ultrasonic conditions; and / or The drying process in step S4 includes: placing the cleaned sample target in a forced-air drying device for drying for more than 1 hour; and / or In step S4, the coating process uses gold plating to form a continuous conductive layer on the surface of the dried sample target.

[0014] Furthermore, in step S3, based on the change in cross-sectional area of ​​the tiny target minerals with a particle size ≤10 micrometers after secondary polishing, minerals that meet the following rules are identified as candidate target minerals: S2≥90%×S1; Where S1 is the cross-sectional area of ​​the mineral after the first polishing; S2 is the cross-sectional area of ​​the mineral after the second polishing.

[0015] Furthermore, in step S3, when performing secondary polishing on the initial sample target, a diamond polishing paste with a particle size of 0.25 micrometers is used, and the polishing time is 10±3 minutes, so as to remove a thickness of 1±0.1 micrometers from the surface of the sample target.

[0016] Furthermore, step S2 specifically includes: Surface scanning analysis was performed on the initial test sample target after carbon spraying to obtain secondary electron images, backscattered electron images, and energy spectrum surface distribution data. Based on the relative content, symbiotic relationship and spatial distribution characteristics of elements, minerals in the scanning area are identified; and based on the morphological characteristics of different minerals, the differences in backscatter brightness and the combination relationship of multiple elements, the target mineral to be tested is determined. The identified target minerals are recorded using coordinates, numbers, markers, layer overlays, and digital mineral distribution maps. The cross-sectional area of ​​the target minerals is also recorded, and the relative spatial position information of all target minerals on the sample target surface is established.

[0017] Furthermore, in step S2, during the initial surface scanning of the target sample, the spatial resolution of the secondary electron image and the backscattered electron image is better than 0.5 micrometers, the energy spectrum surface scanning resolution is better than 1 micrometer, and the scanning dwell time of a single pixel is greater than 0.2 milliseconds.

[0018] Furthermore, the standard sample selected in step S1 is a glass standard sample, including: the standard sample is a glass standard sample, including NIST610, NIST612, NIST614, BCR-2G, BHVO-2G, NIM-RM2720 and NIM-RM2722.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: a) The lead isotope determination method for extraterrestrial samples based on the ion probe peak-hopping method provided by this invention can realize in-situ micro-area analysis of lead isotopes in different mineral phases of extraterrestrial samples, and can retain the advantages of micro-area in-situ analysis and 204 While maintaining the capability for direct Pb determination, this new approach reduces the reliance of existing multi-receiver static analysis methods on the consistency of multiple receiver states, minimizes the accumulation of errors caused by receiver gain differences, background differences, aging, and response drift, and simplifies instrument adjustment, standard sample calibration, and quality control processes. It is a novel solution for establishing, calibrating, and controlling the quality of lead isotope analysis of extraterrestrial samples.

[0020] (b) The lead isotope determination method for extraterrestrial samples based on ion probe peak-hopping method provided by this invention adopts a single-receiver peak-hopping mode and combines optimized settings for beam spot, scan time, and cycle number for different mineral scales. This reduces the reliance on multi-receiver gain matching and complex calibration procedures, and reduces additional errors caused by receiver differences and variations in the area of ​​small particles. Specifically, by adding secondary polishing and repeated screening steps for small-diameter target minerals, minerals with reduced cross-sectional area can be effectively excluded, avoiding false isotope ratio shifts caused by changes in the effective bombarded area during peak-hopping analysis, thereby improving the accuracy and stability of the analytical results.

[0021] c) The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method provided by this invention establishes a peak position correction and standard sample data quality control process applicable to extraterrestrial samples. It can effectively monitor instrument drift, peak position stability and analytical accuracy, thereby improving the repeatability and reliability of lead isotope test results. It is especially suitable for the analysis of extraterrestrial samples with very small sample quantities, complex mineral assemblage and significant differences in target mineral particle size.

[0022] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this specification 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 recorded in the embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings. Figure 1 This is a schematic diagram of the operation process of the extraterrestrial sample lead isotope determination method based on ion probe peak jumping method provided by the present invention; Figure 2 A comparison of microscopic images of the first and second polishing processes provided for this invention (illustrating the change in the cross-sectional size of the target mineral).

[0024] Figure label: A. Target mineral one; B. Target mineral two. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] To facilitate understanding of the embodiments of this application, further explanation and description will be provided below with reference to the accompanying drawings and specific embodiments. These embodiments do not constitute a limitation on the embodiments of this application. In the drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components.

[0027] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0028] Regarding the English abbreviations and definitions used in this application: SEM stands for Scanning Electron Microscopy; EDS stands for Energy Dispersive X-ray Spectroscopy; BSE stands for Backscattered Electron (Image), which refers to an image obtained in a scanning electron microscope (SEM) based on the elastic scattering effect between a high-energy electron beam and the sample's atomic nuclei, where the signal intensity is positively correlated with the sample's atomic number. SIMS stands for Secondary Ion Mass Spectrometry (Ion Probe).

[0029] Example 1

[0030] A specific embodiment of the present invention discloses a method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method. The operation procedure is described in [reference needed]. Figure 1 The method for determining lead isotopes in extraterrestrial samples includes steps S1 to S5: Step S1: The target is made by embedding the sample to be tested and the standard sample together. After the initial polishing, the initial target of the sample to be tested is obtained.

