Deep metal deposits tend to be associated with heterogeneous geological bodies on different scales.Moreover,their orefields mostly lie in areas with complex geological structures,developed faults,and intense lithological changes and have complex surface conditions and structures.As a result,the seismic data of metal deposits frequently originate from complex and variable seismic wave fields suffering the mutual inference of multiple types of waves.Therefore,the seismic data have extremely low signal-to-noise ratios,which severely restricts the seismic interpretation of metal deposits and the prediction of concealed orebodies. With the 2D seismic data of the Chaganhua molybdenum orefield in Inner Mongolia as a case study,this study explored the key techniques for the seismic data processing of deep metal deposits.Specifically,this study analyzed the characteristic of seismic data of the Chaganhua molybdenum deposit and summarized the difficulties with seismic data processing of the metal deposit.Based on these,this study developed a set of processes for the data processing of the Chaganhua molybdenum orefield.The actual processing results agree well with the known orebody distribution in the geological borehole section.To be specific,zones with thick ore bodies generated strong reflected energy,while thinner ore bodies exhibited low-amplitude reflected waves.The results of this study can provide strong support for inferring geological structures and delineating concealed orebodies in the study area.

The Changjiang uranium ore field is located in the south-central part of the Zhuguangshan pluton in northern Guangdong Province. This ore field holds many uranium deposits such as Mianhuakeng (302), Shulouqiu (305), and Changpai. These uranium deposits are mainly distributed along the contact parts between the Changjiang and Youdong plutons, and uranium mineralization is closely related to the Changjiang and Youdong plutons and their intrusive dykes. Previous researchers have conducted much testing on the formation ages of plutons, dykes, and deposits in the Changjiang ore field, obtaining abundant age data. This study summarized the chronological study advances of the granites, uranium mineralization, and dykes in the Changjiang uranium ore field. The results are as follows. The Changjiang biotite granite pluton was formed at 166~157 Ma (weighted average age: 160.9 Ma) during the Middle-Late Jurassic. The Youdong two-mica granite pluton was formed at 245.6~219.6 Ma (weighted average age: 232.1 Ma) during the Triassic. A variety of dykes such as gabbro diorites, hornblende diabases, fine-grained granitic rocks, and lamprophyres have developed in the study area. The dykes in the ore field can be divided into at least three categories according to their activity stages, namely Late Jurassic mafic dykes (150~145.1 Ma), Early Cretaceous acid dykes (138.6~123.9 Ma), and Early Cretaceous mafic dykes (110 Ma). The uranium mineralization of the Changjiang uranium ore field began during the Early Cretaceous and lasted until the Paleocene, showing a long time span ranging from 127 to 60 Ma. The uranium metallogenic periods include the Early Cretaceous metallogenic epoch (127~119 Ma), the Late Cretaceous metallogenic epoch (75~67 Ma), and the Paleocene metallogenic epoch (61~54 Ma). The age data are concentrated in the range of 70~60 Ma (Late Cretaceous-Paleocene), which might be the peak of uranium mineralization of the study area. The diagenesis and uranium mineralization of the Changjiang uranium ore field evolved in the order of Youdong pluton → Changjiang pluton → early mafic dykes → fine-grained granitic dykes → early uranium mineralization stage → fine-grained biotite granite dykes → late mafic dykes → second uranium mineralization stage → late uranium mineralization stage. There are six phases of diagenesis and uranium mineralization of the Changjiang uranium ore field, i.e., Triassic granitic magmatism (the Youdong pluton), Middle-Late Jurassic granitic magmatism (the Changjiang pluton), diagenesis of Late Jurassic mafic dykes (gabbro diorite dykes, 150 Ma; hornblende diabase dykes, 145 Ma), diagenesis of Early Cretaceous dykes and uranium mineralization (138.6~110 Ma), Late Cretaceous uranium mineralization (75~67 Ma), and Paleocene uranium mineralization (61~54 Ma). It is recommended that further studies should be conducted on the metallogenic chronology of uranium deposits, the geochronology of other dykes such as lamprophyres, and the uranium metallogenic mechanisms of deposits except for Mianhuakeng (302), Shulouqiu(305), and Changpai.

