The crucial precondition of using spectral attributes to conduct hydrocarbon detection is to investigate the spectral differences between gas-bearing and none-gas bearing area.In order to determine the spectrum difference between hydrocarbon bearing and none-hydrocarbon bearing areas intuitively and incorporate the constraints of oil and gas production testing data,this paper proposes a hydrocarbon detection technology based on spectrum difference,which divides known wells into hydrocarbon-bearing wells and non-hydrocarbon bearing wells according to the actual oil and gas production testing data and research needs.By comparing the instantaneous amplitude spectral of pay zones of classified objects,researchers can recognize spectral differences related to hydrocarbons and use the intersection of multiple spectrum attributes to characterize the differences so as to obtain the seismic hydrocarbon-bearing areas that could be identified.The maximum trough amplitude was determined as the relative advantage attribute to recognize the reservoir information of the H1 member according to the forward modeling contrast between presence and absence of underlying coal seams.More in-depth analysis shows that the spectrum difference can better forecast hydrocarbon-bearing and hydrocarbon-absent zones than the maximum trough amplitude.The differences of spectral attributes between hydrocarbon-bearing areas and non-hydrocarbon bearing areas was quantified by setting attributed threshold value,and the spectral attributes in individual thresholds of the four spectral attributes were crossplotted to dentify the potential hydrocarbon bearing areas.The hydrocarbon dictation results are supported by horizontal wells,which indicates the method is reliable.

Eastern Hebei Province has very rich mineral resources;nevertheless, the past prospecting work was focused only on iron and gold deposits,whereas the attention to tungsten deposits was very insufficient.Based on 1∶25 000 soil geochemical survey,the authors conducted detailed soil geochemical survey in the Liangjiayu areaof Hebei Province.Through studying element distribution characteristics,individual element anomaly features,element correlation,and comprehensive anomaly setting combinational anomalies of related elements,the authors determined Au and W as the target ore species elements in the study areaand delineated further prospecting areas.

Non-seismic methods have been proved to be effective in geothermal exploration.This paper describes a two-step method for investigating the geothermal potential in Fountain Village,Rongsheng,Qihe,Shandong Province.The geological background of the target area is very complicated;for instance,many complex faults are developed and the formations usually have strong horizontal anisotropic property,which enhances the difficulty of exploration.The two-step method put forward by the authors utilizes the electrical and elastic features in different formations to solve these difficulties.The first step is to investigate the location of huge fault structure and the depth of resources by using electromagnetic method,which can locate the water-rich regions.The second step focuses on the more precise features of faults based on microtremors method. This method can help locate the sweet spot area more accurately and bring constructive suggestions to well location determination.Drilling results have testified the feasibility and applicability of this two-step method,which opens up a new path in complex geothermal exploration.

This paper briefly introduces the principle of aeromagnetotelluric method, the measurement system, the calculation of tiltepper parameters and the two-imensional and three-dimensional inversion. By using the forward program, the tipplter parameters of the geoelectric model of the transverse electrical interface were calculated. The results show that the tilter data obviously reflect the transverse electrical interface. Finally, combined with the actual geological situation, the distribution characteristics of rock mass and ore-control structure in the area were found by using the measured tilter and inversion resistivity data, and some results were obtained, which verify the feasibility of the method.

Haoran Qaidam region is located in the western part of Hanggin Banner. According to the analysis of previous work, there exists great potential for prospecting in the lower Cretacteous Huachihuanhe Formation. Based on CSAMT sounding data obtained along five lines in 2019 and combined with geological and drilling data, the authors analyzed the sand body development characteristics of Huachihuanhe Formation. The research results show that the sand bodies in this area are well developed and widely distributed, with a roof buried depth of about 200 m, a thickness of 400~700 m, a local thickness of 750 m, and a NW strike. The overall development and distribution characteristics are thin in the northeast and thick in the middle southwest. The result obtained by the authors provides deep geological information for the layout of drilling projects.