[0031] S11. Since the extraterrestrial samples are granular and irregular in shape, samples with relatively flat surfaces are selected as extraterrestrial samples to be tested under a stereomicroscope. S12. Select a set of standard samples suitable for ion probe micro-area analysis. Multiple standard samples in the set have different lead contents and different matrix types. After crushing the standard samples, select fragments that are similar in size and flatness of the exposed surface of the sample to be tested. Then, embed the fragments together with the sample to be tested to make a target and perform initial polishing to obtain the initial sample target.

[0032] Preferably, the initial polishing treatment of the embedded sample target includes two stages: progressive grinding and fine polishing. First, the sample target is progressively ground using sandpaper with grit sizes of 200 mesh, 800 mesh, 2000 mesh, 3000 mesh, 5000 mesh, and 7000 mesh, with a polishing disc rotation speed of 120 rpm and a grinding time of 2 minutes for each stage. Then, the sample target after progressive grinding is finely polished using diamond polishing paste with a particle size of 0.5 micrometers for 20 minutes at a polishing disc rotation speed of 200 rpm. Through this progressive grinding and fine polishing process, the surface roughness of the sample target can be gradually reduced, obtaining a smooth exposed surface that meets the requirements of ion probe micro-area analysis.

[0033] Preferably, the standard samples are glass standard samples, including NIST610, NIST612, NIST614, BCR-2G, BHVO-2G, NIM-RM2720, and NIM-RM2722. Among them, NIST610, NIST612, and NIST614 are glass trace element standard materials provided by the National Institute of Standards and Technology (NIST) of the United States; BCR-2G and BHVO-2G are micro-area analysis glass reference materials provided by the United States Geological Survey (USGS); and NIM-RM2720 and NIM-RM2722 are silicate rock glass slide standard materials launched by the National Institute of Metrology of China.

[0034] By keeping the standard sample and the sample to be tested similar in geometry and surface condition, the surface undulations caused by differences in sample height and polishing rate during subsequent polishing can be reduced. By configuring a variety of standard samples with different lead contents and different matrix types, the adaptability to different types of extraterrestrial samples can be improved, and conditions can be provided for subsequent instrument status monitoring and analysis method establishment.

[0035] Step S2: Conduct conductivity processing and scanning imaging are performed on the initial test sample target in sequence to obtain secondary electron image, backscattered electron image and energy spectrum distribution data; based on the secondary electron image, backscattered electron image and energy spectrum distribution data, the target mineral to be tested in the scanning area is identified, and the spatial position of the target mineral to be tested is calibrated to obtain the relative spatial position information A of all target minerals to be tested on the surface of the initial test sample target.

[0036] Step S21: Perform conductivity processing and scanning imaging on the initial test sample target sequentially to obtain secondary electron images, backscattered electron images, and energy spectrum distribution data, specifically including steps S211-S212: S211. Conduct the initial test sample target obtained in step S1 with conductive treatment, preferably by carbon spraying, to improve the conductivity of the sample surface and meet the requirements of subsequent scanning electron microscopy observation and energy dispersive spectroscopy analysis.

[0037] S212. After carbon spraying, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) is used to perform surface scanning analysis on the initial test sample target after carbon spraying. At the same time, secondary electron images, backscattered electron images and energy spectrum surface distribution data (elemental surface distribution map) are acquired, thereby obtaining the relative content, co-occurrence relationship and spatial distribution characteristics of elements.

[0038] During the initial surface scanning of the target sample, the spatial resolution of the secondary electron image and the backscattered electron image is better than 0.5 micrometers, the energy spectrum surface scanning resolution is better than 1 micrometer, and the scanning dwell time of a single pixel is greater than 0.2 milliseconds.

[0039] Scanning electron microscopy can simultaneously obtain sample surface morphology information, atomic number contrast information, and elemental distribution information. EDS surface distribution analysis can achieve multi-element identification and spatial distribution characterization within a selected area. Pixel resolution and dwell time can be set according to analytical requirements.

[0040] Step S22: Based on the secondary electron image, backscattered electron image, and energy dispersive spectral distribution data obtained in step S21, identify the target minerals within the scanning area and calibrate their spatial positions to obtain the relative spatial position information A of all target minerals on the initial sample target surface. In other words, based on the scanning electron microscope secondary electron image, backscattered electron image, and energy dispersive spectral distribution data obtained in step S21, identify, screen, and calibrate the material phases within the sample scanning area. These material phases include target minerals with a particle size less than 10 μm and large-particle-size target minerals with a particle size greater than 10 μm. Step S22 includes steps S221-S222: Step S221: Based on the relative content, symbiotic relationship and spatial distribution characteristics of the elements obtained in step S21, identify the minerals in the scanning area; and based on the morphological characteristics, backscatter brightness differences and combination relationships of various elements of different minerals, determine the target minerals suitable for lead isotope analysis.

