Based on 1∶50 000 stream sediments survey and mathematical statistics of analytical results of 5 386 samples, the authors conducted an in-depth study of the geochemical characteristics of ore-forming elements of Qimen-Yixian area in Anhui Province. Through element geochemical characteristics analysis and R cluster analysis, the element combination was divided into three types, namely, high temperature anomaly, medium temperature anomaly and low temperature anomaly. The distribution law of combined anomalies shows polymetallic element enrichment in Qimen-Yixian area, mainly controlled by Yanshanian magmatic-tectonic mineralization system and Cambrian black rock series. On such a basis, six polymetallic metallogenic prospective areas were delineated according to geological and mineral resources features. Gold was selected as the dominant mineral, and the target deposit types are magmatic hydrothermal filling and skarn types. Anomaly verification and mineral exploration were carried out in Huanggutian, Guxi, Jinjiashan areas of Qimen County based on the results of the stream sediments survey. A batch of gold, tungsten, molybdenum orebodies were discovered, indicating that there exists great application value of prospecting in this area.

The Cuonadong Dome is located in the eastern part of the Tethyan Himalaya, within which a Be-W-Sn deposit, accompanied by a variety of rare elements, has been found. On the basis of field investigation and whole-rock geochemical characteristics, the authors discuss the elemental enrichment rules of Au, Ag, Cu, Pb, Zn, W, Sn, Li, Be, As, Sb and U in the dome, by means of geochemical clustering analysis, factor analysis and other methods, combined with the structural characteristics of the dome. Analytical results show that the dome system itself provides sufficient material sources for the enrichment of Sn, As, Be, Li, Pb and W. The dome controls the enrichment of various elements differently. The core mainly controls W, Sn ,Be and Pb. The slip system mainly controls W, Sn and Be. The capping layer mainly controls Pb, Cu, Zn, Ag and Pb elements, and the dome presents the distribution rule of high temperature (W-Sn-Se) -medium temperature (Cu-Pb-Zn) -medium low temperature (Sb-Ag) from the inner part outwards on the whole. The W-Sn-Be elements are highly enriched and large in scale, and are found to be related to pale granite and pegmatite, skarn marble as well as failure of the decollement tectonic-shear caprock.

With the deepening of the oil and gas exploration and development,geological object is becoming more and more complex.Due to the requirement of increasing the precision of seismic imaging,especially with the development of high-density and wide-azimuth and wide-band seismic exploration technology,the direction of anisotropy is more and more prominent in the seismic data processing.However,the conventional Kirchhoff prestack time and depth migration uses both offset gathers,the angle gathers information fails to be retained and therefore it is unable to meet the demand of the current seismic processing.By way of full wave field and multipath,full azimuth migration imaging applies all seismic data in a continuous manner in underground local angle domain and generates two complementary full azimuth direction angle gathers and full azimuth common refection angle gathers.Fairly good application effect has been achieved in the migration imaging of Nanmazhuang buried hill tectonic belt,as shown by the facts that the imaging accuracy is improved,the geological phenomena is clearer,and the prediction of fracture density and development direction is more reliable.

Based on the aeromagnetic data of the latest high precision of 1∶50 000 and the existing gravity data of 1∶200 000 in 2016 in the southwestern margin of Ordos Basin, data processing was carried out. 1crust fault, 11 basement faults,3 cap rock faults and range of the southern central uplift. Using joint inversion of gravity and magnetic data the depth and thickness of basement and cap rock is roughly understood. The analysis indicates that the gravity field mainly reflects the difference in density between the Ordovician and its overlying sedimentary cover, and the magnetic field mainly reflects the structure of the crystalline substrate. Combined with joint inversion of gravity and magnetic data, the top surface depth of the Ordovician system and the crystallographic basement depth were extracted respectively using gravity data and aeromagnetic data by Euler deconvolution and source parameter imaging, and the basement lithofacies were studied. All that provided an important basis for the prediction of oil and gas in the area. The study believes that the use of high-precision aeromagnetic data combined with gravity data can identify base features effectively and make up for the lack of other geophysical data.

