CN115204563A - An evaluation method suitable for sandstone-type uranium ore prospecting target layers - Google Patents

Abstract

The invention belongs to the technical field of ore exploration of sandstone-type uranium ores in basins, and discloses an evaluation method suitable for an ore exploration target layer of sandstone-type uranium ores, which comprises the following steps: determining an ore-finding target layer in a basin uranium ore exploration area; litho-geochemical zonation is carried out on the target layer; carrying out equidistant continuous grooving on the target layer sand-mudstone, and collecting a sandstone sample and a mudstone sample; mechanically crushing and screening the collected sandstone sample to obtain sandstone fine grain components; testing and analyzing the sandstone fine particle component and the mudstone sample to obtain a test and analysis result; and evaluating the mineralization environment and potential of the uranium in the target layer according to the test analysis result. The samples collected by the method have more representativeness and contrast, the test data can comprehensively and accurately reflect the real geological geochemical characteristics of the target layer, the effective target layer position is prevented from being judged by mistake or omitted, and the uranium mineralization environment and potential of the prospecting target layer in the working area are scientifically evaluated.

Description

An evaluation method suitable for sandstone-type uranium ore prospecting target layers

technical field

The invention belongs to the field of prospecting technical methods for sandstone-type uranium deposits in a basin, and particularly relates to an evaluation method suitable for a prospecting target layer of sandstone-type uranium deposits.

Background technique

In the early stage of investigation and evaluation of sandstone-type uranium ore resources in sedimentary basins, it is necessary to comprehensively evaluate the elements, minerals and geochemical characteristics of rocks in different rock-geochemical zones in the prospecting target layer, and then objectively evaluate their uranium metallogenic potential. Among them, the reasonable collection and representativeness of rock samples in different petro-geochemical zones are directly related to the scientific evaluation of the metallogenic prospects of the target layer and the prediction of favorable prospects.

In the past, uranium mine geologists usually used the block picking or core splitting method to selectively collect some sandstone samples in different geochemical zones of the target layer, and then directly conduct whole-rock testing, analysis and evaluation. However, the representativeness of the data obtained in this way has certain limitations. Insufficient, and then have a greater impact on the evaluation of its metallogenic potential. For example, when a sample is collected in a zone where carbon cuttings or pyrite are extremely developed in the formation, the organic carbon or total sulfur content will be extremely high, leading to the conclusion that the reduction capacity of the target layer is high, and vice versa, it may be extremely low , will be used to indicate that the reduction ability of the target layer is weak, which may not fully and reasonably represent the real geological and geochemical characteristics of the layer; and various test results of the coarse-grained, medium-grained, and fine-grained sandstones in the target layer are also There are large differences and poor comparability. At the same time, the flow-rock reaction intensity in the later metallogenic process in the ore-bearing layer under the shallow (semi) open system is mostly clay level, which generally only leads to the change of the fine-grained matrix composition in the sandstone; The main components of quartz, feldspar, and various types of cuttings often cover up these weaker information on changes in geological and geochemical content, interfere with the reasonable evaluation of the characteristics and extent of fluid transformation in the later stage, and thus fail to accurately discover possible fluid epigenetic transformation and uranium mineralization. In addition, in the past, geologists mostly collected sandstone samples that were easily modified by later fluids, but did not pay attention to the collection and analysis of mudstone samples in the target layer, which may affect the accurate identification of the original geochemical characteristics of the target layer.

Therefore, the above factors will affect the accurate and objective evaluation of the uranium metallogenic potential of the entire prospecting target layer in the uranium exploration area to varying degrees, so that the effective prospecting target layer may be misjudged or omitted.

At present, no relevant literature has been published and no relevant patents have been applied for the methods of sample collection for different research purposes in the sandstone-type uranium ore prospecting target layers in the basin, and the general sample collection is mainly based on traditional geological research. methods and methods of sample collection. However, the above methods do not comprehensively consider the sandstone uranium metallogenic regularity and basic characteristics, and there are still some problems and deficiencies in the application of sample collection in the early-stage prospecting target layer for the investigation and evaluation of sandstone-type uranium deposits.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an evaluation method suitable for the prospecting target layer of sandstone-type uranium deposits. The ore prospecting target layer is from the zonal and segmented equidistant continuous groove collection and processing of sand-mudstone samples to the method and process of evaluating the metallogenic environment and potential based on the results of conventional chemical analysis. The obtained sample data can fully represent the geological earth of the target layer. The chemical characteristics and the obtained test data are conducive to comparative analysis, which can be accurately and truly used to objectively evaluate the uranium metallogenic potential and prospecting prospects of the ore prospecting target layer, and reasonably guide the prospecting deployment.

