The important marks and essential characteristics of China's exploration geochemistry are big information and systematic science of the earth. The overall development of exploration geochemistry persists in the policy of laying equal stress on resources and environment, truly and actively reflects the historical locus of the development of national economy and society, and has typical significance in the field of science and technology. During the natural resources period, the connotations of geological work related to resources are from mineral resources, land resources to all natural resources, whereas the connotations of geological work related to environment are from geological environment, land environment to all natural environments which include life community of mountains, water, forests, cultivated land, lakes and grass. At the time when the Ministry of Natural Resources is established and geological work is faced with deep transformation, the author, following writing a comment on this problem in 2008, here makes another discussion on this topic in some aspects which are worthy of attention, such as big data information science and geochemical survey of natural resources, establishment of geochemical theoretical system and geochemical evaluation system for natural resources guided by systematic science of the earth, important scientific problems aimed at the field of natural resources, deepening geochemical application research and theoretical research, and establishment of perfect scientific system. The long-term aim of exploration geochemistry lies in revealing the situation of natural resources and natural environment, realizing scientific development, and rational utilization and integrated protection of the earth's resources by means of big data information and systematic science of the earth, thus creating an environment that mankind can harmoniously coexist with the earth. Therefore, the whole process of the development of China's exploration geochemistry will be permeated with transformation and upgrade. Geochemistry will emerge in national professional department and science and technology field with the multi-purpose and all-round appearance characterized by the role of systematic nature, comprehensive nature and integration as well as application practice, thus extremely expanding and deepening its role in economic and social development. With its technological advantages, exploration geochemistry will implement big survey, big data and big application strategy, establish big environment, big ecology and big earth outlook, and transform itself into big geology, big resources and big science, so as to provide a geochemical scheme for solving problems of natural resources and ecological environment and promote exploration geochemistry in the period of overall development from the advantages of big data information application and the height of systematic scientific theory to the realm of 'big geochemistry'.

The integrated geophysical exploration work of high-accuracy gravity, CSAMT and microtremor survey was carried out in Tongzhou District, capital subcenter of Beijing, the position of Yanjiao fault was redetermined and one new branch fault was discovered in the north of Yanjiao according to repeated comparison and analysis of different results interpreted in many ways. In addition, the results were proved by some boreholes. These surveys indicate that the utilization of combinational method of gravity, electricity and vibration to investigate the fault structure won't be feasible under the disturbance of the complex electromagnetic environment in cities. The spatial layout features of Yanjiao fault and branch fault will be significant in the development of geothermal resources and prevention of geological disasters.

The Pearl River Mouth basin is the largest pre-Cenozoic sedimentary basin on the continental slope of the South China Sea. It is rich in oil and gas resources. Due to the lack of new geophysical data, the distribution characteristics of the internal tectonic units in the Pearl River Mouth basin have many different views. This problem has constrained further exploration and development of the basin. This study aims to throw light on the magnetic basement structure of Pearl River Mouth basin based on the latest high resolution aeromagnetic data, combined with drilling data, seismic profiles and basic geological data. Tangent method was used in the inversion. On the basis of fully investigating the existing structural unit division in the Pearl River Mouth basin and in combination with the faults and regional structures, the internal tectonic units were studied. The result shows that the magnetic basement depth of the basin is between 0 and 9 km, and the magnetic basement is characterized by "three uplift and two depressions". The whole depression area has the characteristics of "north-south zoning, east-west sub-block". The NE trending fault is the main fault that controls sedimentary depression, while the NW-trending faults are secondary faults which control depressions.

Weak BSR or no BSR is developed in western Pearl River Mouth basin.The conventional post-stack inversion obtains only one parameter,and it is difficult to accurately predict the gas hydrates distribution characteristics.Based on seismic gather optimization,fine velocity analysis,petrophysical analysis and accurate establishment of low-frequency models,the authors used pre-stack simultaneous inversion technology to predict gas hydrate reservoirs in western Pearl River Mouth basin,adopted facies and fluid probabilities analysis technology to comprehensively identify the gas hydrate reservoirs in the study area,and achieved a fine characterization of the gas hydrates.The inversion prediction results show that the gas hydrates are developed well in the study area,and the prediction results are consistent with the drilling results,implying that the application effect of pre-stack simultaneous inversion technology is ideal.

