Estimation method of granite-type uranium ore-forming temperature based on arsenic and selenium content of pyrite

Abstract

The application provides a method for estimating the temperature of the formation of a granite type uranium deposit based on the content of arsenic and selenium in pyrite, which comprises the following steps: firstly, collecting ore samples of the uranium deposit through field geological investigation; then, observing the ore samples under a microscope and analyzing the elements in the laboratory after processing the ore samples; and finally, processing the laboratory data and comprehensively estimating the temperature of the formation of the uranium deposit. The application has reasonable design and simple process, and is simple to operate and has low technical difficulty in estimating the temperature of the formation of the granite type uranium deposit, which is of great significance for deeply understanding the cause of the uranium deposit and predicting the prospect of the formation of the uranium deposit in the deep part.

Description

Technical Field

[0001] This invention belongs to the field of uranium mineralization theory and mineralization prediction technology, specifically involving a method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite. Background Technology

[0002] Ore-forming temperature is one of the fundamental topics in ore deposit geology. A reasonable determination of the ore-forming temperature not only helps in identifying the genetic type of the deposit but also in determining the depth of mineralization and further evaluating the prospective potential for deep exploration. Estimation of ore-forming temperature mainly includes qualitative methods based on alteration and mineralization mineral assemblages, and methods such as fluid inclusion microthermometry and estimation of the stable isotope equilibrium temperature of associated minerals. For granite-type uranium deposits in South China, previous researchers, based on fluid inclusion microthermometry results, have limited the main ore-forming temperature of such deposits to between 150℃ and 250℃. However, some scholars have proposed the existence of an early high-temperature stage of uranium mineralization, based on the presence of sericitization hydrothermal alteration associated with uranium mineralization. Therefore, the reasonable estimation of the ore-forming temperature of granite-type uranium deposits is an important fundamental issue. However, because the quartz mineral, a common vein mineral in granite-type uranium deposits, is mostly composed of very fine-crystalled crystals with high impurity content and poor transparency, it poses a significant challenge to estimating the ore-forming temperature using fluid inclusion microthermometry. Meanwhile, determining the primary and secondary inclusions in quartz and their relationship with uranium mineralization is quite difficult, further posing technical challenges to the application of fluid inclusion microthermography.

[0003] Pyrite is one of the most common metallic sulfides in various types of mineral deposits. Its wide distribution and diverse occurrence environments make it a valuable mineral for mineral deposit classification studies. Previous researchers have conducted extensive genetic and prospecting mineralogy studies on pyrite, summarizing a wealth of genetic information. Especially in the study of gold deposits, pyrite has played a crucial role, not only reflecting the genetic information of gold deposits but also indicating various prospecting information. In recent years, different scholars have proposed pyrite trace element content thermometers based on pyrite research, with the pyrite arsenic and selenium content thermometers being the most mature. However, the effectiveness of their application differs. The pyrite arsenic content thermometer has a larger error when the arsenic content is low, while the pyrite selenium content thermometer has a larger error when the selenium content is low. How to rationally use these two pyrite trace element content thermometers to estimate ore-forming temperatures remains an unsolved technical problem. Most granite-type uranium deposits contain pyrite from the same mineralization period. Using a thermometer to measure the arsenic and selenium content of pyrite to reasonably estimate the mineralization temperature will have important theoretical and practical significance for the study of granite-type uranium deposits and the evaluation of deep mineralization in such deposits.

[0004] Ore-forming temperature is a crucial parameter for determining the genesis of uranium deposits, tracing the source of ore-forming fluids, and rationally determining the age of ore formation. Existing research methods include qualitative estimation using alteration mineral assemblages, semi-quantitative estimation using fluid inclusion microthermometry, and quantitative estimation using mineral-to-isotope geothermometry. Qualitative estimation using mineral assemblages yields results with a wide temperature range and requires identification of hydrothermal alteration assemblages from the same ore-forming period, making it prone to misinterpretation during geological observation. Semi-quantitative estimation using fluid inclusion microthermometry requires strict definition of fluid inclusions from the same ore-forming period and revisions such as homogenization temperature and pressure corrections, making it significantly influenced by subjective factors. Mineral-to-isotope geothermometry requires determining mineral co-occurrence relationships and complex isotopic analysis, resulting in high costs and limitations in its application.

