Method for identifying primary color and secondary color of sandstone in basin red mixed color uranium-containing construction

Abstract

The invention belongs to the field of in-situ leachable sandstone type uranium ore, and particularly relates to a method for identifying primary color and secondary color of sandstone in basin red mixed color uranium-containing construction, which comprises the following steps of: 1, analyzing macroscopic and microscopic geologic characteristics of sandstone with different colors; 2, analyzing spatial distribution rules of sandstones with different colors; step 3, analyzing geochemical characteristics of sandstones with different colors; step 4, performing quantitative reconstruction analysis on paleoclimate-paleo environment; 5, analyzing a sedimentary facies color control rule; and 6, multi-dimensional comprehensive collaborative analysis is carried out, and the primary color and the secondary color of the sandstone are identified. According to the method, the primary color and the secondary color of the sandstone in the red mottled building can be effectively and accurately identified, the geochemical zoning in the red mottled building and the front line drawing position of the oxidation zone are correctly divided, the uranium prospecting effect and probability are improved, and the sandstone type uranium mine possibly existing in the ancient depression in the center of the basin or the fracture development part is prevented from being omitted.

Description

Technical Field

[0001] This invention belongs to the field of in-situ leaching sandstone-type uranium deposits, specifically relating to a method for identifying the primary and secondary colors of sandstone in basin red-variegated uranium-bearing formations. Background Technology

[0002] Since the 1990s, a large number of large, medium, and even super-large sandstone-type uranium deposits have been discovered in several basins, including the Ili, Ordos, Turpan-Hami, Songliao, and Bayingol basins, and six large sandstone-type uranium mining bases have been established. In recent years, with the shift in prospecting strategies, significant progress has been made in uranium exploration within red-colored formations formed under semi-arid to arid climate conditions. Examples include thick, large, and rich uranium ore bodies in the Cretaceous red-colored formations in the northern and southwestern Ordos Basin; uranium ore bodies in the Neogene red-colored formations on the western edge of the Qaidam Basin; and industrial mineralization clues in the Neogene Shawan Formation of the Chepaizi Formation in the Junggar Basin. These findings demonstrate the enormous resource potential of sandstone-type uranium deposits within red-colored formations. Existing exploration results indicate that uranium mineralization in the aforementioned red-variegated formation generally occurs near the interface between oxidized and reduced sandstone, and is controlled by the oxidation front. This suggests that identifying the secondary oxidation zone and defining geochemical zoning markers within the red-variegated formation is crucial for uranium exploration deployment, with identifying the genesis of sandstone color being a key element. However, red-variegated formations often contain sandstones of various colors, including red, yellow, green, and gray. This can be due to oxidation of primary gray-green sandstone or subsequent alteration of primary red sandstone by reducing fluids. These two scenarios represent different mineralization models, exploration directions, and exploration locations, undoubtedly increasing the difficulty and uncertainty of uranium exploration within the red-variegated formation. Therefore, accurately identifying the primary and secondary colors of sandstone within the red-variegated formation is particularly important for delineating geochemical zoning, accurately determining the location of the oxidation zone front, and subsequently determining the exploration direction.

[0003] Currently, research on the genesis of sandstone color in red-variegated formations, both domestically and internationally, faces the following technical limitations: ① Single-index discrimination method: Existing technologies mostly rely on single geochemical indicators or macroscopic geological features for judgment, lacking a systematic approach. For example, relying solely on Fe... 3+ / Fe 2+ ① The ratio is used to determine the redox environment, but the controlling role of sedimentary facies and paleoclimate is ignored; ② There is a disconnect between the micro and macro scales, and the micro-lithological observation and macro-distribution characteristics are not organically combined, resulting in contradictory judgments; ③ The paleoclimate-paleoenvironment reconstruction is insufficient: the reconstruction of the paleoclimate and paleohydrological conditions that control color formation is not accurate enough, especially the identification of the warm-humid-arid transitional climate zone lacks effective indicators; ④ The practicality is insufficient: the existing methods are mostly still in the theoretical research stage and have not formed a standardized process that can guide exploration practice.

[0004] Therefore, taking the geological problems that urgently need to be solved in the exploration of sandstone-type uranium deposits as a starting point, there is an urgent need to develop a comprehensive, accurate, and easy-to-operate method for identifying the primary and secondary colors of sandstone to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a method for identifying the primary and secondary colors of sandstone in red-variegated uranium-bearing formations in basins. This method systematically integrates multi-dimensional discrimination indicators such as macroscopic and microscopic characteristics of sandstone, spatial distribution patterns, geochemical characteristics, paleoclimate-paleoenvironmental characteristics, and sedimentary facies characteristics. It can effectively and accurately identify the primary and secondary colors of sandstone in red-variegated formations, correctly delineate the geochemical zonation in red-variegated formations, and draw the position of the oxidation zone front line, thereby improving the uranium exploration effect and probability, and preventing the omission of sandstone-type uranium deposits that may exist in the paleodepressions or fault-developed areas in the center of the basin.

