Method for testing and correcting rutile oxygen isotope

Abstract

The invention discloses a method for testing and correcting rutile oxygen isotope. The method comprises the following steps: carrying out stability test on a detection instrument by using a glass standard substance with a known oxygen isotope value; after the stability test passes, the detection instrument performs multi-group measurement on the crystal face of each rutile standard substance particle with the known oxygen isotope value, the measurement times and the total times in each group are the same, and a first standard deviation of each rutile standard substance particle with the known oxygen isotope value in each group is obtained; when the inter-group first standard deviation meets a first preset threshold value, a fractionation coefficient of the detection instrument is obtained through calculation; measuring the crystal face of the rutile sample with an unknown oxygen isotope value by the detection instrument, and obtaining a second average value between the groups, wherein the measurement depth is consistent with the measurement depth of the rutile standard substance particles with the known oxygen isotope value; and obtaining the oxygen isotope value of the unknown rutile sample by combining the fractionation coefficient of the detection instrument and the second average value among the groups. The method is fast, efficient and high in reliability.

Description

Technical Field

[0001] The present invention belongs to the field of chemical detection, and more particularly, relates to a method for testing and calibrating rutile oxygen isotopes. Background Art

[0002] Oxygen is the most widespread and abundant element in the Earth's crust, and its isotopic signature is widely used to study the evolution of oxygen-containing substances. In geological science research, oxygen isotopes are often used to analyze the properties of solid geological materials.

[0003] Rutile (TiO2) is a titanium-containing oxide mineral that is widely found in metamorphic rocks, igneous rocks, sedimentary rocks, mantle xenoliths, lunar rocks, and meteorites. Its geochemical characteristics, including oxygen isotope composition, are important for revealing the genesis of igneous, sedimentary, and metamorphic rocks. Studies have shown that under low-temperature conditions, the oxygen isotope composition of rutile can provide accurate estimates of formation temperatures and help understand the rock's origin and metamorphic equilibrium conditions. Furthermore, rutile oxygen isotopes are increasingly being used to study titanium mineralization and the formation of related deposits. Accurate analysis of rutile oxygen isotopes is of great value in the exploration and discovery of titanium resources.

[0004] At present, there are two main methods used internationally to determine the oxygen isotope composition of rutile: laser fluorination and secondary ion mass spectrometry (SIMS). Laser fluorination is a high-precision method for determining the oxygen isotope composition (such as δ 18 O) technology is widely used in geology, geochemistry and planetary science research. The steps include crushing the rock sample into micron-sized particles, selecting rutile minerals for cleaning and drying, then using a laser to heat the sample, generating gas through fluorination, and introducing the extracted oxygen into an isotope ratio mass spectrometer (IRMS) to measure the relative abundance of oxygen isotopes. Although the laser fluorination method has high testing accuracy and has been used for a long time, it is highly destructive to the sample, and overall sampling may mask changes in the sample micro-area. Secondary ion mass spectrometry (SIMS) has emerged as a suitable method for in-situ analysis of micro-areas. SIMS does not require mineral selection and can directly cut the rock into thin slices and select rutile for analysis. This technology has low sample consumption and the ability to perform repeated analysis for a long time. It is particularly suitable for rutile samples with a small particle size (such as around 50 microns). Through a high-precision and high-spatial-resolution ion probe, SIMS can directly measure the oxygen isotopes of rutile in rocks and effectively avoid interference from inclusions, thereby obtaining more accurate analysis results.

[0005] Despite this, SIMS analysis of rutile still faces challenges. Research has revealed a significant crystallographic orientation effect in rutile SIMS analysis. This effect occurs when certain physical or chemical properties (such as ion sputtering efficiency and signal intensity) vary with crystal orientation due to crystal anisotropy. In SIMS analysis of rutile oxygen isotopes, isotope ratios can vary significantly across different surface regions, impacting test reliability.

[0006] In view of this, overcoming the technical defects of the above-mentioned prior art is an urgent problem to be solved in this technical field. Summary of the Invention

[0007] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for testing and calibrating rutile oxygen isotopes, the purpose of which is to reduce the significant differences in the isotope ratios of rutile oxygen isotopes in different surface areas, thereby avoiding affecting the reliability of the test.

