A method for delineating a target area for prospecting a deep sandstone-type uranium deposit

Abstract

This invention belongs to the field of uranium mineralization prediction technology, specifically relating to a method for delineating prospecting target areas for deep sandstone-type uranium deposits. The method includes the following steps: Step 1, analyzing key ore-controlling elements of deep uranium mineralization strata; Step 2, identifying key geological features; Step 3, delineating prospecting target areas; and Step 4, drilling verification. The method for delineating prospecting target areas for deep sandstone-type uranium deposits designed in this invention combines geological, geochemical, and geophysical methods, utilizing existing data to quickly determine key ore-controlling elements and key geological issues in deep strata. This provides valuable technical support for target area selection and uranium geological exploration.

Description

Technical Field

[0001] This invention belongs to the field of uranium mineralization prediction technology, specifically relating to a method for delineating prospecting target areas for deep sandstone-type uranium deposits. Background Technology

[0002] Currently, sandstone-type uranium deposits have become the most important type of uranium deposit in the world and also the most economically exploitable type in my country. Before 2005, my country's exploration strategy for sandstone-type uranium deposits mainly focused on four aspects: "rich, near, shallow, and easy," with exploration depths generally limited to areas shallower than 300 meters at the basin edge. After 2005, the exploration strategy was adjusted to five aspects: "deep, rich, variable, abundant, and distant," with "deep" referring to exploration depths of less than 1500 meters for sandstone-type uranium deposits. Currently, exploration depths have reached 900 meters in the southern edge of the Ili Basin, 800 meters in the central Erlian Basin and northern Ordos Basin, and 700 meters in the Songliao Basin. In the southwestern edge of the Ordos Basin, new uranium mineralization bodies have been discovered within the Cretaceous Luohe Formation aeolian sedimentary system at depths of 700-2000 meters. Several new deep uranium anomaly zones have been discovered in the Junggar, Qaidam, Tarim, Songliao, and Jiuquan basins. The discovery of these deep uranium ore bodies and uranium anomaly zones has expanded the research field and prospecting space of sandstone-type uranium deposits, and has a profound impact on the theoretical research and exploration of sandstone-type uranium deposits.

[0003] Given that existing deep sandstone-type uranium deposits are characterized by large sand bodies, extensive mineralization areas, high grades, and significant thicknesses, the methods and technologies for deepening the prediction of deep uranium mineralization and delineating prospective areas and target areas need further optimization. Summary of the Invention

[0004] This invention proposes a method for delineating prospecting target areas in deep sandstone-type uranium deposits. This method updates and optimizes existing techniques for delineating prospecting target areas in deep sandstone-type uranium deposits, thereby providing valuable technical support for subsequent geological exploration work in deep sandstone-type uranium deposits.

[0005] The technical solution of this invention:

[0006] A method for delineating prospecting target areas in deep sandstone-type uranium deposits includes the following steps:

[0007] Step 1: Analyze the key ore-controlling factors in deep uranium mineralization strata, including:

[0008] Step 1.1 Uranium source control analysis;

[0009] Step 1.2 Construct mineral control structures;

[0010] Step 1.3 Constructing ore-controlling structures;

[0011] Step 1.4 Modify the ore control system;

[0012] Step 2: Identify key geological features, including:

[0013] Step 2.1 Identification of mineral-bearing sand bodies;

[0014] Step 2.2 Identification of favorable mineralization structures;

[0015] Step 2.3 Identification of redox transition zones and identification of uranium prospecting markers;

[0016] Step 3: Delineate the target area for mineral exploration;

[0017] Step 4: Drilling verification.

