In order to study the combination of effective geophysical and geochemical prospecting methods in mineral inspection work in arid desert areas and to achieve regional mineral prospecting breakthroughs, the authors conducted the mineral survey work in an arid desert area in the Heiyingshan area of Inner Mongolia. Geophysical and geochemical methods were used in search for copper polymetallic deposits. Geological survey, high-power IP, high-precision magnetic survey at a scale of 1∶10 000 and thermomagnetic component soil measurement (1∶50 000) were carried out in the survey area. IP anomalies and magnetic anomalies were delineated, and characteristics of multi-element combination were revealed after data processing. The controllable source audio magnetotelluric sounding profiles were arranged in the locations of the IP anomalies and the anomaly concentration places of the elements to determine the downward distribution of the two high conductivity anomalies. The trench reveals that strong silicification, skarnization and malachite mineralization occur at the contact zone between the albite-actinolite-schist mixed with metamorphic quartz sandstone in the Gongpoquan Formation and the marble. The content of Cu and Ag in the samples reaches the boundarygrade. The ore-search prospects in the survey area are good and further work should be carried out.

Light hydrocarbons in an underground hydrocarbon reservoir can reach the surface in a trace yet detectable amount through near-vertical microseepage, and some of them may occur in free form in the pores of soil or rock particles. Hydrocarbon in soil gas can indicate the current compensatory active microseepage of hydrocarbons in deep reservoirs; therefore, it is thought to be one of the most reliable methods in geochemical prospecting for oil and gas. The collection of free gas from soil is a key technique for obtaining the geochemical anomalies of microseepage hydrocarbons in Quaternary sediments. A new portable soil gas collection device was developed, which is easy to operate, easy to carry and has good air tightness. The ways of soil free gas fidelity collection are summarized through long-term practice. Soil gas method was applied to geochemical prospecting for oil and gas in Linan-Qianguantun area on the south slope of Huimin sag, Jiyang depression and X well block of Akyasu area, Tarim basin. The soil free hydrocarbon anomalies can well reflect the near surface information from vertical microseepage as well as the distribution characteristics of oil and gas accumulations underground. The surface geochemical anomaly of oil and gas accumulations is significantly different from that of the background area. The results show that the soil gas method is very effective and deserves wide application in oil and gas exploration.

Coalbed methane content is one of the key parameters in coal seam exploration and development research. Due to the influence of many factors on coalbed methane content, it is very important to predict coalbed methane content effectively. In this paper, slope correlation degree method and random forest algorithm are combined to predict coalbed methane content based on geophysical logging data. Firstly, the improved slope correlation degree method is used to obtain the favorable geophysical logging curves for CBM content prediction, and then the cross validation method is used to explore the appropriate number of random forest decision trees, and the random forest algorithm is used to predict the coalbed methane content for the logging curve sequence with positive correlation. With the No.3 seam in Shizhuang north area of Qinshui coalfield as an example, the block was evaluated and predicted with the results compared with the results of multiple regression model, and the anti-interference ability of the model was studied and analyzed. The results show that the application of slope correlation method to analyzing and calculating the geophysical logging curve and coalbed methane content can accurately and effectively find the logging curve that can be used to predict the content of coalbed methane, the model trained by random forest algorithm is accurate in predicting the content of coalbed methane in the non-gangue section, and the calculation result has high reliability, but the prediction ability is weak in the gangue section. The results obtained by the authors are of guiding significance to the exploration and development of coalbed methane and have practical application value.

In the Mesozoic and Cenozoic basin areas, the aeromagnetic ΔT anomaly information of sandstone-type uranium deposits is not obvious due to the influence of the basin cover layer, which directly affects the application effect of using aeromagnetic data to find sandstone-type uranium deposits. The research on the method of extracting weak information of aeromagnetic data in the basin can give full play to the role of aeromagnetic data in the exploration of sandstone-type uranium deposits. This paper summarizes the mechanism of the formation of weak aeromagnetic anomalies in sandstone-type uranium deposits, and analyzes and defines the quantitative range of weak aeromagnetic anomalies. On the basis of the 1∶50,000 high-precision aeromagnetic data and through the analysis and research on the aeromagnetic characteristics of the sandstone-type uranium deposits discovered in western Inner Mongolia, a high-pass filtering method was used to extract the aeromagnetic data above the sandstone-type uranium deposit. This method was used to carry out aeromagnetic weak anomaly extraction experiments in a uranium metallogenic belt in Erlian Basin of Inner Mongolia. The aeromagnetic weak anomaly information was extracted above three discovered interlayer oxidation zones of sandstone-type uranium deposits, thus finding a new way in the search for sandstone-type uranium deposits in the Meso-Cenozoic basin area.