[0008] To achieve the above object, according to one aspect of the present invention, a method for testing and calibrating rutile oxygen isotopes is provided, the method comprising:

[0009] Use glass reference materials with known oxygen isotope values ​​to test the stability of the test instrument;

[0010] After the stability test is passed, the detection instrument performs multiple groups of measurements on the crystal faces of each rutile reference material particle with a known oxygen isotope value, with the same number of measurements within each group and the same total number of measurements, to obtain the first standard deviation between groups of each rutile reference material particle with a known oxygen isotope value in each group;

[0011] When the first standard deviation between the groups meets a first preset threshold, the fractionation coefficient of the detection instrument is calculated;

[0012] The detection instrument also measures the crystal surface of the rutile sample with an unknown oxygen isotope value, and the measurement depth is consistent with the measurement depth of the rutile standard material particles with a known oxygen isotope value, thereby obtaining a second average value between the groups;

[0013] The oxygen isotope value of the unknown rutile sample is obtained by combining the fractionation coefficient of the detection instrument and the second average value between the groups.

[0014] As a further improvement and supplement to the above solution, the present invention also includes the following additional technical features.

[0015] Preferably, the method for performing stability testing on a detection instrument using a glass standard substance with a known oxygen isotope value comprises:

[0016] Using the detection instrument to collect instrument signals of no less than three glass standard substances, and obtain the oxygen isotope value of each glass standard substance;

[0017] Calculate the distribution range of oxygen isotope values ​​of all glass standard materials 玻璃 ;

[0018] If the distribution range Range 玻璃 <1‰, indicating that the detection instrument has passed the stability test.

[0019] Preferably, the method for the detection instrument to perform multiple sets of measurements on the crystal faces of each rutile standard material particle with a known oxygen isotope value includes:

[0020] Measure two or more crystal planes of rutile standard materials with known oxygen isotope values.

[0021] Preferably, the method for obtaining the first standard deviation between each group of rutile reference material particles of known oxygen isotope value comprises:

[0022] The first inter-group average value of all particles at the same measurement depth is calculated based on the first intra-group average value and the first intra-group standard deviation of each rutile standard material particle with a known oxygen isotope value in the group;

[0023] The first standard deviation SD between groups is calculated from the first mean value between groups 已知 ;

[0024] If the first standard deviation SD between the groups 已知 Meet 2SD 已知 < the first preset threshold, indicating that the sampling range of rutile standard material particles with known oxygen isotope values ​​has passed the test.

[0025] Preferably, the fractionation coefficient of the detection instrument is calculated as follows:

[0026] The first average value between the groups that meets the sampling range test is subtracted from the known oxygen isotope value of the rutile standard material.

[0027] Preferably, the method for obtaining the oxygen isotope value of the rutile sample in combination with the fractionation coefficient of the detection instrument includes:

[0028] The inter-group second mean of all particles at the same measurement depth is calculated based on the intra-group second mean and intra-group second standard deviation of each rutile sample with unknown oxygen isotope value within the group.

[0029] Preferably, the oxygen isotope value of the rutile sample is calculated as follows:

[0030] The fractionation coefficient of the detection instrument is added to the second average value between the groups.

[0031] Preferably, at least one glass standard material with a known oxygen isotope value, at least one rutile standard material with a known oxygen isotope value, and at least one rutile sample with an unknown oxygen isotope value are located in the same plane during testing.

[0032] Preferably, the method further comprises:

[0033] Double-sided tape is pasted on a glass sheet, and the glass standard material with known oxygen isotope value, the rutile standard material with known oxygen isotope value, and the rutile sample with unknown oxygen isotope value are pasted on the double-sided tape.

[0034] Preferably, the method for measuring the oxygen isotope value in the method is:

[0035] use 133 Cs + Ion source, which irradiates the focused ion beam onto the material to be tested, with a beam spot size of 20μm 2 , to excite the substance to be tested to produce secondary ions;

[0036] The secondary ions released by the substance to be tested pass through the electric field and magnetic field in sequence and finally reach the ion signal detection system.