The H exploration area is located in the northeast of the Tulu-Tuomatan basin.Its geomorphology is desert and gobi.The climate in the area is dry,the plants are poorly developed,and the ecological conditions are very fragile.The surface is dominated by gravel and sub-sand layers,its thickness is large and the latent water level is deep.The choice of reasonable acquisition technology and parameters is the premise of seismic work and the key to ensuring seismic exploration results.Firstly,the feasibility of using vibroseis in this area was analyzed according to the seismic and geological conditions of the exploration area.Then,the selection of the vibrating parameters of the vibrator was tested,and the excitation parameters such as vibration number,scanning length,scanning frequency,and source output were determined.Referring to the experience of seismic exploration in adjacent areas,the authors chose the linear combination of multiple geophones and the observation system with high coverage times.The vibroseis technology was adopted,the selected acquisition parameters were finely constructed,and the better seismic effect was obtained,which provides valuable reference for the future seismic exploration of coal fields in similar areas.

There is a promising exploration potential in Changxing Formation of Puguang area,northeastern Sichuan Basin.In this paper,the authors made a comparison of the growth pattern of reef between Puguang area and Yuanba area,conducted an analysis of the geological features of reef and reservoir and drew a summary on vertical and horizontal distribution law of reef dolomite reservoir.On such a basis,a reef seismic forward model was established to obtain the identification mode of seismic facies using logging and seismic data.In order to avoid the interference from marly limestone,the authors predicted favorable sedimentary facies belt of reservoir growth using palaeogeomorphology analysis and picked an appropriate time window for reservoir prediction.Finally,the authors used seismic facies reading,attributive analysis and wave impedance inversion to accurately predict the effective reservoir distribution.So a seismic prediction method for reef reservoir in Puguang area was established and the reef reservoir distribution in Puguang area was predicted quantitatively.The prediction result indicates that the reservoirs mainly occur on the reef cap in vertical dimension and on a narrow belt along the platform margin in horizontal dimension.Meanwhile,the congruence between prediction result and well data confirms the effectiveness of the proposed method.

Bashenghe is located in Chaihe Basin, Da Hinggan Mountains uranium metallogenic belt. Previous research on uranium prospecting has been very insufficient. Based on an analysis of the characteristics of airborne gamma-ray spectroscopy of typical regional uranium deposits, the authors established the anomalous indicators of airborne gamma-ray spectroscopy in regional volcanic-type uranium mineralization areas: high-value field of uranium, high-value halo of uranium increment (Delta U), low-value halo of active uranium (Hu), and high-value halo of airborne F-parameter. In terms of these features, the airborne gamma-ray spectrum data of the study area were processed effectively, then anomalous characteristics were analyzed, and five airborne comprehensive anomalous halos were delineated. Combined with stratigraphic, structural and geophysical and geochemical conditions, the uranium metallogenic potential of the five airborne comprehensive anomalous halos was studied. Finally, the integrated anomalous halos formed by H01, H02 and H03 in the study area was found with good volcanic uranium metallogenic potential.

Seawater intrusion is one of the problems facing coastal countries and regions, and is also one of the major geological disasters in the Beibu Gulf economic zone. In this paper, based on systematic research on previous researches on Beibu Gulf region of Guangxi and using EH-4 audio magnetotelluric method int Beihai City, the authors made a preliminary study of the present situation of seawater intrusion, salty-fresh water dividing, and features of water-containing strata in the study area. It can be seen that, through the coastal city environmental geological survey work and by using reasonable geophysical detection methods and taking the preventive measures, the problem of seawater intrusion in coastal areas can be solved effectively. The authors' work has also confirmed that the EH-4 audio magnetotelluric method has a good effect in the investigation of seawater intrusion in the research area, and hence deserves wide application.

This paper describes a realization method and hardware dynamic loading process of pseudorandom signal mixed coding based on x×a ⁿ and y×b ⁿ sequences and its application to gas fracture detection in Weiyuan of Sichuan Province. By using the mixed coding method of pseudorandom signals based on x×a ⁿ and y×b ⁿ sequences, researchers can design pseudorandom signals that satisfy combination of pseudorandom encoding rules, encode waveforms and generate code streams automatically. The dynamic loading technology based on this coding can load large, long and complex composite pseudorandom signals, thus providing a convenient and universal technical method for the application of multiple pseudorandom signals.

