A Magnetic Anomaly Modeling Method for Intersection-Type Uranium Deposits

Abstract

This invention relates to the field of magnetic anomaly analysis of uranium deposits, specifically a method for modeling magnetic anomalies in intersection-type uranium deposits. The method includes the following steps: S1, measuring the magnetic characteristic parameters of rock cores using magnetic measurement equipment; S2, calculating a single finite-length inclined thin-plate magnetic anomaly model and calculating the overall magnetic anomaly. This invention rationally constructs magnetic anomalies in intersection-type uranium deposits from hydrothermal uranium veins, forming various modeling structures such as deep and frontal sections, rich and poor ore, based on the obtained surface magnetic anomaly characteristics of different types of ore bodies. This can assist ground magnetic surveys in more accurately delineating the structural zones of uranium deposits, and, combined with magnetic survey results and forward modeling, more accurately determining the rich ore zones in real areas.

Description

Technical Field

[0001] This invention relates to the field of magnetic anomaly analysis technology for uranium deposits, and more particularly to a magnetic anomaly modeling method for intersection-type uranium deposits. Background Technology

[0002] In the Xiazhuang uranium field in South China, five groups of northwest-trending intermediate-basic veins are distributed at equal intervals from north to south, filling the northwest-northeast and northeast-east trending fault zones. The ore bodies are filled in the basic veins and silicified breccia zones of granite affected by hydrothermal alteration, forming a "crossroads" type uranium deposit. The magnetic anomaly interpretation of the vein-like uranium deposit is strongly influenced by magmatic metamorphism.

[0003] Currently, the well-established forward modeling techniques for magnetic anomalies in rock masses with typical tectonic indices generally still require input of parameters such as magnetic declination, magnetic dip, and magnetic susceptibility to perform normal magnetic anomaly calculations. New models require input of magnetic parameters from various rock samples, including diabase or gabbro dikes, silicified fault zones, and uranium deposits, encompassing magnetic declination, magnetic dip, and magnetic susceptibility, or remanent magnetization and magnetic susceptibility. Therefore, extensive deep core data measurements are necessary to accurately construct the magnetic anomaly characteristics of uranium deposits.

[0004] Because geophysical interpretations are highly ambiguous, when considering complex geological conditions such as the irregularity of slab formations, the magnetic heterogeneity of dikes, and the complex structure of silicified fault zones and uranium veins, simulation results can better constrain the measured results, greatly reduce geophysical ambiguity, and provide reasonable geological interpretations, but cannot achieve complete data matching. Summary of the Invention

[0005] The purpose of this invention is to address the problem of the lack of suitable models for analyzing the magnetic anomalies of intersection-type uranium deposits in the background art, and to propose a magnetic anomaly modeling method for intersection-type uranium deposits.

[0006] The technical solution of this invention: A method for modeling magnetic anomalies in intersection-type uranium deposits, comprising the following steps:

[0007] S1. Utilize magnetic measurement equipment to measure the magnetic characteristic parameters of rock cores;

[0008] S2. Calculate the magnetic anomaly model of a single finite-length inclined thin plate and calculate the overall magnetic anomaly.

[0009] Preferably, it also includes S3, which constructs a combination of various inclined structural models based on the actual situation of intersection-type uranium deposits.

[0010] Preferably, it also includes S4, which forms different types of intersection-type uranium deposit mineralization models based on the above-constructed models, compares them well with ground magnetic anomalies, analyzes the demagnetization characteristics of diabase magnetic anomaly zones, and further identifies intersection-type uranium deposit zones.

[0011] Preferably, in S1, the parameters include the volume magnetic susceptibility κ of the rock sample, the magnetic anisotropy parameters, namely the magnetic anisotropy characteristic values ​​K1, K2 and K3, the mass magnetic susceptibility χ, and the remanent magnetization of the standard sample, and their corresponding magnetic declination and magnetic inclination parameters.

[0012] Preferably, the rock samples include four main categories: host rock granite, diabase, altered diabase, and ore-bearing rocks; the volumetric magnetic susceptibility κ was measured using an SM30 magnetic susceptibility meter, the magnetic anisotropy parameters were measured using a Bartington MS2 multi-functional magnetic susceptibility meter, and the remanent magnetization of the standard samples and their corresponding magnetic declination and magnetic inclination parameters were measured using a Minispin magnetometer.

[0013] Preferably, the local geomagnetic field strength is calculated using the International Geomagnetic Reference Field Model based on the sampling points. The magnitude of the induced magnetization is obtained based on the product of magnetic susceptibility. The vector sum of the induced magnetization and the remanent magnetization is then calculated to obtain the magnitude M of the total magnetization and the magnetization inclination i of the four major rock types. s .