[0005] In conclusion, it is necessary to further innovate existing technologies. Summary of the Invention

[0006] To address the technical problems existing in the background art, this invention proposes a method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite. The method is reasonable in conception and simple in process. It is easy to operate and has low technical difficulty in estimating the mineralization temperature of granite-type uranium deposits. It is of great significance for a deeper understanding of the genesis of uranium deposits and for predicting the prospect of deep uranium mineralization.

[0007] To address the aforementioned technical problems, this invention provides a method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite. The method involves first conducting a field geological survey and collecting uranium deposit ore samples; then processing the uranium deposit ore samples and performing microscopic observation and laboratory elemental analysis; finally, processing the obtained laboratory data to comprehensively estimate the uranium mineralization temperature.

[0008] The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite specifically includes the following steps:

[0009] (1) Collect uranium ore samples from the deposit

[0010] Rich ore samples were collected from different uranium deposits, with a gamma intensity greater than 500 ur as the indicator;

[0011] (2) Sample processing

[0012] The collected rich ore samples were further crushed, and the structure and texture of the ore were observed in detail. A position perpendicular to the vein direction was selected, the rich ore samples were cut and ground, and probe slides without coverslips were made.

[0013] (3) Microscopic observation of samples to delineate pyrite from the same mineralization period.

[0014] The obtained probe slides were observed in detail under a polarizing and reflecting microscope to identify the petrographic relationship between pyrite and pitchblende, determine the pyrite from the same mineralization period and mark it, and determine the mineral composition on the probe slides.

[0015] (4) In-situ geochemical composition determination of pyrite micro-area

[0016] The elemental content of probe samples of pyrite from the same mineralization period was tested to obtain trace element geochemical composition data of pyrite from the same mineralization period at multiple test points.

[0017] (5) Data processing

[0018] For the obtained trace element geochemical composition data of pyrite from the same mineralization period in uranium deposit ore, the As and Se content temperatures of pyrite were calculated using pyrite As content thermometers and pyrite Se content thermometers, respectively. By plotting the As and Se content temperatures at the same pyrite analysis point, the distribution characteristics and consistency of the As and Se content temperature data at the same data point were compared to determine reasonable mineralization temperature data points. That is, whether the As and Se content temperatures at the same point are consistent. If they are basically consistent, it indicates that the estimated temperature is reasonable. If the difference is large, it reflects that at least one of the As and Se content temperatures is too high or too low, which is obviously unreasonable. Then, the corresponding mineralization temperature is estimated based on the temperature data where the As and Se content temperatures are basically consistent.

[0019] The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite, wherein: in step (1), attention should be paid to the characteristics of the hand specimen of ore when collecting samples, and ore samples containing pyrite should be collected.

[0020] The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite includes the following step (4): the elemental content of probe samples of pyrite from the same mineralization period can be tested using a laser ablation plasma mass spectrometer.

[0021] The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite includes the following step (4): electron probe microanalysis can be used to test the elemental content of probe samples of pyrite from the same mineralization period.

[0022] The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite includes the following: In step (4), before conducting elemental content testing, it is necessary to select test points, and when selecting test points, it is necessary to combine the printed reflective photographs to accurately locate pyrite particles from the same mineralization period and the parts that need to be analyzed and tested.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects:

[0024] This invention presents a reasonable and simple method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite. It is easy to operate, has low technical difficulty, and low economic cost for estimating the mineralization temperature of granite-type uranium deposits. It is of great significance for a deeper understanding of the genesis of uranium deposits and for predicting the prospect of deep uranium mineralization, and has broad application value. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This diagram illustrates the implementation steps of the method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite, as described in this invention.

[0027] Figure 2 This invention provides a method for estimating the mineralization temperature of granite-type uranium deposits based on arsenic and selenium content in pyrite, using typical uranium ore from the Zhangjia uranium deposit and characteristic images of pyrite from the same mineralization period. Figure 2 In the figure, Figure a shows uranium ore from the Zhangjia uranium deposit, and Figure b shows pyrite from the same mineralization period in the ore from the Zhangjia uranium deposit.

