Sandstone type uranium mine exploration method based on radon gas-gamma measurement

Abstract

The invention provides a sandstone type uranium mine exploration method based on radon gas-gamma measurement. The invention discloses a sandstone type uranium mine exploration method based on radon gas-gamma measurement. The method comprises the following steps: S1, collecting radon gas measurement data; s2, collecting ground total gamma measurement data; s3, determining the lower limit of radon gas and gamma abnormity; s4, reducing the influence of terrain on radon gas measurement by using a median contrast value filtering method; and S5, determining the ratio of the radon concentration to the total gamma measurement uranium content. The sandstone type uranium mine exploration method based on radon gas-gamma measurement provided by the invention has the advantages that the cause of the abnormal signal can be comprehensively analyzed, and the abnormal signal related to the deep sandstone type uranium mine can be screened out, so that the drilling deployment is guided and the prospective area of the uranium mine is predicted; the method has the advantage of effectively extracting weak abnormal signals of radon and decay products thereof above the sandstone type uranium mine.

Description

Technical Field

[0001] The invention relates to the technical field of uranium exploration, and in particular to a method for sandstone-type uranium exploration based on radon-gamma measurement. Background Art

[0002] Radon (mainly refers to 222 Rn, whose half-life is about 3.825 days, is mainly derived from natural rocks and soil. 238 U decays in the natural decay chain, and is the only radioactive noble gas in nature. Radon has a strong ability to migrate underground in nature, and can be used as a natural tracer to reflect underground information. It is widely used in many fields such as mineral exploration, geological engineering, geodynamic research, and earthquake disaster prediction, especially in uranium exploration, oil exploration, geological structure, and groundwater hydrological surveys. Soil radon concentration measurement can be used to find uranium mines in areas covered by loose soil; it is also widely used in the study of faults in geological structures.

[0003] Since the process of radon generation from deep underground to migration to the near surface is complex and invisible, especially in the application of prospecting for concealed ore bodies, radon gas measurement has become one of the main radioactive measurement methods in the field of sandstone-type uranium mine exploration, relying on its convenient and fast characteristics and good indication effect on concealed uranium mineralization. Although radon anomalies are mainly affected by the surface radium content, theoretically speaking, in addition to the part formed by the decay of the surface radium element, the radon concentration also migrates from underground. This part of radon gas does not migrate directly from the ore body hundreds of meters deep, but is formed by the decay of the radium element rising from the deep when it migrates to the near surface. If this part of radon concentration data can be accurately obtained, it will be very helpful to determine the location of the hidden ore body at a certain depth. The uranium equivalent data measured by the total gamma ray represents the radium content on the surface, and the radon concentration data indicates the total amount of radium elements that migrate on the surface and underground. The radium content rising from the deep is obtained after mathematical calculation of the two types of data, which can achieve a better guidance for prospecting.

[0004] Radon gas measurement and gamma measurement are fast, portable, sensitive and low-cost radioactive measurement methods. However, the geological interpretation of using radon gas measurement to find sandstone-type uranium deposits is generally complicated. The weak anomalies produced by radon and its daughters above sandstone-type uranium deposits are often superimposed on a more complex background. The current focus is on how to identify and extract these weak anomalies. Based on the investigation and research results of radon gas and gamma measurement in sandstone-type uranium deposits in the northern series of basins, the applicant has condensed the correlation analysis of the measurement results of radon gas measurement and total gamma measurement on the basis of previous research, and combined the obtained radon concentration anomalies with the geological and hydrological research results and geomorphological conditions in the field, comprehensively analyzed and inferred the causes of the anomalies, and extracted the anomalies related to deep sandstone-type uranium deposits to guide the deployment of drilling holes and predict the prospective areas of uranium mineralization. This is a method worthy of reference for extracting weak anomalies produced by radon and its daughters above sandstone-type uranium deposits. It is expected to provide strong technical support for the prospecting and exploration of sandstone-type uranium deposits in basins in the future.

