Method for judging participation of submarine exhalation hydrothermal fluid in rock-forming process of black rock series

Abstract

The present application relates to the technical field of uranium ore, in particular to a method for judging the participation of submarine exhalative hydrothermal fluid in the rock-forming process of black rock series, comprising the following steps: step 1, collecting black rock series samples; step 2, sample preparation and analysis testing; step 3, scanning electron microscope observation of black rock series samples; step 4, biological hot water action judgment; and step 5, isotopic tracing judgment. The present application combines modern element content testing means, isotopic tracing means, biological hot water discrimination means and traditional geological work, extracts key elements, establishes a flow-based discrimination basis, and judges whether the black rock series in the target area has the participation of submarine exhalative hydrothermal fluid, thereby improving the ore prospecting efficiency in the black rock series, reducing large-scale construction exploration, and saving funds and time.

Description

Technical Field

[0001] This invention relates to the field of uranium mining technology, specifically to a method for determining the participation of submarine hydrothermal vents in the formation of black rock formations. Background Technology

[0002] Black rock formations are among the most important deposits of rare metals, non-metals, and oil and gas energy worldwide. They contain vital strategic resources of rare elements ("three rare elements"), essential "vitamins" for national defense and development. While widely distributed from North America to Eurasia, and extensively belted in Guizhou, Qinghai, Hunan, Jiangxi, Xinjiang, Tibet, and Zhejiang provinces in my country, relatively few black rock formations possess uranium polymetallic mineralization potential. A crucial prerequisite for uranium polymetallic mineralization in black rock formations is the involvement of hydrothermal fluids from the seabed during their formation. Only in this way can platinum group elements, rare earth elements, phosphorus, vanadium, nickel, molybdenum, and uranium from deep within the Earth be transported by hydrothermal fluids to shallower regions, where they precipitate and crystallize, forming mineral resources within the black rock formations.

[0003] Therefore, it is necessary to design a method to determine whether submarine hydrothermal vents were involved in the formation of black rock formations, so as to improve the technical efficiency of quickly screening black rock formations with uranium polymetallic mineralization potential in existing technologies. Summary of the Invention

[0004] This invention presents a method for determining the participation of submarine hydrothermal vents in the diagenesis of black rock formations, which aims to solve the technical problem of improving mineral exploration efficiency in black rock formations, reducing large-scale construction exploration, and saving exploration costs and time.

[0005] The technical solution of the present invention:

[0006] A method for determining the involvement of submarine hydrothermal vents in the diagenesis of black rock formations includes the following steps:

[0007] Step 1: Collection of samples from the black rock formation;

[0008] Step 2: Sample preparation and analysis;

[0009] Step 3: Scanning electron microscopy observation of black rock samples;

[0010] Step 4: Determining the effect of biothermal water;

[0011] Step 5: Isotope tracing determination.

[0012] According to claim 1, a method for determining the participation of submarine hydrothermal vents in the formation of black rock formations is characterized in that: step 1, black rock formation sample collection, includes: selecting the black rock formation strata to be determined, and collecting a rock sample weighing 500 grams or more at every 3 cm thickness from bottom to top in a direction perpendicular to the bedding of the black rock formation. The sample must be collected from a newly exposed surface of the rock to ensure that the rock sample has not been subjected to severe weathering.

[0013] Step 2, sample preparation and analysis, including:

[0014] Step 2.1: Take the sample from Step 1 and slice it to make a thin slice with a thickness of 0.3 mm. Make at least 2 thin slices for each sample. Keep the remaining part of each sample slice for subsequent operations.

[0015] Step 2.2: Crush the remaining portion of each sample slice from Step 2.1 to 200 mesh;

[0016] Step 2.3: Take 50 grams of sample powder from each sample and use a plasma mass spectrometer to determine the Ba element content in each sample;

[0017] Step 2.4: Take 50 grams of sample powder from each sample and use an X-ray fluorescence spectrometer to determine the SiO2 and Al2O3 content. Calculate the SiO2 / Al2O3 ratio for each sample based on the measurement results.

[0018] Step 2.5, Isotope determination: Take 50 grams of sample powder from each sample and use a MAT-253 gas isotope mass spectrometer to determine the δ13C isotope in each sample.