The technical scheme that realizes the object of the present invention:

An evaluation method suitable for a sandstone-type uranium ore prospecting target layer, the method comprising the following steps:

Step (1), determination of the prospecting target layer in the basin uranium exploration area;

Step (2), carry out lithologic geochemical zoning to target layer sand and mudstone respectively;

Step (3), carry out equidistant continuous grooves on sand-mudstone in different geochemical zones of the target layer, and collect sandstone samples and mudstone samples;

Step (4), mechanically crushing and sieving the collected sandstone samples to obtain fine-grained components of sandstone;

Step (5), test and analyze the fine-grained components of the sandstone and the mudstone sample, and obtain the test and analysis results;

In step (6), the uranium metallogenic environment and potential of the target layer are evaluated according to the test and analysis results.

The step (1) is: according to the analysis of the metallogenic environment in the basin area, determine the target horizon of sandstone-type uranium ore prospecting in the uranium ore exploration area, and require that there are drill holes in the area to expose the horizon, and there are corresponding rock samples. .

Described step (2) comprises:

Step (2.1), carry out lithology segmentation to the target layer according to sandstone and mudstone;

In step (2.2), color segmentation is performed on the sandstone and mudstone in the target layer.

Described step (3) comprises:

Step (3.1), continuously groove the sandstone after color segmentation in the target layer, and collect all grades of sandstone according to the number of samples required for each color segment;

In step (3.2), continuous grooves are performed on the color-segmented mudstone in the target layer, and the mudstone is collected according to the number of samples required for each color segment.

The step (4) is: setting a particle size threshold according to the size of the debris particles in the target layer, mechanically breaking the collected sandstone samples into coarse-grained components and fine-grained components, and retaining the fine-grained components of the sandstone.

The step (5) includes:

Step (5.1), crushing the fine-grained components of sandstone and mudstone samples into powder samples;

Step (5.2), perform selective mineral, elemental and environmental geochemical analysis on the powder sample.

The chemical analysis in the step (5.2) includes: major and trace analysis, clay X-ray quantitative diffraction analysis, organic carbon analysis, total sulfur analysis, redox potential analysis, pH value analysis and acid hydrolysis hydrocarbon analysis.

Described step (6) comprises:

Step (6.1), evaluating the epigenetic polyuranium ability of the target layer according to the environmental geochemical index;

Step (6.2), according to the comparative analysis of different colored sandstone geochemical indexes, to discriminate the characteristics and intensity of epigenetic oxidation or secondary reduction of the target layer;

Step (6.3): According to the comparative analysis of sandstone and mudstone geochemical indicators, comprehensively evaluate the sandstone uranium metallogenic environment, metallogenic potential and scale of the ore prospecting target layer in the investigation area.

The beneficial technical effect of the present invention is:

1. A method for evaluating the target layer of sandstone-type uranium ore prospecting provided by the present invention is based on the metallogenic characteristics of sandstone-type uranium deposits and the typical rock-geochemical zoning mode, and the zoning and subsections are continuously grooved to collect sand, Mudstone samples break through the limitation of only collecting a certain grade of sandstone in the target layer in the past, which is not only more representative, but also saves the cost of collecting and testing a large number of samples in the early stage;

2. The present invention provides an evaluation method suitable for the target layer of sandstone-type uranium ore prospecting. The mixed sandstone samples of each particle size are respectively subjected to mechanical crushing and screening, and the coarse-grained components are eliminated, which effectively reduces the fragmentation of the parent rock itself. The effect of clastic minerals on the results of epigenetic alteration analysis;

3. An evaluation method suitable for sandstone-type uranium ore prospecting target layers provided by the present invention conducts chemical tests on fine-grained components and mudstones in sandstone, so that the obtained test data can comprehensively and accurately reflect the real uranium formation of the target layer. Mining environment, prevent misjudgment or omission of effective target horizons, indicate the correct prospecting direction, directly serve the actual production needs, and have important promotion and application value;

4. An evaluation method suitable for the prospecting target layer of sandstone-type uranium ore provided by the present invention provides a reasonable method for collecting rock samples required for laboratory chemical analysis for uranium geologists in the process of sandstone-uranium ore exploration. , processing and evaluation methods, and then objectively evaluate the metallogenic environment and potential of the prospecting target layer.

