On the basis of geological exploration information obtained in the Duolongqiarou exploration area of Qinghai Province and with the molybdenitized and chalcopyritized Indosinian and Yanshanisn granites as the main study objects, the authors conducted geochemical soil (debris) survey and geophysical dual-frequency IP sweeping, delineated three valuable metallogenic prospective areas, and then employed IP sounding and EH4 magnetotelluric sounding to preliminarily delineate two anomaly belts, which are mainly NNW-striking and SWW-dipping large-size anomaly belts. A geological-geophysical-geochemical metallogenic model was formulated for this ore district, and drill holes were deployed over the inferred anomaly positions, which intersected ore bodies. The results show that the combination of geophysical methods and geological mapping information and the integrated consideration of the geochemical anomalies can avoid anomalies resulting from carbon matter, which is of great significance for the exploration work in the west special landscape areas.

The recently-discovered Ajile Ag, Cu, Pb, Zn polymetallic ore district has favorable ore-forming potential and ore-search prospect; nevertheless, the thick overburden and rare outcrops have restricted its exploration and development. Therefore, the authors employed X fluorescence method, high-density method, EH4 electrical method and soil and rock integrated geophysical-geochemical survey to the ore-prospecting work. Through areal profile survey and X fluorescence measurement, the Mn, Cu, Pb, Zn multi-element peak value anomalies can reflect surface exposed positions of ore (mineralized) bodies; the high-density electrical anomalies show that the mineralization is distributed in positions of structural fissures and rock body contact zones; The EH4 electrical anomalies reveal that the depth of No. I mineralization and shatter zone is a nearly EW-trending low-resistivity structural zone, which dips northward and extends some one thousand meters. An integrated analysis in combination with drilling result shows that lead-zinc ore bodies are mainly controlled by the low-resistivity structural zone and produced along the contact zone between the structural zone and the wall rock, the rock fissures at different depths of the structural zone and the contact surface between rocks of different lithologic characters, occurring in layers and segments at different depths.

The portable X-ray fluorescence analyzer was used to investigate the concealed ore body over the shallow Quaternary coverage area of the Shuitou fluorite ore district in Linxi County, Chifeng City. Based on an analysis of the data collected and a comparison with the known ore body, the authors have drawn the conclusion that the portable X-ray fluorescence analyzer is serviceable and can provide evidence for the prospecting of concealed fluorite ore deposits.

Soil geochemical characteristics of the Changtangling tungsten polymetallic ore district show that anomalies of high temperature elements such as W, Sn and Bi are weak, relatively small and rather inconsistent, whereas anomalies of such elements as Mo, Pb, Zn and Cu are characterized by high intensity, large scale and consistency, suggesting fairly good ore-prospecting potential. The anomalies of ore-forming elements are mainly controlled by the contact zone between the porphyroid biotite adamellite and the two-mica K-feldspar granite and were formed by the filling and replacement action of the ore-bearing hydrothermal fluid along the contact zone between rocks of different lithologic characters.

Bed set PⅠ is the main reservoir group in the Weixing Oilfield,characterized by thin thickness of single sand layer and poor spatial continuity.Bed set PⅠ can be divided into 3 composite units,which can be well reflected by the seismic wave shape.Well logs have perfect identification capacity for sedimentary micro-facies.The unit with channel or river dam sand body is defined as sand body development, and that without channel or river dam sand body is assigned to interbed development.The authors investigated the corresponding relationship between sedimentary micro-facies identified by well log data of 100 wells in 3D survey of the Weixing Oilfield and the seismic wave shape and,on such a basis,established 8 types of sand body reflection mode of seismic wave.According to the mode,sand body development can be derived for the exploration blank area of Bed set PⅠ of the Weixing Olilfield.The results provide technological support for the deployment of favorable well locations.

The effectiveness of radon gas and metal mobile state measurement was tested along the known profile in eastern part of the north belt of the Daguanchang uranium-molybdenum ore district, and the result shows that obvious radon gas anomalies and uranium-molybdenum mobile state anomalies exist over the concealed uranium-molybdenum ore body. Using this method, the authors made ore-prospecting prognosis in the western part of the north belt, followed by drilling verification of the integrated anomalies. As a result, concealed uranium-molybdenum ore bodies were discovered, which proves the effectiveness of radon gas measurement and metal mobile state measurement in search for concealed uranium-molybdenum deposits.

The studied gold deposit in Tanzania is a concealed ore deposit associated with BIF. In order to find out the distribution of the gold ore veins, the authors conducted ground high precision magnetic survey. The results show that the ΔT anomalies are mainly negative anomalies, whose peak value is higher than that of positive anomalies, which seem to be associated anomalies. The anomalies basically reflect the extension of BIF in plane and characteristics of the structure. The induced polarization depth measurement along the section shows that the contour lines of apparent resistivity are concave whereas the contour lines of apparent polarizability are convex, respectively reflecting the position of structure along the section and the features of BIF. The magnetic force and induced polarization anomaly in this area display obviously the concealed feature of BIF,and the bed of interest is intersected by drilling. The results are valuable in the deployment of drill holes.

