An electron probe analysis method for testing trace elements in extraterrestrial zircon

Abstract

The present invention provides an electron probe analysis method for testing trace elements in extraterrestrial zircon, including: S1, selecting zircon standard samples; S2, verifying the composition homogeneity of zircon standard samples and selecting monitoring standard samples; S3, comparing the electron probe test results of the trace element content in the monitoring standard samples with the LA-ICP-MS test results, adjusting and optimizing and determining the test conditions for the electron probe test of trace elements in extraterrestrial zircon; S4, using the test conditions determined in S3 to test the trace element content in extraterrestrial zircon. The present invention innovatively reduces the element detection limit and improves the analysis accuracy of trace elements, highlighting the advantages of high spatial resolution and non-destructive analysis of electron probe analysis technology. The present invention can not only test the trace elements of zircon in Chang'e VI anorthosite with high precision, but also can be applied to the main trace element analysis of fine-grained zircon in Earth, Mars and meteorite samples.

Description

Technical Field

[0001] The invention belongs to the technical field of earth and planetary science analysis and testing, and in particular relates to an electron probe analysis method for testing trace elements in extraterrestrial zircon. Background Art

[0002] The study of lunar samples is the most important means to reveal the history of the formation and evolution of the moon. Prior to this, there were ten lunar sampling operations in human history, including six Apollo missions, three Lunar missions and the Chang'e-5 mission, which collected a total of 382.98 kg of lunar samples. These samples have greatly improved our understanding of the formation and evolution of the moon, such as large impact events, magma ocean models, and processes such as volcanic activity and thermal evolution. However, these ten samplings were all located on the front side of the moon. The lack of samples on the back side of the moon has prevented us from fully understanding the diversity of lunar geological characteristics, especially the lack of highland anorthosite samples on the back side of the moon that represent the initial lunar crust. On June 25, 2024, Chang'e-6 successfully collected 1935.3 grams of lunar soil samples in the South Pole-Aitken Basin on the back side of the moon, opening a new era of lunar scientific research. At the same time, the plagioclase samples on the back side of the moon provide new ideas and insights for revealing the composition of the lower lunar crust and upper mantle of the moon.

[0003] Zircon is the most important accessory mineral in geological research. It is widely distributed and has stable physical and chemical properties. It records a series of information such as the age of crystallization, temperature, oxygen fugacity, magma source area, and magma evolution process. It is widely used in the study of earth and planetary sciences. However, due to the characteristics of zircon particles in lunar samples being few and small (usually < 10μm), the beam spot of conventional in-situ trace element analysis methods such as secondary ion microprobe (SIMS) or laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) is generally larger than 15μm, which cannot meet the testing requirements of its spatial resolution. Therefore, the content of major and trace elements (Al, Ti, P, Zr, Hf, Yb, Y) in zircon in lunar samples and their research significance are rarely reported.

[0004] Electron probe has the advantages of high spatial resolution (~ 1μ), non-destructiveness, and high instrument penetration rate, and is widely used in the frontier fields of earth and planetary science. However, this method is usually used to test the major elements of minerals. The ability to analyze trace elements (<0.1wt.%) depends largely on the setting of experimental conditions, including important indicators such as reducing the detection limit of elements and improving the accuracy of analysis. With the development of large analytical crystals (LLIF, LPET, etc.), analysis and correction software, and the research and development of major and trace standard materials, high-precision trace element analysis by electron probe has been achieved to a certain extent, such as the key trace element analysis of minerals such as quartz, rutile, olivine and spinel.

[0005] So far, no electron probe analysis method for elements such as Al, Ti, P, Hf, Yb, and Y in zircon has been reported. The main reasons are as follows: (1) Most zircons are rare earth elements, which excite complex characteristic X-ray lines and cause serious interference between the peak positions of the elements, resulting in poor analysis accuracy. (2) The zircon particles in planetary samples are small (< 10 μm) and are mainly found in silicate minerals. Elements such as Al, Ti, and P in zircon are easily affected by the secondary fluorescence effect of the host minerals. (3) Currently, zircon standards at home and abroad are all isotope standards such as U-Pb-Hf-O and rare earth element standards. There is a lack of homogeneity verification for elements such as Al, Ti, and P, which makes it impossible to estimate the error of electron probe trace element analysis. (4) Lunar soil samples are extremely precious. How to balance the detection limit, analysis accuracy, and test efficiency without damaging the precious lunar soil samples is also a major difficulty in zircon trace element analysis.