During the exploration of terrestrial gas hydrates,Large quantities of geological, geophysical and geochemical data will be produced. The search for hydrate is of significance for effective combination of multi-source information with mathematical methods so as to establish a comprehensive information forecasting model. In this paper, the features which are favorable for gas hydrate accumulation were extracted from geological, geophysical and geochemical data in Muli area, and the corresponding transformation regularity was proposed. BP artificial neural network was used to do the study of gas hydrate prediction, and the effects of these two methods are compared and assessed. The results show that the prediction area is highly correlated with existing drilling result, suggesting that the methods are effective and the transformation regularity is feasible.

The Yongshan area of Leping City belongs to the front of the tower in the east section of the Qinhang metallogenic belt-Fuchun copper polymetallic ore-forming belt. Based on 1:10,000 soil geochemical survey in this area, the authors analyzed elemental geochemical characteristics, single element anomaly characteristics and elemental combination characteristics. In combination with the geological background of mineralization, a total of 18 comprehensive anomalies were identified, and the comprehensive anomalies were classified and evaluated. Preferably, 3 better anomalies were verified in detail. The surface exploration trough revealed 2 new gold (chemical) sites, 2 gold orebodies and 2 gold mineralized bodies, thus obtaining a good ore prospecting effect. It is believed that the ore-search prospects in the area are good, and a skarn-type copper deposit is expected to be found. This area is the favorable area for finding ductile shear gold deposit.

The Tianyu Cu-Ni deposit is located in the Gobi desert area. The geochemical characteristics of elements such as Ni, Co, Fe, Mg and Cu in the geogas were statistically analyzed by geogas survey at the scale of 1:10 000 in the range of 2 km ² in the Tianyu Cu-Ni deposit. According to the indication effect of each element on mineralization and geophysical and geochemical anomalies, five comprehensive geochemical anomalies were delineated, and Ni,Co,Cu,Fe,V indicators can effectively indicate the position of the orebody, thus exhibiting good prospecting effect in the Tianyu Cu-Ni deposit. The survey work provides new ideas for mineral exploration in the Gobi desert area.

The study area is located in the west of the southern margin of Ordos basin, on the western wing of Tianhuan depression, where Ⅰ-160 sandstone-type uranium ore spot exists. Based on the collection and collation of previous data and combined with the investigation results of airborne radioactive anomalies distributed in the study area, the author analyzed uranium mineralization conditions in this region and discussed the prospect of uranium exploration. It is concluded that there are favorable ore-hunting zones in the Chengyang-Wugou area, which has better conditions of sandstone-type uranium mineralization, with the aviation radioactive anomaly being the key prospecting area. The author delineated a favorable area for uranium prospecting. The results obtained by the author seem to have directive significance in the acceleration of the exploration of uranium and mineral resources in this region.

Induced polarization method is one of the most important geophysical methods for mineral exploration. There is strong electromagnetic interference in old mines, and traditional IP instruments are incapable of obtaining stable and reliable data. Pseudo-random signal electrical prospecting instrument is based on "system identification". It is a new electrical prospecting instrument with strong anti-interference capability and could be applied in old mines. Based on a case study of an old mine in Hebei Province, the superiority of pseudo-random signal electrical apparatus is further expounded.

EH-4 has been applied to many fields, such as mineral exploration and engineering exploration. Nevertheless, because of the limitation of the acquisition frequency as well as geological and geophysical conditions, the application effects of EH-4 in different geological backgrounds are different. In order to prove the argument that the geological geophysical work in EH-4 is reasonable, the authors analyzed the EH-4 effects in exploration of Lianshangguan hard rock type uranium, sandstone type uranium deposit in Erlian Basin and mined out region of Yili basin in Xinjiang. The results show that, in the hard rock area, the depth of EH-4 exploration generally can reach 1000 m or so, and the detection of faults, the contact zone of rock bodies and its strike and spatial distribution can yield fairly good application effect; in sedimentary basins, the exploration effect of EH-4 is affected by the overall depth of resistivity and surface resistivity, the exploration depth may sometimes only reach two hundred or three hundred meters, but can sometimes reach five hundred or six hundred meters. Although the depth of exploration is not big, but the shallow geoelectric properties reflect good effect.

