A method for inferring the depth of pegmatite rare metal deposits by using ground gas and X-ray fluorescence anomalies

Abstract

The present invention discloses a method for inferring the extension of pegmatite rare metal ore using ground gas and X-ray fluorescence anomaly, which can determine the extension depth of pegmatite vein and the extension length of the vein. The method includes the following steps: S1: Based on the method, the content of each element in the soil sample of the target area is measured to determine the abnormal area with working value; S2: For the working profile of the abnormal area, the ground gas method is measured to one side of the underground overturning direction to obtain the ground gas information above the deep vein on the overturning side of the pegmatite vein, and the abnormal position on the profile is divided; S3: It is determined whether the ground gas abnormal material comes from the deep pegmatite rare metal ore body, and if so, it enters S4; S4: Based on the previous geological and engineering data of the target area, the inclination of the pegmatite vein is determined, and a comprehensive profile including ground gas anomaly and X-ray fluorescence anomaly is compiled based on the topographic map of the target area; S5: Based on the obtained comprehensive profile, the extension length and burial depth of the pegmatite rare metal vein are inferred.

Description

Technical Field

[0001] The invention belongs to the technical field of pegmatite rare metal ore exploration, and in particular relates to a method for inferring whether a pegmatite is a mineralized body, and the extending depth and length of a ore-bearing pegmatite vein underground. Background Art

[0002] Generally speaking, when prospecting in a pegmatite rare metal ore exploration area, we will face a large number of pegmatite veins, but the proportion of pegmatite veins containing minerals is very small. The main task of prospecting is to determine which pegmatite veins are mineralized, as well as the extension length and burial depth of the mineralized body to the depth, and to judge whether the evaluated pegmatite vein has prospecting value. For concealed pegmatite veins, it is necessary to confirm the projection position of the top of the vein on the surface and the mineralization in the depth.

[0003] At present, the exploration technology of pegmatite rare metal mines is mainly traditional geochemical exploration. Although ordinary geophysical exploration has certain applications, the effect is mostly poor. Traditional geochemical exploration obtains the content of ore body elements and co-existing (associated) elements (these elements are called prospecting indicator elements) by chemical analysis after area or profile sampling, captures the indicator element anomalies formed by these elements on the surface, and guides prospecting. However, this method cannot determine the mineralization of pegmatite veins deep below the surface, and the cost is relatively high. Although ordinary geophysical exploration based on electricity, magnetism, gravity, and seismic can obtain physical property information such as electricity, magnetism, gravity, and seismic waves of deep geological bodies, these physical properties are indirect prospecting information and cannot make qualitative judgments on the mineralization of deep pegmatites. In addition, pegmatite veins are produced in granite, and the physical property parameters of pegmatite veins are slightly different from those of granite, resulting in ordinary geophysical exploration can only provide some auxiliary indirect prospecting information after high cost investment. In the field of pegmatite rare metal ore exploration, at present, only geogas measurement can directly obtain the content information of ore body elements of various pegmatite rare metal ores at a depth of about 50 to 1000m, and qualitatively determine the mineralization of deep pegmatite veins. However, geogas measurement is not sensitive to surface mineralization information, and it is difficult to accurately capture the mineralization anomalies formed on the surface of pegmatite rare metal ores through geogas measurement.

[0004] At present, commercial handheld X-ray fluorescence instruments based on Si-PIN or SDD detectors are widely used in the market. Such X-ray fluorescence instruments can complete soil X-ray fluorescence measurements similar to geochemical exploration in the field or at field stations, directly determine the ore body element content of pegmatite rare metal ores with higher atomic numbers such as Nb and Ta, and realize the capture of mineral anomalies. For pegmatite rare metal ores with lower atomic numbers such as Li and Be, although the ore body element content cannot be directly measured, the content of elements such as Nb, Ta, Rb, and Y belonging to the same rare metal cluster can be measured. These elements that have been confirmed to have a close symbiotic relationship with Li and Be in geological theory and practice are used as prospecting indicator elements to capture the anomalies formed by these elements in the soil, and combine the geogas content information of Li and Be from the deep part of the same pegmatite vein to see if there are any abnormal displays, and then reliably make a conclusion whether the captured X-ray fluorescence indicator element anomaly is a mineral anomaly.

