Method for researching influence of radioactive elements on mineral crystal structure

Abstract

The invention belongs to the cross technical field of mineralogy, radiochemistry and material microstructure analysis, and particularly relates to a method for researching the influence of radioactive elements on a mineral crystal structure. The method comprises the steps of sample preparation and target area screening, carrier mineral morphology and component characterization, overall structure analysis, micro-area accurate positioning and transmission electron microscope sample preparation, direct observation and association of atomic scale microstructure damage, data integration and mechanism research. According to the technical scheme, real'in-situ-correlation 'analysis is achieved, a complete evidence chain from macroscopic scale to atomic scale is established, microscopic heterogeneity which is difficult to find by a traditional method is revealed, and the application value is wide.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary technical field of mineralogy, radiochemistry and materials microstructure analysis, and specifically relates to a research method for the influence of radioactive elements on mineral crystal structure. Background Technology

[0002] The long-term presence of radioactive elements (such as U and Th) in minerals can disrupt the crystal lattice through their decay process, leading to amorphization (transformation) and affecting the physicochemical properties and long-term stability of the minerals. Accurately assessing this impact is crucial for the development and utilization of radioactive deposits, nuclear waste disposal, and mineral dating.

[0003] Existing technologies typically employ single or a few characterization methods, but these have significant limitations. For example: single chemical analysis (such as LA-ICP-MS) can accurately determine elemental and isotopic content, but cannot directly obtain structural information; single structural analysis (such as XRD) can obtain overall average crystal structure parameters, but is insensitive to micro-regions and non-uniform radiation damage, making it difficult to locate damaged areas; conventional micro-region morphology analysis (such as SEM) can observe surface morphology, but cannot obtain atomic-scale structural information within the crystal.

[0004] The data from various techniques in existing methods are isolated from each other, making it difficult to directly and accurately correlate the microscopic distribution of radioactive elements with the specific structural damage morphology they cause in space. This makes it impossible to fully reveal the complete chain from elemental substitution to mineral lattice changes. In particular, for radioactive elements that are dispersed in an isomorphic manner, it is difficult to accurately locate their enrichment areas and analyze the fine structural changes in those areas. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems and provide a systematic, precise, and multi-scale research method. This method can rapidly screen and accurately locate mineral particles containing radioactive elements and their internal radioactive element-enriched micro-regions (such as zonation) within complex natural minerals. It establishes a spatial correspondence between elemental distribution (type, content) and crystal structure state (lattice parameters, order, defect type) within the same micro-region, and further elucidates the role of radioactive elements (such as U) at the atomic scale. 4+ By examining the specific effects of isomorphic substitution on the crystal lattice of the carrier mineral (such as lattice expansion, amorphization, dislocation generation, etc.), the degree of damage can be quantitatively or semi-quantitatively assessed, ultimately ensuring the logical coherence and data verifiability from macroscopic statistics to atomic-scale observation.

