Detection method of zircon zirconium isotope

Abstract

The invention relates to the technical field of geochemical analysis, in particular to a zircon zirconium isotope detection method, which comprises the following steps: co-loading a zircon sample to be detected and a standard sample with a coherent growth structure; a femtosecond laser system integrated with laser-induced breakdown spectroscopy is used for performing real-time component sensing and dynamically adjusting laser parameters so as to realize intelligent denudation, generated aerosol is ionized by a series quadrupole rod inductively coupled plasma mass spectrometer, and interference is eliminated through two-stage mass screening and chemical reaction in a reaction tank; and a multi-receiver array is adopted to synchronously detect signals, and finally, multi-source data are fused and input into a pre-trained machine learning model for intelligent correction, so that the problems that polyatomic ion interference is serious, the matrix effect is remarkable, and high spatial resolution and analysis precision are difficult to consider at the same time are effectively solved. And high-precision and high-accuracy micro-area in-situ analysis of the zircon zirconium isotope is realized.

Description

Technical Field

[0001] This invention relates to the field of geochemical analysis technology, and in particular to a method for detecting zircon isotopes. Background Technology

[0002] Zircon is a common accessory mineral in igneous, metamorphic, and sedimentary rocks. Due to its stable physicochemical properties, high uranium and thorium content, and low lead content, it is one of the most ideal minerals for uranium-lead isotope dating. The uranium-lead isotope age of zircon can not only accurately determine the formation age of geological bodies, but its zircon isotope composition is also a key geochemical tracer for revealing petrogenesis, crustal evolution, and crust-mantle interactions. Therefore, high-precision and high-accuracy zircon isotope analysis techniques are an important support for contemporary Earth science research.

[0003] To obtain isotopic information within zircon, in-situ micro-area analysis techniques have become mainstream. Among them, secondary ion mass spectrometry (SIMS) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) are the two most widely used techniques. SIMS utilizes a primary ion beam to bombard the zircon surface, generating secondary ions for high spatial resolution (micrometer-level) analysis, making it particularly suitable for micro-area dating of complex-zoned zircons. LA-ICP-MS, on the other hand, uses a laser beam to ablate zircon, generating aerosols which are then ionized by plasma and detected by a mass spectrometer, offering advantages such as fast analysis speed and relatively low cost. These techniques effectively solve the problem of mixed information from different genetic domains in traditional whole-grain analysis (such as isotope dilution-thermal ionization mass spectrometry, ID-TIMS), enabling precise targeted analysis of different regions within a single zircon grain.

[0004] However, existing micro-area in-situ analysis techniques still have significant limitations. First, for SIMS, the matrix effect present during the analysis process is a key factor affecting the accuracy of isotope ratios. Correction using standard materials highly matched to the chemical composition and crystal structure of the zircon being analyzed is necessary, which limits its versatility to some extent. Second, while LA-ICP-MS offers high throughput, it is susceptible to interference from polyatomic ions generated by the high zircon and silicon content in zircon during zircon isotope analysis. Even with techniques such as collision / reaction cells, this interference is difficult to completely eliminate, affecting the precision and accuracy of low-content Hf isotope analysis. Furthermore, both SIMS and LA-ICP-MS present a trade-off between spatial resolution and analytical sensitivity and precision. It is difficult to obtain high-precision trace element and isotope data while maintaining high spatial resolution (<10 μm), which limits the study of finer zircon zoning or early core information. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting zircon zircon isotopes, which solves the problems of severe polyatomic ion interference, significant matrix effects, and difficulty in balancing high spatial resolution and analytical accuracy in existing micro-area in-situ analysis techniques.