[0005] Although the exploration of pegmatite rare metal deposits by geogas or X-ray fluorescence measurement alone has certain effects, they both have technical defects and cannot meet the requirements of pegmatite rare metal deposit exploration.

[0006] There are two problems in geogas surveying and exploring pegmatite rare metal ores:

[0007] 1) It is impossible to accurately obtain the geogas anomalies formed by surface mineralization. Because the migration power of geogas substances is the pressure difference and temperature difference inside the crust, the pressure difference and temperature difference on the surface can be roughly considered to be equal to 0. Since there is no geogas migration power, surface mineralization (chemical) substances cannot form obvious geogas anomalies.

[0008] 2) Although we know that the geogas anomaly reflects the mineralization information from deep inside, we cannot know how deep the source of the anomaly (mineralized body) is buried, nor can we know the depth and extension length of the pegmatite rare metal ore as a vein ore body.

[0009] There are also two problems in the X-ray fluorescence survey of pegmatite rare metal ores:

[0010] 1) It can only capture the anomalies of mineralization near the surface, but cannot make judgments on the deep mineralization of pegmatite veins.

[0011] 2) For low atomic number pegmatite rare metal ores such as Li and Be, X-ray fluorescence measurement cannot directly obtain abnormal element information in the ore body. Summary of the invention

[0012] The purpose of the present invention is to provide a method for inferring the extension of pegmatite rare metal ore by using ground gas and X-ray fluorescence anomaly in order to overcome the defects of the prior art. The present invention combines ground gas with X-ray fluorescence measurement, and with the help of the data processing and interpretation method specially established for pegmatite rare metal ore, the two methods make up for each other's respective technical defects, obtain the prospecting information from the surface to the deep required for the exploration of pegmatite rare metal ore, and determine the top position and direction of the pegmatite rare metal vein on the plane; in the deep, the extended length and burial depth of the vein are roughly determined.

[0013] The object of the present invention is achieved through the following technical solutions:

[0014] A method for inferring the depth of pegmatite rare metal ore using ground gas and X-ray fluorescence anomaly, the method for inferring the depth of pegmatite veins at least comprises the following steps:

[0015] S1: Based on the X-ray fluorescence method, complete the measurement of the content of each characteristic fluorescent element in the soil samples of the target area, and based on the abnormal conditions of each element in the measurement results, complete the determination of abnormal areas with further work value;

[0016] S2: For the working section in the abnormal area, the geogas method is measured on the side of the pegmatite vein that overturns underground to obtain the geogas information above the deep pegmatite vein on the overturned side of the pegmatite vein, and the profile of the corresponding elements is completed based on the content of the local geogas elements obtained from the geogas information, and the abnormal position on the profile is divided;

[0017] S3: Determine whether the abnormal gas material comes from the deep pegmatite rare metal ore body. If so, proceed to S4;

[0018] S4: Determine the dip angle α of the pegmatite rare metal vein based on the previous geological and engineering data of the target area, and compile a comprehensive profile including geogas anomalies and X-ray fluorescence anomalies based on the topographic map of the target area;

[0019] S5: Based on the comprehensive profile obtained in S4, the extended length and burial depth of the pegmatite vein are inferred.

[0020] According to a preferred embodiment, the comprehensive profile obtained in step S4 also includes: point A, the projection position of the top of the pegmatite vein on the ground surface, and point B, the projection position of the boundary point of the maximum depth of the vein extension on the ground surface, wherein point A is obtained based on step S1 using X-ray fluorescence anomaly; point B is determined based on the abnormal boundary measured on the overturned side of the vein using the geogas method in step S2.

[0021] According to a preferred embodiment, step S5 specifically includes: obtaining a horizontal distance L0 between point A and point B based on the positions of point A and point B; obtaining a height difference h1 of point B relative to point A based on a topographic map of the target area;

[0022] Then the extended length of the pegmatite vein is l = L0 / cosα;

[0023] The depth of the maximum depth boundary point of the vein extension relative to point A is h2= L0*tanα, so the burial depth of the maximum depth boundary point of the vein extension is h = (h1+h2).