[0037] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0038] The present invention provides a method for testing and calibrating rutile oxygen isotopes. By comparing fractionation characteristics with instrument stability, it can accurately determine the oxygen isotope composition of a sample. This method is rapid, efficient, and highly reliable, significantly improving the accuracy of rutile oxygen isotope measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0040] Figure 1 This is a flow chart of a method for testing and calibrating rutile oxygen isotopes provided in Example 1;

[0041] Figure 2 a is a graph showing the relationship between the accuracy of the rutile oxygen isotope measurement value measured by SIMS and the measurement depth in Example 1;

[0042] Figure 2b is a graph showing the relationship between the rutile oxygen isotope measurement values ​​obtained using SIMS and the measurement depth in Example 1;

[0043] Figure 3 a is a side view of the sample target provided in Example 1;

[0044] Figure 3 b is a distribution diagram of the glass standard substance, rutile standard substance and the sample to be tested on the surface of the sample target in the first embodiment. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0046] Existing techniques can reduce the potential for significant variations in isotope ratios between different surface regions of rutile oxygen isotopes. To mitigate this, researchers have proposed various approaches. For example, Schmitt and Zack proposed combining SIMS with electron backscatter diffraction (EBSD) to assess the influence of crystal orientation; Shulaker et al. attempted to mitigate the crystal orientation effect by reducing the incident primary ion intensity. However, these methods still face significant reproducibility issues in practical applications, resulting in significant intra- and inter-grain variations in SIMS-based rutile oxygen isotope test results.

[0047] Since the measurement of rutile oxygen isotopes is affected by the crystal orientation effect, it is necessary to study the distribution law of oxygen isotopes inside it in order to establish a correction method and improve the precision and accuracy of the test results.

[0048] Example 1

[0049] This embodiment provides a method for testing and calibrating rutile oxygen isotopes, the method comprising the following steps: Figure 1 As shown:

[0050] S101: Use glass reference materials with known oxygen isotope values ​​to perform stability tests on the detection instrument.

[0051] Use glass reference materials with known oxygen isotope values ​​to test the stability of the instrument. For example:

[0052] Collect the oxygen isotope values ​​of 10 sets of glass standard materials, denoted as δ 18 O Measured-Nist610-1 , δ 18 O Measured-Nist610-2 ,…,δ18 O Measured-Nist610-10 )

[0053] Calculate the standard deviation SD of the above 10 groups of data 玻璃 , recorded as SD Nist610 , if 2SD is satisfied Nist610 <0.6‰, proceed to the next step; otherwise, debug the instrument and repeat the first step until the conditions are met.

[0054] S102: After the stability test is passed, the detection instrument performs multiple groups of measurements on the crystal surface of each rutile standard material particle with a known oxygen isotope value. The number of measurements within each group and the total number of measurements are the same, and the first standard deviation between groups of each rutile standard material particle with a known oxygen isotope value in each group is obtained.

[0055] Collecting oxygen isotopes of rutile standard materials 18 O and 16 O instrument signal and calculate its oxygen isotope ratio data using the Vienna Standard Mean Ocean Water (VSMOW); 18 O / 16 O=0.0020052) for normalization, the formula is as follows: 18 O VSMOW =(( 18 O / 16 O)Measured value / 0.0020052-1)×1000. For example:

[0056] 2000 measurements were performed on 10 particles of a rutile standard material (NR201) with known oxygen isotope values.

[0057] The first measured ratio of the first particle is recorded as D -NR201-p1-C1 ,

[0058] The kth measurement ratio of the first particle is recorded as D -NR201-p1-Ck , where k = 1, 2,…, 2000.

[0059] The first measurement ratio of the jth particle is recorded as D -NR201-pj-C1 , where j = 1, 2, ..., 10

[0060] The kth measurement ratio of the jth particle is recorded as D -NR201-pj-Ck , where j = 1, 2,…, 10, k = 1, 2,…, 2000.

[0061] The measurement results of each particle are divided into a group of 40 consecutive measurements.

[0062] Group 1: 1st to 40th measurements.

[0063] Group 2: 41st to 80th measurements.

[0064] Group i: kth to k+39th measurements.

[0065] Where i = 1, 2, ..., 50; K = (i-1) * 40 + 1, the values ​​are (1, 41, 81, ..., 1961)

[0066] The last group: measurements 1961 to 2000.

