A method of testing and correcting for rutile oxygen isotopes

Abstract

This invention discloses a method for testing and calibrating rutile oxygen isotopes. The method includes: performing a stability test on a detection instrument using glass standard materials with known oxygen isotope values; after passing the stability test, the detection instrument performs multiple sets of measurements on the crystal planes of rutile standard material particles with known oxygen isotope values, with the number of measurements within each group and the total number of measurements being the same, obtaining the first standard deviation between groups for each rutile standard material particle with known oxygen isotope value; when the first standard deviation between groups meets a first preset threshold, the fractionation coefficient of the detection instrument is calculated; the detection instrument also measures the crystal planes of rutile samples with unknown oxygen isotope values, with the measurement depth consistent with the measurement depth of rutile standard material particles with known oxygen isotope values, obtaining a second average value between groups; combining the fractionation coefficient of the detection instrument and the second average value between groups, the oxygen isotope value of the rutile sample with unknown oxygen isotope value is obtained. This method is fast, efficient, and highly reliable.

Description

Technical Field

[0001] This invention belongs to the field of chemical detection, and more specifically, relates to a method for testing and calibrating rutile oxygen isotopes. Background Technology

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

[0003] Rutile (TiO2) is a titanium-bearing oxide mineral widely found in metamorphic rocks, igneous rocks, sedimentary rocks, mantle xenoliths, lunar rocks, and meteorites. Its geochemical characteristics (including oxygen isotope composition) are crucial 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 temperature and help understand rock origins and metamorphic equilibrium conditions. Furthermore, rutile oxygen isotopes are increasingly being used to study titanium mineralization and the formation processes of related deposits. Precise analysis of rutile oxygen isotopes is of great value for the exploration and discovery of titanium resources.

[0004] Currently, two main methods are used internationally for determining rutile oxygen isotopes: laser fluorination and secondary ion mass spectrometry (SIMS). Laser fluorination is a high-precision method for determining oxygen isotope composition (such as δ¹²⁻¹). 18 The technique of fluorination (O) is widely used in geological, geochemical, and planetary science research. Its steps involve crushing rock samples to micron-sized particles, selecting rutile minerals, washing and drying them, then heating the sample with a laser to generate gas via fluorination, and introducing the extracted oxygen into an isotope ratio mass spectrometer (IRMS) to measure the relative abundance of oxygen isotopes. Although laser fluorination is highly accurate and has been used for a long time, it is relatively destructive to the sample, and whole-sample processing may mask variations in micro-regions. Secondary ion mass spectrometry (SIMS) has emerged to address this need, suitable for in-situ analysis of micro-regions. SIMS eliminates the need for mineral selection; rutile can be directly analyzed after preparing thin sections of the rock. This technique consumes less sample, allows for repeated analysis over long periods, and is particularly suitable for small-particle rutile samples (e.g., around 50 micrometers). Using high-precision and high spatial resolution ion probes, SIMS can directly determine the oxygen isotopes of rutile in rocks and effectively avoid interference from inclusions, thus obtaining more accurate analytical results.

[0005] Despite this, SIMS testing of rutile remains challenging. Studies have revealed a significant crystallographic orientation effect in rutile SIMS analysis. This effect arises because crystal anisotropy causes certain physical or chemical properties (such as ion sputtering efficiency and signal intensity) to vary with crystal orientation. In rutile oxygen isotope SIMS analysis, isotope ratios can differ significantly across different surface regions, affecting the reliability of the test.

[0006] Therefore, overcoming the technical defects of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0007] In view of 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 different surface regions of rutile oxygen isotopes and avoid affecting the reliability of the test.

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

[0009] Stability tests were conducted on the detection instrument using glass standard materials with known oxygen isotope values.

[0010] After the stability test is passed, the detection instrument performs multiple sets of measurements on the crystal plane 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, so as to obtain the first standard deviation between each group of rutile standard material particles with a known oxygen isotope value.

[0011] The fractionation coefficient of the detection instrument is calculated after the first standard deviation between groups meets the first preset threshold.

