A combined method of CSAMT and transient electromagnetic method for concealed copper-gold deposit exploration

Abstract

The present application relates to the field of quantum magnetic field measurement, and discloses a CSAMT and transient electromagnetic combined detection method for concealed copper-gold mine exploration, comprising the following steps: establishing a survey area coordinate system and arranging comprehensive geophysical survey lines in the survey area; sending alternating current by using the controllable source audio frequency magnetotelluric method along the survey line, and combining a quantum geomagnetic field strength meter to obtain the earth's electromagnetic response data; sending pulse current by using the equivalent counter magnetic flux transient electromagnetic method, and placing a quantum magnetometer on the zero magnetic flux plane of the primary field to obtain the stratum pure secondary field transient decay signal; inputting the data into a noise reduction system, and extracting the noise-reduced data by using an adaptive common-mode noise suppression algorithm; performing inversion processing on the noise-reduced data to obtain a two-dimensional resistivity section and delineate the concealed ore body. The present application overcomes the delay of the traditional induction coil, captures deep and extremely weak signals with high precision, and strips strong interference at the physical and algorithm levels, thereby improving the inversion reliability and ore body positioning accuracy.

Description

Technical Field

[0001] This invention relates to the field of quantum magnetic field measurement technology, specifically to a CSAMT and transient electromagnetic joint detection method for the exploration of concealed copper-gold deposits. Background Technology

[0002] The exploration of concealed copper-gold deposits typically faces the objective conditions of deep burial depth and weak electrical differences in the surrounding rocks. Geophysical electromagnetic methods are commonly used to explore deep metallic mineral deposits, among which controlled-source audio-frequency magnetotellurics (CSAMT) and transient electromagnetic methods are used to obtain deep structural information and shallow-to-medium-level structural characteristics, respectively.

[0003] In existing electromagnetic exploration technologies, the receiving end commonly uses traditional induction coils based on Faraday's law of electromagnetic induction as sensors. These sensors actually measure the time derivative of the secondary magnetic field. During the pulse-off period of the transient electromagnetic method, the differential receiving mechanism generates a delay in the induced electromotive force and waveform broadening, creating an early detection blind zone. This makes it difficult for the equipment to capture the pure secondary field transient signal excited by the formation at time zero. In the extremely low-frequency band of the CSAMT method, the induced electromotive force of traditional induction rods attenuates as the frequency decreases, making it difficult to effectively extract the weak secondary electromagnetic response conducted from deep ore bodies to the surface.

[0004] On the other hand, the exploration area often has high-voltage power grids and industrial facilities on the surface, generating strong environmental electromagnetic interference. Conventional data processing often uses bandpass filtering or notch filtering techniques to remove power frequency interference, but in the process of pure digital filtering, it is easy to cause phase distortion and energy loss of effective low-frequency geological signals. Under the cover of strong background noise, conventional noise reduction methods are difficult to accurately restore weak signals at depth.

[0005] Furthermore, due to limitations in detection depth and resolution of single electromagnetic methods, it is usually necessary to combine broadband electromagnetic data with transient electromagnetic data. However, due to the physical receiving limitations of traditional sensors and environmental noise interference, the overall signal-to-noise ratio of the observed data is low. In subsequent inversion processing, local electrical inhomogeneities near the surface can easily cause static shifts in the apparent resistivity curve, which increases the fitting error of the joint inversion. The combination of these factors results in a bias in the final output resistivity model, making it difficult to provide accurate spatial coordinate parameters to delineate the boundaries and burial depth of concealed ore bodies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a combined CSAMT and transient electromagnetic detection method for the exploration of concealed copper-gold deposits. This method solves the problem that existing electromagnetic exploration technologies are limited by the physical reception delay of traditional sensors and strong electromagnetic noise interference on the surface, making it difficult to effectively extract weak response signals from deep depths and accurately locate concealed ore bodies.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a CSAMT and transient electromagnetic joint detection method for the exploration of concealed copper-gold deposits, comprising the following operations: A coordinate system for the survey area is established using real-time dynamic positioning technology, and a comprehensive geophysical survey line is laid out within the survey area; Along the aforementioned integrated geophysical exploration line, an alternating current is transmitted underground using the controlled-source audio-frequency magnetotelluric method, and mutually orthogonal electrode dipoles are deployed at the receiving end to synchronously extract the horizontal electric field signal. At the same time, a quantum geomagnetic field strength meter is used to measure the magnetic field and obtain magnetotelluric response data containing electric and magnetic field components. Along the aforementioned geophysical exploration line, the equivalent anti-magnetic flux transient electromagnetic method is used to send bipolar pulse currents underground through dual transmitting coils arranged in parallel and coaxial configurations. At the receiving end, a quantum magnetometer is placed on the primary field zero flux plane generated at the center of symmetry of the dual transmitting coils to perform geomagnetic measurements and obtain the transient decay signal of the pure secondary field of the stratum. The acquired magnetotelluric response data and the transient attenuation signal of the pure secondary field of the stratum are input into the noise reduction system. The adaptive common-mode noise suppression algorithm is used to filter out power frequency and environmental electromagnetic interference, and the noise-reduced broadband electromagnetic data and transient electromagnetic data are extracted. The denoised broadband electromagnetic data and the transient electromagnetic data are inverted to obtain a two-dimensional resistivity profile reflecting the electrical structure of the strata, and the spatial distribution and burial depth range of the concealed copper-gold deposits are delineated based on the two-dimensional resistivity profile.

