Deep niobium phosphorite positioning physical and chemical exploration method based on multi-method cooperation

Abstract

The invention discloses a deep niobium phosphate ore positioning physical and chemical exploration method based on multi-method cooperation, and belongs to the technical field of geological mineral exploration. According to the method, a three-stage exploration system of region optimization, target region delineation and fine verification is constructed, multi-parameter cooperation of a magnetic method, an electromagnetic method, an induced polarization method, a three-component magnetic logging method and a geochemical method is combined, and each step is constrained by a basic rock-niobium phosphorite metallogenic model. An ore prospecting mark is determined through regional geological background analysis and metallogenic model construction, a metallogenic prospective region is delineated through regional optimization, a specific target region is delineated and locked, engineering verification is carried out through fine verification, and finally, a result is integrated to estimate the resource quantity. According to the method, the multiplicity of solutions of a single method is effectively reduced, the positioning precision of the deep niobium phosphorite is improved, the exploration efficiency and the target area ore finding rate are improved, and the method is suitable for accurate exploration of the deep niobium phosphorite.

Description

Technical Field

[0001] This invention relates to the field of geological and mineral exploration technology, and in particular to a geophysical and geochemical exploration method for locating deep niobium-phosphate deposits based on multi-method synergy. Background Technology

[0002] Niobium-phosphate deposits, as important strategic mineral resources, play an irreplaceable role in industry, new energy, and other fields. The occurrence and distribution patterns of niobium-bearing minerals (such as columbite and pyrochlore) and phosphorus-bearing minerals (such as apatite) have always been a key focus of geological and mineral exploration research. These deposits are mostly formed in deep alkaline-carbonate complexes, with few surface outcrops, making exploration quite challenging. Currently, the field of geological and mineral exploration has formed a geophysical and geochemical exploration technology system centered on magnetic methods, electromagnetic methods, and geochemical measurements. These methods are widely used in mineral exploration at different scales, providing important technical support for the discovery and evaluation of mineral resources.

[0003] However, existing technologies still have significant limitations in deep niobium-phosphate exploration: First, single geophysical and geochemical methods lack sufficient sensitivity to identify deep niobium-phosphate ore bodies with weak magnetic properties and low to medium resistivity, making it difficult to effectively capture mineralization information under complex geological conditions; Second, traditional method combinations often focus on surface or shallow anomalies, lacking multi-parameter collaborative analysis of deep structural, alteration, and mineralization characteristics, resulting in strong ambiguity in anomaly interpretation; Third, the exploration process is not fully optimized by incorporating the mineralization regularities of alkaline rocks and niobium-phosphate deposits (such as the relationship between magmatic activity and tectonic mineralization), resulting in a lack of clear guidance for target area delineation and making it difficult to meet the need for precise location of deep (burial depth > 300m) niobium-phosphate deposits. Summary of the Invention

[0004] The purpose of this invention is to overcome one or more shortcomings of the prior art and provide a geophysical and geochemical exploration method for locating deep niobium-phosphate deposits based on multi-method synergy.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A multi-method collaborative geophysical and geochemical exploration method for locating deep niobium-phosphate deposits includes the following steps:

[0007] (1) Regional geological background analysis and metallogenic model construction: Collect geological data, remote sensing images and regional geophysical databases of the study area, analyze the distribution patterns of alkaline rock-carbonate complex, fault structures and alteration zones; combine known niobium-phosphate deposit metallogenic models to determine key prospecting indicators;

[0008] (2) Regional optimization: The combined methods of airborne magnetic survey, ground high-precision magnetic survey, remote sensing structural extraction and geochemical measurement were used to process the data and delineate the composite anomaly zone of "magnetic anomaly + dense fault zone + niobium element anomaly concentration center". Combined with the regional geochemical background value, the prospective mineralization area was determined.

[0009] (3) Target area delineation: A combination of airborne magnetics, audio magnetotellurics and deep soil geochemical measurements is used to process the data to construct a three-dimensional model, invert the low resistivity body and extract the main ore-forming element combination. The specific target area is locked by the four superposition anomalies of "high gravity + magnetic anomaly + low resistivity alteration zone + high concentration secondary halo".

[0010] (4) Detailed verification: A combination of induced polarization method, wide-area electromagnetic method, rock geochemical profile and three-component magnetic logging method is used to identify high polarizability alteration zones, invert deep structures and concealed rock masses, indicate deep mineralization and corresponding magnetic bodies, and arrange verification boreholes for engineering verification.

[0011] (5) Results integration: Based on the borehole verification results, the ore body boundary is delineated by combining the three-dimensional model of geophysical and geochemical anomalies, and the resource quantity is estimated by the geological block method or the kriging method.