[0067] Calculate the first mean and first standard deviation of the rutile reference material sample within the group:

[0068] The first mean and standard deviation of the i-th group of the j-th particle in the NR201 sample are denoted as A -NR201-pj-gi and SD -NR201-pj-gi ,

[0069]

[0070] Where j = 1, 2,…, 10; i = 1, 2,…, 50; k = (i-1)*40+1, and the resulting values ​​are (1, 41, 81,…, 1961) respectively.

[0071]

[0072] Among them, j=1,2,…,10; i=1,2,…,50; k=(i-1)*40+1, and the resulting values ​​are (1,41,81,…,1961) respectively.

[0073] Then calculate the first inter-group mean value and the first inter-group standard deviation of all rutile reference material sample particles in the same group, that is, at the same measurement depth.

[0074] The first inter-group mean of group i is:

[0075] Where j = 1, 2, ..., 10; i = 1, 2, ..., 50;

[0076] The first standard deviation between groups of group i is:

[0077] Where j = 1, 2,…, 10; i = 1, 2,…, 50.

[0078] S103: When the first standard deviation between the groups meets the first preset threshold, the fractionation coefficient of the detection instrument is calculated.

[0079] The first preset threshold is set to 0.6‰. If 2SD -NR201-giIf the value of i is less than or equal to 0.6‰, the current value of i is taken and the process proceeds to S104; otherwise, the process continues until the condition is met. The range of i is 1-50, and the first i that meets the condition is used as the reference, and the subsequent values ​​are discarded.

[0080] According to the known value of rutile standard material δ 18 O NR201 =6.80‰, calculate the fractionation coefficient IMF:

[0081] IMF=δ 18 O NR201 -AA NR201-gi .

[0082] S104: The detection instrument also measures the crystal surface of the rutile sample with an unknown oxygen isotope value. The measurement depth is consistent with the measurement depth of the rutile standard material particles with a known oxygen isotope value, and the second average value between the groups is obtained.

[0083] Calculate the second mean and second standard deviation of all unknown oxygen isotope values ​​of rutile samples (NR202) in the same group, at the same depth as the measurement of the rutile reference material sample particles.

[0084] The second mean between groups of group i is:

[0085] Where j = 1, 2, ..., 10; i = 1, 2, ..., 50;

[0086] S105: The oxygen isotope value of the unknown rutile sample is obtained by combining the fractionation coefficient of the detection instrument and the second average value between groups.

[0087] Combined with the fractionation coefficient IMF obtained in S103, the oxygen isotope value δ of the rutile sample with unknown oxygen isotope value is calculated 18 O NR202 , δ 18 O NR202 =IMF+AA NR202-gi .

[0088] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the method of using a glass standard substance with a known oxygen isotope value to perform a stability test on a detection instrument includes:

[0089] Using the detection instrument to collect instrument signals of no less than three glass standard substances, and obtain the oxygen isotope value of each glass standard substance;

[0090] Calculate the distribution range of oxygen isotope values ​​of all glass standard materials 玻璃 ;

[0091] If the distribution range Range 玻璃<1‰, indicating that the detection instrument has passed the stability test.

[0092] In this embodiment 1, 10 glass standard substances are selected.

[0093] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the method of performing multiple groups of measurements on the crystal faces of each rutile reference material particle with a known oxygen isotope value by the detection instrument includes:

[0094] Measure two or more crystal planes of rutile standard materials with known oxygen isotope values.

[0095] In the first embodiment of the present invention, multiple measurements are performed on different crystal faces of a rutile standard material with known oxygen isotope values. By calculating the variation range of the rutile measurement values ​​in different test time periods, the measurement value with a variation range less than or equal to the variation range of the instrument is taken as the best measurement result. The corresponding sampling time and sampling range are determined as the optimal test time and sampling range of the rutile sample, thereby improving the measurement accuracy.

[0096] The optimal test time and sampling range is to obtain a stable interval of the later measurement value through long-term measurement. The stable measurement value is reflected by the smaller SD. When the instrument is stable, the sampling range at the same time point is the same. In this embodiment, the first standard deviation is set to meet 2SD -NR201-gi Less than 0.6‰.