The carbonate karstic-fault oil-bearing reservoir is rich in oil resources storage,and large karst caves and fractures are the main reservoir space and flow channels.There are mud leakage and hole collapse in the drilling process,so it is difficult to carry out conventional logging measurement,and reservoir evaluation or even reservoir depth (i.e. oil source location) can not be determined.Temperature curve is often used in production logging,and it is not affected by borehole condition and it can reflect the depth of the reservoir.Based on the morphological characteristics and size of karstic-fault reservoir,the authors constructed the geometric models of wellbore,formation,fracture and cave,and simulated the variation of wellbore temperature in the production of karstic-fault reservoir by numerical simulation method.The simulation results were analyzed,and then the oil source depth of karstic-fault reservoir was estimated by well temperature curve,which provides technical support for further development of karstic-fault reservoir.

In this paper,the first arrival wave time field of imaging area is obtained by solving the Eikonal equation by using wavefront expansion extrapolation method.The full plane migration imaging of prestack data of complex model is performed by using Kirchhoff integral migration technique.The imaging results show that the inversion method of curve ray tomography describes the anomaly velocity body more accurately than straight ray tomography result.Better migration imaging results can be obtained by using the velocity field inverted by curved ray tomography.

The affine time-frequency analysis method has the characteristics of fuzzy instantaneous spectral changes,highlights the characteristics of the main frequency variation trend,and has a good capability for determining the degree of cycle.Therefore,it has been used by experts in the classification of cyclic thin interbed types.The layer time domain waveforms are characterized by dense waveforms toward the thin layer and sparse waveforms in the thick layer direction,but their poor stability is susceptible to external interference.The time-spectrum obtained from the affine class time-frequency distribution has a one-to-one correspondence with the sedimentary cycle pattern.The frequency rising characteristics of thin interbeds in different model cycles are in the direction of thickness thinning.As the study of the influencing factors of cyclic interbeds characteristics in the current time is very insufficient,it is important to clarify the influence of these factors on the criterion of the cycle.Based on the above considerations,this paper discusses the influence of the sudden change in the thickness of the small layer,the size of wave impedance,the influence of noise,the size of seismic data frequency and the viscous absorption of the formation on the cycle discrimination based on the positive cycle model.Firstly,according to the wave theory,the depth-domain phase-shift method is used to make forward simulation of the cyclic thin interbeds with different influencing factors,and zero-offset gathers is extracted for affine time-frequency analysis;after that,the differences of time-frequency characteristics of cyclic thin interbeds are compared under ideal conditions.The results show that affine time-frequency distribution has a strong capability for discriminating sedimentary cycles against noise,and is less affected by slight sudden changes in the thickness of thin interbeds,that the variation of wave impedance mainly affects the temporal energy distribution of time-frequency spectrum,but has little effect on the energy distribution of frequency-direction,and that the variation of main frequency of seismic data has little effect on the time-frequency characteristics,whereas the variation of main frequency of seismic data has little effect on the time-frequency characteristics.With the increase of main frequency of wave,the trend of cycle is more obvious,the influence of stratigraphic viscous absorption on the accuracy of this method is also small,and the time-frequency characteristics are stable.

The Xihu sag is the largest oil-bearing sag in the East China Sea.The main reservoir of the Xihu sag is located in the middle and deep strata.Adding low frequency information is one of the core issues for solving the main geological problems in the Xihu sag.The variable-depth streamer acquisition technology can effectively suppress ghost waves,broaden the frequency band,especially the low frequency,and has the advantages of simple field operation and low cost,which is beneficial to solving the geological problems of the Xihu sag.Based on the average ghost filter of variable-depth streamer,the key acquisition parameters are theoretically analyzed,such as streamer mode and the streamer depth range.Through 2D field test,a further comparative study was carried out on the raw shot and PSTM record.It is concluded that,for the deep reservoirs of the Xihu sag,the variable-depth streamer is more clearly structured than the conventional horizontal streamer data,and the frequency band has been broadened. Among the two commonly used streamer modes,the linear streamer has better notch compensation effect,and the parabolic streamer has higher low frequency energy.When the shallowest depth of the variable-depth streamer is fixed,increasing the depth range is beneficial to obtaining more low frequency information.