[0006] To achieve the above objectives, the present invention provides a method for detecting zircon isotopes, comprising the following steps: The zircon sample to be tested and the standard sample were prepared together and loaded into the laser ablation sample chamber; The analytical micro-area of ​​the zircon sample to be tested is pre-etched, and laser-induced breakdown spectrum signals are collected simultaneously. The elemental composition information of the analytical micro-area is obtained in real time based on the laser-induced breakdown spectrum signals, and the laser parameters for subsequent formal etching are dynamically adjusted accordingly. The analytical micro-area is then formally etched using the adjusted laser parameters to generate aerosols. The aerosol is transported via carrier gas to the plasma of a series quadrupole inductively coupled plasma mass spectrometer for ionization. The target zirconium isotope ions are screened out by the first quadrupole mass analyzer. The screened ions are then introduced into a second quadrupole reaction cell filled with reaction gas to carry out a chemical reaction and generate product ions. The product ions are then screened by the third quadrupole mass analyzer, and the signals of each product ion after screening are detected simultaneously by a multi-receiver array. Multi-source data for each analytical micro-region is collected and integrated, and the multi-source data is input into a pre-trained machine learning model to calculate the final zircon isotope ratio of the analytical micro-region of the zircon sample to be tested.

[0007] The process involves preparing the zircon sample to be tested and a standard sample together and loading them into a laser ablation sample chamber, specifically including: The standard sample is a zircon with a coherent growth structure, which consists of a standard zircon matrix with a known zircon isotope composition and an epitaxially grown zircon thin layer of the test that matches the zircon's composition and crystal structure. The thickness of the epitaxially grown zircon thin layer of the test is 1 micrometer to 5 micrometers.

[0008] The process involves pre-etching the analytical micro-region of the zircon sample and simultaneously acquiring laser-induced breakdown spectral signals. Based on these signals, the elemental composition of the analytical micro-region is obtained in real time, and the laser parameters for subsequent formal etching are dynamically adjusted accordingly. The adjusted laser parameters are then used to perform formal etching of the analytical micro-region, generating aerosols. Specifically, this includes: The dynamically adjusted laser parameters include at least one of laser energy density, beam diameter, and ablation frequency.

[0009] The process involves ionizing the aerosol in a tandem quadrupole inductively coupled plasma mass spectrometer via a carrier gas. Target zirconium isotope ions are then selected using a first quadrupole mass analyzer. These selected ions proceed to a second quadrupole reaction cell filled with reactive gas for chemical reaction, generating product ions. A third quadrupole mass analyzer further filters the product ions, and a multi-detector array simultaneously detects the signals of each filtered product ion. Specifically, the process includes: The type of reaction gas is dynamically selected based on the intensity of the interfering element fed back in the laser-induced breakdown spectrum signal; when the interference intensity of ytterbium or lutetium is higher than a preset threshold, ammonia is selected as the reaction gas; when the interference intensity of ytterbium or lutetium is lower than a preset threshold, oxygen or nitrous oxide is selected as the reaction gas.

[0010] The process involves ionizing the aerosol in the plasma of a tandem quadrupole inductively coupled plasma mass spectrometer via a carrier gas. Target zirconium isotope ions are then screened using a first quadrupole mass analyzer. The screened ions proceed to a second quadrupole reaction cell filled with reactive gas for chemical reaction, generating product ions. These product ions are then mass-screened using a third quadrupole mass analyzer, and a multi-receiver array is used to simultaneously detect the signals of each screened product ion. The process further includes: The multi-receiver array synchronously detects at least the product ion signal of the target zirconium isotope, the product ion signal of the internal standard zirconium isotope, and an interfering product ion signal for monitoring.

[0011] This process involves collecting and integrating multi-source data from each analytical micro-region, inputting the multi-source data into a pre-trained machine learning model, and calculating the final zircon isotope ratio of the analytical micro-region of the zircon sample to be tested. Specifically, this includes: The multi-source data includes laser-induced breakdown spectral signals, dynamically adjusted laser parameters, raw ion signal intensities acquired by a multi-receiver array, and correction factors calculated in real time based on the standard sample.

[0012] This process includes collecting and integrating multi-source data from each analytical micro-region, inputting the multi-source data into a pre-trained machine learning model, and calculating the final zircon isotope ratio of the analytical micro-region of the zircon sample to be tested. Specifically, it also includes: The pre-trained machine learning model is a gradient boosting tree model or a neural network model.