This study introduced the development process, research status, and application effects of the tectono-geochemistry survey theory, and proposed the tectono-geochemistry weak information extraction method by summarizing the latest research results and understandings based on the prospecting practice in bedrock areas. Based on the contrastive analysis, this study pointed out the limitations of the conventional geochemical survey methods and the advantages of the tectono-geochemistry weak information extraction method, which was developed from the conventional tectono-geochemistry survey method. Moreover, this study systematically summarized the theoretical basis, operating conditions, deployment method, sampling principle, sampling media, anomaly interpretation, mapping, and application of the tectono-geochemistry weak information extraction method, highlighting the rationality of the deployment method, the representativeness of sampling points, the diversity of sampling media, and the validity (“yes” and “no”) of element anomalies and samples. Based on these, this study established the index system of this method. Finally, by combining the prospecting prediction of the eastern section of the Huijiabao anticline in the distribution area of Carlin-type gold deposits in southwestern Guizhou, this study concluded that the tectono-geochemistry weak information extraction method can extract the deep metallogenic weak information more effectively than the conventional tectono-geochemistry survey. It also inferred that this method has a good application prospect in the prospecting of concealed hydrothermal deposits and can be applied to the prospecting prediction of concealed hydrothermal deposits in all bedrock areas.

The Luzhou shale gas block,which is located in the southern Sichuan Basin,has undergone multi-stage tectonic evolution and has complex faults and multiple sets of vertical detachment layers,forming the characteristics of multiple stages,multiple strikes,and multiple layers.To overcome the difficulties with the tectonic interpretation of the study area,this study combined a set of seismic multi-attribute techniques,namely using seismic multi-attribute optimization and attribute fusion technique to assist fault interpretation,using structural anomaly attribute to identify microstructures,using seismic attribute slicing technique to analyze the characteristics of tectonic temporal and spatial evolution,and using multi-superposition ant tracking attribute technique to predict fracture development.Using this technique combination,this study completed the fine-scale interpretation of complex faults in the area, effectively characterized the development of microstructures,clarified the tectonic stages and distribution in the area,improved the fracture prediction accuracy,and described the development characteristics of fractures.The results of this study will provide solid data and a foundation for the next platform deployment.

The Baoding sag is located on the western margin of the Jizhong depression,Bohai Bay basin.It is adjacent to the uplift of the Taihang Mountains in the west,with the piedmont fault of the Taihang Mountains as the boundary.Identifying the deep structures and fine-scale geological structure of the sag is greatly significant for the hydrocarbon exploration and the survey and evaluation of deep thermal reservoirs in the sag.Meanwhile,it also facilitates the research on the characteristics of the piedmont fault of the Taihang Mountains.Since the exploration using the seismic reflection method feature high precision and high resolution in the detection of deep geological structure,this study conducted the seismic reflection-based exploration in the tectonic units of the Baoding sag and their periphery.First,high-quality original seismic records were obtained by means of explosive source excitation,long-array multi-channel reception,and high coverage times.Then,seismic reflection sections that can clearly reflect the deep geological structure and structural characteristics of the survey area were obtained using high-precision imaging data processing techniques,such as static correction,pre-stack noise attenuation,deconvolution,and offset stack.The obtained seismic sections allowed for determining the characteristics of faults in the sag and internal secondary tectonic units.Based on the angular unconformities identified in the seismic sections,the basement structural layer and the structural layers formed during the faulting stage and the depression stage of the Baoding sag were also determined,and,accordingly,the tectonic evolutionary process of the three structural layers were discussed.

As confirmed by exploration and development, many low-resistivity gas zones exist in the upper portion of layer Q₃c of the H Formation in structure A of Sag X. Given the problems such as unclear understanding of the geological sedimentary environment, insufficient microcosmic knowledge about the reservoirs, and unclear causes of the low resistivity of the gas zones, this study conducted extensive research based on the log data of three wells in the study area, as well as the data on drilling and many petrophysical experiments. Specifically, the petrological and physical property characteristics of the study area were studied using the thin-section identification data; the genetic mechanisms of low-resistivity gas zones were studied using the well tie sections and the special log data, as well as the data of many petrophysical experiments; the formation mechanisms of low-resistivity gas zones were confirmed from the microscopic visualization scale by constructing a multi-component conductivity model using the digital core technique, and the contributions of various low-resistivity geneses to the decrease in resistivity were quantitatively analyzed through the finite element-based electrical simulations. As indicated by the study results, the low-resistivity response of the gas zones in the study area is caused by the presence of clay minerals with high clay content and high cation exchange capacity and also results from the complex pore structure formed under the favorable physical property conditions in the anomalous high-pressure depositional setting. The contributions of the clay additional conductivity and the complex pore structure to the low resistivity are 35.63% and up to 64.37%, respectively. The electrical simulation results are consistent with the log-derived electrical characteristics, verifying the genetic mechanisms of the low-resistivity gas zones in the upper portion of the Q₃c.