The longitudinal heterogeneity of reservoir and gas saturation in He 1 member of well block Jin 72 of Dongsheng gas field is quite large, and gas and water distribution is diverse.Predicting effective reservoir is a key issue in exploration and development.Combined with well logging data,a statistical and comparative study method was used to establish the logging response characteristics and the criteria of fluid identification in the tight sandstone reservoir of He 1 member.The theory proves that the gas-bearing sandstone decreases with the increase of gas saturation,and the longitudinal wave velocity and the shear wave velocity decrease,but the longitudinal wave velocity changes more than the shear wave velocity.Therefore,the longitudinal and transverse wave velocity ratio decreases.Based on this theory,the reservoir fluid is quantitatively identified through cross-section analysis.At the same time,based on the longitudinal and transverse wave velocity ratio inversion and longitudinal wave impedance inversion analysis,the regularity of gas-water distribution and its spatial distribution characteristics in He 1 member of the study area are clarified,which provides the basis for oil and gas exploration in the study area.

In tackling the technical difficulties of deep and shallow consideration in active fault exploration,the authors achieved good exploration results through the application of shallow seismic P/S wave reflection combined exploration.The fault identified by this method is proved to be reliable by drilling.In this paper,the key technology and parameters selection of field data acquisition,data processing and stacked section interpretation are described.Engineering practice proves that the geophysical exploration combination method described in this paper is effective and reliable in active fault detection,and can effectively find out the plane position and spatial distribution of active faults in the buried area,thus providing a scientific geophysical basis for earthquake prevention and disaster reduction in cities and towns.

In the Qaidam Basin,the overthrust is developed and,because of the influence of fracture,the footwall imaging is difficult and complex.Based on the seismic numerical simulation technology,the authors integrated seismic and logging data to set up a geological model so as to guide the seismic processing and interpretation.The forward results of the Yingxiongling area show that,due to the high speed formation on the hanging wall,there appear monoclinic,local pseudo faults,bedrock pull-up and fault shape change in the footwall.The results obtained in this paper can be used for reference to the seismic data processing and interpretation in Yingxiongling area and exploration target areas of other structural reservoirs in the Qaidam Basin.

The Dawangshan tungsten-molybdenum polymetallic deposit in Jiangxi province is a typical quartz vein type deposit, lies in the Dawangshan-Yudu Cu-Mo-Au-Ag-Pb-Zn ore belt. The ore-bearing rock mass is characterized by multiple stages. According to the LA-ICPMS zircon U-Pb dating technique, the diagenetic age of fine-grained granite in the late stage is 145.1±0.89 Ma, which is close to the formation time of medium-grained granite formed in the early stage (147.8±1.9 Ma). Using the Re-Os isotope dating technique of molybdenite, the metallogenic age was 147.6±1.8 Ma. Indicating that the deposit was formed in the late Jurassic, It is consistent with the diagenesis and mineralization age of Yanshanian quartz vein type tungsten molybdenum polymetallic deposit in Nanling area. Re content of molybdenite has important reference value to indicate the source of mineralization materials. The Dawangshan tungsten-molybdenum polymetallic deposit is related with Yanshanian granites, the Re contents of molybdenite samples is 2 215×10 ^-9~10 183×10 ^-9, It is consistent with the characteristics of tungsten deposit associated molybdenum,which indicates that the ore-forming materials are likely to come from the crust or crust-mantle-derived ones. In combination with metallogenic geological background, the author infers that the Dawangshan deposit is associated with the subduction of the Paleo-Pacificocean plate beneath the Eurasian continent. It is proposed that the ore-forming materials were extracted by alkali metasomatism between the magma and the wall rock and then concentrated in the favourable areas.

After more than 30 years of research in high-level radioactive waste disposal, China has initially identified Xinchang block as the recommended site of underground laboratory. It is necessary to make full use of the existing data to express all kinds of geological phenomena accurately and intuitively to reproduce the spatial distribution of geological units and their mutual relations. on the other hand, it is possible to mine hidden geological information to facilitate geological analysis and engineering decision-making, which is very important in the research phase of underground laboratory. Based on the comprehensive analysis and interpretation of the existing data, the three-dimensional geological model of Xinchang block has been established. The model reproduced the geologic and environmental characteristics of Xinchang block. Based on the model, we designed the drilling to expose the fault and determined the location and main structure of the underground laboratory, the effect seems good. This study can provide useful reference and technical support for the geological analysis and engineering design of the high-level radioactive waste disposal project in China.