Drilling has revealed that the Archean buried hill of BZ-A has great potential for natural gas exploration.In the target area,the metamorphic rock fracture reservoir in Archean buried hill has many problems such as great buried depth,strong heterogeneity of the reservoir and rapid lateral changes,which pose challenges to the exploration.Based on the study of the genetic mechanism of fractured reservoirs in buried hill,the authors comprehensively analyzed the features of the weathered fractured zone and the inner fractured zone,and established a targeted technical system for the description of fractured reservoirs in buried hill.For the weathered zone fractured reservoir,the pre-stack fracture reservoir porosity prediction technology based on the double-parameter was innovatively used,and the fracture reservoir porosity was predicted by the 3D elastic parameter analysis,and the distribution of the fractured reservoir in the weathered zone was finely described.For the inner fractured zone,the F-K domain coherence enhancement technique was used to improve the imaging of the buried hill.The method of edge enhanced crack detection based on clustering analysis was used to comprehensively characterize the distribution of reservoir in the inner fracture zone.Through the comprehensive application of targeted geophysical techniques, the exploration evaluation of BZ-A has been strongly promoted,thus providing a strong basis for the further exploration evaluation of the target area.

Based on the formula system of the electromagnetic field of the horizontal electric dipole source on the layered earth surface, this paper proposes the wide field apparent resistivity of y-component magnetic field (H_y) using the modulus of impedance. The field components E_x, H_y, and H_z of the electromagnetic field with multiple source-receiver separations on the surface of layered geoelectric model are calculated. The wide field apparent resistivity with these three field components and E_x/H_y cagniard resistivity are calculated, and compared with the MT Cagniard resistivity spectrum curve of the model. It is suggested that the wide field apparent resistivity of H_y has a good response to the geoelectric model in the vast area of the equatorial array and the axial array of the horizontal electric dipole source, and it can be used for single component wide field electromagnetic sounding. The axial array wide field apparent resistivity of H_y is similar to that of the equatorial array wide field of the vertical magnetic field of H_z. In the low frequency band, the wide field apparent resistivity of H_y is similar to that of the Cagniard resistivity of the magnetotelluric sounding of the layered model. Under the condition of small source-receiver separation, the axial array wide field apparent resistivity of H_y can have a better response to the deep basement. The equatorial array and the axial array wide field apparent resistivity of the E_x component of the horizontal electric field will wholly enter "saturated area" in the low frequency band. For each resistivity definition method, the appropriate source-receiver separation is the premise to reflect the geoelectric characteristics better, and the multi source-receiver separation measurement is more conducive to reflecting the deep electrical characteristics.

Compared with the post-stack inversion,coupling features in impedance are complex.The pre-stack inversion can make full use of the information such as the amplitude and travel time and frequency of the prestack seismic data,more diverse logging data and geology,and yields geophysical parameters that are highly correlated with hydrate saturation.Seismic rock physics modeling of hydrate reservoirs is the basis for hydrate-oriented prestack inversion.Considering the microscopic pore structure and composition characteristics of hydrate reservoir rocks,this paper introduces SCA-DEM rock physics modeling methods.The influence of physicochemical parameters on the elastic characteristics of rock and its role in AVO characteristics are analyzed.The geophysical response of hydrates is discussed and a new hydrate seismic indicator is constructed.Seismic rock physics analysis shows that the indicator has a high correlation with hydrate saturation.Then,the seismic reflection equation based on hydrate indicator is derived and the feasibility analysis of the inversion is carried out. Finally, based on geological prior, we get the indicator using the actual pre-stack data and logging data in the Qiongdongnan sea of South China Sea.The real data application shows that the method has certain practicability and scientificity.