[0008] Furthermore, when using a quantum geomagnetic field strength meter to measure the magnetic field, the quantum geomagnetic field strength meter is equipped with a diamond NV color center sensor. When acquiring the magnetotelluric response data, it utilizes the electron spin magnetic resonance effect under microwave excitation to perform broadband absolute measurement of the weak electromagnetic signals transmitted from the concealed copper-gold ore body to the surface in the orthogonal horizontal direction.

[0009] The innovative principle of this invention lies in utilizing the electron spin level splitting characteristics of nitrogen-vacancy (NV) defects in diamond for quantum sensing of weak magnetic fields. Under the influence of an applied weak secondary geological magnetic field, the ground-state spin level of the NV color center splits due to the Zeeman effect. The spin resonance frequency is then determined through frequency sweeping excitation using photodetector magnetic resonance technology. The following physical relationship must be satisfied: In the formula, The zero-field splitting constant without an external magnetic field is approximately [value missing]. ; The gyromagnetic ratio of the electron is approximately [value missing]. ; This refers to the weak geomagnetic field response component generated in the deep strata under test along the NV color center axis. By monitoring the frequency shift of the minimum point of fluorescence intensity in real time, absolute quantitative measurement of the changes in the extremely weak magnetic field in deep strata can be achieved, overcoming the physical sensitivity limitations of traditional induction magnets.

[0010] Furthermore, when transmitting alternating current underground using the controlled-source audio-frequency magnetotelluric method, power-supplying transmitters are deployed along the integrated geophysical exploration line. The length of the transmitter-to-receiver distance is controlled to be less than one-third of the transmitter-to-receiver distance, and the alternating current with a frequency range of 7680 Hz to 1.2 Hz is transmitted underground using a multiple superposition technique. At the receiving end, horizontal electric field signals are synchronously extracted using mutually orthogonal electrode dipoles deployed on the surface, and combined with magnetotelluric response data obtained from a quantum geomagnetic field strength meter; based on the electromagnetic plane wave propagation theory, the apparent resistivity of the shallow, medium, and deep Carnia layers is calculated. The calculation formula is: In the formula, The controllable source transmission frequency (in Hertz, Hz) is set as described above. The amplitudes of the horizontal components of the mutually orthogonal electric fields on the ground (unit: millivolts per kilometer, mV / km). The amplitude of the horizontal component of the magnetic field (in nanotesla, nT) is accurately measured by the quantum geomagnetic field meter. The high signal-to-noise ratio of the magnetic field component data effectively improves the noise resistance of apparent resistivity calculations.

[0011] Furthermore, when transmitting bipolar pulsed currents underground using the equivalent anti-magnetic flux transient electromagnetic method, pulsed currents of equal magnitude and opposite direction are synchronously injected into two parallel and coaxially arranged transmitting coils. This creates a geometric surface at the center of symmetry of the two coils where the primary transient magnetic fields cancel each other out. The quantum magnetometer is placed on the primary field zero-flux plane at the transmission current cut-off gap to eliminate interference from the primary field induced electromotive force. At least two hundred superimposed measurements are used to capture high-precision transient attenuation responses in shallow, medium, and deep formations, obtaining complete pure secondary field transient attenuation signals from the formation. The magnetic field detection sensitivity of the quantum magnetometer placed on the primary field zero-flux plane is adjusted to the picotesla to femtotes level to extract extremely weak electromagnetic anomaly signals generated by deep, concealed copper-gold ore bodies with high precision. This setting references the extremely weak magnetic field detection threshold at the biomagnetism measurement level, overcoming the technical obstacle of effectively extracting the secondary electromagnetic response of deep ore bodies, which decays exponentially with depth.

[0012] Furthermore, the adaptive common-mode noise suppression algorithm is applied to the magnetotelluric response data and the transient attenuation signal of the pure secondary field in the strata using the noise reduction system. A reference magnetic field detection base station is set up in the electromagnetic interference-free area at the far end of the comprehensive geophysical survey line. By dynamically differentially comparing the raw data from the main measuring station on the survey line with the data from the reference magnetic field detection base station, gradient noise reduction of the far-field ionized stray magnetic field is achieved, filtering out strong environmental electromagnetic interference caused by the superposition of shallow high-voltage power lines and underground ionizing currents in the survey area. The calculation formula for its spatial gradient differential noise reduction is: In the formula, The noise-reduced electromagnetic signal extracted after filtering out power frequency interference; The original mixed magnetic field, including environmental background noise, was collected by the main measuring station along the measuring line; For the first Environmental ionizing electromagnetic interference signals were synchronously captured by a remote reference magnetic field detection base station; This is the adaptive weighting coefficient matrix calculated by the system based on real-time feedback of the environmental electromagnetic noise waveform.

