Method for remodeling basin sandstone type uranium ore curtain type metallogenic time sequence

Abstract

The invention belongs to the technical field of foreground prediction and scientific research of sandstone type uranium ores in basins, and particularly relates to a method for remodeling a screen-type metallogenic time sequence of sandstone type uranium ores in basins, which comprises the following steps: step (1), utilizing tectonic low-temperature thermal chronology or stratigraphic back-stripping inversion to recover the rise and fall history of ore-bearing stratums in a basin uranium ore gathering area, so as to obtain a screen-type metallogenic time sequence of the sandstone type uranium ores in the basin; comprehensively dividing a plurality of uranium metallogenic stages; (2) sandstone ore is systematically collected in different industrial uranium mine holes of the selected uranium mine concentration area, and ore microelement and Ra analysis is carried out; (3) carrying out U-Ra balance correction total rock U-Pb isotope dating on the same-pore sandstone uranium ore, and obtaining key metallogenic time points of different stages; (4) carrying out uranium occurrence form research on the sandstone uranium ore sample with high uranium content; (5) carrying out micro-area in-situ U-Pb isotope dating on the delineated uranium ore; and (6) according to the comprehensively divided data results of the multiple uranium metallogenic stages, the key metallogenic time points of the different stages and the micro-area in-situ U-Pb isotope dating, reconstructing the sandstone curtain type uranium metallogenic time sequence. According to the method, the multi-stage uranium metallogenic process in the open system can be effectively divided, and the success rate of obtaining the multi-stage key metallogenic age and the geological reliability of the multi-stage key metallogenic age are improved.

Description

Technical Field

[0001] The invention belongs to the field of prospect prediction and scientific research technology of sandstone-type uranium deposits in basins, and in particular relates to a method for reshaping the curtain-type mineralization sequence of sandstone-type uranium deposits in basins. Background Art

[0002] The formation of shallow sandstone-type uranium deposits in the basin is closely related to the evolution of tectonic uplift in the area. It is a kind of epigenetic uranium deposit formed by the infiltration of uranium-containing and oxygen-containing water along the outcrop area of ​​ore-bearing sand bodies during the period of tectonic compression and uplift, and the oxidation-reduction reaction occurs during the downward runoff process. Its mineralization system is open and dynamic, and the mineralization process is both episodic and continuous. The accurate determination of the mineralization time has always been an important basic geological issue in the study of sandstone-type uranium deposits, and has long faced major technical bottlenecks.

[0003] At present, the age of sandstone uranium mineralization is mainly obtained based on U-Pb isotope dating of ores or uranium minerals using dissolution methods (such as ID-TIMS) or in situ methods (such as La-ICP-MS, SIMS), but there are still some difficulties and shortcomings: ① The dating methods / means used in the past were mostly single, lacking a systematic technical method flow to comprehensively and objectively reflect the entire process of sandstone curtain uranium mineralization; ② Less attention was paid to how to effectively collect ore samples, and the sampling was unsystematic or chaotic, which directly affected the success rate of subsequent isochron age fitting; ③ The age data obtained by different dating methods are relatively scattered, and how to interpret their geological significance is relatively insufficient, which in turn leads to limited application in the field of mineralization and prospecting model construction, and ultimately affects the evaluation of mineralization prospects and prospecting and exploration deployment. Summary of the invention

[0004] The purpose of the present invention is to provide a method for reconstructing the episodic mineralization sequence of sandstone-type uranium deposits in a basin. The method constructs a set of dating technology methods for reconstructing the complete time chain of episodic mineralization of sandstone-type uranium deposits by constructing multidisciplinary related technologies such as low-temperature thermochronology, isotope chronology, and petrology and mineralogy. The method can effectively divide the multi-stage uranium mineralization process in an open system, improve the success rate and geological reliability of obtaining multi-stage key mineralization ages, and further provide technical support for studying sandstone multi-stage uranium mineralization patterns and prospecting models, and guide uranium mine exploration.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A method for reconstructing the episodic mineralization sequence of basin-type sandstone-type uranium deposits, the method comprising:

[0007] Step (1), using structural low-temperature thermochronology technology or stratum backstripping technology to invert, restore the structural uplift history of the ore-bearing strata in the uranium ore-rich area of ​​the basin, and comprehensively divide the potential multi-stage uranium mineralization stage;

[0008] Step (2), systematically collecting sandstone ore from different industrial uranium mine holes in the selected uranium ore cluster area, and conducting trace element and Ra analysis of the ore;

[0009] Step (3), performing U-Ra balance-corrected whole-rock U-Pb isotope dating on the sandstone uranium ore in the same hole to obtain key mineralization time points at different stages;

[0010] Step (4), conducting a study on the occurrence form of uranium in a sandstone uranium ore sample with a high uranium content;

[0011] Step (5), conducting micro-area in-situ U-Pb isotope dating on the identified uranium minerals;

[0012] Step (6): Reconstruct the sandstone curtain uranium mineralization time sequence based on the comprehensive division of multiple uranium mineralization stages, key mineralization time points in different stages, and micro-area in situ U-Pb isotope dating data.

[0013] The step (1) comprises:

[0014] Step (1.1), using stratum stripping or thermal history simulation technology, restore the subsidence and uplift evolution history of the ore-bearing strata in the uranium ore-rich area of ​​the basin, and obtain the evolution history curve of the ore-bearing strata in the uranium ore-rich area;

[0015] Step (1.2): Based on the acquired evolution history curve of the ore-bearing strata in the uranium ore cluster area and on the basis of structural compression-strata uplift, the potential multi-stage uranium mineralization stages are comprehensively divided.

[0016] The step (2) comprises:

[0017] Step (2.1), selecting different industrial uranium mine holes in the uranium ore concentration area to collect sandstone uranium ore samples, and collecting sandstone uranium ore samples of different grades;

[0018] Step (2.2), crush the sandstone uranium ore sample, and analyze the trace elements and Ra of the ore.

[0019] The trace elements in the ore in step (2) include U, Th, Mo and Pb.

[0020] The step (3) comprises:

[0021] Step (3.1), testing the uranium and lead isotope compositions of the sandstone uranium ore powder sample of step (2.2) using a mass spectrometer;

[0022] Step (3.2), using the U and Ra contents obtained in step (2.2), perform U-Ra balance correction on the isotopic composition data of the sandstone uranium ore in the same hole to obtain the corrected isotope ratio 238 U / 204 Pb, 235U / 204 Pb data;

[0023] Step (3.3), using the corrected isotope ratio obtained in step (3.2) 238 U / 204 Pb, 235 U / 204 Based on the Pb data and the uranium and lead isotope composition data obtained in step (3.1), the isochron age fitting of the sandstone uranium ore in the same hole was performed using Isotope or Excel software to obtain the key mineralization time points in different stages.

[0024] The step (3.2) is specifically as follows: using the U and Ra contents obtained in step (2.2), based on the correction formula Kp=Ra / (U×0.01241), where Ra and U are the contents measured today, the ancient uranium content of the sample (Up=U×Kp) and the corrected isotope ratio ( 238 U / 204 Pb)p= 238 U / 204 Pb×Kp and isotope ratios ( 235 U / 204 Pb)p= 235 U / 204 Pb×Kp.

[0025] The step (4) comprises:

[0026] Step (4.1), select the sandstone uranium ore sample with high uranium content in step (2), and grind parallel samples of the optical thin slice and the probe slice at the same position of the ore sample;

[0027] Step (4.2), carbon-coating the ground thin sections, conducting microscopic mineralogy and semi-quantitative elemental geochemical composition analysis, and circling out the unaltered uranium minerals.