[0012] The detection instrument also measures the crystal plane of rutile samples with unknown oxygen isotope values. The measurement depth is consistent with the measurement depth of rutile standard material particles with known oxygen isotope values, and the second average value between groups is obtained.

[0013] The oxygen isotope value of the unknown rutile sample was obtained by combining the fractionation coefficient of the detection instrument and the second average value between 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 testing the stability of the detection instrument using glass standard materials with known oxygen isotope values ​​includes:

[0016] The instrument signal of no less than three glass standard substances is collected using the aforementioned detection instrument to obtain the oxygen isotope value of each glass standard substance.

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

[0018] If the distribution range Range 玻璃 <1‰ indicates that the testing instrument has passed the stability test.

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

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

[0021] Preferably, the method for obtaining the first standard deviation between groups of rutile standard material particles with each known oxygen isotope value includes:

[0022] The first mean of all particles at the same measurement depth was calculated from the first mean within the group and the first standard deviation within the group for each rutile standard material particle with a known oxygen isotope value.

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

[0024] If the first standard deviation between groups SD 已知 Meets 2SD 已知 <First preset threshold indicates 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 known oxygen isotope value of the rutile standard reference is subtracted from the first average value between groups that satisfies the sampling range test.

[0027] Preferably, the method for obtaining the oxygen isotope value of a rutile sample by combining the fractionation coefficient of the detection instrument includes:

[0028] The second mean of all particles at the same measurement depth was calculated from the second mean within the group and the second standard deviation within the group for each rutile sample with an unknown oxygen isotope value.

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

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

[0031] Preferably, at least one glass standard with a known oxygen isotope value, at least one rutile standard 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 includes:

[0033] Double-sided tape is applied to a glass slide, 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 then attached to the double-sided tape.

[0034] Preferably, the method for measuring oxygen isotope values ​​in the method is as follows:

[0035] use 133 Cs + The ion source focuses the ion beam onto the analyte, with a beam size of 20 μm. 2 To excite the analyte to generate secondary ions;

[0036] Secondary ions released by the analyte pass through an electric field and a magnetic field in sequence before finally reaching the ion signal detection system.

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

[0038] This invention provides a method for testing and calibrating rutile oxygen isotopes. Through comparative analysis of fractionation characteristics and instrument stability, it can accurately determine the oxygen isotopes of the sample. This method is rapid, efficient, and highly reliable, greatly improving the accuracy of rutile oxygen isotope determination. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0040] Figure 1 This is a schematic flowchart of a method for testing and calibrating rutile oxygen isotopes provided in this embodiment.

[0041] Figure 2 a is a graph showing the relationship between the accuracy of rutile oxygen isotope measurements using SIMS testing and the measurement depth in this first embodiment.

[0042] Figure 2b is a graph showing the relationship between the rutile oxygen isotope measurement values ​​obtained by SIMS and the measurement depth in this embodiment 1.

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

[0044] Figure 3 b is a distribution diagram of the glass standard material, rutile standard material, and the sample to be tested on the sample target surface in this embodiment. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] In existing techniques, reducing the significant differences in isotopic ratios of rutile oxygen isotopes across different surface regions can affect the reliability of measurements. Researchers have proposed various approaches. For example, Schmitt and Zack suggested combining SIMS with electron backscatter diffraction (EBSD) to assess the influence of crystal orientation; Shulaker et al. attempted to reduce the crystal orientation effect by decreasing the incident intensity of primary ions. However, these methods still suffer from significant reproducibility issues in practical applications, resulting in significant intragranular or intergranular variations in SIMS-based rutile oxygen isotope measurements.

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

[0048] Example 1

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

[0050] S101: Use glass standard materials with known oxygen isotope values ​​to test the stability of the detection instrument.

[0051] The stability of the instrument is tested using glass standard materials with known oxygen isotope values. For example:

[0052] Collect oxygen isotope values ​​for 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 sets of data. 玻璃 , denoted as SD Nist610 If 2SD is satisfied Nist610 If the value is less than 0.6‰, proceed to the next step; otherwise, adjust the instrument and repeat step one until the condition is met.