The Xiwan lead-zinc deposit in Anhui Province is located on the northern margin of the Luzong volcanic basin. This deposit is an overburden area, causing great difficulties with exploration. Based on the analysis results of borehole core samples, this study analyzed the characteristics of the primary halos of the Xiwan lead-zinc deposit. The results show that the mineralized zone and its roof and floor have significantly different contents and anomaly characteristics of elements. Specifically, brecciated limestones in the mineralized zone have high contents of elements such as Pb, Zn, Ag, As, Sb, Bi, Au, Cu, and Mo. These elements feature high anomaly intensity and large anomaly scales and have definite concentrations and component zoning. These element anomalies effectively reflect the characteristics of orebodies and significantly indicate the NE-trending extension of ore bodies. The volcanic rocks on the roof of the mineralized zone have high contents of elements such as As, Sb, Pb, Zn, and Ag. These elements feature weak anomalies without significant zoning. These element anomalies can only indicate the ore bodies near the sampling points. The anhydrites on the floor have low contents of the abovementioned elements, without significant anomaly. Therefore, As, Sb, Pb, Zn, Ag, and Mo are indicator elements of lead-zinc mineralization in the study area. The brecciated limestones in the mineralized zone have high element contents, forming anomalies with high intensity and large scales. Moreover, these anomalies are characterized by significant concentrations and component zoning and can clearly indicate the extension direction of ore bodies. The contents and anomaly characteristics of elements in the core samples collected from different metallogenic parts can guide the further prospecting of the mining area.

The Xiangshan ore field is the largest volcanogenic uranium ore field in China with abundant uranium resources and favorable geothermal geological conditions. However, few studies have been conducted on its thermal structure and mineralization characteristics,In order to solve this problem effectively. Taking the Zoujiashan super-large uranium deposit in the west of the ore field as a typical area, this study systematically investigated the thermal structure characteristics of the ore field, established the thermal structure model, and analyzed the relationships between heat generation and mineralization. The results are as follows. The thermal structure in the study area is of the hot-mantle and cold-crust type, which is in line with the characteristics of thermal structures in eastern China. The higher crustal heat flow in the area is closely related to the uranium source and uranium ore bodies, and the decay heat generation of radionuclides is the main source of the crustal heat flow. The thermal anomalies in the area are obviously controlled by faults, and the heat source is highly consistent with the uranium source. The geothermal gradient anomalies are one of the prospecting criteria of the area. Moreover, 4 ℃/100 m is the positioning marker of deposits, and the variation amplitude of geothermal gradients can be used as the positioning marker of rich and large ore bodies. This study provides effective technical support for the study of geothermal geology and metallogenic geology in this area.

To achieve the accurate positioning of the water-conducting channels in the areas with unknown anomalous water inrush in the Beiminghe iron mine to ensure the safe production of the mine, this study explored the 11# across-vein roof at -110 m level in this iron mine using the mine transient electromagnetic method (MTEM). Firstly, this study briefly introduced the basic principle of MTEM and theoretically analyzed the characteristics of mine transient electromagnetic response under metal interferences. Then, it analyzed the geophysical characteristics based on the geology of the iron mine and corrected the measured data targeting metal interferences using the coefficient correction method. Afterward, the measured data were used as the initial model for the inversion of full-space transient electromagnetic using the bee colony algorithm, obtaining the high-resolution resistivity images of the working face roof. The images combined with the existing geological data allow for the fine detection of water-rich anomalous areas and water-conducting channels, and the detection results were verified by drilling. The results show that the MTEM can effectively improve the detection accuracy of water-rich anomalous positions in the roof strata of the working face in iron mines by means of effective data processing, thus providing effective technical support for water control in iron mines.

Karst is widely distributed in China. However, geological disasters frequently occur in karst zones due to the fragile geological environment, which seriously threatens the safety of people’s life and property and cause huge economic losses. In this study, the controlled source audio-frequency magnetotelluric (CSAMT) method and microgravity were used to extract residual gravity anomalies through the two-dimensional inversion of pseudosections and multi-scale wavelet analysis. As a result, rock-soil interfaces of karst zones and the development zones of strong karst were well divided; the locations, burial depths, scales, and spatial distribution of karst caves were delineated. As verified by drilling, the rock-soil interfaces and strong-karst development zones determined by CSAMT interpretation were roughly consistent with those revealed by boreholes, and the sizes and burial depths of collapsed karst caves that were delineated by microgravity roughly correspond to those revealed by boreholes of engineering exploration. These results show that the CSAMT combined with the microgravity method can achieve significant effects in the detection of concealed karst collapses and serves as a scientific detection method for the early warning of the prevention and treatment of potential karst collapses and similar geological disasters.

