Method for determining uranium mine target area based on alteration type of granite

Abstract

The invention discloses a method for determining a uranium mine target area based on the alteration type of granite, and the method comprises the steps: obtaining samples in a primary target area, and recording the position information of each sample; obtaining the chemical composition of the sample; determining the alteration type of the sample based on the chemical composition; screening the sample of which the alteration type is illite petrochemical, chlorite or pyrite as a primarily screened sample, and calculating the molar ratio of Fe < 3 + > to Fe < 2 + > of the primarily screened sample; screening the primarily screened sample with Fe < 3 + > / Fe < 2 + > greater than 1 as a target sample, and determining the position information of the target sample as a uranium ore target area; the cost of uranium prospecting work is remarkably reduced, the success rate of uranium prospecting is increased, and the method has wide reproducibility and operability and has good application prospects.

Description

Technical Field

[0001] The invention relates to the field of uranium geological research, and in particular provides a method for determining a uranium target area based on the alteration type of granite. Background Art

[0002] Granite-type uranium deposits are one of the most important types of uranium deposits in my country. This type of uranium resources accounts for about 20% of the total uranium resources that have been identified in my country, and are concentrated in South my country. The depth of uranium exploration in this area was generally shallow (concentrated within 500m underground), and faced the crisis of gradual resource depletion. "Exploring deep to find blind spots" has become an urgent direction to be overcome in the later exploration of granite-type uranium deposits in South China.

[0003] Previous researchers have conducted a lot of research on the classification of uranium mineralization types in granite-type areas in South China, the geological characteristics of key ore fields and deposits, and the laws of mineralization. Most of these studies focus on the source and migration of uranium in the mineralization process, but these studies cannot be directly used to guide the determination of the precise location or construction location of the final uranium mineralization. In the process of prospecting for minerals in depth, a lot of indoor and outdoor work is often required to determine the mineral points, which is time-consuming and economically costly. There is an urgent need for a low-cost method to determine the target area of ​​uranium deposits as a method for further in-depth work to finally confirm the location of the deposit. Summary of the invention

[0004] In order to overcome the defects of the prior art, the object of the present invention is to at least provide a novel method for determining a uranium ore target area based on the alteration type of granite.

[0005] The present invention provides a method for determining a uranium ore target area based on the alteration type of granite, comprising the following steps:

[0006] S1, obtaining samples in the primary target area and recording the location information of each sample;

[0007] S2, obtaining the chemical composition of the sample;

[0008] S3, determining the alteration type of the sample based on the chemical composition, the alteration type comprising one or more of silicification, greisenization, feldsparization, chloritization, sericitization, pyritization, illitization, calciteization and fluoritization; the chemical composition comprising at least one selected from the molar amount of Si, Na, K, Ca, Fe, Mg, Ti, Al, and the chemical composition further comprising at least one selected from the mass percentage of K2O, MgO, Na2O, CaO and FeO;

[0009] S4, screening the samples with the alteration type of illitization, chloritization, calciteization or pyritization as the primary screening samples, and calculating the Fe 3+ / Fe 2+The molar ratio of

[0010] S5, Screening Fe 3+ / Fe 2+ >1 is the target sample, and the location information of the target sample is determined as the uranium ore target area.

[0011] In the present invention, the chemical compositions expressed by metal oxides (such as FeO, MgO, CaO, Na2O, K2O, etc.) are all mass fractions, and the chemical compositions expressed by metal elements (such as Si, Na, K, Ca, Fe, Mg, Ti, Al, Fe 3+ , Fe 2+ The molar fractions of the elements are calculated based on the mass fractions.

[0012] The above method can quickly locate samples with superposition of oxidative and reduced hydrothermal alteration. Oxidized uranium is more likely to migrate and activate, while reduced uranium is more likely to precipitate and enrich. There is evidence that samples that have undergone oxidative and reduced hydrothermal alteration will have greater mineralization potential. By studying the chemical composition of the sample to determine the superposition of hydrothermal alteration and then determine the uranium ore target area, the time and economic cost in the prospecting process can be significantly reduced.