[0054] S102: After the stability test is passed, the testing instrument performs multiple sets of measurements on the crystal plane 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 for each rutile standard material particle with a known oxygen isotope value is obtained.

[0055] Collection of rutile standard material oxygen isotopes 18 O and 16 The instrument signal of O was collected, and its oxygen isotope ratio data were calculated using the Vienna Standard Mean Seawater (VSMOW). 18 O / 16 Normalization is performed on O = 0.0020052, using the following formula: Measured δ 18 O VSMOW =(( 18 O / 16 O)Measured value / 0.0020052-1)×1000. For example:

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

[0057] The ratio of the first measurement of the first particle is denoted as D. -NR201-p1-C1 ,

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

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

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

[0061] The measurement results for each particle were grouped into sets of 40 consecutive measurements.

[0062] Group 1: Measurements 1 through 40.

[0063] Group 2: Measurements from the 41st to the 80th.

[0064] Group i: Measurements from the kth to the (k+39th)th time.

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

[0066] The last group: measurements from the 1961st to the 2000th.

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

[0068] The first mean and first standard deviation within the group of the j-th particle in the ith group of 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 values ​​are (1, 41, 81, ..., 1961).

[0071]

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

[0073] Then calculate the first mean and first standard deviation between groups for all rutile standard material sample particles in the same group, i.e., at the same measurement depth.

[0074] The first mean between groups for group i is:

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

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

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

[0078] S103: The fractionation coefficient of the testing instrument is calculated after the first standard deviation between groups meets the first preset threshold.

[0079] The first preset threshold is set to 0.6‰, if 2SD -NR201-giIf the value is less than or equal to 0.6‰, take the current value of i and proceed to S104; otherwise, continue calculation until the condition is met. The range of i is 1-50, and the first i that meets the condition is used, while the subsequent ones are discarded.

[0080] Based on the known value δ of rutile standard material 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 plane of rutile samples with unknown oxygen isotope values. The measurement depth is consistent with the measurement depth of rutile standard material particles with known oxygen isotope values, and the second average value between groups is obtained.

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

[0084] The second mean between groups for 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] Using the fractionation coefficient IMF obtained from S103, the oxygen isotope value δ of the rutile sample with unknown oxygen isotope value was 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 for testing the stability of the detection instrument using glass standard materials with known oxygen isotope values ​​includes:

[0089] The instrument signal of no less than three glass standard substances is collected using the aforementioned detection instrument to obtain the oxygen isotope value of each glass standard substance.

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

[0091] If the distribution range Range 玻璃<1‰ indicates that the testing instrument has passed the stability test.

[0092] In this first embodiment, 10 glass standard substances were selected.

[0093] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, the method for the detection instrument to perform multiple sets of measurements on the crystal facets of rutile standard material particles with known oxygen isotope values ​​includes:

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

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

[0096] The optimal testing time and sampling range are obtained by measuring over a long period of time to achieve a stable range of measurement values. Stable measurement values ​​are characterized by a decreasing standard deviation (SD). When the instrument is stable, the sampling range at the same time point is the same. In this first embodiment, the first standard deviation is set to satisfy 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 rutile samples with uniform oxygen isotope values, such as the rutile standard NR201 with three known oxygen isotope values, the accuracy of the oxygen isotope values ​​is 2SD = 0.18‰, although there are significant differences in the accuracy of SIMS measurements on multiple particle surfaces, such as when using a 40-cycle test with a test time of 3 minutes. Figure 2 After the red curves of the three different particles in b correspond, Figure 2 The accuracy (i.e., twice the standard deviation) of the test values ​​for the three different test particles in a is 2SD = 3.78‰. However, as the test depth increases and the test time extends, the oxygen isotope measurements of different crystal planes gradually become consistent, and the measurement accuracy improves significantly. If the test is increased to 2000 cycles with a test time of 76 minutes, the accuracy will decrease to 2SD = 0.58‰.