X ray fluorescence spectrometry (XRF) is one of the important methods to test the homogeneity of geochemical reference materials, but there is still controversy about the application. The homogeneity test requires the prerequisite that the sample weight is the minimum. The result of homogeneity test using conventional powder tableting or melting samples by XRF is generally larger than the minimum sample weight, so the results obtained are not theoretically sufficient to support the homogeneity of the sample under the condition of minimum sample weight. In this study, the 0.1 g samples experienced melted preparation with a mixed flux of Li₂B₄O₇ LiBO₂ and LiF (mass ratio 45∶10∶5) and NH₄I release agent. The authors established an experiential method to analyzetotally 10 measuring components, i.e., SiO₂, Al₂O₃, TFe₂O₃, MgO, CaO, Na₂O, K₂O, Mn, Ti and P. The correlation coefficient of the calibration curve of each component was between 0.997 3 and 1.000 0. The experimental optimization results of sample preparation conditions showed that the ratio of sample to mixed flux was 1∶4, 2 drops of 0.2 g/mL and ammonia iodide were used as the mold release agent, melting at 1 050 ℃ for 10 min., leading to the best molding effect. The method parameters were studied. The relative standard deviation of each component was 0.2%~5.3 %, and the relative error was less than 6.2%. The method precision and method accuracy were high. Compared with the conventional sample weighing of 0.65 g, the experimental results of the two methods are consistent. This study provides the basis for the application of X ray fluorescence spectroscopy to the homogeneity test of geochemical reference materials.

The field seismic data are disturbed by various random factors,and hence it is necessary to remove the random noise from seismic data.The soft and hard threshold functions of wavelet transform are effective methods for seismic data de-noising;nevertheless,due to the characteristics of the algorithm itself,their de-noising performance has some defects.In view of such a situation,the authors propose an improved wavelet threshold method for de-noising.Firstly,the improved wavelet threshold method is constructed and some of its functions are studied.It is shown that the best wavelet basis of the improved threshold method is sym3,and the best decomposition level is 3.The effect of the new algorithm in de-noising is evaluated by means of mean square error (RMSE) and signal-to-noise ratio (SNR).The proposed method was applied to the actual seismic data de-noising.The results show that the improved threshold method can effectively remove all kinds of random noise of seismic data.A comparison with soft and hard threshold method shows that the improved threshold method has a better effect in seismic data de-noising.

Amplitude gain control is widely used in seismic data processing and interpretation.Based on an analysis of the shortcomings of conventional amplitude gain control (AGC),this paper presents an amplitude gain control method (envelope AGC) based on Hilbert transform.The basic principle is to decompose the amplitude envelope of seismic trace,get the normal amplitude and abnormal amplitude,then extract and add the abnormal value components to the normal value components by weighting,and finally conduct inverse transform to t-x domain to realize envelope AGC.The application results of actual seismic data show that the envelope AGC is realizable and has certain practical application value.

A service system for magnetotelluric data sharing is proposed to solve the management and sharing of magnetotelluric data.This paper discusses the cloud architecture design, function design and other aspects, focusing on the integration of electromagnetic operations such as phase diagram in the system. Finally, a prototype system is built based on the electromagnetic data of Nima basin. Compared with the traditional sharing system, the interface of this system completely follows the "geological cloud" standard, which provides the premise of exploration practice for the magnetotelluric thematic service in the "geological cloud" sharing.

In order to analyze the effect of suppressing background noise of the vibroseis vehicle,the authors,based on the working principle and cross-correlation theory of the vibroseis,simulated calculation of the reflected signal generated by the geological model by adding random Gaussian white noise and actual road traffic interference noise.The results show that the vibroseis can suppress random noise equivalent to 27~81 times the reflected signal strength or 5~27 times of actual road traffic interference noise from single excitation to 8 repeated excitations.The engineering seismic exploration example shows that,in the context of strong urban traffic interference,the vibroseis can be used as the excitation source,and both the exploration accuracy and the exploration depth can meet the engineering needs.