[0028] The step (5) comprises:

[0029] Step (5.1), conduct electron probe in situ U-Pb isotope dating on the uranium minerals circled on the optical thin section;

[0030] Step (5.2), perform LA-ICP-MS micro-area in situ U-Pb isotope dating on the uranium minerals on the parallel sample of the probe sheet corresponding to the optical thin section.

[0031] The step (5.1) is specifically as follows: according to the uranium, thorium and lead contents obtained by the electron probe, the apparent age of the uranium mineral is calculated using the formula t=7550Pb / (U+0.365Th); wherein U, Th and Pb are the uranium, thorium and lead contents obtained by the electron probe, respectively, in units of mass percentage; and t is the apparent age of the uranium mineral, in units of millions of years;

[0032] The step (5.2) is specifically as follows: based on the U and Pb isotope ratios obtained by mass spectrometry, the age calculation formula commonly used in radioactive geochemistry and Isotope related processing software are used to obtain the apparent age and isochron age of the uranium mineral formation.

[0033] The step (6) is specifically as follows: comprehensively divide the early, middle and late three continuous mineralization stages of sandstone-type uranium deposits: pre-enrichment stage, oxidation-reduction main mineralization stage, and superposition transformation mineralization stage; eliminate isochron age data that is older than the stratigraphic age of the ore-bearing layer, and then sort the ages from large to small to obtain the pulsating key mineralization time points in each stage; use the apparent age and isochron age data of in-situ U-Pb dating of uranium mineral micro-areas as the superposition transformation time; and finally construct a time series chart of episodic mineralization of basin sandstone-type uranium deposits.

[0034] The beneficial technical effects of the present invention are:

[0035] 1. The method provided by the present invention for reconstructing the episodic mineralization sequence of sandstone-type uranium deposits in a basin provides a systematic combination of dating technology methods, which is more suitable for and meets the complete restoration of the sandstone episodic uranium mineralization process in an open system compared to a single dating technology, and the results are relatively more objective and true;

[0036] 2. Since the migration distance of uranium and lead may not be too far, the uranium-lead system in the mineralized section of the same borehole is still in a relatively balanced state as a whole, and the isotope homogenization within the same ore body can be achieved; the method provided by the present invention for reshaping the curtain-type mineralization time sequence of basin sandstone-type uranium deposits, which performs U-Pb or Pb-Pb isochron age fitting for the isotopic composition of sandstone ore in the same hole, obviously has a higher success rate and reliability than the age obtained by the dispersed ore sample data of different boreholes, which has also been verified by comparison in the example work of the patent;

[0037] 3. Structural evolution is closely related to sandstone uranium mineralization. The present invention provides a method for reshaping the episodic mineralization sequence of basin-type sandstone uranium deposits, which realizes the division of mineralization stages and the reasonable interpretation of effective mineralization age under the constraints of the structural uplift evolution history of the mining area. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A flow chart of a method for reshaping the episodic mineralization sequence of basin-type sandstone-type uranium deposits provided by the present invention;

[0039] Figure 2 The thermal history simulation results and mineralization stage division diagram of two detrital apatite samples in the Qianjiadian ore cluster area of ​​the Songliao Basin in the embodiment of the present invention (the black curve represents the optimal thermal history path);

[0040] Figure 3 This is the U-Pb isochron age diagram of sandstone ore in the same hole of Qianjiadian ore cluster area in Songliao Basin in the embodiment of the present invention;

[0041] Figure 4 This is a microscopic identification result of the uranium occurrence form of sandstone ore in the Qianjiadian ore concentration area of ​​the Songliao Basin in the embodiment of the present invention: Figure 4 a is the optical thin section image of the ore sample, Figure 4 b is the local position element surface scan image, Figure 4 c is the backscatter image of the scanning electron microscope, Figure 4 d is the semi-quantitative component analysis diagram of the energy spectrum;

[0042] Figure 5 This is a time series diagram of the curtain-type uranium mineralization of the sandstone in the Qianjiadian ore cluster area of ​​the Songliao Basin in the embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0044] like Figure 1 As shown, the present invention provides a method for reshaping the episodic mineralization sequence of basin-type sandstone-type uranium deposits, which specifically includes the following steps:

[0045] Step (1) uses structural low-temperature thermochronology or stratigraphic stripping inversion to restore the structural uplift history of the ore-bearing strata in the uranium ore-rich area of ​​the basin, and comprehensively divides the potential multi-stage uranium mineralization stage; the specific steps are as follows:

[0046] Step (1.1), using stratum backstripping or thermal history simulation technology, restore the subsidence and uplift evolution history of the ore-bearing strata in the uranium ore-rich area of ​​the basin, and obtain the evolution history curve of the ore-bearing strata in the uranium ore-rich area.

[0047] Stratigraphic stripping is a conventional technique in basin analysis. When there are many physical data such as borehole and core porosity and permeability in the working area, this technical method can be used to invert the stratigraphic uplift history; when sandstone samples with a large burial depth in the area can be obtained, structural low-temperature thermochronology technology can be used; so the specific method can be selected according to the data at hand. Since sandstone-type uranium deposits are shallowly buried, the thermal history simulation mainly uses the fully annealed detrital apatite fission track method or (U-Th) / He method with a large burial depth, which can better reflect the lower temperature evolution history experienced by the stratum.

[0048] Step (1.2): Based on the acquired evolution history curve of the ore-bearing strata in the uranium ore cluster area and on the basis of structural compression-strata uplift, the potential multi-stage uranium mineralization stages are comprehensively divided.

[0049] For example, the thermal history simulation technology is used to restore the settlement and uplift evolution history of the ore-bearing strata in the Qianjiadian uranium ore cluster in the Songliao Basin. First, several sandstone samples of the Yaojia Formation ore-bearing strata in the mining area are collected (other strata underlying the ore-bearing strata can also be collected). In order to ensure that the fission track of the detrital apatite in the sandstone can be completely annealed, sandstone samples from deeply buried strata should be collected as much as possible. Then, the selection of detrital apatite single minerals and their fission track analysis are carried out to obtain data such as the fission track age and length of the samples. The fully annealed samples with track ages younger than their stratigraphic ages are selected to carry out thermal history simulation, as shown in Table 1, so as to obtain the thermal history evolution curve of the ore-bearing strata. According to the stratum compression uplift-infiltration uranium oxide mineralization theory, four main uranium mineralization stages are finally divided, such as Figure 2 As shown, it includes the pre-enrichment stage of sedimentation and burial of ore-bearing layers (about 90 to about 70 Ma), the main mineralization stage 1 (about 65 to about 55 Ma), the main mineralization stage 2 (about 45 to about 30 Ma), and the main mineralization stage 3 (about 30 to about 15 Ma).

[0050] Table 1 Results of fission track analysis of detrital apatite in Qianjiadian area

[0051]

[0052] Step (2), in the above step (1), systematically collect sandstone ore from several industrial uranium mine holes in the uranium ore concentration area, and carry out trace element and Ra analysis of the ore; the specific steps are as follows:

[0053] Step (2.1), select drill holes with developed industrial uranium ore bodies in the uranium ore concentration area to collect sandstone uranium ore samples, and ensure that the number of ore samples collected continuously from the main ore section in each hole is more than 3 pieces, so that isochron age fitting can be carried out later;

[0054] Step (2.2), some sandstone uranium ore samples were crushed into 200 mesh powder samples in the laboratory, and then trace elements such as U, Th, Mo, Pb and Ra content were analyzed.

[0055] For example, sandstone ore samples were continuously collected in the main mining section of 6 industrial wells in the Qianjiadian mining area, with the number of samples in each well being more than 3. Afterwards, tests were carried out on the powder samples of sandstone ore and their uranium, radium and other contents. The results are shown in Table 2.