[0006] In summary, the study of zircon trace elements in lunar samples has important scientific research significance, and it is imperative to detect zircon trace elements in lunar samples through electron probe analysis technology. Summary of the invention

[0007] In view of this, the present invention aims to propose an electron probe high-precision analysis method for testing the trace elements such as Al, Ti, P, Hf, Yb, and Y in zircons in the Chang'e-6 samples. This method aims to solve the problems of low spatial resolution and damage to lunar soil samples in conventional in-situ trace element analysis methods (LA-ICP-MS), as the zircons in the Chang'e-6 plagioclase samples are small and precious, thereby solving the problems of low spatial resolution and damage to lunar soil samples in conventional in-situ trace element analysis methods (LA-ICP-MS). This method can accurately test the trace elements of zircons in the Chang'e-6 plagioclase samples without damaging the lunar soil samples.

[0008] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0009] The present invention provides an electron probe analysis method for testing trace elements in extraterrestrial zircon, comprising the following steps:

[0010] S1: Select a zircon standard sample, wherein the zircon standard sample is a U-Pb-Hf-O isotope standard sample;

[0011] S2: Verify the composition homogeneity of zircon standard samples, calculate the average value, standard deviation and relative standard deviation of the trace elements of each zircon standard sample, and use the zircon standard sample with a relative standard deviation value of <20% as the trace element monitoring standard sample of the electron probe; the trace elements are Al, Ti, P, Hf, Yb and Y;

[0012] S3: Use an electron probe to perform a spectral scan of trace elements on the monitoring standard sample, test the content of trace elements in the monitoring standard sample, and compare it with the corresponding trace element content obtained by testing the monitoring standard sample through laser ablation-inductively coupled plasma mass spectrometry, and adjust and optimize the electron probe test conditions according to the comparison result, until the analysis error between the electron probe test result of the trace element content in the monitoring standard sample and the laser ablation-inductively coupled plasma mass spectrometry test result is ≤20%, thereby determining the test conditions for the electron probe test of trace elements in extraterrestrial zircon; the test conditions include acceleration voltage, beam current, front and back background values, peak analysis time, background value analysis time, calibration standard sample, and background model;

[0013] S4: Using the test conditions determined in S3, an electron probe spectrum scan is performed on the trace elements in the extraterrestrial zircon to test the content of the trace elements in the extraterrestrial zircon.

[0014] Furthermore, laser ablation-inductively coupled plasma mass spectrometry was used to verify the composition homogeneity of the zircon standard sample.

[0015] Furthermore, the monitoring standard sample for Al is Qinghu zircon, the monitoring standard sample for Ti is Qinghu zircon, the monitoring standard sample for P is GJ-1 or Tanz zircon, the monitoring standard sample for Hf is Qinghu, GJ-1 or Tanz zircon, the monitoring standard sample for Yb is GJ-1 zircon, and the monitoring standard sample for Y is GJ-1 zircon.

[0016] Furthermore, the calibration standard for Al and Y is Y3Al5O 12 The calibration standard for Ti is rutile, the calibration standard for P is apatite, the calibration standard for Hf is pure Hf metal, and the calibration standard for Yb is rare earth element synthetic glass with a Yb content of 10.54 wt.%.

[0017] Furthermore, according to the characteristic X-ray properties of each trace element, a characteristic X-ray line system with high intensity and less interference is selected, among which Si, Al, Ti, and P are the Kα line system, and Zr, Hf, Yb, and Y are the Lα line system.

[0018] Furthermore, in order to reduce the interference of secondary fluorescence effect, the acceleration voltage of trace element analysis was set to 20 kV.

[0019] Furthermore, appropriate measuring currents are selected according to the different trace elements to be measured. The beam current for testing Hf is set to 40 nA, and the beam current for testing Al, Ti, P, Yb and Y is set to 500 nA.

[0020] Furthermore, the double crystal enhanced mode was used to analyze the trace elements Al and Y, the LLIF crystal was used as the spectroscopic crystal to test Hf and Yb, and the LPET crystal was used as the spectroscopic crystal to test P and Ti.

[0021] Furthermore, the peak analysis time for testing Hf was set to 30 s, and the background value analysis time was set to 15 s; the peak analysis time for testing Al, Ti, P, Yb, and Y was set to 240 s, and the background value analysis time was set to 60 s.

[0022] Furthermore, the before and after background values ​​of test P were (None, +300), the before and after background values ​​of test Yb were (-530, +600), the before and after background values ​​of test Ti were (-750, +450), the before and after background values ​​of test Y were (Sp1 -300, None) (Sp4 -200, None), the before and after background values ​​of test Al were (Sp1 -600, +450) (Sp4 -550, +500), and the before and after background values ​​of test Hf were (-600, +650).

[0023] Furthermore, the method also includes step S5: step S4 tests the content of trace elements in extraterrestrial zircon. If the test result of the trace element content is abnormal, continue to adjust and optimize the electron probe test conditions until the trace element content in the extraterrestrial zircon is tested normally.