Generally, audio frequency magnetotelluric sounding (AMT) and controlled source audio frequency magnetotelluric sounding (CSAMT) are used for deep exploration. The AMT method has a relatively wide acquisition frequency band, but is affected by weak signals in certain frequency bands of the natural field, which is called "dead band". In the "dead band" range, the geological body response cannot be obtained completely. However, CSAMT has the characteristics of high signal-to-noise ratio due to the introduction of artificial source; therefore, due to the limitation of transmitting power, the distance between transmitting and receiving is generally not far enough, so it is easy to enter the "near area" prematurely. This paper proposes a processing method that combines the two methods of data splicing. Firstly, on the basis of previous theoretical research, the forward calculation is carried out by using CSAMT and AMT uniform half space model, and the results show that the combination of CSAMT and AMT data is feasible. Secondly, the field measured data of No. 7 geological section of the Renli niobium and tantalum deposit in Hunan Province are tested by using the CSAMT far area data and the AMT data at the same measuring point with the same mode to "splice". Finally, the new AMT data derived from synthesization are used. The results show that the inversion results and the drilling results correspond well, which proves that the method has good promotion significance.

Airborne gravimetry uses aircraft as a carrier to collect data of gravity field. Due to the influence of air flow, flight state and body vibration, the original data of airborne gravity measurement contain a large amount of noise, and the SNR is as high as the grade of several thousand to ten thousand. This becomes a technical problem for the development of airborne gravity measurement system to obtain the weak gravity signal from the original measurement data. In this paper, the general Kalman filter formula with certain control was adjusted for adaptability based on airborne gravity measurement system, the mathematical model of the airborne gravity anomaly was established, and the Kalman filter state equation was proposed for measuring principle of the system. Finally, the authors solved the problem of gravity signal and differential GNSS signals matching and airborne gravity of weak signal extraction. After the test of airborne gravity measurement data, the proposed airborne gravity data solution method can be used to solve airborne gravity anomalies with high accuracy, and the result is better than the FIR low-pass filter (currently used in engineering) solution results, which promotes the development of airborne gravity weak signal extraction technology.

In order to separate and extract the effective signals from gravity and magnetic data, the authors studied a method developed in the past ten years—Curvelet transform method. Starting with the basic principles of the Curvelet transform, the authors analyzed the multi-scale decomposition and reconstruction ability of the Curvelet transform through the theoretical model data of the gravity potential field, and analyzed the threshold denoising ability of the Curvelet transform by the noise-added theoretical model data. In addition, the Curvelet transform was used to extract effective signals from the Bouguer gravity anomaly data in the eastern part of Nanling. The results verify that the method can be applied to both the decomposition and denoising processing of potential field data. The results provide a reference for the multi-scale analysis and processing of gravity and magnetic data as well as a certain indication for actual data.

Determination of the spatial position of the rugged topography surface is the key to the success of the pre-stack depth migration and velocity modeling on relief surface.The floating datum is not only a rugged topography elevation surface,but also defines the rules on which the CMP gathers are used for datum corrections.Analyzed the definition of the floating datum and clarified the physical meaning of the floating datum in general situations.The seismic data and velocity on floating datum can be directly used for topography pre-stack depth migration and velocity modeling under specific conditions.Discussed the situation that the improper use of floating datum data and corresponding RMS velocity in pre-stack depth migration and velocity modeling might result in shifting and distortion of the horizon layers in depth migration results.

Multi-source semi-airborne TEM is a supplement and development of electric source semi-airborne TEM. It has characteristics of great detective depth, strong adaptability in complex topography and high working efficiency. Based on the one-dimensional forward algorithm, the author analyzed the full-component response of parallel source and multi-source and single-source models. The results show that the curve of vertical component z is the simplest and it can be significantly strengthened with multi-source, which means this component is the most suitable one for data processing and interpretation. The most complex component is x. The curve always shows sign-changing in full field, but the magnitude can be strengthened in late stage. As the horizontal component y is most affected by current direction and receiver location, the curve shape and magnitude change are both complicated. Combined with the response characteristics of magnitude variation versus offset, it is suggested that the working area should be within the range of 5~6 times of source length. The research results in this paper can provide a reference for technical support to its application and obtain a preliminary understanding of the method.