[0013] This invention discloses a method for detecting zircon zircon isotopes. The method involves co-loading the zircon sample to be tested with a standard sample exhibiting a coherent growth structure. A femtosecond laser system integrating laser-induced breakdown spectroscopy is used for real-time component sensing and dynamic adjustment of laser parameters to achieve intelligent ablation. The resulting aerosol is ionized by a tandem quadrupole inductively coupled plasma mass spectrometer (ICP-MS). Interference is eliminated through two-stage mass screening and chemical reaction in a reaction cell. A multi-receiver array is used for synchronous signal detection. Finally, multi-source data is integrated into a pre-trained machine learning model for intelligent correction. This method effectively solves the problems of severe multi-atomic ion interference, significant matrix effects, and the difficulty in balancing high spatial resolution and analytical accuracy, achieving high-precision, high-accuracy in-situ micro-area analysis of zircon zircon isotopes. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0015] Figure 1 This is a flowchart of the steps of the zircon zircon isotope detection method of the present invention. Detailed Implementation

[0016] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0017] Please see Figure 1 ,in, Figure 1 This is a flowchart of the steps of the zircon zircon isotope detection method of the present invention.

[0018] This invention provides a method for detecting zircon isotopes, comprising the following steps: S101: The zircon sample to be tested and the standard sample are prepared together and loaded into the laser ablation sample chamber; Specifically, the first step is sample preparation. The standard sample is a specially prepared zircon with a coherent growth structure. This standard sample consists of two parts: the matrix is ​​a standard zircon crystal with a known precise zircon isotopic composition, on which a thin layer with a composition and crystal structure highly matching the zircon sample to be tested is epitaxially grown using hydrothermal or high-temperature solid-state methods. Furthermore, the thickness of the epitaxially grown thin layer needs to be precisely controlled between 1 and 5 micrometers. This scale design aims to maximize the simulation of the actual micro-area to be tested in terms of physicochemical properties, while ensuring that it provides an effective real-time signal in subsequent analysis. After preparation, the zircon sample to be tested and this specially prepared coherently grown standard sample undergo a standard probe preparation process, including polishing and cleaning, to ensure the smoothness and cleanliness of the analytical surface. Subsequently, the prepared probe is carbon-plated to make its surface conductive, meeting the physical requirements of laser ablation and subsequent ionization processes. Finally, the processed probe sheet containing both the test sample and the standard sample is securely mounted in the sample chamber of the laser ablation system, ensuring its fixed position to lay the foundation for subsequent in-situ micro-area analysis. The core purpose of this co-mounted design is to utilize this coherently grown standard sample under almost identical analytical conditions to provide a real-time, accurate matrix effect correction benchmark for subsequent steps, thereby improving the accuracy and reliability of the final isotope analysis results from the outset.

[0019] S102: Pre-etch the analytical micro-area of ​​the zircon sample to be tested, and simultaneously acquire the laser-induced breakdown spectrum signal. Based on the laser-induced breakdown spectrum signal, obtain the elemental composition information of the analytical micro-area in real time, and dynamically adjust the laser parameters for subsequent formal etching accordingly. Use the adjusted laser parameters to perform formal etching on the analytical micro-area to generate aerosol. Specifically, the laser system is first moved and focused onto a pre-defined analytical micro-region of the zircon sample. The system first emits a series of low-energy femtosecond laser pulses to pre-eject this micro-region, removing only trace amounts of surface material. Simultaneously, the integrated laser-induced breakdown spectroscopy module is triggered, acquiring the plasma emission signal generated during the pre-ejection process—the laser-induced breakdown spectral signal. This spectral signal is rapidly transmitted to the data processing system, where it is analyzed in real-time using a built-in elemental spectral library. This allows for the rapid acquisition of key semi-quantitative elemental composition information for the analytical micro-region, such as the zircon-hafnium ratio and the approximate content of rare earth elements (especially interfering elements ytterbium and lutetium).