The Western Dinosaur Park of the Lanzhou New area, located in the Lanzhou-Minhe Basin, has encouraging prospects for geothermal exploration, development, and utilization. Based on the previous results of regional geological structure and geothermal characteristics, this study further investigated the geothermal reservoir horizons and the geothermal geological conditions using both the controlled source audio-frequency magnetotellurics (CSAMT) and the magnetotelluric sounding. Then, available geothermal water with suitable temperatures was discovered by drilling. Based on the geophysical exploration and drilling results, this study deduced and explained the structure and pluton distribution of the study area, analyzed the geothermal geological conditions, and pointed out the future exploration direction. The results of this study can be utilized as a reference for geothermal exploration in adjacent areas of the Western Dinosaur Park and similar areas.

Geothermal energy mainly migrates and accumulates along fractured zones. Ascertaining the faults in the study area is an important goal of geothermal exploration. Many faults are distributed in the Zhangye-Minle basin. They are deeply buried and are difficult to find on the surface. The special geological conditions make it difficult to fully utilize the advantages of conventional geophysical methods. By contrast, the activated charcoal radon measurement features strong anti-interference, large detection depth, and low cost, which are unique advantages in detecting concealed structures. This study investigated the concealed structures in the Zhangye-Minle basin using the activated charcoal radon measurement. Through the trend analysis of measured radon concentrations, this study extracted local anomalies and determined the favorable parts for the geothermal water exploration in the study area, creating conditions for further drilling and shallow artificial seismic exploration.

The Technical Symbols for Geochemical Exploration (GB/T 14839-93) is a national standard formulated in the early 1990s, including 101 symbols. The revision of this standard began in 2019 according to the following principles: (a) Inheriting the original symbols. The stability and continuity of the original standard content should be maintained as far as possible; (b) Selecting new symbols in line with professional habits. It is necessary to select symbols that are widely used in geochemical exploration and are recognized by most peers as far as possible; (c) Matching the development of geochemical exploration technologies. The revised technical symbols for geochemical exploration should cover all fields involved in the current geochemical explorations; (d) Focusing on the commonly used geochemical symbols. The commonly used geochemical symbols should be included. According to the above principles, special technical symbols for ecological geochemical surveys and evaluation were newly added, and the expanded symbols include general technical symbols for geochemical exploration and special technical symbols for mineral geochemical exploration and geochemical sample testing. A total of 173 symbols were included in the revised standard. The revised technical symbols for geochemical exploration can be divided into a general type and a special type according to their application scopes. The special geochemical symbols can be categorized into three subtypes according to their application fields, namely mineral exploration, ecological environment investigation and evaluation, and geochemical sample testing. The fields covered by the revised standard are consistent with the current application fields of geochemical exploration technologies.

The inversion of electromagnetic detection data is a typical ill-posed problem and is prone to cause a multiplicity of solutions of the inversion results. The ill-posedness is an inherent characteristic of inversion and is difficult to overcome without additional information. An effective way to solve this problem is constrained inversion. In this study, the Gauss-Newton - conjugate gradient (GN-CG) method was used to directly impose constraints on the inversion objective function. Specifically, the dielectric resistivity range was introduced into the inversion objective function as the prior information and constraints using the exterior penalty function method. Compared with the conventional three-dimensional resistivity inversion objective function, the objective function with inequality constraints can suppress the multiplicity of solutions in theory. As revealed by the testing results of various theoretical models, the three-dimensional borehole-to-surface resistivity inversion algorithm based on inequality constraints effectively improves the precision of inversion results, and the way of imposing inequality constraints using the penalty function method is feasible and effective.

Random noise attenuation played an important role in the seismic data processing. The low-rank estimation of the seismic signal in the time-frequency domain is essentially a trace-by-trace process, which cannot exploit the channel-to-channel coherence of the signal. We propose a novel random noise attenuation based on f-x low-rank matrix approximation with nonconvex regularization. Firstly, the noisy seismic data is transformed into the f-x domain by Fourier transform. Then, the time-frequency method is employed to decompose each discrete frequency slice. Finally, we estimate the sparse low-rank matrix from the obtained noisy matrix. This method enables the denoising of non-stationary signals by exploiting the spectral differences between signal and noise. Compared with the common shot and mid-point gathers, the common offset gather is characterized by flat events, which basically satisfies the assumption of linear events for f-x domain denoising, and it is suggested that the proposed algorithm should be applied to the common offset gather. Synthetic and real data sets demonstrate the performance of our proposed method in random noise suppression and preserving more useful energy.