[0019] Step 3, the scanning electron microscopy observation of the black rock series samples, includes: using a scanning electron microscope to perform mapping operations on the thin sections prepared in step 2.1, and performing surface scanning observation of the two elements Se and Ir. Samples containing Se and Ir are divided into group A, where only one or both of the two elements Se and Ir are observed and they are classified into group A. Samples where neither of these two elements is observed are recorded as group B.

[0020] Step 4: Determining the biothermal effect, including:

[0021] Now, the samples in Group A of Step 3 need to be evaluated. This requires the Ba content and SiO2 / Al2O3 ratio of each sample obtained from the tests and calculations in Step 2. Samples in Group A with Ba content ≥ 500 × 10-6 and SiO2 / Al2O3 ratio ≥ 4.5 are selected and classified as Group I. The remaining samples are classified as Group II. At this point, it can be determined that the black rock formation in the area where the Group I samples were collected had the participation of submarine hydrothermal activity during the sedimentary formation process, and has extremely high uranium polymetallic mineralization potential. The samples in Group II are pending further investigation.

[0022] The samples in group B from step 3 are now being evaluated. Samples in group B that meet either the requirement of Ba content ≥ 500 × 10⁻⁶ or SiO₂ / Al₂O₃ ratio ≥ 4.5 are classified into group III for future use. If the Ba content in the sample is < 500 × 10⁻⁶ and the SiO₂ / Al₂O₃ ratio is < 4.5, the sample is classified into group IV. It is also determined that the black rock formation in the area where the samples in group IV were collected did not involve hydrothermal activity from the seafloor during the sedimentary formation process, and therefore has very low mineral exploration value.

[0023] According to claim 5, a method for determining the participation of submarine hydrothermal vents in the diagenesis of black rock formations is characterized in that: step 5, isotope tracing determination, includes:

[0024] Now, isotope tracing is performed on the samples from Group II and Group III in step 4. The isotope values ​​obtained in step 2 are required. Samples from Group II and Group III with -2.8‰≥δ13C≥-8.9‰ are assigned to Group V, and the remaining samples are assigned to Group VI. At this point, it can be concluded that the black rock formation in the area where the Group V samples were collected had the participation of submarine hydrothermal activity during the sedimentary formation process, and has extremely high mineralization value.

[0025] The black rock formations in the area where Group VI samples were collected did not involve hydrothermal activity from the seafloor during their depositional formation, and therefore have very low mineral exploration value, so no further work is necessary.

[0026] The beneficial effects of this invention are:

[0027] This invention combines modern elemental content testing methods, isotope tracing methods, biothermal water identification methods, and traditional geological work to extract key elements, establish a standardized identification process, and determine whether there is submarine hydrothermal activity in the black rock formations of the target area. This improves the efficiency of mineral exploration in black rock formations, reduces large-scale construction exploration, and saves money and time.

[0028] This invention is based on 25,000 sets of black rock samples collected from eight countries and regions around the world, including Jordan, Saudi Arabia, Canada, Russia, and China. It integrates multi-directional geological research approaches and extracts key elements. The judgment process designed in this method can quickly and efficiently screen out black rock areas that have been involved in the deposition process by submarine hydrothermal activity from the widely distributed black rock systems around the world. Then, focus on mineral exploration work, reducing drilling and deep well exploration work by more than 80%, minimizing the environmental damage caused by conventional exploration, and saving time and money.

[0029] This invention boasts broad coverage, high effectiveness, and strong applicability, and can be effectively extended to the entire geosciences field. Its innovation lies in integrating multiple disciplines, including geology, geochemistry, isotope tracing, and electron microscopy, along with various advanced instrumental observation methods. Simultaneously, it eliminates minor interfering factors, providing grouped, streamlined, and intuitive conclusions. The method developed using this invention for determining whether submarine hydrothermal activity was involved in the formation of black rock formations has been validated in large-scale black rock formations in northern Saudi Arabia from 2019 to 2022. A total of 107 black rock formations, covering an area of ​​538 km², were identified in northern Saudi Arabia where submarine hydrothermal activity was involved in the sedimentary process. 2 Further targeted uranium exploration was conducted in these 107 areas, with 83 areas yielding mineralized deposits, representing a mineralization rate of 77.6%. The highest uranium content reached 10122 × 10⁻⁶. -6 This has led to a major breakthrough in the exploration of uranium polymetallic deposits in the black rock series in northern Saudi Arabia. Detailed Implementation

[0030] The following describes in detail, with reference to embodiments, a method for determining the participation of submarine hydrothermal fluids in the diagenesis of black rock formations according to the present invention.