[0006] Specifically, the research methods for studying the influence of radioactive elements on mineral crystal structures include: A method for studying the influence of radioactive elements on mineral crystal structure, the method comprising: Step 1: Sample preparation and target region screening: Prepare optical sheets from ore samples suitable for testing; Using an automated mineral analysis system combined with scanning electron microscopy and energy dispersive spectroscopy, the target mineral group containing radioactive elements was preliminarily delineated. Step 2: Characterization of the morphology and composition of the carrier minerals: In-situ quantitative analysis and surface scanning analysis of carrier minerals were performed using electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry. Backscattered electron imaging was used to identify the microstructural features of carrier minerals; By combining the microstructural characteristics of the carrier mineral, we can identify the microstructural features caused by elemental differences. Step 3: Overall structural analysis: The carrier mineral was cut and extracted using a focused ion beam system. The extracted carrier mineral particles were subjected to X-ray diffraction or single-crystal X-ray diffraction tests. Obtain the unit cell parameters and the trend of unit cell variation; Step 4: Precise micro-area localization and transmission electron microscopy sample preparation: Based on the data from step 2, focused ion beam sample preparation is performed targeting the region of interest; Regions of interest include regions enriched with radioactive elements and regions with characteristic structures; Step 5: Direct observation and correlation of atomic-scale microstructural damage: The sample prepared in step 4 was observed under a transmission electron microscope. The crystallization state was determined by selected area electron diffraction. The changes in the crystal structure of the carrier mineral were determined by analyzing the morphology and characteristics of the diffraction rings. Further high-resolution transmission electron microscopy imaging studies were conducted on regions that still retained crystal structure to identify crystal defects; In TEM mode, combined with energy dispersive spectroscopy, micro-area composition analysis was performed on the observed amorphous and crystalline regions to verify the spatial correspondence between "high radioactive element content" and "amorphous structure / specific defects" at the nanoscale. Step 6: Data Integration and Mechanism Study By integrating the data from all the aforementioned steps, a damage evolution model of radioactive elements in minerals is constructed, which follows the sequence of "occurrence form → local lattice distortion / expansion → generation of micro-defects → accumulation leading to amorphization".

[0007] The core innovation of this invention lies not in the use of a single instrument, but in the construction of a unique "analysis chain": Directional navigation analysis: Using BSE images and elemental surface distribution maps as "maps", the FIB is guided to perform "surgical" point sampling on composition-specific regions (such as high-uranium rings), solving the fundamental problem of inconsistency between "the place to measure composition" and "the place to observe structure".

[0008] A closed-loop evidence chain across scales: from the mineral statistics of AMICS (millimeter-micrometer scale), to the elemental distribution of EMPA (micrometer scale), to the lattice parameters of SCXRD (cell scale), and finally to the atomic arrangement of HRTEM (angstrom scale), a logically consistent and scale-connected complete chain of evidence is formed.

[0009] Discovery of hidden inhomogeneities: As shown in Example 2, the present invention can reveal the dramatic structural differentiation (coexistence of amorphous matrix and nanocrystalline domains) at the nanoscale within minerals that appear homogeneous at the macro or microscale, which is crucial for accurately assessing the long-term behavior of minerals.

[0010] The above-mentioned research methods for studying the influence of radioactive elements on mineral crystal structure, wherein the minerals are zircon, pyrochlore, monazite, rutile, calcite, apatite, epidote, xenotime, etc.

[0011] As a preferred option, in the above-mentioned method for studying the influence of radioactive elements on mineral crystal structure, step 1 uses an automated mineral analysis system, either AMICS or TIMA. AMICS (Automated Mineralogy and Imaging System) is based on scanning electron microscopy (SEM) + energy-dispersive X-ray spectroscopy (EDS) technology, combined with high-speed energy spectrum acquisition and image recognition algorithms to achieve automatic identification, quantitative analysis, and three-dimensional visualization of mineral samples. Working principle: Imaging: SEM obtains secondary electron (SE) images and high-resolution backscattered electron (BSE) images of the sample surface; Composition analysis: The EDS detector acquires elemental composition information for each pixel in real time; Mineral identification: The software compares the EDS data with a mineral database and uses grayscale threshold segmentation (BSE contrast) to distinguish mineral types; Data statistics: Quantitative results such as mineral content percentage, grain size distribution, and coexistence relationship maps are generated. TIMA (Tescan Integrated Mineral Analyzer) is another automated mineral analysis platform developed by TESCAN. Also based on SEM+EDS technology, it emphasizes complete hardware and software integration, seamlessly connecting the entire process from scanning to mineral identification, and is optimized for industrial and scientific applications. Working principle: Scanning Imaging: TIMA is equipped with a high-brightness field emission SEM and fast BSE imaging to achieve high-contrast mineral differentiation; High-Speed ​​EDS Analysis: Employs a large-window EDS detector to improve acquisition efficiency and reduce analysis time; Intelligent Mineral Interpretation: Built-in machine learning-based mineral classification algorithms can handle complex multiphase systems; Data Output: Generates mineral distribution maps, elemental surface distributions, statistical reports, and 3D models.