[0097] like Figure 2 Figure a shows the relationship between the accuracy of rutile oxygen isotope measurements using SIMS and the measurement depth. For a rutile sample with uniform oxygen isotope values, such as the rutile standard material NR201 with three known oxygen isotope values, the accuracy of the oxygen isotope value is 2SD = 0.18‰. Although the SIMS measurements on multiple particle surfaces show large variations, such as using a 40-cycle test with a test time of 3 minutes, and Figure 2 After the red curves of the three different particles in b correspond, Figure 2 The precision (i.e., twice the standard deviation) of the measured values ​​for the three different test particles in Figure a is 2SD = 3.78‰. However, as the test depth and test time increase, the oxygen isotope values ​​measured on different crystal planes gradually converge, significantly improving the measurement precision. However, if the test is increased to 2000 cycles, with a test time of 76 minutes, the precision decreases to 2SD = 0.58‰.

[0098] like Figure 2As shown in a, the horizontal axis is the number of cycles measured, a total of 2000 cycles, and each cycle is 2 seconds. The vertical axis is the change in the rutile oxygen isotope ratio, which is expressed here as twice the standard deviation between groups, that is, 2SD. It can be seen that as time (that is, the number of cycles) increases, the change in the rutile oxygen isotope ratio becomes smaller. For example, the 2SD from the first cycle to the fortieth cycle is 3.78‰, which is Figure 2 The first point of a. The 2SD from the 1961st cycle to the 2000th cycle is 0.58‰, which is Figure 2 The last point of a.

[0099] like Figure 2 As shown in b, the relationship between the measured values ​​of rutile oxygen isotopes obtained by SIMS and the measurement depth. Since SIMS is a relative measurement method, it was found that at the same measurement depth, the test values ​​of different rutile samples have consistent instrument fractionation coefficients. The instrument fractionation coefficient varies from Figure 2 In Figure (b), the difference between the vertical coordinates of the red and green curves is consistent. By calibrating rutile reference material particles with known oxygen isotope values ​​against rutile samples with unknown oxygen isotope values, the oxygen isotope values ​​of the rutile samples can be accurately determined, enabling highly accurate measurements. This discovery provides a scientific basis for addressing measurement errors caused by rutile crystal orientation effects and lays the foundation for calibration methods.

[0100] like Figure 2 As shown in b, the horizontal axis is the number of cycles measured, a total of 2000 cycles, each cycle is 2 seconds. The vertical axis is the measured value of the rutile oxygen isotope ratio, expressed as δ 18 The calculation method is: using Vienna Standard Mean Ocean Water (VSMOW; 18 O / 16 O=0.0020052) for normalization, the formula is as follows: 18 O VSMOW =(( 18 O / 16 O) measured value / 0.0020052-1)×1000. The figure shows two different rutile samples. The red curve shows the time-varying values ​​of three NR201 measurements; the green curve shows the time-varying values ​​of three NR202 measurements. The difference between the average of the three NR201 and three NR202 measurements remains constant over time. This indicates that the instrumental fractionation characteristics of the two samples are identical, meaning that the rutile fractionation coefficients are identical at the same test time / depth / cycle.

[0101] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the method for obtaining the first standard deviation between each group of rutile reference material particles with known oxygen isotope values ​​includes:

[0102] The first inter-group average value of all particles at the same measurement depth is calculated based on the first intra-group average value and the first intra-group standard deviation of each rutile standard material particle with a known oxygen isotope value in the group;

[0103] The first standard deviation SD between groups is calculated from the first mean value between groups 已知 ;

[0104] If the first standard deviation SD between the groups 已知 Meet 2SD 已知 < the first preset threshold, indicating that the sampling range of rutile standard material particles with known oxygen isotope values ​​has passed the test.

[0105] In this embodiment 1, the first mean value and the first standard deviation of the rutile reference material sample within the group are calculated:

[0106] The first mean value and the first standard deviation of the i-th group of the j-th particle in the rutile standard material sample NR201 are expressed as A -NR201-pj-gi and SD -NR201-pj-gi ,

[0107]

[0108] Where j = 1, 2,…, 10; i = 1, 2,…, 50; k = (i-1)*40+1, and the resulting values ​​are (1, 41, 81,…, 1961) respectively.

[0109]

[0110] Where j = 1, 2,…, 10; i = 1, 2,…, 50; K = (i-1)*40+1, and the resulting values ​​are (1, 41, 81,…, 1961) respectively.