[0018] Step 1.1, uranium source control analysis, specifically includes: when the uranium abundance value of the source rock mass is within the range of 2×10⁻⁶... -6 ~8×10 -6 When the uranium activation mobility ranges from 50% to 90%, the uranium content of the ore-bearing layer itself ranges from 3 × 10⁻⁶. -6 ~6×10 -6 At that time, the rock mass in the erosion source area is prone to forming rich uranium sources, and a large amount of uranium will be leached out and transferred underground with rainwater, providing favorable conditions for uranium mineralization;

[0019] Step 1.2, the construction of the ore-controlling structure, specifically includes: sandstone-type uranium ore bodies are distributed in a banded pattern on the plane, with a length ranging from 20 to 60 km and a width ranging from 3 to 30 km; the sandstone-type uranium ore bodies have a vertical mud-sand-mud interlayer structure, suitable for superimposing into thick sand bodies with mudstone interlayers in the middle, and the thickness of a single sand body is 10 to 50 m, with a cumulative sand body thickness of 20 to 150 m and a sand content of 40% to 80%; in the process of uranium mineralization in deep strata, the favorable lithology is gravelly medium-coarse sandstone and medium sandstone, followed by medium-fine sandstone;

[0020] Step 1.3, tectonic mineralization, specifically includes: tectonic movements determine the sedimentary evolution of the basin; uplift, compression, and folding of the basin can all lead to fault formation, and granite magma intrudes along these faults, forming the main uranium source bodies for uranium mineralization; tectonic mineralization consists of two aspects: first, the control of tectonic movements on basin sedimentation; second, the control of tectonic reversal on epigenetic alteration; tectonic reversal leads to strata uplift and weathering and erosion. If the tectonic deformation is strong, uranium mineralization is mainly of the phreatic oxidation zone type; if the tectonic deformation is of moderate intensity, uranium mineralization is mainly of the inter-layer oxidation zone type.

[0021] Step 1.4, the modification and control of ore, specifically includes: modification and control of ore refers to the oxidation effect of surface water infiltration, mainly developing phreatic water and phreatic-interlayer oxidation; the vertical development depth of the phreatic oxidation zone is related to the stratum exposure and the underlying lithology; when phreatic oxidation encounters mudstone layers in the vertical direction, local bedding-parallel oxidation occurs, forming a phreatic-interlayer oxidation zone, with an oxidation zone length ranging from 15 to 30 km; an oxidation zone width ranging from 1 km to 12 km; an oxidation-reduction transition zone length ranging from 18 km to 45 km; a width ranging from 1 km to 14 km; a maximum oxidation depth ranging from 200 to 480 m; and a front line length ranging from 20 to 65 km; all of these factors are mainly controlled by the stratification and connectivity of the sand body.

[0022] Step 2.1, identification of ore-bearing sand bodies, includes: conducting a detailed analysis of the deep stratigraphic sedimentary system based on existing borehole, seismic, and electrical resistivity data in the study area to identify the sand body's permeability and the parts where the hydrogeological environment is prone to change; systematically collecting sand body samples from different locations, analyzing geochemical environmental characteristic parameters, and establishing geological-geochemical identification markers for sandstone-type uranium ore-bearing sand bodies to identify ore-bearing sand bodies;

[0023] The geological-geochemical identification markers of the sandstone-type uranium-bearing sand bodies specifically include: redox potential ΔEh value, pH value, clay content, and Fe content. 2+ / Fe 3+ value.

[0024] In step two, the redox potential in the geological-geochemical identification of the sandstone-type uranium ore-bearing sand body includes: the higher the redox potential ΔEh value, the stronger the redox capacity of the rock; the redox potential ΔEh value in the sand body shows a zonal distribution, with the oxidative zone ΔEh value ranging from 47 to 70 mV, the redox transition zone ΔEh value ranging from 138 to 188 mV, and the reduction zone ΔEh value ranging from 60 to 100 mV, indicating that the redox transition zone has a strong redox capacity, which is conducive to uranium mineralization;

[0025] The pH values ​​in the geological-geochemical identification of the sandstone-type uranium-bearing sand bodies include: typical oxidation-zone sandstone-uranium deposits exhibit vertical zonation with alkaline upper zones and acidic lower zones. Among them, the oxidation zone is generally alkaline with a pH value of 8.98–9.8; the redox transition zone is generally neutral to acidic with a pH value of 7.59–5.8; and the reduction zone is weakly alkaline with a pH value of 8.0–9.4.