[0012] The aforementioned research methods on the effects of radioactive elements on mineral crystal structures specifically involve in-depth studies of how radioactive elements alter mineral crystal structures, particularly the lattice distortions induced by uranium (U) and thorium (Th), two typical radioactive elements, in different minerals. For step 1, the radioactive element is at least one of U and Th. This focus concentrates on radioactive elements that are ubiquitous in nature and significantly detrimental to mineral crystals. Uranium and thorium are both long-lived radionuclides whose decay processes continuously release alpha particles and other secondary particles, which are important sources of localized lattice damage and amorphization transformation in minerals. By focusing on these two typical radioactive elements, the research can be ensured to have practical significance and scientific representativeness, while also providing methodological references for the study of other radioactive elements (such as potassium-40 and rubidium-87).

[0013] As a preferred approach, the aforementioned method for studying the influence of radioactive elements on mineral crystal structure involves, in step 2, in-situ quantitative micro-area analysis of the carrier mineral using electron probe microanalysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to obtain precise content, spatial distribution, and surface scan maps of major, minor, and trace elements. This step achieves accurate quantification of the types and contents of elements in the mineral through high-precision and high-sensitivity in-situ micro-area analysis technology. Electron probe microanalysis (EMPA) can provide quantitative information on elements at micrometer-level spatial resolution, making it particularly suitable for quantitative analysis of major elements (such as Zr, Si, Ti, etc.) and key trace elements (such as U, Th) in minerals. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), on the other hand, possesses extremely high sensitivity and the ability to simultaneously detect multiple elements, enabling the detection of trace radioactive elements and their isotopes. It also provides element mapping images, visually demonstrating the spatial enrichment characteristics of radioactive elements within the mineral, such as banded distribution, fissure enrichment, or inclusion aggregation. This comprehensive analysis method, which combines quantitative analysis, spatial distribution analysis, and morphological correlation analysis, lays the foundation for the subsequent precise location of "high-radioactive damage areas" and is a key step in achieving correlation analysis "from composition to structure".

[0014] The research method for studying the influence of radioactive elements on mineral crystal structure, as described above, includes, in step 2, at least one of the following microstructural features: zoning, fissures, inclusions, irradiation halos, dissolution cavities, and twins. In radioactive minerals, microstructural features often represent the "footprints" of radioactive element enrichment or migration. For example, zoning structures are common in minerals such as zircon, recording element fractionation or changes in environmental conditions during crystal growth, and are also common areas where elements such as U and Th accumulate within specific growth zones. Fissures provide channels and sites for the diffusion, enrichment, and even precipitation of radioactive elements, and are often accompanied by significant element segregation and structural damage around them. Inclusions (such as fluid inclusions and mineral inclusions) may be "residual areas" where radioactive elements are captured after mineral crystallization, and local amorphization or lattice distortion can easily occur within or around them. Irradiation halos are abnormal regions of color or structure formed by the movement of alpha particles released from the decay of radioactive elements within the crystal and causing local lattice damage; they typically appear as dark or light-colored zoning rings distributed concentrically around a central radioactive source. The size and distribution of these halos directly reflect the range and energy of alpha particles, and therefore can be used to infer the type and content of radioactive elements. Their presence also indicates significant lattice damage in the region, potentially becoming the starting point for subsequent structural evolution. Dissolution cavities are voids or pits formed after mineral formation due to chemical corrosion, hydrothermal activity, or stress release, resulting in partial dissolution of the crystal structure. The edges and interiors of these cavities easily become secondary enrichment zones for radioactive elements, as elements such as U and Th in solution can be adsorbed or co-precipitated on the pore surface. Simultaneously, lattice mismatches and dislocation concentrations often appear around the cavities, providing space for radiation damage accumulation. In microscopic observation, dissolution cavities are often accompanied by high concentrations of elemental segregation or anomalous reflectivity. Twins are formed by lattice rearrangement according to certain symmetry rules during crystal growth or deformation. Their interfaces can become stress concentration points and defect aggregation areas. In radioactive minerals, twin boundaries not only easily capture impurity elements but also provide rapid pathways for the diffusion and local enrichment of radioactive elements. Furthermore, high-energy particles generate additional lattice shifts when crossing twin boundaries, making these regions more prone to accumulating radiation damage than the matrix, thus exhibiting unique morphologies and diffraction characteristics in structural characterization. In summary, irradiation halos record the physical trajectory of radioactive element decay, dissolution pores reflect the influence of subsequent chemical-physical modifications on element migration and storage, and twins reflect the response of internal crystal symmetry and defect structures to radioactive effects. Identifying and analyzing these microstructural features not only helps in understanding the storage forms of radioactive elements but also provides guidance for subsequent micro-area sampling strategies—for example, prioritizing high-resolution structural observation of areas such as rings, crack edges, or near inclusions, thereby making it easier to discover "hot spots" of radiation damage.