[0111] Then calculate the first average value and the first standard deviation among all rutile standard material sample particles in the same group, ie, at the same measurement depth.

[0112] The first inter-group mean of group i is:

[0113] Where j = 1, 2, ..., 10; i = 1, 2, ..., 50;

[0114] The first standard deviation between groups of group i is:

[0115] Where j = 1, 2,…, 10; i = 1, 2,…, 50.

[0116] The first preset threshold is set to 0.6‰. If 2SD -NR201-gi If the value of i is less than 0.6‰, the current value of i is used and the next step is entered; otherwise, the calculation continues until the condition is met. The range of i is 1-50.

[0117] In the first embodiment, the value of i is 50, the first inter-group mean value of the i-th group is -51.51‰, and the first inter-group standard deviation of the i-th group is 0.58‰.

[0118] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the calculation method of the fractionation coefficient of the detection instrument is:

[0119] The first average value between the groups that meets the sampling range test is subtracted from the known oxygen isotope value of the rutile standard material.

[0120] In this embodiment 1, the known value δ of the rutile standard substance 18 O NR201 =6.80‰, fractionation coefficient IMF: IMF = δ 18 O NR201 -AA NR201-gi In this embodiment, the value of IMF is 58.3‰

[0121] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the method for obtaining the oxygen isotope value of the rutile sample in combination with the fractionation coefficient of the detection instrument includes:

[0122] The inter-group second mean of all particles at the same measurement depth is calculated based on the intra-group second mean and intra-group second standard deviation of each rutile sample with unknown oxygen isotope value within the group.

[0123] In this Example 1, the second mean value and the second standard deviation of the rutile sample (NR202) with unknown oxygen isotope value are calculated:

[0124] The second mean and standard deviation of the i-th group of the j-th grain in the rutile sample NR202 with unknown oxygen isotope value are expressed as A -NR202-pj-gi and SD -NR202-pj-gi ,

[0125]

[0126] Where j = 1, 2,…, 10; i = 1, 2,…, 50; k = (i-1)*40+1, and the resulting values ​​are (1, 41, 81,…, 1961) respectively.

[0127] When i=50, the second mean value of the j=1 NR202 particle within the group is -59.72‰; when i=50, the second mean value of the j=2 NR202 particle within the group is -59.81‰; when i=50, the second mean value of the j=3 NR202 particle within the group is -59.62‰, and the second standard deviation within the group is calculated again;

[0128]

[0129] Among them, j=1,2,…,10; i=1,2,…,50; k=(i-1)*40+1, and the resulting values ​​are (1,41,81,…,1961) respectively.

[0130] Then calculate the second average value among all rutile standard material sample particles in the same group, that is, the same measurement depth.

[0131] The second mean between groups of group i is:

[0132] Where j = 1, 2,…, 10; i = 1, 2,…, 50.

[0133] In this embodiment 1, the second average value among the groups of rutile sample NR202 is -59.72‰.

[0134] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the calculation method of the oxygen isotope value of the rutile sample is:

[0135] The fractionation coefficient of the detection instrument is added to the second average value between the groups.

[0136] In this Example 1, the oxygen isotope value δ of the rutile sample with unknown oxygen isotope value is 18 O NR202 , δ 18 O NR202 =IMF+AA NR202-gi .

[0137] In this example 1, the oxygen isotope value of the rutile sample with unknown oxygen isotope value is -1.40‰

[0138] In combination with this embodiment, there is also a preferred implementation scheme, specifically, at least one glass standard with a known oxygen isotope value, at least one rutile standard material with a known oxygen isotope value, and at least one rutile sample with an unknown oxygen isotope value are located in the same plane during testing.

[0139] like Figure 3 a and Figure 3As shown in b, there are multiple rutile standard materials NR201, multiple samples to be tested NR202 and multiple glass standard materials Nist610 on the sample target surface.

[0140] In combination with this embodiment, there is also a preferred implementation scheme. Specifically, double-sided tape is stuck on a glass sheet, and the glass standard material with known oxygen isotope value, the rutile standard material with known oxygen isotope value, and the rutile sample with unknown oxygen isotope value are stuck on the double-sided tape.