[0041] When identifying minerals within a scanning area, the extracted and analyzed elements preferably include one or more of oxygen, silicon, aluminum, iron, calcium, magnesium, potassium, sodium, phosphorus, sulfur, and zirconium. It is preferable to extract all of these elements simultaneously to comprehensively distinguish different minerals in the sample based on their relative abundance, symbiotic relationships, and spatial distribution characteristics. SEM / EDS can be used to acquire morphological and elemental composition information of particles and minerals at submicron to micron spatial resolution, making it suitable for geological materials and mineral identification. Specifically, secondary electron imaging characterizes the sample surface morphology and microstructure, while backscattered electron imaging characterizes the average atomic number differences between different minerals. Combined with EDS elemental surface distribution maps, this allows for the screening and precise location of lead isotope analysis targets. BSE and EDS are used in combination for mineral identification and phase composition discrimination.

[0042] In a preferred embodiment, the target minerals whose relative spatial positions are identified and calibrated include one or more of pyroxene, feldspar, potassium-rich glass, troilite, phosphates, and zirconium minerals. Based on the morphological characteristics, backscattering brightness differences, and the combination relationships of elements such as oxygen, silicon, aluminum, iron, calcium, magnesium, potassium, sodium, phosphorus, sulfur, and zirconium (i.e., the elemental composition and content in the corresponding minerals), target minerals suitable for lead isotope analysis are determined, and fractures, pores, edge fracture zones, miscible zones, or other unsuitable locations for testing are excluded.

[0043] Step S222: Record the identified target minerals using coordinates, numbers, markers, layer overlays (including various overlay methods such as microscopic morphology images, elemental images, phase distribution images, and crystal structure distribution images), and digital mineral distribution maps. It is also important to record the cross-sectional area of ​​the target minerals. Establish the relative spatial position information of all target minerals on the sample target surface for target navigation, analysis point layout, and result backtracking during subsequent ion probe testing.

[0044] By pre-identifying and calibrating the location of the target mineral, a basis for target screening and precise positioning can be provided for subsequent ion probe lead isotope analysis, thereby improving testing efficiency and reducing the risk of false testing of non-target minerals.

[0045] Step S3: Perform secondary polishing on the initial sample target after the identification and spatial positioning of the target minerals to be tested are completed, so as to achieve secondary polishing of micro-target minerals with a particle size ≤10 micrometers. Based on the change in cross-sectional area of ​​the micro-target minerals after secondary polishing, candidate target minerals are screened. Specifically, micro-target minerals with a reduced cross-sectional area after secondary polishing (i.e., micro-target minerals with a reduction in cross-sectional area exceeding the threshold range) are eliminated. Minerals with a basically unchanged or increased cross-sectional area after secondary polishing are used as candidate target minerals. The candidate target minerals and target minerals with a particle size greater than or greater than 10 micrometers are used together as the objects of subsequent ion probe peak jumping lead isotope analysis (i.e., key target minerals). Secondary identification and spatial positioning of key target minerals are performed to obtain the relative spatial position information B of all key target minerals on the surface of the initial sample target.

[0046] Large-particle-size target minerals with a particle size >10 μm identified in step S2 can be directly used as the target for subsequent ion probe peak-hopping lead isotope analysis; however, target minerals with a particle size ≤10 μm require further screening.

[0047] For target minerals with a particle size ≤10 micrometers (i.e., micro-target minerals) identified in step S2, phosphates, zirconium minerals, and potassium feldspar are preferred. Since these minerals often appear as embedded particles with a certain three-dimensional morphology in the sample target, it is difficult to determine their cross-sectional change trend in the direction of further analysis depth based solely on the surface morphology and cross-sectional size exposed after one polishing. If the exposed area of ​​the target mineral decreases after further surface removal, when its actual bombarded area is smaller than the ion beam spot area, the main ion beam will not be able to fully act on the target mineral, resulting in a decrease in signal count during the analysis. Furthermore, since different isotope signals are not received synchronously at the same time in the peak-hopping mode, if the effective bombarded area of ​​the target mineral continues to change during the analysis, it may cause non-uniform attenuation of different isotope signals over time, thereby causing false isotope ratio changes introduced by the analysis process.

[0048] To avoid the aforementioned problems, this embodiment performs a secondary polishing treatment on micro-target minerals with a particle size ≤10 micrometers before the formal ion probe test. Preferably, a diamond polishing paste with a particle size of 0.25 micrometers is used to further polish the sample target to be tested initially, and the polishing time is preferably 10±3 minutes, so as to further remove 1±0.1 micrometers of thickness from the sample surface. After the secondary polishing is completed, the same secondary electron imaging, backscattered electron imaging, and energy dispersive spectroscopy (EDS) scanning process as in step S2 is used again to perform conductivity treatment and scanning imaging to identify the target minerals to be tested, with a focus on comparing and analyzing the cross-sectional area of ​​the micro-target minerals. By comparing the changes in the exposed cross-sectional area of ​​the same micro-target mineral before and after the secondary polishing, micro-target minerals with a particle size of less than 10 micrometers are classified into three types: those with reduced area, those with essentially unchanged area, and those with increased area. Among them, small target minerals whose cross-sectional area decreases after secondary polishing are preferably excluded and not used as candidate target minerals for subsequent analysis point layout, that is, not used as objects for subsequent ion probe peak jumping lead isotope analysis; small target minerals whose cross-sectional area remains basically unchanged or increases after secondary polishing are preferably retained and used as candidate target minerals for subsequent analysis point layout.