When exploration of the deep electrical structure of the earth's crust and mantle scale is conducted. LEMI-417 long-period magnetotelluric sounding instrument is a prevailing system for continuously observing natural electromagnetic field. In this paper, through in-depth study of the original binary data structure of the system, the authors analyzed the corresponding data structure in C++ computer language and also listed the core program code so as to provide necessary support for researchers who are engaged in the research on deep earth exploration and signal processing in electromagnetic field.

Deep well natural electric field observation is an effective means to monitor the geological activities in the deep earth, and is of great significance to the prevention of earthquake disasters and the exploration of deep resources. In general, the ground electric field signal is a weak electrical signal of the mV level or even the light V level. As a non-polarized electrode of the electric field sensor, its performance will have an important impact on the measurement results. The existing non-polarized electrode works mainly on the principle of electrochemistry, but in the deep well, the high temperature, the acid corrosion and other harsh conditions exist. According to electrochemical theory, factors such as high temperature and acid corrosion will severely impact the performance of non-polarizable electrode. In order to make high temperature and acidic environment inspection of wells of non-polarizable electrode and the suitability of the principle of electrochemical non-polarizable electrode to deep well measurement and the related experiment, the authors selected three kinds of electrodes and tested them under simulated conditions of deep well testing. The results show that the principle of electrochemical non-polarizable electrode electric field measurement is not suitable for deep well environment, graphite electrode performance is stable, and graphite substances are suitable electrode materials for deep wells.

The input flux of Se in farmland soil of 9 counties in the middle east of Guangxi were studied. By integrating various factors, the authors took the atmospheric wet and dry depositions as the main input way of Se. The average atmospheric wet and dry deposition flux in the whole study area is 6.36 g/(hm²·a), the irrigation water input flux possesses the second position, whereas the fertilization input flux is obviously lower. They account for 70.93%,27.35% and 1.72% of Se in soil respectively. Their proportions are somewhat different among 9 counties of the study area: the contribution of the atmospheric wet and dry deposition is the highest, accounting for more than 50%. Therefore, the atmospheric wet and dry depositions seem to be the main input ways of Se in the study area. The regional differences of Se input flux and the proportion of different input routes in the study area are basically consistent with the total amount of As, Cd, Cr⁶⁺, Hg and Pb in the field soils. These data show that the inputs bring in not only the beneficial element Se but also a certain amount of heavy metals. Therefore, the pollution of heavy metals in soil caused by the inputs should be strictly prevented and controlled.

Nanchuan District is a typical agricultural area in Chongqing. The authors investigated the geochemical characteristics and influential factors of soil Se from Nanchuan District of Chongqing City to provide some scientific bases for the survey of environment background and regional production as well as human health. More than 8 496 soil samples from the topsoil layers(0~20 cm)all over the Nanchuan District were collected and analyzed for content and distribution of soil Se and their relationships with parent material, soil properties (pH and Corg), altitude and human factors. The research results show that the content of total selenium ranges from 0.056×10^-6 to 10.80×10^-6 with a mean value of 0.46×10^-6, which indicates that the most of the soils are in the category of Se-sufficiency to Se-abundance, with 42.31% being Se-enrichment. The spatial characteristics of soil Se content in Nanchuan District show "high in the south and low in the north", and the soil Se enrichment areas are mainly distributed in Shuijiang Town, Nanping Town, Nanchuan urban area and Jinfo Mountain. Among the types of soils existing in the Nanchuan District, Se content is the highest in industrial and mining land soil and the lowest in farmland. The spatial characteristics of soil Se content and strata show a similar variation pattern. The soil Se enrichment is mainly distributed in Permian, Triassic (Feixianguan Formation and Jialingjiang Formation), Silurian, Ordovician and Cambrian strata, which indicates that the soil Se content is mainly controlled by parent materials in Nanchuan District. In addition, Se content in soil is significantly positively correlated with soil organic matter and altitudes, but significantly negatively correlated with soil pH.