[0012] Furthermore, in step (1), the key mineral exploration indicators include: high-density alteration zone: density difference Δρ is 0.3 to 0.8 g / cm³; weak magnetic alteration zone: magnetic anomaly ΔT is 30 to 100 nT; high polarizability alteration zone: polarizability ηs is 5% to 10%; medium-low resistivity alteration zone: resistivity ρs is 20 to 100 Ω·m; and enrichment areas of niobium, phosphorus, nickel, titanium, tantalum, rare earth elements, thorium, and uranium.

[0013] Furthermore, in step (2), the scale of the airborne magnetic survey is 1:200,000, the scale of the ground high-precision magnetic survey is 1:50,000, the remote sensing structure extraction utilizes remote sensing data and digital elevation data, and the scale of the geochemical measurement is 1:25,000; the data processing includes: calculating the residual gravity anomaly after topographic correction and Bouguer correction of gravity data: Δg_residual > 5 × 10⁻ 5 m / s²; Magnetic data calculation of total magnetic anomaly: T_residual > 10 nT; Remote sensing extraction of areas with fracture density > 0.5 fractures / km², and geochemical measurements extraction of anomalies with niobium as the main element.

[0014] Furthermore, in step (2), the geochemical measurements collect stream sediments, taking into account soil and rock debris, with a point density of 20 points / square kilometer. The analyzed elements include gold, arsenic, antimony, mercury, silver, copper, lead, zinc, tungsten, tin, molybdenum, bismuth, cobalt, chromium, nickel, lithium, beryllium, uranium, niobium, yttrium, lanthanum, zirconium, and fluorine; the anomaly with niobium as the main element has a niobium anomaly ≥36×10⁻ 6The background geochemical values ​​for the area include phosphorus pentoxide > 0.1% and total rare earth elements > 500 × 10⁻⁻⁻⁶. 6 .

[0015] Furthermore, in step (3), the aeromagnetic grid is 100m × 20m in size and extends upwards by 400m, and the frequency range of the audio magnetotelluric method is 10⁻ 4 ~10 4 The detection depth is 500-1000m, and the sampling depth of the deep soil geochemical measurement is 0.3-2m with a point spacing of 10m. The data processing includes the joint inversion of magnetic data to construct a three-dimensional magnetic model, the inversion of low resistivity (resistivity <100Ω·m) from audio magnetotelluric data, and the extraction of the main ore-forming element combination from soil data using multivariate statistical analysis.

[0016] Furthermore, in step (3), the three-dimensional magnetic model is used to identify the boundaries of concealed rock masses (such as carbonate rock masses with magnetic susceptibility κ > 0.01 SI), the main ore-forming element assemblage includes niobium-phosphorus-rare earth elements-thorium, and the secondary halo anomaly peak value of niobium > 50 × 10⁻ 6 Phosphorus pentoxide > 0.3%.

[0017] Furthermore, in step (4), the electrode spacing of the induced polarization method is 50m×20m, and the detection depth is 300-500m; the detection depth of the wide-area electromagnetic method is 500-2000m; the rock geochemical profile includes bedrock samples collected from the surface and deep boreholes, and the analyzed elements include niobium, phosphorus, rare earth elements and alteration mineral content; the three-component magnetic logging measures the vertical component and the total field.

[0018] Furthermore, in step (4), the induced polarization method is used to identify alteration zones with high polarizability (polarizability η is 5% to 10%); the deep structures inverted by the wide-area electromagnetic method include basement undulations, fault occurrences, and concealed rock masses that are carbonate rocks with velocities > 5500 m / s; the high anomalies in the vertical component and total field of the three-component magnetic logging correspond to magnetic bodies (such as magnetite and niobite).

[0019] Furthermore, in step (4), the verification borehole is 500-1300m deep, and the geophysical model is verified by core physical property testing. The core physical properties include density, magnetic susceptibility, resistivity and polarizability. Sampling analysis is used to determine the grade of the ore body, which includes niobium pentoxide > 0.05% and phosphorus pentoxide > 0.3%.

[0020] Furthermore, each step incorporates constraints from an alkaline rock-niobium-phosphate mineralization model. These constraints include the selection of methods and anomaly interpretation based on the mineralization regularity of alkaline rock-niobium-phosphate deposits. The mineralization regularity includes the characteristics of "alkaline magmatic activity - tectonic ore control - hydrothermal alteration enrichment".

[0021] The beneficial effects of this invention are:

[0022] (1) By combining multiple methods, integrating technologies such as magnetic surveying, electromagnetic surveying, and geochemical surveying, we can comprehensively capture the distribution, alteration characteristics, and mineralization information of rock masses, effectively reduce the multiple interpretations caused by a single method, and thus more accurately locate deep niobium-phosphate deposits.

[0023] (2) By advancing the target area in stages, from regional selection to target area delineation and then to detailed verification, the exploration scope is gradually narrowed, so that the exploration work focuses on high-potential areas, reduces ineffective exploration links, and significantly improves the overall efficiency of deep niobium and phosphate exploration.