[0026] In step two, the clay content in the geological-geochemical identification of the sandstone-type uranium ore-bearing sand body includes: clay content is characterized by the content of major elements Al2O3 and CaO; taking the Al2O3 and CaO content of the Erlian Basin as an example, it has good zoning. The Al2O3+CaO content in the oxidation zone is 10.07-10.75%, which is relatively low; the Al2O3+CaO content in the redox transition zone is 10.84-16.60%, which is relatively high; and the Al2O3+CaO content in the reduction zone is 9.98-11.415%, which is between the former two. This indicates that the high clay content in the redox transition zone is conducive to uranium mineralization by clay adsorption.

[0027] In step two, the Fe content in the geological-geochemical identification of the sandstone-type uranium-bearing sand body is... 2+ / Fe 3+ Values ​​include: Fe within the oxidation zone 2+ / Fe 3+ A value of 0.31–0.42 indicates a high degree of oxidation and high Fe content within the reduction zone. 2+ / Fe 3+ The value ranges from 0.58 to 0.72, indicating high reducing power, while Fe in the redox transition zone... 2+ / Fe 3+ The value ranges from 0.98 to 1.07, indicating a decrease in oxidation level and an increase in reducing power, which is beneficial for uranium mineralization.

[0028] Step 2.2, the identification of favorable mineralization structures, includes: using electrical, magnetic, gravity, and seismic data to determine the spatial distribution characteristics of the target layer sand bodies and the structural pattern of the target layer, to find the distribution patterns and structural patterns of different lithologies and facies within relatively strong tectonic activity areas, and to delineate the locations of favorable mineralization structures.

[0029] Step 2.3, identification of the redox transition zone, includes: using coalfield borehole data, borehole logging curves, and lithological characteristics to distinguish geological markers of the redox transition zone boundaries. The colors of the oxidation zone include yellow, light yellow, brownish-yellow, and bright yellow; the color of the reduction zone is gray; the total thickness of the oxidized sand body / sand body ranges from 20% to 60%; geochemical markers include Fe... 3+ / Fe 2+ ΔEh and pH value; and combined with fine-grained geochemical exploration and high-precision magnetic measurement methods, a system for identifying and locating deep redox transition zones was established.

[0030] Step 2.4 Identification of uranium prospecting indicators includes: utilizing ground radiometric measurement data, optimizing the data processing workflow, extracting the surface anomaly displays of deep mineral-induced anomalies, and determining the distribution characteristics of uranium prospecting indicators; the ground radiometric measurement data includes: ground radon concentration anomaly values, fine-grained geochemical soil uranium anomaly values, and high-precision magnetic anomalies;

[0031] The aforementioned abnormal ground radon concentration values ​​are generally greater than 10,000 Bq / m³. 3 The range of uranium anomaly values ​​in the fine-grained geochemical soil is 2 × 10⁻⁶. -6 ~15×10 -6 The high-precision magnetic anomalies include: the oxidation zone being located in a region with a high magnetic field and the redox transition zone being located in a region with a low magnetic field.

[0032] The delineation of the prospecting target area mentioned in step three includes: determining the ore-controlling uranium source and ore-controlling construction according to steps 1.1 and 1.2, and determining the favorable locations for uranium mineralization according to steps 1.3, 1.4, 2.1, 2.2, 2.3 and 2.4.

[0033] Step four, drilling verification, includes drilling verification of the favorable uranium mineralization sections identified in step three that are suitable for drilling verification.

[0034] The beneficial effects of this invention are:

[0035] Deep sandstone-type uranium deposits are characterized by large sand bodies, extensive mineralization areas, high grades, and significant thickness. Therefore, it is crucial to deepen research into key geological issues related to sandstone-type uranium mineralization, and based on this, predict prospective areas for deep exploration and delineate target areas, in order to provide reference and guidance for the national deployment of deep uranium resource exploration.

[0036] The method for delineating prospecting target areas in deep sandstone-type uranium deposits designed in this invention combines geological, geochemical, and geophysical approaches. It utilizes existing data to quickly determine key ore-controlling elements and critical geological issues in deep strata, providing valuable technical support for target area selection and uranium geological exploration. Attached Figure Description

[0037] Figure 1 This is a flowchart of a method for delineating prospecting target areas in deep sandstone-type uranium deposits according to the present invention;

[0038] Figure 2 This is a post-alteration alteration diagram of the upper segment of the Saihan Formation in the field area of ​​the Naomu root depression in an embodiment of the present invention.