[0014] Preferably, in S2, the parameters in the single finite-length inclined thin-plate magnetic anomaly model are described as follows: h is the depth of the top of the thin plate from the ground, 2L is the length of the thin plate, 2l is the depth of the thin plate, 2b is the thickness of the thin plate, the magnetization intensity of the thin plate is M, and the magnetization tilt angle is i. s The thin plate is tilted at an angle of β; the calculation of the overall magnetic anomaly includes the following steps:

[0015] S21. Calculate the vertical magnetic anomaly component Za based on the magnetized parallelepiped. The specific formula is as follows:

[0016]

[0017] S22. Through Fourier transform, Z a Transform into S z :

[0018]

[0019] S23, Calculate T i The Fourier transform, also known as S T :

[0020]

[0021] in,

[0022]

[0023] Where L0, M0, and N0 are the direction cosines of the magnetization M.

[0024] Finally, the overall magnetic anomaly T is calculated using inverse Fourier transform:

[0025]

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] 1. By constructing a three-dimensional magnetic anomaly model for intersection-type uranium deposits of hydrothermal origin, the challenges of complex extraction of magnetic features of various lithologies, indistinct magnetic features of rich and poor ore zones, and different mineralization depths were overcome. The model was developed to construct magnetic anomaly features of intersection-type uranium deposits from magnetic exploration. Ultimately, it is possible to model magnetic anomalies under different conditions and perform comprehensive magnetic anomaly calculations and mapping.

[0028] 2. The constructed model breaks away from conventional magnetic exploration methods that model general single rock bodies. Instead, it specifically models the magnetic anomalies of intersection-type uranium deposits in vein-type uranium deposits in South China. It can model intersection-type uranium deposits at different depths and with varying mineralization levels, and calculate the magnetic anomaly state, thus more realistically reflecting the surface magnetic anomaly characteristics of intersection-type uranium deposits. Combined with measured surface magnetic anomalies, it can more clearly analyze the mineralization location of uranium deposits, which has practical significance for deep uranium exploration in South China. Attached Figure Description

[0029] Figure 1 A schematic diagram of a finite-length plate-like structure;

[0030] Figure 2 A magnetic anomaly structure diagram showing the 10m silicified fault zone cutting through 100m into a diabase dike;

[0031] Figure 3 A magnetic anomaly structure diagram showing the complete cutting through of the diabase dike (10m) by a silicified fault zone (4m);

[0032] Figure 4 A magnetic anomaly structure diagram of an irregular diabase dike combined with a silicified fault zone;

[0033] Figure 5 A schematic diagram illustrating the influence of residual magnetization on the integrated magnetic anomaly modeling type, combined with measured magnetic parameters. Detailed Implementation

[0034] Example 1, as Figure 1 As shown, the present invention proposes a magnetic anomaly modeling method for intersection-type uranium deposits, comprising the following steps:

[0035] S1. Utilize magnetic measurement equipment to measure the magnetic characteristic parameters of rock cores;

[0036] S2. Calculate the magnetic anomaly model of a single finite-length inclined thin plate and the overall magnetic anomaly. The magnetic anomaly model of the inclined thin plate is as follows: Figure 1 As shown.

[0037] Example 2: The magnetic anomaly modeling method for intersection-type uranium deposits proposed in this invention adds S3 and S4 compared to Example 1.

[0038] S3. Based on the actual situation of intersection-type uranium deposits, various combinations of inclined structural models are constructed, including (i) pure diabase dike model (poor ore); (ii) diabase dike shallowly cut through silicified fault zone model (poor ore); (iii) diabase dike fully cut through silicified fault zone model (poor ore); (iv) irregular diabase dike intersecting with silicified zone model (poor ore); (v) shallow mineralization model of diabase dike fault zone (rich ore); (vi) deep mineralization model of diabase dike fault zone (rich ore), etc.

[0039] S4. Based on the above model, different types of intersection-type uranium deposit mineralization models are formed, and a good comparison is made with ground magnetic anomalies. The demagnetization characteristics of diabase magnetic anomaly zones are analyzed, and intersection-type uranium deposit zones are further identified.

[0040] Example 3, as Figure 2 As shown, the present invention proposes a magnetic anomaly modeling method for intersection-type uranium deposits. Compared with Embodiment 1, this embodiment details S1.

[0041] In S1, the parameters include the volumetric magnetic susceptibility κ of the rock samples, magnetic anisotropy parameters (i.e., magnetic anisotropy characteristic values ​​K1, K2, and K3), mass magnetic susceptibility χ, and the remanent magnetization of the standard samples, along with their corresponding magnetic declination and magnetic inclination. The rock samples include four main categories: host granite, diabase, altered diabase, and ore-bearing rocks. The volumetric magnetic susceptibility κ was measured using an SM30 magnetic susceptibility meter, the magnetic anisotropy parameters were measured using a Bartington MS2 multi-functional magnetic susceptibility meter, and the remanent magnetization of the standard samples, along with their corresponding magnetic declination and magnetic inclination, were measured using a Minispin magnetometer. Based on the sampling points, the local geomagnetic field strength was calculated using the International Geomagnetic Reference Field Model. The magnitude of the induced magnetization was obtained based on the product of magnetic susceptibility values. Furthermore, the vector sum of the induced and remanent magnetization was calculated to obtain the total magnetization M and magnetization inclination i of the four rock categories. s .