[0015] In step 3 of the aforementioned method for studying the influence of radioactive elements on mineral crystal structure, the extracted carrier mineral particles are subjected to X-ray diffraction or single-crystal X-ray diffraction tests to obtain cell parameters, atomic occupancy, anisotropic displacement parameters, and bond lengths. This step aims to reveal the overall trend of mineral crystal structure changes from the macroscopic to near-atomic scale. X-ray diffraction (XRD) or the more refined single-crystal X-ray diffraction (SCXRD) is one of the most classic and reliable methods for studying crystal structure. These techniques can obtain crystal cell parameters (such as lattice constants a, b, c, and cell volume V) and further analyze key structural parameters such as atomic occupancy, bond lengths, and bond angles. More importantly, by comparing the changes in cell parameters before and after irradiation, the degree of lattice expansion or contraction can be quantitatively assessed—a direct reflection of lattice stress accumulation caused by radioactive elements (especially high-energy particles produced by alpha decay). Furthermore, changes in anisotropic displacement parameters can reflect abnormal atomic thermal vibrations or an increase in local disorder, providing auxiliary evidence for judging amorphization trends.

[0016] In the aforementioned method for studying the influence of radioactive elements on mineral crystal structures, step 4 produces samples that are ultrathin sheets or needles. To meet the stringent requirements of transmission electron microscopy (TEM) regarding sample thickness and morphology (typically less than 100 nm), the target micro-region must be processed into ultrathin sheet or needle-shaped samples. This sample shape ensures that the electron beam can penetrate while preserving as much of the original micro-region's structural features and compositional information as possible. Using focused ion beam (FIB) technology, precise positioning and micro / nano-scale processing of micron-scale target regions (such as high-uranium rings, specific cracks, or inclusions) can be achieved, ultimately producing TEM samples suitable for high-resolution imaging and electron diffraction analysis. This process is a crucial bridge from micro-region compositional analysis to atomic-scale structural observation and is also the technical guarantee for implementing the "in-situ correlation" approach in this method.

[0017] The research method for studying the influence of radioactive elements on mineral crystal structure, as described above, involves step 5, where the crystal defects to be investigated include at least one of dislocations, grain boundaries, stacking faults, and voids. In minerals suffering from radioactive damage, the formation of crystal defects is an unavoidable secondary effect. Dislocations are defects resulting from linear misalignment of atoms in a crystal, and their presence significantly affects the crystal's mechanical and transport properties. Grain boundaries are transitional regions between different grains, typically hotspots of structural disorder and elemental segregation, and locations where radiation damage easily accumulates and spreads. High-resolution transmission electron microscopy (HRTEM) imaging allows direct observation of the morphology, distribution, and density changes of these defects. For example, dense dislocation networks can be observed in certain high-uranium regions, or amorphous transition layers can be found at grain boundaries. These defects are not only a "visual manifestation" of lattice damage but may also further affect the physicochemical properties of minerals. Therefore, accurate identification and quantitative assessment of these defects are of great value for a comprehensive understanding of the mechanisms of radiation damage.