[0020] Based on real-time acquired elemental composition information, the system's control algorithm dynamically adjusts the laser parameters required for subsequent formal ablation. These parameters include, but are not limited to, one or more of the following: laser energy density, beam diameter, and ablation frequency. For example, if a high uranium or thorium content is detected in the current micro-area, it may indicate severe radiation damage, and the system will automatically lower the laser energy density to reduce fractionation caused by thermal effects; if the micro-area composition is relatively uniform, preset optimization parameters are used to pursue efficiency; if the beam diameter is set small, and high spatial resolution is desired, the ablation frequency may be adjusted accordingly to maintain sufficient signal strength.

[0021] After the laser parameters were dynamically adjusted, the system immediately used these optimized parameters to perform formal ablation on the same analytical micro-region. High-energy femtosecond laser pulses precisely ablated the zircon material, converting it into an aerosol containing information about the micro-region's composition. The aerosol generated in this process used high-purity helium as the primary carrier gas, mixed with a small amount of nitrogen or hydrogen, forming a stable gas flow that was effectively transported out of the laser ablation cell, preparing it for subsequent mass spectrometry analysis. Through closed-loop control of "sensing-decision-execution," the representativeness, efficiency, and adaptability to zircon with complex compositions were significantly improved.

[0022] S103: The aerosol is transported by carrier gas to the plasma of a series quadrupole inductively coupled plasma mass spectrometer for ionization. The target zirconium isotope ions are screened by the first quadrupole mass analyzer. The screened ions are then introduced into a second quadrupole reaction cell filled with reaction gas to carry out a chemical reaction and generate product ions. The product ions are then screened by the third quadrupole mass analyzer, and the signals of each product ion after screening are detected synchronously by a multi-receiver array. Specifically, the aerosol carried by helium gas is stably transported to an inductively coupled plasma source. In the high-temperature plasma (temperatures can reach thousands to tens of thousands of degrees Celsius), the aerosol particles are completely evaporated, atomized, and ionized to form a positively charged ion beam containing the zirconium isotope ions to be measured, as well as a large number of other ions.

[0023] The ion beam is first introduced into a first quadrupole mass analyzer. This quadrupole is configured as a high-quality filter, allowing only ions with a preset target mass number to pass through stably. This is used to determine... 176 Taking Hf as an example, Q1 will be precisely set to a quality number of 176, thereby filtering out... 176 Hf + Ions. This step effectively removes the vast majority of ions that are not of the target mass number, completing the primary purification.

[0024] The target ions selected through Q1 are then fed into a second quadrupole, which operates as a reaction cell filled with a specific type of reaction gas. The selection of the reaction gas is not fixed but dynamically determined based on the intensity of interfering elements (such as ytterbium and lutetium) as reflected in the real-time feedback from the laser-induced breakdown spectrum in step S102. When the feedback indicates that the interference intensity of Yb or Lu is higher than a preset threshold, the system automatically selects ammonia as the reaction gas; when the interference level is low, oxygen or nitrous oxide can be used. In the reaction cell, the target ions undergo characteristic chemical reactions with the reaction gas molecules. For example, when using ammonia… 176 Hf + Ions can undergo efficient ligand exchange reactions with it to generate adduct ions with larger mass numbers. 176 Hf(NH) + ; and potential equal-mass interfering ions 176 Yb + and 176 Lu + It hardly reacts with ammonia. This chemical reaction process enables the effective "labeling" and separation of target analytes in the presence of interfering ions.

[0025] All ions produced after the reaction (including converted product ions and unreacted ions) then enter a third quadrupole mass analyzer. Q3 is set to allow only product ions with a specific mass number to pass through. Continuing the previous example, when the target analyte is... 176 Hf(NH) + At this time, Q3 is set at a mass number of 191. After this final mass screening, almost all of the signals reaching the detector are the desired target signals, thus fundamentally eliminating interference from polyatomic ions and isotopes.