Description of drawings

Fig. 1 is a kind of evaluation method flow chart that is applicable to sandstone type uranium ore prospecting target layer provided by the present invention;

FIG. 2 is the lithologic geochemical zoning and sample distribution map of the Yaojia Formation target layer of the SL1 drill hole in the southern Songliao Basin provided by the present invention.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

As shown in Figure 1, taking Kailu Depression in the southwest of Songliao Basin as the research object, an evaluation method suitable for sandstone-type uranium prospecting target layers is provided, which specifically includes the following steps:

Step (1), determination of the prospecting target layer in the uranium exploration area of the basin

Step (1.1), select a prospecting site in a sedimentary basin as a research object;

In step (1.2), determine the main prospecting target layers in the uranium ore survey area, and require that the target layers be exposed by drilling holes, and rock samples can be collected.

For example, the Kailu Depression in the southwest of the Songliao Basin was selected as the research object, the Yaojia Formation of the Upper Cretaceous was the target layer for prospecting, and the Yaojia Formation was exposed by the SL1 drilling hole.

Step (2), in the above-mentioned step (1), select the drill hole that exposes the target layer, and carry out lithologic geochemical zoning, i.e., lithology and color segmentation, respectively, on the sand and mudstone of the target layer.

Step (2.1), according to the ore prospecting target layer determined in the above-mentioned step (1), the target layer in the borehole is generally segmented from top to bottom according to two lithologies of sandstone and mudstone;

Step (2.2), according to step (2.1), color segmentation is performed on the sandstone and mudstone in the target layer respectively;

The sandstone belts are set as follows from top to bottom according to different colors: Sd ₁ , _{Sd 2} , Sd ₃ ,... Different colors are set as follows from top to bottom: Md ₁ , Md ₂ , _{Md 3} ,... , and when other positions in the target layer contain similar segments, the segment can be ignored or merged into the adjacent segment, otherwise it will be a separate segment.

For example, the Yaojia Formation prospecting target layer in the SL1 hole in the Kailu Depression is buried at a depth of 461.5m-596.59m. As shown in Figure 2, sandstones can be divided into 5 sections from top to bottom: Sd ₁ (red sandstone), Sd ₂ (gray sandstone), Sd ₃ (red sandstone), Sd ₄ (gray sandstone), Sd ₅ (red sandstone) Sandstone), the approximate burial depths are 462m-474m, 474m-495m, 495m-561m, 561m-565m, 565m-596.59m; mudstones can be divided into 7 sections from top to bottom: Md ₁ , Md ₂ , Md ₃ , The approximate burial depths of Md ₄ , Md ₅ , Md ₆ and Md ₇ are: 461.5m-500m, 500m-502m, 502m-534m, 534m-537.2m, 537.2m-561m, 561m-568m, 568m-585m. The thin lithological sections with different geochemical properties (generally less than _1m ) in each lithological section are selectively discarded and merged. The sandstone is classified into the adjacent gray sandstone Sd ₂ member; the red coarse sandstone with a burial depth of 564.8m-565.4m and a thickness of 0.6m in the gray sandstone Sd ₄ member has been discarded.

In step (3), the ore-prospecting target layers that have been divided into lithologic geochemical zones in the above step (2) are subjected to sand-mudstone equidistant grooves in different geochemical zones, and sandstone samples and mudstone samples are collected.

In step (3.1), based on the subdivided sandstone sections of different colors in the above-mentioned step (2), the uranium mine geologists collect a certain number of different colors and different grain grades for each section (Sd _n ) continuously grooved according to actual needs. For mixed sandstone samples, each section requires at least one sample to be collected; that is, firstly, a certain Sd _n section is divided into smaller sections at equal distances according to the actual number of samples to be collected, and then for each subsection, etc. The sandstones of all grades are collected from the continuous grooves, and the sandstones of different grades in the same sub-section need to be continuously grooved and mixed into a sandstone sample; finally, the registered samples are S ₁ , S ₂ , S ₃ , ..., _Sa ; where a is the number of sandstone samples.