[0013] In some embodiments, in step S1, samples that are greisenized and silicified are removed based on the observation of hand specimens, and then step S2 is performed.

[0014] In some embodiments, in step S3, the sample is simultaneously observed under a microscope to determine the type of alteration.

[0015] In some embodiments, in step S5, screening 1 <Fe 3+ / Fe 2+ The primary screening samples with a concentration <20% are target samples.

[0016] In some embodiments, in step S5, screening 1 <Fe 3+ / Fe 2+ <10 of the primary screening samples are target samples.

[0017] In some embodiments, in step S5, the target sample is also observed under a microscope to determine the superposition characteristics of alteration, and the target sample whose hematite alteration is later than the reductive alteration is screened as the optimized target sample, and the reductive alteration includes one or more of illite alteration, chlorite alteration or pyritization, and the location information of the optimized target sample is determined as the uranium target area.

[0018] The beneficial effects of the present invention are:

[0019] Compared with the prior art, the method for determining the target area of ​​uranium ore based on the alteration type of granite provided by the present invention obtains the composition data of the sample through chemical analysis, and then selects the samples that have undergone illitization, chloritization or pyritization, and further selects the samples that have undergone Fe 3+ / Fe 2+ The molar ratio of uranium to uranium is used to select samples with a higher probability of mineralization, and the location information of these samples is determined as the points and areas for further prospecting and mining. This significantly reduces the cost and success rate of uranium prospecting, has wide replicability and operability, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A photo of a sample hand specimen in an embodiment of the present invention;

[0021] Figure 2 This is a microscopic photograph of a sample in an embodiment of the present invention;

[0022] Figure 3 A is the Ai index-CCPI index diagram in the embodiment of the present invention;

[0023] Figure 3 B is U-Fe in the embodiment of the present invention. 3+ / Fe 2+ Graphics;

[0024] In the figure, Qz-quartz, Kf-potassium feldspar, Chl-chlorite, Ill-illite, Hem-hematite; U-potential abnormal point of uranium mineralization.

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. DETAILED DESCRIPTION

[0026] The present invention can be further understood through the specific examples of the present invention given below.

[0027] This embodiment provides a method for determining a uranium ore target area based on the alteration type of granite, comprising the following steps:

[0028] S1, obtaining samples in the primary target area, and recording the location information of each sample, the location information includes but is not limited to GPS information, information of overlying rock mass and underlying rock mass, surrounding rock, depth, lithology, borehole number, etc., which can re-determine the sampling location of the sample; we found that greisenization and silicification have nothing to do with uranium mineralization, and some may even cause uranium ore to become depleted. Therefore, in some embodiments, in step S1, samples with strong greisenization and silicification are eliminated based on the observation of hand specimens, and then step S2 is executed to reduce the analysis cost.

[0029] S2, obtaining the chemical composition of the sample, and determining the composition of major elements and / or trace elements of the sample by existing methods in the prior art;

[0030] S3. Determine the alteration type of the sample based on the chemical composition, the alteration type including one or more of silicification, greisenization, feldsparization, chloritization, sericiteization, pyritization, illiteization, calciteization and fluoritization; the chemical composition includes at least one of the molar amounts selected from Si, Na, K, Ca, Fe, Mg, Ti, and Al, and the chemical composition also includes at least one of the mass percentages selected from K2O, MgO, Na2O, CaO, FeO, etc. Specifically, the Q index combined with the P index and the B index combined with the A index diagrams are used to indicate the alteration types such as silicification-greisenization-potash feldsparization-chloritization, the (Na+K+2Ca) / Al vs. K / Al diagram is used to indicate the KH replacement alteration type, and the Ai index vs. CCPI index diagram is used to indicate the alteration types such as sericitization-chloritization / pyritization-carbonatization, among which the Q index is the molar amount of Si / 3-(Na+K+2Ca / 3), the P index is the molar amount of K-(Na+Ca), the B index is the molar amount of Fe+Mg+Ti, the A index is Al-(Na+K+2Ca), the CCPI index is 100*(MgO+FeO) / (MgO+FeO+Na2O+K2O), and the Ai index is 100*(K2O+MgO) / (K2O+MgO+Na2O+CaO). The chemical composition can be used to determine the type of alteration of the sample according to the above method.