[0039] Figure 3 This is a uranium anomaly map of fine-grained soil in the distant area of ​​the root depression of *Gnaphalium affine* in this embodiment of the invention.

[0040] Figure 4 This is a longitudinal lithological geochemical profile of the ancient river channel in the Naomugen Depression, as described in an embodiment of the present invention. Detailed Implementation

[0041] The following describes in detail, with reference to the accompanying drawings and embodiments, a method for delineating prospecting target areas in deep sandstone-type uranium deposits according to the present invention.

[0042] Step 1: Analysis of Key Ore-Controlling Elements in Deep Strata

[0043] Through data collection, collation, field geological surveys, and indoor analysis and testing, the key ore-controlling elements of deep uranium mineralization are analyzed from the aspects of uranium source control, ore-controlling formation, ore-controlling structure, and ore-controlling alteration.

[0044] Step 1.1 Uranium Source Control

[0045] For uranium to accumulate in large quantities and form uranium deposits, there must be abundant uranium sources, and the uranium abundance value of the source rock mass must be (2×10⁻⁶). -6 ~8×10 -6 The high uranium activation mobility (50-90%) allows a large amount of uranium to be leached out and carried underground by rainwater, providing favorable conditions for uranium mineralization. Simultaneously, the ore-bearing layer itself has a uranium content (3×10⁻⁶). -6 ~6×10 -6 The higher concentration of uranium minerals is conducive to uranium mineralization.

[0046] Step 1.2 Construct mineral control

[0047] Sandstone-type uranium deposits exhibit a banded distribution in plan view, with a considerable scale (20–60 km in length and 3–30 km in width). Vertically, they possess a well-developed mudstone-sandstone-mudstone interbedded structure, which can be superimposed to form thick sandstone bodies with mudstone interlayers (single sandstone layer thickness 10–50 m, cumulative sandstone body thickness 20–150 m, sand content 40%–80%). During uranium mineralization at deep strata, favorable lithologies are gravelly medium-coarse sandstone and medium sandstone, followed by medium-fine sandstone, providing a suitable environment for uranium enrichment.

[0048] Step 1.3 Constructing Ore-Controlling Structures

[0049] Tectonic movements determine the sedimentary evolution of basins. Uplift, compression, and folding of basins can all lead to fault formation, at which point granitic magma intrudes along the faults, forming the main uranium source bodies for uranium mineralization. Analysis suggests that tectonic control over mineralization is mainly reflected in the following two aspects: First, the control of tectonic activity over sedimentation. The upper Saihan Formation sand bodies are buried at depths of 260–350 m, and the lower Saihan Formation sand bodies are buried at depths of 300–780 m, primarily focusing on areas with well-developed gray sand bodies. Second, the control of tectonic inversion over epigenetic alteration. Tectonic inversion leads to strata uplift and weathering / erosion. Strong tectonic deformation results in predominantly phreatic oxide zone uranium mineralization, while moderate tectonic deformation results in predominantly interbedded oxide zone uranium mineralization.

[0050] Step 1.4 Modify the ore control system

[0051] Later-stage alteration generally refers to the oxidation process caused by surface water infiltration, mainly developing into groundwater oxidation and groundwater-interlayer oxidation. The vertical depth of the groundwater oxidation zone is related to the stratum exposure and underlying lithology. When groundwater oxidation encounters mudstone layers in the vertical direction, localized bedding-parallel oxidation occurs, forming a groundwater-interlayer oxidation zone. The oxidation zone (length 15–30 km, width 1–12 km), oxidation-reduction transition zone (length 18–45 km, width 1–14 km), maximum oxidation depth (200–480 m), and front length (20–65 km) are mainly controlled by factors such as the stratification and connectivity of the sand body, directly determining the scale of uranium mineralization.