[0024] (3) By constraining the mineralization model, the mineralization regularity of alkaline rock-niobium phosphate deposits guides the selection of method combinations and anomaly interpretation at each stage, clarifies the exploration direction, reduces blindness, and makes the target area delineation more in line with the ore body occurrence regularity, effectively improving the ore occurrence rate of the target area. Attached Figure Description

[0025] Figure 1 This is a flowchart of the geophysical and geochemical exploration method for locating deep niobium-phosphate deposits as described in this invention;

[0026] Figure 2 A plan view of the composite anomaly of "magnetic anomaly + remote sensing fault + geochemical anomaly" in the regional optimization stage;

[0027] Figure 3 Plan view of "airborne magnetic method, ground magnetic method, and surface ore body distribution" for the target area delineation stage;

[0028] Figure 4 This is a simulated cross-section diagram of "magnetic anomaly + WFEM low-resistivity three-dimensional inversion model + borehole verification" in the fine verification stage. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A multi-method collaborative geophysical and geochemical exploration method for locating deep niobium-phosphate deposits is provided, comprising the following steps:

[0032] (1) Regional geological background analysis and metallogenic model construction: Collect geological data, remote sensing images and regional geophysical databases of the study area, analyze the distribution patterns of alkaline rock-carbonate complex, fault structures and alteration zones; combine known niobium-phosphate deposit metallogenic models to determine key prospecting indicators;

[0033] (2) Regional optimization: The combined methods of airborne magnetic survey, ground high-precision magnetic survey, remote sensing structural extraction and geochemical measurement were used to process the data and delineate the composite anomaly zone of "magnetic anomaly + dense fault zone + niobium element anomaly concentration center". Combined with the regional geochemical background value, the prospective mineralization area was determined.

[0034] (3) Target area delineation: A combination of airborne magnetics, audio magnetotellurics and deep soil geochemical measurements is used to process the data to construct a three-dimensional model, invert the low resistivity body and extract the main ore-forming element combination. The specific target area is locked by the four superposition anomalies of "high gravity + magnetic anomaly + low resistivity alteration zone + high concentration secondary halo".

[0035] (4) Detailed verification: A combination of induced polarization method, wide-area electromagnetic method, rock geochemical profile and three-component magnetic logging method is used to identify high polarizability alteration zones, invert deep structures and concealed rock masses, indicate deep mineralization and corresponding magnetic bodies, and arrange verification boreholes for engineering verification.

[0036] (5) Results integration: Based on the borehole verification results, the ore body boundary is delineated by combining the three-dimensional model of geophysical and geochemical anomalies, and the resource quantity is estimated by the geological block method or the kriging method.

[0037] In step (1), the key mineral exploration indicators include: high-density alteration zone: density difference Δρ is 0.3 to 0.8 g / cm³; weak magnetic alteration zone: magnetic anomaly ΔT is 30 to 100 nT; high polarizability alteration zone: polarizability ηs is 5% to 10%; medium-low resistivity alteration zone: resistivity ρs is 20 to 100 Ω·m; and enrichment areas of niobium, phosphorus, nickel, titanium, tantalum, rare earth elements, thorium, and uranium.

[0038] In step (2), the scale of the airborne magnetic survey is 1:200,000, the scale of the ground high-precision magnetic survey is 1:50,000, the remote sensing structure extraction utilizes remote sensing data and digital elevation data, and the scale of the geochemical measurement is 1:25,000; the data processing includes: calculating the residual gravity anomaly after topographic correction and Bouguer correction of gravity data: Δg_residual > 5 × 10⁻ 5 m / s²; Magnetic data calculation of total magnetic anomaly: T_residual > 10 nT; Remote sensing extraction of areas with fracture density > 0.5 fractures / km², and geochemical measurements extraction of anomalies with niobium as the main element.

[0039] In step (2), the geochemical measurements collect stream sediments, taking into account soil and rock debris, with a point density of 20 points / square kilometer. The analyzed elements include gold, arsenic, antimony, mercury, silver, copper, lead, zinc, tungsten, tin, molybdenum, bismuth, cobalt, chromium, nickel, lithium, beryllium, uranium, niobium, yttrium, lanthanum, zirconium, and fluorine; the anomaly with niobium as the main element has a niobium anomaly ≥36×10⁻ 6 The background geochemical values ​​for the area include phosphorus pentoxide > 0.1% and total rare earth elements > 500 × 10⁻⁻⁻⁶. 6 .

[0040] In step (3), the aeromagnetic grid is 100m × 20m and extends upwards by 400m, and the frequency range of the audio magnetotelluric method is 10⁻ 4 ~10 4 The detection depth is 500-1000m, and the sampling depth of the deep soil geochemical measurement is 0.3-2m with a point spacing of 10m. The data processing includes the joint inversion of magnetic data to construct a three-dimensional magnetic model, the inversion of low resistivity (resistivity <100Ω·m) from audio magnetotelluric data, and the extraction of the main ore-forming element combination from soil data using multivariate statistical analysis.