[0005] Therefore, it is necessary to provide a method for sandstone-type uranium deposit exploration based on radon-gamma measurement to solve the above technical problems. Summary of the invention

[0006] The technical problem solved by the present invention is to provide a method for comprehensively analyzing the causes of abnormal signals, which is helpful to effectively extract the weak abnormal signals of radon and its decay products above sandstone-type uranium deposits, and then guide drilling deployment and predict uranium prospecting areas, providing important technical support for prospecting and exploration of sandstone-type uranium deposits, planning of mineralization prospecting areas, etc.

[0007] In order to solve the above technical problems, the present invention provides a method for sandstone-type uranium ore exploration based on radon-gamma measurement, comprising the following steps:

[0008] S1: Collect radon gas measurement data;

[0009] S2: Collecting ground gamma total measurement data;

[0010] S3: Determine the lower limit of radon and gamma anomalies;

[0011] S4: Use median contrast filtering to reduce the impact of terrain on radon gas measurement;

[0012] S5: Determine the ratio of radon concentration to total gamma measured uranium content.

[0013] Preferably, in S1, collecting radon gas measurement data includes the following steps:

[0014] S11: Drill a hole at the sampling point with a diameter of 4.5 cm and a depth of 90 cm;

[0015] S12: Place the sampler in the sampling hole and discharge the air that has infiltrated the sampling hole;

[0016] S13: The air sample is drawn into the soil of the sampling hole by a vacuum pump. The pumping time is about 20 seconds and the sampling volume is 1.5L.

[0017] S14: Start high pressure to collect RaA ions in the gas sample;

[0018] S15: Instrument measurement, record measurement results.

[0019] Preferably, in S2, collecting the total ground gamma measurement data comprises the following steps:

[0020] S21: Use the digital gamma radiometer FD-3013 to carry out ground-based total gamma measurement;

[0021] S22: put the instrument into normal working state and determine the lower threshold and alarm threshold of the instrument;

[0022] S23: Take measurement readings at each measuring point and record the measuring point number, measuring point nature, terrain and geomorphic features in the field.

[0023] Preferably, in S3, determining the lower limits of radon and gamma anomalies comprises the following steps:

[0024] SPSS software was used for data statistics to conduct overall representativeness and discrete parameter statistics of the preprocessed data, draw frequency distribution histograms, perform normal distribution tests, and determine background values ​​and standard deviations.

[0025] Preferably, in S4, using the median contrast filter method to reduce the influence of terrain on radon gas measurement includes the following steps:

[0026] S41: Median contrast filter processing process:

[0027] By applying the median contrast filter method in the GeochemStudio integrated system to process radon gas data, the abnormal halo becomes smooth and continuous, the regularity becomes clearer, and the high abnormal area that is favorable to mineralization is still retained;

[0028] The median contrast filter method uses a window to replace the sub-area, taking the small window as the local anomaly and the large window as the local background, moving point by point, so that the background of each point or sub-area is different, and the radon concentration background surface is regarded as a continuously fluctuating surface;

[0029] In the process of this method, a large area is automatically divided into many small sub-areas, each of which has its own radon concentration background value and abnormal lower limit value. This theoretically solves the problem of identifying weak anomalies in low background areas and high background areas, weakens the negative impact of terrain on the radon anomaly morphology, and takes the median of 3×3 grids as a small window in the grid data as the trend value of the center grid of the small window.

[0030] The processing algorithm is as follows:

[0031] F u =Q u +1.5S h , 1

[0032] F 1 =Q 1 -1.5S h , 2

[0033] CW m =∑ s i＝1 Pi×ti

[0034] In formula 1, F u Indicates the lower limit of abnormal points, Q u represents the upper quartile, and F in formula (2) 1 represents the upper limit of abnormal points, Q 1 Indicates the lower quarter point, S h represents the internal dispersion, Pi represents the relative abundance of sample i, ti represents the trait value of sample ii, and S represents the number of data in the sample;

[0035] Calculate F using the median contrast filter algorithm u , then calculate CW m With F u The ratio C F , C F That is the lining value. If C F >1 represents a positive anomaly, based on which we can use the contrast value to identify radon anomalies;

[0036] S42: Combined use of digital elevation model data:

[0037] The digital elevation model data of the study area was collected to generate a topographic map, which was then matched and compared with the preprocessed radon concentration data.