Step (3.2), based on the different-color mudstone sections subdivided in the above-mentioned step (2), the uranium mine geologists collect a certain number of different-color mudstone samples in each section (Md _m ) according to the actual requirements, continuously grooved, Each section requires at least one sample to be collected; that is, a certain Md _m section is firstly divided into sub-sections equidistantly according to the number of samples to be collected, and then each sub-section is continuously grooved at equal distances to collect mudstone samples, and then the mudstone samples are collected. Register as M ₁ , M ₂ , M ₃ , ..., M _b in sequence; b is the number of mudstone samples.

For example, the sampling of the Yaojia Formation sandstone in the SL1 hole in the Kailu Depression in the southern Songliao Basin is as follows: As shown in Figure 2, the burial depth of Sd ₁ member is 462m-474m, and the thickness of the sandstone between them is 10.2m. There are 2 samples, so the thickness of the grooves in the samples S ₁ and S ₂ of this lithological section is 5.1m respectively, and the sampling depths are about 462m-468m and 468m-474m respectively; The 18.1m gray sandstone Sd ₂ section is planned to collect 3 samples, and the thickness of each sample is about 6m. Therefore, the depths of the collected S ₃ , S ₄ , and S ₅ samples are roughly 474m-481m, 481m-489m, and 489m, respectively. -495m; and so on, a total of 11 samples were collected in the 5 sandstone sections, and they basically covered all the sandstones in the prospecting target layer of the entire Yaojia Formation in the borehole.

At the same time, it is planned to collect one sample from each of the seven mudstone sections, and the sample numbers are set to M ₁ , M ₂ , M ₃ , M ₄ , M ₅ , M ₆ , and M ₇ in sequence. The burial depth and depth are shown in Table 1. , due to the poor porosity and permeability of mudstone and weak or non-reformed by late fluids, they can comprehensively represent the original geological and geochemical characteristics of the Yaojia Formation prospecting target layer.

Table 1. Test results of sand-mudstone samples from the target layer of Yaojia Formation in drill hole SL1 in the southern Songliao Basin

Remarks: The buried depth of the target layer of the Yaojia Formation is 461.5m-596.59m.

In step (4), the sandstone samples collected in the above step (3) are mechanically crushed and screened to retain the fine-grained components of the sandstone.

Based on the sandstone samples collected in the above step (3.1), manual and mechanical crushing is first performed in the room, and then the particle size threshold is set according to the size of the clastic particles in the target layer, and each sample is divided into coarse-grained components larger than the particle size threshold and smaller than the particle size threshold. The fine-grained components of the value, the coarse-grained parts are removed, and the corresponding fine-grained components are retained for subsequent testing, and are respectively numbered as S ₁ ', S ₂ ', S ₃ ', ..., S _a '.

For example, the 11 Yaojia Formation sandstones in the SL1 borehole in the area are screened according to the grain size threshold of 120 mesh, and the coarse-grained part of sandstone larger than 120 mesh is excluded, and the fine-grained sandstone with grain size smaller than 120 mesh is retained, and the numbers are S respectively. ₁ ', S2', _S3 ', _S4 ', _S5 ', _S6 ', _S7 ', _S8 ', _S9 ', _{S10 '} , _S11 ' for subsequent test utilization.

Step (5), test and analyze the fine-grained components of the sandstone in the above-mentioned step (4) and the mudstone sample in the above-mentioned step (3)

Step (5.1), based on the sandstone fine-grained component sample (S _a ') in the above step (4) and the mudstone sample (M _b ) collected in the step (3.2), first pulverize the samples into 200 mesh powder respectively After that, the powder sample is divided into several parts according to different test items, and the weight of each sample must meet the corresponding test requirements.

Step (5.2), respectively send the corresponding samples to the laboratory for selective mineral, element and environmental geochemical analysis; the total analysis items include: major and trace analysis, clay X-ray quantitative diffraction analysis, organic carbon analysis, total sulfur Analysis, oxidation-reduction potential analysis, pH value analysis and acid hydrolysis hydrocarbon analysis to obtain the corresponding test results; in this way, the geological and geochemical characteristics of the entire target layer can be fully represented, and the samples are all fine-grained components, which is convenient for subsequent comparative analysis. Accurately reflect the epigenetic alteration characteristics and intensity of the target layer.