[0013] Furthermore, when performing inversion processing on the denoised broadband electromagnetic data and the transient electromagnetic data, the apparent resistivity curve features of the denoised broadband electromagnetic data are extracted. In response to the static shift phenomenon caused by the upward or downward translation of the curve due to local electrical inhomogeneities near the surface, the data is statically corrected based on the surface resistivity distribution characteristics of the exploration area to establish an initial geoelectric model with topographic undulation information.

[0014] Furthermore, establishing an initial geoelectric model with topographic relief information for two-dimensional constrained inversion specifically includes: adopting the method of inversion fitting apparent resistivity and phase hyperbolic curves, combining statically corrected broadband electromagnetic data with transient electromagnetic data in the depth domain, performing iterative convergence calculations through a two-dimensional smooth model algorithm, and outputting a high-resolution two-dimensional resistivity profile.

[0015] Furthermore, based on the known electrical difference model between the concealed copper-gold ore body and its surrounding strata, relatively high-resistivity or low-resistivity anomaly zones reflecting the macroscopic outline of the deep strata are extracted from the two-dimensional resistivity cross-section. Combined with the structural features of local subtle anomalies in the shallow and middle layers obtained by transient electromagnetic method, the two-dimensional planar boundary of the concealed copper-gold ore body and the depth parameters of the top and bottom plates of the ore body are comprehensively delineated.

[0016] This invention provides a combined CSAMT and transient electromagnetic detection method for the exploration of concealed copper-gold deposits. It offers the following advantages: 1. To address the problem of extremely weak signals and transient electromagnetic shut-off blind zones in deep ore bodies, this invention introduces a diamond NV color center quantum magnetometer into the primary field zero flux plane. This solution effectively avoids the physical delay of traditional induction coils, capturing pure secondary field signals from deep within with high precision at the femtotes level, significantly improving the equipment's ability to detect weak anomalous fields in concealed deep ore bodies.

[0017] 2. To address the challenge of strong electromagnetic interference from high-voltage power grids and other sources in the survey area overwhelming effective signals, this invention deploys a spatial gradient differential noise reduction mechanism. Through a remote reference base station and an adaptive common-mode suppression algorithm, power frequency and ionization interference are effectively separated at both physical and algorithmic levels. This results in a high signal-to-noise ratio for restoring the deep low-frequency response, significantly improving the reliability of the joint inversion and the accuracy of ore body positioning. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention. Figure 2 This is a schematic diagram of the integrated geophysical observation system and the spatial layout of the survey lines of the present invention; Figure 3 This is a schematic cross-sectional view of the equivalent anti-magnetic flux dual-emitting coil and the planar geometric structure of the primary field zero magnetic flux of the present invention; Figure 4 This is a block diagram of the structure or optical detection magnetic resonance principle of the quantum geomagnetic field strength meter based on diamond NV color centers of the present invention. Figure 5 This is a block diagram illustrating the principle of the space physics noise reduction mechanism and adaptive common-mode noise suppression system of the present invention. Figure 6 This is a schematic diagram illustrating the interpretation of the two-dimensional resistivity profile and the delineation of concealed ore bodies generated by the joint inversion of this invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0020] Please see the appendix Figure 1 -Appendix Figure 6 This invention provides a CSAMT and transient electromagnetic joint detection method for the exploration of concealed copper-gold deposits, comprising the following steps: A coordinate system for the survey area was established using real-time dynamic positioning technology, and a comprehensive geophysical survey line was laid out within the survey area.

[0021] Along the aforementioned integrated geophysical exploration line, an alternating current is transmitted underground using the controlled-source audio-frequency magnetotelluric method. At the receiving end, mutually orthogonal electrode dipoles are deployed to synchronously extract the horizontal electric field signal. Simultaneously, a quantum geomagnetic field strength meter is used to measure the magnetic field, thereby obtaining magnetotelluric response data containing both electric and magnetic field components.

[0022] Along the aforementioned geophysical exploration line, a bipolar pulse current is transmitted underground through a dual-transmitting coil arranged in parallel and coaxial configuration using the equivalent anti-magnetic flux transient electromagnetic method. At the receiving end, a quantum magnetometer is placed on the primary field zero flux plane generated at the center of symmetry of the dual-transmitting coil to perform geomagnetic measurements and obtain the transient decay signal of the pure secondary field of the stratum.

[0023] The acquired magnetotelluric response data and the transient attenuation signal of the pure secondary field of the stratum are input into the noise reduction system. The adaptive common-mode noise suppression algorithm is used to filter out power frequency and environmental electromagnetic interference, and the noise-reduced broadband electromagnetic data and transient electromagnetic data are extracted.

[0024] The denoised broadband electromagnetic data and the transient electromagnetic data are inverted to obtain a two-dimensional resistivity profile reflecting the electrical structure of the strata, and the spatial distribution and burial depth range of the concealed copper-gold deposits are delineated based on the two-dimensional resistivity profile.

[0025] The exploration of concealed copper-gold deposits faces multiple physical constraints, including deep burial depths, weak electrical differences in surrounding rocks, and strong electromagnetic interference from surface human activities. Conventional induction coil-based electromagnetic exploration receivers experience severe signal-to-noise ratio degradation in strong electromagnetic environments, making it difficult to penetrate shallow overburden layers and obtain deep mineralization information. This invention's exploration process begins with establishing a high-precision spatial physical benchmark. Through calibration using topographic features and known geological structures, it provides rigorous coordinate constraints for subsequent joint data inversion.

