A method for delineating deep volcanic channels of volcanic rock-type uranium deposits

Abstract

The present invention relates to a method for delineating deep volcanic channels in volcanic rock-type uranium deposits. First, borehole rock physical property measurements are carried out in the study area to determine the density and resistivity characteristics of volcanic rocks. Then, gravity measurements are implemented in the working area to obtain the Bouguer gravity anomaly in the working area. Next, three-dimensional density inversion is performed to determine the density characteristics and spatial distribution pattern of the volcanic channels. Then, broadband magnetotelluric profile measurements are carried out to obtain the deep resistivity characteristics, and then the resistivity characteristics and spatial distribution pattern of the volcanic channels are delineated. Finally, the range of the deep volcanic channels is delineated using the density characteristics and spatial distribution pattern as well as the resistivity characteristics and spatial distribution pattern. The present invention realizes the rapid delineation of deep volcanic channels through physical property test statistics and two geophysical joint exploration methods of high-precision gravity and broadband magnetotelluric, can provide important information for the exploration of volcanic rock-type uranium deposits, especially deep prospecting, reduce unnecessary geological and drilling work, and shorten the prospecting cycle.

Description

Technical Field

[0001] The invention relates to the field of volcanic rock type uranium ore exploration and deep geophysical detection, and in particular to a method for delineating deep volcanic channels in volcanic rock type uranium deposits. Background Art

[0002] With the rapid development of my country's nuclear power industry, the demand for uranium resources will increase in the future. Volcanic uranium deposits have been one of the main types of mineral exploration in my country for many years. In decades of exploration, many deposits have been found and developed. It has been found that known deposits and mineral points are closely related to deep thermal activities, especially in the volcanic channels and structural fissures of volcanic rocks, which are more prone to mineralization.

[0003] Due to the Quaternary cover on the surface, it is difficult to find volcanic structures through surface geological observations, and it is even more difficult to determine the direction, shape and scale of deep volcanic channels. This makes the current exploration of deep hydrothermal uranium deposits lack direction. Therefore, correctly and effectively delineating the spatial distribution of volcanic channels is the key to finding deep volcanic rock-type uranium deposits. Based on this, a method for delineating deep volcanic channels in volcanic rock-type uranium deposits is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for delineating deep volcanic channels in volcanic rock type uranium deposits, so as to provide a basis for identifying the location of deep volcanic channels and narrowing down the prospecting target area.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for delineating a deep volcanic channel in a volcanic rock type uranium deposit, the method comprising:

[0007] Select boreholes in the study area, and select different types of volcanic rock samples from the boreholes to perform density and resistivity measurements, so as to obtain density variation range data and resistivity variation range data of different types of volcanic rocks;

[0008] Selecting a plurality of first survey lines in the study area, and selecting a plurality of first survey points on each of the first survey lines, obtaining coordinates and gravity altitudes of the plurality of first survey points, and using a gravimeter to perform gravity measurements on the plurality of first survey points respectively, to obtain gravity values of the plurality of first survey points;

[0009] Calculating Bouguer gravity anomaly values of a plurality of the first measuring points using the gravity values of a plurality of the first measuring points and the coordinates and gravity altitudes of a plurality of the first measuring points;

[0010] Based on the Bouguer gravity anomaly values of multiple said first measuring points, the elevation of multiple said first measuring points, and the density change range data of different types of said volcanic rocks, three-dimensional density inversion is carried out using three-dimensional density inversion software to obtain the density model of the research area;

[0011] According to the density model and the density change range data of different types of said volcanic rocks, determine the spatial distribution pattern of the density of the volcanic conduit, denoted as the density spatial distribution pattern;

[0012] Select multiple second survey lines in the research area, select multiple second measuring points on each said second survey line, and use broadband magnetotelluric equipment to conduct observations at multiple said second measuring points respectively to obtain the measuring point data of multiple said second measuring points;

[0013] For each said second survey line, import the multiple said second measuring point data on the second survey line into the electrical method inversion software for inversion calculation to obtain the resistivity inversion data of the corresponding profile of the second survey line, denoted as the resistivity inversion data of the profile, and use the resistivity inversion data of the profile to obtain the inversion resistivity contour map;

[0014] Use multiple said inversion resistivity contour maps and the resistivity change range data of different types of said volcanic rocks to obtain the spatial distribution pattern of the resistivity of the volcanic conduit, denoted as the resistivity spatial distribution pattern;

[0015] Perform an intersection operation on the density spatial distribution pattern and the resistivity spatial distribution pattern to obtain the range of the volcanic conduit in the research area.