[0024] The analysis method of the present invention is based on the principle of electron probe. By comparing the electron probe of trace elements in zircon monitoring standard samples with the LA-ICP-MS analysis results, the electron probe test conditions such as acceleration voltage, beam current, front and back background values, peak analysis time, background value analysis time, calibration standard sample, background model, etc. are optimized to achieve the best test effect, thereby solving the problem of high-precision determination of Al, Ti, P, Hf, Yb, Y and other trace elements in zircon in Chang'e 6 anorthosite by electron probe. Compared with the prior art, the electron probe analysis method for testing trace elements in extraterrestrial zircon provided by the present invention has the following advantages:

[0025] (1) The present invention not only effectively reduces the element detection limit, but also significantly improves the analysis accuracy of trace elements, greatly highlighting the advantages of high spatial resolution (micrometer level) and non-destructive analysis of electron probe analysis technology;

[0026] (2) The electron probe analysis method of the present invention can accurately test the trace elements of zircon in the Chang'e-6 anorthosite sample, identify the element distribution and occurrence state, and provide important technical support for studying the formation temperature of the lunar crust, the magma evolution process, and the composition of the lunar crust.

[0027] (3) Based on the zircon isotope and rare earth element standards used by predecessors, the present invention verifies and calibrates key indicator elements such as Al, Ti, and P in zircon. By continuously optimizing the analysis method, the analysis accuracy of electron probe testing of zircon trace elements is effectively improved;

[0028] (4) The present invention can not only analyze the trace elements such as Al, Ti, P, Hf, Yb, and Y in zircon in the Chang'e-6 anorthosite, but can also be applied to the analysis of major and trace elements in fine-grained (<10 μm) zircon in Earth, Mars, and meteorite samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The features and advantages of the present invention may be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0030] Figure 1 This is a backscattered photo of Chang'e 6's anorthosite. Figure 1 a in the middle is plagioclase (PI), Figure 1 b is Figure 1 A partial magnified image of zircon (Zrn) in middle a;

[0031] Figure 2 This is a comparison chart of the electron probe background setting and test results of Ti and P in zircon. Figure 2 a in the middle is the Ti element spectrum of Qinghu zircon. Figure 2 Figure b is the Ti element spectrum of zircon in the Chang'e 6 anorthosite. Figure 2 Figure c is the P element spectrum of GJ-1 zircon at 20kV and 200nA. Figure 2 Figure d is the P element spectrum of GJ-1 zircon at 20kV and 500nA. Figure 2 The middle e is the Ti content distribution diagram of Qinghu zircon tested at different test points. Figure 2 Middle f is the P content distribution diagram of GJ-1 zircon tested at different test points;

[0032] Figure 3 This is a comparison chart of the electron probe background setting and test results of Al and Y in zircon. Figure 3 a in the middle is the Al element spectrum of Qinghu zircon. Figure 3 Figure b is the Al element spectrum of zircon in the Chang'e 6 anorthosite. Figure 3 Figure c is the Y element spectrum of GJ-1 zircon at 20kV and 200nA. Figure 3 Figure d is the Y element spectrum of GJ-1 zircon at 20kV and 500nA. Figure 3 The middle e is the Al content distribution diagram of Qinghu zircon tested at different test points. Figure 3 f in the figure is the Y content distribution diagram of GJ-1 zircon tested at different test points;

[0033] Figure 4 This is a comparison chart of the electron probe background settings and test results of Hf and Yb in zircon. Figure 4 a in the figure is the Hf element spectrum of Tanz zircon. Figure 4b is the Yb element spectrum of GJ-1 zircon. Figure 4 The middle c is the Hf content distribution diagram of Qinghu, GJ-1 and Tanz zircon tested at different test points. Figure 4 d in the figure is the Yb content distribution diagram of GJ-1 zircon tested at different test points;

[0034] Figure 5 This is a comparison chart of the results of high-precision determination of six trace elements, Hf, P, Y, Yb, Ti, and Al in three types of zircons, Qinghu, GJ-1, and Tanz, by LA-ICP-MS and electron probe. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0036] Figure 1 This is a backscattered photo of Chang'e 6's anorthosite. Figure 1 a in the middle is plagioclase, Figure 1 b is Figure 1 A partial enlarged image of zircon (Zrn) in a. As described in the background technology, lunar soil samples are extremely precious. How to achieve a balance between detection limit, analysis accuracy and test efficiency without damaging the precious lunar soil samples is an important reason why it is difficult to measure the trace elements of zircon in the Chang'e 6 anorthosite with high precision.