[0056] Step (3), performing whole-rock U-Pb isotope dating of the sandstone uranium ore in the same hole with U-Ra balance correction, using isotope dilution-thermal ionization mass spectrometry (ID-TIMS); the specific steps are as follows:

[0057] Step (3.1), testing the uranium and lead isotope compositions of the sandstone uranium ore powder sample of the above step (2.2) using a mass spectrometer;

[0058] Step (3.2), using the U and Ra contents obtained in the above step (2.2), perform U-Ra balance correction on the isotopic composition data of the sandstone uranium ore in the same hole to obtain the corrected isotope ratio 238 U / 204 Pb, 235 U / 204 Pb data

[0059] Using the U and Ra contents obtained in the above step (2.2), based on the correction formula Kp = Ra / (U×0.01241), where Ra and U are the contents measured today, the ancient uranium content of the sample (Up = U×Kp) and the corrected isotope ratio ( 238 U / 204 Pb)p= 238 U / 204 Pb×Kp and isotope ratios ( 235 U / 204 Pb)p= 235 U / 204 Pb × Kp;

[0060] Step (3.3), using the corrected isotope ratio obtained in step (3.2) 238 U / 204 Pb, 235 U / 204 Pb data, uranium and lead isotope composition data obtained in step (3.1), use Isotope or Excel software to fit the isochron age of sandstone uranium ore in the same hole, and obtain the key mineralization time points in different stages

[0061] The sandstone uranium ore in the same borehole was grouped and the U-Pb ( 238 U- 206 Pb or 235 U- 207 Pb) or Pb-Pb( 207 Pb- 206 Pb) isochron age fitting (all three isochron ages can be used) to obtain the key mineralization time points in different stages.

[0062] For example, all sandstone ores collected from the six industrial wells were tested for uranium and lead isotope composition; then, the paleouranium content Up and ( 238U / 204 Pb)p ratio, the results are shown in Table 2.

[0063] Since the initial lead (also known as common lead) content of sandstone uranium ore is very high, it is difficult to calibrate the initial lead, which makes the sandstone uranium ore samples of the same mineralization period have different age results, and their apparent age has lost practical significance. Therefore, this time, the ore samples of the same hole were corrected by Isochron software loaded in EXCEL ( 238 U / 204 Pb)p and lead isotope composition were used to fit the age and obtain a more realistic 238 U- 206 Pb isochron mineralization age, such as Figure 3 As shown, the mineralization age of the ZKXing 29-22 ore body in borehole is 91.4±5.8Ma, the mineralization age of the ZKH2-2 ore body in borehole is 78.4±5.5Ma, the mineralization age of the ZKH0-2 ore body in borehole is 57.3±2.6Ma, the mineralization age of the ZKXing 125-9-12 ore body in borehole is 38.4±2.47Ma, the mineralization age of the ZKXing 97-7 ore body in borehole is 25.6±3.04Ma, and the mineralization age of the ZKL16-7 ore body in borehole is 44.4±5.6Ma.

[0064]

[0065]

[0066] Step (4), conducting a study on the occurrence form of uranium in the sandstone uranium ore sample with a high uranium content (U content>1000ppm) in the above step (2); the specific steps are as follows:

[0067] Step (4.1), using the trace element content data as a reference, select a uranium-rich sandstone ore sample with a uranium content greater than 1000 ppm, and grind parallel samples of a light slice and a probe slice at the same position of the ore sample;

[0068] Step (4.2), the ground thin slice is carbon-plated (to increase conductivity), and then placed in a scanning electron microscope equipped with an energy spectrometer to carry out microscopic mineralogy and semi-quantitative elemental geochemical composition analysis of the development location, morphology, composition, etc. of uranium minerals, and circle out unaltered (relatively good crystal form, large particle size) uranium minerals.