For example, 11 pieces of fine-grained sandstone and 7 pieces of mudstone samples from the Yaojia Formation in the SL1 borehole of Kailu Depression in the southwestern Songliao Basin were first crushed into 200 mesh, and then each sample was divided into 3 parts and sent to the corresponding The laboratory conducted the main trace test, organic carbon test (C _with ) and total sulfur (S _total ) test, and obtained the elemental and environmental geochemical index data of the target layer of the entire Yaojia Formation. The results are shown in Table 1.

Step (6), according to the test results obtained in the above-mentioned step (5), evaluate the uranium metallogenetic geochemical environment and potential of the target layer

Uranium geologists based on the analysis and test data of fine-grained components of sandstone and mudstone obtained in the above step (5.2), based on the mineralization law of sandstone-type uranium deposits in the basin, starting from the characteristics, laws and patterns of sandstone uranium mineralization, Comprehensive comparative analysis of changes in mineralogy, element content and environmental geochemical indicators of sandstone and mudstone in different color zones was carried out, and a scientific evaluation of the uranium metallogenic geochemical environment and metallogenic potential of the ore prospecting target layer in the survey area was carried out; the specific steps include:

Step (6.1), evaluate the pre-enrichment strength and inherent uranium content of the target layer according to the uranium content of the primary gray mudstone and gray sandstone fine-grained components; identify the primary water environment of the target layer according to their clay mineral content differences and characteristics ; According to the environmental geochemical indicators between _them (C, S, Eh, etc.), _the epigenetic polyuranium ability of the target layer is evaluated.

Step (6.2), according to the above step (6.1) primary gray sand, mudstone samples and (red, yellow) warm-colored sandstone fine-grained component samples and (gray, light gray, gray-white, gray-green, green) cool-colored sandstone fine-grained samples The comprehensive comparison results of the differences in the mineralogy, elemental and environmental geochemical characteristics of the component samples are used to identify the characteristics and intensity of epigenetic oxidation or secondary reduction in the target layer.

In step (6.3), according to the above-mentioned steps (6.1) and the above-mentioned steps (6.2), the geological and geochemical characteristics and differences of sand-mudstone samples of different colors are compared, and the sandstone-uranium metallogenic environment and metallogenic potential of the ore prospecting target layer in the survey area are comprehensively evaluated. , size, etc.

For example, the analysis of the sample test results of the Yaojia Formation from the SL1 borehole in the Kailu Depression in the southwest of the Songliao Basin is as follows: From the results in Table ₁ , it can be seen that combined with the fine _- grained components _of gray sandstone S3', S4', S5', The test results of S ₉ ' and gray mudstone M ₂ , M ₄ , M ₆ show that the primary gray rock of Yaojia Formation has a high uranium content ranging from 2.77ppm to 30.2ppm, which has strong synsedimentary diagenetic uranium pre-enrichment; Its organic carbon and total sulfur are moderately low, 0.029%-0.714%, <0.003%-0.131%, respectively, indicating that its own uranium accumulation ability is general, especially the organic carbon of sandstone is generally low, and the reduction capacity is not high; therefore , this result is different from the previous view that the organic carbon of the local carbonaceous rock can reach 1%, so the target layer itself has a strong reducing ability. Our sampling method is within the same lithological and geochemical zone. The results of continuous rock sample collection are more reliable, which are consistent with the geological fact that the Yaojia Formation is a weakly reducing red variegated formation formed under arid and hot paleoclimate conditions. It is pointed out that the exudation of deep reducing fluid is an important sign of prospecting in this area. The uranium content (2.74ppm-4.42ppm), organic carbon content (0.044%-0.161%) and total sulfur content (all less than 0.003%) of the M ₁ , M ₃ , M ₅ , M ₇ primary red mudstone samples this time are all very high. Low value can also indicate that the target layer belongs to a set of red variegated deposits with weak reducibility.

The red sandstone fine-grained components S ₁ ', S ₂ ', S ₆ ', S ₇ ', S ₈ ', S ₁₀ ', and S ₁₁ ' of this Yaojia Formation have uranium content (1.72ppm-3.76ppm), organic carbon The very low test results (Table 1) of the total sulfur content (0.012%-0.088%) and total sulfur content (both less than 0.003%) reflect that the sandstone in this area has been subjected to strong epigenetic oxidation transformation, and the uranium leaching loss in the sand body is strong. Large-scale precipitation and enrichment of uranium deposits may occur in other parts, which can be verified from the discovery of the Qianjiadian ultra-large uranium ore field in the study area; it also reflects the Yaojia Formation in the uranium ore survey area in the southwestern Songliao Basin. There are very favorable uranium metallogenic potential and prospecting prospects, and it is worth further increasing exploration deployment.