[0006] Technical solution to achieve the purpose of this invention: A method for identifying the primary and secondary colors of sandstone in uranium-bearing formations with reddish-brown variegated strata in basins, comprising: Step 1: Analysis of macroscopic and microscopic geological characteristics of sandstones of different colors; Step 2: Analysis of the spatial distribution patterns of sandstone of different colors; Step 3: Geochemical characteristics analysis of sandstones of different colors; Step 4: Quantitative reconstruction analysis of paleoclimate and paleoenvironment; Step 5: Analysis of the color control pattern of sedimentary phases; Step Six: Multi-dimensional comprehensive and collaborative analysis to identify the primary and secondary colors of sandstone.

[0007] Furthermore, step one includes: identifying the macroscopic and microscopic characteristics of sandstone of different colors through detailed observation of drill cores and petrographic analysis of typical samples to collaboratively distinguish the primary and secondary colors of sandstone.

[0008] Furthermore, the indicators for distinguishing primary and secondary colors of sandstone in step one include whether the sandstone color is related to grain size and degree of cementation, the uniformity of sandstone color and the clarity of color change boundaries, the occurrence state of colorants, the distribution characteristics of reducing substances, and special structures.

[0009] Furthermore, step two includes: based on the detailed observation of the borehole core in step one, drawing the spatial distribution characteristics of sandstone profiles and planes of different colors, identifying the distribution patterns of sandstone of different colors on the profiles and planes, and determining whether they are related to the distribution of sedimentary facies, ancient depressions, faults, and other development locations.

[0010] Furthermore, step three includes: taking sandstone samples of different colors from the borehole, conducting X-ray diffraction and major and trace element tests, and analyzing the characteristics of the types and contents of the different colored sandstone debris, as well as the types and contents of the colorants.

[0011] Furthermore, in step three, the sandstone fragments include quartz and potassium feldspar; the colorants include hematite, goethite, manganese oxides, chlorite, and organic matter; among them, quartz fragments are mostly grayish-white to gray, potassium feldspar fragments are mostly red, hematite is mostly red to brownish-red, goethite is mostly yellow, manganese oxides are mostly purple to grayish-black, chlorite is mostly green, and organic matter is mostly black.

[0012] Furthermore, step four includes: conducting major and trace element tests on the collected fine-grained sediment (mudstone, siltstone) samples, and comprehensively analyzing the paleoclimate and paleoenvironmental characteristics of the Red Variegated Formation.

[0013] Furthermore, the major and trace element discrimination indices in step four include: Sr / Ba, V / Cr, Ni / Co, V / (V+Ni), and Sr / Cu ratios.

[0014] Furthermore, step five includes: based on the field borehole core observation and rock and mineral identification in step one, analyzing the sedimentary composition structure, grain size, roundness and maturity in the red variegated formation, combining the changes in the vertical combination relationship of sediments and the cyclic development characteristics, preliminarily identifying the sedimentary facies development characteristics of the red variegated formation, determining the distribution characteristics on the sedimentary facies plane by drawing characteristic maps such as sand body isopyre maps and sand / mud ratio maps, and judging the primary color of sediments by the corresponding transport dynamic characteristics, sand body deposition environment and vegetation conditions of different sedimentary facies.

[0015] Further, step six includes: based on multi-dimensional discrimination such as the macroscopic and microscopic characteristics of sandstone in the red-variegated formation, the spatial distribution pattern of sandstone of different colors, the geochemical characteristics of sandstone of different colors, paleoclimate-paleoenvironment characteristics, and sedimentary facies characteristics, comprehensively identifying the primary and secondary colors of sandstone in the red-variegated formation; if the primary color of sandstone in the red-variegated formation is red, then subsequent mineral exploration should focus on areas with developed faults; if the primary color of sandstone in the red-variegated formation is grayish-green, then subsequent mineral exploration should focus on the basin margin and the paleodepression in the center of the basin, finding the location of the grayish-green sand bodies that control the formation of uranium mineralization, and combining this with the accurate mapping of the oxidation zone front to complete uranium mineralization exploration. The beneficial technical effects of this invention are: This invention provides a method for identifying the primary and secondary colors of sandstone in red-variegated uranium-bearing formations within basins. Through multi-dimensional, multi-indicator synergistic cross-validation, it improves the accuracy of distinguishing primary and secondary colors in sandstone, facilitating the correct delineation of geochemical zoning and the mapping of oxidation zone fronts within red-variegated formations. This enhances prospecting effectiveness and probability while reducing exploration costs. When prospecting within red-variegated formations in basins, it can provide new directions and locations for subsequent prospecting, preventing the overlooking of potential sandstone-type uranium deposits in paleodepressions or fault-developed areas in the basin center. This provides technical support and evaluation criteria for finding sandstone-type uranium deposits within red-variegated formations in basins. Attached Figure Description