Capacity prediction is a key step in oilfield production.It is difficult to predict reservoir capacity quantitatively.Therefore,the classification of reservoir capacity is usually carried out first to provide a basis for quantitative prediction of reservoir capacity.By analyzing the factors affecting the reservoir capacity in the Huizhou depression of Pearl River mouth basin,191 core capillary pressure curves which can reflect the petrophysical characteristics of reservoirs were used to classify reservoirs into three categories.Then,through combining reservoir classification with capacity classification,the classification limits of reservoir oil production index per meter were determined as 12 and 2 m ³/(d·MPa·m).The comprehensive evaluation index Z,which combines the macroscopic and microscopic physical parameters of the reservoir,was used to divide the reservoir capacity,and finally the reservoir quality index was used to identify the reservoir capacity category of the whole well.Using the capacity classification and identification method,the authors divided the capacity categories of all test sites in the study area,with the accuracy rate over 90%.The method has a good application effect and deserves promotion.

Geomorphology of Guizhou Province belongs to the plateau mountain area of southern China, where the terrain undulates greatly, regional carbonate rock is widely distributed, there exist towns, roads and other human interferences, and geological structure is complex. Therefore, it is difficult for conventional methods to obtain good exploration results. With the utilization of wide field electromagnetic method in Ziyun area of Guizhou Province, the distribution range and buried depth of the deep shale series were basically determined, and the fault characteristics in this area were detected, which provided the geophysical exploration basis for the drilling arrangement. The results were verified by drilling, and good exploration results were obtained. The case study shows that the wide field electromagnetic method is suitable for exploration in carbonate rock area of complex terrain, and it is an effective method for deep exploration.

The hydrogeological conditions in karst mountainous areas are complex, and the distribution of groundwater may have different response characteristics to different geophysical methods. In this paper, the high density resistivity method and audio magnetotelluric method were synthetically used to study the application of groundwater exploration in Changtang Village, Huaihua area. The comprehensive exploration results are better indicate the anomalous characteristics and specific anomalous locations. The inferred results are basically consistent with the drilling results, and the maximum water inflow is greater than 146.88 m ³/d。The study results show that symmetrical four-pole sounding inversion can effectively respond to the changes of underground transverse resistivity, and the resistivity sounding curve (single branch curve) can be used to make stratification vertically, the results of stratification are basically consistent with the results of drilling.The audio magnetotelluric method has a large detection depth and can effectively respond to subsurface fault structures.

Based on the survey of soil radon gas and gamma spectrum in the Michurinskoye uranium deposit in Central Ukrainian U province, and the comprehensive comparative analysis of the existing regional gravity, magnetic, seismic and logging data, the authors used various geophysical exploration techniques to evaluate the existing orebodies rapidly and effectively. On the basis of the analysis and study of ore-controlling structures in tectonic alteration zones, the authors constructed the identification technology of deep uranium metallogenic information and the comprehensive technology of deep uranium resources exploration and evaluation for hydrothermal uranium deposits, and provided theoretical guidance for the prospecting of alternative resources in similar mining areas and crisis mines.

Sparker is an important equipment for marine seismic exploration technology. It not only is environmentally friendly,safe and low-cost to use,but also has broad frequency advantages for data,which can improve the resolution of seismic exploration.However,in the early stage of its development,there existed some problems such as unstable signals and shallow penetration depth,which caused its development speed to slow down or even to be replaced by air gun source.Later,with the rapid development of electronic technology and data processing level,these problems have been solved very well,and it also has attracted people's attention once again.This paper reviews the development of sparker source hardware and data processing methods,summarizes the problems existing in the process of sparker source development,expounds the application effect of sparker source used by previous researchers,proposes a solution from the data processing,and predicts the future and important developing direction of the sparker source in marine seismic exploration.The authors hold that sparker source will play a much more important role in marine seismic exploration and this will have significant studying meanings for the improvement of marine seismic exploration,sparker source hardware and source data processing methods.