The acquisition system is a very important part of a broadband spectral induced polarization (SIP) tester for rock and ore samples. Its performance directly determines the precision, power consumption, sampling rate, and signal-to-noise ratio of the tester. Therefore, it is a focus and challenge throughout the development of a tester to design an acquisition system with high input impedance, a high sampling rate, high precision, low noise, and low power consumption. Based on the principle of the quadrupole method, this study designed an acquisition system of a SIP tester that integrates four acquisition channels. The acquisition system uses the 24-bit ADC chip AD7760 to realize A/D conversion, uses the AD9837 chip to generate sine waveforms for self-check of the tester, and uses the FPGA chip of the model XC6SLX25 to control the acquisition system. The test results of the system are as follow. The acquisition system has input impedance greater than 1 TΩ, survey precision of 0.4%, a sampling rate of up to 2.5 MHz, and a bandwidth of 1~200 kHz. Each sampling channel of the acquisition system has short-circuit noise less than 1 mV and supports 1/5/25/125 times adjustable gain. The voltage and current of the signal source can be switched among 1 mV, 10 mV, 100 mV, 1 V, and 10 V and 1 μA, 10 μA, 100 μA, 1 mA, and 10 mA, respectively. The hardware acquisition system developed in this study can meet the needs for broadband SIP tests of rock and ore samples.

Spectral induced polarization (SIP) response testers for rock and ore specimens determine the SIP response differences between ore bodies and host rocks by measuring the SIP characteristics of rock and ore specimens, thus providing a basis for ore prospecting. They are widely used in geophysical exploration. However, the existing SIP response testers have shortcomings in terms of bandwidth, intelligence, portability, and power consumption. Given this, this study developed a piece of measurement and control software for SIP response testers based on the Internet of Things (IoT) techniques including NB-IoT, Bluetooth, and Wifi, realizing the functions such as near-field communication, cloud communication, data visualization, and data processing. The test results verify that the software can achieve the desired effect owing to its easy operation, stable running, and friendly man-machine interaction.

The phase-shift method is commonly used to extract the Rayleigh wave dispersion curves.However,in the case of a complex wave field,the dispersion spectra calculated using the phase-shift method have a low resolution of Rayleigh wave dispersion energy,reducing the accuracy of the dispersion curves.This study improved the phase-shift method by obtaining the power exponent of the amplitude of each point on the dispersion spectra to improve the convergence and focusing properties of the dispersion energy.The improved phase-shift method was used to process the simulated data of the theoretical stratigraphic model and the actual seismic data of a coalfield in a certain study area.The processing results were compared with the dispersion spectra generated using the conventional phase-shift method.Moreover,the inversion based on dispersion curves of the actual data was conducted to generate a two-dimensional (2D) S-wave velocity section of the study area.As revealed by the study results,the improved phase-shift method can enhance the signal-to-noise ratio of the Rayleigh wave signals in the frequency-velocity domain and improve the resolution of the dispersion energy spectra and the accuracy of the dispersion curves.

The seismic impedance inversion is nonlinear optimization based on seismic data to obtain wave impedance parameters.The global optimization algorithm independent of the gradient information of objective function is an effective method for seismic impedance inversion.However,this method adopts a trace-by-trace inversion strategy and ignores the spatial correlation of adjacent seismic traces,resulting in poor lateral continuity of the inversion results.Given this,this study proposed a model space initialization method integrating the optimal solution of the bypass to restrict the search space of wave impedance inversion,in order to improve the lateral continuity of inversion results.Based on this,this study proposed a seismic impedance inversion method with lateral constraints based on multi-group variation differential evolution.A case of synthetic seismogram shows that this method has a higher convergence rate and better lateral continuity of inversion results than conventional methods.This method was applied to the inversion of reservoir impedance parameters of a block of the Shengli Oilfield.The obtained inversion results were in good agreement with the logging data and effectively characterize the thickness of reservoir sandstone.

The seismic slope tomography is an effective method for building macro-velocity models using the travel time and slopes of locally coherent events of reflected waves.For data with low signal-to-noise ratios,the deep effective reflection wave data that can be picked are often far fewer than the shallow reflection wave data,resulting in a poor tomographic inversion effect of the velocity of the deep strata.Therefore,this study proposed a 3D seismic slope tomography method based on depth weighting.In the linear tomographic inversion equation of each iteration,the depth weighting was performed for the kernel function of the observed data on the node velocity of the discrete model.The weighting coefficient was determined according to the node depth of the discrete model and the reflection point depth of each shot-detection pair of the current iteration,increasing the constraining effect of deep reflection wave data on the deep velocity.Meanwhile,the shallow velocity was mainly constrained by the shallow reflection wave data.As a result,the inversion effect of deep velocity could be improved while maintaining the inversion precision of shallow velocity.The application and tests of both theoretical model data and actual data yielded satisfactory results,verifying the effectiveness of the method.