[0141] In the first embodiment, a target is first prepared, which contains a glass standard material, a rutile standard material and a rutile sample to be tested.

[0142] Since the stability of the instrument requires a standard material with known oxygen isotope results to monitor, the glass standard material NIST610 developed by the National Institute of Standards and Technology of the United States was selected. This standard material has a uniform oxygen isotope value δ 18 O Nist610 =10.91±0.20‰.

[0143] Due to the matrix effect of the ion probe, a sample with a composition similar to that of the sample to be tested is required as a standard material. Therefore, a rutile sample that has been tested for oxygen isotopes using a traditional method is selected as a standard material. In this example, the rutile NR201 sample from the Kinyanfumbe area of ​​Zambia is selected. The oxygen isotope value of this sample obtained by the traditional method is δ 18 O NR201 =6.80±0.18‰. Here, NR201 is used as a standard material to determine the test time range and sampling interval of rutile, and the instrument fractionation coefficient is calculated to establish the method. A rutile NR202 sample from the Graves Mountain area in the United States is selected as the test sample for testing. The oxygen isotope of this rutile sample has been measured using traditional methods and is: δ 18 O NR202 =-1.98±0.34‰. The rutile sample NR202 with known oxygen isotope value was used as the test sample to verify this method.

[0144] The specific process of making the target is as follows: stick a 10cm*5cm double-sided tape on a 10cm*10cm glass sheet, and stick 10-12 particles of glass standard material Nist610 with a particle size of 100-250 microns, 10-12 particles of rutile standard material NR201 with a particle size of 100-250 microns, and 10-12 particles of test sample NR202 with a particle size of 100-250 microns into a 1 cm diameter circle on the double-sided tape. Mix the epoxy resin with the coagulant; place a polyethylene hollow column with a smooth surface and an inner diameter of 1 inch vertically on the double-sided tape, and place the above-mentioned glass and rutile particles in the middle of the polyethylene hollow column; slowly inject the vacuumed mixture of the epoxy resin and the coagulant along the inner surface of the polyethylene hollow column, vacuum again and let it stand to solidify the mixture, then remove the polyethylene hollow column and tear off the double-sided tape to obtain a solidified rutile ore standard material sheet that can be taken out of the polyethylene hollow column. Use fine sandpaper and polishing disc to grind and polish the rutile ore target in turn, so that the glass standard material Nist610 and the rutile standard material NR201, and the sample to be tested NR202 are exposed on one side of the target surface, and the entire surface is bright and smooth. The prepared target is as follows Figure 3 shown. Figure 3 a is the overall image, which is a disc. Figure 3 b is the surface morphology. Figure 3 b is Figure 3 a Distribution diagram of the sample target surface at 50 times magnification.

[0145] In the first embodiment, rutile was tested using secondary ion mass spectrometry (SIMS).

[0146] First, clean the surface of the sample target with clean water, place the sample target in a beaker filled with alcohol, use an ultrasonic instrument to ultrasonically clean the sample for three minutes, and then place the sample target in a drying oven to dry for one hour.

[0147] A Q150TE gold plating machine from Quorum is used to plate a continuous gold film on the exposed surface of the cleaned wafer sample target. To ensure good conductivity of the sample, the coating thickness is between 20nm and 50nm. For example, it can be 20nm or only 45nm.

[0148] The signal required for rutile oxygen isotope detection was measured by secondary ion mass spectrometry. 133 Cs + Ion source, irradiates the focused ion beam onto the glass or rutile sample on the sample target, with a beam spot area size of 20μm 2 , to excite the sample to produce secondary ions. Subsequently, the secondary ions released by the sample 16 O and 18O passes through the electric and magnetic fields in sequence and finally reaches the ion signal detection system. Collecting oxygen isotopes of rutile standard materials 18 O and 16 O instrument signal and calculate its oxygen isotope ratio data using the Vienna Standard Mean Ocean Water (VSMOW); 18 O / 16 O=0.0020052) for normalization, the formula is as follows: 18 O VSMOW =(( 18 O / 16 = (O) measured value / 0.0020052-1) × 1000. During the detection process, two Faraday cups were used to simultaneously receive the secondary ion signal. Each test cycle consisted of at least 2000 cycles, with each cycle lasting 2 seconds.