[0031] A method for determining the involvement of submarine hydrothermal vents in the diagenesis of black rock formations includes the following steps:

[0032] Step 1: Collection of samples from the black rock formation;

[0033] Step 2: Sample preparation and analysis;

[0034] Step 3: Scanning electron microscopy observation of black rock samples;

[0035] Step 4: Determining the effect of biothermal water;

[0036] Step 5: Isotope tracing determination.

[0037] According to claim 1, a method for determining the participation of submarine hydrothermal vents in the formation of black rock formations is characterized in that: step 1, black rock formation sample collection, includes: selecting the black rock formation strata to be determined, and collecting a rock sample weighing 500 grams or more at every 3 cm thickness from bottom to top in a direction perpendicular to the bedding of the black rock formation. The sample must be collected from a newly exposed surface of the rock to ensure that the rock sample has not been subjected to severe weathering.

[0038] Step 2, sample preparation and analysis, including:

[0039] Step 2.1: Take the sample from Step 1 and slice it to make a thin slice with a thickness of 0.3 mm. Make at least 2 thin slices for each sample. Keep the remaining part of each sample slice for subsequent operations.

[0040] Step 2.2: Crush the remaining portion of each sample slice from Step 2.1 to 200 mesh;

[0041] Step 2.3: Take 50 grams of sample powder from each sample and use a plasma mass spectrometer to determine the Ba element content in each sample;

[0042] Step 2.4: Take 50 grams of sample powder from each sample and use an X-ray fluorescence spectrometer to determine the SiO2 and Al2O3 content. Calculate the SiO2 / Al2O3 ratio for each sample based on the measurement results.

[0043] Step 2.5, Isotope determination: Take 50 grams of sample powder from each sample and use a MAT-253 gas isotope mass spectrometer to determine the δ13C isotope in each sample.

[0044] Step 3, the scanning electron microscopy observation of the black rock series samples, includes: using a scanning electron microscope to perform mapping operations on the thin sections prepared in step 2.1, and performing surface scanning observation of the two elements Se and Ir. Samples containing Se and Ir are divided into group A, where only one or both of the two elements Se and Ir are observed and they are classified into group A. Samples where neither of these two elements is observed are recorded as group B.

[0045] Step 4: Determining the biothermal effect, including:

[0046] Now, the samples in Group A of Step 3 need to be evaluated. This requires the Ba content and SiO2 / Al2O3 ratio of each sample obtained from the tests and calculations in Step 2. Samples in Group A with Ba content ≥ 500 × 10-6 and SiO2 / Al2O3 ratio ≥ 4.5 are selected and classified as Group I. The remaining samples are classified as Group II. At this point, it can be determined that the black rock formation in the area where the Group I samples were collected had the participation of submarine hydrothermal activity during the sedimentary formation process, and has extremely high uranium polymetallic mineralization potential. The samples in Group II are pending further investigation.

[0047] The samples in group B from step 3 are now being evaluated. Samples in group B that meet either the requirement of Ba content ≥ 500 × 10⁻⁶ or SiO₂ / Al₂O₃ ratio ≥ 4.5 are classified into group III for future use. If the Ba content in the sample is < 500 × 10⁻⁶ and the SiO₂ / Al₂O₃ ratio is < 4.5, the sample is classified into group IV. It is also determined that the black rock formation in the area where the samples in group IV were collected did not involve hydrothermal activity from the seafloor during the sedimentary formation process, and therefore has very low mineral exploration value.

[0048] According to claim 5, a method for determining the participation of submarine hydrothermal vents in the diagenesis of black rock formations is characterized in that: step 5, isotope tracing determination, includes:

[0049] Now, isotope tracing is performed on the samples from Group II and Group III in step 4. The isotope values ​​obtained in step 2 are required. Samples from Group II and Group III with -2.8‰≥δ13C≥-8.9‰ are assigned to Group V, and the remaining samples are assigned to Group VI. At this point, it can be concluded that the black rock formation in the area where the Group V samples were collected had the participation of submarine hydrothermal activity during the sedimentary formation process, and has extremely high mineralization value.