The reliable detection of data outliers and unusual data behavior is one of the key task in the statistical analysis of applied geochemical data, and has remained a core problem. Factor analysis is a multivariate statistical analysis method, which is used to solve the problem of complex geological origin and superimposed mineralization; nevertheless, geochemical data are compositional data, there exist their closure effects, closure has a major influence on the covariance and correlation matrices, the very base of principal component analysis (PCA) and factor analysis (FA). So the authors applied isometric logratio-transformed (ILR) to 'open' the data before FA. The study area is located in the east of East Kunlun polymetallic mineralization zone. The authors used ILR transformed 11 major elements to conduct FA, extracted four public factors and calculated the four factor scores. According to the results of FA with EDA method , the authors standardized geochemical data and delineated Au anomaly. Compared with traditional method, this method can eliminate the influence of high background values.

Factor analysis and fractal modeling were combined to study the 1:50000 geochemical data of Heiyingshan, Inner Mongolia, so as to recognize ore-induced geochemical anomaly. First, sample factor analysis of 10 elements mainly includes three factors: F1 consists of Zn-Cd-(Cu), F2 consists of Ag-Mo-Cu-Bi, and F3 consists of Sn-As-Pb-Sb. Second, the F2 factor score is further modeled by Concentration-Area (C-A) factor model. The fractal fitting lines of four segments were obtained from the log-log graph of Area-F2 factor score, which represent "low background area without prospecting potential", "background area", "high background area" and "high prospecting potential area", respectively. In the subsequent prospecting work, several mineralizations and alterations were found in the "high prospecting potential area". Some conclusions have been reached: F2 factor reflects the hydrothermal metallogenic process and can be used as a comprehensive index for the spatial aggregation of major metallogenic elements in the study area. The C-A fractal model can accurately delineate the boundary of F2 factor "high metallogenic potential area". The "high metallogenic potential area" can be used as the basis for delineating the prospecting target.

Gravity gradient tensor is the second derivatives of gravitational field. Compared with the traditional gravitational exploration, gravity gradient tensor can reach a better resolution. Gravity gradient tensor has 5 independent components, so they can contain more geological information. Therefore, gravity gradient tensor can be used to recover the causative bodies in the subsurface with high accuracy. Due to strong adaptability and flexibility of the unstructured grid, it can smoothly approximate the irregular and complex boundaries of anomalous source. Compared with the structured grid, the unstructured grid can provide researchers with more accurate discretization and calculation with less computation time. In order to reduce the ambiguity of the inversion, the authors chose to jointly and simultaneously invert all gravity gradient components based on tetrahedron grids with the help of the so called generalized objective function which is widely used in geophysical inverse problems. The authors applied the algorithm to each gravity tensor component at the beginning to ensure that the depth weighting function makes a difference in the inversion. It turns out that the depth weighting function works well. To explore all components of the gravity gradient tensor as much as possible, the authors described the joint-inversion in detail in this paper. The inversion results show that 3D inversion of gravity gradient tensor based on unstructured grids can obtain the position of causative bodies in the subsurface and the density distribution. Based on a comparison with rectangular grid inversion results, the authors highlighted the advantages of unstructured grid inversion. And the practicability of the method was verified through two synthetic models.

In the exploration and development of oil and gas reservoirs,the in-situ stress is closely related to the distribution of fractures,while fracture is an important channel for migration and accumulation of oil and gas,so the study of in-situ stress is of great significance for oil and gas development.In this paper,tight sandstone was taken as the research object.On the basis of the transverse isotropic rock layer model and in consideration of the complexity of sand and mud layer stress changes,the formation was assumed to be orthotropic,the elastic parameters of the inverse elastic impedance were taken as the background field of the working area,then the anisotropic parameters in orthotropic medium were obtained,and the ratio of differential stresses was calculated.The anisotropic impedance equation was used in this study,and the elastic parameters and fracture flexibility parameters were converted into anisotropic parameters,in order to verify the accuracy of the prediction method for the in-situ stress of tight sandstone;the ratio of differential stress calculated under the orthotropic model was compared with the results of the same log calculation and various characterization methods.It is shown that the results of geostress calculated under the assumption of orthogonal medium model are basically the same as those calculated by various control methods,thus proving that the orthotropic model stress prediction method is applicable in sand and mudstone formations,and has a good guiding significance for the exploration and development of low permeability oil and gas reservoirs in the future.