[0041] In step (3), the three-dimensional magnetic model is used to identify the boundaries of concealed rock masses (such as carbonatite bodies with magnetic susceptibility κ > 0.01 SI), the main ore-forming element assemblage includes niobium-phosphorus-rare earth elements-thorium, and the secondary halo anomaly peak niobium > 50 × 10⁻ 6 Phosphorus pentoxide > 0.3%.

[0042] In step (4), the electrode spacing of the induced polarization method is 50m×20m, and the detection depth is 300-500m; the detection depth of the wide-area electromagnetic method is 500-2000m; the rock geochemical profile includes bedrock samples collected from the surface and deep boreholes, and the analyzed elements include niobium, phosphorus, rare earth elements and alteration mineral content; the three-component magnetic logging measures the vertical component and the total field.

[0043] In step (4), the induced polarization method is used to identify alteration zones with high polarizability (polarizability η is 5% to 10%); the deep structures inverted by the wide-area electromagnetic method include basement undulations, fault occurrence, and concealed rock bodies are carbonate rocks with velocities > 5500 m / s; the high anomalies in the vertical component and total field of the three-component magnetic logging correspond to magnetic bodies (such as magnetite and niobite).

[0044] In step (4), the verification borehole is 500-1300m deep, and the geophysical model is verified by core physical property testing. The core physical properties include density, magnetic susceptibility, resistivity and polarizability. Sampling analysis is used to determine the grade of the ore body. The grade includes niobium pentoxide > 0.05% and phosphorus pentoxide > 0.3%.

[0045] Each step incorporates constraints from an alkaline rock-niobium-phosphate mineralization model. These constraints include the selection of methods and anomaly interpretation based on the mineralization regularity of alkaline rock-niobium-phosphate deposits. The mineralization regularity includes the characteristics of "alkaline magmatic activity - tectonic ore control - hydrothermal alteration enrichment".

[0046] Example 2

[0047] An Example of a Multi-Method Collaborative Geophysical and Geochemical Exploration Method for Locating Deep Niobium-Phosphorus Deposits

[0048] I. Regional geological background analysis and metallogenic model construction:

[0049] Before conducting deep niobium-phosphate exploration, the primary task is to study the geological background of the area and construct a mineralization model.

[0050] Data Collection and Basic Analysis: 1:50,000 geological maps, high-resolution remote sensing images (such as multispectral fusion images), and regional geophysical (gravity and magnetic) databases of the study area were collected. Field geological surveys were used to supplement and verify the surface characteristics of rock masses, structures, and alteration zones. The focus was on observing the lithological assemblage of alkaline-carbonate complexes (such as calcite carbonate rocks, pyroxene rocks, and peridotite), recording their contact relationships with surrounding strata, as well as the strike, density, and cutting characteristics of fault structures. Simultaneously, surface rock samples were systematically collected, and their physical properties were tested, including density (Δρ = 0.3–0.8 g / cm³), magnetic susceptibility, polarizability (ηs = 5%–10%), and resistivity (ρs = 20–100 Ω·m), providing physical property evidence for subsequent geophysical anomaly interpretation.

[0051] Metallogenic Model Construction and Prospecting Indicators Determination: Based on the known metallogenic characteristics of niobium-phosphate deposits, a metallogenic model of "alkaline magmatic activity - tectonic control of ore deposits - hydrothermal alteration enrichment" was constructed. This model clarifies that: multiple phases of alkaline magmatic activity provide material sources for the enrichment of elements such as niobium and phosphorus; fault structures (especially densely faulted zones) provide channels and space for ore fluid migration and ore body occurrence; and hydrothermal alteration (such as phlogopitization, carbonatization, chloritization, etc.) promotes the precipitation and enrichment of niobium-phosphate minerals (columbite, pyrochlore, apatite, etc.).

[0052] See Figure 1 Starting with "regional geological background analysis and metallogenic model construction," and through a progressive process of "regional optimization—target area delineation—refined verification—results integration," the precise location of deep niobium-phosphate deposits is achieved. The specific process is as follows:

[0053] Step 1: Regional geological background analysis and metallogenic model construction:

[0054] Data collection and basic analysis: Geological maps, high-resolution remote sensing images and regional geophysical (gravity and magnetic) databases of the study area were collected. Field reconnaissance and observation of the lithological assemblage, fault structure distribution and alteration zone characteristics of alkaline-carbonate complexes were conducted. Rock samples were collected simultaneously to test physical properties such as density (Δρ≈0.3~0.8g / cm³), magnetic susceptibility, polarizability (ηs≈5%~10%), and resistivity (ρs≈20~100Ω·m).

[0055] Metallogenic model construction: Based on known mineralization patterns of ore deposits, a model of "alkaline magmatic activity - tectonic control of ore - hydrothermal alteration and enrichment" is constructed to clarify the metallogenic logic of alkaline magma providing material sources, fault structures controlling ore fluid migration, and hydrothermal alteration promoting mineral enrichment.