[0050] The black rock formations in the area where Group VI samples were collected did not involve hydrothermal activity from the seafloor during their depositional formation, and therefore have very low mineral exploration value, so no further work is necessary.

[0051] Example

[0052] The invention will be further explained in detail below using the black rock formations developed in northern Saudi Arabia as an example.

[0053] Step 1: Sample collection was first carried out in three areas in northern Saudi Arabia where black rock formations are developed: Anir, Muhaly, and Al-Jonf. A rock sample weighing 500 grams or more was collected from bottom to top every 3 cm of thickness, perpendicular to the bedding plane of the black rock formations. The samples were collected from newly exposed surfaces to ensure that the rock samples had not been subjected to severe weathering. Depending on the size and thickness of the rock layers, 28 samples were collected from Anir, 37 from Muhaly, and 25 from Al-Jonf.

[0054] Step 2:

[0055] Operation 1: Prepare thin sections for each collected sample. At least two thin sections should be prepared for each sample. If the budget is sufficient, the number of thin sections prepared for each sample can be increased to three or four to ensure that the scanning electron microscope in step 3 can observe more detailed internal rock features and reduce misjudgments due to accidental errors. A total of 206 thin sections were prepared in this work, and four thin sections were prepared for some key samples.

[0056] Operation 2: Grind each remaining sample from Operation 1 to 200 mesh, and the weight of the powder from each sample should not be less than 250 grams.

[0057] Operation 3: Take 50 grams of sample powder from each sample and use an inductively coupled plasma mass spectrometer to determine the Ba content in each sample according to GBT 14506.30-2010 "Methods for Chemical Analysis of Silicate Rocks Part 30: Determination of 44 Elements". The test results are shown in column 6 of Table 1.

[0058] Operation 4: Take 50 grams of sample powder from each sample and determine the SiO2 and Al2O3 contents using X-ray fluorescence spectrometry according to GB / T 14506.28-2010 "Chemical Analysis Methods for Silicate Rocks Part 28: Determination of 16 Major and Minor Components". Calculate the SiO2 / Al2O3 ratio for each sample based on the measurement results. The ratio results are shown in column 7 of Table 1.

[0059] Operation 5: Take 50 grams of sample powder from each sample and determine the δ13C isotope in each sample using a MAT-253 gas isotope mass spectrometer according to DZ / T 0184.17-1997 "Determination of Carbon and Oxygen Isotope Composition in Carbonate Minerals or Rocks by Phosphoric Acid Method". The determination results are shown in column 9 of Table 1.

[0060] Table 1. Discrimination factors for submarine hydrothermal vents in black rock samples.

[0061]

[0062]

[0063] Step 3: Perform elemental surface scanning on the thin sections prepared in Step 2, Operation 1, using a scanning electron microscope (SEM). Focus on observing the presence of Se (Se) and Ir (Ir). Elemental surface scanning ensures that no area is missed in each thin section. Se and Ir were chosen because Se is a core-affinity element, with a much higher concentration in the core than in the crust. The core contains approximately 40 × 10⁻⁶ Se, while the crust contains only 0.08 × 10⁻⁶. Ir is similar to Se; it is siderophile and has a high density. Its concentration in the Earth's depths is much higher than in the crust, making it a typical deep-source element. The presence of Se or Ir in rocks strongly suggests that the rocks were mixed with material upwelling from deep within the Earth during sedimentation. Through surface scanning of Se and Ir, 55 out of 90 samples from three regions were found to contain Se or Ir, and these were classified as Group A. The remaining 35 samples were classified as Group B.

