Hydrothermal uranium mineralization indication method based on chlorite chemical component analysis

Abstract

The invention belongs to the field of geology and mineral deposit science, and particularly relates to a hydrothermal uranium mineralization indication method based on chlorite chemical component analysis, which comprises the following steps: step (1) sample collection and selection; (2) preparing a polished thin sheet and carrying out microscopic observation; (3) determining and analyzing components of main elements and trace elements in the polished thin section to obtain chemical analysis data; and (4) constructing a uranium mineralization intensity prediction model according to the chemical analysis data. According to the method, the proportion and spatial distribution of main elements and trace elements in chlorite are systematically analyzed, the uranium mineralization area and scale can be effectively predicted, the uranium ore exploration accuracy can be improved, and the potential mineralization area can be effectively identified.

Description

Technical Field

[0001] The invention belongs to the field of geology and ore deposits, and in particular relates to a hydrothermal uranium mineralization indication method based on chlorite chemical composition analysis. Background Art

[0002] Hydrothermal uranium deposits are an important source of uranium resources, and their formation process is usually accompanied by complex hydrothermal activity and mineral changes. Traditional uranium exploration methods mostly rely on direct analysis of uranium minerals, but because uranium minerals are easily affected by later geological transformations, direct dating and mineralization predictions are often uncertain. Chlorite, as a common mineral, is widely found in hydrothermal alteration environments, especially in hydrothermal activity areas related to uranium mineralization. The chemical composition of chlorite, especially the proportions of major elements such as Al, Fe, and Mg and the distribution of trace elements, reflects the characteristics of the hydrothermal environment when it was formed. Therefore, by analyzing the chemical composition of chlorite, important information about the intensity of hydrothermal activity and mineralization potential can be obtained.

[0003] Current research shows that the chemical composition of chlorite can serve as an important mineral marker for hydrothermal uranium mineralization. For example, chlorite with high AlIV content and low Fe / (Fe+Mg) ratio usually indicates strong hydrothermal alteration, which is closely related to the uranium mineralization environment. In addition, the enrichment of trace elements such as U and Th in chlorite can also directly reflect the intensity of uranium mineralization. However, existing research has mostly focused on the role of chlorite in hydrothermal alteration of metal deposits such as lead, zinc and copper, and there is still a lack of systematic methods to apply the chemical composition analysis of chlorite to the exploration of hydrothermal uranium deposits. Summary of the invention

[0004] The purpose of the present invention is to provide a method for indicating hydrothermal uranium mineralization based on the analysis of the chemical composition of chlorite. The method can effectively predict the area and scale of uranium mineralization by systematically analyzing the proportions and spatial distribution of major elements and trace elements in chlorite, which can not only improve the accuracy of uranium exploration, but also effectively identify potential mineralized areas.

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

[0006] A method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis, the method comprising:

[0007] Step (1) sample collection and selection;

[0008] Step (2) optical thin-section preparation and microscopic observation;

[0009] Step (3) determining and analyzing the main elements and trace elements in the optical slice to obtain chemical analysis data;

[0010] Step (4) constructs a prediction model for uranium mineralization intensity based on chemical analysis data.

[0011] The step (1) specifically comprises: measuring the profile of a borehole or underground tunnel, dividing the alteration zones perpendicular to the strike direction of the ore body, and recording geological information data; marking sampling points on each alteration zone, and systematically collecting rock samples.

[0012] The geological information data include: sample collection location, surrounding rock lithology, alteration type, mineralization intensity and ore-bearing structure.

[0013] The step (2) specifically comprises: making the collected samples into optical thin slices for electron probe microanalysis to ensure that the samples are uniform; and using a mineralogy microscope to observe in detail the occurrence and morphology of chlorite in different alteration zones and mineralization zones.