[0069] For example, the uranium-rich sandstone ore samples S14-193, Xing 97-7-2, Xing 97-7-6, Xing 97-7-7, Xing 9-12-1 to Xing 9-12-5, L7-5, L7-9, L7-12, and L7-16 in the boreholes were firstly subjected to optical thin sectioning (e.g. Figure 4a) and the probe sheet were ground in parallel; then, the carbon-coated optical slice was scanned for local elements (as shown in Figure 4 b), scanning electron microscope backscatter image identification (as shown in Figure 4 c), semi-quantitative component analysis of energy spectrum (such as Figure 4 d) and other work, it was basically obtained that the main mineral type in the optical thin section field of view is pitchblende, and the development location of pitchblende with good crystallization and large particle size was delineated, laying the foundation for the next step of in situ U-Pb dating of uranium mineral micro-areas.

[0070] Step (5), conducting micro-area in-situ U-Pb isotope dating on the uranium minerals identified in step (4), using dating techniques including electron probe analysis and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS); the specific steps are as follows:

[0071] Step (5.1): Conduct electron probe in situ U-Pb isotope dating of the uranium minerals circled on the optical thin section.

[0072] Based on the uranium, thorium and lead contents obtained by the electron probe, the apparent age of the uranium mineral is calculated using the formula t=7550Pb / (U+0.365Th). U, Th and Pb are the uranium, thorium and lead contents obtained by the electron probe, respectively, in mass percentage; t is the apparent age of the uranium mineral, in millions of years.

[0073] Step (5.2), LA-ICP-MS micro-area in situ U-Pb isotope dating of uranium minerals on the parallel sample of the probe sheet corresponding to the optical thin section

[0074] The apparent age of each measuring point is calculated based on the uranium and lead isotope composition. Specifically, refer to the common formula given in the uranium-lead radiochronology chapter in the geochemistry textbook, t=ln(1+D* / N) / λ, where D* represents the ratio of the accumulated decay products to the remaining amount of the original isotope, N is the number of atoms of the original isotope, λ is the decay constant, and t is the desired rock age. The isotope composition data of all measuring points can also be imported into the Isolope software for processing to fit the isochron age of uranium mineral formation, where the isochron equation is: 206 Pb / 204 Pb=( 206 Pb / 204 Pb) 0 + 238 U / 204 Pb[Exp(λ 8 t)-1], the decay constant λ of 238U 8 =0.155125×10 -9 a-1 (a is year), ( 206 Pb / 204Pb) 0 =9.307. For example, electron probe analysis was performed on pitchblende delineated in thin sections of multiple rich ore sandstones of the Yaojia Formation in the Qianjiadian ore cluster. PbO was detected at four points, but ThO was not detected. 2 The apparent age of the uranium minerals is between 3.0Ma and 6.01Ma according to the calculation formula, as shown in Table 3, which can be considered as the superposition and transformation time of the ore body. At the same time, the uranium-lead isotope composition of the pitchblende on the probe sheet (relatively thick and cannot be penetrated by laser ablation) was tested by LA-ICP-MS, with a total of 57 points tested. 235 U / 207 The apparent Pb age ranges from 1.3Ma to 8.9Ma, with most of them being less than 3Ma. 238 U / 206 The apparent age of Pb is between 0.6Ma and 3.9Ma, as shown in Table 4, and most of them are less than 2Ma; it can be regarded as the youngest superimposed transformation age of the ore body; the isotopic composition measurement point data of all uranium minerals failed to fit the isochron age, which is related to the difference in the degree of uranium and lead loss of pitchblende in different parts of the ore.

[0075] Table 3 Results of electron probe dating of bituminous uranium ore in sandstone-rich ore of Qianjiadian ore cluster in Songliao Basin

[0076]

[0077]

[0078] Table 4 In situ LA-ICP-MS U-Pb dating data of the pitchblende micro-area in the Qianjiadian ore cluster in the Songliao Basin

[0079]

[0080] Step (6): Reconstruct the sandstone curtain uranium mineralization time sequence based on the data results of the above steps (1), (3) and (5). The specific steps are as follows:

[0081] The three continuous mineralization stages of sandstone-type uranium deposits are comprehensively divided into early, middle and late stages: pre-enrichment stage, main redox mineralization stage and superimposed transformation mineralization stage. The isochron age data older than the stratigraphic age of the ore-bearing layer are eliminated, and then the ages are sorted from large to small to obtain the pulsating key mineralization time points in each stage. The apparent age and isochron age data of in-situ U-Pb dating of uranium mineral micro-areas are taken as the superimposed transformation time. Finally, a time series chart of episodic mineralization of sandstone-type uranium deposits in the basin is constructed.