[0024] According to a preferred embodiment, step S1 specifically includes:

[0025] S11: In the target area, lay out X-ray fluorescence survey lines or survey areas in a direction substantially perpendicular to the strike direction of known pegmatite veins in the area;

[0026] S12: For soil samples collected along the survey line or within the survey area, dry the soil samples naturally under the premise of ensuring that the soil does not clump;

[0027] S13: sieving the air-dried soil sample obtained in step S12, and retaining the successfully sieved soil as a sample to be tested;

[0028] S14: Complete the content measurement of fluorescent elements Nb, Ta, Rb, Y, and Zr in the sample to be tested by X-ray fluorescence instrument;

[0029] S15: obtaining a number of mapping parameters based on the content of each element measured in step S4, and compiling a cross-sectional view or a plane cross-sectional view based on each mapping parameter; and compiling a plane contour map based on the plane cross-sectional view;

[0030] When the X-ray fluorescence anomaly is confirmed to be a pegmatite rare metal ore anomaly, the anomaly position confirmed by each section in the plane contour map reflects the projection position of the pegmatite vein or its top on the surface;

[0031] S16: When measuring a section or an area, if an abnormality is found in each mapping parameter and the abnormal position of each parameter is consistent, the abnormality is determined to be an abnormality with further work value, or the abnormal area is determined to be an area with further work value.

[0032] According to a preferred embodiment, step S13 specifically includes: passing the air-dried soil sample obtained in step S12 through an 80-mesh sieve, and retaining soil with a mesh size smaller than 80 mesh as a sample to be tested.

[0033] According to a preferred embodiment, the mapping parameters are: element content ratios of Nb / Zr, Ta / Zr, Rb / Zr and Y / Zr; or the element contents of Nb, Ta, Rb and Y; when the anomaly formed by a single element or element ratio is not significant, the mapping parameters are: element content ratios of (Nb+Ta+Rb) / Zr, (Nb+Rb+Y) / Zr; or the element contents of Nb+Ta+Rb, Nb+ Rb+Y.

[0034] According to a preferred embodiment, step S2 specifically includes:

[0035] S21: On the profile, dynamic geogas sampling is performed on the side of the pegmatite vein that overturns underground, starting from the front end of the anomaly, which is collinear and co-pointed with the X-ray fluorescence measurement. The contents of elements including Li, Be, Nb, Ta, Rb, Y, U, Th, Cs, Zr, and a full set of rare earth elements in the gas samples are analyzed to obtain geogas information above the deep pegmatite vein on the overturned side of the pegmatite vein.

[0036] S22: After contrast processing of the content of each element obtained from the ground-gas measurement, the profiles of the rare metal cluster elements and radioactive elements Li, Be, Nb, Ta, Rb, Y, U, Th, and Cs measured by the ground-gas measurement are compiled respectively, and the abnormal positions on the profiles are divided.

[0037] According to a preferred embodiment, in step S21, the element content in each ground gas sample is analyzed by ICP-MS method.

[0038] The aforementioned main scheme of the present invention and its further options can be freely combined to form multiple schemes, all of which are schemes that can be adopted and claimed for protection by the present invention. After understanding the scheme of the present invention, those skilled in the art can understand that there are multiple combinations based on the prior art and common knowledge, all of which are technical schemes to be protected by the present invention, and they are not exhaustively listed here.

[0039] Beneficial effects of the present invention: Compared with the traditional geochemical prospecting method, soil measurement based on a handheld X-ray fluorescence instrument has the advantages of being able to be carried out in the field, being fast, low-cost, and having a short period of time to obtain prospecting information. In addition, when combined with geogas measurement, it avoids the situation where the non-ore anomaly is identified as an ore anomaly due to the inability to directly measure and obtain the ore body elements of low atomic number (such as Li, Be) pegmatite rare metal ores. When geogas measurement is combined with X-ray fluorescence measurement, it not only makes up for the problem that geogas measurement is not sensitive to surface mineralization information and it is difficult to roughly locate the projection position of the top of the ore body on the surface, but also effectively solves the problem that traditional geophysical prospecting methods cannot directly obtain deep mineralization information of pegmatite rare metal mines. Through the method of the present invention, deep mineralization information that is urgently needed in the prospecting of pegmatite rare metal mines can be provided, and the problem of determining the depth of the ore vein extending underground and the length of the ore vein can be basically solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a principle diagram of the method of the present invention for inferring the top position of the ore vein, the extension length of the mineralized section and the buried depth;