[0016] Figure 1 A flowchart illustrating a method for identifying the primary and secondary colors of sandstone in uranium-bearing red variegated formations in basins, provided by this invention. Figure 2 The following are macroscopic and microscopic features of the Huanhe Formation sandstone in the northwestern Ordos Basin in this embodiment of the invention: Figure a is a brownish-red coarse sandstone, Figure b is a purplish-red coarse sandstone, Figure c is a brownish-red oxidation spot in green coarse sandstone, Figure d is a brown oxidation band in gray medium sandstone containing organic matter, Figure e is a green coarse sandstone, Figure f is a green medium sandstone containing organic matter, Figure g is a film of iron oxide on the surface of the grains and iron oxide in the interstitial material, Figure h is an iron oxide of pyrite oxidation in the interstitial material, Figure i is a velvety iron oxide on the surface of the grains, Figure j is an iron oxide and chlorite in the pores, Figure k is a film of chlorite on the surface of the grains, and Figure l is a film of chlorite and green / montmorillonite mixed layer in the pores; Figure 3 The following are spatial distribution characteristics of sandstones of different colors in the lower and upper sections of the Huanhe Formation in the northwestern Ordos Basin, as shown in the embodiments of the present invention: Figure a is a plan view of the lower section of the Huanhe Formation, Figure b is a plan view of the upper section of the Huanhe Formation, Figure c is a cross-sectional view along AB in Figures a and b, and Figure d is a cross-sectional view along CD in Figures a and b. Figure 3 Middle: 1 – Luohandong Formation; 2 – Upper section of Huanhe Formation; 3 – Lower section of Huanhe Formation; 4 – Upper section of Luohe Formation; 5 – Lower section of Luohe Formation; 6 – Anding Formation; 7 – Erosion line; 8 – Boundary between oxidation zone and transition zone; 9 – Front line of interlayer oxidation zone; 10 – Stratigraphic boundary; 11 – Angular unconformity boundary; 12 – Fault; 13 – Oxidation zone (red sandstone); 14 – Transition zone (brownish-red, brown with green, green with brown, brownish-gray); 15 – Reduction zone (green sandstone); 16 – Industrial ore body; 17 – Mineral deposit; 18 – Drill hole; 19 – Location; Figure 4 This is a paleoclimate and paleosedimentary environment feature map of the Huanhe Formation in the northwestern Ordos Basin, as described in this embodiment of the invention. Figure 5 This is a map showing the distribution characteristics of the Huanhe Formation sedimentary facies in the northwestern Ordos Basin, as described in this embodiment of the invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0018] like Figure 1 As shown, this invention provides a method for identifying the primary and secondary colors of sandstone in uranium-bearing formations with reddish-brown variegated strata in basins, specifically including the following steps: Step 1: Analysis of the macroscopic and microscopic geological characteristics of sandstone of different colors.

[0019] By carefully observing drill cores and analyzing the petrography of typical samples, the macroscopic and microscopic characteristics of sandstones of different colors are identified to collaboratively distinguish the primary and secondary colors of sandstones. The distinguishing indicators include whether the color of sandstone is related to grain size and degree of cementation, the uniformity of sandstone color and the clarity of color change boundaries, the occurrence state of colorants, the distribution characteristics of reducing substances (carbon fragments, pyrite, etc.), and special structures (such as mudstone zoning, fading halos, etc.).

[0020] If the sandstone in the red-variegated formation has the following macroscopic characteristics, it can be preliminarily determined that the primary color of the red-variegated formation is red, and other colors (yellow, gray-green) are secondary colors: A. The red sandstone is predominantly red, with widespread development of hematite films, and hematite films are also developed at the contact points between grains; B. The red sandstone has calcareous colloidal development and often contains evaporite interlayers; C. The red sandstone does not contain visible organic matter or reducing substances such as pyrite; D. The red sandstone has weak post-alteration alteration and a relatively dense cementation degree; E. The red sandstone profile shows development unrelated to grain size.

[0021] If the sandstone in the red-variegated formation has the following macroscopic characteristics, it can be preliminarily determined that the primary color in the red-variegated formation is grayish-green, and the other colors (red and yellow) are secondary colors: A. Carbon fragments and reducing substances such as pyrite can be seen in the grayish-green sandstone; B. Uneven brown spots are seen in the grayish-green, red and yellow sandstone; C. Grayish-green mudstone gravel is edged with brown rings; D. The red and yellow sandstone are generally strongly altered, with a high content of clay minerals, and iron oxide colorants are produced in the pores between the particles.