Compaction is the only consideration for 'velocity-depth' linear model of sedimentary strata.With the velocity spectra data along a multi-channel seismic profile in deep-water area of South China Sea basin and by applying the 'velocity-depth' linear model to the interpreted data of the profile,the authors obtained direct results for geological interpretation.In addition,through the creation of visual workflow and the consideration of horizontal variation of sedimentary interval velocity within the depth conversion procedures,the authors made the results of depth conversion more reliable.In the end,the authors gave a discussion on the limitation and further application of 'velocity-depth' linear model both from theory and practice,which deserves consideration in further work.

According to the observation mode, Controlled Source Audio-frequency Magnetotelluric Method (CSAMT) can be divided into scalar CSAMT and tensor CSAMT. Due to the difference between the construction method and the resistivity calculation method, the minimum transmission and reception distance in the division of far-field of the scalar CSAMT cannot be accurately applied to the tensor CSAMT. According to the relative errors of tensor apparent resistivity and Magnetotelluric (MT) apparent resistivity, the relative errors of the homogeneous geodetic model and the two-layer model were calculated respectively, and the minimum transmission and reception distances under different error limits was accurately given. The results show that, for the two-layer model, when the thickness of the first layer is less than 3 times the skin depth, the result of homogeneous half space cannot be directly applied, which causes a large error for the G-type model. Multilayer results can be approximately evaluated from the two-layer model with equivalent resistivity . The research results in this paper have certain theoretical guiding significance for the tensor CSAMT field construction.

In order to apply the method of multi-channel analysis surface wave (MASW) to geological survey,the authors studied multi-channel transient surface wave data acquisition in loess plateau.The effect of some acquisition parameters,such as different excitation sources,number of receiving channels,station intervals and the minimum offset,on the record quality of the data was analyzed.In addition,the suitable data acquisition method and parameters for the loess plateau were pointed out.The processing results of the actual data reflect the velocity structure and the loess type characteristics in the near surface of the work area,which indicates that the selection method of the data acquisition parameters is reasonable,which lays a foundation for the application of MASW in the geological survey in the loess plateau area.

This paper gives an account of the development and application of the aeromagnetic measuring system of a power glider equipped with cesium optical pump magnetometer. The model selection, support modification, magnetic interference elimination, aeromagnetic system integration and other aspects are fully studied, and the integrated aeromagnetic system performance indexes are tested. On the whole, the indexes accord with the technical specification for aviation magnetic survey DZ/T 0142-2010 (hereinafter referred to as the aeromagnetic specification) requirements. The production operation was conducted, and a comparison was made between the aeromagnetic survey results and the previous aeromagnetic results; an analysis was conducted in the aspects of economy, applicability and green environmental protection. It is shown that the system is an effective method in the low-level aeromagnetic survey, and the use of the system to carry out large scale aeromagnetic survey and geomagnetic survey has obvious advantages.

Aeromagnetic anomaly data constitute one of the most important achievements in aeromagnetic work. It is the qualitative analysis of obtained aeromagnetic data via evaluation and interpretation. In order to meet the need of cartographic representation of final production map compiled by researchers in specific project, cartographers need to render the same data several times via different attributes. An Oracle database must be built as the unified storage and management platform so that the airborne geophysical data and information service can be provided efficiently. The authors investigated the mapping requirement of aeromagnetic anomaly and, in combination with management of Oracle database, constructed an auto-renderring model for aeromagnetic anomaly data. Then the authors implemented secondary development of auto-renderring workflow using C# language based on ArcEngine. Tests based on database data have validated that the results meet the standards. Now standardized API interfaces can be provided for other software development.

In order to accurately obtain the information of the joint surface which hides inside the rock mass and the floating soil cover, the authors employed the geological radar detection technology, established the trigonometric function measurement formula of the true and apparent dip angle as well as inclination and length of the joint surface and obtained he accurate solution of such pieces of information as attitude and length. Using wet wood-fine sand indoor model test, the authors verified the rationality of the theoretical solution.