[0014] The step (3) specifically comprises: using electron probe microanalysis to quantitatively analyze the main elements in the optical thin slice sample, and using laser ablation inductively coupled plasma mass spectrometry to quantitatively analyze the key trace elements in the optical thin slice sample to obtain chemical analysis data.

[0015] The main elements include Si, Al, Fe, and Mg, the key trace elements include Ti, Mn, Cr, U, and Th, and the chemical analysis data include AlIV value, Fe / (Fe+Mg) ratio, and U and Th contents.

[0016] The step (4) is specifically as follows: using the obtained chemical analysis data, comparing the chemical composition differences of chlorite in the known uranium mineralized zone and non-mineralized zone, and determining the key indicators related to mineralization. By comparing the chemical analysis data, the indicator characteristics of the mineralization intensity are identified, a geochemical model is established, the critical value for identifying the uranium mineralization potential zone is determined, and a prediction model for the uranium mineralization intensity is constructed.

[0017] In the step (4), by comparing the AlIV value, Fe / (Fe+Mg) ratio and U and Th contents in the chlorite sample, the indicator characteristics of the mineralization intensity are identified, a geochemical model is established, and the critical values ​​of high AlIV content and high Fe / (Fe+Mg) ratio are determined to identify the uranium mineralization potential area; according to the distribution of U and Th contents in the chlorite, a prediction model for uranium mineralization intensity is constructed.

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

[0019] 1. The present invention provides a method for indicating hydrothermal uranium mineralization based on the chemical composition analysis of chlorite, by analyzing the Al IV The content, Fe / (Fe+Mg) ratio and the distribution of trace elements such as U and Th provide more reliable indications of uranium mineralization. IVChlorite with high content and low Fe / (Fe+Mg) ratio often corresponds to strong hydrothermal alteration areas. Through the systematic analysis of these chemical indicators, potential uranium mineralization zones can be accurately identified, the risk of blind drilling can be reduced, the efficiency and success rate of prospecting can be improved, and the mineral exploration cycle can be effectively shortened. It has important promotion value and application prospects, especially in volcanic rock and granite uranium deposits.

[0020] 2. The hydrothermal uranium mineralization indication method based on chlorite chemical composition analysis provided by the present invention is not only applicable to the Xiangshan volcanic rock type uranium ore field, but can also be promoted and applied in the exploration of other hydrothermal uranium deposits in the world. It is suitable for the preliminary and detailed exploration stages to provide reliable mineralization evaluation; it is also suitable for the detection and evaluation of uranium deposits related to hydrothermal activities, and can be widely used in uranium exploration under different geological backgrounds around the world.

[0021] 3. The chemical composition of chlorite records the evolution history of regional hydrothermal fluids. The hydrothermal uranium mineralization indication method based on chlorite chemical composition analysis provided by the present invention can also provide important geochemical evidence for the study of regional geological structure, magmatic activity and mineralization relationship. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The following are photos of typical uranium ore bodies in Zoujiashan and Yunji mining areas in Xiangshan area and microscopic photos of typical altered chlorite (Chl1, Chl2 and Chl3) in the embodiments of the present invention: Figure 1 a is a field photo of a typical alkali-replacement ore body in the Yunji mining area. Figure 1 b is a field photo of acid-base superposition mineralization in Zoujiashan mining area. Figure 1 c is a field photo of a typical acid replacement ore body in Zoujiashan mining area. Figure 1 d is a microscopic photo of Chl1-Y in the Yunji mining area. Figure 1 e is a microscopic photo of Chl1-Z in Zoujiashan mining area. Figure 1 f and g are microscopic photos of Chl2 in Yunji mining area. Figure 1 h, i, and j are micrographs of Chl3 from Zoujiashan;

[0023] Figure 2 This is a box line diagram of trace elements of different types of chlorite in Zoujiashan and Yunji mining areas in Xiangshan area in the embodiment of the present invention: Figure 2 The upper middle figure is a box plot of the trace element contents of Ti, Mn, Zn, V, Cr, Ni, and Sc in chlorite. Figure 2 The lower middle figure is a box plot of the trace element contents of Co, Ga, Sr, Ce, Yb, U, and Pb in chlorite. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] The present invention provides a method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis, which specifically comprises the following steps:

[0026] Step (1) Sample collection and selection

[0027] Based on the detailed observation of the profile of the borehole or underground tunnel, the profile measurement is carried out, and the mineralization zone and alteration zone are divided perpendicular to the direction of the ore body, and the division is accurate, and the geological information data is recorded. The geological information data includes the sample collection location, surrounding rock lithology, alteration type, mineralization intensity and ore-bearing structure, etc. These data provide important reference basis for indoor analysis. After completing the profile measurement and the division of mineralization and alteration zones, the sampling points are accurately marked on each mineralization zone and alteration zone, and rock samples are systematically collected to ensure clear and orderly numbering.

[0028] Step (2) Light slice preparation and microscopic observation

[0029] After the samples were collected from the field and brought back to the laboratory, they were initially crushed and screened, and each sample was processed by rock slicer and hand-processing to make a thin slice suitable for electron probe microanalysis (EPMA) for mineral phase and petrographic observation to ensure that the samples were uniform and suitable for subsequent chemical composition analysis. After that, the occurrence and morphology of chlorite in different alteration zones and mineralization zones were observed in detail using a mineral phase microscope.

[0030] Step (3) Determination and analysis of main elements and trace elements in the optical slice

[0031] The main elements (such as Si, Al, Fe, Mg) in the optical thin film samples were quantitatively analyzed using electron probe microanalysis (EPMA), and the content of key trace elements (such as Ti, Mn, Cr, U, Th) was determined using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The following parameters were mainly determined:

[0032] Al IV Value: Usually, hydrothermal alteration causes Al in chlorite IV The value increases, especially in the uranium mineralized zone, and the increase of this content often indicates strong mineralization;

[0033] Fe / (Fe+Mg) ratio: This ratio reflects the nature of the fluid during the formation of chlorite. A higher ratio usually indicates the presence of reducing fluids, which is closely related to the uranium deposition mechanism.

[0034] U and Th content: The significant enrichment of U and Th in chlorite is an important sign of uranium mineralization, especially in the mineralized zone. The increase in U content directly indicates the concentration of uranium and the intensity of mineralization.

[0035] Step (4) Constructing a prediction model for uranium mineralization intensity based on chemical analysis data

[0036] By using the chemical analysis data obtained, the chemical composition differences of chlorite in known uranium mineralized zones and non-mineralized areas are compared to determine the key indicators related to mineralization. IV Based on the above analysis, a geochemical model was established to determine the high Al IV The critical value of the content and high Fe / (Fe+Mg) ratio is used to identify the potential areas of uranium mineralization; according to the distribution of U and Th contents in chlorite, a prediction model of uranium mineralization intensity is constructed to guide further exploration.

[0037] Example

[0038] Taking the Zoujiashan deposit and the Yunji deposit in Xiangshan area of ​​Jiangxi Province as examples, the present invention provides a hydrothermal uranium mineralization indication method based on chlorite chemical composition analysis, which specifically includes the following steps:

[0039] Step 1. Sample collection and selection

[0040] The Xiangshan uranium ore field is located in southeastern China and is one of the largest volcano-related uranium ore fields in China. The uranium mineralization types in the Xiangshan ore field can be divided into two basic mineralization types, alkaline uranium mineralization and acidic uranium mineralization, according to the relative acidity and alkalinity of the fluid, and alkaline uranium mineralization and acidic uranium mineralization are formed accordingly. At present, only the Yunji deposit in the eastern part of the basin has been found to be a deposit dominated by alkaline uranium mineralization, while the uranium deposits in the northern and central-western parts of the basin are mainly dominated by acidic uranium mineralization. This embodiment selects the Zoujiashan deposit dominated by acidic uranium mineralization and the Yunji deposit dominated by alkaline uranium mineralization as research targets. Chloritization is widely developed in both deposits. In the main mineralization belts and alteration belts of the Zoujiashan and Yunji deposits, multiple sampling points were set up to collect chlorite or chloritized ore and altered surrounding rock samples. The sampling points cover different mineralization stages and alteration types to ensure the representativeness of the samples. Special attention should be paid to areas with intense uranium mineralization and significant hydrothermal alteration to obtain representative chlorite mineralized samples.