Dry and wet atmospheric deposition is a main input pathway of some elements in the surface soil of agricultural areas, and its heavy metalelementcomponents mayhave a great influence on the environmental qualityof soil. Research on the dry and wet atmosphericdeposition of Juye County in Shandong Province shows that, with the rapid development of coal mining and chemical industry in recent years, total amount of dry and wet atmospheric deposition has been significantly increased in this area, and is also significantly higher than that of several other regions of China.The deposition flux of heavy metal elements in this region is also higher,the deposition fluxes of Pb, Cr, Cu, Ni can be 2~ 3 times those of other regions inChina. The enrichment degree of Cd, Pb, Hg and other elements in atmospheric deposition is higher, and the high value area of the enrichment factor(EF) coincides with the position of the emission source of coal mining and coal chemical industry, which indicates that the dry and wet atmospheric deposition in the industrial area is an important way for heavy metal elements like Cd, Pb, Hg to enter the soil. Industrial activities have an important influence on the increase of dry and wet atmospheric deposition in thisarea. In addition, the enrichment factor shows thatcoal burning dusts should be the main source of S and Se in atmospheric deposition and soil. Ni, Cr, As in atmospheric deposition should mainly originate from soil dusts, and thesources of Ca and Mg are closely related to the stone mining and cement manufacturing industry.

Based on the theory of variable weight, the authors used the weight of the state vector measured by the divergence degree to regulate the demand force, the weight of the variable state vector identified by the adjustment degree regulated the supply force, and the weight level of the adjustment weight weighed the balance point between the two so as to select the appropriate state. Change vector, a comprehensive evaluation model of soil nutrient geochemical transformation power, was constructed to solve the problem of evaluation distortion due to the difficulty of highlighting the restrictive effect of nutrient element. The results show that the method is easy to operate and can reflect the changing law of soil nutrient element. The weight vector of product and sum state is difficult to control because of its adjustment degree, and its application range is limited. However, the adjustment degree of exponential state variable vector varies with parameters, the adjustment effect is easy to control, and the application is wide, and it has a good change effect. The soil nutrient data in the pagoda area has low dispersion and high equilibrium. The comprehensive determination of the weight adjustment level is 0.8, the power parameter α= 2.524 8, and the weight is transferred to N and Corg. The penalty is reasonable, and the comprehensive evaluation level of soil nutrients is scientifically adjusted. The grade changes from second class to third class, 42 third class to fourth class, and 131 fourth class to fifth grade, and N and Corg are identifiedas the short plate elements of soil nutrients in the pagoda area which overall limit the improvement of soil nutrient quality.The results obtained by the authors providea necessary basis for scientific improvement of the soil under local conditions.

Soil and crop samples were collected simultaneously from the main vegetable production areas of Tianjin. The concentration of available Cd, influence factors and key regulation factor were studied by correlation analysis and principal component analysis. The results show that the content of Cd in soil samples ranges from 0.21×10^-6 to 1.03×10^-6, with an average of 0.47×10^-6, and the proportion exceeding the risk screening value (GB15618-2018) is 28%.The content of available Cd ranges from 0.05×10^-6 to 0.48×10^-6, with an average of 0.14×10^-6. The Cd content in crop samples is lower than 0.05×10^-6, which meet the food safety requirements (GB2762-2017). The content of Cd in crops is positively correlated with Cd and available Cd in soil (p<0.01). Available Cd content is negatively correlated with pH, CEC and clay content (p<0.01), positively correlated with available P content (p<0.01), but not with organic matter and Eh. Combined with principal component analysis and linear regression analysis, it can be inferred that Cd content is the dominant factor of available Cd in soil.

Based on the analysis of the origin, geological conditions and geophysical characteristics of the ancient river channel in the study area, the electrical sounding method and hydrogeological drilling are used to explore the ancient river channel in the area. The electrical sounding curve and its one-dimensional inversion show that the ancient channel is characterized by relatively high resistivity with an average thickness of 23m.From the perspective of resistivity, i.e., the comprehensive electrical characteristic parameter, the authors analyzed the spatial distribution characteristics of the palaeochannel within the detection range. The palaeochannel is deposited as a river facies on the whole,and the lithology mainly includes fine sand,medium-coarse sand and sand gravel. The spatial characteristics of the palaeochannel reflected in the resistivity image are basically consistent with the characteristics of palaeochannel revealed by the borehole data. This exploration work has reconstructed the Quaternary geological section of the study area, and laid a solid foundation for rational utilization and protection of the palaeochannel resources.