[0018] The research method for studying the influence of radioactive elements on mineral crystal structure, in step 6, after systematically building a damage evolution model of radioactive elements in minerals from “occurrence form → local lattice distortion / expansion → generation of micro-defects → accumulation leading to amorphization”, also includes: further comparing and evaluating the differences in the tolerance of different minerals to radiation damage.

[0019] In a more specific embodiment, the object of the present invention is achieved through the following steps: Step 1: Sample Preparation and Target Area Screening. The natural ore sample is crushed, graded, and prepared into slides suitable for the following tests. Using an automated mineral analysis system (AMICS or TIMA, etc.) combined with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the types, contents, particle size distribution, and co-occurrence relationships of minerals in the sample are automatically identified and statistically analyzed. Based on the characteristic peaks of radioactive elements in the energy dispersive spectroscopy image, the target mineral group containing radioactive elements (such as U, Th) is preliminarily delineated.

[0020] Step 2: Morphology and Composition Characterization of the Support Mineral. Backscattered electron (BSE) imaging is used to identify the microstructural features of the support mineral, such as zoning, fractures, and inclusions. Electron probe microanalysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are used to perform in-situ quantitative micro-area analysis of the support mineral, obtaining precise content, spatial distribution, and specific elemental surface scans of major, minor, and trace elements (especially radioactive elements such as U and Th). Combined with the microstructural features of the support mineral, microstructures caused by elemental differences, such as growth zoning, fractures, and inclusions, are identified. This step establishes a correlation between compositional data and morphological features, providing a basis for further judgment.

[0021] Step 3: Overall Structure Analysis. Using the elemental distribution map (e.g., U-plane scan image) and BSE image obtained in Step 2 as a navigation map, the carrier mineral particles are precisely located. The carrier mineral is extracted using a focused ion beam (FIB) system. X-ray diffraction (XRD) or single-crystal X-ray diffraction (SCXRD) tests are performed on the extracted carrier mineral particles. Through structural analysis and refinement, the cell parameters (a, b, c, V), atomic occupancy, anisotropic displacement parameters, and bond lengths are accurately obtained. The above parameters of the carrier mineral are compared with those of a standard mineral to obtain the cell variation trend.

[0022] Step 4: Precise Micro-region Localization and TEM Sample Preparation. The carrier mineral is prepared as a target sample and subjected to fine electron scanning. Combined with U-elemental surface scans and BSE images, characteristic micro-regions are precisely located on the carrier mineral particles. Using a focused ion beam (FIB) system, this specific micro-region is extracted and processed in situ to prepare ultrathin sections or needle-like samples suitable for TEM observation. This step is crucial for achieving "in-situ correlation." This technique ensures that the area for subsequent atomic-scale observation is precisely the specific location of interest in the initial compositional analysis.

[0023] Step 5: Direct observation and correlation of atomic-scale microstructural damage. The site-specific samples prepared in Step 4 are observed under a transmission electron microscope (TEM). The crystallization state of the micro-region is determined by selected area electron diffraction (SAED). The changes in the crystal structure of the carrier mineral are determined by analyzing the morphology and characteristics of the diffraction rings. For regions that still have crystalline structure, high-resolution transmission electron microscopy (HRTEM) imaging is further carried out to directly observe the atomic arrangement and investigate crystal defects such as dislocations and grain boundaries. In TEM mode, combined with energy dispersive spectroscopy (EDS), micro-region composition analysis is performed on the observed amorphous and crystalline regions to verify the spatial correspondence between "high radioactive element content" and "amorphous structure / specific defects" at the nanoscale.