[0026] Finally, a multi-receiver array was used to synchronously detect the ion signals passing through Q3. This array contained at least three independent receivers, each used to synchronously acquire the product ion signals of the target zirconium isotope, such as... 176 Hf(NH) + The product ion signal of the internal standard zirconium isotope, such as 179 Hf(NH) + The system also includes a product ion signal for monitoring residual interference. This multi-channel synchronous measurement mode, compared to traditional single-receiver sequential scanning, not only significantly improves analysis efficiency but also completely eliminates ratio measurement errors caused by instantaneous signal fluctuations, thus providing a highly accurate and synchronized set of raw signal data for the final calculation.

[0027] S104: Collect and integrate multi-source data for each analytical micro-region, input the multi-source data into a pre-trained machine learning model, and calculate the final zircon isotope ratio of the analytical micro-region of the zircon sample to be tested.

[0028] Specifically, the process begins by collecting and integrating multi-source data from previous steps, each corresponding to a specific micro-region being analyzed. This data constitutes a comprehensive dataset, primarily including: the laser-induced breakdown spectral signal obtained in step S102 and its elemental composition information, dynamically adjusted laser parameters used (such as energy density and beam diameter), the original signal intensities of each product ion obtained from step S103 by a multi-receiver array, and a crucial calibration benchmark—the instrument drift and matrix correction factor calculated in real time based on signals measured from co-loaded coherently grown standard samples within the same analysis cycle.

[0029] Next, this comprehensive dataset containing multi-dimensional features is fed into a pre-trained machine learning model for processing. This model, such as a gradient boosting tree or neural network, has been trained on a large amount of standard sample data with known accurate zirconium isotope ratios. The training process enables the model to learn and master the precise mapping between complex, potentially non-linear, raw data and the true isotope ratios.

[0030] In the application phase, this well-trained model intelligently analyzes the input multi-source data. It can automatically identify and compensate for systematic errors introduced by factors such as instrument fluctuations, residual matrix effects, signal interference, and differences in laser ablation behavior. The model's final output is the depth-corrected final zircon isotope ratio for the micro-area of ​​the zircon sample being analyzed, such as... 176 Hf / 177 Hf.

[0031] This machine learning-based data processing paradigm surpasses traditional correction methods that rely on fixed mathematical formulas or linear interpolation. It can more accurately handle complex interferences and effects in real-world analysis, thereby significantly improving the accuracy, precision, and overall robustness of the analysis results.

[0032] By introducing coherent growth structure standard samples to suppress matrix effects at the source, and utilizing laser-induced breakdown spectroscopy real-time feedback and dynamic laser tuning to achieve adaptive micro-area ablation, combined with the reaction cell technology of tandem quadrupole inductively coupled plasma mass spectrometry and multi-receiver detection to completely eliminate polyatomic ion interference, and finally using machine learning models to intelligently fuse and nonlinearly correct multi-source data, the system systematically solved three major technical challenges: significant matrix effects, severe polyatomic ion interference, and the difficulty in balancing high spatial resolution and analytical accuracy. Ultimately, it achieved high-precision, high-accuracy, and high-robust in-situ analysis of zircon zircon isotopes at the micrometer scale.

[0033] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for detecting zircon isotopes, characterized in that, Includes the following steps: The zircon sample to be tested and the standard sample were prepared together and loaded into the laser ablation sample chamber; The analytical micro-area of ​​the zircon sample to be tested is pre-etched, and laser-induced breakdown spectrum signals are collected simultaneously. The elemental composition information of the analytical micro-area is obtained in real time based on the laser-induced breakdown spectrum signals, and the laser parameters for subsequent formal etching are dynamically adjusted accordingly. The analytical micro-area is then formally etched using the adjusted laser parameters to generate aerosols. The aerosol is transported via carrier gas to the plasma of a series quadrupole inductively coupled plasma mass spectrometer for ionization. The target zirconium isotope ions are screened out by the first quadrupole mass analyzer. The screened ions are then introduced into a second quadrupole reaction cell filled with reaction gas to carry out a chemical reaction and generate product ions. The product ions are then screened by the third quadrupole mass analyzer, and the signals of each product ion after screening are detected simultaneously by a multi-receiver array. Multi-source data for each analytical micro-region is collected and integrated, and the multi-source data is input into a pre-trained machine learning model to calculate the final zircon isotope ratio of the analytical micro-region of the zircon sample to be tested.