In this study, the authors compared the loop source transient electromagnetic sounding effect between the induced voltage data and B_z data obtained by one-dimensional and three-dimensional forward modelling. The longest effective delay time of the two types of data under the current data acquisition accuracy of mainstream hardware was analyzed through a comparison of multiple models; the longitudinal and horizontal resolutions of the two types of data were analyzed through a comparison of apparent conductivity and one-dimensional inversion. The results show that, under the data acquisition accuracy presumed in this study, only when an abnormal body with a conductivity ≥ 0.036 S/m exists in the model can the effective delay time of the B_z data be longer than the induced voltage data. Compared with the induced voltage data, the B_z data can sense the underground anomaly in advance, but are worse in longitudinal and horizontal resolutions. The recovery of resistivity by B_z data is also worse than that by the induced voltage data. In the actual field measurement, it is not recommended to record only the B_z field. If conditions are allowed, the induced voltage and the B_z field could be collected simultaneously to obtain an optimized solution.

Previous studies have shown that CNN-GRU hybrid deep learning inversion EI has the advantages of strong applicability and strong generalization capability.However,there are many pre-stack inversion parameters based on deep learning,such as internal deep learning network learnable parameters and external hyperparameters.At present,there is still no systematic research on the impact of hyperparameter selection on network performance and computing speed,which will directly affect the further promotion and application of the method.Therefore,based on the hybrid deep learning inversion elastic impedance,this paper discusses the impact of five hyperparameters,i.e.,learning rate,Epoch,batch_size,regularization parameter,and the number of wells participating in network training on network performance and calculation speed,thus providing a basis for studying the selection of seismic inversion hyperparameters.The research results can provide a feasible quality control method for three-dimensional large-area deep learning inversion,which is of certain significance for promoting the wide application of deep learning methods in petroleum geophysical prospecting.

Prestack seismic data contain elastic and viscoelastic information such as P-wave velocity,S-wave velocity,density and absorption attenuation parameters,among which absorption attenuation property is particularly sensitive to reservoir physical properties and fluid properties.Based on the accurate Zoeppritz equation of viscoelastic medium and the theory of medium decomposition,the authors established the characteristic equation of P-wave reflection coefficient including P-wave velocity,S-wave velocity,density and absorption attenuation parameters.Furthermore,under the constraint of Bayesian inversion framework,the simultaneous inversion of prestack four parameters was realized.The reliability of the method was verified by the trial of forward model.Finally,the method was applied to oil and gas identification in the eastern offshore exploration area of the Shengli Oilfield.Compared with things of the fluid factor based on elastic medium,the absorption and attenuation parameters obtained by the four-parameter simultaneous inversion method can more accurately characterize the distribution of oil and gas.

In this paper, an unstructured triangular grid combined with a fast Occam algorithm is used to carry out a two-dimensional joint inversion study of marine controlled source electromagnetic (CSEM) and magnetotelluric (MT) data. The unstructured triangular grid can accurately simulate undulating terrain and complex geological structures. Fine meshing is used for the inversion target area, and the other area is divided by coarse meshing, which reduces unnecessary calculations under the premise of meeting accuracy. For the purpose of realizing the joint inversion, the CSEM and MT data are assembled to the same inversion data set, and the relevant weight factors of the CSEM and MT data are constructed from the joint inversion data weight formula, which controls the fitting weights of different data. Finally, inversion calculations are performed on different models, and the results show that the joint inversion has a higher degree of recovery of seafloor structures and anomalous bodies than a single inversion, which verifies the reliability of the joint inversion algorithm.