[0022] Step 2: Analysis of the spatial distribution patterns of sandstone of different colors.

[0023] Based on the detailed observation of the borehole core in step one, the spatial distribution characteristics of sandstone profiles and planes of different colors are plotted to identify the distribution patterns of sandstone of different colors on the profiles and planes, and to determine whether they are related to the distribution of sedimentary facies, ancient depressions, faults, and other development locations.

[0024] If red sandstone is evenly distributed on the plane or cross section, the sedimentary facies are mostly alluvial fan oxidation environment, and the gray-green sandstone is developed on the plane or cross section and is related to faults, then it indicates that the primary color of the sandstone in the red variegated formation is red, while gray-green is the secondary color.

[0025] If the location of the gray-green sandstone on the plane is closely related to the ancient depression, the sedimentary facies are mostly delta front or large braided channel sedimentary environments, and the red sandstone is distributed in a tongue shape on the plane or in the cross section, then it indicates that the primary color of the sandstone in the red variegated formation is gray-green, while the red is the secondary color.

[0026] Step 3: Geochemical characteristics analysis of sandstones of different colors.

[0027] By collecting sandstone samples of different colors from the borehole, X-ray diffraction and major and trace element tests were conducted to analyze the main types (quartz, potassium feldspar, etc.) and content characteristics of the different colored sandstone fragments, as well as the types (iron oxides / manganese oxides / chlorite / organic matter, etc.) and content characteristics of the colorants. Among them, quartz fragments mostly appear grayish-white to gray, potassium feldspar fragments mostly appear red, hematite mostly appears red to brownish-red, goethite mostly appears yellow, manganese oxides mostly appear purple to grayish-black, chlorite mostly appears green, and organic matter mostly appears black.

[0028] If the colorant content is >1.0%, the color of sandstone needs to be determined by combining the primary color and secondary color based on steps one and two.

[0029] If the colorant content is <1.0%, the sandstone color often appears as the inherited color of the clastic particles. The main components of the rock fragments are quartz >85% and potassium feldspar <5%, and the primary color of the sandstone is grayish-white to gray quartz inherited color. If the main components of the rock fragments are quartz <60% and potassium feldspar >10%, the primary color of the sandstone is red potassium feldspar inherited color.

[0030] Step 4: Quantitative reconstruction analysis of paleoclimate and paleoenvironment.

[0031] Major and trace element tests were performed on the collected fine-grained sediment samples (mudstone and siltstone) to comprehensively analyze the paleoclimate and paleoenvironment characteristics of the Red Variegated Formation. The discrimination indicators included Sr / Ba, V / Cr, Ni / Co, V / (V+Ni), and Sr / Cu ratios. Specific indicators are shown in Table 1.

[0032] Table 1. Quantitative Reconstruction Index System for Paleoclimate and Paleoenvironment If Sr / Cu < 5, it indicates that the red variegated formation was deposited during a brief period of warm and humid paleoclimate, when there was sufficient water, which was conducive to the extensive development of vegetation and could form gray sediments rich in carbon fragments, resulting in the presence of gray-green sediments in the red variegated formation.

[0033] If 5 < Sr / Cu < 10, the paleoclimate of the red variegated formation sedimentation is semi-arid to semi-humid. The primary color of its sediment can be grayish green or light red. It is necessary to introduce discrimination indicators for the oxidation-reduction environment and salinity of the ancient water body for further discrimination. When the ancient water body is oxygen-rich (V / Cr < 2, Ni / Co < 5, V / (V + Ni) < 0.6) and the ancient water body is saline (Sr / Ba > 1), it indicates that the water body was insufficient during sedimentation, and the primary color of the sediment is mostly oxidation colors such as red. When the ancient water body is oxygen-poor or sub-oxygen-rich (2 < V / Cr < 4.25, 5 < Ni / Co < 7, 0.6 < V / (V + Ni) < 0.77) and the ancient water body is fresh water (Sr / Ba < 0.5), it indicates that the water body was sufficient during sedimentation, and the primary color of the sediment is mostly reduction colors such as grayish green. When the ancient water body is anoxic (4.25 < V / Cr, 7 < Ni / Co, 0.77 < V / (V + Ni)), the primary color of the sediment is mostly reduction colors such as gray.

[0034] If 10 < Sr / Cu, the paleoclimate of the red variegated formation sedimentation is an arid environment. The water body was insufficient during sedimentation, which was not conducive to the growth of vegetation. Evaporite interlayers often existed, and the primary color of the sediment was mostly oxidation colors such as light red.

[0035] Step Five: Analysis of sedimentary facies-controlled color law.