[0026] In the data acquisition phase, the system employs a mechanism of coordinated frequency and time domain detection. Frequency domain detection relies on controlled-source audio-frequency magnetotellurics (CSAMT) to provide large-scale macroscopic control of deep rock structures. At the receiving end, a quantum magnetometer replaces the traditional high-frequency magnetic rod to directly extract extremely weak alternating magnetic fields in space. During this process, the apparent resistivity of the Carnia system is acquired. The physical calculation relationship satisfies: In the formula, The excitation frequency (in Hertz, Hz) for transmitting underground alternating current from a controllable source. The amplitude of the horizontal electric field component extracted from electrodes laid out on the ground parallel to the survey line (unit: millivolts per kilometer, mV / km). This refers to the amplitude (in nanotesla, nT) of the horizontal magnetic field component perpendicular to the measurement line, precisely obtained by the quantum geomagnetic field strength meter. The quantum detector provides high fidelity... The data, from the source, ensures the apparent resistivity. The reliability of the calculation results. Simultaneously, based on the extracted electric and magnetic field components, the system obtains the phase information of the magnetotelluric response through impedance complex calculations, including its impedance phase. The calculation formula satisfies: This provides complete impedance phase parameters for subsequent inversion processing.

[0027] The time-domain probing relies on the equivalent anti-magnetic flux transient electromagnetic method to provide a keen characterization of the fine geological structure of shallow and medium-depth formations. The system captures the transient decay voltage sequence of the formation during the cut-off gap by geometrically constructing a primary field zero-flux plane and utilizing the broadband transient response characteristics of a quantum magnetometer. The time-frequency and time-domain data volumes do not interfere with each other at the acquisition end, achieving blind zone complementarity at the physical probing level.

[0028] During the data processing and noise reduction stage, considering that the free currents generated by shallow high-voltage power grids and industrial facilities will form broadband background noise, the noise reduction system receives the mixed magnetic field time series collected by the front end and simultaneously filters out power frequency harmonic interference in both physical and algorithmic dimensions. The purified broadband electromagnetic data and transient electromagnetic data are then transformed into noise-reduced apparent resistivity curves.

[0029] In the final inversion processing stage, the system performs static translation correction on the denoised data stream to eliminate curve distortion caused by local electrical inhomogeneities near the surface. Based on the initial geoelectric model constrained by topographic relief, a two-dimensional smooth iterative convergence is performed. The output two-dimensional resistivity profile accurately reflects the electrical anomaly gradient zone caused by underground concealed sulfides or alteration zones, thus providing rigorous data support for delineating the three-dimensional target area of ​​concealed copper-gold deposits and for drilling verification.

[0030] In this embodiment, the precise spatial layout of the geodetic work and observation system is the geological and physical foundation for ensuring the fidelity of subsequent quantum electromagnetic joint detection data. This invention employs rigorous coordinate constraints and a physical avoidance strategy based on the attenuation law of electromagnetic fields to establish a pristine observation environment for capturing weak deep-seated anomalies.

[0031] In this embodiment, real-time dynamic positioning technology is used to establish an independent high-precision coordinate system for the exploration area. Based on the strike of the concealed ore-controlling structure analyzed from existing geological data, multiple comprehensive geophysical exploration lines are laid out parallel to the strike of the main structure within the exploration area. On each comprehensive geophysical exploration line, physical points are laid out one by one and their three-dimensional coordinates are calibrated according to the set point spacing to ensure the absolute accuracy of the geometric position of the subsequent two-dimensional or three-dimensional inversion spatial grid subdivision.

[0032] In the observation system deployment phase, the system first conducts a survey and physical calibration of shallow, strong electromagnetic interference sources within and around the survey area. For typical human-caused interference sources such as high-voltage power grids and heavy industrial facilities, a differential deployment mechanism is adopted between the transmitting source and the receiving base station. The power supply transmitter is deployed using a long, grounded parallel conductor, and the position of the transmitter must strictly adhere to the far-field plane wave observation conditions of the controlled-source audio-frequency magnetotelluric method.

[0033] The transmit / receive distance is controlled by the skin effect of electromagnetic waves in the underground medium within the detection frequency band. The skin depth at which electromagnetic waves propagate downwards is also a factor. The physical calculation formula satisfies: In the formula, The average apparent resistivity of the surrounding rock in the underground semi-space of the exploration area; Let be the angular frequency of the emitted electromagnetic wave, and satisfy . , The frequency of the alternating current injected into the ground by the emitter; ρ is the vacuum permeability. To ensure that all receiving measurement points are within the far-field radiation range, the vertical transmit / receive distance between the transmitter and the synthetic object detection line is set to a multiple limit greater than the maximum skin depth corresponding to the lowest transmit frequency, thereby ensuring that the electromagnetic waves entering the receiving area satisfy the horizontal propagation plane wave assumption.