The resistivity method can be used for the detection of near ground surface, and can also be employed to monitor dynamic underground targets. For the inversion of monitoring data, the single inversion of different data sets has certain defects. For this reason, on the basis of the traditional resistivity inversion algorithm, the time-lapse resistivity inversion formula was derived and the time-lapse inversion program was realized; for the purpose of demonstrating the superiority of the time-lapse inversion algorithm for imaging of dynamic underground targets, a set of multiple forward models was established, and the simulation data were used for single inversion and time-lapse inversion. The results show that, although both algorithms can draw the dynamic underground targets, the time-lapse inversion algorithm can eliminate random errors contained in different observation data sets and reduce the occurrence of inversion artifacts.

In the gravity survey, especially in the gravity survey of the Quaternary cover areas, it is of great significance to accurately determine the density of loose sediments for the correction, processing, inversion, interpretation and study of gravity data. For a long time, the density of loose sediments has always been determined by regular bulk sample method in the field of gravity survey. However, it is difficult for this method to obtain a regular sampling pit in field work. Therefore, there is a large error between the volume of sampling pit obtained from the calculation formula of regular shape and the volume of actual sampling pit, which leads to inaccurate measurement of density value of loose sediments. This paper presents a method which is the irregular hexahedron volume calculation method. This method is more suitable for the actual situation in the field, and can improve the traditional regular bulk sample method. This method can determine the density of loose sediments more precisely and raise the working efficiency.

Rock density determination is an important method to obtain accurate density values, and it is also an indispensable parameter for topographic correction and middle layer correction of gravity measurement results. The higher the accuracy of density measurement, the higher the accuracy of geological interpretation. However, there are different opinions on whether soaking treatment is needed before the determination of rock density in different versions of measurement specification. In this paper, we taking 12 kinds of rock (ore) specimens in Bayan Obo mining area as an example, comparing the density changes before and after soaking. It is concluded that the density of rock increases in varying degrees after soaking, except mica-type iron ore. For rocks (ores) with developed pores or fissures, the percentage of density difference after soaking is greater than 0.5%, and the density difference percentage will be greater than 0.5%. However, for the rock (ore) with dense structure, the influence of soaking on the density measurement is less than 2 times of the measurement error, which is negligible.

Helicopter TEM is widely used in mineral resources,hydrogeology and other fields.Summarizing the field survey process and analyzing the influencing factors of field survey have practical significance for future helicopter TEM flight operations.Based on the actual survey data from the two survey areas of Baiyangdian and Xiongxian in Xiong'an New Area,the authors analyzed the influencing factors in each link of the helicopter TEM field survey,investigated the model,and put forward suggestions in such aspects as the choice of take-off and landing points,the flight in different weathers,the flight height and speed,flight plan formulation,survey system stability monitoring and other aspects,thus providing reference experience for future helicopter TEM survey.

The thematic map is one of the most intuitionistic forms for presenting the research results in geophysical exploration. Nevertheless, a final result map needs to be revised and improved many times. According to the characteristics and requirements of geological interpretation map and with a section map of interpretation by electromagnetic method as an example, the authors designed and compiled an automatic drawing program by using Python language and its rich third-party libraries. In this paper, main links, such as drawing unconformity line (wave line), deleting micro-short line, polygonization and color filling are described in detail. Meanwhile, the key code are provided.

Fujian Province is located in the southeast coastal area of China, where granite is extensively exposed, which causes the fact that radionuclide is generally high in the soil, so that the environmental terrestrial gamma-radiation dose rate is higher too. In recent years, the living environment safety has aroused more and more attention, and the problem whether higher gamma radiation dose rate there is a risk has become much concern from the people. This study chose Luofang of Yong'an and Zhongdi of Wuping which are two key areas to carry out the 1∶50 000 environment terrestrial gamma radiation dose rate measurement, supported by soil samples at the same collection points. Through the study of relationship between specific activity of soil radioactive elements²³⁸U, ²³²Th, ⁴⁰K and gamma radiation dose rate, a multivariate regression equation was established. The U, Th, K test results of 31 303 surface soil samples obtained from 1∶250 000 multi-purpose regional geochemical survey in Fujian Province were converted into 2 km×2 km grid environmental terrestrial gamma-radiation dose rate in Fujian Province,so that human settlement environment suitability evaluation could be conducted.The authors have reached the conclusion that gamma radiation safety area (with no risk) in Fujian Province possesses about 121 000 km², accounting for 99.64%, the risk area (probably with some risk) possesses 433 km²,accounting for 0.36%,and controlarea (with risk) only possesses 4 km², suggesting an excellent natural radioactive environment.