[0016] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0017] The present invention provides a method for delineating the deep volcanic conduit of a volcanic rock type uranium deposit. First, carry out borehole rock physical property measurement work in the research area to determine the density and resistivity characteristics of volcanic rocks; then conduct gravity measurement in the work area to obtain the Bouguer gravity anomaly in the work area; then through three-dimensional density inversion, determine the density characteristics and spatial distribution pattern of the volcanic conduit; then carry out broadband magnetotelluric profile measurement to obtain the deep resistivity characteristics, and then delineate the resistivity characteristics and spatial distribution pattern of the volcanic conduit; finally, use the density characteristics and spatial distribution pattern and the resistivity characteristics and spatial distribution pattern to delineate the range of the deep volcanic conduit. The present invention realizes the rapid delineation of the deep volcanic conduit through physical property test statistics and two geophysical joint exploration methods of high-precision gravity and broadband magnetotelluric, can provide important information for the exploration of volcanic rock type uranium deposits, especially deep prospecting, reduce unnecessary geological and drilling work, and shorten the prospecting cycle. Description of the Drawings

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A flow chart of a method for delineating deep volcanic channels in a volcanic rock-type uranium deposit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The purpose of the present invention is to provide a method for delineating deep volcanic channels in volcanic rock type uranium deposits, thereby effectively delineating the spatial morphology of the deep volcanic channels and reducing the prospecting target area.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] This embodiment provides a method for delineating deep volcanic channels in volcanic rock-type uranium deposits. Figure 1 , the method comprising:

[0025] S1. Select boreholes in the study area, and select different types of volcanic rock samples from the boreholes to perform density and resistivity measurements, so as to obtain density variation range data and resistivity variation range data of different types of volcanic rocks.

[0026] Specifically, the selected borehole should be located within the working area, and the depth of the borehole needs to pass through the volcanic rock cap layer to expose all volcanic rocks. Use a balance and a measuring cup to measure the density of rock specimens of different lithologies, and use a SCIP rock electrical property measuring instrument to measure the resistivity. The number of samples for each lithology should be no less than 30. The density and resistivity variation ranges of each lithology are statistically obtained in turn.

[0027] S2. Select multiple first survey lines in the study area, and select multiple first measurement points on each of the first survey lines. Obtain the coordinates and gravity elevation of the multiple first measurement points, and use a gravimeter to conduct gravity measurements on the multiple first measurement points respectively to obtain the gravity values of the multiple first measurement points. Calculate the Bouguer gravity anomaly values of the multiple first measurement points using the gravity values of the multiple first measurement points and the coordinates and gravity elevation of the multiple first measurement points.

[0028] Among them, any two of the first survey lines are parallel, the vertical distance between adjacent two of the first survey lines is less than or equal to 100 meters, the distance between any two of the first measurement points on the same first survey line is less than or equal to 100 meters, and the measurement area covers the outcropping area of volcanic rocks.

[0029] In this embodiment, a CG-5 gravimeter can be used, with a resolution of 0.001×10 -5 m / s 2 , a repeatability accuracy of 0.005 ×10 - 5 m / s 2 , and a mean square error of gravity measurement points of 0.80×10 -5 m / s 2 .

[0030] Specifically, the Bouguer gravity anomaly can be calculated using the following formula.

[0031]

[0032]

[0033] Δg B = g - γ0 + δ b +δ 地

[0034] Among them, represents the latitude value of the gravity point; h is the gravity elevation; ρ is the density of the intermediate layer; δ 地 is the topographic correction value; R is the topographic correction radius; g is the gravity value; Δg B represents the Bouguer gravity anomaly value; δ b represents the Bouguer correction value, and γ0 is the normal gravity field value.