[0056] Identifying mineral exploration indicators: Key indicators were refined based on the model, including high-density, weakly magnetic (ΔT≈30~100nT), high polarizability, medium-low resistivity alteration zones, and enrichment areas of elements such as Nb, P, REE, Th, and U (Nb anomaly ≥36×10⁻⁻⁻⁶). 6 , >0.1%, ΣREE>500×10⁻ 6 ).

[0057] Step 2: Regional Optimization (1:200,000 to 1:25,000 scale):

[0058] Methods were combined to obtain regional magnetic anomalies using 1:200,000 airborne magnetic surveys (grid size 2000m×500m) and 1:50,000 high-precision ground magnetic surveys (grid size 500m×100m); dense zones with fracture density >0.5 fractures / km² were extracted using remote sensing data and DEM; and 1:25,000 geochemical surveys (point density 20 points / km²) were conducted, collecting samples of stream sediments, soil, and rock debris, and analyzing 23 elements.

[0059] Data processing: Gravity data is corrected for topography and Bouguer correction before calculating residual gravity anomaly (Δg_residual > 5 × 10⁻). 5 m / s²); Magnetic data were used to calculate the total magnetic anomaly (T_remainder > 10nT); Geochemical data were used to extract Nb anomaly ≥ 36 × 10⁻ 6 The concentration center.

[0060] Delineation of mineralization prospective areas: By superimposing the composite anomaly of "magnetic anomaly + dense fault zone + Nb anomaly concentration center" and combining it with regional geochemical background values, mineralization prospective areas with an area of ​​50 to 100 km² were determined.

[0061] Step 3: Target delineation (1:10,000 to 1:5,000 scale):

[0062] Method combination implementation: 1:10,000 airborne magnetic field method (grid size 100m × 20m, extended upwards by 400m) and audio-frequency magnetotelluric method (AMT, frequency 10⁻) were used. 4 ~10 4 Hz, detection depth 500-1000m); carry out deep soil geochemical measurements (sampling depth 0.3-2m, point spacing 10m) to detect elements such as Nb, P, REE.

[0063] Data processing: Magnetic data were jointly inverted to construct a three-dimensional magnetic model and identify concealed rock mass boundaries (e.g., carbonatite bodies with magnetic susceptibility κ > 0.01 SI); AMT data were inverted to delineate alteration zones by identifying low-resistivity bodies (resistivity < 100 Ω·m); soil data were analyzed using multivariate statistical extraction of Nb-P-REE-Th elemental combinations to delineate secondary halo anomalies (peak Nb > 50 × 10⁻⁻⁻⁶). 6 , >0.3%.

[0064] Target area identification: By identifying four superimposed anomalies—high gravity, magnetic anomaly, low resistivity alteration zone, and high concentration of secondary halo—a specific target area of ​​1–3 km² is identified.

[0065] Step 4: Fine-grained verification (1:2,000 scale):

[0066] Method combination implementation: Induced polarization (IP, electrode spacing 50m×20m, detection depth 300-500m) and wide-area electromagnetic method (WFEM, detection depth 500-2000m) were used; surface and borehole bedrock samples were collected along the tectonic zone to carry out rock geochemical profile analysis; three-component magnetic logging (measuring vertical component and total field) was carried out in the borehole.

[0067] Key technology applications: IP method for identifying high polarizability alteration zones (η>5%) and delineating mineralized areas; WFEM inversion for deep structures and concealed rock masses (velocity>5500m / s); rock anomalies indicating deep mineralization; three-component magnetic logging for identifying magnetic bodies (such as niobite) corresponding to high anomalies.

[0068] Engineering verification: Verification boreholes of 500–1300 m were drilled at the center of the comprehensive anomaly. The geophysical model was verified through core physical property testing, and the grade of the ore body was determined by sampling analysis. >0.05%, >0.3%.

[0069] Step 5: Results Integration

[0070] Based on the borehole verification results, the ore body boundaries are delineated using a three-dimensional geophysical and geochemical anomaly model. The resource quantity is estimated using the geological block method or the kriging method, forming a complete exploration result to guide the deployment of deep mineral exploration drilling.

[0071] II. Regional Optimization (Scale of 1:200,000 to 1:25,000):

[0072] Regional optimization aims to screen out promising areas with mineralization potential on a macro scale, and to delineate the scope through multi-method data collection and composite anomaly analysis.

[0073] Method combination and data acquisition: A combination scheme of "airborne magnetic survey + ground high-precision magnetic survey + remote sensing structural extraction + geochemical measurement" was adopted.

[0074] Airborne magnetic survey: conducted at a scale of 1:200,000 with a grid size of 2000m×500m, to obtain regional total magnetic field distribution data for identifying the distribution range of large magnetic rock masses;

[0075] High-precision ground-based magnetic surveys: conducted at a scale of 1:50,000 with a grid size of 500m×100m, supplementing detailed information from airborne magnetic surveys and improving the resolution of magnetic anomalies;

[0076] Remote sensing structure extraction: Using multispectral remote sensing data and digital elevation models (DEM), fault structures are identified through edge detection and linear structure extraction algorithms, with a focus on delineating areas with a fault density > 0.5 faults / km².