[0028] Figure 3 This is an example diagram showing the arsenic and selenium content data and temperature calculations of pyrite from the same mineralization period involved in the method for estimating the mineralization temperature of granite-type uranium deposits based on arsenic and selenium content in pyrite, as described in this invention. Figure 3 Arsenic and selenium content is expressed in wt%, and temperature is expressed in °C.

[0029] Figure 4 This is a comparison chart of pyrite arsenic content temperature and selenium content temperature involved in the method for estimating the mineralization temperature of granite-type uranium deposits based on pyrite arsenic and selenium content in this invention. Detailed Implementation

[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The present invention will be further explained below with reference to specific embodiments.

[0032] This embodiment provides a method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite. The method involves first conducting a field geological survey and collecting uranium deposit ore samples; then processing the samples and performing microscopic observation and laboratory elemental analysis; finally, calculating and mapping the obtained laboratory data to comprehensively estimate the uranium mineralization temperature.

[0033] The specific steps are as follows:

[0034] S010. Collect uranium ore samples from the deposit.

[0035] Collect typical ore samples of the target uranium deposit from different uranium deposits (such as in mine or exploration tunnels, ore piles, trenches, and brick holes), using high radioactivity and high grade (gamma intensity greater than 500 ur) as indicators, which is beneficial for subsequent sample processing and microscopic observation. When collecting samples, in addition to collecting high-grade primary uranium ore containing pyrite and pitchblende as much as possible, attention should also be paid to the characteristics of hand specimens of ore, and attention should be paid to collecting ore samples that also contain pyrite.

[0036] S020, Sample Processing

[0037] The collected uranium ore samples were further crushed (using a geological hammer to strike them, and observing the fresh cross-section of the rich ore after crushing). The structure and texture of the ore were observed in detail with the naked eye. A section perpendicular to the vein was selected and cut and ground to make a probe slide without a cover glass. The standard dimensions were 5cm in length, 2.5cm in width, and 2mm in thickness. The thickness of the rich ore slice was 0.03mm.

[0038] S030. Microscopic observation of samples to delineate pyrite from the same mineralization period.

[0039] The prepared probe slides were subjected to petrographic observation under a polarizing and reflecting microscope to determine the petrographic relationship between pyrite and primary mineralized pitchblende (i.e., the relationship between pitchblende and pyrite, and to find evidence that proves that the two crystallized at the same time). Pyrite from the same mineralization period was identified, that is, pyrite containing pitchblende inclusions and occurring as a co-occurring mineral with pitchblende in the same hydrothermal vein. The locations of the pyrite from the same mineralization period were marked on the probe slide with a marker pen for in-situ composition analysis in micro-areas without damaging the overall rock structure. The mineral composition was then determined directly on the probe slide using analytical methods.

[0040] S040, in-situ geochemical composition determination of pyrite micro-areas

[0041] For probe samples of pyrite from the same mineralization period, in-situ micro-area testing and analysis of pyrite was performed using laser ablation plasma mass spectrometry (LA-ICP-MS) or electron probe microanalysis (EPMA) to obtain trace element geochemical composition data of pyrite from the same mineralization period at multiple test points (a single analysis can provide data on the content of multiple trace elements, including arsenic and selenium).

[0042] Before conducting elemental content testing, it is necessary to select test sites. When selecting test sites, it is necessary to combine the printed reflective photographs to accurately locate pyrite particles from the same mineralization period and the parts that need to be analyzed and tested.

[0043] S050, Data Processing

[0044] For the trace element geochemical composition data of pyrite from the same mineralization period obtained from uranium deposit ore, the arsenic and selenium content temperatures in pyrite were measured using pyrite As content thermometers and pyrite Se content thermometers, respectively. By plotting the As and Se content temperatures at the same pyrite analysis point and comparing their distribution characteristics and consistency, reasonable mineralization temperature data points were determined. Specifically, whether the As and Se content temperatures at the same point are consistent was considered. If they are basically consistent, the estimated temperature is reasonable; if they differ significantly, it indicates that at least one of the As or Se content temperatures is too high or too low, which is obviously unreasonable. Based on the temperature data where the As and Se content temperatures are basically consistent, the corresponding mineralization temperature was estimated.