[0064] Step 4: Further analysis of the A and B groups of samples separated in Step 3 using elemental surface scanning was conducted using elemental geochemistry and biogeochemistry, focusing on the trace element Ba and the major element SiO2 / Al2O3 ratio. The Ba content in deep-sea hydrothermal vents is significantly higher than that in normal seawater. While the Ba content in normal seawater sediments typically does not exceed 70 × 10⁻⁶, the Ba content in sediments formed by deep-sea hydrothermal vents is usually greater than 500 × 10⁻⁶, indicating a substantial difference in geochemical characteristics between the two. On the other hand, seawater mixed with hydrothermal vents from the ocean floor will experience an extraordinary abundance of marine life, mainly due to the following two factors: first, the high-temperature hydrothermal vents continuously erupting from the Earth's depths can raise the temperature of the seawater near the vent, which is conducive to biological growth; second, the hydrothermal vents from the Earth's depths contain a large amount of trace elements such as P, Ca, Cu, and Zn, which are necessary for biological reproduction. Therefore, while the above factors cause a large accumulation of marine life, they also leave biogeochemical traces in the black rock formations formed by sedimentation. Here, the SiO2 / Al2O3 ratio, a major element parameter, is selected to judge the biochemical characteristics affected by hydrothermal vents. When SiO2 / Al2O3 ≥ 4.5, it is determined that biothermal activity was involved in the sedimentation process of the rocks.

[0065] Based on the above approach, the samples from groups A and B separated in step 3 were evaluated. Of the 55 samples in group A, 8 samples with Ba content ≥ 500 × 10⁻⁶ and SiO₂ / Al₂O₃ ratio ≥ 4.5 were classified as group I. At this point, it can be determined that the black rock formations represented by these 8 samples in the sampling area underwent hydrothermal activity during sedimentation, exhibiting extremely high uranium polymetallic mineralization potential, warranting further exploration efforts. The remaining 47 samples were classified as group II.

[0066] In Group B, 13 samples with Ba content ≥ 500 × 10⁻⁶ or SiO₂ / Al₂O₃ ratio ≥ 4.5 were assigned to Group III. The remaining 22 samples with Ba content < 500 × 10⁻⁶ and SiO₂ / Al₂O₃ ratio < 4.5 were assigned to Group IV. It was determined that the black rock formations represented by the samples in Group IV did not involve hydrothermal activity from submarine vents during their depositional formation, and therefore have very low mineral exploration value. Further exploration efforts can be reduced, and the focus can be shifted to areas with greater mineralization potential.

[0067] Step 5: Isotope tracing was used on samples from Groups II and III separated in Step 4 to further determine whether hydrothermal activity from deep-sea vents was involved in their formation. δ¹³C isotopes exhibit significant fractionation in different geological bodies. Therefore, based on the fractionation differences of δ¹³C between geological bodies, combined with the aforementioned parameters, it can be determined which of the following water sources—seawater, atmospheric water, terrestrial geysers, or deep-sea hydrothermal fluids—was involved in the sedimentary formation of the rock. When -2.8‰ ≥ δ¹³C ≥ -8.9‰, it represents the distribution range of deep-source C isotopes on Earth. Only through deep-sea hydrothermal activity could these be brought to the Earth's surface and deposited in rocks. Four samples from Groups II and III with -2.8‰ ≥ δ¹³C ≥ -8.9‰ were assigned to Group V, and the remaining 56 samples were assigned to Group VI. Based on this assessment, it can be concluded that the black rock formations in the sampling area represented by Group V exhibited significant uranium polymetallic mineralization potential due to the involvement of submarine hydrothermal vents during sedimentation. Further exploration efforts can be intensified. Conversely, the black rock formations in the sampling area represented by Group VI lacked such involvement during sedimentation, indicating very low mineralization value. Therefore, exploration efforts should be reduced, and the focus should be shifted to areas with greater mineralization potential.

[0068] Based on the above assessment, a total of 12 samples were identified as involving hydrothermal activity from submarine vents. Subsequently, based on the collection locations of these 12 samples, six target areas with extremely high uranium polymetallic exploration potential were delineated in the Anir, Muhal, and Cl-Jonf regions. These six target areas were then explored in accordance with the nuclear industry standard specification "Technical Guidelines for Prediction and Evaluation of Unconventional Uranium Resources in Black Rock Series". Uranium deposits were found in five of these areas, with an encounter rate of 83%. The highest U content was 10122×10⁻⁶, and the average content was 673×10⁻⁶, which is 6.73 times the average content specified by the nuclear industry standard.