1∶50 000 Gaoluji Sheet was chosen as the research object in this study. The soil elements at two sampling densities of 6 points/km ² and 4 points/km ² are similar in geochemical parameter characteristics and spatial distribution. The sampling density of 4 points/km ² in the map can meet the requirements of 1∶50,000 land quality survey and evaluation work. Based on the comparative analysis of the geochemical characteristics of soil elements under different sampling densities, the authors hold that the minimum sampling density (4 points/km ²) can be used when 1∶50,000 land quality survey is conducted in a relatively continuous farming area in the Huaibei plain coverage area. The soil environmental quality evaluation results show that the quality of the soil environment in this area is excellent. The priority is given to protecting the soil, and the safe use type soil is only in scattered distribution. The main impact indicator is Cd. The results can provide a scientific basis for the implementation of green pollution-free industries in this area.

In this study, the soil and walnut samples were taken in the main walnut producing area of Tianjin, and the content characteristics of heavy metals Cd, Hg, Pb, As, Cr, Zn and Cu in the soil were analyzed. Three methods were used to evaluate soil environmental quality in the study area, i.e., Nemerow index method, geo-accumulation index method and pollution load index.The safety of walnut samples was analyzed. The results show that the average values of Cd, Hg, Pb, As, Cr, Zn and Cu in the soil samples are 0.19×10^-6, 0.06×10^-6, 24.1×10^-6, 11.9×10^-6, 75.5×10^-6, 78.9×10^-6 and 30.6×10^-6, respectively. The average values of Cd, Hg, As and Cu exceed the background values of Tianjin, and 11.7% and 1.7% of the samples of Cd and Cu exceed the risk screening values. For the single evaluation results, Nemerow single index method shows that 10.0% of the samples of Cd have slight pollution, 1.7% of the samples have moderate pollution, and 1.7% of the samples of Cu have slight pollution. According to the method of Nemerow comprehensive index, the soil environmental quality of the study area is generally better, but according to the evaluation results of geo-accumulation index and pollution load index, it can be found that there is heavy metal accumulation caused by human factors in the study area, and the pollution points are evenly distributed in the study area. The average values of Cd, Hg, Pb, As and Cr in walnut samples are 0.003 ×10^-6, 0.004 ×10^-6, 0.044 ×10^-6, 0.043 ×10^-6 and 0.760 ×10^-6, respectively, which meet the requirements of food safety standards.

Based on geochemical investigation of land quality in northern Muchuan County of Sichuan Province, the authors identified the geochemical characteristics of Se element in the soil of the working area and carried out a study of its causes . The results show that the Se content of the soil in the working area ranges from 0.06×10^-6 to 1.49×10^-6, with an average value of 0.41×10^-6. It is mainly dominated by selenium-enriched soil, which satisfies the conditions of selenium-enriched soil and possesses 60% of the whole working area. The content of Se in different parent rocks is quite different and tends to be enriched in the surface layer. The content of Se in soils with Xiangxi Group as the parent rock is higher but the content of heavy metals is lower; the content of Se is the highest in forest land in different land use types; the difference in content of Se in different soil types is relatively small. Correlation analysis shows that the Se content of the soil is significantly positively correlated with SOM, Pb, As, Cd, etc. Different parent rocks have a greater influence on the correlation between Se content and pH, indicating that the main factors of Se content in soil are parent rocks, SOM and heavy metal elements in the working area.