[0041] Figure 2 It is a ground gas and X-ray fluorescence comprehensive anomaly interpretation inference diagram according to an embodiment of the present invention;

[0042] Figure 3 It is a diagram for calculating the depth of the ore vein according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and the features in the embodiments can be combined with each other without conflict. It should be noted that in order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments.

[0044] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate the orientation or positional relationship in which the product of the invention is usually placed when in use, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, terms such as "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but may be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but may be slightly tilted.

[0045] refer to Figure 1 As shown, the present invention discloses a method for inferring the spatial distribution of pegmatite veins based on ground gas and X-ray fluorescence, and the method for inferring the spatial distribution of pegmatite veins comprises at least the following steps:

[0046] Step S1: Complete the measurement of the content of each element in the soil sample of the target area based on the X-ray fluorescence method, and complete the determination of abnormal areas with further work value based on the abnormal conditions of each element in the measurement results.

[0047] Preferably, the step S1 specifically includes:

[0048] Step S11: In the target area, X-ray fluorescence survey lines or survey areas are arranged substantially perpendicular to the strike direction of known pegmatite veins in the area.

[0049] Step S12: For the soil samples collected in the survey line or survey area, the soil samples are naturally air-dried under the premise of ensuring that the soil does not clump.

[0050] Step S13: sieve the air-dried soil sample obtained in step S12, and retain the successfully sieved soil as the sample to be tested.

[0051] Furthermore, step S13 specifically includes: passing the air-dried soil sample obtained in step S12 through an 80-mesh sieve, and retaining soil with a mesh size smaller than 80 as a sample to be tested, so as to screen out soil particles most enriched in rare metal cluster elements.

[0052] Step S14: The content of the fluorescent elements Nb, Ta, Rb, Y, and Zr in the sample to be tested is measured by an X-ray fluorescence instrument. Specifically, on the handheld X-ray fluorescence instrument, the "soil" mode is selected to measure the content of Nb, Ta, Rb, Y, and Zr elements in the soil that has passed through an 80-mesh sieve (or the net peak area of ​​the X-ray fluorescence spectrum of the elements).

[0053] Step S15: Based on the content of each element measured in step S4, a number of mapping parameters are obtained, and based on each mapping parameter, a profile diagram is compiled (when mapping by element ratio or element cumulative ratio, the measured value of each element must first be subjected to contrast processing) or a plane profile diagram (for area measurement work, a plane profile diagram with the geological map of the survey area as the base map should be compiled).

[0054] When the X-ray fluorescence anomaly is confirmed to be a pegmatite rare metal ore anomaly, the anomaly position confirmed in each section in the planar profile reflects the projection position of the pegmatite vein or its top on the surface.

[0055] Preferably, the imaging parameters are: ratios of fluorescent element contents such as Nb / Zr, Ta / Zr, Rb / Zr and Y / Zr; or contents of fluorescent elements such as Nb, Ta, Rb, Y, etc.

[0056] Alternatively, the mapping parameters are: the ratio of the cumulative content of fluorescent elements of (Nb+Ta+Rb) / Zr, (Nb+Rb+Y) / Zr; or the cumulative content of elements of Nb+Ta+Rb, Nb+Rb+Y.

[0057] Specifically, the X-ray fluorescence measurement profile varies depending on the rare metal ore.

[0058] For low atomic number pegmatite rare metal ores such as Li and Be, (Nb+Rb+Ta) / Zr (or Nb+Rb+Ta), (Nb+Rb+Y) / Zr (or Nb+Rb+Y), etc. are generally used to make mapping parameters (the ore composition in different mining areas will be different, and the best indicator element for cumulative ratios may also be different, and should be selected based on experiments).