[0045] Example 1

[0046] The following example, using the estimation of the mineralization temperature of the Zhangjia uranium deposit in Ziyuan County, Guangxi, further describes the present invention:

[0047] like Figure 1 As shown, the method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite in Embodiment 1 of the present invention specifically includes the following steps:

[0048] S110, Sample Collection

[0049] Geologists visited the Zhangjia uranium deposit in Ziyuan County, Guangxi Province, and collected typical uranium ore samples. Figure 2 a) The ore is required to have a high uranium content, containing primary pitchblende mineralization and pyrite. Some ore samples, after being crushed, show pitchblende and pyrite on the fracture surface.

[0050] S120, Sample Processing

[0051] The uranium ore samples were further examined visually. Then, perpendicular to the vein, the samples were cut and ground to create probe slides. Cutting perpendicular to the vein aims to include mineralization information from different parts of the vein's cross-section, including structural changes and distribution of minerals from the vein wall inwards. This facilitates more comprehensive information on mineral coexistence during microscopic petrographic observation. The prepared probe slides serve two purposes: first, they can be used for microscopic observation, particularly for observing the petrographic relationship between pitchblende and pyrite under a reflecting microscope; second, they can be directly applied to laser ablation analysis and electron probe microanalysis for quantitative elemental analysis, directly obtaining in-situ elemental content data for micro-areas of the minerals.

[0052] S130, Sample Observation Marks

[0053] The probe slides of the prepared typical uranium ore samples were observed under a microscope, mainly focusing on the pitchblende vein portion, paying attention to the relationship between pitchblende and pyrite, and identifying pyrite from the same mineralization period. Figure 2 (b, c, d) were marked to facilitate in-situ laser or electron probe microanalysis. Two different occurrence states of pyrite from the same mineralization period were observed in this study. Figure 2 (b) One type is pyrite associated with fluorite-pitchblende, and the other type is pyrite associated with sericite-pitchblende. Figure 2 (c, d). Due to the large magnification of laser in-situ micro-area analysis, to facilitate the location of analysis points, reflective images of the delineated pyrite sites of the same mineralization period at different magnifications can be taken under a microscope. The analysis points can then be organized and printed according to magnification from small to large for subsequent electron probe microanalysis.

[0054] S140, Laboratory Analysis and Testing

[0055] For probe slides delineating pyrite from the same mineralization period, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) or electron probe microanalysis (EPMA) were used for testing to obtain trace element composition data for pyrite from the same mineralization period. When selecting the points to be analyzed, it is necessary to accurately locate the pyrite particles from the same mineralization period and the areas to be analyzed, based on the printed reflective image. This example uses electron probe microanalysis (EPMA); the operation was repeated multiple times to obtain trace element composition data of pyrite from different uranium deposits from the same mineralization period. Figure 3 ).

[0056] S150, Data Mapping and Recognition

[0057] The temperatures of arsenic and selenium content in pyrite from the same mineralization period of the Zhangjia uranium deposit were plotted. Reasonable temperature estimation data points were determined based on the differences and consistency of arsenic and selenium content temperatures obtained from the same point in the same mineralization period.

[0058] exist Figure 4 In the graph, the horizontal axis represents the temperature of pyrite selenium content, and the vertical axis represents the temperature of pyrite arsenic content. The diagonally dark area represents the region where the temperatures of pyrite selenium and pyrite arsenic content are essentially the same, and the central black line represents the line where they are completely equal. Considering the error between different thermometers, a range of 50°C above and below is set as an acceptable error range, meaning the area between the upper and lower black lines represents the region where the temperatures of pyrite selenium and pyrite arsenic content are essentially the same. The graph shows that five points of the arsenic content temperature in sericite-symbiotic pyrite are above the gray area, indicating that the arsenic content temperature has been overestimated; one point of the arsenic content temperature in sericite-symbiotic pyrite is below the gray area, indicating that the arsenic content temperature has been underestimated. The remaining two temperature points in sericite-symbiotic pyrite are within the gray area, indicating that the temperatures of pyrite selenium and pyrite arsenic content are essentially the same, indicating high reliability. Similarly, for fluorite-associated pyrite, one data point above the gray area indicates an overestimation of arsenic content temperature; three data points below the gray area indicate an underestimation of arsenic content temperature; and nine points within the gray area indicate that the selenium content temperature and arsenic content temperature of pyrite are basically consistent, demonstrating high reliability. The pyrite data points within the black area are considered reasonable uranium mineralization temperatures. It is evident that sericite-associated pyrite and its corresponding uranium mineralization temperatures are relatively high, exceeding 400℃; while fluorite-associated pyrite and its corresponding uranium mineralization temperatures are relatively low, approximately 200±50℃, showing good consistency with previous estimates of 150℃-250℃ for granite-type uranium mineralization temperatures.