[0098] like Figure 2As shown in Figure a, the horizontal axis represents the number of measurement cycles, a total of 2000 cycles, with each cycle lasting 2 seconds. The vertical axis represents the change in the rutile oxygen isotope ratio, expressed as twice the inter-group standard deviation, or 2SD. It can be seen that the change in the rutile oxygen isotope ratio decreases with increasing time (i.e., the number of cycles). For example, the 2SD from the first to the fortieth cycle is 3.78‰. Figure 2 The first point of a. The 2SD from the 1961st to the 2000th cycle is 0.58‰, which is Figure 2 The last point of a.

[0099] like Figure 2 Figure b shows the relationship between the measured values ​​of rutile oxygen isotopes obtained using SIMS and the measurement depth. Since SIMS is a relative measurement method, experiments showed that at the same measurement depth, the measured values ​​of different rutile samples had a consistent instrument fractionation coefficient, which ranged from... Figure 2 In diagram b, the difference between the ordinates of the red and green curves is consistent. By cross-calibrating rutile standard particles with known oxygen isotope values ​​and rutile samples with unknown oxygen isotope values, the oxygen isotope values ​​of rutile samples can be accurately obtained, thus achieving high-accuracy measurement. This research provides a scientific basis for solving the measurement deviation caused by the orientation effect of rutile crystals and lays the foundation for calibration methods.

[0100] like Figure 2 As shown in figure b, the horizontal axis represents the number of measurement cycles, a total of 2000 cycles, with each cycle lasting 2 seconds. The vertical axis represents the measured value of the rutile oxygen isotope ratio, expressed as δ¹⁸. 18 O represents the value. The calculation method is as follows: using the Vienna Standard Mean Seawater (VSMOW); 18 O / 16 Normalization is performed on O = 0.0020052, using the following formula: Measured δ 18 O VSMOW =(( 18 O / 16 O)Measured value / 0.0020052-1)×1000. The figure shows two different rutile samples. The red curve represents the change of three NR201 measurements over time; the green curve represents the change of three NR202 measurements over time. The difference between the average of the three NR201 measurements and the three NR202 measurements remains constant over time. This indicates that the two samples have the same instrumental fractionation characteristics, meaning that the fractionation coefficient of rutile is the same 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 groups of rutile standard material particles with each known oxygen isotope value in each group includes:

[0102] The first mean of all particles at the same measurement depth was calculated from the first mean within the group and the first standard deviation within the group for each rutile standard material particle with a known oxygen isotope value.

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

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

[0105] In this first embodiment, the within-group first mean and within-group first standard deviation of the rutile standard material samples are calculated:

[0106] The first mean and first standard deviation within the group of the j-th particle in the ith group of the rutile standard reference sample NR201 are respectively denoted 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 values ​​are (1, 41, 81, ..., 1961).

[0109]

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

[0111] Then calculate the first average value and the first standard deviation between groups for all rutile standard material sample particles in the same group, i.e., at the same measurement depth.

[0112] The first mean between groups for group i is:

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

[0114] The first standard deviation between groups for 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 is less than or equal to 0.6‰, take the current value of i and proceed to the next step; otherwise, continue calculating until the condition is met. The range of i is 1-50.

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

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

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

[0120] In this first embodiment, the known value δ of the rutile standard material is... 18 O NR201 =6.80‰, Fractionation coefficient IMF: IMF = δ 18 O NR201 -AA NR201-gi In this first embodiment, the IMF value 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 a rutile sample by combining the fractionation coefficient of the detection instrument includes:

[0122] The second mean of all particles at the same measurement depth was calculated from the second mean within the group and the second standard deviation within the group for each rutile sample with an unknown oxygen isotope value.

[0123] In this first embodiment, the second mean and second standard deviation within the group of the rutile sample (NR202) with unknown oxygen isotope values ​​are calculated:

[0124] The second mean and second standard deviation within the group of the j-th particle in the i-th group of the rutile sample NR202 with unknown oxygen isotope values ​​are denoted 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 values ​​are (1, 41, 81, ..., 1961).