[0024] Step 6: Data Integration and Mechanism Study. Integrate data from all the preceding steps: mineralogical statistics from Step 1, micro-area elemental distribution from Step 2, overall structural parameter changes from Step 3, and the correspondence between micro-area composition and structure from Step 5. Systematically construct a damage evolution model for radioactive elements in minerals: "existence form (isomorphic) → local lattice distortion / expansion → generation of microscopic defects → accumulation leading to amorphization." Based on this model, further comparative evaluations of the differences in radiation damage tolerance among different minerals can be conducted.

[0025] The beneficial effects of the technical solution of the present invention are as follows: (1) Achieving true “in-situ-correlation” analysis: Through FIB technology, the target micro-region locked by composition analysis (EMPA) and the observation area of ​​structure analysis (TEM) are physically and precisely unified for the first time, ensuring the spatial homology of elemental data and structural data, and the conclusions are more direct and reliable.

[0026] (2) A complete chain of evidence from the macroscopic to the atomic scale has been established: the method and process design starts from the macroscopic mineral distribution (micrometer level), gradually focuses on the micro-region composition (micrometer level), the overall crystal structure (cell level), and finally reaches the atomic arrangement and defects (angstrom level), forming a set of logically rigorous and scale-connected systematic research methods.

[0027] (3) It reveals microscopic inhomogeneities that are difficult to detect using traditional methods: Traditional XRD can only obtain average structural information. This invention, through HRTEM and SAED, directly reveals significant inhomogeneities at the nanoscale within minerals—that is, high-radioactive regions are completely amorphous, while low-radioactive regions still retain crystalline structures but with defects. This is crucial for understanding the mechanism of radiation damage to minerals.

[0028] (4) Wide range of applications: This method is not only applicable to zircon, but can also be extended to all minerals that may carry radioactive elements (such as pyrochlore, monazite, etc.), providing a powerful and refined technical means for the development of radioactive minerals, the assessment of the long-term stability of solidified nuclear waste, and the correction of radioisotope dating systems.

[0029] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0030] Figure 1 A general flowchart of one specific embodiment of the research method of the present invention is shown; Figure 2 Zircon grains with a ring-like structure are shown; Figure 3 The electron diffraction pattern of high uranium ring zones is shown; Figure 4 Zircon grains with uniform gray hue are shown; Figure 5 This shows the distribution of tiny grains in a uniform zircon amorphous matrix; Figure 6 This shows that the atomic structure near the dislocation lines of tiny grains is significantly distorted. Detailed Implementation

[0031] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0032] In the embodiments of the present invention, all the relevant devices used can be obtained commercially.

[0033] The overall workflow of the research method on the influence of radioactive elements on mineral crystal structure in this embodiment of the invention is as follows: Figure 1 .

[0034] Example 1: Analysis of zircon grains containing high-uranium zoning This case study aims to reveal the direct correlation between radioactive element enrichment zones (rings) within minerals and damage to their crystal structure.

[0035] Step 1: The raw radioactive polymetallic ore was crushed, graded, and prepared into slides. Using the AMICS system combined with SEM-EDS analysis, zircon was quickly identified as the main carrier mineral of uranium in the ore (accounting for 41.47% of the total uranium-bearing minerals), thus becoming the target mineral.

[0036] Step 2: In-situ quantitative analysis and surface scanning analysis of zircon were performed using EMPA and laser ablation inductively coupled plasma mass spectrometry (ICP-MS). The analysis revealed uneven uranium distribution on the zircon grain surface and the presence of distinct zoning structures. BSE images clearly showed a high-brightness zoning zone within each zircon grain. Figure 2 Quantitative analysis of the zonal ring revealed a UO2 content as high as 4.29%, significantly higher than that of standard zircon.