[0042] Example 4 presents a magnetic anomaly modeling method for intersection-type uranium deposits proposed in this invention. Compared with Example 3, this example details S2.

[0043] In S2, the parameters in the single finite-length inclined thin-plate magnetic anomaly model are described as follows: h is the depth of the top of the thin plate from the ground, 2L is the length of the thin plate, 2l is the depth of the thin plate, 2b is the thickness of the thin plate, the magnetization intensity of the thin plate is M, and the magnetization tilt angle is i. s The thin plate is tilted at an angle of β; the calculation of the overall magnetic anomaly includes the following steps:

[0044] S21. Calculate the vertical magnetic anomaly component Za based on the magnetized parallelepiped. The specific formula is as follows:

[0045]

[0046] S22. Through Fourier transform, Z a Transform into S z :

[0047]

[0048] S23, Calculate T i The Fourier transform, also known as S T :

[0049]

[0050] in,

[0051]

[0052] Where L0, M0, and N0 are the direction cosines of the magnetization M.

[0053] Finally, the overall magnetic anomaly T is calculated using inverse Fourier transform:

[0054]

[0055] After using this invention:

[0056] Figure 2 This image shows the magnetic anomaly results of a silicified fault zone longitudinally cutting through a diabase dike trending NW-SE, with a depth of 100 meters from the surface. The strike of the diabase dike is clearly identifiable. Furthermore, there is a significant low magnetic anomaly at the point of cut by the silicified fault zone, indicating demagnetization of a junction-type uranium vein. Notably, although the silicified fault zone cuts through to a depth of 100 meters, the characteristics of the deep diabase dike can still be identified through the high-low-high magnetic anomaly trend.

[0057] Figure 3This paper presents the magnetic anomaly results of a 100m deep hydrothermal uranium vein that longitudinally cuts through a silicified fault zone in the middle of a NW-SE-EST trending diabase dike. The results show that the strike of the diabase dike is clearly identifiable, but significant demagnetization is observed at the cut location of the silicified fault zone. Because the magnetic parameters of the uranium vein are relatively close to those of the silicified zone, no high-low-high demagnetization enhancement phenomenon is observed. However, when uranium deposits occur on the surface of fault zones or as outcrops, the magnitude of this demagnetization will be significantly reduced.

[0058] Figure 4 This study demonstrates the combined forms of irregular diabase bodies and silicified fault zones constructed using this method, and these combined forms are similar to... Figure 2 Similarly, this forms a magnetic anomaly structure that approximates actual geological conditions. From Figure 4 It can be seen that, despite the influence of the irregular shape of the diabase dike, the deep structure of the diabase dike and the silicified fault zone can still be judged from the changing trend of the demagnetization area for the intersection-type deposit structure.

[0059] Therefore, further combining it with ground magnetic surveys, based on ground magnetic anomaly maps, to analyze the magnetic anomaly characteristics of the diabase tectonic region, and to analyze the special magnetic anomaly characteristics of the diabase demagnetization region, in close combination with the method of this invention, can help to effectively delineate the rich ore areas of intersection-type uranium deposits.

[0060] Specific application example: Diabase dikes of a certain width are widely distributed in South China, exhibiting a near-east-west trend, primarily in a northwest-southeast direction, with silicified fault zones distributed nearly perpendicularly to the dikes. Uranium veins mostly occur at a certain depth at the intersection of the diabase dike and the silicified fault zone. Here, it is assumed that the diabase dike has an apparent thickness of 10m and a dip angle of 60°; the silicified fault zone vertically cuts through the diabase dike, with a width of 4-10m; two states of uranium veins are set: one is an outcrop deposit, and the other is a deposit at a depth of 100m. The magnetic parameters of all rock masses are given by local core measurements. Subsequently, several intersection deposit types, including rich ore, poor ore, outcrop ore, and deep mineralization, are constructed, and the magnetic anomaly results of the intersection type uranium deposit are calculated based on the model parameters.

[0061] Other applications:

[0062] The data processing algorithm of this invention is not limited to anomaly modeling for deep exploration of intersection-type uranium veins. Under certain circumstances, it can be used to model other types of uranium ore belts in South China. For example, silicified zone uranium deposits are a typical type of uranium mineralization in the Xiaozhuang area of ​​South China. In silicified zone mineralization in granite areas, uranium enrichment occurs between the silicified zone and the granite host rock. This hydrothermal reduction mineralization is also reflected in the iron oxide transformation. The reduced magnetite is also reflected in the magnetic anomalies. This can be achieved by measuring the magnetic parameters of the veins and then performing modeling and analysis based on the silicified zone model provided by this invention.