[0035] S3. According to the Bouguer gravity anomaly values of the multiple first measurement points, the elevation of the multiple first measurement points, and the density change range data of different types of volcanic rocks, use three-dimensional density inversion software to perform three-dimensional density inversion to obtain the density model of the study area. Determine the spatial distribution pattern of the density of the volcanic conduit according to the density model and the density change range data of different types of volcanic rocks, denoted as the density spatial distribution pattern.

[0036] Step S3 specifically includes:

[0037] S31. Use gravity and magnetic processing software to grid the Bouguer gravity anomaly values of multiple said first measurement points to obtain gridded data;

[0038] In this embodiment, EncomPA processing software can be used to grid the Bouguer gravity anomaly Δg B to obtain gridded data. It should be noted that those skilled in the art can also choose other middle-word processing software to process the Bouguer gravity anomaly, and this application does not make specific limitations on this.

[0039] Considering the influence of near-source noise, this embodiment also needs to perform low-pass filtering on the gridded data to weaken the influence of near-source noise.

[0040] S32. Use the gravity and magnetic processing software to grid the elevation of multiple said first measurement points to form a topographic data file;

[0041] The gravity and magnetic processing software here can also select Encom PA processing software, and the number of grid nodes is the same as that in step S31.

[0042] S33. Establish an initial grid model in 3D inversion software, add the density change range data of different types of said volcanic rocks to the initial grid model, and input the gridded data and the topographic data file into the 3D inversion software. Perform 3D inversion in the 3D inversion software according to the preset 3D inversion stop condition to obtain the density model of the study area; the initial grid model is a model that only contains empty grids.

[0043] The 3D inversion software here can select UBC software for 3D density inversion. The density parameters of the surface lithology in the initial model use the measurement results in step S1, and the data file and topographic file respectively use the results obtained in steps S31 and S32. The set 3D inversion stop condition is: stop the inversion calculation when the fitting difference is less than 0.5 mgal or when convergence cannot be achieved, and obtain the density model of the study area.

[0044] S34. Obtain general density change range data according to the density change range data of different types of said volcanic rocks, and the general density change range is the density change range applicable to all types of said volcanic rocks.

[0045] S35. Select the area corresponding to the volcanic rocks with density greater than X min less than X max in the density model as the spatial distribution form of the density of the volcanic conduit; where X min is the minimum value of the general density change range data, and X maxis the maximum value of the general density change range data.

[0046] It should also be noted that in addition to the selected area satisfying a density greater than X min less than X max it also needs to satisfy an area in a continuous form.

[0047] Among them, the calculation formulas for the minimum value and the maximum value of the general density change range data are respectively:

[0048]

[0049]

[0050]

[0051] Among them, represents the average density of the I-th type of volcanic rock; I represents volcanic rocks of different lithologies; n represents the number of samples collected for the I-th type of volcanic rock; is the average density of all volcanic rock samples.

[0052] S4. Select multiple second survey lines in the study area, select multiple second measurement points on each of the second survey lines, and use broadband magnetotelluric equipment to observe at multiple second measurement points respectively to obtain measurement point data of multiple second measurement points; for each second survey line, import the multiple second measurement point data on the second survey line into an electrical method inversion software for inversion calculation to obtain resistivity inversion data of the corresponding profile of the second survey line, denoted as resistivity inversion data of the profile, and use the resistivity inversion data of the profile to obtain an inversion resistivity contour map.

[0053] Here, the selection methods of the second survey line and the second measurement point are the same as those of the first survey line and the first measurement point in step S2.

[0054] At the same time, it is required that the broadband magnetotelluric simultaneously collects three magnetic field components and two electric field components, the observation time is 36 hours, and the measurement frequency range is 360 - 0.0005 HZ.