[0077] Geochemical measurements were conducted at a scale of 1:25,000, primarily using stream sediment samples, while also considering soil and rock debris samples. The point density was 20 points / km². 23 elements, including Au, As, Sb, Nb, P, and REE, were analyzed, with a focus on capturing anomalous concentration centers of Nb.

[0078] Data processing and anomaly identification: The collected data is systematically processed to highlight mineralization-related anomalies.

[0079] After topographic and Bouguer corrections, the residual gravity anomaly is calculated from the gravity data, and Δg_residual > 5 × 10⁻ is selected. 5 High m / s² values ​​indicate the distribution of high-density rock masses;

[0080] Magnetic data is used to calculate the total magnetic anomaly and extract weak magnetic anomaly areas with T residual > 10nT, corresponding to weak magnetic ore bodies or alteration zones.

[0081] The dense fault zones extracted from remote sensing data are superimposed with magnetic and gravity anomalies to identify tectonic-rock mass composite zones.

[0082] Geochemical data were analyzed using concentration zoning and anomaly lower limits to extract Nb anomalies ≥36×10⁻. 6 The concentration center, and combined with >0.1%, ΣREE>500×10⁻ 6 The regional geochemical background value further constrains the anomaly range.

[0083] Metallogenic prospective areas were identified by superimposing a triple composite anomaly of "magnetic anomaly + dense fault zone + Nb anomaly concentration center" and combining it with the tectonic ore-controlling features in the metallogenic model. For example... Figure 2 As shown in the figure (a composite anomaly planar map of "magnetic anomaly + remote sensing fault + geochemical anomaly" in the regional selection stage), the spatial superposition relationship of magnetic anomaly (dark blocks), dense fault zone (linear lines) and Nb geochemical anomaly (light-colored concentration area) is clearly displayed. The area with the highest superposition degree (area 50-100 km²) is identified as a prospective mineralization area, providing a key range for subsequent target area delineation.

[0084] III. Target delineation (1:10,000 to 1:5,000 scale):

[0085] Within mineralized prospective areas, a combination of more precise methods can be used to narrow down the exploration scope and pinpoint specific target areas.

[0086] Method combination and data acquisition: A combination scheme of "airborne magnetometry + audio-frequency magnetotellurics (AMT) + deep soil geochemical measurement" was adopted.

[0087] Airborne magnetic method: The data is carried out at a scale of 1:10,000 with a grid size of 100m×20m. The data is then processed by extending upwards by 400m to suppress shallow interference and highlight the anomalous features of deep magnetic bodies (such as concealed carbonate rocks).

[0088] AMT measurement: Frequency range 10⁻ 4 ~10 4 Hz, with a detection depth of 500–1000 m, used to invert deep resistivity structures and identify low-resistivity alteration zones;

[0089] Deep soil geochemical measurement: sampling depth 0.3-2m (avoiding surface soil with strong surface processes), point spacing 10m, focusing on detecting elements such as Nb, P, Ni, Ti, Ta, REE, Th, U, etc., to capture secondary halos formed by the upward migration of deep ore bodies.

[0090] Data processing and model building: Constructing a three-dimensional anomaly model through multi-dimensional data processing.

[0091] Magnetic data: A three-dimensional magnetic model is constructed using joint inversion technology to identify the boundaries of concealed rock masses (such as carbonatite rock masses with magnetic susceptibility κ > 0.01SI). The morphology and distribution of magnetic bodies in the model provide rock mass background constraints for the occurrence of ore bodies.

[0092] AMT data: Invert deep low-resistivity bodies (resistivity <100Ω·m), and combine the low-resistivity characteristics of alteration minerals (phlogopite, carbonates, etc.) to delineate the range of alteration zones, which are often closely related to mineralization.

[0093] Soil geochemical data: Multivariate statistical methods such as cluster analysis and factor analysis were used to extract the main ore-forming element assemblages (e.g., Nb-P-REE-Th) and delineate secondary halo anomalies, with peak Nb > 50 × 10⁻ 6 , Areas with an anomaly rate greater than 0.3% are considered key anomaly areas.

[0094] Target area identification: Specific target areas are identified through a quadruple anomaly analysis of "high gravity + magnetic anomaly + low resistivity alteration zone + high concentration secondary halo". For example... Figure 3 As shown in the target area delineation stage (plan view of "airborne magnetic method, ground magnetic method, and surface ore body distribution"), the spatial relationship between the concealed carbonate rock body (dashed line range), alteration zone (gray halo) and surface ore body (black block) is clearly marked. The superimposed area of ​​magnetic anomaly (overlapping area of ​​positive and negative anomalies), low resistivity alteration zone (AMT inversion result), and high concentration secondary halo (soil geochemical anomaly) is the target area (area 1-3 km²), which is a high probability area for the existence of deep ore bodies.