[0037] Step 3: The zircon grains with zonal structures were cut using FIB and subjected to SCXRD analysis. The results showed that their cell parameters (a=6.6210 Å, c=5.9984 Å, V=262.96 Å) were... 3 Compared to standard zircon (a=6.6003 Å, c=5.9765 Å, V=260.36 Å) 3 A systemic expansion occurs, with the volume increasing by approximately 1%.

[0038] Step 4: Target sample preparation was performed on the zircon grain. Based on the BSE image and U elemental distribution map from Step 2, further fine electron scanning was conducted to accurately locate the aforementioned high-uranium ring micro-region. Using a FIB system, in-situ cutting, extraction, and thinning were performed centered on this ring, ultimately preparing a transmission electron microscope thin section sample with a width of approximately 15 μm and a thickness of less than 100 nm, ensuring that the observation area was precisely the high-uranium ring.

[0039] Step 5: Observe the high-uranium ring-shaped micro-region thin film prepared in Step 4 under TEM: SAED analysis: The electron diffraction pattern obtained in this region is a broadened halo and diffuse rings ( Figure 3 This indicates that the high-uranium ring has become completely amorphous, losing its long-range ordered crystal structure. HRTEM verification: High-resolution images show no lattice fringes, further confirming its amorphous nature. Micro-area composition correlation: TEM-EDS confirms that the amorphous region has an abnormally high U content, establishing a spatial correspondence between "high uranium enrichment" and "complete amorphization".

[0040] Step 6: Combine the above data to form a complete chain of evidence: U 4+ Replace Zr in the form of isomorphism 4+ Entering the zircon lattice (Step 2 - EMPA data) → causing macroscopic expansion of the lattice (Step 3 - SCXRD data) → in the localized region (zone) of anomalously enriched uranium, lattice distortion accumulates to a critical point, leading to complete destruction of the crystal structure and the formation of an amorphous region (Step 5 - TEM data). This case is the first to directly link compositional anomalies with structural phase transitions within the same micrometer-scale zone.

[0041] Example 2: Analysis of uranium-bearing zircon grains without significant zoning This case study aims to demonstrate that even for seemingly homogeneous minerals, the method of this invention can reveal internal nanoscale damage inhomogeneities.

[0042] Steps 1 and 2: Same as in Example 1, uranium-bearing zircon was screened out. Through EMPA and BSE observation, a zircon grain with no visible zoning and relatively uniform backscattered grayscale was selected. Figure 4 The interior contains zircon fragments. Multi-point analysis of zircon fragment A shows that its UO2 content is about 0.5%, which is relatively uniformly distributed and obvious micron-sized enrichment areas were found.

[0043] Step 3: Same as in Example 1, single-crystal diffraction tests were performed on the uniform zircon particles. Data analysis showed that its unit cell parameters (a=6.6208 Å, c=5.9981 Å, V=262.92 Å) were... 3 Compared to standard zircon (a=6.6003 Å, c=5.9765 Å, V=260.36 Å), 3 A systemic expansion occurs, with the volume increasing by approximately 1%.

[0044] Step 4: Based on the results of Step 2, in order to investigate the microstructure of debris A under overall homogeneity, it was decided to prepare a transmission electron microscope sample spanning the interior of the mineral using FIB on the seemingly homogeneous debris A for observation.

[0045] Step 5: TEM observation revealed complex structures unpredictable at the micrometer scale: SAED survey: the diffraction pattern in most areas still showed diffuse rings, indicating that the matrix was highly amorphous. HRTEM fine observation: a small number of tiny grains with a size <10 nm were scattered within the amorphous matrix. Figure 5 These nanocrystals contain clear lattice fringes, but defects such as dislocations are visible. Figure 6 Composition and structure correlation: TEM-EDS showed that these residual nanocrystalline regions did not differ significantly in U content from the surrounding amorphous matrix, indicating that localized non-uniform recrystallization or the existence of anti-amorphization microregions occurred under a uniform radiation damage background.