[0063] Based on this, the data processing algorithm of this invention is not limited to anomaly modeling for deep uranium deposit exploration. Under certain circumstances, it can also be used to model magnetic anomalies in other non-ferrous metal minerals and their associated fault zones or tectonic zones and other types of rock masses. Figure 5 Generally, non-ferrous metal mineral deposits are located in fault zones or tectonic zones, which can be modeled using a slab cutting through the surrounding rock. This is based on high-precision magnetic parameters obtained from the rock magnetic results of the ore-bearing samples and the surrounding rock. By using the deep or forward-facing, rich or poor ore structural models provided by this invention, their surface magnetic characteristics can be analyzed using forward modeling. Based on the measured magnetic survey results, potentially rich ore areas can be effectively identified.

[0064] In summary, this invention overcomes the challenges of complex extraction of magnetic features from various lithologies, indistinct magnetic features in rich and poor ore zones, and varying mineralization depths by constructing a three-dimensional magnetic anomaly model for intersection-type uranium deposits formed by hydrothermal veins. It achieves the construction of magnetic anomaly features for intersection-type uranium deposits from magnetic exploration, ultimately enabling the modeling of magnetic anomalies under different conditions and the comprehensive calculation and mapping of magnetic anomalies. The constructed model breaks away from conventional magnetic exploration methods that model general single rock bodies, instead focusing on the targeted magnetic anomaly modeling of intersection-type uranium deposits in vein-type uranium deposits in South China. It can model intersection-type uranium deposits at different depths and with varying mineralization levels, and calculate the magnetic anomaly state, more realistically reflecting the surface magnetic anomaly characteristics of intersection-type uranium deposits. Combined with measured surface magnetic anomalies, it can more clearly analyze the mineralization location of uranium deposits, possessing practical significance for deep uranium exploration in South China.

[0065] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. 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.

Claims

1. A method for modeling magnetic anomalies in intersection-type uranium deposits, characterized in that, Includes the following steps: S1. Magnetic core magnetic characteristic parameters were measured using magnetic measurement equipment. These parameters included the volumetric magnetic susceptibility κ, magnetic anisotropy parameters (i.e., magnetic anisotropy characteristic values ​​K1, K2, and K3), mass magnetic susceptibility χ, and the remanent magnetization of the standard sample, along with their corresponding magnetic declination and inclination parameters. The rock samples included four main categories: host granite, diabase, altered diabase, and ore-bearing rocks. The volumetric magnetic susceptibility κ was measured using an SM30 magnetic susceptibility meter, the magnetic anisotropy parameters were measured using a Bartington MS2 multi-functional magnetic susceptibility meter, and the remanent magnetization of the standard sample, along with its corresponding magnetic declination and inclination parameters, were measured using a Minispin magnetometer. Based on the sampling points, the local geomagnetic field strength was calculated using the International Geomagnetic Reference Field Model. The magnitude of the induced magnetization was obtained based on the product of magnetic susceptibility values. Furthermore, the vector sum of the induced magnetization and the remanent magnetization was calculated to obtain the total magnetization M and magnetization inclination i of the four rock categories. s ; S2. Calculate the magnetic anomaly model of a single finite-length inclined thin plate and calculate the overall magnetic anomaly. The parameters in the single finite-length inclined thin plate magnetic anomaly model are explained as follows: h is the depth of the top of the thin plate from the ground, 2L is the length of the thin plate, 2l is the depth of the thin plate, 2b is the thickness of the thin plate, the magnetization intensity of the thin plate is M, and the magnetization tilt angle is i. s The thin plate is tilted at an angle of β; the calculation of the overall magnetic anomaly includes the following steps: S21. Calculate the vertical magnetic anomaly component Za based on the magnetized parallelepiped. , The specific formula is as follows: S22. Through Fourier transform, Z a Transform into S z : S23, Calculate T i The Fourier transform, also known as S T : in, Where L0, M0, and N0 are the direction cosines of the magnetization M. Finally, the overall magnetic anomaly T is calculated using inverse Fourier transform:

2. The magnetic anomaly modeling method for intersection-type uranium deposits according to claim 1, characterized in that, It also includes S3, which constructs a combination of various inclined structural models based on the actual conditions of intersection-type uranium deposits.

3. The magnetic anomaly modeling method for intersection-type uranium deposits according to claim 1, characterized in that, It also includes S4, which forms different types of intersection-type uranium deposit mineralization models based on the above-constructed models, compares them well with ground magnetic anomalies, analyzes the demagnetization characteristics of diabase magnetic anomaly zones, and further identifies intersection-type uranium deposit zones.

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