[0036] Based on the field borehole core observation and rock and mineral identification in Step One, analyze the component structure, grain size, roundness, and maturity of the sediment in the red variegated formation. Combine the vertical combination relationship changes and cyclic development characteristics of the sediment to preliminarily查明 the development characteristics of the sedimentary facies of the red variegated formation. Determine the distribution characteristics of the sedimentary facies (sub-facies) on the plane by drawing characteristic maps such as sand body isopach maps and sand / mud ratio maps, and use the corresponding transportation dynamic characteristics, sand body sedimentary environment, and vegetation conditions of different sedimentary facies (sub-facies) to discriminate the primary color of the sediment. The sedimentary facies characteristics and primary colors of the sediment in the red variegated formation are shown in Table 2.

[0037] Table 2 Sedimentary facies characteristics and primary colors of the sediment in the red variegated formation If the overall red variegated formation is an alluvial fan facies, which belongs to episodic water flow sedimentation. The sedimentary water body is greatly affected by paleoclimate, season, etc. The sedimentation is of a sudden nature. The sediment is exposed on the surface for a long time and undergoes oxidation, forming thick to very thick red conglomerates and sandy conglomerates, indicating that the primary color of the alluvial fan facies sandy conglomerates in the red variegated formation is mostly oxidation tones such as red.

[0038] If the reddish-brown structure is a braided river facies, its development scale and nature determine the type and color of the sediments. When it is a gravelly braided river, it is large in scale, but generally characterized by shallow water and rapid flow. Due to the large slope, strong water erosion and transport capacity, the deposition process is relatively slow. During the transportation and deposition process, the sediments are easily oxidized, forming braided river facies sandstone and conglomerate with a primary color of red. When it is a sandy braided river, the river channel is deeper, less affected by changes in external conditions, and the water flow is stable. The water-rich riverbed can maintain a relatively reducing environment for a long time, and fallen plant stems are easily buried and preserved, forming sediments with a primary color of gray or grayish-green and other reducing hues.

[0039] If the reddish-brown formation is a deltaic facies, the deltaic plain subfacies is similar to the sandy braided river facies. The primary color of its sediments is controlled by the water supply. If the water supply is sufficient, the primary color of the sediments is likely to be a reduced hue such as gray or grayish-green. If the water supply is insufficient, the primary color of the sediments is likely to be an oxidized hue such as red. The delta front subfacies is a subaqueous sedimentary environment dominated by a weakly reducing-reducing environment, which easily results in the primary color of the sediments being a reduced hue such as grayish-green and gray.

[0040] If the reddish-brown structure is an aeolian desert facies, and the entire area is in an arid and hot environment, it is easy for the sediments to have a primary color of red or other oxidized hues.

[0041] Step Six: Multi-dimensional comprehensive and collaborative analysis to effectively identify the primary and secondary colors of sandstone.

[0042] Based on the indicators used in the above steps to distinguish the primary and secondary colors of sandstone in red-variegated formations, a multi-dimensional and synergistic approach using multiple indicators is employed to comprehensively identify the primary and secondary colors of sandstone in red-variegated formations. Specifically, this involves comprehensive identification of the primary and secondary colors of sandstone in red-variegated formations based on multiple dimensions, including macroscopic and microscopic characteristics of sandstone, spatial distribution patterns of sandstone of different colors, geochemical characteristics of sandstone of different colors, paleoclimate-paleoenvironmental characteristics, and sedimentary facies characteristics.

[0043] If the primary color of the sandstone in the red-variegated formation is red, then subsequent prospecting should focus on areas with well-developed faults; if the primary color of the sandstone in the red-variegated formation is grayish-green, then subsequent prospecting should focus on the basin margin and the ancient depression in the center of the basin. This can quickly and efficiently locate the grayish-green sand bodies that control the formation of uranium mineralization. Combined with the accurate mapping of the oxidation zone front, this can improve the effectiveness and probability of uranium prospecting, providing technical support and evaluation basis for finding sandstone-type uranium deposits in the red-variegated formation of the basin.

[0044] Example 1 Taking the Huanhe Formation, a red-variegated uranium-bearing formation in the Telaobao uranium deposit in northwestern Ordos Basin, as an example, this embodiment provides a method for identifying the primary and secondary colors of sandstone in the red-variegated uranium-bearing formation of the basin, specifically including the following steps: Step 1: Analysis of the macroscopic and microscopic geological characteristics of sandstone of different colors.