2. The method for detecting zircon zircon isotopes as described in claim 1, characterized in that, The zircon sample to be tested and the standard sample were prepared together and loaded into the laser ablation sample chamber, specifically including: The standard sample is a zircon with a coherent growth structure, which consists of a standard zircon matrix with a known zircon isotope composition and an epitaxially grown zircon thin layer of the test that matches the zircon's composition and crystal structure. The thickness of the epitaxially grown zircon thin layer of the test is 1 micrometer to 5 micrometers.

3. The method for detecting zircon zircon isotopes as described in claim 2, characterized in that, The analytical micro-region of the zircon sample to be tested is pre-etched, and laser-induced breakdown spectral signals are acquired simultaneously. Based on the laser-induced breakdown spectral signals, the elemental composition information of the analytical micro-region is obtained in real time, and the laser parameters for subsequent formal etching are dynamically adjusted accordingly. The formal etching of the analytical micro-region is then performed using the adjusted laser parameters, generating aerosols. Specifically, this includes: The dynamically adjusted laser parameters include at least one of laser energy density, beam diameter, and ablation frequency.

4. The method for detecting zircon zircon isotopes as described in claim 3, characterized in that, The aerosol is transported via carrier gas to the plasma of a tandem quadrupole inductively coupled plasma mass spectrometer (QCPMS) for ionization. Target zirconium isotope ions are screened using a first quadrupole mass analyzer. The screened ions then enter a second quadrupole reaction cell filled with reactive gas for chemical reaction, generating product ions. These product ions are then mass-screened using a third quadrupole mass analyzer, and the signals of each screened product ion are simultaneously detected using a multi-receiver array. Specifically, this process includes: The type of reaction gas is dynamically selected based on the intensity of the interfering element fed back in the laser-induced breakdown spectrum signal; when the interference intensity of ytterbium or lutetium is higher than a preset threshold, ammonia is selected as the reaction gas; when the interference intensity of ytterbium or lutetium is lower than a preset threshold, oxygen or nitrous oxide is selected as the reaction gas.

5. The method for detecting zircon zircon isotopes as described in claim 4, characterized in that, The aerosol is transported via carrier gas to the plasma of a tandem quadrupole inductively coupled plasma mass spectrometer for ionization. Target zirconium isotope ions are screened using a first quadrupole mass analyzer. The screened ions then enter a second quadrupole reaction cell filled with reactive gas for chemical reaction, generating product ions. These product ions are then mass-screened using a third quadrupole mass analyzer, and the signals of each screened product ion are simultaneously detected using a multi-receiver array. Specifically, the process also includes: The multi-receiver array synchronously detects at least the product ion signal of the target zirconium isotope, the product ion signal of the internal standard zirconium isotope, and an interfering product ion signal for monitoring.

6. The method for detecting zircon zircon isotopes as described in claim 5, characterized in that, Multi-source data for each analytical micro-region is collected and integrated. This multi-source data is then input into a pre-trained machine learning model to calculate the final zircon isotope ratio for each analytical micro-region of the zircon sample. Specifically, this includes: The multi-source data includes laser-induced breakdown spectral signals, dynamically adjusted laser parameters, raw ion signal intensities acquired by a multi-receiver array, and correction factors calculated in real time based on the standard sample.

7. The method for detecting zircon zircon isotopes as described in claim 6, characterized in that, Collecting and integrating multi-source data from each analytical micro-region, inputting the multi-source data into a pre-trained machine learning model, and calculating the final zircon isotope ratio of the analytical micro-region of the zircon sample to be tested, specifically also includes: The pre-trained machine learning model is a gradient boosting tree model or a neural network model.

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