[0059] For high atomic number pegmatite rare metal ores such as Nb and Ta, it is better to use (Nb+Rb+Ta) / Zr (or Nb+Rb+Ta), Nb, and Rb. Before converting the cumulative ratio (or cumulative value), the X-ray fluorescence measurement values ​​of elements such as Nb, Rb, Ta, Y, and Zr should all be values ​​that have been contrasted.

[0060] Step S16: When measuring a section or an area, if an abnormality is found in each mapping parameter and the abnormal position of each parameter is consistent, the abnormality is determined to be an abnormality with further work value, or the abnormal area is determined to be an area with further work value.

[0061] Specifically, for profile (or area) measurements, if anomalies are found in parameters such as Nb / Zr (or Nb), Rb / Zr (or Rb), [(Nb+Ta+Rb) / Zr] (or Nb+Ta+Rb), [(Nb+Rb+Y) / Zr] (or Nb+ Rb+Y), and the anomaly positions of the parameters are basically consistent, and the anomaly amplitude of at least one parameter exceeds 2, then it can be preliminarily determined that the anomaly found is worthy of further work.

[0062] Step S2: For the working section in the abnormal area, geogas method measurement is performed on the side of the pegmatite vein that overturns underground to obtain geogas information above the deep pegmatite vein on the overturned side of the pegmatite vein, and the profile of the corresponding element is completed based on the content of each element obtained from the geogas information, and the abnormal position on the profile is divided;

[0063] Preferably, the step S2 specifically includes:

[0064] Step S21: On the profile, on the side of the pegmatite vein overturning underground, dynamic geogas sampling is performed from the front end of the anomaly on the same line and point as the X-ray fluorescence measurement, and the content of elements including Li, Be, Nb, Ta, Rb, Y, U, Th, Cs, Zr, and a full set of rare earth elements in the geogas samples are analyzed to obtain geogas information above the deep pegmatite vein on the overturned side of the pegmatite vein. Further, in step S21, the element content in each geogas sample is analyzed by ICP-MS. (If the area X-ray fluorescence measurement is carried out in the early stage, a profile with obvious anomalies and geological representativeness is selected to perform the same geogas measurement work)

[0065] Step S22: After contrast processing of the content of each element obtained from the ground-gas measurement, the profiles of the rare metal cluster elements and radioactive elements Li, Be, Nb, Ta, Rb, Y, U, Th, and Cs measured by the ground-gas measurement are compiled respectively, and the abnormal positions on the profiles are divided.

[0066] Specifically, the geogas measurement profile should use the ore body elements of the ore body being explored. For example, for pegmatite Li ore, the geogas profile mapping parameters should use the Li element content or its contrast value. For pegmatite Nb and Ta ore, the mapping parameters should use the contrast accumulation value of (Nb+Ta), or a profile composed of the two element contents of Nb and Ta or their contrast values ​​respectively.

[0067] Step S3: determine whether the abnormal gas material comes from the deep pegmatite rare metal ore body, if so, proceed to S4;

[0068] Specifically, rare earth elements can be used as tracers to determine whether the abnormal geogas substances come from deep pegmatite rare metal ore bodies. By comparing the rare earth element distribution curve of the abnormal area on the geogas profile with the rare earth element distribution curve of the known pegmatite rare metal ore in the exploration area, if the change trends of the two rare earth element distribution curves are basically the same, it can be basically determined that the source of the material causing the geogas anomaly comes from the corresponding pegmatite rare metal mineral (mineralization) body deep in the abnormal area. In other words, the corresponding geogas anomaly can be identified as a mineral (chemical) anomaly.

[0069] Step S4: Determine the inclination angle α of the pegmatite vein based on the previous geological and engineering data of the target area, and compile a comprehensive profile including geogas anomalies and X-ray fluorescence anomalies based on the topographic map of the target area, that is, Figure 1 Schematic diagram showing the location of the top of the inferred vein, the extended length of the mineralized section and the buried depth.

[0070] Among them, the comprehensive profile obtained in step S4 also includes: point A, the projection position of the top of the pegmatite vein on the ground surface, and point B, the projection position of the boundary point of the maximum depth of the vein extension on the ground surface, wherein point A is obtained based on step S1 using X-ray fluorescence anomaly; point B is determined based on the abnormal boundary measured on the overturned side of the vein using the geogas method in step S2.