[0049] See Figure 2 , Figure 2The diagram shows the changes in the cross-sectional size of the target minerals during the initial and secondary polishing processes. Target mineral A, whose cross-sectional area remains essentially unchanged, is retained, while target mineral B, whose cross-sectional area decreases, is discarded. Candidate target minerals, along with target minerals larger than 10 μm, are used for subsequent ion probe peak-hopping lead isotope analysis and can be termed "key target minerals." Following the above rules, unsuitable target minerals are removed from the relative spatial position information A of all target minerals, thus obtaining the relative spatial position information B of all key target minerals on the sample target surface after removal. The relative spatial position information B of all key target minerals includes the spatial position information of target minerals with a particle size greater than 10 μm, as well as the spatial position information of small target minerals whose cross-sectional area remains essentially unchanged or increases after the secondary polishing.

[0050] In this embodiment, "area reduction type" refers to a decrease in the cross-sectional area of ​​the mineral after two polishing processes exceeding 10%; "area essentially unchanged type" refers to a decrease or increase in the cross-sectional area of ​​the mineral after two polishing processes not exceeding 10%; and "area increase type" refers to an increase in the cross-sectional area of ​​the mineral after two polishing processes exceeding 10%. Therefore, in this embodiment, the cross-sectional area of ​​the mineral after the first polishing is S1, and the cross-sectional area of ​​the mineral after the second polishing is S2. Minerals that meet the following rules are identified as candidate target minerals: S2≥90%×S1; Where S1 is the cross-sectional area of ​​the mineral after the first polishing; S2 is the cross-sectional area of ​​the mineral after the second polishing.

[0051] By adding this step, based on the change in the cross-sectional area of ​​the small target minerals before and after secondary polishing, small target minerals that show a shrinking trend in the direction of analysis depth can be effectively removed. This avoids signal instability and false isotope ratio changes caused by the target cross-sectional area being smaller than the ion beam spot or by the bombardment area changing over time during the analysis process. As a result, the authenticity, stability and repeatability of the ion probe peak-jumping lead isotope analysis results can be improved.

[0052] Step S4: The initial test sample target, after completing the secondary identification and calibration of key target minerals, is subjected to two stages of fine polishing, cleaning, drying, and coating treatment to obtain the secondary test sample target.

[0053] Step S41: Perform two-stage fine polishing on the surface of the initial sample target after the secondary identification and calibration of key target minerals in step S3 to remove the conductive carbon layer formed by the previous carbon spraying and surface contaminants.

[0054] Specifically, diamond polishing paste is used to polish the sample target surface after secondary identification and calibration of key target minerals to remove the conductive carbon layer formed by previous carbon spraying and surface contaminants. Further, it is preferable to first polish with diamond polishing paste with a particle size of 0.5 micrometers for 1 minute, and then continue polishing with diamond polishing paste with a particle size of 0.25 micrometers for another minute. The preferred polishing speed is 100 rpm. These steps differ from traditional polishing processes, primarily to remove the carbon film on the sample surface while effectively maintaining the cross-sectional area of ​​the target mineral. Secondary ion mass spectrometry (SIMS) sample preparation typically requires a smooth, well-polished sample target surface, which must be cleaned before analysis.

[0055] Step S42: Clean the initial test sample target after two-stage fine polishing.

[0056] Specifically, since extraterrestrial samples typically contain numerous fissures and have small minerals with large grain boundaries due to their formation, it is necessary to clean the two-stage finely polished sample target sequentially with analytical grade alcohol, deionized water, and ultrapure water after polishing. Preferably, each cleaning step is performed under ultrasonic conditions, with each ultrasonic treatment lasting 10 minutes, in order to remove residual polishing paste particles, fine dust, and contaminants adhering to the surface, pores, fissures, and phase boundaries.

[0057] Step S43: After cleaning, dry the sample target. Place the cleaned sample target in a forced-air drying device for drying, preferably for more than 1 hour, to remove residual moisture from the surface and pores of the sample target after cleaning, thereby improving vacuum compatibility and surface stability during subsequent vacuum coating and ion probe analysis. Ion probe analysis typically requires good vacuum conditions and that the surface be kept clean and dry before analysis.

[0058] Step S44: Perform conductive coating treatment on the primary test sample target after cleaning and drying to obtain a coated secondary test sample target.

[0059] The initial sample target, after being cleaned and dried in step S43, is placed into the coating equipment for conductive coating treatment. Gold plating is preferred, forming a continuous conductive layer on the surface of the initial sample target after two stages of fine polishing, cleaning, and drying. This improves the surface conductivity of the sample, reduces charge accumulation during testing, and enhances the stability of subsequent ion probe analysis. Simultaneously, a conductive reference material is processed using the same cleaning procedure as the initial sample target in step S42. The conductive reference material is preferably 99.99% pure gold. The cleaned conductive reference material is also placed into the coating equipment to assist in monitoring the coating status or as an object for checking the conductivity.

[0060] Before secondary ion mass spectrometry (SIMS) sample analysis, samples typically require gold plating to improve conductivity. To balance conductivity with the requirements of micro-area analysis, this embodiment preferably uses a nanoscale gold plating layer instead of a micrometer-thick plating layer. In one preferred embodiment, the gold plating layer is a thin conductive layer with a thickness of 30 nm.