[0038] Preferably, in S5, determining the ratio of radon concentration to total gamma ray measurement uranium content comprises the following steps:

[0039] The radon gas measurement data is divided by the gamma measurement data, and the logarithmic relative value is calculated as the ratio of the two. Then, the contour map of radon concentration and total gamma measurement is compiled.

[0040] Compared with the related art, the method for sandstone-type uranium ore exploration based on radon-gamma measurement provided by the present invention has the following beneficial effects:

[0041] The present invention provides a method for sandstone-type uranium mine exploration based on radon gas-gamma measurement. By comparing the results of radon gas measurement with the total gamma-ray dose measurement and combining the geological and topographic conditions on site, the causes of abnormal signals can be comprehensively analyzed, which is helpful to screen out abnormal signals related to deep sandstone-type uranium mines, thereby guiding drilling deployment and predicting uranium mine prospecting areas. For effectively extracting weak abnormal signals of radon and its decay products above sandstone-type uranium mines, a reference approach is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The invention provides radon gas and gamma interpretation related maps for a sandstone-type uranium mine exploration method based on radon gas-gamma measurement. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0044] Please refer to Figure 1 ,in, Figure 1 Radon gas and gamma interpretation related diagrams of the method for sandstone-type uranium ore exploration based on radon gas-gamma measurement provided by the present invention. The method for sandstone-type uranium ore exploration based on radon gas-gamma measurement includes the following steps:

[0045] Radon gas measurement and ground gamma total measurement data collection:

[0046] Radon gas measurement data collection:

[0047] During the measurement process, measurements and records shall be carried out according to the accuracy requirements of the measurement network.

[0048] Field radon measurement mainly uses instantaneous radon measuring instruments such as HDC-C or FD-3017 RaA, which have the advantages of no pollution to the detector, no interference from thoron, high sensitivity, simple operation, and can obtain measurement results on site. After the "three properties" of the instrument are checked, the accuracy and stability of the measuring instrument are ensured to be good. In the process of data collection, it is necessary to avoid interference from human factors and meteorological factors. It is best to complete the same measurement line at one time within a period of time with a small temperature difference. The basic steps of measurement can be simply summarized as "background measurement-inflation-measurement-exhaust" and so on.

[0049] (1) Drill a hole at the sampling point with a diameter of 4.5 cm and a depth of 90 cm; (2) Place the sampler in the sampling hole and exhaust the atmosphere that has infiltrated the sampling hole; (3) Use a vacuum pump to draw the gas sample from the soil in the sampling hole. The pumping time is about 20 s and the sampling volume is 1.5 L; (4) Start the high pressure to collect the RaA ions in the gas sample; (5) Perform instrument measurement and record the measurement results.

[0050] During the actual field measurement process, it should be noted that when measuring in low-lying and humid locations, beware of groundwater entering the dryer and the inner cavity of the lifting tube to avoid damaging the instrument or affecting the measurement results. When sampling and measuring with a metal collecting sheet, pay attention to the marking of the collecting sheet and correctly place the collecting surface and the measuring surface. After the sampler is inserted into the soil with the suction hole drilled with a steel chisel, it should be sealed and compacted with soil in time to avoid air leakage affecting the measurement results. Remove the fine sand sucked into the suction tube in time and lubricate it with butter. Avoid interference caused by human factors when laying out the measuring lines and measuring points and actually measuring.

[0051] Ground total gamma measurement data collection:

[0052] The total ground gamma measurement is carried out simultaneously with the radon gas measurement, and the measurement point is located 1-2 meters near the radon gas measurement point.

[0053] The digital gamma radiometer FD-3013 was used to measure the total amount of ground gamma in the area. During the whole measurement process, the digital gamma radiometer used had good stability, which ensured the accuracy of the original data. The instrument was placed in normal working state, mainly to determine the lower threshold and alarm threshold of the instrument. After pressing the start switch at each measuring point, the measurement reading was taken, and the measuring point number, measuring point nature, terrain and geomorphic features were recorded in the field.