[0031] S4, screening the samples with the alteration type of illitization, chloritization, calciteization or pyritization as the primary screening samples, and calculating the Fe 3+ / Fe 2+ Molar ratio, Q index, P index and CCPI index;

[0032] S5, Screening Fe 3+ / Fe 2+ >1 is the target sample, and the location information of the target sample is determined as the uranium ore target area.

[0033] As a variable valence element, the activity of U is highly related to the redox environment. Generally, the oxidized U element is more active and is easy to migrate with the fluid and activate from the source rock, creating conditions for enrichment and mineralization; at the same time, the reduced U element is less active, and the low oxygen fugacity environment can constitute a reduction barrier for the fluid rich in oxidized U, thereby causing the oxidized U to be reduced and precipitated into minerals. Therefore, for a mineralization point, if it has undergone reductive alteration (such as illitization, chloritization, calciteization or pyritization) before mineralization, it can become a reduction barrier, and uranium mineralization often presents the characteristics of oxidative alteration (such as hematite). The S4 step is used to screen out the samples of reductive alteration to preliminarily screen out the points that can become reduction barriers, and then the S4 step is used to find the samples with oxidative alteration, and the uranium mineralization points will belong to the collection of these target samples.

[0034] Preferably, in some embodiments, in step S5, the target sample is also observed under a microscope to determine the superposition characteristics of alteration, and the target sample whose hematite alteration is later than the reductive alteration is screened as the optimized target sample, and the reductive alteration includes one or more of illite alteration, chlorite alteration or pyritization, so that samples that are first oxidized and then reduced can be excluded, thereby further narrowing the screening range of potential uranium target areas, and determining the location information of the optimized target sample as the uranium target area.

[0035] In this embodiment, the method for determining the uranium target area based on the alteration type of granite in the present application is used to determine the uranium target area in the Yangjiaonao deposit.

[0036] S1, a total of 72 samples were obtained in the primary target area, and the GPS, core number and depth information of each sample were recorded;

[0037] S2, the major element analysis of the samples was completed by inductively coupled plasma spectrometer (ICP-OES) in Nanjing Hongchuang Geological Exploration Technology Service Co., Ltd., and the trace element analysis was completed by Agilent 7900 inductively coupled plasma mass spectrometer (ICP-MS) in Nanjing Hongchuang Geological Exploration Technology Service Co., Ltd. The chemical parameter results of all samples refer to Tables 1 and 2, where the major elements are mass percentages, and all data retain one significant digit of the decimal point.

[0038]

[0039]

[0040] Table 1 Chemical composition of samples No. 1-35

[0041]

[0042] Table 2 Chemical composition of samples No. 36-72

[0043] S3, determining the alteration type of the sample based on the chemical composition, the alteration type comprising one or more of silicification, greisenization, feldsparization, chloritization, sericitization, pyritization, illitization, calciteization and fluoritization.

[0044] Of course, it can be combined with hand specimens (ref. Figure 1 The sample shown in the figure can be observed to have illitized + chloritized + pyritized alteration) and microscopic characteristics (reference Figure 2 , illitized and chloritized altered rocks are replaced by comb-shaped quartz veins and superimposed with vein-like hematite) to determine the alteration type of the sample. Figure 3 As shown in A, the alteration type of sample group 1 is greisenization alteration, and the CCPI index of sample groups 2-4 increases significantly, but the Ai index does not change significantly, indicating that K is lost and Fe is introduced during the alteration of these samples. The relevant samples have undergone illitization of potassium feldspar, chloritization of sericite / biotite, and pyritization (ref. Figure 3 A).

[0045] S4, in this embodiment, exclude sample group 1 that has only undergone greisenization, select sample groups 2-4 with the alteration types of illitization, chloritization, and pyritization as the primary screening samples, and calculate the Fe 3+ / Fe 2+ As a comparison, the Fe 3+ / Fe 2+ The molar ratio was calculated, referring to Table 1-2 and Figure 3 B.