A comparison for the marine gravimeters on the same vessel was carried out between SAG-2M marine gravimeter developed by China and KSS31M marine gravimeter designed by Germany in order to test the technical performance and data reliability of SAG-2M marine gravimeter. The raw gravity data acquired from these two marine gravimeters were preprocessed according to the standards of marine geologic survey to obtain the free air gravity anomalies, and the comparison and relativity for those two types of gravity data were studied by analyzing the cross-point differences, survey lines and grid data. The result shows that the SAG-2M marine gravimeters have the same level of measurement accuracy with the KSS31M marine gravimeter because there is a highly linear relationship between the data from two marine gravimeters with an approximately similar variation trend. Based on the results of comparison, it is concluded that the self-developed SAG-2M marine gravimeter shares the similar standard of measurement accuracy with the KSS31M marine gravimeter with a stabilized technical performance, which provides an important reference for the future application of SAG-2M marine gravimeter.

Three-dimensional constrained inversion of gravity data in the mining area is an important technique for deep metallogenic environment exploration. The key point of the gravity inversion is the introduction of prior information. The reference model is a simple and effective constraint method, which can significantly improve the inversion quality. This paper discusses the construction of reference model in practice. Geological map, physical property statistics and interface information serve as parts of the import to obtain reliable results which accord with geological understanding. A reference model constraint was constructed and three-dimensional inversion of gravity data was performed in the Zhangmajing ore district. The inversion results are consistent with the surface outcrop information and the formation information revealed by the boreholes. The unconstrained results are quite different from the actual geological condition. Therefore, it is of high practical value to construct the reference model constraint to handle the inversion work. It is worthful and applicable in improving the gravity data inversion results.

Anomaly separation has always been the focus of gravity and magnetic data processing. Interpolation cutting is a spatial potential field data separation method, which has different effects on different nonlinear parts of the gravity and magnetic anomalies, so as to improve the resolution of different feature anomalies. It can be applied to denoising, anomaly separation and 3D imaging. In this paper, based on the problems encountered in the process of model and actual data processing, the interpolation algorithm is improved, and the effects before and after the improvement are compared. The improved interpolation cutting method was used to process the gravity and magnetic data of a certain exploration area in western China. Good results were obtained in the extraction of deep gravity anomalies and the three-dimensional imaging of igneous rocks.

According to the measured gravity data and wide-area magnetotelluric sounding study as well as the seismic section and borehole data, the authors investigated the deep structure of Xiaoqingling area. It is considered that the buried depths at 1 500 m, 2 500 m and 3 500 m of Taihua Group in Xiaoqingling area are important tectonic interfaces, especially at 1 500 m, which may limit the emplacement of most quartz vein orebodies. The intersection of the S-dipping and N-dipping resistivity of the grid magnetotelluric profile at 1 500~2 500 m may indicate the formation of large-scale gold orebodies. The fault structure of Xunmadao is complex, and its upper plate may be dominated by structural schist and rifting rocks. The Yanshanian intrusive rock mass may exist at the depth of 3 500 m, which has the prospect of finding quarz vein-type gold deposits and the conditions for forming tectonic alteration rock-type gold deposits. The Taiyao fault dips northward in the stepladder form. Within the range of 1.5~3 km to the north, the underlying Quaternary Taihua Group is buried at the depth of 800~1 500 m. The fault is wide in the west and narrow in the east. The deep prospecting in this area should pay attention to the recognition of the complex structural features of the electrical structure on both sides of the middle and western sections of the Xunmadao fault.