[0054] Data processing and interpretation:

[0055] Radon and gamma anomaly lower limits determination:

[0056] SPSS software was used for data statistics to perform overall representativeness and discrete parameter statistics on the preprocessed data, draw frequency distribution histograms, perform normal distribution tests, and determine background values ​​and standard deviations. Based on the relationship between the data mean x and the standard deviation σ, the mean value xn obtained after multiple eliminations of data greater than x+2σ was taken as the background value, and the value xn+2σn was taken as the lower limit of abnormality to delineate abnormalities.

[0057] Use the median contrast filter method to reduce the impact of terrain on radon gas measurement:

[0058] There is seasonal water erosion in low-lying areas. The surface radium element is transported by water, resulting in a decrease in its content. Radon, as a decay product of radium, has a corresponding decrease in concentration. The radon anomaly on the surface is caused by radon gas that rises directly from deep areas. The radon anomaly measured on the surface is mainly formed by the decay of radium on the surface and the radon gas that rises directly from deep areas.

[0059] Median contrast filtering process:

[0060] By applying the median contrast filter method in the GeochemStudio integrated system to process radon gas data, the abnormal halo can be made smooth, continuous, and the regularity is clearer, while the high abnormal area with favorable mineralization is still retained. The median contrast filter method uses a window to replace the sub-area, with a small window as the local abnormality and a large window as the local background. It moves point by point, so that the background of each point or sub-area is different, and the radon concentration background surface is regarded as a continuously undulating surface. That is, in the processing of this method, a large area is automatically divided into many small sub-areas, each of which has its own radon concentration background value and abnormal lower limit value. This theoretically solves the problem of identifying weak anomalies in low background areas and high background areas, and weakens the negative impact of terrain on the radon abnormal morphology. In the gridded data, 3×3 grids are used as small windows, and the median is taken as the trend value (CWm) of the center grid of the small window.

[0061] The processing algorithm is as follows:

[0062] F u =Q u +1.5S h , (1)

[0063] F 1 =Q 1 -1.5S h , (2)

[0064] CW m =∑ s i＝1 Pi×ti

[0065] In formula (1), F u Indicates the lower limit of abnormal points, Q u represents the upper quartile, and F in formula (2) 1 represents the upper limit of abnormal points, Q 1 Indicates the lower quarter point, S h represents the internal dispersion. Pi represents the relative abundance of sample i, ti represents the trait value of sample ii, and S represents the number of data in the sample.

[0066] Calculate F using the median contrast filter algorithm u , then calculate CW m With Fu The ratio C F , C F That is the lining value. If C F >1 represents a positive anomaly, based on which we can use the contrast value to identify radon gas anomalies.

[0067] Digital elevation model (DEM) data combined with:

[0068] Digital elevation model (DEM) data of the study area were collected to generate a topographic map, which was then fitted and compared with the preprocessed radon concentration data.

[0069] The ratio of radon concentration to total gamma ray measurement uranium content:

[0070] Gamma measurement reflects the near-surface uranium mineralization information, while radon gas measurement is a comprehensive reflection of the deep and near-surface uranium mineralization information. Therefore, the ratio of radon concentration measured by active radon gas to uranium content measured by gamma measurement can effectively eliminate the impact of near-surface uranium mineralization.

[0071] Divide the radon gas measurement data by the gamma measurement data. Since the two have different dimensions, their logarithmic relative values ​​can be calculated as the ratio of the two, and then the contour map of radon concentration and total gamma measurement can be compiled.

[0072] Compared with the related art, the method for sandstone-type uranium ore exploration based on radon-gamma measurement provided by the present invention has the following beneficial effects:

[0073] The present invention provides a method for sandstone-type uranium mine exploration based on radon gas-gamma measurement. By comparing the results of radon gas measurement with the total gamma-ray dose measurement and combining the geological and topographic conditions on site, the causes of abnormal signals can be comprehensively analyzed, which is helpful to screen out abnormal signals related to deep sandstone-type uranium mines, thereby guiding drilling deployment and predicting uranium mine prospecting areas. For effectively extracting weak abnormal signals of radon and its decay products above sandstone-type uranium mines, a reference approach is provided.