[0061] Step S5: Based on the relative spatial location information B of all key target minerals on the secondary test sample target, select multiple key target minerals located at different positions on the Pb–Pb isochron and with different Pb isotope ratio characteristics as test points; first, configure different ion probe main ion beam spots and beam current conditions according to the particle size of each key target mineral; then, set the peak jumping acquisition time and cycle number differently according to the type of each key target mineral; perform differentiated ion probe peak jumping lead isotope analysis on the coated secondary test sample target, construct isochrones and obtain the age information and initial lead isotope composition of the test sample, and obtain the lead isotope determination results of the extraterrestrial sample.

[0062] In other words, this step selects multiple key target minerals with different Pb isotope ratios at different locations on the Pb–Pb isochrones as test points, based on the relative spatial location information B of all key target minerals. According to the particle size (corresponding to the effective exposure cross-section), Pb signal intensity, and distribution position of each key target mineral on the Pb–Pb isochrones, the beam spot size, beam current intensity, lead isotope single scan time, and number of cycles of the ion probe's primary ion beam are set respectively. Specifically, for target minerals with a small effective exposure cross-section and a strong Pb signal, a small beam spot, a shorter lead isotope single scan time, and a larger number of cycles are used for peak-hopping analysis. For target minerals with a large effective exposure cross-section but a weak Pb signal, a larger beam spot, a longer lead isotope single scan time, and a smaller number of cycles are used for peak-hopping analysis. Thus, differentiated ion probe peak-hopping lead isotope analysis is performed on the secondary test sample target after coating, obtaining the lead isotope determination results of the extraterrestrial sample.

[0063] Step S51: Selection of target for ion probe peak-hopping lead isotope analysis and configuration of beam parameters, as detailed below: In this invention, the target mineral for ion probe peak-hopping lead isotope analysis is not limited to a single mineral, but rather preferably multiple phases with different Pb isotope ratios located at different positions on the Pb–Pb isochrones to construct isochrones and obtain age information and initial lead isotope composition of the sample. Specifically, for analysis points in the lower part of the isochrones or where radiogenic lead is dominant, mineral phases rich in U and low in common lead or almost entirely containing radiogenic lead are preferred, mainly including zirconium minerals and phosphates; for analysis points in the upper part of the isochrones or where common lead is dominant, mineral phases with extremely low U content and predominantly initial lead are preferred, mainly including plagioclase, potassium feldspar, and troilite; for intermediate analysis points between these two, mineral phases containing both a certain amount of U and Pb are preferred, mainly including potassium glass, pyroxene, and some phosphates. By combining the above-mentioned analysis points located at different positions on the isochrones, the accuracy of isochrone fitting can be improved, and a data foundation can be provided for age and initial lead isotope composition inversion.

[0064] Furthermore, due to the significant differences in grain size, lead content, uranium content, and occurrence state of different mineral phases in extraterrestrial samples, this embodiment configures different ion probe main ion beam spots and beam current conditions for different analyte minerals to balance spatial resolution, signal intensity, and test stability. In-situ ion probe analysis offers micrometer-level spatial resolution, which can be achieved by adjusting the O... 2- The main ion beam intensity and beam spot size are adapted to mineral phases with different particle sizes and contents; in a preferred embodiment, In this embodiment, target minerals are classified into large-size target minerals and small-size target minerals based on their particle size. Specifically, target minerals with a particle size of less than 10 μm are defined as small-size target minerals, while those with a particle size greater than 10 μm are collectively referred to as large-size target minerals. Among them, large-size target minerals include two particle size grades: relatively large and medium-sized.

[0065] For rock-forming minerals with relatively large grain sizes (above 30 micrometers) but low lead content, such as plagioclase and pyroxene, a larger beam size is preferred to increase the lead signal intensity. Specifically, an O2 beam with a beam diameter of approximately 30 micrometers and a beam current of approximately 15 nA can be used. 2- The main ion beam is used for continuous analysis of the sample. For medium-sized (10-30 μm) potassium feldspar, potassium glass, and troilite, which are typically poorly distributed, an O2 beam with a beam spot diameter of approximately 15 μm and a beam current of approximately 6 nA is preferred. 2- Main ion beam.

[0066] For zirconium minerals and phosphates with small particle sizes (below 10 micrometers) but often enriched in U or with high Pb / U ratios, a smaller beam spot is preferred to ensure spatial resolution. Specifically, an O beam spot diameter of approximately 5 or 7 micrometers and a beam current of approximately 0.5 nA can be used. 2- Main ion beam.

[0067] By classifying and selecting different mineral phases and configuring differentiated beams, the in-situ lead isotope analysis needs of large-particle low-Pb rock-forming minerals, medium-scale Pb-b-bearing glasses or sulfides, and fine-grained U-rich dating minerals can be met on the same sample target. This provides the basic conditions for subsequent lead isotope acquisition, isochron construction, and age-initial lead joint inversion under peak-jumping mode.

[0068] Step S52: When performing ion probe peak-hopping lead isotope analysis, the peak-hopping acquisition time and number of cycles are set according to the differences in the types of key target minerals.