[0037] To solve the above problems, the present invention provides an electron probe analysis method for testing Al, Ti, P, Hf, Yb and Y trace elements in extraterrestrial zircon, comprising the following steps:

[0038] S1: Select a zircon standard sample, wherein the zircon standard sample is a U-Pb-Hf-O isotope standard sample;

[0039] S2: Verify the composition homogeneity of zircon standard samples, calculate the average value, standard deviation and relative standard deviation of the trace elements of each zircon standard sample, and use the zircon standard sample with a relative standard deviation value of <20% as the trace element monitoring standard sample of the electron probe; the trace elements are Al, Ti, P, Hf, Yb and Y;

[0040] S3: Use an electron probe to perform spectral scanning of each trace element on the monitoring standard sample, test the content of trace elements in the monitoring standard sample, and compare it with the corresponding trace element content obtained by testing the monitoring standard sample through laser ablation-inductively coupled plasma mass spectrometry, and adjust and optimize the electron probe test conditions according to the comparison result, until the analysis error between the electron probe test result of the trace element content in the monitoring standard sample and the laser ablation-inductively coupled plasma mass spectrometry test result is ≤20%, thereby determining the test conditions for the electron probe test of trace elements in extraterrestrial zircon; the test conditions include acceleration voltage, beam current, front and back background values, peak analysis time, background value analysis time, calibration standard sample, and background model;

[0041] S4: Using the test conditions determined in S3, an electron probe spectrum scan is performed on the trace elements in the extraterrestrial zircon to test the content of the trace elements in the extraterrestrial zircon;

[0042] S5: Step S4 tests the content of trace elements in extraterrestrial zircon. If the test result of the trace element content is abnormal, continue to adjust and optimize the electron probe test conditions until the content of trace elements in extraterrestrial zircon is tested normally.

[0043] When selecting zircon standards, since the detection limit of the electron probe is usually as low as about 10 ppm, the trace element content of the selected zircon should be as high as possible to meet the content requirements of the electron probe trace element test. Therefore, it is necessary to select zircon trace element standards suitable for electron probe.

[0044] Without detailed trace element homogeneity verification, the present invention collected six existing zircon standards from Qinghu, Penglai, GJ-1, Tanz, 91500, and PLE, all of which are U-Pb-Hf-O isotope standards. LA-ICP-MS was used to verify the composition homogeneity of zircon standards from Qinghu, Penglai, GJ-1, Tanz, 91500, and PLE, and one composition profile was analyzed for each sample, for a total of ten points. The mean value, standard deviation, and relative standard deviation of the trace elements of each standard sample were calculated, and elements with a relative standard deviation of <20% were generally considered to be uniform in composition.

[0045] The results of component homogeneity verification show that the elements Si, Zr, Al, Ti, P, Hf, Yb, Y, Th and U in Qinghu, GJ-1, Tanz and 91500 zircons are relatively uniform, as shown in Table 1. The content of some elements is low, such as Al in GJ-1, 91500 and Tanz zircons is less than 12 ppm, but the Al content in Qinghu zircon is 73.9 ppm. Therefore, Qinghu zircon can be used as a monitoring standard for Al element electron probe analysis. In addition, the relative standard deviation of trace elements in some zircons exceeds 20%, but ≤30%, which can be used as reference values ​​when necessary, such as Ti in Qinghu zircon.

[0046] Steps S1 and S2 of the present invention are the collection and determination process of zircon trace element monitoring standard samples. Finally, the present invention selects Qinghu zircon as the monitoring standard sample for Al, Qinghu zircon as the monitoring standard sample for Ti, GJ-1 or Tanz zircon as the monitoring standard sample for P, Qinghu, GJ-1 or Tanz zircon as the monitoring standard sample for Hf, GJ-1 zircon as the monitoring standard sample for Yb, and GJ-1 zircon as the monitoring standard sample for Y.

[0047] The present invention selects suitable calibration standards (internal standards), Al and Y: Y3Al5O 12 ; Ti: rutile; P: apatite; Hf: pure Hf metal; Yb: rare earth element synthetic glass with Yb content of 10.54 wt.%.

[0048] According to the characteristic X-ray properties of each element, a characteristic X-ray line system with high intensity and less interference is selected. In this embodiment, Al, Ti and P are selected as the Kα line system, and Hf, Yb and Y are selected as the Lα line system.

[0049] Since the zircon particles in the Chang'e-6 anorthosite are relatively small, in order to avoid interference from the secondary fluorescence effect (mainly affected by voltage), the present invention does not use the 25 kV commonly used in trace element analysis, but uses 20 kV.

[0050] Since the content of Zr, Hf and Si in zircon is relatively high, low current (40 nA) can meet their analysis requirements; while other trace elements with low content are detected by high beam current (500 nA) to effectively reduce the element detection limit. In the present invention, the beam current for measuring Hf is set to 40 nA, which is the current for single-point analysis of Hf element; the beam current for measuring Al, Ti, P, Yb and Y is set to 500 nA.

[0051] Selecting a spectrometer and a spectroscopic crystal. In the present invention, two TAP crystals are used to test Al (Kα) and Y (Lα), one PET crystal is used to test Zr (Lα), one LLIF crystal is used to test Hf and Yb, and one LPET crystal is used to test P and Ti (Kα).