The prospect of exploration in southern South China Sea is widest,but the seismic data are very rare and the quality is low.The deepwater block seismic data in southern South China Sea are constrained by low quality seismic data acquired in the 1970s,characterized by no navigation text,time uncertainty of record about seabed,serious lack of traces and very short cable,which results in unique seismic processing results with serious multiples,low signal-to-noise ratio and illegibility of stratigraphic structure record on paper.To solve these problems,the authors use and develop a set of key technologies that are suitable for seismic data processing in this area,such as using navigation reconstruction technique to solve the problem of lack of navigation text,using self-correlation technique to solve the problem of seabed records uncertainty,using the frequency limited F-K domain interpolation technique to solve the problem of lack of traces,using combination multiples suppression technique to solve the problem of multiples suppression caused by short cable.The final results show that the applications of key technologies make the seismic data achieve expected effect in this area.These technological achievements not only provide reliable seismic data for deepwater oil and gas exploration in southern South China Sea but also provide some ideas and techniques for similar low-quality seismic data processing.

A one-dimensional inversion method for the vertical Z component of any measuring point in the frame of the large loop source transient electromagnetic method is proposed in this paper. The algorithm uses the CMD regularization factor optimization scheme, smoothness function and natural boundary conditions to constrain the inversion process, reduce the initial value dependence, and ensure the autonomy of the inversion process and the stability of the inversion results. In the inversion process, while ensuring that the model residual decreases along the gradient, the maximum value of the model correction is limited, so that the inversion model is not easy to fall into the local minimum, which ensures the global convergence of the inversion results. The sensitivity matrix is updated by Newton's method, thus reducing the workload of the entire inversion calculation. Finally, the reliability of the algorithm is guaranteed by five-layer double low-resistance layer model, double high-resistance layer model and measured data.

3-D inversion plays an important role in the quantitative interpretation of magnetic data. However, the commonly used space-domain 3-D inversion algorithms usually require a large number of forward modeling and inversion calculations. Hence, the inversion based on a large-scale data is usually inefficient. 3-D imaging is another significant algorithm for the qualitative and quantitative interpretation of magnetic data. This paper implements a frequency-domain iterative approach for 3-D imaging of magnetic anomalies and gradients, which can improve imaging efficiency and is suitable for rapid imaging of large-scale data. The frequency-domain forward formulae and imaging formulae of magnetic total field anomaly and magnetic gradients are derived in this paper. A depth scaling factor is added to the imaging formulae to significantly improve the depth resolution. In order to reduce the fitting error and improve the imaging accuracy, this paper adopts an iterative optimization algorithm. The effectiveness and feasibility of the presented approach were verified by the synthetic data and real data from a metallic deposit area in Xinjiang.

In the magnetic exploration theory, total-field anomaly ΔT is regarded as the component T_ap of the magnetic anomaly vector T_a on the main field (T₀) direction and thus constitutes the theoretical basis. However, there is an error in this approximation. Theoretical calculations and experiments have proved that this approximation error will increase rapidly as the T_a increases. When the magnetic anomaly T_a is much smaller than T₀, the influence of the error is small and negligible. In the case of a strong magnetic anomaly, the error is large, and the processing interpretation accuracy of the ΔT anomaly is greatly affected. For high-precision magnetic exploration, ΔT must be converted to a magnetic anomaly component Tap for processing and interpretation. In this paper, the method of accurately calculating the magnetic anomaly component using T_ap based on the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm is proposed. Firstly, the authors derived the forward formula for ΔT from Tap, and then constructed the objective function of Tap inversion by the difference function between ΔT and T_ap. L-BFGS algorithm was used to solve the Tap from ΔT. Model experiments show that the Tap calculated by this method is very close to the real value, which can reduce the error by two orders of magnitude. This method also yields good results in the presence of noise and background fields. The method was applied to the processing of ΔT magnetic survey data of the Yangshan iron mine in Fujian Province, and the results of processing and interpretation which are more consistent with the actual results were obtained.