[0055] The electrical method inversion software selected in this embodiment can be MTPioneer inversion software. The inversion selects TM mode polarization data, the data threshold error is 2%, the smoothing coefficient is selected as 10, and two-dimensional conjugate gradient inversion calculation is selected to sequentially obtain the resistivity inversion data of the corresponding profile of the second survey line. Loading the resistivity inversion results of each profile with Surfer software obtains multiple broadband magnetotelluric inversion resistivity contour maps.

[0056] S5. Use the multiple inversion resistivity contour maps and the resistivity change range data of different types of the volcanic rocks to obtain the spatial distribution pattern of the resistivity of the volcanic conduit, denoted as the resistivity spatial distribution pattern.

[0057] Specifically, first obtain the general resistivity change range data according to the resistivity change range data of different types of the volcanic rocks. The general resistivity change range is the resistivity change range applicable to all types of the volcanic rocks.

[0058] Then, for each of the multiple inversion resistivity contour maps, delineate the range where the resistivity is greater than Y min and less than Y max to obtain multiple delineated ranges; Y min is the minimum value of the general density change range data, and Y max is the maximum value of the general density change range data.

[0059] The calculation formulas for the minimum value and the maximum value of the general density change range data are respectively:

[0060]

[0061]

[0062]

[0063] where represents the average resistivity of the I-th type of volcanic rock; is the average resistivity of all volcanic rock samples; σ is the sample standard error; N is the total number of all volcanic rock samples; is the lateral distribution point of the standard normal distribution.

[0064] Finally, interpolate the multiple delineated ranges into a three-dimensional body to obtain the spatial distribution pattern of the resistivity of the volcanic conduit.

[0065] S6. Perform an intersection operation on the density spatial distribution pattern and the resistivity spatial distribution pattern to obtain the range of the volcanic conduit in the study area.

[0066] Through physical property testing statistics and two geophysical joint exploration methods of high-precision gravity and broadband magnetotellurics, the present invention can quickly delineate the deep volcanic conduit, and can provide important information for the exploration of volcanic rock type uranium deposits, especially deep prospecting, reduce unnecessary geological and drilling work, and shorten the prospecting cycle.

[0067] In this article, specific examples are used to illustrate the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation modes and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A method for delineating a deep volcanic channel of a volcanic rock type uranium deposit, characterized in that The method includes: Select boreholes in the study area, and select specimens of different types of volcanic rocks from the boreholes respectively for density and resistivity measurement to obtain data on the density change range and resistivity change range of different types of volcanic rocks; Select multiple first survey lines in the study area, and select multiple first survey points on each of the first survey lines to obtain the coordinates and gravity elevation of the multiple first survey points, and use a gravimeter to perform gravity measurement on the multiple first survey points respectively to obtain the gravity values of the multiple first survey points; Calculate the Bouguer gravity anomaly values of the multiple first survey points using the gravity values of the multiple first survey points, the coordinates of the multiple first survey points, and the gravity elevation; According to the Bouguer gravity anomaly values of the multiple first survey points, the elevation of the multiple first survey points, and the density change range data of different types of the volcanic rocks, use three-dimensional density inversion software to perform three-dimensional density inversion to obtain the density model of the study area; The step of using three-dimensional density inversion software to perform three-dimensional density inversion according to the Bouguer gravity anomaly values of the multiple first survey points, the elevation of the multiple first survey points, and the density change range data of different types of the volcanic rocks to obtain the density model of the study area specifically includes: Use gravity and magnetic processing software to grid the Bouguer gravity anomaly values of the multiple first survey points to obtain gridded data; Use the gravity and magnetic processing software to grid the elevation of the multiple first survey points to form a topographic data file; Establish an initial grid model in the three-dimensional inversion software, add the density change range data of different types of the volcanic rocks to the initial grid model, and input the gridded data and the topographic data file into the three-dimensional inversion software, and perform three-dimensional inversion in the three-dimensional inversion software according to the preset three-dimensional inversion stop condition to obtain the density model of the study area; the initial grid model is a model that only contains empty grids; Determine the spatial distribution pattern of the density of the volcanic conduit according to the density model and the density change range data of different types of the volcanic rocks, denoted as the density spatial distribution pattern; Select multiple second survey lines in the study area, select multiple second survey points on each of the second survey lines, and use broadband magnetotelluric equipment to perform observations on the multiple second survey points respectively to obtain the survey point data of the multiple second survey points; For each of the second survey lines, import the multiple second survey point data on the second survey line into the electrical method inversion software for inversion calculation, and use the TM-mode polarization data and the conjugate gradient inversion algorithm to obtain the resistivity inversion data of the profile corresponding to the second survey line, denoted as the resistivity inversion data of the profile, and use the resistivity inversion data of the profile to obtain an inverted resistivity contour map; Obtain the spatial distribution pattern of the resistivity of the volcanic conduit, denoted as the resistivity spatial distribution pattern, using the multiple inverted resistivity contour maps and the resistivity change range data of different types of the volcanic rocks; Perform an intersection operation on the density spatial distribution pattern and the resistivity spatial distribution pattern to obtain the range of the volcanic conduit in the study area.