[0052] In order to reduce the element detection limit and improve the analysis accuracy, the present invention innovatively uses multiple means to achieve this. In the present invention, the double crystal enhanced mode is used to analyze trace elements, such as Al and Y; the peak analysis time of the trace elements Al, Ti, P, Yb and Y is extended to 240 s; and large crystals such as LLIF and LPET are used to enhance the counting intensity.

[0053] In order to balance the element detection limit and single-point analysis efficiency, the present invention changes the traditional background value analysis time (usually half of the peak analysis time). In the present invention, the background value analysis time for testing Al, Ti, P, Yb and Y is set to 60s, which is only 1 / 4 of the peak time, improving the analysis efficiency while ensuring the detection limit of the test element. The peak analysis time for testing Hf is set to 30s, and the background value analysis time is set to 15s. The calculation formulas for the element detection limit and analysis accuracy are as follows:

[0054]

[0055]

[0056] DL is the detection limit, SD is the analytical precision, i is the element, P is the peak intensity (cps / μA), B is the background intensity (cps / μA), PC is the beam current, t is the analysis time, UNK represents the unknown sample, STD represents the standard sample of element i, and C represents the content.

[0057] In the present invention, under the conditions of 20 kV and 500 nA, the peak analysis time of Al, Ti, P, Yb and Y is 240 s, the background time is 60 s, the detection limit is 12-67 ppm (3σ), and the analysis accuracy is 10-52 ppm, see Table 2 for details.

[0058] Since zircon in Chang'e-6 anorthosite is relatively scarce and the particles are small (< 10 μm), in order to avoid damage caused by multiple analyses, the electron probe trace element analysis mainly performs spectral scanning and accuracy verification on three zircon monitoring standards. In order to improve the accuracy of trace element analysis, high-precision spectral scanning and accurate setting of front and back background values ​​are performed on the trace elements with high content in the three zircon monitoring standards.

[0059] Step S3 of the present invention determines the test conditions (voltage, beam current, and analysis time) for electron probe testing of zircon trace elements in Chang'e 6 anorthosite, thereby effectively reducing the trace element detection limit and improving the accuracy of trace element analysis.

[0060] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0061] Example 1 Determination of Ti element

[0062] The Qinghu zircon has the highest Ti content, with the LA-ICP-MS analysis result of 66.8 ppm, which is more suitable as a monitoring standard sample for the Ti element.

[0063] First, the electron probe Ti element spectrum analysis of Qinghu was carried out, such as Figure 2 As shown in a, the accelerating voltage is 20 kV, the analytical beam current is 200 nA, and the conventional front and back background Analytical Conditions (AC1: -500, +500) are used. Figure 2 The test results shown in e show that the Ti content is consistently low.

[0064] The background values ​​before and after several changes, such as (AC2: -400, +1000), (AC3: -400, +900), (AC4: -400, +800), (AC5: -900, +830), (AC6: -600, +800), (AC7: -650, +650), Figure 2 As shown in Figure e, the test results have improved, but the Ti content is still low.

[0065] Therefore, if Figure 2 The background mode change method shown in a still uses the background value (-650, +650), and changes from linear regression to exponential regression. Figure 2 The test results of medium e (AC8: -650, +650) show that the change is significant. This background value was used to test the zircon in the Chang'e 6 anorthosite. However, the test results showed a negative Ti content, indicating that this background value is not suitable for testing the Ti element.

[0066] like Figure 2 As shown in b, on the zircon in the Chang'e 6 anorthosite, the electron probe Ti element fine spectrum scan was performed using 20 kV and 500 nA. The result showed that there was a bulge at (AC9: -650, +650), making its background value higher than the peak value, resulting in the test results as shown in Figure 2 The value shown in e is negative. Re-adjust the background before and after (AC10: -750, +550). Figure 2 The Ti content of zircon in the Chang'e 6 anorthosite test result is normal ( Figure 2 (e) The purple solid circle in the figure determines the Ti element testing conditions of zircon in the Chang'e-6 anorthosite.

[0067] To verify the accuracy, the Ti element in Qinghu zircon was tested again using the background before and after (AC10: -750, +550). Figure 2 The test result in Figure e shows 77.2 ppm ( Figure 2 e (blue solid square), the analytical error is 3.5%.

[0068] Example 2 Determination of P element

[0069] LA-ICP-MS analysis showed that the P contents in GJ-1 and Tanz zircons were 182.6±5.3 ppm and 212.1±3.9 ppm, respectively, and both can be used as monitoring standards for the P element in zircon.

[0070] First, if Figure 2 As shown in Figure c, the P element in GJ-1 zircon was tested using an electron probe under a conventional background (AC1: -800, +800). Figure 2 The value shown in f is a negative value. After adjusting the background (AC2: -800, +1000), the P element content is still negative.