[0034] At the receiving end, the observation system employs a configuration of mobile main measuring stations and fixed reference base stations. Along the established geophysical survey line, main measuring stations equipped with quantum geomagnetic field strength meters and quantum magnetometers are deployed point-by-point to collect data. Simultaneously, reference magnetic field detection base stations are permanently deployed outside the survey area, away from known high-voltage power lines and surface industrial ionized current networks.

[0035] The spatial deployment location of reference magnetic field detection base stations must meet specific electromagnetic isolation physical conditions. The power frequency magnetic field interference intensity generated by long-distance, high-voltage transmission networks... Vertical distance in space The attenuation follows a derived form of Ampere's circuital law: In the formula, This refers to the instantaneous value of the power frequency equivalent current generated in the high-voltage transmission network; The system uses the vertical spatial distance from the reference magnetic field detection base station to the axis of the high-voltage transmission network as a reference. Based on this attenuation model, the system determines the deployment distance of the reference magnetic field detection base station. Strictly configured within the power frequency magnetic field interference intensity Spatial locations attenuated to levels below the ambient white noise level.

[0036] Through the aforementioned deployment mechanism, the main measuring station is positioned above the target area to simultaneously capture the formation response and environmental noise, while the remote reference base station extracts the clean regional background noise. This collaborative deployment of main and auxiliary stations based on the spatial distribution of electromagnetic fields provides comprehensive physical hardware architecture support for subsequent extraction of high-precision broadband and transient data using quantum sensors, as well as the implementation of common-mode noise suppression algorithms.

[0037] In this embodiment, broadband detection based on quantum magnetic field sensing aims to acquire high-fidelity macroscopic electrical structures of deep strata. The system transmits alternating current underground using controlled-source audio-frequency magnetotellurics (AETG) along a deployed geophysical survey line. At the transmitting end, the physical length of the power supply and transmitting electrode distance is strictly controlled to be less than one-third of the transmit / receive distance, ensuring that the data acquisition area is entirely within the far-field range satisfying the plane wave approximation assumption. The transmitting system, combined with multiple superposition techniques, sequentially transmits alternating frequency-varying currents with a frequency range set from 7680 Hz to 1.2 Hz into the underground medium, achieving continuous electromagnetic imaging from the shallow overburden layer to the deep bedrock structure.

[0038] This invention abandons the traditional induction coil based on the Faraday electromagnetic induction principle in the broadband electromagnetic response receiving stage, and instead uses a quantum geomagnetic field strength meter equipped with a diamond NV color center sensor to perform high-precision magnetic field measurements. This receiving system utilizes the inherent electron spin characteristics of nitrogen-vacancy defects within diamond crystals, and through a photodetector magnetic resonance mechanism, achieves broadband absolute measurement of weak electromagnetic signals transmitted from concealed ore bodies to the Earth's surface.

[0039] During the continuous acquisition of magnetotelluric response data by the quantum geomagnetic field meter, a weak secondary alternating magnetic field generated by geological structures acts on the sensor, causing the ground-state spin energy level of the NV color center to split due to the Zeeman effect. The quantum geomagnetic field meter integrates a laser emission module (such as a 532nm green laser) and a photodetector (such as an avalanche photodiode) for initializing the color center spin state. The system applies continuous microwave frequency sweep excitation and uses the photodetector to monitor the number of fluorescence emission photons in real time, as well as the frequency at which the electron spin resonates. The physical relationship satisfies: In the formula, The zero-field splitting constant of the NV color center under conditions without an external magnetic field; is the gyromagnetic ratio constant of electrons; The absolute component of the magnetic field response generated by the weak alternating electromagnetic field in the deep stratum to be measured along the specific quantized crystal axis of the NV color center is given.

[0040] The system directly converts the physical scalar of the spatially alternating magnetic field strength into a precise reading of the microwave frequency shift by tracking the frequency shift corresponding to the minimum point of fluorescence intensity depression in the optically detected magnetic resonance spectrum. This measurement mechanism, based on quantum spin level splitting, is completely independent of the frequency response, fundamentally eliminating the receiving bottleneck caused by the attenuation of induced electromotive force in extremely low frequency bands such as 1.2 Hz using traditional magnetic rods, and maintaining a flat and consistent extremely high sensitivity throughout the entire frequency sweep range.

[0041] In the specific data acquisition process, the main measuring station incorporates diamond NV color center sensing units arranged in an orthogonal matrix, which, in conjunction with orthogonal electrodes deployed on the ground, extracts horizontal electric field signals and horizontal broadband magnetic field response data perpendicular to the survey line direction in real time and synchronously. This direct extraction method of absolute magnetic field strength avoids the phase delay and waveform distortion caused by the integrating circuit in traditional equipment, truly restoring the original magnetotelluric response characteristics excited by underground sulfide highly polarized geological bodies, and providing a high-quality data foundation for the accurate tracing of deep-seated concealed copper-gold deposits.

[0042] In this embodiment, to meet the high-resolution detection requirements of fine geological structures in shallow, medium, and deep layers, the system performs quantum transient electromagnetic detection based on the zero-flux plane along the comprehensive geophysical detection line. To overcome the shallow detection blind zone caused by the primary field shutdown in conventional transient electromagnetic methods, the transmitting end employs an equivalent anti-flux transient electromagnetic loop device to send bipolar pulse currents with a fundamental frequency set to 12.5Hz or 25Hz and a duty cycle of 50% to the underground. This transmitting device consists of two parallel coaxially arranged transmitting coils, and the system synchronously injects pulse currents of equal magnitude and opposite direction into the two sets of coils.