The invention can be widely used in the process of prospecting and evaluation of sandstone-type uranium deposits in Mesozoic and Cenozoic sedimentary basins at home and abroad. The geological and geochemical characteristics and metallogenic environment of the ore target layer provide accurate data reference for objective evaluation of sandstone uranium metallogenic potential and scale, directly serve the needs of prospecting and deployment, and have important practical application and promotion value.

The present invention has been described in detail above in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the above-mentioned embodiments, and within the scope of knowledge possessed by those of ordinary skill in the art, various kind of change. The content that is not described in detail in the present invention can use the prior art.

Claims (8)

1. an evaluation method that is applicable to sandstone type uranium ore prospecting target layer, is characterized in that, described method comprises the following steps: Step (1), determination of the prospecting target layer in the basin uranium exploration area; Step (2), carry out lithologic geochemical zoning to target layer sand and mudstone respectively; Step (3), carry out equidistant continuous grooves on sand-mudstone in different geochemical zones of the target layer, and collect sandstone samples and mudstone samples; Step (4), mechanically crushing and sieving the collected sandstone samples to obtain fine-grained components of sandstone; Step (5), test and analyze the fine-grained components of the sandstone and the mudstone sample, and obtain the test and analysis results; In step (6), the uranium metallogenic environment and potential of the target layer are evaluated according to the test and analysis results. 2. a kind of evaluation method that is applicable to sandstone type uranium ore prospecting target layer according to claim 1, is characterized in that, described step (1) is: according to basin area metallogenic environment analysis, in uranium ore exploration area To determine the target horizon of sandstone-type uranium ore prospecting, it is required that there are drill holes in the area to expose the horizon and corresponding rock samples are available. 3. a kind of evaluation method applicable to sandstone type uranium ore prospecting target layer according to claim 2, is characterized in that, described step (2) comprises: Step (2.1), carry out lithology segmentation to the target layer according to sandstone and mudstone; In step (2.2), color segmentation is performed on the sandstone and mudstone in the target layer. 4. a kind of evaluation method applicable to sandstone type uranium ore prospecting target layer according to claim 3, is characterized in that, described step (3) comprises: Step (3.1), continuously groove the sandstone after color segmentation in the target layer, and collect all grades of sandstone according to the number of samples required for each color segment; In step (3.2), continuous grooves are performed on the color-segmented mudstone in the target layer, and the mudstone is collected according to the number of samples required for each color segment. 5. a kind of evaluation method suitable for sandstone type uranium ore prospecting target layer according to claim 4, is characterized in that, described step (4) is: according to target layer clastic particle size, set particle size threshold, set The collected sandstone samples are divided into coarse-grained components and fine-grained components after mechanical crushing, and the fine-grained components of the sandstone are retained. 6. a kind of evaluation method applicable to sandstone type uranium ore prospecting target layer according to claim 5, is characterized in that, described step (5) comprises: Step (5.1), crushing the fine-grained components of sandstone and mudstone samples into powder samples; Step (5.2), perform selective mineral, elemental and environmental geochemical analysis on the powder sample. 7. a kind of evaluation method that is applicable to sandstone type uranium ore prospecting target layer according to claim 6, is characterized in that, the chemical analysis in described step (5.2) comprises: main quantity and trace analysis, clay X quantitative Diffraction analysis, organic carbon analysis, total sulfur analysis, redox potential analysis, pH value analysis and acid hydrolysis hydrocarbon analysis. 8. a kind of evaluation method applicable to sandstone type uranium ore prospecting target layer according to claim 7, is characterized in that, described step (6) comprises: Step (6.1), evaluating the epigenetic polyuranium ability of the target layer according to the environmental geochemical index; Step (6.2), according to the comparative analysis of different colored sandstone geochemical indexes, to discriminate the characteristics and intensity of epigenetic oxidation or secondary reduction of the target layer; Step (6.3): According to the comparative analysis of sandstone and mudstone geochemical indicators, comprehensively evaluate the sandstone uranium metallogenic environment, metallogenic potential and scale of the ore prospecting target layer in the investigation area.

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