[0071] Using GJ-1 zircon, scanning at 20kV, 200nA, expanding the left background and adjusting the right background (AC3: -2000, +1400), (AC4: -2000, +1100), (AC5: -1900, +800), Figure 2 The test result shown in middle f becomes positive, but the content value is too high and is still interfered by the left background of Zr.

[0072] Therefore, we changed the background to the right (AC6: None, +800), and the test results are as follows Figure 2 The value f in the middle is too low, indicating that the background value is still inappropriate. The test results under the background (AC7: None, +600) and (AC8: None, +400) are too high, indicating that the 200nA spectrum scan may not be fine enough.

[0073] like Figure 2 As shown in Figure d, under the conditions of 20 kV and 500 nA, the P peak of GJ-1 zircon was clearly seen. Figure 2 The P content of the background (AC9: None, +400) shown in f is still slightly high. Figure 2 As shown in f, the test results are consistent with the standard values, thereby determining the P element test conditions of zircon in the Chang'e-6 plagioclase.

[0074] After testing the P element of zircon in the Chang'e-6 plagioclase, the P element of GJ-1 zircon was tested again. The results were consistent with the previous ones, with an average value of 183.2 ppm and an analytical error of 0.33%.

[0075] Example 3 Determination of Al element

[0076] According to LA-ICP-MS analysis, the Al content in Qinghu zircon is 73.9±19.6 ppm, which can be used as a monitoring standard for Al element in zircon.

[0077] In order to obtain more accurate electron probe test results, a double TAP crystal was used to test the Al element with a beam current of 200 nA. Figure 3 As shown in a, the internal standard of conventional Al element is Al2O3, and the conventional front and back background (AC1: Sp1 -1800, +1000) (AC1: Sp4 -1800, +1000) is used for scanning. The test results are as follows Figure 3 As shown in Figure e, the Al content is low. After three background adjustments (AC2: Sp1 -300, +900) (AC2: Sp4 -600, +800), (AC3: Sp1 -700, +900) (AC3: Sp4 -700, +1000), (AC4: Sp1 -300, +900) (AC4: Sp4 -600, +800), as shown in Figure e. Figure 3 As shown in Figure e, the test result is still low.

[0078] The strategy of replacing the internal standard was adopted, and Al2O3 was changed to YAG_8. Under the conditions of background 5 (AC5: Sp1 -300, +900) (AC5: Sp4 -600, +800), as shown in Figure 3 As shown in Figure e, the Al content in the test results has increased, but it is still not enough. Re-adjust the background before and after (AC6: Sp1 -250, +450) (AC6: Sp4 -150, +350), as shown in Figure e. Figure 3 As shown in (e), the test results are consistent with the Al content in Qinghu Lake.

[0079] The Al content of zircon in Chang'e 6 anorthosite was tested using the following conditions (AC7: Sp1 -250, +450) (AC7: Sp4 -150, +350). Figure 3 The result shown in e is a negative value, indicating that the background of this element is still not suitable. Figure 3 As shown in b, a detailed spectral scan of the Al content of zircon in the Chang'e 6 anorthosite using a beam current of 500nA shows obvious peaks, which is conducive to the setting of the background before and after. The background was readjusted (AC8: Sp1 -600, +450) (AC8: Sp4 -550, +500), and the Al content of the tested Qinghu zircon was consistent with the standard value (see Figure 3 AC8 short line in middle e), thus determining the Al element testing conditions of zircon in Chang'e 6 anorthosite.

[0080] After testing the Al content of zircon in Chang'e 6 anorthosite, we tested the Qinghu zircon again, and the results were consistent (see Figure 3AC8 (green long line in e-zone) has an average value of 79.4 ppm and an analytical error of 7.46%.

[0081] Example 4 Determination of element Y

[0082] LA-ICP-MS analysis showed that the Y content in GJ-1 zircon was 268.2±0.95 ppm, which can be used as a monitoring standard for the Y element in zircon.

[0083] Large crystals have higher resolution, and LPET large crystals are used to analyze the Y element. First, the Y element electron probe spectrum analysis was performed on GJ-1 zircon, such as Figure 3 As shown in c, the acceleration voltage is 20 kV, the analysis beam current is 200 nA, and the conventional front and back background (AC1: -500, +500) is used. Figure 3 Figure f shows that the test results show that the Y content is consistently low.

[0084] After the following background debugging (AC2: -1000, +500) and (AC3: -1400, +500), such as Figure 3 As shown in f, the test result is still low. This may be because although LPET has high resolution, the counting intensity of the Y element is too low. Therefore, two TAP crystals were tried to analyze the Y element under the conditions of (AC4: Sp1 -500, +900) (AC4: Sp4 -500, +900) and (AC5: Sp1 -500, +200) (AC5: Sp4 -500, +200). Figure 3 The test result in f is negative. This is because both sides are interfered by ZrLa and ZrLn, resulting in a background value that is too high and exceeds the peak value.