[0059] Therefore, the method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite proposed in this embodiment not only has good consistency with the relevant results of previous studies, but also clearly demonstrates the existence of uranium mineralization in the high-temperature stage. It is a practical and reasonable method for estimating uranium mineralization temperature.

[0060] Through the study of the Zhangjia uranium deposit in Ziyuan County, Guangxi, pyrite from the same mineralization period was identified, and the trace element content of pyrite was analyzed. The temperatures at which arsenic and selenium contents of pyrite from the same mineralization period were calculated. By comparing the temperature differences of arsenic and selenium contents at the same analysis point, a method for reasonably estimating the mineralization temperature of granite-type uranium deposits was designed using a combined pyrite arsenic and selenium content thermometer.

[0061] This invention has a reasonable concept and a simple process. It is easy to operate and has low technical difficulty in estimating the mineralization temperature of granite-type uranium deposits. It is of great significance for a deeper understanding of the genesis of uranium deposits and for predicting the prospect of deep uranium mineralization.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite, characterized in that: First, a field geological survey was conducted to collect uranium ore samples. Then, the uranium ore samples were processed and subjected to microscopic observation and laboratory elemental analysis. Next, the obtained laboratory data were processed to comprehensively estimate the uranium mineralization temperature. Specifically, the following steps are included: (1) Collect uranium deposit ore samples Rich ore samples were collected from different uranium deposits, with an equivalent uranium content greater than 500 Ur as the indicator; (2) Sample processing The collected rich ore samples were further crushed, and the structure and texture of the ore were observed in detail. A position perpendicular to the vein direction was selected, the rich ore samples were cut and ground, and probe slides without coverslips were made. (3) Microscopic observation of samples to delineate pyrite from the same mineralization period. The obtained probe slides were observed in detail under a polarizing and reflecting microscope to identify the petrographic relationship between pyrite and pitchblende, determine the pyrite from the same mineralization period and mark it, and determine the mineral composition on the probe slides. (4) In-situ geochemical composition determination of pyrite micro-area The elemental content of probe samples of pyrite from the same mineralization period was tested to obtain trace element geochemical composition data of pyrite from the same mineralization period at multiple test points. (5) Data processing For the obtained trace element geochemical composition data of pyrite from the same mineralization period in uranium deposit ore, the As and Se content temperatures of pyrite were calculated using pyrite As content thermometers and pyrite Se content thermometers, respectively. By plotting the As and Se content temperatures at the same pyrite analysis point, the distribution characteristics and consistency of the As and Se content temperature data at the same data point were compared to determine reasonable mineralization temperature data points. That is, whether the As and Se content temperatures at the same point are consistent. If they are basically consistent, it indicates that the estimated temperature is reasonable. If the difference is large, it reflects that at least one of the As and Se content temperatures is too high or too low, which is obviously unreasonable. Then, the corresponding mineralization temperature is estimated based on the temperature data where the As and Se content temperatures are basically consistent.

2. The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite as described in claim 1, characterized in that: In step (1), attention should be paid to the characteristics of the ore hand specimen when collecting samples, and ore samples containing pyrite should be collected.

3. The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite as described in claim 1, characterized in that: In step (4), the elemental content of the probe sample of pyrite from the same mineralization period is tested using a laser ablation plasma mass spectrometer.

4. The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite as described in claim 1, characterized in that: Step (4) also employs electron probe microanalysis to test the elemental content of probe samples of pyrite from the same mineralization period.

5. The method for estimating the mineralization temperature of granite-type uranium deposits based on the arsenic and selenium content of pyrite as described in claim 1, characterized in that: Before conducting elemental content testing, step (4) requires selecting test sites. When selecting test sites, it is necessary to combine the printed reflective photographs to accurately locate pyrite particles from the same mineralization period and the parts that need to be analyzed and tested.

Images