[0041] Step 2, optical thin section preparation and microscopic observation

[0042] The collected chlorite-bearing ore samples were preliminarily crushed and screened, the selected sample particles were fixed on a glass slide, and a standard geological thin section grinding and polishing process was used to prepare a thin section with a thickness of about 30 microns. During the grinding process, care should be taken to avoid artificial cracks or breakage to maintain the original structure of the mineral. After the thin section is polished, it is encapsulated with a transparent resin to protect the surface of the thin section and prevent oxidation or further damage of the sample. The encapsulated thin section can be used for subsequent microscopic observation and electron probe microanalysis (EPMA).

[0043] Under the microscope, at least four types of chlorite are identified, depending on their chemical composition and the environment in which they were formed. Two types of chlorite are identified in the Yunji mining area: Chl1-Y and Chl2. Chl1-Y originates from partial or complete alteration of biotite in igneous rocks and is widely distributed around the ore body, which is related to the alteration before uranium mineralization ( Figure 1 d). Chl2 is concentrated in the center of the ore body, closely related to alkali replacement uranium mineralization, and often coexists with uranium minerals ( Figure 1 f, g). In the Zoujiashan mining area, Chl1-Z is similar to Chl1-Y and is widely distributed in the altered surrounding rocks ( Figure 1 e), the alteration range can reach hundreds of meters. Chl3 is modified by late acidic replacement alteration, which is related to uranium-thorium mineralization and often coexists with pitchblende and fluorite ( Figure 1 h, i, j).

[0044] Step 3: Analysis of main and trace components of chlorite micro-area

[0045] Electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used to quantitatively analyze the major elements (such as Si, Al, Fe, Mg) and trace elements (such as Ti, Mn, Cr, U, Th) of thin-section samples. Special attention was paid to Al in chlorite. IV The values, Fe / (Fe+Mg) ratios and the contents of trace elements U and Th are of great significance in reflecting the formation environment of chlorite and its relationship with uranium mineralization.

[0046] The results show that the Al content of chlorite (Chl2) related to alkali metasomatic mineralization in the Yunji deposit is IV The values ​​range from 0.876 to 1.312, while the Al content of chlorite (Chl3) related to acid replacement mineralization in the Zoujiashan deposit is IVThe values ​​are slightly higher, ranging from 1.031 to 1.664, which indicates that the chlorites in both places were formed in an environment with strong hydrothermal activity. The Fe / (Fe+Mg) ratio of chlorite (Chl3) related to acid replacement mineralization is as high as 0.6, which further indicates that its formation temperature is relatively high, which is consistent with the characteristics of the acidic alteration uranium mineralization stage. In the LA-ICP-MS analysis, the chlorite associated with uranium mineralization showed a significant increase in U (51-901ppm) and Th (21-200ppm) content, especially in the Zoujiashan deposit, where the U content of chlorite (Chl3) reached the highest value. The trend of trace element changes in chlorite plays a significant role in indicating uranium mineralization.