[0043] During the off-state gap of the excited bipolar pulse current, the system uses physical ranging at the receiving end via the geometric symmetry center of the transmitting coil, or optimizes the primary field induction reading by utilizing high-frequency real-time feedback monitoring to achieve a minimum value, precisely placing the quantum magnetometer on the primary field zero flux plane for geomagnetic measurement. On the geometric symmetry center plane of the aforementioned dual transmitting coils, the primary transient magnetic field vectors generated by the upper and lower coils cancel each other out in the vertical direction. Let the vertical magnetic induction intensity component generated by the upper coil be... The vertical magnetic flux density component generated by the lower coil is The vertical component of the total first field at any position within the plane of symmetry satisfy: This geometric plane is the physical zero-flux plane of the primary field. Placing the quantum magnetometer at this location cuts off the saturation impact of the strong primary field induced electromotive force on the receiving system at the source of electromagnetic field radiation, creating a pure spatial environment for capturing the transient attenuation signal of the pure secondary field of the stratum without blind spots.

[0044] In this invention, a quantum magnetometer arranged on a zero flux plane directly extracts the absolute magnetic field strength scalar of the underground medium. Conventional induction coils, following Faraday's law of electromagnetic induction, actually extract the time derivative of the secondary magnetic field, which is the secondary magnetic field strength. Electromotive force measured by traditional induction coil The physical relationship between them satisfies: In the formula, This refers to the number of turns of a traditional receiving coil; This is the effective equivalent cross-sectional area of ​​a single-turn receiving coil; This is the time delay after the emitter bipolar pulse current is turned off. Differential operation characteristics. Traditional coils suffer from severe bandwidth limitations and waveform broadening delays at the moment of current cutoff. This can be addressed by introducing a quantum sensing mechanism to directly obtain... The system avoids early signal distortion caused by differential reception, enabling exploration equipment to track the complete transient electromagnetic response excited by underground anomalies at the zero moment of pulse shutdown.

[0045] To address the physical characteristic of deep, concealed copper-gold ore bodies where the secondary electromagnetic response decays exponentially due to their great depth, the system employs a cross-disciplinary, high-sensitivity parameter configuration. The magnetic field detection sensitivity of the quantum magnetometer placed on the primary field zero-flux plane is rigorously adjusted to the picotesla to femtotes level. This sensitivity threshold directly corresponds to the stringent biomagnetic measurement level, endowing geological exploration equipment with the ability to detect extremely weak deep-seated anomalous fields.

[0046] During the acquisition and execution of single-point data, to further ensure the reliability of weak signals, the system employs a superposition measurement mechanism of no less than two hundred times within the transmission cycle. Repeated sampling via multiple pulse excitations accumulates the weak, effective signals in phase over the time domain, synchronously suppressing random Gaussian white noise in the environment. Ultimately, this captures high-precision transient attenuation responses from shallow, medium, and deep formations, obtaining continuous and complete pure secondary field transient attenuation signals with a high signal-to-noise ratio.

[0047] In this embodiment, addressing the extremely weak response signals of deep, concealed copper-gold deposits, which are easily submerged by strong electromagnetic background noise in the mining area, the system simultaneously inputs the magnetotelluric response data acquired at the front end and the transient attenuation signal of the pure secondary field of the formation into the noise reduction system for signal purification and extraction. Conventional bandpass filtering or notch filtering often causes phase distortion and energy loss of effective low-frequency geological signals when eliminating power frequency interference. This invention abandons the traditional pure digital filtering strategy and introduces a space-physical noise reduction mechanism at the biomagnetic measurement level in the signal extraction stage.

[0048] In this invention, the system utilizes an adaptive common-mode noise suppression algorithm built into the quantum geomagnetic field strength meter to process magnetotelluric response data mixed with complex environmental noise and transient attenuation signals of pure secondary fields in the strata. Based on the aforementioned observation system deployment architecture, a reference magnetic field detection base station is set up in a physically isolated area free from electromagnetic interference at the far end of the integrated geophysical survey line. By dynamically differentially comparing the raw data time series acquired by the main measuring station on the survey line with the background ionized data synchronously captured by the reference magnetic field detection base station, strong environmental electromagnetic interference caused by the superposition of shallow high-voltage power lines and underground ionized currents in the survey area is directly filtered out at the spatial physical gradient level.

[0049] The aforementioned spatial gradient difference denoising mechanism is based on the high spatial coherence of electromagnetic noise between the far and near environmental regions, and the physical and mathematical calculation formulas for its core extraction process satisfy: In the formula, This is the time series of broadband electromagnetic data and transient electromagnetic data after noise reduction, extracted after differential filtering to remove power frequency and ionization current interference. The original mixed magnetic field sequence, which includes effective mineralized geological response and environmental background noise, was collected in real time by the main survey station on the comprehensive geophysical exploration line. This refers to the number of remote reference magnetic field detection base stations operating synchronously in the system. For the first Pure environmental ionizing electromagnetic interference signals synchronously captured by a remote reference magnetic field detection base station; The adaptive weighting coefficients are calculated in real time based on the coherence characteristics of the environmental electromagnetic noise waveform by the noise reduction system.