[0085] Therefore, if Figure 3 As shown in middle d, 500nA was used again to scan the Y peak position on GJ-1 zircon, and the peak position was obvious. Adjust the background (AC6: Sp1 -400, +200) (AC6: Sp4 -400, +200), Figure 3 The f in the middle shows that the test result is positive, but still low. After further adjustment (AC7: Sp1 -200, +200) (AC7: Sp4 -200, +200), the result is not improved.

[0086] Since the interference peaks on both sides are close, the left single background setting (AC8: Sp1 -300, None) (AC8: Sp4 -300, None) is used. The data is close, but still slightly lower. After further adjustment (AC9: Sp1 -300, None) (AC9: Sp4 -200, None), as shown in Figure 3As shown in middle f, the data is close to the standard value (see the long green line AC9), which determines the Y element testing conditions of zircon in the Chang'e 6 plagioclase.

[0087] After testing the Y element of zircon in the Chang'e-6 anorthosite, the Y element of GJ-1 zircon was reanalyzed, which was consistent with the previous results (see AC9 purple diamond), with an average value of 251.3 ppm and an analytical error of 6.30%.

[0088] Example 5 Determination of Hf Element

[0089] Since the content of Hf in zircon is relatively high, such as Figure 4 As shown in a, the electron probe spectrum was scanned using Tanz zircon at 20kV and 100nA. The 100nA current is the spectrum scanning current of Tanz zircon. The background before and after was determined to be (-600, 650), and ten points were taken for Qinghu, GJ-1 and Tanz zircon, respectively. Figure 4 Figure c shows that the Hf content of the test results is consistent within the error range (see Qinghu_S, GJ-1_S and Tanz_S). This determines the Hf element test conditions of zircon in Chang'e 6 anorthosite.

[0090] After testing the Hf content of zircon in Chang'e 6 plagioclase, the Qinghu, GJ-1 and Tanz zircon were scanned again, which was consistent with the previous data (see Qinghu_E, GJ-1_E and Tanz_E). The Hf content of Qinghu zircon is 1.27 wt.%, the average value of the test is 1.27 wt.%, and the analysis error is 0.30%; the Hf content of GJ-1 zircon is 0.74 wt.%, the average value of the test is 0.79 wt.%, and the analysis error is 5.78%; the Hf content of Tanz zircon is 1.34 wt.%, the average value of the test is 1.30wt.%, and the analysis error is 2.67%.

[0091] Example 6 Determination of Yb Element

[0092] LA-ICP-MS analysis showed that the Yb content in GJ-1 zircon was 63.1±0.55 ppm, which can be used as a monitoring standard for the Yb element in zircon.

[0093] First, the electron probe Yb element spectrum of GJ-1 zircon was analyzed. Figure 4 As shown in b, the acceleration voltage is 20 kV, the analysis beam current is 200 nA, and the conventional front and back background (AC1: -500, +700) is used. Figure 4The test results in Figure d show that the Yb content is consistently low. After several background adjustments (AC2: -700, +1000), (AC3: -700, +1500), (AC4: -700, +2000), (AC5: -500, +2000), (AC6: -500, +1600), Figure 4 The test value in middle d is still significantly low.

[0094] Re-scan the Yb peak on GJ-1 zircon at 500 nA and adjust the background (AC7: Sp1 -250, +500). Figure 4 The test results in the middle d show a slight increase. Comparing the Yb element spectrum characteristics of zircon in GJ-1 and Chang'e 6 plagioclase, the background before and after is reset (AC8: Sp1 -530, +600), and the test results are improved (see Figure 4 AC8 short line in middle d), thus determining the Yb element testing conditions of zircon in Chang'e-6 anorthosite.

[0095] After testing the Yb element of zircon in Chang'e 6 anorthosite, the Yb element of GJ-1 zircon was retested, and the results were consistent with the previous results (see Figure 4 The average value of the Yb element is 44.1 ppm, and the analytical error is 30.0%. Although the Yb data tested by this method is relatively stable, it is lower than the LA value. It is speculated that the Yb element composition of GJ-1 zircon is not uniform.

[0096] The average values ​​and standard deviations of the elements Al, Ti, P, Hf, Yb, and Y of the three zircons of Qinghu, GJ-1, and Tanz were calculated, and then compared with their reference values ​​to obtain the analytical accuracy of the electron probe method of the present invention, see Table 3. Figure 5 It can be seen that the results show that the electron probe analysis method for testing trace elements in extraterrestrial zircon proposed in the present invention has high accuracy and stability.