[0052] Step 2: Identification of Key Geological Issues

[0053] Step 2.1 Ore-bearing sand body identification technology

[0054] Based primarily on existing borehole, seismic, and electrical resistivity tomography data in the study area, a detailed analysis of the deep stratigraphic sedimentary system was conducted to identify areas of sand body permeability and hydrogeological environment prone to change. Sand body samples from different locations were systematically collected, and geochemical environmental characteristics were analyzed to establish geological-geochemical parameter identification markers for sandstone-type uranium-bearing sand bodies, which are used to identify ore-bearing sand bodies. The geological-geochemical parameter identification markers for sandstone-type uranium-bearing sand bodies include the following:

[0055] (1) Redox potential (ΔEh)

[0056] Redox potential (ΔEh) effectively reflects the redox capacity of rocks; a higher ΔEh value indicates a stronger redox capacity. The redox potential (ΔEh) within sandstone bodies exhibits zonation. The ΔEh value in the oxidation zone is generally between 47 and 70 mV, in the redox transition zone it is between 138 and 188 mV, and in the reduction zone it is between 60 and 100 mV. This indicates that the redox transition zone possesses strong redox capacity, which is favorable for uranium mineralization.

[0057] (2) Acidity / alkalinity (pH)

[0058] Typical oxidation-zone sandstone uranium deposits generally exhibit vertical zonation, with an upper alkaline zone and a lower acidic zone. The oxidation zone is generally alkaline, with a pH of 8.98–9.8; the redox transition zone is generally neutral to acidic, with a pH of 7.59–5.8; and the reduction zone is weakly alkaline, with a pH of 8.0–9.4, which is favorable for sandstone-type uranium mineralization.

[0059] (3) Clay content

[0060] Clay content can be characterized by the content of major elements Al2O3 and CaO. The Al2O3 and CaO contents in the Erlian Basin exhibit good zonation. The oxidation zone has a lower Al2O3+CaO content (10.07–10.75%); the redox transition zone has a higher Al2O3+CaO content (10.84–16.60%); and the reduction zone has an Al2O3+CaO content (9.98–11.415%) between the two. This indicates that the high clay content in the redox transition zone is conducive to uranium adsorption and mineralization.

[0061] (4)Fe 2+ / Fe 3+

[0062] Fe in the oxidation zone 2+ / Fe 3+ A value of 0.31–0.42 indicates a high degree of oxidation and high Fe content within the reduction zone. 2+ / Fe 3+ The value ranges from 0.58 to 0.72, indicating high reducing power, while Fe in the redox transition zone... 2+ / Fe 3+ The value ranges from 0.98 to 1.07, indicating a decrease in oxidation level and an increase in reducing power, which is beneficial for uranium mineralization.

[0063] Step 2.2 Identification technology for favorable mineralized structures

[0064] Using data from electrical, magnetic, gravity, and seismic methods, we determined the spatial distribution characteristics and structural pattern of the target layer sand bodies, studied the distribution patterns and structural patterns of different lithologies and facies within relatively strongly tectonically active areas, and delineated favorable mineralization structures.

[0065] Step 2.3 Redox Transition Zone Identification Technology

[0066] Using information such as coalfield boreholes, borehole logging curves, and lithological characteristics, this study investigates geological indicators (oxidized zone color (yellow, light yellow, brownish-yellow, bright yellow), reduced zone color (gray), oxidized sand body / total sand body thickness (20–60%)) and geochemical indicators (Fe) to distinguish the boundaries of redox transition zones. 3+ / Fe 2+ By combining technologies such as micro-grain geochemical exploration and high-precision magnetic measurement, a method system suitable for identifying and locating deep redox transition zones can be established.

[0067] Step 2.4 Uranium ore prospecting marker identification technology

[0068] Using ground-based radiometric measurements, including ground-based radon concentration anomalies (generally greater than 10,000 Bq / m³). 3 ), fine-grained geochemical soil uranium anomaly (2×10⁻⁶) -6 ~15×10-6 High-precision magnetic anomalies (i.e., the oxidation zone is located in a region with a high magnetic field; the redox transition zone is located in a region with a low magnetic field), etc., optimize the data processing flow, extract the surface anomaly display of deep mineral-induced anomalies, and determine the distribution characteristics of uranium prospecting indicators.