[0050] When executing the adaptive common-mode noise suppression algorithm, the system dynamically updates the adaptive weight coefficients based on the noise covariance matrix received by the reference base station and the main measurement station, using standard adaptive filtering mechanisms such as the least mean square error algorithm (LMS) or the recursive least squares algorithm (RLS). This weighting coefficient accurately characterizes the spatial attenuation and phase delay transfer function of far-end ionized noise as it propagates to the main station location. Through this strategy combining physical isolation sampling with adaptive algorithmic tracking, the system can accurately reconstruct and remove the interference baseline at the main station location.

[0051] Ultimately, the noise reduction system extracts high-fidelity, noise-reduced broadband electromagnetic data and transient electromagnetic data without compromising the true physical properties of the amplitude and phase of the secondary response signal of the target geological body. This step fundamentally solves the problem of extracting weak signals from deep within areas with strong human interference, ensuring the integrity of information on concealed mineral-induced anomalies.

[0052] In this embodiment, performing high-precision joint inversion in the depth domain on the acquired denoised data is a crucial step in transforming surface observation physical quantities into subsurface electrical structure profiles and achieving target area localization. The system first extracts the apparent resistivity curve features from the denoised broadband electromagnetic data. Due to electromagnetic distortion caused by local electrical inhomogeneities and topographic undulations near the surface of the survey area, the apparent resistivity curve is prone to overall upward or downward parallel shifts, i.e., static offset. To address this phenomenon, the system performs static translation correction on the data based on the spatial distribution characteristics of the actual surface resistivity of the survey area, removing spurious anomalies caused by shallow electrical inhomogeneities, and combining this with high-precision coordinate data of the survey area to establish an initial geoelectric model with accurate topographic undulation information.

[0053] In this invention, to achieve seamless integration from shallow to deep geoelectric data, the system employs an inversion fitting method of apparent resistivity and phase hyperbolic curves, combining statically corrected broadband electromagnetic data with transient electromagnetic data within a unified depth domain. The system performs iterative convergence calculations on the initial geoelectric model using a two-dimensional smoothed model algorithm. During the inversion calculation process, a regularized objective functional is constructed. Satisfy the following mathematical relationship: In the formula, The objective functional is used for inversion and iterative optimization; This is the vector of broadband electromagnetic and transient electromagnetic joint observation data output by the front-end system; This is the theoretical electromagnetic response operator obtained by forward modeling the current geoelectric model; The parameterized resistivity vector of the two-dimensional geoelectric model to be solved; For dynamically adjusted regularization balance coefficients; is the roughness matrix operator in the model space, used to apply spatial constraints to obtain smooth physical property boundaries.

[0054] The system drives iterative updates of model parameters until the fitting residuals converge by solving for the nonlinear minimum of the aforementioned objective functional, ultimately outputting a high-resolution two-dimensional resistivity profile. This physical profile, within a unified depth coordinate system, organically integrates the deep transmission resolution of deep macroscopic structures obtained by controlled-source audio-frequency magnetotellurics (AETMT) with the characteristics of shallow to intermediate geological microstructures acquired by transient electromagnetic methods, thus realistically reconstructing the continuous electrical sequence distribution from shallow to deep subsurface.

[0055] Based on the known intrinsic electrical difference model between concealed copper-gold ore bodies and their surrounding strata, the system performs quantitative structural analysis on the two-dimensional resistivity profile. Sulfide-rich copper-gold ore bodies exhibit corresponding low-resistivity anomaly zones on the electrical profile, while their associated silicification alteration zones show relatively high resistivity. The system extracts relatively high- or low-resistivity anomaly zones reflecting the macroscopic outline of the deep strata from the two-dimensional resistivity profile, and combines this with the structural features of local subtle anomalies in the shallow to medium layers obtained by transient electromagnetic methods (i.e., local high-frequency gradient anomalies on the profile) to comprehensively delineate the morphological characteristics of structural development. By locking the spatial abrupt change interface of the dense resistivity contour gradient, the system directly delineates the two-dimensional planar boundary of the concealed copper-gold ore body and precisely defines the depth parameters of the top and bottom plates of the ore body, providing a rigorous spatial coordinate target area for subsequent geological drilling verification.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A combined CSAMT and transient electromagnetic detection method for the exploration of concealed copper-gold deposits, characterized in that, Includes the following steps: A coordinate system for the survey area is established using real-time dynamic positioning technology, and a comprehensive geophysical survey line is laid out within the survey area; Along the aforementioned integrated geophysical exploration line, an alternating current is transmitted underground using the controlled-source audio-frequency magnetotelluric method, and mutually orthogonal electrode dipoles are deployed at the receiving end to synchronously extract the horizontal electric field signal. At the same time, a quantum geomagnetic field strength meter is used to measure the magnetic field and obtain magnetotelluric response data containing electric and magnetic field components. Along the aforementioned geophysical exploration line, the equivalent anti-magnetic flux transient electromagnetic method is used to send bipolar pulse currents underground through dual transmitting coils arranged in parallel and coaxial configurations. At the receiving end, a quantum magnetometer is placed on the primary field zero flux plane generated at the center of symmetry of the dual transmitting coils to perform geomagnetic measurements and obtain the transient decay signal of the pure secondary field of the stratum. The acquired magnetotelluric response data and the transient attenuation signal of the pure secondary field of the stratum are input into the noise reduction system. The adaptive common-mode noise suppression algorithm is used to filter out power frequency and environmental electromagnetic interference, and the noise-reduced broadband electromagnetic data and transient electromagnetic data are extracted. The denoised broadband electromagnetic data and the transient electromagnetic data are inverted to obtain a two-dimensional resistivity profile reflecting the electrical structure of the strata, and the spatial distribution and burial depth range of the concealed copper-gold deposits are delineated based on the two-dimensional resistivity profile.

2. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 1, characterized in that, The specific methods for magnetic field measurement using a quantum geomagnetic field strength meter include: The quantum geomagnetic field strength meter is equipped with a diamond NV color center sensor. When acquiring the magnetotelluric response data, it uses the electron spin magnetic resonance effect under microwave excitation to perform broadband absolute measurement of the weak electromagnetic signals transmitted from the concealed copper-gold ore body to the surface in the orthogonal horizontal direction.

3. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 1, characterized in that, The specific methods for transmitting alternating current underground using the controlled-source audio-frequency magnetotelluric method include: The power supply transmitters are installed on the integrated geophysical detection line, and the length of the transmitter distance is controlled to be less than one-third of the transmit-receive distance. The alternating current with a frequency range of 7680 Hz to 1.2 Hz is transmitted underground using multiple superposition technology.

4. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 1, characterized in that, The method employs the equivalent anti-magnetic flux transient electromagnetic method to transmit bipolar pulsed currents underground, and places a quantum magnetometer on the primary field zero flux plane at the receiving end to conduct geomagnetic measurements. Specifically, this includes: The quantum magnetometer is placed on the zero flux plane of the primary field in the transmission current cut-off gap to eliminate the interference of the primary field induced electromotive force, and high-precision transient decay response of shallow, medium and deep formations is captured by superposition measurement of no less than two hundred times in order to obtain the complete pure secondary field transient decay signal of the formation.

5. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 4, characterized in that, The quantum magnetometer employs a biomagnetic measurement-level sensitivity configuration, specifically including: The magnetic field detection sensitivity of the quantum magnetometer placed on the primary field zero flux plane is adjusted to the picotesla to femtotes level.

6. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 1, characterized in that, The use of adaptive common-mode noise suppression algorithms to filter out power frequency and environmental electromagnetic interference specifically includes: The noise reduction system is used to apply the adaptive common-mode noise suppression algorithm to the magnetotelluric response data and the transient attenuation signal of the pure secondary field of the stratum, so as to filter out strong environmental electromagnetic interference caused by the superposition of shallow high-voltage power lines and underground ionizing current in the survey area.

7. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 6, characterized in that, The specific steps of executing the adaptive common-mode noise suppression algorithm include: A reference magnetic field detection base station is set up in the electromagnetic interference-free area at the far end of the integrated geophysical detection line. By dynamically comparing the raw data of the main measuring station on the measuring line with the data of the reference magnetic field detection base station, gradient noise reduction of the far-field ionized stray magnetic field is achieved.

8. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 1, characterized in that, The inversion processing of the noise-reduced broadband electromagnetic data and the transient electromagnetic data specifically includes: The apparent resistivity curve features of the denoised broadband electromagnetic data are extracted. For the static offset phenomenon caused by the upward or downward translation of the curve due to local electrical inhomogeneities near the surface, the data is statically corrected based on the surface resistivity distribution characteristics of the exploration area. An initial geoelectric model with topographic undulation information is established for two-dimensional constrained inversion.

9. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 8, characterized in that, Establishing an initial geoelectric model with topographic relief information and performing two-dimensional constrained inversion specifically includes: By employing the method of inverting and fitting apparent resistivity and phase hyperbolas, the statically corrected broadband electromagnetic data and transient electromagnetic data are combined in the depth domain. The two-dimensional smooth model algorithm is used for iterative convergence calculation to output the high-resolution two-dimensional resistivity profile.

10. The CSAMT and transient electromagnetic joint detection method for concealed copper-gold deposit exploration according to claim 1, characterized in that, Delineating the spatial distribution and burial depth of concealed copper-gold deposits based on the aforementioned two-dimensional resistivity cross-sections specifically includes: Based on the known electrical difference model between the concealed copper-gold ore body and its surrounding strata, relatively high-resistivity or low-resistivity anomaly zones reflecting the macroscopic outline of the deep strata are extracted from the two-dimensional resistivity cross-section. Combined with the structural features of local subtle anomalies in the shallow and middle layers obtained by transient electromagnetic method, the two-dimensional planar boundary of the concealed copper-gold ore body and the depth parameters of the top and bottom plates of the ore body are comprehensively delineated.

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