[0047] Step 4: Establish the indication standard of chlorite trace elements and characteristic values ​​for uranium mineralization and construct a prediction model for hydrothermal uranium mineralization intensity

[0048] The main and trace elements of chlorite in different mineralized alteration zones and surrounding rocks vary greatly. IV The high Fe / (Fe+Mg) value (1.031-1.664), the high Fe / (Fe+Mg) ratio (greater than 0.6), and the significantly enriched U (51-901ppm) and Th (21-200ppm) contents are important geochemical markers indicating uranium mineralization in the Xiangshan area. These characteristics not only reflect the hydrothermal environment when chlorite was formed, but also indicate the potential intensity of uranium mineralization. Specifically, these chemical characteristics of chlorite (Chl3) related to acid replacement mineralization indicate its distribution in highly mineralized areas, which is particularly suitable for identifying new uranium mineralization zones.

[0049] Using the chlorite geochemical indicators constructed above, the chemical composition of chlorite was analyzed in the unexplored areas of Xiangshan area, especially in the peripheral areas of Zoujiashan deposit. IV The potential uranium mineralization zones can be identified by comprehensive evaluation of Fe / (Fe+Mg) value, Fe / (Fe+Mg) ratio and U and Th contents.

[0050] The invention is applicable to hydrothermal uranium deposits worldwide, and is particularly applicable to most hydrothermal uranium deposits in southern my country. It has been applied in prospecting and exploration of multiple uranium deposits in the Xiangshan uranium field in southern my country, and has achieved remarkable results.

[0051] The above implementation scheme is only a preferred example for the Xiangshan volcanic rock type uranium ore field, but the present invention is not limited to the above implementation case. Within the knowledge of technicians in this field, various other changes and modifications can be made 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 indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis, characterized in that: The method comprises: Step (1) sample collection and selection; Step (2) optical thin-section preparation and microscopic observation; Step (3) determining and analyzing the main elements and trace elements in the optical slice to obtain chemical analysis data; Step (4) constructs a prediction model for uranium mineralization intensity based on chemical analysis data.

2. A method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 1, characterized in that: The step (1) specifically comprises: measuring the profile of a borehole or underground tunnel, dividing the alteration zones perpendicular to the strike direction of the ore body, and recording geological information data; marking sampling points on each alteration zone, and systematically collecting rock samples.

3. A method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 2, characterized in that: The geological information data include: sample collection location, surrounding rock lithology, alteration type, mineralization intensity and ore-bearing structure.

4. The method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 1, characterized in that: The step (2) specifically comprises: making the collected samples into optical thin slices for electron probe microanalysis to ensure that the samples are uniform; and using a mineralogy microscope to observe in detail the occurrence and morphology of chlorite in different alteration zones and mineralization zones.

5. The method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 1, characterized in that: The step (3) specifically comprises: using electron probe microanalysis to quantitatively analyze the main elements in the optical thin slice sample, and using laser ablation inductively coupled plasma mass spectrometry to quantitatively analyze the key trace elements in the optical thin slice sample to obtain chemical analysis data.

6. A method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 5, characterized in that: The main elements include Si, Al, Fe, Mg, the key trace elements include Ti, Mn, Cr, U, Th, and the chemical analysis data include Al IV value, Fe / (Fe+Mg) ratio and U and Th contents.

7. The method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 1, characterized in that: The step (4) is specifically as follows: using the obtained chemical analysis data, comparing the chemical composition differences of chlorite in the known uranium mineralized zone and non-mineralized zone, and determining the key indicators related to mineralization. By comparing the chemical analysis data, the indicator characteristics of the mineralization intensity are identified, a geochemical model is established, the critical value for identifying the uranium mineralization potential zone is determined, and a prediction model for the uranium mineralization intensity is constructed.

8. A method for indicating hydrothermal uranium mineralization based on chlorite chemical composition analysis according to claim 7, characterized in that: In the step (4), by comparing the Al IV value, Fe / (Fe+Mg) ratio and U and Th content, identify the indicator characteristics of mineralization intensity, establish a geochemical model, and determine the high Al IV The critical value of the content and high Fe / (Fe+Mg) ratio is used to identify the potential areas of uranium mineralization; and a prediction model for the uranium mineralization intensity is constructed based on the distribution of U and Th contents in chlorite.

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