2. The method according to claim 1, characterized in that, The formula for calculating the Bouguer gravity anomaly value is: Among them, represents the latitude value of the gravity point; h is the gravity elevation; ρ is the density of the intermediate layer; δ 地 is the topographic correction value; R is the topographic correction radius; g is the gravity value; Δg B represents the Bouguer gravity anomaly value; δ b represents the Bouguer correction value, and γ0 is the value of the normal gravity field.

3. The method according to claim 1, characterized in that, Determining the spatial distribution pattern of the density of the volcanic conduit according to the density model and the density change range data of different types of the volcanic rocks specifically includes: Obtaining general density change range data based on the density change range data of different types of the volcanic rocks, where the general density change range is the density change range applicable to all types of the volcanic rocks; Select the regions corresponding to the volcanic rocks with densities greater than X min less than X max to obtain the spatial distribution pattern of the density of the volcanic conduit; where X min is the minimum value of the general density change range data, and X max is the maximum value of the general density change range data.

4. The method according to claim 3, characterized in that, The calculation formulas for the minimum value and the maximum value of the general density change range data are respectively: Among them, represents the average density of the I-th type of volcanic rock; I represents volcanic rocks of different lithologies; n represents the number of samples collected for the I-th type of volcanic rock; is the average density of all volcanic rock samples; σ is the sample standard error; is the side distribution point of the standard normal distribution; N is the total number of all volcanic rock samples.

5. The method according to claim 1, characterized in that The observation time for using the broadband magnetotelluric equipment to conduct observations at multiple second measuring points is greater than 30 hours, and the measurement frequency range is 360 - 0.0005 HZ.

6. The method according to claim 1, wherein Determining the spatial distribution pattern of the resistivity of the volcanic conduit by using multiple inversion resistivity contour maps and the resistivity change range data of different types of the volcanic rocks specifically includes: Obtaining general resistivity change range data based on the resistivity change range data of different types of the volcanic rocks, where the general resistivity change range is the resistivity change range applicable to all types of the volcanic rocks; For each of the multiple inverted resistivity contour maps, those with resistivity greater than Y min less than Y max are delineated to obtain multiple delineated ranges; Y min is the minimum value of the general density change range data, and Y max is the maximum value of the general density change range data; Interpolating multiple delineated ranges into a three-dimensional body to obtain the spatial distribution pattern of the resistivity of the volcanic conduit.

7. The method according to claim 6, wherein The calculation formulas for the minimum value and the maximum value of the general density change range data are respectively: Among them, represents the average resistivity of the I-th type of volcanic rock; is the average resistivity of all volcanic rock samples; σ is the sample standard error; N is the total number of all volcanic rock samples; is the side distribution point of the standard normal distribution; Y n is the resistivity of all volcanic rock samples; n represents the number of samples collected for the I-th type of volcanic rock.

8. The method according to claim 1, characterized in that The resolution of the gravimeter is higher than 0.001×10 -5 m / s 2 , and the repeatability accuracy is higher than 0.005×10 -5 m / s 2 .

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