[0074] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for sandstone-type uranium ore exploration based on radon-gamma measurement, characterized in that: The following steps are involved: S1: Collect radon gas measurement data; S2: Collecting ground gamma total measurement data; S3: Determine the lower limit of radon and gamma anomalies; S4: Use median contrast filtering to reduce the impact of terrain on radon gas measurement; S5: Determine the ratio of radon concentration to total gamma measured uranium content.

2. The method for sandstone-type uranium ore exploration based on radon-gamma measurement according to claim 1, characterized in that: In S1, collecting radon gas measurement data includes the following steps: S11: Drill a hole at the sampling point with a diameter of 4.5 cm and a depth of 90 cm; S12: Place the sampler in the sampling hole and discharge the air that has infiltrated the sampling hole; S13: The air sample is drawn into the soil of the sampling hole by a vacuum pump. The pumping time is about 20 seconds and the sampling volume is 1.5L. S14: Start high pressure to collect RaA ions in the gas sample; S15: Instrument measurement, record measurement results.

3. The method for sandstone-type uranium ore exploration based on radon-gamma measurement according to claim 2, characterized in that: In S2, collecting the total ground gamma measurement data includes the following steps: S21: Use the digital gamma radiometer FD-3013 to carry out ground-based total gamma measurement; S22: put the instrument into normal working state and determine the lower threshold and alarm threshold of the instrument; S23: Take measurement readings at each measuring point and record the measuring point number, measuring point nature, terrain and geomorphic features in the field.

4. The method for sandstone-type uranium ore exploration based on radon-gamma measurement according to claim 3, characterized in that: In S3, determining the lower limit of radon gas and the abnormality of the addition comprises the following steps: SPSS software was used for data statistics to conduct overall representativeness and discrete parameter statistics of the preprocessed data, draw frequency distribution histograms, perform normal distribution tests, and determine background values ​​and standard deviations.

5. The method for sandstone-type uranium ore exploration based on radon-gamma measurement according to claim 4, characterized in that: In S4, the median contrast value filtering method is used to reduce the influence of terrain on radon gas measurement, including the following steps: S41: Median contrast filtering process: By applying the median contrast filter method in the GeochemStudio integrated system to process radon gas data, the abnormal halo becomes smooth and continuous, the regularity becomes clearer, and the high abnormal area with favorable mineralization is still retained; The median contrast filter method uses a window to replace the sub-area, taking the small window as the local anomaly and the large window as the local background, moving point by point, so that the background of each point or sub-area is different, and the radon concentration background surface is regarded as a continuously fluctuating surface; In the process of this method, a large area is automatically divided into many small sub-areas, each of which has its own radon concentration background value and abnormal lower limit value. This theoretically solves the problem of identifying weak anomalies in low background areas and high background areas, and weakens the negative impact of terrain on the radon abnormal form. In the grid data, 3×3 grids are used as small windows, and the median is taken as the trend value of the center grid of the small window. F u =Q u +1.5S h ,1; F1=Q1-1.5S h ,2; CW m =∑ s i＝1 Pi×ti; In formula 1, F u Indicates the lower limit of abnormal points, Q u In Formula 2, F1 represents the upper quartile, Q1 represents the lower quartile, and S h represents the internal dispersion, Pi represents the relative abundance of sample i, ti represents the trait value of sample ii, and S represents the number of data in the sample; Use the median contrast filter algorithm to calculate Fu, and then calculate CW m With F u The ratio C F , C F That is the lining value. If C F >1 represents a positive anomaly, based on which we can use the contrast value to identify radon anomalies; S42: Combined use of digital elevation model data: The digital elevation model data of the study area was collected to generate a topographic map, which was then matched and compared with the preprocessed radon concentration data.

6. The method for sandstone-type uranium ore exploration based on radon-gamma measurement according to claim 1, characterized in that: In S5, determining the ratio of radon concentration to gamma total uranium content comprises the following steps: The radon gas measurement data is divided by the gamma measurement data, and the logarithmic relative value is calculated as the ratio of the two. Then, the contour map of radon concentration and total gamma measurement is compiled.

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