The dolomites in the Dengying Formation in the Gaoshi-Moxi area,Sichuan Basin have strong anisotropy,causing great differences in acoustic and resistivity curves measured at horizontal and vertical wells and unclear interpretation of logging response rules,thus affecting the application performance of the horizontal well technique in actual reservoirs.With the dolomite outcrops in the Gaoshi-Moxi area as a case study,this study designed and conducted the synchronous measurement experiments of resistivity and acoustic waves of cores in different directions under high-temperature and high-pressure conditions and analyzed the experimental relationship between acoustic and electrical anisotropy coefficients.The experimental results show that there was a positive linear correlation between the two coefficients at 60℃ and 60 MPa.Specifically,with an increase in water saturation,the compressional wave velocity increased,the resistivity decreased,and acoustic and electrical anisotropy coefficients increased.This result provides an experimental basis for the correlation analysis of acoustic-electrical anisotropy and the correction of the differences in the acoustic waves and resistivity.

Geothermal resources are widely distributed in the Beijing-Tianjin-Hebei region and the Xiong'an New Area and are mainly characterized by deep carbonate geothermal reservoirs. To achieve stable and increased production of geothermal reservoirs, it is effective to detect and evaluate the fracture parameters of reservoirs and analyze the distribution patterns of tectonic fractures in underground rock masses using the ultrasonic imaging logging technique. Targeting the high-temperature and high-pressure environment of deep carbonate geothermal reservoirs, this study developed an ultrasonic imaging logging system, which can be used under the conditions of well depth greater than 4,000 m, well diameter of 150~500 mm, temperature greater than 110℃, continuous operating time greater than 12 h, and pixels per meter of a geological well greater than 50,000. The equipment of this ultrasonic imaging logging system has been tested in well D22 in Xiong'an New Area. The test results show that the developed ultrasonic imaging logging system has a clear imaging effect and high identification degree of fractures and that its various performance indicators are comparable to those of advanced foreign equipment. Therefore, this system can provide an efficient technical method for identifying fractures and fractured zones and analyzing the occurrence of deep carbonate geothermal reservoirs.

To further improve the precision of gravity gradient measurement, this study proposed a method for real-time phase angle compensation of gravity gradient demodulation and real-time processing of gravity gradients. Firstly, this study determined the process and formula used to determine the phase angles for gravity gradient demodulation based on the structural features of the gravity gradiometer prototype. Then, it investigated the method for real-time gravity gradient demodulation and determined the formula. Finally, this study carried out simulation experiments using the hardware-in-the-loop simulation platform of gravity gradient signals. The simulation results show that the method proposed in this study can significantly improve the precision of gravity gradient measurement and can be applied to engineering. Therefore, this study can provide technical references for the development of airborne gravity gradiometers.

The surface-related multiple elimination (SRME) method is usually used to predict the multiples of marine seismic data.However,it cannot be used to predict the interbed multiples formed between strong reflection interfaces in seismic data.This study,based on the Huygens principle and the received known seismic wave fields,inferred the interbed multiples propagating between the strong reflection interfaces using Green's function.First,the Green's function propagating between the strong reflection interfaces at each receiver was calculated;then the obtained Green's function was convoluted with the received wave field(the original seismic data received by all receivers of the current shot gather);finally,the sum of the results was taken as the model of the interbed multiples of the current receiver.Subsequently,subtracting the multiple model from the original data through adaptive subtraction achieved the prediction and attenuation of interbed multiples.The tests based on simulation data and actual data indicate that the method proposed in this study can effectively attenuate interbed multiples.

The conventional diurnal variation correction of multiple geomagnetic stations based on geographic coordinates is to increase the precision of diurnal variation correction by improving the calculation methods. Based on the comparative analysis of conventional diurnal variation correction methods, this study proposed the geomagnetic coordinate fitting method for diurnal variation correction based on the high correlation between geomagnetic coordinates and geomagnetic field strength. The experimental results show that the diurnal variation correction of multiple geomagnetic stations based on geomagnetic coordinates generally improves the precision of diurnal variation correction and, thus, serves as a new study approach for diurnal variation correction of multiple geomagnetic stations.