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

[0128]

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

[0130] Then calculate the second average value of all rutile standard material sample particles in the same group, i.e., at the same measurement depth.

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

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

[0133] In this first embodiment, the second average value between groups for rutile sample NR202 was -59.72‰.

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

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

[0136] In this first embodiment, 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 first embodiment, the oxygen isotope value of the rutile sample with an unknown oxygen isotope value is -1.40‰.

[0138] In conjunction with this embodiment, there is also a preferred implementation scheme, in which at least one glass standard with a known oxygen isotope value, at least one rutile standard 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, the sample target surface contains multiple rutile standard material NR201, multiple test samples NR202, and multiple glass standard material Nist610.

[0140] In conjunction with this embodiment, there is also a preferred implementation scheme. Specifically, double-sided tape is applied to a glass slide, 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 attached to the double-sided tape.

[0141] In this first embodiment, a target is first made, which contains a glass standard substance, a rutile standard substance and a rutile sample to be tested.

[0142] Since the stability of the instrument requires a standard material with known oxygen isotope results for monitoring, the glass standard material NIST 610, developed by the National Institute of Standards and Technology (NIST), was chosen. 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 similar composition to the sample to be tested is required as a standard. Therefore, rutile, whose peroxy isotope has been tested using conventional methods, was selected as the standard. In this example, a rutile NR201 sample from the Kinyanfumbe region of Zambia was selected. The oxygen isotope value of this sample obtained using conventional methods is δ0. 18 O NR201 =6.80±0.18‰. Here, NR201 is used as the standard to determine the testing time range and sampling interval of rutile, and the method is established by calculating the instrument's fractionation coefficient. A rutile NR202 sample from the Graves Mountains in the United States was selected as the test sample. The oxygen isotope of this rutile sample has been determined using conventional methods to be: δ 18 O NR202 = -1.98 ± 0.34‰. A rutile sample NR202 with a known oxygen isotope value was used as the sample to test this method.

[0144] The specific process for making the target is as follows: 10cm*5cm double-sided tape is attached to a 10cm*10cm glass slide. 10-12 glass standard materials Nist610 with a particle size of 100-250 micrometers, 10-12 rutile standard materials NR201 with a particle size of 100-250 micrometers, and 10-12 test samples NR202 with a particle size of 100-250 micrometers are attached to a circle with a diameter of 1 cm on the double-sided tape. Epoxy resin and a coagulant are mixed. A smooth, 1-inch inner diameter polyethylene hollow column is placed vertically on the double-sided adhesive. The sample containing glass and rutile particles is placed in the middle of the polyethylene hollow column. The mixture of epoxy resin and coagulant, after vacuuming, is slowly injected along the inner surface of the polyethylene hollow column. Vacuuming is repeated, and the mixture is allowed to solidify. The polyethylene hollow column is then removed, and the double-sided adhesive is peeled off, resulting in a solidified rutile mineral standard sheet that can be extracted from the polyethylene hollow column. The rutile target is then polished using fine sandpaper and a polishing pad until the glass standard Nist610, the rutile standard NR201, and the sample NR202 are all exposed on one side of the target, and the entire surface is smooth and clean. The prepared target is shown below. Figure 3 As shown. Figure 3 'a' represents the overall image, which is circular in shape. Figure 3 b represents the surface morphology. Figure 3 b is Figure 3 A distribution map of the sample target surface magnified 50 times.

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

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

[0147] Using a Q150TE gold plating instrument from Quorum, a continuous gold film was deposited on the exposed side of the cleaned circular sample target. To ensure good conductivity of the sample, the plating thickness was 20nm-50nm, for example, it could be 20nm or only 45nm.