[0071] Step S5: Based on the comprehensive profile obtained in S4, the extended length and buried depth of the pegmatite vein are inferred.

[0072] Further, step S5 specifically includes: based on the positions of point A and point B, obtaining a horizontal distance L0 between point A and point B; based on the topographic map of the target area, obtaining a height difference h1 between point B and point A;

[0073] Then the extended length of the pegmatite vein l = L0 / cosα;

[0074] The depth of the maximum depth boundary point of the vein extension relative to point A is h2= L0*tanα, so the burial depth of the maximum depth boundary point of the vein extension is h = (h1+h2).

[0075] Compared with the traditional geochemical prospecting method, the soil measurement based on the handheld X-ray fluorescence instrument of the present invention has the advantages of being able to be carried out in the field, fast, low cost, and short period of obtaining prospecting information. In addition, when combined with geogas measurement, it avoids the situation that non-ore anomalies may be identified as ore anomalies due to the inability to directly measure and obtain ore body elements for low atomic number (such as Li, Be) pegmatite rare metal ores. When geogas measurement is combined with X-ray fluorescence measurement, it not only makes up for the problem that geogas measurement is not sensitive to surface mineralization information and it is difficult to roughly locate the projection position of the top of the ore body on the surface, but also effectively solves the problem that traditional geophysical prospecting methods cannot directly obtain deep mineralization information of pegmatite rare metal ores.

[0076] Embodiment 1:

[0077] refer to Figure 2 and Figure 3 As shown, this embodiment discloses the prospecting results of the Kaluan pegmatite lithium deposit in Fuhai County, Xinjiang. In the early exploration, it was believed that the pegmatite veins generally extended to 200m underground, and would not exceed 250m at most. In 2017, the inventor of this patent conducted a comprehensive geogas exploration experiment for pegmatite lithium ore in the Kaluan mining area. On the overturned side of the No. 806 pegmatite lithium vein on the L2 survey line, based on l0 and the overturning angle of the ore body, the largest continuous comprehensive anomaly area on the survey line reflecting the existence of lithium ore bodies at a depth of more than 250m was captured (see Appendix Figure 2 ).

[0078] Based on the attached Figure 1 The method disclosed in the present invention can establish Figure 3 The vein extension estimation diagram shown in the figure shows that the deep extension length l of the No. 806 vein from the surface to the left boundary of the anomaly along the 56° inclination is calculated as:

[0079] l=400 / (cos56°)=715(m)

[0080] This anomaly revealed that the vein did not extend to a depth of only 200m as previous work had believed, but may extend to a depth of more than 400m.

[0081] This achievement has achieved two geological benefits:

[0082] (1) For the No. 806 pegmatite vein, the ore reserves can be increased by more than 1 times;

[0083] (2) A new prospecting idea was proposed: the pegmatite veins of the Kaluan deposit extend to a depth of not more than 200 m. The prospecting of pegmatite lithium deposits in the Kaluan area still has great prospecting potential after the depth exceeds 200 m.

[0084] This prospecting result was confirmed and affirmed by the local geological team's further prospecting work.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for inferring the depth of pegmatite rare metal ore using ground gas and X-ray fluorescence anomaly, characterized in that: The inference of the extended length and buried depth of the pegmatite rare metal vein comprises at least the following steps: S1: Based on the X-ray fluorescence method, complete the measurement of the content of each fluorescence characteristic indicator element in the soil sample of the target area, and based on the abnormal conditions of each element in the measurement results, complete the determination of abnormal areas with further work value; S2: For the working section in the abnormal area, the geogas method is measured on the side of the pegmatite vein that overturns underground, and the geogas information above the deep pegmatite vein on the overturned side of the pegmatite vein is obtained. Based on the content of the elements indicating the characteristics of the various geothermal elements obtained from the geogas information, the profile of the corresponding elements is completed, and the abnormal position on the profile is divided; S3: Determine whether the abnormal gas material comes from the deep pegmatite rare metal ore body. If so, proceed to S4; S4: Determine the dip of pegmatite veins based on the previous geological and engineering data of the target area α , and compile a comprehensive profile including geogas anomalies and X-ray fluorescence anomalies based on the topographic map of the target area; The comprehensive profile obtained in step S4 also includes: point A, the projection position of the top of the pegmatite vein on the ground surface, and point B, the projection position of the boundary point of the maximum depth of the vein on the ground surface, wherein point A is obtained based on step S1 using X-ray fluorescence anomaly; point B is determined by the anomaly boundary measured on the overturned side of the vein using the geogas method based on step S2; S5: Based on the comprehensive profile obtained in S4, the extended length and buried depth of the pegmatite rare metal veins are inferred; Step S5 specifically includes: based on the positions of point A and point B, obtaining the horizontal distance between point A and point B L 0 ; Based on the topographic map of the target area, obtain the height difference between point B and point A h 1 ; The extended length of the pegmatite vein l= L 0 / cosα ; The depth of the maximum depth boundary point of the vein relative to point A h 2 = L 0 *tanα , then the buried depth of the maximum depth boundary point of the ore vein is h = (h 1 +h 2 ） .