In order to meet the requirements of portable,intelligent and long-term automatic monitoring of 192 channel spontaneous potential monitor,the shortcomings of the acquisition and control equipment of current electrical exploration instruments in man-machine interaction,endurance and portability are solved.In this paper,the acquisition and control software based on Android platform is designed by combining Bluetooth,Wifi and other IoT technologies with geophysical instruments.After testing,the software function is efficient,the data transmission quality is good,the software runs stably.In the practical application of natural electric field signal detection of geological microorganisms, the performance is stable and can be monitored continuously for more than 36 h. The data acquisition accuracy is high, and the visualization effect is good, so it has strong practical application value.

The high-precision magnetic field measurement module is mainly used in the scientific fields such as geology, geophysics, and national defense. However, the existing three-component magnetic field measurement module suffers poor portability (requiring a PC for data acquisition), large background noise, and short operating time. Therefore, this study developed a portable three-component magnetic field measurement module:a high-precision data measurement module and an Android control program. The test results show that the measurement module supports the interactive control using Android mobile phones and enjoys the advantages of low background noise (dynamic range>121dB@fs=1,000Hz), high clock synchronization precision (time drift±0.87 ms/day), long operating time (for one-week continuous work), and high scalability (supporting multiple fluxgate sensors).Portable three-component magnetic field mesurement module is portable,simpk and easy to use,suitable for field testing.

GOCAD (Geological-Object Computer-Aided Design) is now a piece of internationally recognized mainstream modeling software with functions of powerful 3D modeling, visualization, geological interpretation, and analysis. It has been widely used in the fields such as geological engineering, geophysical prospecting, mining development, and water conservancy engineering. Drilling data and geophysical prospecting data are the important modeling basis for 3D geological modeling. GOCAD provides a general data import function, which, however, is not fully applicable to actual production data. As a result, these data need to be processed and converted before being imported. Based on the GOCAD development kit, this study developed a data interface for drilling data and geophysical prospecting data derived from production to quickly and efficiently import multi-source geological prospecting data into GOCAD, thus greatly saving the time for 3D geological modeling.

Determining the geometric position of the zero magnetic flux plane is the key to the detection system of the opposing-coils transient electromagnetic method (opposing-coils TEM). Given this, a zeroing method was proposed in this study. First, an opposing-coils transient electromagnetometer was used to continuously send the bipolar square wave of fixed frequency. Then, the receiver collected the time domain signals of the receiving antenna in real time, and the discrete Fourier transform was used to calculate the minimum power spectral density (A1, A2 and A3) at the roughly-, finely-, and micro-tuned receiving antenna positions. When A1>A2>A3, the receiving antenna was in the zero magnetic flux plane. Finally, the test results of transmitting 20 kHz bipolar square wave showed that the transition process of the attenuation signals of the secondary field can be significantly improved under the condition of A1>A2>A3.

The 1∶250 000 multi-target geochemical survey shows that there is a large area of zinc-rich fluvo-aquic soil in northern Anhui Province, and the study on the distribution law, bioavailability, and influencing factors of zinc in the soil is of great significance to the development of zinc-rich agricultural industries. This study investigated the distribution characteristics, occurrence forms, bioavailability, and influencing factors of zinc in the topsoil at a depth of 0~20 cm and the section soil of 0~200 cm depth of both the fluvo-aquic soil and the lime concretion black soil in northern Anhui Province. The results are as follows: The fluvo-aquic soil has abundant total zinc and moderate available zinc, while the lime concretion black soil lacks the total zinc in general and is rich in available zinc. The total zinc in the fluvo-aquic soil is significantly positively correlated with manganese, organic matter, and phosphorus. The available zinc in both the fluvo-aquic soil and the lime concretion black soil is positively correlated with the available phosphorus and negatively correlated with pH. The zinc in the soil at the depth of 0~200 cm mainly occurs as residuals for both the fluvo-aquic soil and the sand concretion black soil. The total content of the water-soluble and ion-exchangeable zinc that is easily absorbed by plants in the plough layer of the fluvo-aquic soil area accounts for 0.29% of the total zinc content, and the content of iron-manganese oxide bound zinc accounts for 23.62% of the total zinc content. The total zinc is obviously enriched in the soil at a depth of 0~85 cm, which is significantly restricted by the phosphorus and manganese contents in the soil. The total content of the water-soluble and ion-exchangeable zinc in the plough layer of the lime concretion black soil area accounts for 0.41% of the total zinc content, and the total zinc content in the soil at a depth of 0~200 cm slightly changes. This study indicates that the fluvo-aquic soil in the study area has rich total zinc and moderate available zinc and that the available zinc content is mainly restricted by the pH of soil. Therefore, applying conditioners to reduce the pH of soil is an effective way to enhance the bioavailability of zinc in the total-zinc-rich fluvo-aquic soil.