The use of VSP data to accurately acquire formation velocities plays an important role in time-depth conversion and migration imaging of seismic data.Due to factors such as changes in receive and excitation conditions,near-source dynamic interference,and first arrival time pick-up errors,the first arrival time of VSP data often contains a certain degree of random interference.The authors studied the error characteristics of inverting interval velocity for VSP data with different offsets by layer-by-layer recursion algorithm when VSP data have random noise at the first arrival time and only deep data are received.Some conclusions have been reached:①The larger the offset,the smaller the inversion velocity error of the corresponding data;②When the data is only recorded from the deep level,the smaller the offset,the closer the inversion result to the actual formation velocity.For this reason,the first arrival time should be smoothed before being inverted by layer-by-layer recursion algorithm,and then the average of inversion results is taken from multi offset VSP data as the final interval velocity.This method can improve the inversion accuracy of the interval velocity.By using this research conclusion,good results were obtained in the processing of marine Walkaway-VSP data.

Imaging condition is the key to realizing accurate imaging of seismic wave field,and optimizing reverse-time imaging condition is especially important in improving the application of reverse-time migration method.For this reason,based on the impulse response of zero offset and non-zero offset,this paper compares the reverse-time imaging condition based on one-way wave separation with conventional reverse-time imaging condition in detail.On the basis of the complex theory model and the real 3D seismic data of SZ working area,the imaging effects of two kinds of reverse-time imaging conditions are compared.The results show that the imaging results of the reverse-time imaging condition based on one-way wave separation can effectively attenuate the low wave number background noise,restore the effective seismic imaging information concealed under this background noise,and the stratigraphic details are characterized more clearly.These results can provide guidance for the high precision seismic imaging of complex wave fields and complex structures.

The shallow layer of Bozhong A oilfield develops a large number of "bright spot" gas-bearing reservoirs.The identification of these reservoirs is seriously affected by the water-bearing reservoirs with the tuning thickness.To solve this problem,the authors,based on the difference of the main control factors of the strong amplitude caused by the gas and water layers,analyzed and summarized the amplitude energy response law of the different thickness of the gas layer and the water layer with tuned thickness,and proposed the method for detecting the shallow "bright spot" type gas layer by using the frequency-dividing amplitude.The method was successfully applied to the prediction of gas-bearing reservoirs in Bozhong A oilfield,and guided the well-appraisal proposal efficiently.This method can be potentially applied to the other gas-bearing reservoirs prediction in Bohai and provide reliable technical supports for well deployment of oil and gas exploration.

Cross-hole electromagnetic attenuation tomography is a method that uses the amplitude information of electromagnetic waves to invert the distribution of the attenuation constant of the medium by the amplitude change of the electromagnetic wave from the transmitting to the receiving. Transmitter amplitude is also called the initial amplitude, which is generally unknown. Its accuracy largely affects the tomographic results and it needs to be obtained before inversion or by special inversion methods. This paper summarizes four initial amplitude processing methods, i.e., linear fitting method, matrix inversion method, dual-frequency electromagnetic wave method and neighboring traces method. The feasibility of these four methods is verified by synthetic data, and the advantages and disadvantages of each method are pointed out: Linear fitting method is suitable for the case where the physical property changes little; matrix inversion has low requirements for physical condition, but the amount of calculation is relatively large.; dual-frequency electromagnetic wave method can directly obtain the conductivity distribution, but only for the good conductor case; the applicable situation of neighboring traces method is the most extensive, but it is susceptible to interference.

A method for the pretreatment and determination of trace thallium in soil by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) with mixed acids sample digestion system was established. In this study, the authors investigated the optimum instrumental conditions for the determination and optimized the concentration and volume of the matrix modifier, adsorption-desorption system, adsorption acidity and the oscillation time. The detection limit was 0.015×10 ^-6, and the relative standard deviation was from 5.49% to 13.42%. The method was verified by National Standard Reference Material and the results were accurate and reliable.