In recent years, gravity and magnetic software for data managing and processing has been developed in the direction of three-dimensional visual quantitative comprehensive interpretation, keeping pace with the requirements of geological interpretation. At present, the development of gravity and magnetic software in China needs to be further improved, so the study of the development of gravity and magnetic software is necessary. In this paper, the framework of gravity and magnetic data processing and inversion system based on component + plug-in technology has been designed, and the technical difficulties and main work lies in the research on data organization and management, 3D visualization, quantitative expression, and comprehensive interpretation. The software can realize stable platform and flexible plug-in. Also, it can combine gravity and magnetic data results with multidisciplinary information to realize 3D integrated analysis and comprehensive interpretation of geophysical multi-data. The system has a variety of standardized component interfaces and plug-in modules, having cross-language hybrid programming capabilities and characterized by stability, flexibility, reusability and extensibility. In addition, it can provide some ideas and solutions for magnetic software design.

Cloud computing provides a new development direction for the geological software. The authors have used cloud computing technology to develop a web-based online grid data processing system that allows users to easily obtain data processing capabilities such as filtering, extension, and derivative calculation without installation. The tool uses a three-layer architecture, namely the presentation layer, the logic layer, and data processing service layer. The presentation layer is developed using web 2.0 front-end technology to provide user interaction interface and data visualization functions. The data layer encapsulates a series of grid data processing algorithms, which are used to process data-processing tasks submitted by users and response data processing results. This layer includes filter calculation, frequency domain upward continuation method, and differential iterative downward continuation algorithm and some other means. The logic layer connects the presentation layer and the data layer, and calls the required algorithm and returns the calculation result according to the data processing request submitted by the user. The authors tested the correctness of the tool using magnetic data from a synthetic model, and verified the cross-platform convenience of the tool by comparative study of this means on different computing platforms.

Accurately characterizing rock types and their structural relationships can provide important information for researches on energy and mineral exploration, deep structure and tectonic, and so on. At present, geophysical data can be used to identify lithology through the differences between the corresponding physical property parameters of different rocks (such as density, susceptibility, resistivity, speed,etc.). However, different rock physical properties often coincide at a certain degree, on the other hand the result of lithological identification is not accurate enough when a single physical property is used. Therefore, it is of great significance to use multi-source data for lithological identification. Bayesian method belongs to the statistical classification methods, which relies on probability for classification, and the calculation of probability density depends on the correlation between sample attributes. On such a basis, the authors introduce the Bayesian probability model based on adaptive kernel density estimation to lithology identification. This method has good adaptability for many different types of physical property parameters and such the predicted lithology classification results with probability parameters, fuzzy intervals, and a variety of lithology classification results. This method has a strong scalability that can process both parametric and non-parametric information at the same time to maximally the known geological information and physical parameters. Synthetic models prove that this method has the ability to provide more stable and accurate results of lithology recognition compared with the methods of traditional Gaussian algorithm and fixed bandwidth kernel density estimation.

With offering the increasing opening exploration of oil and gas resources to the oversea exploration companies in Africa which remains in an early exploration stage, a good opportunity is provided for the companies in China. In this study, the gravity data of this research area were collected in order to study the tectonic characteristics of Malagasy Island, which has insufficient oil and gas geological data but abundant mineral resources. The faults and the boundaries of this basin were identified according to the response of the gravity anomaly to the sediments by the separation method of the minimum curvature, the vertical derivative of the normalized total horizontal derivative (NVDR-THDR) and the inversion of the depth of the curvature attribute, with Bouguer gravity anomaly. The geological and geophysical characteristics of the main faults were analyzed, and the distribution characteristics of faults and basins were determined, which were based on the geological and geophysical data. According to this research, there are 9 primary faults and 11 secondary faults inferred in this study area trending NNE, NE and nearly NS. The tectonics of Tamatave Basin, Morondava Basin and Majunga Basin were re-divided into 7 depressions and 3 uplifts combined with the distribution of faults from this study and previous studies, which are shown as a zonal distribution like "two depressions with one uplift". This research can provide geophysical information for exploration of oil, gas and mineral resources in Madagascar and its adjacent regions.