In this study, 91 sediment samples were collected from the middle and lower reaches of Liujiang River. The geochemical characteristics of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and other elements were analyzed. The current pollution situation and potential risks were predicted and evaluated, and the sources of heavy metals were analyzed. The results show that: The spatial dispersion of elements in the sediments of Liujiang River Catchment is relatively large, and the distribution of heavy metal elements shows strong regional characteristics.Distribution of heavy metal elements in Liujiang River Catchment shows strong regional characteristics.As, Cr, Cu, Hg and Ni are mainly from natural sources, while Cd and Pb are mainly from human sources. The high-value areas of Cd natural source contribution mainly distribute in Longjiang River Catchment, while the high-value areas of industrial and mining sources contribution mainly distribute around Jincheng River and Liuzhou District of Liujiang River.

Through systematic sampling and analysis of soil and crop samples in Nomhon oasis agricultural area of Qaidam basin, Qinghai Province, the geochemical characteristics of selenium, source of selenium, ecological effects of selenium-enriched Lycium barbarum and its development and utilization prospects were identified. The results show that the selenium-rich soil area is 413.6 square kilometers, and the selenium content ranges from 0.23×10 ^-6 to 2.8×10 ^-6, with an average of 0.47×10 ^-6. Selenium-rich soil is alkaline with rich fertility elements and clean soil environment. The source of soil selenium in the study area is Quaternary lacustrine sediments, and the salinization, soil particle size and organic matter content have significant effects on the migration and enrichment of selenium. Wolfberry in Nomhon is clean and pollution-free and has a high proportion of rich selenium, which has a significant positive correlation with soil selenium, and has a great prospect of exploitation and utilization.

Fluorine is a necessary trace element for human beings, and lack or excess of fluorine will exert adverse effects on human health. In this paper, the geochemical characteristics and environmental quality of fluorine in soil, groundwater and crops in Jizhou district of northern Tianjin were studied. The results are as follows: The fluorine content in surface soil ranges from 201×10 ^-6 to 8545×10 ^-6, with an average of 757×10 ^-6. The average content is 1.25 times the background value of surface soil in Tianjin and 1.58 times that in China. In the vertical profile of soil, the fluorine content is higher in cohesive soil than that in sandy soil. The average fluoride content of groundwater in plain area is 1.50 mg/L and that in mountainous area is 0.47 mg/L. The fluoride content in plain area is obviously higher than that in mountainous area. Over 90% of the surface soil fluoride content in the region is excessive and high, and the proportion of groundwater samples of fluoride IV and V in plain area reaches 61.54%. The proportion of fluorine exceeding the standard in maize samples is 26.67%, with the maximum exceeding multiple over two times. Generally speaking, the fluorine content in surface soil and groundwater in the plain area of northern Tianjin is significantly higher than that in the high fluoride area. The fluorine content in some agricultural products has exceeded the standard, to which more attention should be paid by the relevant departments.

The dam failure and leakage risk of tailings dam are directly related to the safe operation of tailings pond, which is an important environmental safety problem. In this paper, the authors used the high density resistivity method to detect the two-dimensional fine section of tailings dam, and found four weak areas of tailings dam structure. Since the leakage is mainly caused by the movement of groundwater, monitoring studies were carried out for three times on the tailings dam before and after the rainy season and, as a result, the dynamic response of the electrical structure of the dam body was obtained, with a suspected dew point determined. The feasibility of application of high density resistivity method to the tailings dam monitoring was verified, and the result provides a new technical means for tailings dam stability study.

Goaf tends to cause land subsidence and threaten the safety of power grid operation. It is of great significance to detect the distribution of underground goaf. Traditional goaf electrical detection technology has complex control system and complicated survey line arrangement, needs many sensors and cables as well as large amounts of measurement data, and is characterized by inefficient layout and mobile measurement, and hence it is not suitable for the use of electric power field to prevent and control the hazards of underground goaf. In view of the distribution characteristics of goaf under power pole and tower, the authors designed an electrode system for goaf electrical detection. The centralized-istributed detection method can effectively reduce the number of sensors and cables for goaf detection under power pole and tower, optimize the system control, simplify the effective detection data and improve the efficiency of goaf detection.