[0046] Step 6: Data integration leads to the conclusion that in this type of uranium-bearing zircon, alpha decay damage has resulted in a high degree of overall mineral amorphization (Step 5 - SAED). However, localized residual or newly formed nanodomains exist within the amorphous matrix (Step 5 - HRTEM). These domains contain internal defects and are either "structural memory" remnants of severe lattice damage or products of later annealing. This indicates that the radiation damage and repair processes of the mineral coexist dynamically and are highly heterogeneous at the nanoscale, a phenomenon that traditional bulk analysis methods (such as XRD) cannot reveal.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for studying the influence of radioactive elements on mineral crystal structure, characterized in that, The method includes: Step 1: Sample preparation and target region screening: Prepare optical sheets from ore samples suitable for testing; Using an automated mineral analysis system combined with scanning electron microscopy and energy dispersive spectroscopy, the target mineral group containing radioactive elements was preliminarily delineated. Step 2: Characterization of the morphology and composition of the carrier minerals: In-situ quantitative analysis and surface scanning analysis of carrier minerals were performed using electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry. Backscattered electron imaging was used to identify the microstructural features of carrier minerals; By combining the microstructural characteristics of the carrier mineral, we can identify the microstructural features caused by elemental differences. Step 3: Overall structural analysis: The carrier mineral was cut and extracted using a focused ion beam system. The extracted carrier mineral particles were subjected to X-ray diffraction or single-crystal X-ray diffraction tests. Obtain the unit cell parameters and the trend of unit cell variation; Step 4: Precise micro-area localization and transmission electron microscopy sample preparation: Based on the data from step 2, focused ion beam sample preparation is performed targeting the region of interest; Regions of interest include regions enriched with radioactive elements and regions with characteristic structures; Step 5: Direct observation and correlation of atomic-scale microstructural damage: The sample prepared in step 4 was observed under a transmission electron microscope. The crystallization state was determined by selected area electron diffraction. The changes in the crystal structure of the carrier mineral were determined by analyzing the morphology and characteristics of the diffraction rings. Further high-resolution transmission electron microscopy imaging studies were conducted on regions that still retained crystal structure to identify crystal defects; In TEM mode, combined with energy dispersive spectroscopy, micro-area composition analysis was performed on the observed amorphous and crystalline regions to verify the spatial correspondence between "high radioactive element content" and "amorphous structure / specific defects" at the nanoscale. Step 6: Data Integration and Mechanism Study By integrating the data from all the aforementioned steps, a damage evolution model of radioactive elements in minerals is constructed, which follows the sequence of "occurrence form → local lattice distortion / expansion → generation of micro-defects → accumulation leading to amorphization".

2. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, The minerals mentioned are zircon, pyrochlore, monazite, rutile, calcite, apatite, epidote, or xenotime.

3. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 1, the automated mineral analysis system is AMICS or TIMA.

4. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 1, the radioactive element is at least one of U and Th.

5. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 2, in-situ quantitative micro-area analysis of the carrier mineral is performed using electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry to obtain the precise content, spatial distribution, and surface scan maps of major, minor, and trace elements.

6. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 2, the microstructural features include at least one of the following: rings, cracks, inclusions, irradiation halos, dissolution cavities, and twins.

7. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 3, the extracted carrier mineral particles are subjected to X-ray diffraction or single-crystal X-ray diffraction tests to obtain unit cell parameters, atomic occupancy, anisotropic displacement parameters and bond lengths.

8. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 4, the prepared sample is in the form of an ultrathin sheet or needle.

9. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, In step 5, the crystal defects to be investigated include at least one of dislocations, grain boundaries, stacking faults, and voids.

10. The method for studying the influence of radioactive elements on mineral crystal structure according to claim 1, characterized in that, Step 6, after establishing the damage evolution model of radioactive elements in minerals—"occurrence form → local lattice distortion / expansion → microscopic defect generation → accumulation leading to amorphization"—also includes: Further comparative evaluation of the differences in the tolerance of different minerals to radiation damage.

Images