[0069] Step 3: Delineate the mineral exploration target area

[0070] Based on step 1.1, the Permian granite body in the Naomugen Depression erosion source area is large in scale and has a high uranium content, with an average uranium content of 3.6 × 10⁻⁶. -6 ~8.3×10 -6 Large amounts of U are leached by rainwater and transferred from the rocks into groundwater. Meanwhile, the average uranium content of the Saihan Formation is 3.81 × 10⁻⁶. -6 ~6.09×10 -6 This provided the main uranium source for uranium mineralization in the depression.

[0071] Based on step 1.2, the mineralized geological body in the Naomugen Depression is an ancient river channel in the upper section of the Saihan Formation, mainly a gravelly river channel, about 40 km long and 5-15 km wide, which is relatively large in scale. The thickness of the river channel sand body reaches 40-180 m, and the river channel curvature reaches 1.5, which is more conducive to sandstone-type uranium mineralization.

[0072] Based on steps 1.3, 1.4, 2.1, and 2.3, the bottom of the ancient river channel in the Naomugen Depression is composed of grayish-green argillaceous siltstone from the lower section of the Saihan Formation, buried at a depth of 420–780 m; the top of the channel is composed of red mudstone from the upper section of the Saihan Formation, buried at a depth of 360–420 m, exhibiting a shallower west and deeper east characteristic, which is conducive to the west-to-east flow of uranium sources. Simultaneously, the sand bodies within the channel are thick, coarse-grained, and highly permeable, resulting in most of the sand bodies in the central part of the channel being oxidized to bright yellow and red, with only gray sand bodies remaining in the bends of the channel. The total thickness of oxidized sand bodies is 31–45%. Figure 2 In the redox transition zone, the average ΔEh is 151 mV, the average pH is 7.1, the average Al₂O₃ + CaO is 16.31%, and the average Fe... 2+ / Fe 3+ The average value is 1.02, which is a favorable location for uranium mineralization.

[0073] Based on sections 2.2 and 2.4, soil radon gas measurements were conducted at a 1km × 1km interval in the root depression of *Gnaphalium affine*, with concentrations greater than 14212 Bq / m³. 3 Defined as an abnormal halo, with a concentration ranging from 11355 to 14212 Bq / m³. 3 Defined as high halo, with concentrations ranging from 8594 to 11355 Bq / m³. 3 The halo was identified as slightly elevated. Based on the paleochannel prospecting model, the area where the abnormal halo and the elevated or slightly elevated halo intersect was defined as a favorable area for uranium mineralization in paleochannel types.

[0074] A 1km × 1km fine-grained geochemical survey was conducted in the Naomugen Depression. A combination of micron-scale sieving and nanoscale observation techniques was used to separate the ore-forming elements adsorbed on clay particles. The content of these elements was then determined using highly sensitive ICP-MS to generate an anomaly map of the ore-forming elements in the area. Figure 3 As shown. Among them, the fine-grained geochemical soil uranium anomaly (4.2 × 10⁻⁶) -6 ~10.8×10 -6 The deposits are mainly concentrated in the upper section of the Saihan Formation in the southern part of the Naomugen Depression, which is consistent with the inferred redox transition zone, indicating that the area has good uranium mineralization potential.

[0075] High-precision magnetic surveys with a point spacing of 20m were conducted on the Naomugen Depression. The magnetic anomaly amplitude in this area is mostly in the range of -20 to 120 nT. The inferred redox transition zone is a low magnetic transition zone, which basically coincides with the geologically inferred redox transition zone, indicating that the area has good uranium mineralization potential.

[0076] Step 4: Drilling Verification

[0077] Based on step three, favorable uranium mineralization zones were identified for drilling verification. A series of boreholes were then drilled on the south side of the Qiaoergu area in the Naomugen Depression. The results showed that borehole EZK383-1099 developed uranium mineralization near the oxidation zone front. Figure 4 As shown.