[0045] Field core observations and detailed petrographic analysis indicate that the sandstone in the red variegated formation exhibits the following characteristics: Figure 2 As shown: A. The sandstone exhibits diverse colors, with abundant brown, reddish-brown, yellow, and purple oxidized sandstone, as well as a large amount of green and a small amount of gray reduced sandstone; B. The sandstone is generally loosely cemented with low calcium content, although locally densely cemented reddish-brown sandstone with high calcium content is observed; C. Carbonized plant debris is almost invisible in oxidized sandstone; D. Macroscopic geological features such as numerous brown and reddish-brown spots are often visible in yellow and purple sandstone, with carbonaceous debris found locally in reddish-brown ore-bearing sandstone; E. Iron oxide films surrounding grains are visible in oxidized sandstone, and numerous villous and... F. Flake-shaped iron oxides and iron oxides formed by the oxidation of pyrite and chlorite, with thin films of iron oxides also visible at the grain contact areas in the brownish-red sandstone; G. Occasionally, reducing substances such as carbonaceous debris and pyrite are visible in the gray and grayish-green sandstone; H. Grayish-green rims, brown spots, and banded oxidation of numerous red mudstones are visible; VII. Plant carbonaceous cell cavities, abundant strawberry-shaped pyrite, mixed layers of chlorophyllite, and clay minerals such as chlorite are visible in the grayish-green sandstone. Chlorite mainly occurs as foliation filling intergranular pores and as a thin film covering the surface of clastic grains, with thin films of chlorite also visible at the grain contact areas. The above macroscopic and microscopic geological features indicate that secondary colors in the reddish-brown variegated formation may include brownish-red, yellow, purple, and grayish-green, while primary colors may include brownish-red and grayish-green.

[0046] Step 2: Analysis of the spatial distribution patterns of sandstone of different colors.

[0047] like Figure 3 As shown in the spatial distribution map of sandstone of different colors, oxidized sandstone mainly occurs along the basin edge in plan view, while in cross section, it generally exhibits multi-layered, tongue-shaped occurrences. Oxidized sand bodies are mainly located in the upper part of the Huanhe Formation, while the lower part commonly features brownish-gray, greenish-brown, brownish-green, and green sandstone. From the basin periphery to the basin interior, the thickness and depth of oxidation gradually decrease, and the proportion of oxidized bodies gradually diminishes. Furthermore, the grayish-green sandstone in both plan view and cross section is controlled by the east-west trending Sanyanjing fault and also by the north-south trending ancient depression (Tianhuan Depression). The grayish-green sandstone in the lower section of the Huanhe Formation is more developed than that in the upper section; the former is mainly controlled by the ancient depression (Tianhuan Depression), while the latter is more controlled by faults. These characteristics indicate that the brownish-red, greenish-brown, and brownish-green oxidized sandstones in the red-variegated formation are mostly secondary colors, while grayish-green exhibits both primary and secondary colors.

[0048] Step 3: Geochemical characteristics analysis of sandstones of different colors.

[0049] The microscopic characteristics of the oxidized sandstones in Step 1, including brownish-red, purple, reddish-brown, and yellowish-green hues, show that their main coloring agent is iron oxide. Major element analysis results indicate that the content of ferric iron (Fe3+) is greater than 1.0%. Based on the combined analysis of Step 1 and Step 2, the brownish-red sandstone is determined to be the primary color, while the purple, reddish-brown, and yellowish-green sandstones are secondary colors. The microscopic characteristics of the reduced-color sandstones in Step 1, including grayish-green and green hues, show that their main coloring agent is chlorite, which is actually ferrous iron (Fe2+). Major element analysis results indicate that the content of ferrous iron (Fe2+) is greater than 1.0%. Based on the combined analysis of Step 1 and Step 2, the grayish-green and green sandstones exhibit both primary and secondary colors.

[0050] Step 4: Quantitative analysis of paleoclimate and paleoenvironment.