[0069] In this embodiment, the lead isotope analysis parameters for ion probe peak jumping of different minerals are preferably differentiated based on the grain size, occurrence state, and U and Pb content characteristics of the key target minerals. Generally, the analyte minerals can be divided into two categories: small-particle-size target minerals and large-particle-size target minerals. For secondary ion mass spectrometry, if the ion beam uses Kohler focusing mode (uniform ion beam energy density, corresponding to Gaussian focusing mode with high energy density at the center and low at the edges), the ion beam size is adjusted using micropores. Therefore, the adjusted ion beam diameter is typically 5 or 7 micrometers, 15 micrometers, and 30 micrometers. In this embodiment, different single isotope scanning times and cycle numbers are configured for small-particle-size target minerals and large-particle-size target minerals, respectively, in order to reduce testing errors and improve the reliability of isotope ratio results.

[0070] For small-particle-size target minerals (≤10 micrometers), including zirconium minerals and phosphates, due to their typically small particle size, only small-spot in-situ analysis can be performed. These minerals typically have U and Pb contents several orders of magnitude higher than rock-forming minerals, providing strong ion signals; however, their exposure cross-section may still change with sputtering depth during analysis. Since the lead isotope signals are received sequentially rather than synchronously in the peak-hopping mode, if the residence time of a single isotope is too long, changes in target area are more likely to be converted into false signal differences between different isotopes, thus affecting the isotope ratio. Therefore, in this step, for small-particle-size target minerals, such as zirconium minerals and phosphates, it is preferable to shorten the individual isotope scan time for the four lead isotopes, making the acquisition times of adjacent isotope signals as close as possible. Specifically, the single scan time for each lead isotope is preferably 5-10 seconds, more preferably no more than 10 seconds; simultaneously, to ensure total count and statistical accuracy, the number of cycles can be increased accordingly, preferably to 20 or more cycles. By shortening the single scan time and increasing the number of cycles, the systematic bias caused by the change of the target cross section over time can be reduced, thereby improving the stability of the peak jumping analysis results for small-particle-size minerals.

[0071] For large-particle-size target minerals (greater than 10 micrometers), including rock-forming minerals such as plagioclase and pyroxene, as well as accessory minerals such as potassium feldspar, potassium glass, and troilite, these minerals typically have large particles and can be analyzed using larger beam sizes. For example, for relatively large-particle-size target minerals (greater than 30 micrometers), such as plagioclase and pyroxene, beam sizes greater than or equal to 30 micrometers are preferred; for medium-particle-size target minerals (10–30 micrometers), such as potassium feldspar, potassium glass, and troilite, beam diameters of approximately 15 micrometers are preferred. Since their effective bombardment area changes little during analysis, there is generally no need to focus on pseudo-isotope ratio shifts caused by cross-sectional changes. Conversely, these minerals typically have low lead content and weak signals, requiring extended scan times for individual isotopes to improve effective counts and reduce the influence of background signals on the results. Therefore, for large-particle-size target minerals, it is preferable to set the single scan time for each lead isotope to 60–120 seconds, and the number of cycles can be appropriately reduced, preferably to 10 cycles. By extending the time of a single acquisition and reducing the number of cycles, the signal-to-noise ratio and analytical accuracy of large-particle minerals with low lead content can be improved while ensuring a reasonable total acquisition time.

[0072] By setting the parameters described above, the matching relationship between single scan time and number of cycles in peak-jumping analysis can be optimized for different mineral scales and signal characteristics. On the one hand, for small-diameter minerals, it can effectively suppress false isotope ratio shifts caused by changes in target area and asynchronous peak-jumping reception; on the other hand, for large-diameter low-lead minerals, it can effectively improve the counting statistics quality and reduce background influence, thereby enhancing the applicability and data reliability of the entire extraterrestrial sample ion probe peak-jumping lead isotope analysis method.

[0073] Step S53: Based on the beam size and ion current intensity of the target mineral to be tested, use differentiated standard samples to correct the peak positions of each lead isotope and control the data quality.

[0074] To ensure accurate reception of lead isotope signals during ion probe peak-hopping lead isotope analysis, the peak positions of each lead isotope need to be corrected and monitored using standard samples to prevent signal reception errors or misreception of interference peaks due to peak position drift. The data quality control process employs different standard sample selection and peak position correction strategies depending on the beam size and ion current intensity used for the target mineral.

[0075] For target minerals with a particle size greater than 10 μm and an effective exposed surface capable of accommodating the ion beam spot, a single ion beam spot of 15–30 μm can be used for analysis, depending on the actual size of the target mineral. Since the effective analytical area for this type of target mineral is relatively large, the cross-sectional changes caused by sputtering during analysis are less affected; therefore, a conventional peak-jumping test procedure can be used for lead isotope analysis.

[0076] Preferably, for this type of target mineral, standard samples with relatively low elemental content, such as BHVO-2G, and suitable for ion probe micro-area analysis can be selected as reference samples for testing conditions or quality control samples; during peak jumping analysis, 204 The Pb peak center scan time is set to 2 seconds. 206 Pb, 207 Pb and 208 The Pb peak center scan time is set to 0.5 seconds, and the signal reception integration time is preferably 10 seconds to ensure test accuracy and analysis efficiency.

[0077] This embodiment focuses on optimizing speckle analysis conditions for target minerals ≤10 micrometers. Specifically, for small speckle analysis conditions, it is preferred for small-particle-size target minerals such as zirconium minerals and phosphates.