[0078] 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 delineating prospecting target areas in deep sandstone-type uranium deposits, characterized in that... Includes the following steps: Step 1: Analyze the key ore-controlling factors in deep uranium mineralization strata, including: Step 1.1 Uranium source control analysis; Step 1.2 Construct mineral control structures; Step 1.3 Constructing ore-controlling structures; Step 1.4 Modify the ore control system; Step 2: Identify key geological features, including: Step 2.1 Identification of mineral-bearing sand bodies; Step 2.2 Identification of favorable mineralization structures; Step 2.3 Identification of redox transition zones and identification of uranium prospecting markers; Step 3: Delineate the target area for mineral exploration; Step 4: Drilling verification; Step 1.1, uranium source control analysis, specifically includes: when the uranium abundance value of the source rock mass is within the range of 2×10⁻⁶... -6 ~8×10 -6 When the uranium activation mobility ranges from 50% to 90%, the uranium content of the ore-bearing layer itself ranges from 3 × 10⁻⁶. -6 ~6×10 -6 At that time, the rock mass in the erosion source area is prone to forming rich uranium sources, and a large amount of uranium will be leached out and transferred underground with rainwater, providing favorable conditions for uranium mineralization; Step 1.2, the construction of the ore-controlling structure, specifically includes: sandstone-type uranium ore bodies are distributed in a banded pattern on the plane, with a length ranging from 20 to 60 km and a width ranging from 3 to 30 km; the sandstone-type uranium ore bodies have a vertical mud-sand-mud interlayer structure, suitable for superimposing into thick sand bodies with mudstone interlayers in the middle, and the thickness of a single sand body is 10 to 50 m, with a cumulative sand body thickness of 20 to 150 m and a sand content of 40% to 80%; in the process of uranium mineralization in deep strata, the favorable lithology is gravelly medium-coarse sandstone and medium sandstone, followed by medium-fine sandstone; Step 1.3, tectonic mineralization, specifically includes: tectonic movements determine the sedimentary evolution of the basin; uplift, compression, and folding of the basin can all lead to fault formation, and granite magma intrudes along these faults, forming the main uranium source bodies for uranium mineralization; tectonic mineralization consists of two aspects: first, the control of tectonic movements on basin sedimentation; second, the control of tectonic reversal on epigenetic alteration; tectonic reversal leads to strata uplift and weathering and erosion. If the tectonic deformation is strong, uranium mineralization is mainly of the phreatic oxidation zone type; if the tectonic deformation is of moderate intensity, uranium mineralization is mainly of the inter-layer oxidation zone type. Step 1.4, ore-controlling modification, specifically includes: ore-controlling modification refers to surface water infiltration and oxidation, mainly developing phreatic water and phreatic-interlayer oxidation; the vertical development depth of the phreatic oxidation zone is related to the stratum exposure and underlying lithology; when phreatic oxidation encounters mudstone layers vertically, localized bedding-parallel oxidation occurs, forming a phreatic-interlayer oxidation zone, with a length ranging from 15 to 30 km; a width ranging from 1 km to 12 km; a redox transition zone with a length of 18 km to 45 km; a width ranging from 1 km to 14 km; a maximum oxidation depth of 200 to 480 m; and a frontal length of 20 to 65 km; mainly controlled by sand body stratification and connectivity factors. Step 2.1, identification of ore-bearing sand bodies, includes: conducting a detailed analysis of the deep stratigraphic sedimentary system based on existing borehole, seismic, and electrical resistivity data in the study area to identify the sand body's permeability and the parts where the hydrogeological environment is prone to change; systematically collecting sand body samples from different locations, analyzing geochemical environmental characteristic parameters, and establishing geological-geochemical identification markers for sandstone-type uranium ore-bearing sand bodies to identify ore-bearing sand bodies; The geological-geochemical identification markers of the sandstone-type uranium-bearing sand bodies specifically include: redox potential ΔEh value, pH value, clay content, and Fe content. 2+ / Fe 3+ value; In step two, the redox potential in the geological-geochemical identification of the sandstone-type uranium ore-bearing sand body includes: the higher the redox potential ΔEh value, the stronger the redox capacity of the rock; the redox potential ΔEh value in the sand body shows a zonal distribution, with the oxidative zone ΔEh value ranging from 47 to 70 mV, the redox transition zone ΔEh value ranging from 138 to 188 mV, and the reduction zone ΔEh value ranging from 60 to 100 mV, indicating that the redox transition zone has a strong redox capacity, which is conducive to uranium mineralization; The pH values ​​in the geological-geochemical identification of the sandstone-type uranium-bearing sand bodies include: typical oxidation-zone sandstone-uranium deposits exhibit vertical zonation with alkaline upper zones and acidic lower zones, wherein the oxidation zone is alkaline with a pH value of 8.98–9.8; the redox transition zone is neutral to acidic with a pH value of 7.59–5.8; and the reduction zone is weakly alkaline with a pH value of 8.0–9.