[0082] For example, based on the results of tectonic thermal history simulation of the Qianjiadian ore cluster in the southwestern Songliao Basin, the isochron age of single-hole sandstone uranium ores and the in-situ U-Pb dating results of uranium mineral micro-areas, the uranium mineralization process of the sandstones of the main ore-bearing layers of the Qingshankou Formation-Yaojia Formation in the area was divided into three continuous mineralization stages: sedimentary diagenesis pre-enrichment under the background of tectonic settlement in the early and middle Late Cretaceous, main oxidation-reduction mineralization under the background of tectonic uplift in the late Late Cretaceous-Miocene, and superimposed transformation since the Pliocene; five key mineralization time points of about 90Ma, about 80Ma, about 60Ma, about 40Ma, and about 25Ma were obtained, indicating that the sandstone uranium mineralization was pulsating; it was concluded that the late superimposed transformation was mainly concentrated in about 3Ma to 6Ma and less than about 2Ma; and finally a complete multi-stage pulsating mineralization time series of the Upper Cretaceous red variegated sandstone in the Qianjiadian ore cluster was constructed, such as Figure 5 shown.

[0083] The present invention can be widely used in scientific research on the evaluation of sandstone-type uranium mineralization prospects and mineralization models in Mesozoic and Cenozoic sedimentary basins at home and abroad. The method provided by the present invention can quickly and comprehensively restore the complete curtain-type uranium mineralization process of the main ore-bearing sandstone layer in the uranium ore concentration area, provide reference and guidance for the reasonable prediction of the peripheral sandstone uranium mineralization prospects and the deployment of prospecting and exploration, reduce the blindness of exploration to a great extent, and have important practical application and promotion value.

[0084] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the present invention can adopt the existing technology.

Claims

1. A method for reconstructing the episodic mineralization sequence of sandstone-type uranium deposits in a basin, characterized in that: The method comprises: Step (1), using structural low-temperature thermochronology technology or stratum backstripping technology to invert, restore the structural uplift history of the ore-bearing strata in the uranium ore-rich area of ​​the basin, and comprehensively divide the potential multi-stage uranium mineralization stage; Step (2), systematically collecting sandstone ore from different industrial uranium mine holes in the selected uranium ore cluster area, and conducting trace element and Ra analysis of the ore; Step (3), performing U-Ra balance-corrected whole-rock U-Pb isotope dating on the sandstone uranium ore in the same hole to obtain key mineralization time points at different stages; Step (4), conducting a study on the occurrence form of uranium in a sandstone uranium ore sample with a high uranium content; Step (5), conducting micro-area in-situ U-Pb isotope dating on the identified uranium minerals; Step (6): Reconstruct the sandstone curtain uranium mineralization time sequence based on the comprehensive division of multiple uranium mineralization stages, key mineralization time points in different stages, and micro-area in situ U-Pb isotope dating data.

2. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 1, characterized in that: The step (1) comprises: Step (1.1), using stratum stripping or thermal history simulation technology, restore the subsidence and uplift evolution history of the ore-bearing strata in the uranium ore-rich area of ​​the basin, and obtain the evolution history curve of the ore-bearing strata in the uranium ore-rich area; Step (1.2): Based on the acquired evolution history curve of the ore-bearing strata in the uranium ore cluster area and on the basis of structural compression-strata uplift, the potential multi-stage uranium mineralization stages are comprehensively divided.

3. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 1, characterized in that: The step (2) comprises: Step (2.1), selecting different industrial uranium mine holes in the uranium ore concentration area to collect sandstone uranium ore samples, and collecting sandstone uranium ore samples of different grades; Step (2.2), crush the sandstone uranium ore sample, and analyze the trace elements and Ra of the ore.

4. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 3 is characterized in that: The trace elements in the ore in step (2) include U, Th, Mo and Pb.

5. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 4, characterized in that: The step (3) comprises: Step (3.1), testing the uranium and lead isotope compositions of the sandstone uranium ore powder sample of step (2.2) using a mass spectrometer; Step (3.2), using the U and Ra contents obtained in step (2.2), perform U-Ra balance correction on the isotopic composition data of the sandstone uranium ore in the same hole to obtain the corrected isotope ratio 238 U / 204 Pb, 235 U / 204 Pb data; Step (3.3), using the corrected isotope ratio obtained in step (3.2) 238 U / 204 Pb, 235 U / 204 Based on the Pb data and the uranium and lead isotope composition data obtained in step (3.1), the isochron age fitting of the sandstone uranium ore in the same hole was performed using Isotope or Excel software to obtain the key mineralization time points in different stages.

6. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 5, characterized in that: The step (3.2) is specifically as follows: using the U and Ra contents obtained in step (2.2), based on the correction formula Kp=Ra / (U×0.01241), where Ra and U are the contents measured today, the ancient uranium content of the sample (Up=U×Kp) and the corrected isotope ratio ( 238 U / 204 Pb)p= 238 U / 204 Pb×Kp and isotope ratios ( 235 U / 204 Pb)p= 235 U / 204 Pb×Kp.

7. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 4, characterized in that: The step (4) comprises: Step (4.1), select the sandstone uranium ore sample with high uranium content in step (2), and grind parallel samples of the optical thin slice and the probe slice at the same position of the ore sample; Step (4.2), carbon-coating the ground thin sections, conducting microscopic mineralogy and semi-quantitative elemental geochemical composition analysis, and circling out the unaltered uranium minerals.

8. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 7, characterized in that: The step (5) comprises: Step (5.1), conduct electron probe in situ U-Pb isotope dating on the uranium minerals circled on the optical thin section; Step (5.2), perform LA-ICP-MS micro-area in situ U-Pb isotope dating on the uranium minerals on the parallel sample of the probe sheet corresponding to the optical thin section.

9. The method for reconstructing the episodic mineralization sequence of basin-type sandstone-type uranium deposits according to claim 8, characterized in that: The step (5.1) is specifically as follows: according to the uranium, thorium and lead contents obtained by the electron probe, the apparent age of the uranium mineral is calculated using the formula t=7550Pb / (U+0.365Th); wherein U, Th and Pb are the uranium, thorium and lead contents obtained by the electron probe, respectively, in units of mass percentage; and t is the apparent age of the uranium mineral, in units of millions of years; The step (5.2) is specifically as follows: based on the U and Pb isotope ratios obtained by mass spectrometry, the age calculation formula commonly used in radioactive geochemistry and Isotope related processing software are used to obtain the apparent age and isochron age of the uranium mineral formation.

10. The method for reconstructing the episodic mineralization sequence of basin-type sandstone uranium deposits according to claim 1, characterized in that: The step (6) is specifically as follows: comprehensively dividing the early, middle and late three continuous mineralization stages of the sandstone-type uranium deposit into: pre-enrichment stage, oxidation-reduction main mineralization stage, and superposition transformation mineralization stage; eliminating isochron age data that are older than the stratigraphic age of the ore-bearing layer, and then sorting the ages from large to small to obtain the pulsating key mineralization time points in each stage; using the apparent age and isochron age data of in-situ U-Pb dating of uranium mineral micro-areas as the superposition transformation time; Finally, a time series chart of episodic mineralization of sandstone-type uranium deposits in the basin was constructed.

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