[0051] like Figure 4As shown, the trace element characteristics of fine-grained sediments in the red-variegated formation show that: (1) the Sr / Cu ratio is between 3.59 and 44.75, with the lower section of the Huanhe Formation having a Sr / Cu ratio between 3.59 and 13.01 and an average of 8.66, while the upper section of the Huanhe Formation has a Sr / Cu ratio between 27.35 and 44.75 and an average of 38.32, both greater than 10.0, indicating that the paleoclimate of the lower section of the Huanhe Formation was semi-humid to semi-arid during deposition, with local warm and humid climate, while the paleoclimate of the upper section of the Huanhe Formation was arid and hot during deposition; (2) the Sr / Ba value is between 0.33 and 1.72, with the lower section of the Huanhe Formation having a Sr / Ba value between 0.33 and 1.72. The values ​​are between 0.0 and 0.5. The Sr / Ba values ​​of the upper section of the Huanhe Formation are between 1.43 and 1.72, all greater than 1.0, indicating that the paleowater body at the time of deposition of the lower section of the Huanhe Formation was freshwater to brackish water, while the paleowater body at the time of deposition of the upper section of the Huanhe Formation was brackish water. This indicates that the paleowater body supply was sufficient at the time of deposition of the lower section of the Huanhe Formation, while the paleowater body supply was insufficient at the time of deposition of the upper section of the Huanhe Formation. This is also related to the dramatic increase in water evaporation and the rapid concentration of water. (3) The V / Cr values ​​are between 0.25 and 1.45, all less than 2.0. The Ni / Co values ​​are between 1.51 and 2.17, all less than 5.0, indicating that the paleowater body at the time of deposition was an oxygen-rich environment. The V / (V+Ni) values ​​are between 0.66 and 0.76, indicating that the paleowater body at the time of deposition of the Red Variegated Structure was a sub-oxygen-rich environment. The above-mentioned indicator system indicates that the paleoclimate of the lower section of the Huanhe Formation was semi-humid to semi-arid, with local warm and humid climates. The paleowater supply was sufficient during deposition. Although the paleowater environment was slightly rich to oxygen-rich, the overall paleoclimate was conducive to vegetation development, transforming the early diagenetic stage environment into a weakly oxidizing to weakly reducing environment. This resulted in the formation of a large amount of grayish-green or locally gray primary-colored sandstone, which is consistent with the presence of carbonized plant debris in the gray and green sandstone. This indicates that the primary color of the sandstone in the lower section of the Huanhe Formation was mostly green or grayish-green. In contrast, the paleoclimate of the upper section of the Huanhe Formation was arid and hot, with insufficient paleowater supply during deposition. The paleowater environment was slightly rich to oxygen-rich, which was not conducive to vegetation development. The resulting sediments were mostly red sandstone, consistent with the presence of iron oxide films at the contact points between the red sandstone grains.

[0052] Step 5: Analysis of the color control rules of the deposition phase.

[0053] The Huanhe Formation sedimentary facies zone in the northwestern Ordos region is relatively complete. Based on lithological assemblage characteristics, sand content, sand / mud ratio, and other factors, a series of subfacies can be identified, including alluvial fans, braided rivers, littoral-shallow lacustrine facies, and mid-channel bars, floodplains, braided river delta plains, and braided river delta fronts. Figure 5As shown. Among them, the Huanhe Formation in the Telaobao uranium deposit exhibits the sedimentary characteristics of a sandy braided river-braided river delta plain. When the paleoclimate of the lower section of the Huanhe Formation was semi-humid to semi-arid, with abundant and deep water, the main channel water showed characteristics of low salinity and relative reduction. Fallen plant stems were easily buried and preserved, which could give the sediments in the channel a grayish-green original color. When the paleoclimate of the upper section of the Huanhe Formation was arid, with insufficient and shallow water, the main channel water showed characteristics of high salinity and relative oxidation. Sediments were frequently exposed to the surface and subjected to oxidation, and organic matter was destroyed, which could give the sediments in the channel a red original color.

[0054] Step Six: Multi-dimensional comprehensive and collaborative analysis to effectively identify the primary and secondary colors of sandstone.

[0055] Based on a multi-dimensional analysis including the macroscopic and microscopic characteristics of sandstone in the red-variegated formation, the spatial distribution of sandstone of different colors, the geochemical characteristics of sandstone of different colors, paleoclimate-paleoenvironment characteristics, and sedimentary facies characteristics, the primary color of the sandstone in the lower part of the Huanhe Formation is mostly green or grayish-green, while brownish-red, purple, and brownish-gray, green-banded brown, and brown-banded green sandstones that transition from sandstone to green sandstone are secondary colors. The primary color of the sandstone in the upper part of the Huanhe Formation is mostly red, among which the large-scale grayish-green sandstone is a secondary color, caused by the reduction of Fe(III) in the primary red sandstone to Fe(II) due to the escape of deep oil and gas, forming chlorite. The large-scale brown, brownish-red, purple and other oxidized sandstones are caused by the secondary reduction of green sandstone and subsequent oxidation, which is also a secondary color. Based on this, and according to the mineralization theory of sandstone-type uranium deposits in the interlayer oxidation zone, it is proposed that the prospecting sites for sandstone uranium deposits in the upper section of the Huanhe Formation should focus on the location of fault development. This is consistent with the current exploration results showing that the uranium ore bodies in the upper section of the Huanhe Formation occur near the Sanyanjing fault. At present, uranium ore bodies in the lower section of the Huanhe Formation are rarely found near the fault. Therefore, the prospecting sites for sandstone uranium deposits should focus on locations closer to the basin margin and ancient depressions.