2. The method for inferring the extension of pegmatite rare metal veins according to claim 1, characterized in that: The step S1 specifically includes: S11: In the target area, lay out X-ray fluorescence survey lines or survey areas in a direction substantially perpendicular to the strike direction of known pegmatite veins in the area; S12: For soil samples collected along the survey line or within the survey area, dry the soil samples naturally under the premise of ensuring that the soil does not clump; S13: sieving the air-dried soil sample obtained in step S12, and retaining the successfully sieved soil as a sample to be tested; S14: Complete the content measurement of fluorescent elements Nb, Ta, Rb, Y and Zr in the sample to be tested by X-ray fluorescence instrument; S15: obtaining a number of mapping parameters based on the content of each element measured in step S4, and compiling a cross-sectional view or a plan cross-sectional view based on each mapping parameter; When the X-ray fluorescence anomaly is confirmed to be a pegmatite rare metal ore anomaly, the anomaly position confirmed in each section on the planar section diagram reflects the projection position of the pegmatite vein or its top on the surface; S16: When measuring a section or an area, if an abnormality is found in each mapping parameter and the abnormal position of each parameter is consistent, the abnormality is determined to be an abnormality with further work value, or the abnormal area is determined to be an area with further work value.

3. The method for inferring the extended length and buried depth of a pegmatite rare metal vein as claimed in claim 2, characterized in that: Step S13 is specifically as follows: the air-dried soil sample obtained in step S12 is sieved through an 80-mesh sieve, and soil with a sieve size smaller than 80 mesh is retained as a sample to be tested.

4. The method for inferring the extended length and buried depth of a pegmatite rare metal vein as claimed in claim 2, characterized in that: The mapping parameters are: the element content ratios of Nb / Zr, Ta / Zr, Rb / Zr and Y / Zr; or the element contents of Nb, Ta, Rb and Y; when the single element parameter abnormality is not significant, the mapping parameters are: the element content cumulative ratios of (Nb+Ta+Rb) / Zr and (Nb+Rb+Y) / Zr; Or it may be the cumulative value of the element contents of Nb+Ta+Rb and Nb+Rb+Y.

5. The method for inferring the extended length and buried depth of a pegmatite rare metal vein according to claim 1, characterized in that: The step S2 specifically includes: S21: On the profile, on the side of the pegmatite vein overturning underground, start dynamic geogas sampling on the same line and point as the X-ray fluorescence measurement from the front end of the anomaly, and analyze the contents of geogas elements including Li, Be, Nb, Ta, Rb, U, Th, Cs, Zr and a full set of rare earth elements in the gas samples of each place, to obtain geogas information above the deep pegmatite vein on the overturning side of the pegmatite vein; S22: After contrast processing of the content of each element obtained from the ground-gas measurement, the profiles of the rare metal cluster elements and radioactive elements Li, Be, Nb, Ta, Rb, Y, U, Th and Cs measured by the ground-gas measurement are compiled respectively, and the abnormal positions on the profiles are demarcated.

6. The method for inferring the spatial distribution of pegmatite veins according to claim 5, characterized in that: In step S21, the element content in each ground gas sample is analyzed by ICP-MS method.

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