[0097] Under the conditions of the present invention, zircon in the Chang'e 6 anorthosite was tested, and the data of each element are shown in Table 4. The trace element data of zircon in the anorthosite on the far side of the moon were obtained for the first time through the analysis method of the present invention, which has extremely important scientific significance for studying the formation temperature of the anorthosite, the magma evolution process and the composition of the lunar crust.

[0098] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations shall all fall within the scope defined by the appended claims.

[0099] Table 1 LA-ICP-MS data results of zircon monitoring standard samples

[0100] .

[0101] Table 2 Analysis conditions of trace elements in zircon from Chang'e 6 anorthosite by high-precision electron microprobe

[0102] Table 3 Results of high-precision electron probe determination of zircon monitoring standard sample data

[0103] Table 4 Results of high-precision electron microprobe determination of trace elements in zircon in Chang'e-6 anorthosite

[0104] .

Claims

1. An electron probe analysis method for testing trace elements in extraterrestrial zircon, characterized in that: The method comprises the following steps: S1: Select a zircon standard sample, wherein the zircon standard sample is a U-Pb-Hf-O isotope standard sample; S2: Verify the composition homogeneity of zircon standards, calculate the average value, standard deviation and relative standard deviation of trace elements of each zircon standard, and use zircon standards with relative standard deviation values ​​<20% as trace element monitoring standards for electron probe; the trace elements are Al, Ti, P, Hf, Yb and Y; wherein the monitoring standard for Al is Qinghu zircon, the monitoring standard for Ti is Qinghu zircon, the monitoring standard for P is GJ-1 or Tanz zircon, the monitoring standard for Hf is Qinghu, GJ-1 or Tanz zircon, the monitoring standard for Yb is GJ-1 zircon, and the monitoring standard for Y is GJ-1 zircon; S3: Use an electron probe to perform a spectral scan of trace elements on the monitoring standard sample, test the content of trace elements in the monitoring standard sample, and compare it with the corresponding trace element content obtained by testing the monitoring standard sample through laser ablation-inductively coupled plasma mass spectrometry, and adjust and optimize the electron probe test conditions according to the comparison result, until the analysis error between the electron probe test result of the trace element content in the monitoring standard sample and the laser ablation-inductively coupled plasma mass spectrometry test result is ≤20%, thereby determining the test conditions for the electron probe test of trace elements in extraterrestrial zircon; the test conditions include acceleration voltage, beam current, front and back background values, peak analysis time, background value analysis time, calibration standard sample, and background model; S4: Using the test conditions determined in S3, perform electron probe fine spectral scanning on the trace elements in the extraterrestrial zircon to test the content of trace elements in the extraterrestrial zircon.

2. The method according to claim 1, characterized in that Laser ablation-inductively coupled plasma mass spectrometry was used to verify the composition homogeneity of zircon standards.

3. The method according to claim 1, characterized in that The calibration standard for Al and Y is Y3Al5O 12 The calibration standard for Ti is rutile, the calibration standard for P is apatite, the calibration standard for Hf is pure Hf metal, and the calibration standard for Yb is rare earth element synthetic glass with a Yb content of 10.54 wt.%.

4. The method according to claim 1, characterized in that: According to the characteristic X-ray properties of trace elements, the characteristic X-ray line series of Al, Ti and P are selected as the Kα line series, and the characteristic X-ray line series of Hf, Yb and Y are selected as the Lα line series.

5. The method according to claim 1, characterized in that: The accelerating voltage was set to 20 kV, the beam current was set to 40 nA for testing Hf, and the beam current was set to 500 nA for testing Al, Ti, P, Yb, and Y.

6. The method according to claim 1, characterized in that The double crystal enhanced mode was used to analyze the trace elements Al and Y, the LLIF crystal was used as the spectroscopic crystal to test Hf and Yb, and the LPET crystal was used as the spectroscopic crystal to test P and Ti.

7. The method according to claim 1, characterized in that The peak analysis time for testing Hf was set to 30 s, and the background value analysis time was set to 15 s; the peak analysis time for testing Al, Ti, P, Yb, and Y was set to 240 s, and the background value analysis time was set to 60 s.

8. The method according to claim 1, characterized in that The before and after background values ​​of test P are (None, +300), the before and after background values ​​of test Yb are (-530, +600), the before and after background values ​​of test Ti are (-750, +450), the before and after background values ​​of test Y are (Sp1 -300, None) (Sp4 -200, None), the before and after background values ​​of test Al are (Sp1 -600, +450) (Sp4 -550, +500), and the before and after background values ​​of test Hf are (-600, +650).

9. The method according to claim 1, characterized in that: The method further comprises step S5: step S4 tests the content of trace elements in the extraterrestrial zircon, and if the test result of the trace element content is abnormal, continues to adjust and optimize the electron probe test conditions until the content of trace elements in the extraterrestrial zircon is tested normally.

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