[0056] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A method for identifying the primary and secondary colors of sandstone in uranium-bearing red-colored formations in basins, characterized in that, include: Step 1: Analysis of macroscopic and microscopic geological characteristics of sandstones of different colors; Step 2: Analysis of the spatial distribution patterns of sandstone of different colors; Step 3: Geochemical characteristics analysis of sandstones of different colors; Step 4: Quantitative reconstruction analysis of paleoclimate and paleoenvironment; Step 5: Analysis of the color control pattern of sedimentary phases; Step Six: Multi-dimensional comprehensive and collaborative analysis to identify the primary and secondary colors of sandstone.

2. The method for identifying the primary and secondary colors of sandstone in uranium-bearing red-variegated formations in basins, as described in claim 1, is characterized in that... Step one includes: identifying the macroscopic and microscopic characteristics of sandstone of different colors through detailed observation of drill cores and petrographic analysis of typical samples to collaboratively distinguish the primary and secondary colors of sandstone.

3. The method for identifying the primary and secondary colors of sandstone in uranium-bearing red variegated formations in basins, as described in claim 2, is characterized in that... In step one, the indicators for distinguishing primary and secondary colors of sandstone include whether the sandstone color is related to grain size and degree of cementation, the uniformity of sandstone color and the clarity of color change boundaries, the occurrence state of colorants, the distribution characteristics of reducing substances, and special structures.

4. The method for identifying the primary and secondary colors of sandstone in uranium-bearing red-variegated formations in basins, as described in claim 2, is characterized in that... Step two includes: based on the detailed observation of the borehole core in step one, drawing the spatial distribution characteristics of sandstone profiles and planes of different colors, identifying the distribution patterns of sandstone of different colors on the profiles and planes, and determining whether they are related to the distribution of sedimentary facies, ancient depressions, faults, and other development locations.

5. The method for identifying the primary and secondary colors of sandstone in a basin-like red-variegated uranium-bearing formation according to claim 4, characterized in that, Step three includes: taking sandstone samples of different colors from the borehole, conducting X-ray diffraction and major and trace element tests, and analyzing the characteristics of the types and contents of the different colored sandstone debris, as well as the types and contents of the colorants.

6. The method for identifying the primary and secondary colors of sandstone in a basin-like red-variegated uranium-bearing formation according to claim 5, characterized in that, In step three, the sandstone fragments include quartz and potassium feldspar; the colorants include hematite, goethite, manganese oxides, chlorite, and organic matter; among them, quartz fragments are mostly grayish-white to gray, potassium feldspar fragments are mostly red, hematite is mostly red to brownish-red, goethite is mostly yellow, manganese oxides are mostly purple to grayish-black, chlorite is mostly green, and organic matter is mostly black.

7. The method for identifying the primary and secondary colors of sandstone in a basin-like red-variegated uranium-bearing formation according to claim 5, characterized in that, Step four includes: conducting major and trace element tests on the collected fine-grained sediment samples, and comprehensively analyzing the paleoclimate and paleoenvironmental characteristics of the Red Variegated Formation.

8. The method for identifying the primary and secondary colors of sandstone in a basin-like red-variegated uranium-bearing formation according to claim 7, characterized in that, The major and trace element discrimination indices in step four include: Sr / Ba, V / Cr, Ni / Co, V / (V+Ni), and Sr / Cu ratios.

9. A method for identifying the primary and secondary colors of sandstone in a basin-like red-variegated uranium-bearing formation according to claim 7, characterized in that, Step five includes: based on the field borehole core observation and rock and mineral identification in step one, analyzing the sedimentary composition structure, grain size, roundness and maturity in the red variegated formation, combining the changes in the vertical combination relationship of sediments and the cyclic development characteristics, preliminarily identifying the sedimentary facies development characteristics of the red variegated formation, determining the distribution characteristics of sedimentary facies on the plane by drawing characteristic maps such as sand body isopyrographs and sand / mud ratio maps, and judging the primary color of sediments by the corresponding transport dynamic characteristics, sand body deposition environment and vegetation conditions of different sedimentary facies.

10. The method for identifying the primary and secondary colors of sandstone in a basin-like red-variegated uranium-bearing formation according to claim 9, characterized in that, Step six includes: based on the macroscopic and microscopic characteristics of sandstone in the red-variegated formation, the spatial distribution pattern of sandstone of different colors, the geochemical characteristics of sandstone of different colors, paleoclimate-paleoenvironment characteristics, and sedimentary facies characteristics, etc., to comprehensively identify the primary and secondary colors of sandstone in the red-variegated formation; if the primary color of sandstone in the red-variegated formation is red, then subsequent mineral exploration should focus on the fault development areas; if the primary color of sandstone in the red-variegated formation is grayish-green, then subsequent mineral exploration should focus on the basin margin and the paleodepression in the center of the basin, find the location of the grayish-green sand body that controls the formation of uranium mineralization, and complete uranium exploration by combining the accurate drawing of the oxidation zone front.

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