[0069] The above-mentioned invention method not only achieves good results in identifying submarine hydrothermal vents and exploring uranium polymetallic deposits in black rock formations, but also reduces drilling and deep well exploration work by more than 80%, making it highly efficient, environmentally friendly, and saving time and money.

[0070] The embodiments of the present invention have been described in detail above. The present invention is not limited to the above examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for determining the participation of submarine hydrothermal vents in the diagenesis of black rock formations, characterized in that, Includes the following steps: Step 1: Collection of samples from the black rock formation; Step 2: Sample preparation and analysis; Step 3: Scanning electron microscopy observation of black rock samples; Step 4: Determining the effect of biothermal water; Step 5: Isotope tracing and determination; Step 1, the collection of black rock samples, includes: selecting the black rock strata that need to be assessed, and collecting a rock sample weighing 500 grams or more from bottom to top every 3 cm in a direction perpendicular to the bedding of the black rock strata. The sample must be collected from the newly exposed surface of the rock to ensure that the rock sample has not been subjected to severe weathering. Step 2, sample preparation and analysis, including: Step 2.1: Take the sample from Step 1 and slice it to make a thin slice with a thickness of 0.3 mm. Make at least 2 thin slices for each sample. Keep the remaining part of each sample slice for subsequent operations. Step 2.2: Crush the remaining portion of each sample slice from Step 2.1 to 200 mesh; Step 2.3: Take 50 grams of sample powder from each sample and use a plasma mass spectrometer to determine the Ba element content in each sample; Step 2.4: Take 50 grams of sample powder from each sample and use an X-ray fluorescence spectrometer to determine the SiO2 and Al2O3 content. Calculate the SiO2 / Al2O3 ratio for each sample based on the measurement results. Step 2.5, Isotope determination: Take 50 grams of sample powder from each sample and use a MAT-253 gas isotope mass spectrometer to determine the δ¹⁸O₂ content in each sample. 13 C isotope determination; Step 3, the scanning electron microscopy observation of the black rock series samples, includes: using a scanning electron microscope to perform mapping operations on the thin sections prepared in step 2.1, and performing surface scanning observation of the two elements Se and Ir. Samples containing Se and Ir are divided into group A. If only one or both of the two elements Se and Ir are observed, they can be classified into group A. Samples without the observation of these two elements are recorded as group B. Step 4: Determining the biothermal effect, includes: Judging the samples in group A from step 3, which requires using the Ba element content and SiO2 / Al2O3 ratio of each sample obtained from the tests and calculations in step 2, and selecting samples in group A with a Ba content ≥ 500 × 10⁻⁶. -6 Samples with a SiO2 / Al2O3 ratio ≥ 4.5 were classified into Group I, and the remaining samples were classified into Group II. It can be determined that the black rock formation in the area where Group I samples were collected had the participation of submarine hydrothermal activity during the sedimentary formation process, and has extremely high uranium polymetallic mineralization potential; Group II samples are pending use. Now, we will evaluate the samples in group B from step 3. Samples in group B only need to meet the following condition: Ba content ≥ 500 × 10⁻⁶. -6 If either the SiO2 / Al2O3 ratio is ≥4.5, the sample will be classified into Group III for further use; if the Ba content in the sample is <500×10⁻⁶, the sample will be classified into Group III for further use. -6 Furthermore, if the SiO2 / Al2O3 ratio is less than 4.5, the sample is classified into group IV. It is also determined that the black rock formation in the area where the group IV sample was collected did not involve hydrothermal activity from the seafloor during its depositional formation, and therefore has very low mineral exploration value. Step 5: Isotope tracing determination includes: Now, isotope tracing is performed on the samples from groups II and III in step 4. This requires the isotope values ​​obtained in step 2. Samples from groups II and III with -2.8‰ ≥ δ are selected. 13 Samples with C≥-8.9‰ were assigned to Group V, and the remaining samples were assigned to Group VI. Based on this, it can be concluded that the black rock formation in the area where Group V samples were collected had the participation of submarine hydrothermal activity during the sedimentation process, and thus has extremely high mineralization value. The black rock formations in the area where Group VI samples were collected did not involve hydrothermal activity from the seafloor during their depositional formation, and therefore have very low mineral exploration value, so no further work is necessary.

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