[0046] S5, reference Figure 3 B, Fe of most sample group 2 in the initial screening samples 3+ / Fe 2+ <1, and the U content of these samples is low. These samples have not experienced a process such as oxidation by hydrothermal fluids rich in high-valent U, and their mineralization potential is limited, which is similar to the situation of comparative sample group 1. 3+ / Fe 2+ >1, these two groups of samples are determined as the final target samples. The U content of these samples is high, which also verifies that the target samples determined in this application have good mineralization prospects, and the location information of the target samples is determined as the uranium target area. 3+ / Fe 2+ The target samples (sample group 3 and sample group 4) with a concentration of >1 showed that they had a high oxygen fugacity and superimposed hematite. This showed that due to the superposition of U-containing hydrothermal fluids with a high oxygen fugacity, a large amount of Fe2+ Converted to Fe 3+ Samples with higher U contents all have this characteristic and can be used as uranium target areas for further detailed work.

[0047] We note that when the oxygen fugacity is too high, it is not conducive to the precipitation of the more active hexavalent U into tetravalent U. Therefore, Fe 3+ / Fe 2+ The environment of samples with a value of ≥20 is not conducive to the precipitation of U-rich ore, which will lead to the reactivation of U and reduce the U content (reference Figure 3 B), you can <Fe 3+ / Fe 2+ <20% of the initial screening sample or further 1 <Fe 3+ / Fe 2+ The primary screening samples with a concentration of less than 10% are determined as target samples, which can more accurately locate the uranium ore target area.

[0048] Preferably, in step S5, Figure 2 As shown, observation of the target sample under a reflected light microscope shows that the hematite mineralization of the sample is later than the reductive alteration such as illite and chlorite. Potential abnormal points of U mineralization can be found under the microscope. These samples can be identified as optimized target samples, and their location information can be determined as uranium target areas. Further subsequent work (such as electron probe analysis to determine the properties of potential abnormal points of U mineralization) can be used for mineral exploration.

[0049] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. A method for determining a uranium ore target area based on the alteration type of granite, characterized in that: The steps include: S1, obtaining samples in the primary target area and recording the location information of each sample; S2, obtaining the chemical composition of the sample; S3, determining the alteration type of the sample based on the chemical composition, the alteration type comprising one or more of silicification, greisenization, feldsparization, chloritization, sericitization, pyritization, illitization, calciteization and fluoritization; the chemical composition comprising at least one selected from the molar amount of Si, Na, K, Ca, Fe, Mg, Ti, Al, and the chemical composition further comprising at least one selected from the mass percentage of K2O, MgO, Na2O, CaO and FeO; S4, screening the samples with the alteration type of illitization, chloritization or pyritization as the primary screening samples, and calculating the Fe 3+ / Fe 2+ The molar ratio of S5, Screening Fe 3+ / Fe 2+ >1 is the target sample, and the location information of the target sample is determined as the uranium ore target area.

2. The method for determining a uranium ore target area based on the alteration type of granite according to claim 1, characterized in that: In step S1, greisenized and silicified samples are eliminated based on the observation of hand specimens, and then step S2 is performed.

3. The method for determining a uranium ore target area based on the alteration type of granite according to claim 1, characterized in that: In step S3, the samples are simultaneously observed under a microscope to determine the type of alteration.

4. The method for determining a uranium ore target area based on the alteration type of granite according to claim 1, characterized in that: In step S5, filter 1 <Fe 3+ / Fe 2+ The primary screening samples with a concentration <20% are target samples.

5. The method for determining a uranium ore target area based on the alteration type of granite according to claim 1, characterized in that: In step S5, filter 1 <Fe 3+ / Fe 2+ <10 of the primary screening samples are target samples.

6. The method for determining a uranium ore target area based on the alteration type of granite according to any of the preceding claims, characterized in that: In step S5, the target sample is also observed under a microscope to determine the superposition characteristics of alteration, and the target sample whose hematite alteration is later than the reductive alteration is screened as the optimized target sample, and the reductive alteration includes one or more of illite alteration, chlorite alteration or pyritization, and the location information of the optimized target sample is determined as the uranium target area.

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