In order to provide scientific reference for the ecological control of the water and the risk assessment of sediment treatment, the authors analyzed the content level, the distribution characteristics and the content change trend of heavy metals such as Cu, Pb, Zn, Cd, As and Hg in water and Cr, Zn, Pb, Cu, Cd and Hg in sediments. The Nemerow Index and the Potential Ecological Risk Index were used to evaluate the accumulation degree and potential risk of heavy metal pollution in water bodies and sediments. The results show that the average content of six heavy metals in water is in the range of 0.005 7~4.796 0 mg/L, and the content exhibits the order of Zn>Cu>Cd>Pb>As>Hg. The content of As in the water body shows an increasing trend with water flow, while the other heavy metals content in water decreases obviously with the water flow. The average content of six heavy metals in the sediments is in the range of (61.6~5 999.3)×10 ^-6, with the order of Zn>Pb>Cu>Cd>Cr>Hg. The content of heavy metals in the sediments of the river sections has undulating changes, but the overall change trend is that the content of heavy metals in the sediments decreases obviously with flowing water. The main heavy metal pollutants in Dongdagou water are Cu, Pb, Zn and Cd, and the single factor pollution degree is in order of Cd>Pb>Zn>Cu. The Dongdagou water evaluated by the Nemerow Index shows that there are different degrees of polluted water in the river. The contaminations in sediments are heavy metal pollutants Cd, Hg, Pb and Cu, and the degree of ecological risk is in order of Cd>Hg>Pb>Cu>Zn>Cr. The evaluation of the sediments in Dongdagou by using the Potential Ecological Risk Index shows that the total potential ecological risk index of the sediments in the whole section of Dongdagou is serious.

Through the investigation and study of surface soil in Changshan County, western Zhejiang Province, a large area of selenium-rich soil was found, and the distribution characteristics of selenium were summarized. The mean amount of selenium in the surface soil in the study area is 0.44×10 ^-6, and different soil types obviously have different amounts of selenium. The amount of soil selenium of the lime (rock) soil is the highest, with the average value being 0.58×10 ^-6, and different parent materials obviously have different amounts of selenium. The amount of soil selenium content in Holocene flood alluvium is the highest, with the average value being 0.59×10 ^-6. The probability accumulation curve shows that the exogenous input components in Changshan have little effect on soil selenium. The amount of soil selenium is closely related to the values of V, Mo, Ni, Cr, S,Cu and Cd (P<0.01), and is also closely related to organic matter (r=0.35), with no significant correlation with soil pH. The selenium values of marlstone in Xiyangshan Formation, carbonaceous shale and siliceous rock in Hetang Formation and carbonaceous shale in Ningguo Formation are relatively high. Selenium in soil inherits selenium in rocks. The wide distribution of selenium-rich rocks is the important reason for the formation of selenium-rich soils.

Based on the principle of hydration heat release and indoor and outdoor tests, it is found that there is a significant temperature difference between the concrete mixture layer and the floating slurry layer, indicating that the pouring height of the concrete mixture can be determined by the temperature change. A portable temperature control device is designed to determine whether the concrete mixing surface reaches the designed height, that is to say, a temperature sensor is respectively embedded at the height of the designed pile top and at the height of 50cm below, and the temperature sensor of 50cm below the height of the designed pile top is used to obtain the temperature peak of the concrete mixture, and then the temperature peak of the temperature sensor at the height of the designed pile top is used to determine the concrete mixture top. It is suggested that the concrete mixture should be overfilled at the height of the designed pile top, namely 50cm above the second temperature sensor, which is 0.3m less than the norm and can save concrete.

The two-dimensional high density electrical method can overcome the limitation of three-dimensional high density electrical method on topography and cost. The 3d high density electrical method can effectively solve the deficiency of two-dimensional high density electrical method in detecting space morphology. Therefore, Three-dimensional inversion of data obtained from two-dimensional exploration of high density electrical method has not only realized the three-dimensional visualization of underground space structure but also avoided the impact of topography and cost. Applying this method to the exploration of karst caves, using DUK-2A high density electrical system to collect data, and then convert the two-dimensional high density data into three dimensional inverse data, the results of the inversion can be obtained by any 3d dielectric section, by Slicer Dicer, in order to get rich information about the cave, finally, the interpretation of karst cave is made by combining the 3d dielectric section and borehole data, providing scientific basis for the smooth operation of the project, the feasibility and validity of this method are proved.