[0095] IV. Detailed Verification (1:2,000 scale):

[0096] High-precision exploration and engineering verification were carried out within the target area to ultimately determine the location and scale of the ore body.

[0097] Method combination and data acquisition: A combination scheme of "Induced Polarization (IP) + Wide-area Electromagnetic Array (WFEM) + Rock Geochemical Profile + Three-component Magnetic Logging" was adopted.

[0098] IP method: Electrode distance 50m×20m, detection depth 300~500m, high polarizability alteration zone (η>5%) is identified by measuring polarizability, and mineralization enrichment area is delineated;

[0099] WFEM: Detects depths of 500–2000 m, inverts deep structures (such as basement undulations and fault occurrences) and concealed rock masses (carbonate rocks with velocities > 5500 m / s), providing a structural framework for locating deep ore bodies;

[0100] Rock geochemical profile: Bedrock samples were collected from the surface and deep boreholes along the tectonic zone to analyze the contents of Nb, P, REE and alteration minerals (phlogopite, chlorite, etc.) to indicate the intensity of deep mineralization.

[0101] Three-component magnetic logging: The vertical component and total field of the magnetic field are measured in the borehole. The depth of the ore body is located by identifying the enrichment zone of magnetic minerals (such as magnetite and niobite) corresponding to high anomalies (vertical component and total field anomalies).

[0102] Anomaly Analysis and Engineering Verification: Based on the anomaly results from multiple methods, verification boreholes (500-1300m deep) were arranged at the anomaly center.

[0103] The high polarizability zone (η=5%~10%) delineated by the IP method overlaps with the low resistivity anomaly zone inverted by WFEM, indicating the core range of mineralization and alteration.

[0104] Rock geochemical analysis shows that the Nb content in the anomalous area is ≥144×10⁻ 6 The results are consistent with the IP and magnetic anomaly spatial patterns, further confirming the mineralization potential.

[0105] Three-component magnetic logging data showed that significant magnetic anomalies (the vertical component and the total field anomaly values ​​deviated significantly from the background) appeared in multiple depth sections of the borehole. These anomaly sections corresponded to the enrichment of magnetic minerals, which is a direct indication of the existence of ore bodies.

[0106] like Figure 4 As shown in the figure (a simulated cross-section diagram of the fine verification stage "magnetic anomaly + WFEM low resistivity 3D inversion model + borehole verification"), the spatial relationship between the magnetic anomaly (curved fluctuations), the WFEM-inverted low resistivity (shaded area), and the borehole (straight line) is illustrated. The borehole encountered ore at the point where the low resistivity and magnetic anomaly overlapped. Core testing shows that the ore body section... >0.05%, The grade was >0.3%, reaching the industrial grade standard, which verified the correspondence between geophysical anomalies and ore bodies.

[0107] V. Integration of Results:

[0108] Based on borehole verification results and combined with a 3D geophysical and geochemical anomaly model, the orebody boundaries are delineated. Using the geological block method or kriging method, resource quantities are estimated based on parameters such as the orebody's length, thickness, and grade. By integrating data from the entire process—from regional optimization and target area delineation to detailed verification—a comprehensive report is generated, including the spatial distribution of the orebody, resource scale, and the effectiveness of exploration methods, providing a basis for subsequent mining design.

[0109] This embodiment utilizes a three-tiered exploration system of "regional optimization, target area delineation, and fine-grained verification," combined with multi-method collaboration and mineralization model constraints, to effectively improve the positioning accuracy of deep niobium-phosphate deposits. The mineralization rate in the target area is significantly higher than that of traditional methods, fully verifying the practicality and effectiveness of this method in deep mineral exploration.

[0110] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A geophysical and geochemical exploration method for locating deep niobium-phosphate deposits based on multi-method synergy, characterized in that, Includes the following steps: (1) Regional geological background analysis and metallogenic model construction: Collect geological data, remote sensing images and regional geophysical databases of the study area, analyze the distribution patterns of alkaline rock-carbonate complex, fault structures and alteration zones; combine known niobium-phosphate deposit metallogenic models to determine key prospecting indicators; (2) Regional optimization: The combined methods of airborne magnetic survey, ground high-precision magnetic survey, remote sensing structural extraction and geochemical measurement were used to process the data and delineate the composite anomaly zone of "magnetic anomaly + dense fault zone + niobium element anomaly concentration center". Combined with the regional geochemical background value, the prospective mineralization area was determined. (3) Target area delineation: A combination of airborne magnetics, audio magnetotellurics and deep soil geochemical measurements was used to process the data to construct a three-dimensional model, invert the low resistivity body and extract the main ore-forming element combination. The specific target area was locked by the four superposition anomalies of "high gravity + magnetic anomaly + low resistivity alteration zone + high concentration secondary halo". (4) Detailed verification: A combination of induced polarization method, wide-area electromagnetic method, rock geochemical profile and three-component magnetic logging method is used to identify high polarizability alteration zones, invert deep structures and concealed rock masses, indicate deep mineralization and corresponding magnetic bodies, and arrange verification boreholes for engineering verification. (5) Results integration: Based on the borehole verification results, the ore body boundary is delineated by combining the three-dimensional model of geophysical and geochemical anomalies, and the resource quantity is estimated by the geological block method or the kriging method.