In recent years, precious selenium-rich land has been discovered in Sanjiang plain, Heilongjiang Province; nevertheless, studies of the distribution and the controlling factors of soil selenium content have been rarely reported. Geochemical investigation of land quality in the western part of Sanjiang plain has revealed that the surface soil in this area is mainly sufficient, without selenium poisoning. The selenium-rich soil is mainly distributed in the alluvial lacustrine low plain area between the front of Wanda Mountain and the Naoli River, and secondarily distributed in the lacustrine denudation platform in the north of Luobei County. The selenium-deficient and selenium-potential-deficient areas mainly existalong the Songhua River and the ancient course of Luobei River in Luobei area. Based on the combination of statistical correlation analysis, factor analysis, clustering analysis and the selenium spatial distribution, the authors consider that the selenium content in the surface soil of Sanjiang plain is mainly affected by the adsorption of organic matter and clay minerals in the surface soil. Oxides of iron, manganese and other elements as well as soil pH have a relatively weaker effect on selenium enrichment.The comprehensive evaluation of soil environmental quality shows that Sanjiang plain area is mostly a risk-free area, which is a precious clean land resource. Green selenium-rich agriculture can be developed by relying on selenium-rich land.

Through the sampling and analysis of soil and crops in Sanyuan-Yanliang area, it is found that the soil environment in the study area is generally clean.The medium-rich selenium soil accounts for 94.62% of the total survey area, selenium-rich soil is widely distributed and has the basic soil conditions for the development of selenium-rich crop. It has the basic soil conditions for developing selenium-enriched foods. For the analysis of crop products, it can be seen that the bulk crops are selenium-rich crops, and the selenium-enriched level is relatively stable. Some vegetables have also reached the standard of selenium-enriched vegetables. The selenium in crops has a good correlation with soil selenium. The correlation coefficient between the selenium content of corn and that of root soil is 0.788, and the correlation coefficient between the selenium content of wheat and that of root soil is 0.612. Hence the study area has a future for the development of selenium-enriched industries. Guanzhon is suitable for vigorously promoting the cultivation of selenium-enriched crops and vegetables as an important food and vegetable. The production area has great potential for the development of selenium-enriched crops. It is recommended to select demonstration sites to carry out selenium-enriched planting work, and to focus on building a group of selenium-rich grain and vegetable industry bases so as to provide a scientific basis for the development and utilization of selenium-rich resources in Guanzhong, Shaanxi Province, thus supporting the rural revitalization strategy and the precise poverty alleviation battle.

The Geological Radar Common Middle Point (CMP) method is only used for local velocity testing. For the purpose of using a wide-angle reflection method for profiling, one radar antenna can be fixed and another antenna moves along the line of measurement to obtain the reflection signal of the entire geological interface. In this paper, the method of wide angle reflection profile detection is proposed. The relations of reflection signals are derived based on the interface of straight rock formations, and the interpretation software is developed to accurately calculate the geometric parameters and layer velocity of rock formations, so as to carry out geological stratification.

Taking the Maoping mining area of Yilang in Yunnan Province as an example, the authors used the opposing coils transient electromagnetic method (OCTEM) and the audio-frequency magnetotelluric (AMT) method to detect the development of water-bearing fault zone within 700 m below the axis of curtain grouting project, with the intention to provide guidance for curtain grouting water control project. Through the comprehensive analysis of geophysical exploration, 7 anomalies with water-rich were delineated. The results show that OCTEM method can identify small water-bearing joints or cracks, AMT method is more sensitive to large-depth water-bearing fracture zone, and the combination of the two has obvious effect on the detection of bad water-bearing geological bodies. It can be seen that the application effect of integrated geophysical exploration in curtain grouting water control is good, the deep extension of water-bearing channel is effectively identified, and the target area is provided for curtain grouting water control.

Karst development characteristics such as depth, fillings and distribution direction are key questions during geophysical survey of bridge site in Alpine gorge area. Satisfactory information of geophysical survey is not available due to influences of weathering,rock,groundwater and topography.In order to improve efficiency of geophysical exploration, shallow seismic method, audio frequency magnetotelluric method and symmetric four-pole sounding method are used for raising geophysical exploration efficiency. As a result, exploration accuracy is improved in turn, and content of exploration is verified by each other. Characteristics of apparent, macroscopic and microcosmic Karst development are obtained.Method of geophysical comprehensive exploration mentioned above can provide reference for similar projects.