Soil germanium natural endowment, genesis sources, ecological and environmental effects and human health assessment are important research directions in the ecological geology of black soil, and the quantitative study of germanium distribution characteristics, migration transformation and influencing factors in the soil-rice human system is of great significance to the development of germanium-rich agricultural products and human health in black soil areas. Based on the 1∶50,000 ecogeochemical survey of land quality in the Shuangyang River Basin, we obtained germanium and other elemental data from multi-media such as soil-forming parent material, top soil, rice seeds, root soil and human hair, and used GIS and SPSS software to statistically analyze the data. The results showed that the germanium content of the top soil ranged from 0.996×10^-6 to 1.626×10^-6, with an average value of 1.326×10^-6, and the high value areas were mainly distributed in the northwest and central south of the north side of Shuangyang River; 70.55 km² and 166.9 km² of germanium-rich and germanium-sufficient arable land were delineated, which had a greater potential for developing green germanium-rich and selenium-rich agricultural products. Soil-forming parent material is the main factor affecting the germanium content of topsoil, and soil type and land use type have less influence; soil environment with acidic and organic matter deficiency may be more favorable for germanium enrichment. The germanium content of rice seeds ranged from 0.24×10^-6 to 3.40×10^-6, with a mean value of 1.59×10^-6, and the samples meeting the moderate and strong uptake criteria accounted for 40% and 60%, respectively, and were at significantly germanium-rich levels. The germanium uptake coefficient (Ax)was significantly negatively correlated with the root soil germanium content (p=-0.34^*), indicating that low concentrations of soil germanium have a promoting effect on rice growth and development, and high concentrations of germanium have an inhibitory or toxic effect on rice growth; it was positively correlated with the root soil pH (p=0.40), indicating that the migration and transformation ability of rice to germanium elements gradually increases with the increase of soil pH. Adult hair germanium levels were at normal healthy levels, but germanium levels in immature female hair significantly exceeded the reference range, and more detailed studies are needed for human health assessment.

This study aims to further understand different input ways of heavy metal elements into the agroecosystem and resultant soil pollution and to promote the sustainable development of agriculture in the Jianghan Plain. To this end, data were collected from the geochemical assessment project on the land quality of Honghu City from 2014 to 2019 and were studied as a whole. Then, this study conducted geochemical analyses of heavy metal elements such as Cr and Hg input via three ways, namely atmospheric dry and wet subsidence, irrigation water, and chemical fertilizers, and calculated the input amount of the heavy metal elements via each way. Based on these, this study explored the impacts of the three ways on land quality. The results are as follows:①The land quality in Honghu City is slightly affected by human activities; ②The total input flux of different elements differs greatly with the input ways, reflecting the differences in the heavy metal elements input via local agricultural activities; ③The annual input flux of heavy metal elements via irrigation water is relatively high, and irrigation water contributes the most to the heavy metal elements (except for Zn, Cr, and Pb) input to soil.

This study investigated the surface soil of the agricultural land in Ruoqiang County, Xinjiang. Based on 142 surface soil samples collected in 2016, this study analyzed the selenium (Se), fluorine (F), iodine (I), Al₂O₃, and SiO₂ contents and the physicochemical proxies such as soil organic carbon (OrgC), total nitrogen (N), and pH of the surface oil in the study area. Then, this study explored the contents and distribution of biological elements Se, F, and I in the study area, as well as their influencing factors. The results are as follows. The soil in the study area is alkaline to strongly alkaline, with average Se, F, and I contents of 0.23×10^-6, 645×10^-6, and 1.06×10^-6, respectively. The average contents of Se and I are lower than their national soil background values, while the average content of F is much higher than its national soil background value. The Se, F, and I contents are positively correlated with each other and all of them are significantly positively correlated with total N. The Se content is negatively correlated with the SiO₂ content, while the I content is positively correlated with the Al₂O₃ content. The contents, distribution, and geochemical characteristics of Se, F, and I are controlled by parent materials and soil types. Among different parent materials, the Se, F, and I contents are higher in the soil of diluvium areas but are the lowest in the soil of alluvium-diluvium areas. Among different types of soil, the contents of the three elements are high in the irrigation-silted soil, while the Se content is the highest and the F and I contents are the lowest in the forest-shrub-grassland soil.