[0078] Because the secondary ion signal generated under small spot conditions (5-7 micrometers) is weak, in order to ensure the quality of each lead isotope, especially the one with the lowest abundance... 204 The Pb peak center can be accurately identified, and it is preferable to use standard samples with high lead content for peak position correction and monitoring, such as the NIST-610 glass standard sample. For peaks with lower intensity and susceptible to noise and neighboring interference... 204 For the Pb peak center, a longer peak scanning time is preferred, more preferably 5 seconds, to improve the stability of peak center positioning. The signal reception integration time is preferably 40 seconds to ensure test accuracy. 206 Pb, 207 Pb and 208 At the center of the Pb peak, due to the strong signal, a shorter peak scanning time is preferred, more preferably 1 second, and the signal receiving integration time is preferably 20 seconds to ensure test accuracy.

[0079] By employing the aforementioned differentiated peak position correction methods, the overall peak position monitoring efficiency can be improved while ensuring the accuracy of identifying low-abundance isotope peak centers. For large-spot analysis conditions, it is preferred to use large-grained rock-forming minerals such as plagioclase and pyroxene. Since the ion current intensity under large-spot conditions is usually significantly higher than under small-spot conditions, reaching several to tens of times the latter, it is preferable to use standard samples with moderate lead content for peak position correction, such as BCR glass standards or NIST-612 glass standards, to avoid unnecessary load on the electron multiplier due to excessively high ion currents and to reduce its lifespan. For large-spot analysis, the peak positions of each lead isotope are also corrected and their stability monitored using standard samples.

[0080] For the sample itself, this embodiment preferably does not perform individual lead isotope peak center correction for each test point. This is because the lead content varies significantly among different mineral phases in extraterrestrial samples, and the actual lead signal intensity of the test sample is usually difficult to predict accurately before analysis. If peak-by-peak center correction is directly performed on low-content samples, the peak position is easily affected by background noise or interference peaks under weak signal conditions, which may lead to the peak center positioning deviating from the true signal position. Therefore, this embodiment adopts a strategy of "correcting peak positions with standard samples and performing peak-skipping analysis directly on the corrected samples" to improve the robustness and consistency of the overall test. Furthermore, to monitor the stability of the instrument's peak position and response status during the analysis process, it is preferable to insert standard samples at fixed intervals for data quality control. Preferably, after analyzing every 3 test sample points, one standard sample point is inserted for peak position correction and stability monitoring; after analyzing every 6 test sample points, one external standard sample point is inserted to verify the accuracy and external consistency of the analysis results. By setting the above-mentioned interpolation frequency, the instrument's operating status, peak drift, and analytical accuracy can be continuously monitored while ensuring testing efficiency, thereby improving the data quality and reliability of the entire peak-jumping lead isotope analysis method.

[0081] Comparative Example The method of this invention and traditional techniques for testing lead isotopes in small-particle-size target minerals 206 Pb, 207 Pb and 206 Pb / 207 The ratio of Pb, the test results are shown in Table 1: Table 1

[0082] As can be seen from the test results in Table 1, traditional techniques were used to test the lead isotopes of small-particle-size target minerals. 206 Pb, 207 Pb and 206 Pb / 207 The Pb ratio varied greatly across the six data sets analyzed over time, severely impacting the quality of the data output. However, the Pb ratio obtained using the method of this invention... 206 Pb, 207 Pb and 206 Pb / 207 Smaller changes in Pb allow for higher precision and accuracy results. It should be noted that Pb is not listed in Table 1. 204 Pb, mainly due to the presence of Pb in lunar samples. 204 Pb content is usually low, compared to 206 There is a difference of several orders of magnitude between Pb and Pb.

[0083] Compared with existing technologies, the lead isotope determination method for extraterrestrial samples based on the ion probe peak-hopping method provided in this embodiment can achieve at least one of the following beneficial effects: (1) This invention enables in-situ analysis of lead isotope micro-regions in different mineral phases of extraterrestrial samples, preserving mineralogical characteristics and spatial occurrence relationships while simultaneously acquiring age information and initial lead isotope composition information. This overcomes the problem of traditional solution methods failing to preserve mineral phase and micro-region structural information. Moreover, this invention is more suitable for the analysis of extraterrestrial samples with extremely small sample volumes, complex mineral assemblages, and significant differences in target mineral grain size.

[0084] (2) This invention employs a single-receiver peak-hopping mode, combined with optimized settings for beam spot size, scan time, and number of cycles for different mineral scales. This reduces the reliance on multi-receiver gain matching and complex correction procedures, and minimizes additional errors caused by receiver differences and variations in the area of ​​small particles. Specifically, by adding secondary polishing and repeated screening steps for small-diameter target minerals, minerals with reduced cross-sectional area can be effectively excluded, avoiding false isotope ratio shifts caused by changes in the effective bombarded area during peak-hopping analysis, thereby improving the accuracy and stability of the analysis results.

[0085] (3) This invention establishes a peak position correction and standard sample data quality control process applicable to extraterrestrial samples, which can effectively monitor instrument drift, peak position stability and analytical accuracy, thereby improving the repeatability and reliability of lead isotope test results, and forming a systematic analysis method with strong implementability and promotion value.