4. In step two, the clay content in the geological-geochemical identification of the sandstone-type uranium ore-bearing sand body includes: clay content is characterized by the content of major elements Al2O3 and CaO; taking the Al2O3 and CaO content of the Erlian Basin as an example, it has good zoning. The Al2O3+CaO content in the oxidation zone is 10.07-10.75%, which is relatively low; the Al2O3+CaO content in the redox transition zone is 10.84-16.60%, which is relatively high; and the Al2O3+CaO content in the reduction zone is 9.98-11.415%, which is between the former two. This indicates that the high clay content in the redox transition zone is conducive to uranium mineralization by clay adsorption. In step two, the Fe content in the geological-geochemical identification of the sandstone-type uranium-bearing sand body is... 2+ / Fe 3+ Values ​​include: Fe within the oxidation zone 2+ / Fe 3+ A value of 0.31–0.42 indicates a high degree of oxidation and high Fe content within the reduction zone. 2+ / Fe 3+ The value ranges from 0.58 to 0.72, indicating high reducing power, while Fe in the redox transition zone... 2+ / Fe 3+ A value of 0.98–1.07 indicates a decrease in oxidation level and an increase in reducing power, which is beneficial for uranium mineralization. Step 2.2, the identification of favorable mineralization structures, includes: using electrical, magnetic, gravity, and seismic data to determine the spatial distribution characteristics of the target layer sand bodies and the structural pattern of the target layer; identifying the distribution patterns and structural patterns of different lithologies and facies within relatively strongly tectonically active areas; and delineating the locations of favorable mineralization structures. Step 2.3, the identification of the redox transition zone, includes: using coalfield borehole data, borehole logging curves, and lithological characteristics to distinguish geological markers of the redox transition zone boundaries. The colors of the oxidation zone include yellow, light yellow, brownish-yellow, and bright yellow; the color of the reduction zone is gray; the total thickness of the oxidized sand body / sand body ranges from 20% to 60%; geochemical markers include Fe... 3+ / Fe 2+ ΔEh, pH value; and combined with fine-grained geochemical exploration and high-precision magnetic measurement methods, establish a system for identifying and locating deep redox transition zones; Step 2.4 Identification of uranium prospecting indicators includes: utilizing ground radiometric measurement data, optimizing the data processing workflow, extracting the surface anomaly displays of deep mineral-induced anomalies, and determining the distribution characteristics of uranium prospecting indicators; the ground radiometric measurement data includes: ground radon concentration anomaly values, fine-grained geochemical soil uranium anomaly values, and high-precision magnetic anomalies; The abnormal ground radon concentration was greater than 10,000 Bq / m³. 3 The range of uranium anomaly values ​​in the fine-grained geochemical soil is 2 × 10⁻⁶. -6 ~15×10 -6 The high-precision magnetic anomalies include: the oxidation zone being located in a region with a high magnetic field, and the redox transition zone being located in a region with a low magnetic field. Step three, delineating the prospecting target area, includes: determining the uranium source and ore-controlling factors according to steps 1.1 and 1.2; and determining favorable locations for uranium mineralization according to steps 1.3, 1.4, 2.1, 2.2, 2.3, and 2.

4. Step four, drilling verification, includes drilling verification of the favorable uranium mineralization sections identified in step three that are suitable for drilling verification.

Images