The Jiaxie Guyots, located in the western Pacific and belongs to China's contract areas of cobalt-rich ferromanganese crusts, contains strategic metal mineral resources, especially cobalt. Local structures of the guyots play an important controlling role in the macroscopic distribution of these resources, which leads to the research on the tectonic division of the guyots to understand their formation processes and explore mineral resources. In this paper, the gravity and magnetic data as well as topographic data were used to delineate fracture features of Jiaxie Guyots by using the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) edge recognition method and curvature attribute depth inversion method. The minimum curvature potential field separation method was used to delineate the distribution features of flank rift zones and gravity slide areas. The results show that faults of Jiaxie Guyots are mainly NW- and NE-trending, followed by NNW- and NEE-trending. The range of apparent depths of faults is between 3000 and 7000 m, and usually the depth of NW-trending faults are shallower than that of NE-trending faults. The faults of these two different directions intersect to form a conjugate shear fault zone, showing a geese-like arrangement, which provides magma volcanic conduits for seamount formation and rock wall intrusion. The flank rift zones are generally located in irregular terrain extensions of guyots, because they were shaped with magma intrusion and reshaped the seamount as irregularly appearances. During the development of flank rift zones, the gravity slide areas were also formed due to the influence of tectonic activities like earthquakes, and commonly they were located on sharp sides of margins and two sides of flank rift zones. The authors hold that this study of geological structures could give strong support to the study of the formation of Jiaxie Guyots and the comprehensive evaluation of cobalt-rich crust ferromanganese.

In order to study the contact relationship of geological bodies and the distribution locations and trends of fault structures on the plane in the northern basin of the South Yellow Sea and its adjacent areas, the authors studied the related means used to solve the related geological structures in the study area. The principles of multiple gravity and magnetic potential field boundary detection methods were systematically analyzed, and the gravity data was processed by various methods in the study area. The fault structure was re-identified and re-extracted to study the system of faults and analyze the characteristics of faults, and the tectonic zoning was conducted in combination with seismic data and related geological recognition in the study area. The results indicate that the joint NVDR-Theta, normalized standard deviations and NVDR-THDR, based on the traditional processing methods, are effective methods for dividing faults. The planar characteristics and depth information of the faults can be more quickly, effectively and accurately reflected by the methods in the study area. NE (NNE)-, NW-, nearly EW- and nearly SN-trending fault structures are developed in the study area, which are hierarchical, regional, and different in activity. The NE (NNE)-trending faults form the main structural framework of the area are the main tectonic bodies of the study area. Under the action of long-term severe activity, NE (NNE)-trending faults are distributed throughout the fault area, and are mainly spread in the northern basin and the northwestern area outside the basin, while nearly EW-trending faults are mainly distributed in the central uplift area. The structure and stratigraphic distribution of the foreland basin were formed in the northern basin under the special tectonic stress environment. Six tectonic zones were recognized in combination with the gravity anomalies and seismic data in the study area, which include Luxi uplift, Jiaolai basin, Jiaonan uplift, Qianliyan uplift, the northern basin of the South Yellow Sea, and the central uplift of the South Yellow Sea.

The Xincai iron ore district is located in the southeast of Wuyang Xincai iron ore metallogenic belt in Henan Province. It is covered with thick Cenozoic strata. The magnetite orebody mainly occurs in the Archean Taihua Group. Due to the underutilization of large-scale geophysical data and other reasons, the division of structural units in the area remains in the result of small-scale division, which restricts the deep exploration breakthrough in this area. In this paper, through the processing and interpretation of large-scale gravity and magnetic data, the spatial distribution characteristics of fault structures and strata in the area were studied. The study shows that there are six main faults in the Xincai iron ore district, which strike NW and NE, and control the basement structural framework; the basement depression area is V-shaped, and the center and both sides of V-shaped are the basement uplift areas. Among the structures, Chendian uplift and Liancun fanghudian uplift were caused by Archean Taihua rock group. The study of magnetic anomalies in this area will help to realize the deep iron ore prospecting breakthrough and hence is of great significance.