[0148] The signal required to measure rutile oxygen isotopes using a secondary ion mass spectrometer is as follows: 133 Cs + The ion source focuses the ion beam onto the glass or rutile sample target, with a beam spot area of ​​20 μm. 2 This is done to excite the sample to generate secondary ions. Subsequently, the sample releases secondary ions. 16 O and 18O passes through electric and magnetic fields sequentially, eventually reaching the ion signal detection system. Oxygen isotopes of rutile standard material are collected. 18 O and 16 The instrument signal of O was collected, and its oxygen isotope ratio data were calculated using the Vienna Standard Mean Seawater (VSMOW). 18 O / 16 Normalization is performed on O = 0.0020052, using the following formula: Measured δ 18 O VSMOW =(( 18 O / 16 O)Measured value / 0.0020052-1)×1000. During the detection process, two Faraday cups are used to simultaneously receive secondary ion signals. Each test round consists 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 within the protection scope of the present invention.

Claims

1. A method for testing and calibrating rutile oxygen isotopes, characterized in that, The methods include: Stability tests were conducted on the detection instrument using glass standard materials with known oxygen isotope values. After the stability test is passed, the detection instrument performs multiple sets of measurements on the crystal plane 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 for each rutile standard material particle with a known oxygen isotope value in the same group, i.e., at the same measurement depth, is obtained. Once the first standard deviation between groups meets the first preset threshold, the fractionation coefficient of the detection instrument is calculated by subtracting the first average value between groups that meets the sampling range test from the known oxygen isotope value of the rutile standard material. The detection instrument also measures the crystal planes of rutile sample particles with unknown oxygen isotope values. The measurement depth is consistent with the measurement depth of rutile standard material particles with known oxygen isotope values ​​in the same group, and the second average value between groups of the i-th group is obtained. The oxygen isotope value of the unknown rutile sample is obtained by adding the fractionation coefficient of the detection instrument to the second average value between groups.

2. The method for testing and calibrating rutile oxygen isotopes as described in claim 1, characterized in that, The method for testing the stability of the detection instrument using glass standard materials with known oxygen isotope values ​​includes: The instrument signal of no less than three glass standard substances is collected using the aforementioned detection instrument to obtain the oxygen isotope value of each glass standard substance. Calculate the range of oxygen isotope values ​​for all the aforementioned glass standard materials. 玻璃 ; If the distribution range Range 玻璃 <1‰ indicates that the testing instrument has passed the stability test.

3. The method for testing and calibrating rutile oxygen isotopes as described in claim 1, characterized in that, The method for the detection instrument to perform multiple sets of measurements on the crystal facets of rutile standard material particles with known oxygen isotope values ​​includes: The crystal planes of two or more particles of rutile standard material with known oxygen isotope values ​​are measured.

4. The method for testing and calibrating rutile oxygen isotopes as described in claim 1, characterized in that, The method for obtaining the first standard deviation between groups of rutile standard material particles with each known oxygen isotope value at the same measurement depth includes: The first mean of all particles at the same measurement depth is calculated from the first mean within the group and the first standard deviation within the group for each rutile standard material particle with a known oxygen isotope value. The first standard deviation (SD) between groups is calculated from the first mean between groups. 已知 ; If the first standard deviation between groups SD 已知 Meets 2SD 已知 <First preset threshold indicates 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 as described in claim 1, characterized in that, The method for obtaining the second inter-group average of the i-th group includes: The second mean of all particles at the same measurement depth was calculated from the second mean within the group and the second standard deviation within the group for each rutile sample with an unknown oxygen isotope value.

6. The method for testing and calibrating rutile oxygen isotopes as described in claim 1, characterized in that, At least one glass reference material with a known oxygen isotope value, at least one rutile reference 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.

7. The method for testing and calibrating rutile oxygen isotopes as described in claim 6, characterized in that, The method further includes: Double-sided tape is applied to a glass slide, 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 then attached to the double-sided tape.

8. The method for testing and calibrating rutile oxygen isotopes as described in claim 6, characterized in that, The method for measuring oxygen isotope values ​​in the aforementioned method is as follows: use 133 Cs + The ion source focuses the ion beam onto the analyte, with a beam size of 20 μm. 2 To excite the analyte to generate secondary ions; Secondary ions released by the analyte pass through an electric field and a magnetic field in sequence before finally reaching the ion signal detection system.

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