2. The method according to claim 1, characterized in that, In step (1), the key mineral exploration indicators include: high-density alteration zone: density difference Δρ is 0.3 to 0.8 g / cm³; weak magnetic alteration zone: magnetic anomaly ΔT is 30 to 100 nT; high polarizability alteration zone: polarizability ηs is 5% to 10%; medium-low resistivity alteration zone: resistivity ρs is 20 to 100 Ω·m; and enrichment areas of niobium, phosphorus, nickel, titanium, tantalum, rare earth elements, thorium, and uranium.

3. The method according to claim 1, characterized in that, In step (2), the scale of the airborne magnetic survey is 1:200,000, the scale of the ground high-precision magnetic survey is 1:50,000, the remote sensing structure extraction utilizes remote sensing data and digital elevation data, and the scale of the geochemical measurement is 1:25,000; the data processing includes: calculating the residual gravity anomaly after topographic correction and Bouguer correction of gravity data: Δg_residual > ; Magnetic data calculation of total magnetic anomaly: T_residual > 10 nT; Remote sensing extraction of areas with fracture density > 0.5 fractures / km², and geochemical measurements extraction of anomalies with niobium as the main element.

4. The method according to claim 3, characterized in that, In step (2), the geochemical measurements collect stream sediments, taking into account soil and rock debris, with a point density of 20 points / square kilometer. The analyzed elements include: gold, arsenic, antimony, mercury, silver, copper, lead, zinc, tungsten, tin, molybdenum, bismuth, cobalt, chromium, nickel, lithium, beryllium, uranium, niobium, yttrium, lanthanum, zirconium, and fluorine; the anomaly with niobium as the main element has a niobium anomaly ≥ The regional geochemical background values ​​include phosphorus pentoxide > 0.1% and total rare earth elements > .

5. The method according to claim 1, characterized in that, In step (3), the aeromagnetic grid is 100m × 20m and extends upwards by 400m, and the frequency range of the audio magnetotelluric method is 10⁻ 4 ~10 4 The detection depth is 500-1000m, and the sampling depth of the deep soil geochemical measurement is 0.3-2m with a point spacing of 10m. The data processing includes the joint inversion of magnetic data to construct a three-dimensional magnetic model, the inversion of low resistivity body (resistivity <100Ω·m) from audio magnetotelluric data, and the extraction of main ore-forming element combinations from soil data using multivariate statistical analysis.

6. The method according to claim 5, characterized in that, In step (3), the three-dimensional magnetic model is used to identify the boundaries of concealed rock masses, the main ore-forming element assemblage includes niobium-phosphorus-rare earth elements-thorium, and the peak value of the secondary halo anomaly is niobium > 50 × 10⁻ 6 Phosphorus pentoxide > 0.3%.

7. The method according to claim 1, characterized in that, In step (4), the electrode spacing of the induced polarization method is 50m×20m, and the detection depth is 300-500m; the detection depth of the wide-area electromagnetic method is 500-2000m; the rock geochemical profile includes bedrock samples collected from the surface and deep boreholes, and the analyzed elements include niobium, phosphorus, rare earth elements and alteration mineral content; the three-component magnetic logging measures the vertical component and the total field.

8. The method according to claim 7, characterized in that, In step (4), the induced polarization method is used to identify high polarizability alteration zones: the polarizability η is 5% to 10%; the deep structure inverted by the wide-area electromagnetic method includes basement undulations, fault occurrence, and the concealed rock mass is a carbonate rock mass with a velocity > 5500 m / s; the high anomalies of the vertical component and the total field in the three-component magnetic logging correspond to the magnetic body.

9. The method according to claim 1, characterized in that, In step (4), the verification borehole is 500-1300m deep, and the geophysical model is verified by core physical property testing. The core physical properties include density, magnetic susceptibility, resistivity and polarizability. Sampling analysis is used to determine the grade of the ore body. The grade includes niobium pentoxide > 0.05% and phosphorus pentoxide > 0.3%.

10. The method according to any one of claims 1 to 9, characterized in that, Each step incorporates constraints from an alkaline rock-niobium-phosphate mineralization model. These constraints include the selection of methods and anomaly interpretation based on the mineralization regularity of alkaline rock-niobium-phosphate deposits. The mineralization regularity includes the characteristics of "alkaline magmatic activity - tectonic ore control - hydrothermal alteration enrichment".

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