[0086] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for determining lead isotopes in extraterrestrial samples based on ion probe peak-hopping method, characterized in that, include: Step S1: The target is made by embedding the sample to be tested and the standard sample together. After the initial polishing, the initial target of the sample to be tested is obtained. Step S2: Conduct conductivity processing and scanning imaging are performed on the target sample to be tested for the first time to identify and calibrate the target minerals in the scanning area; Step S3: Perform secondary polishing on the initial sample target to remove the area-reduced micro-target minerals among the micro-target minerals with a particle size ≤10 micrometers, and obtain candidate target minerals; take the candidate target minerals and target minerals with a particle size >10 micrometers as key target minerals; perform secondary identification and calibration on the key target minerals to obtain the relative spatial position information of all key target minerals; Step S4: The primary test sample target is subjected to two stages of fine polishing, cleaning, drying, and coating treatment to obtain the secondary test sample target. Step S5: Based on the relative spatial location information of all key target minerals, select multiple key target minerals located at different positions on the Pb–Pb isochron and with different Pb isotope ratio characteristics as test points; first, configure different ion probe main ion beam spots and beam current conditions according to the particle size of each key target mineral; then, set the peak jumping acquisition time and cycle number differently according to the type of each key target mineral; perform differentiated ion probe peak jumping lead isotope analysis on the secondary test sample target after coating to obtain the lead isotope determination results of the extraterrestrial sample.

2. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, In step S5, different ion probe main ion beam spots and beam current conditions are configured according to the particle size of each key target mineral, including: For target minerals with a particle size of 30 micrometers or larger, an O-type beam with a beam diameter of 30 micrometers and a beam current of 15 nA is used. 2- Main ion beam; For target minerals with a particle size of 10-30 micrometers, an O-type beam with a beam diameter of 15 micrometers and a beam current of 6 nA is used. 2- Main ion beam; For target minerals with a particle size of less than 10 micrometers, an O-type beam with a beam diameter of 5 or 7 micrometers and a beam current of 0.5 nA is used. 2- Main ion beam.

3. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 2, characterized in that, In step S5, the peak-hopping sampling time and the number of cycle groups are set differently according to the type of each key target mineral, including: For zirconium minerals and phosphates, the single scan time for each lead isotope is 5-10 seconds, and the number of cycles is ≥20. For plagioclase, pyroxene, potassium feldspar, potassium glass, and troilite, the single scan time for each lead isotope is 60-120 seconds, with 10 cycles.

4. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 3, characterized in that, Step S5 also includes: Based on the beam size and ion current intensity used for the target mineral, differentiated standard samples were used to correct the peak positions of each lead isotope and control data quality, as follows: For target minerals with a particle size ≤10 micrometers, NIST-610 glass standard samples were used for peak position correction and monitoring; among them, for 204 For the Pb peak center, the peak scanning time is 5 seconds, and the signal reception integration time is 40 seconds; for 206 Pb, 207 Pb and 208 The peak center of Pb was scanned with a peak scanning time of 1 second and the signal receiving integration time was 20 seconds.

5. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, The two-stage fine polishing process in step S4 includes: polishing for 1 minute each with diamond polishing pastes of 0.5 micrometers and 0.25 micrometers particle sizes, at a polishing speed of 100 rpm; and / or The cleaning process in step S4 includes: sequentially cleaning the sample target after two-stage fine polishing with analytical grade alcohol, deionized water, and ultrapure water three times under ultrasonic conditions; and / or The drying process in step S4 includes: placing the cleaned sample target in a forced-air drying device for drying for more than 1 hour; and / or In step S4, the coating process uses gold plating to form a continuous conductive layer on the surface of the dried sample target.

6. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, In step S3, based on the change in cross-sectional area of ​​tiny target minerals with a particle size ≤10 micrometers after secondary polishing, minerals that meet the following rules are identified as candidate target minerals: S2≥90%×S1; Where S1 is the cross-sectional area of ​​the mineral after the first polishing; S2 is the cross-sectional area of ​​the mineral after the second polishing.

7. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, In step S3, when the initial sample target is polished a second time, a diamond polishing paste with a particle size of 0.25 micrometers is used, and the polishing time is 10±3 minutes, so that the sample target surface is removed by 1±0.1 micrometers of thickness.

8. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, Step S2 specifically includes: Surface scanning analysis was performed on the initial test sample target after carbon spraying to obtain secondary electron images, backscattered electron images, and energy spectrum surface distribution data. Based on the relative content, symbiotic relationship and spatial distribution characteristics of elements, minerals in the scanning area are identified; and based on the morphological characteristics of different minerals, the differences in backscatter brightness and the combination relationship of multiple elements, the target mineral to be tested is determined. The identified target minerals are recorded using coordinates, numbers, markers, layer overlays, and digital mineral distribution maps. The cross-sectional area of ​​the target minerals is also recorded, and the relative spatial position information of all target minerals on the sample target surface is established.

9. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, In step S2, during the initial surface scanning of the target sample, the spatial resolution of the secondary electron image and the backscattered electron image is better than 0.5 micrometers, the energy spectrum surface scanning resolution is better than 1 micrometer, and the scanning dwell time of a single pixel is greater than 0.2 milliseconds.

10. The method for determining lead isotopes in extraterrestrial samples based on the ion probe peak-hopping method according to claim 1, characterized in that, The standard samples selected in step S1 are glass standard samples, including: the standard samples are glass standard samples, including NIST610, NIST612, NIST614, BCR-2G, BHVO-2G, NIM-RM2720 and NIM-RM2722.

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