[0149] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for testing and calibrating rutile oxygen isotopes, characterized in that: Methods include: Use glass reference materials with known oxygen isotope values ​​to test the stability of the test instrument; After the stability test is passed, the detection instrument performs multiple groups of measurements on the crystal faces of each rutile reference material particle with a known oxygen isotope value, with the same number of measurements within each group and the same total number of measurements, to obtain the first standard deviation between groups of the rutile reference material particles with each known oxygen isotope value in each group; When the first standard deviation between the groups meets a first preset threshold, the fractionation coefficient of the detection instrument is calculated; The detection instrument also measures the crystal surface of the rutile sample with an unknown oxygen isotope value, and the measurement depth is consistent with the measurement depth of the rutile standard material particles with a known oxygen isotope value, thereby obtaining a second average value between the groups; The oxygen isotope value of the unknown rutile sample is obtained by combining the fractionation coefficient of the detection instrument and the second average value between the groups.

2. The method for testing and calibrating rutile oxygen isotopes according to claim 1, wherein: The method for performing stability testing on a detection instrument using a glass standard substance with a known oxygen isotope value comprises: Using the detection instrument to collect instrument signals of no less than three glass standard substances, and obtain the oxygen isotope value of each glass standard substance; Calculate the distribution range of oxygen isotope values ​​of all glass standard materials 玻璃 ; If the distribution range Range 玻璃 <1‰, indicating that the detection instrument has passed the stability test.

3. The method for testing and calibrating rutile oxygen isotopes according to claim 1, wherein: The method for the detection instrument to perform multiple groups of measurements on the crystal faces of each rutile standard material particle with a known oxygen isotope value includes: Measure two or more crystal planes of rutile standard materials with known oxygen isotope values.

4. The method for testing and calibrating rutile oxygen isotopes according to claim 1, wherein: The method for obtaining the first standard deviation between each group of rutile reference material particles of each known oxygen isotope value comprises: The first inter-group average value of all particles at the same measurement depth is calculated from the first intra-group average value and the first intra-group standard deviation of each rutile reference material particle with a known oxygen isotope value in the group; The first standard deviation SD between groups is calculated from the first mean value between groups 已知 ; If the first standard deviation SD between the groups 已知 Meet 2SD 已知 < the first preset threshold, indicating that the sampling range of rutile standard material particles with known oxygen isotope values ​​has passed the test.

5. The method for testing and calibrating rutile oxygen isotopes according to claim 4, wherein: The calculation method of the fractionation coefficient of the detection instrument is: The first average value between the groups that meets the sampling range test is subtracted from the known oxygen isotope value of the rutile standard material.

6. The method for testing and calibrating rutile oxygen isotopes according to claim 5, wherein: The method for obtaining the oxygen isotope value of a rutile sample in combination with the fractionation coefficient of the detection instrument includes: The inter-group second mean of all particles at the same measurement depth is calculated based on the intra-group second mean and intra-group second standard deviation of each rutile sample with unknown oxygen isotope value within the group.

7. The method for testing and calibrating rutile oxygen isotopes according to claim 6, wherein: The calculation method of the oxygen isotope value of the rutile sample is: The fractionation coefficient of the detection instrument is added to the second average value between the groups.

8. The method for testing and calibrating rutile oxygen isotopes according to claim 1, wherein: At least one glass standard material with a known oxygen isotope value, at least one rutile standard material with a known oxygen isotope value, and at least one rutile sample with an unknown oxygen isotope value are located in the same plane during testing.

9. The method for testing and calibrating rutile oxygen isotopes according to claim 8, wherein: The method further comprises: Double-sided tape is pasted on a glass sheet, and the glass standard material with known oxygen isotope value, the rutile standard material with known oxygen isotope value, and the rutile sample with unknown oxygen isotope value are pasted on the double-sided tape.

10. The method for testing and calibrating rutile oxygen isotopes according to claim 8, wherein: The method for measuring the oxygen isotope value in the method is: use 133 Cs + Ion source, which irradiates the focused ion beam onto the material to be tested, with a beam spot size of 20μm 2 , to excite the substance to be tested to produce secondary ions; The secondary ions released by the substance to be tested pass through the electric field and magnetic field in sequence and finally reach the ion signal detection system.

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