Large-scale surface oil and gas geochemical prospecting and borehole geochemical exploration were carried out in Qaidam Basin, and the results show that oil and gas geochemical exploration is of good indicating significance in search for oil and gas fields within the basin. An integrated oil and gas accumulation geochemical anomaly model dominated by circular or semi-circular halos has been established. The oil and gas geochemical exploration techniques are effective in oil and gas prospective evaluation and drilling prediction in the new exploration of the basin, and are also valuable in finding borehole oil and gas layers and oil and gas showing beds. It is thus concluded that the oil and gas geochemical exploration techniques have broad application prospect in Qaidam Basin.

It is difficult to carry out regional gravity survey in most parts of Tibetan Plateau due to the harsh natural and communication conditions as well as low level of basic mapping and bad communication. There exist many difficult problems in carrying out regional gravity survey work in this region, such as the selection and calibration of the gravimeter, the establishment of the control range and control points of GPS, the measurement of the level altitude of gravity measurement points, the revision of the near-zone terrain, and the collection of the physical properties of the specimen. Based on summarizing the experience gained from the 1:200000 regional gravity survey in Tibetan Plateau, the authors hold that many problems could be settled by the selection of high-precision and good stability gravimeter, reasonable extension of the closing time, the adoption of CQG2000 quasi-geoid model to figure out the level elevation of a measuring point, and the expansion of the radius of the GPS base station. These measures can be used as references in the regional gravity survey work carried out in the Tibetan Plateau and other difficult areas.

Based on studying the distribution of trace elements in the dioritic weathered crust of Zigui area, the authors have divided the trace elements into three types. The first type consists of inactive elements which include Sc, V, Cr, Co, Ni, Cu, Zn, Zr, Hf, Nb and Ta, U, Th, Mo, W. During the weathering process, they can be effectively preserved. Due to the influence of redox condition variation, U, Cr and Cu sometimes show local enrichment, without obvious regularity. The second type is composed of active elements such as Ca, Rb, Cs, Sr, Ba, Pb, Ga, Gd, and Tl, which are gradually leached from profiles along with the weathering. The third type is represented by REE, which are leached from the upper section downward, and enrichment is observed in the mid-lower section, with the leaching degree of HREE higher than that of LREE. Eu gradually changes from positive anomalies in parent rocks into negative anomalies on the surface due to the weathering leaching of plagioclase in parent rocks under the oxidation environment. Under the surface oxidation condition, Ce easily produces tetravalence oxides (cerianite) and shows obvious surface enrichment, and the variation of the redox conditions leads to the undulate variation of Ce.

Starting with an analysis of the characteristics of the geophysical field, this paper puts forward the evidence for determining the NS-trending tectonic zone on the basis of the east and west differences of NS-striking gravity gradient zone and gravity-magnetic field characteristics, and investigated the regional and deep geological-structural background for the formation of NS-trending tectonic zone as well as the corresponding relationship of the zoned distributions of the earthquakes. The NS-trending tectonic zone reflected by the gravitational gradient zone has not only inheritance manifested by its consistency with the central axis structure but also newborn nature of westward expansion. In addition, there exists the superimposition of the segmentation on the basis of the unified NS-trending zone. It forms the earthquake-controlling and heat-controlling mechanism in different backgrounds of southward compression and northward expansion. It also constitutes the east-west dividing line between the eastern boundary of the Tibetan Plateau and China's continental tectonic domain, corresponding to the narrow sense NS-striking seismic zone.

In western China's loess area, the static correction problem is very prominent. Fine, accurate near-surface structure survey is very important for solving the problems of excitation well depth design and static correction. However, on the one hand, the terrain is very complex, resulting in extremely low conventional rolling refraction interpretation accuracy; On the other hand, it's very difficult to trace the high-speed layer through the micro logging because of the thick loess coverage. Therefore, the problem as to how to take good shot records and how to do well in the static correction processing has become a major difficulty in seismic exploration of these regions. The authors proposed a new method for near-surface structure survey on the basis of full test, i.e., the chromatography method, which can effectively solve the difficulty. A comparison with the conventional refraction method shows that this method can obtain richer information and depict more finely the near-surface structure. Therefore, it can be used fairly well in such aspects as the well depth design and the establishment of the initial model for static correction processing.

Both the phase IP and the polarization rate are important parameters which reflect IP characteristics of rocks or ores. Experimental work was carried out in a certain copper mine. Based on a comparison between the results of time domain IP survey and array phase IP survey, the real applying effects show that the phase parameter is more sensitive than IP to weak induced-polarization body. And the method of phase IP measurement is suitable for investigating work in the weak induced-polarization area.

A method for analyzing adsorbed light hydrocarbons in soil by GC-FID for gas hydrate exploration has been developed. In this paper the acidolysis hydrocarbon equipment has been improved, and the method is suitable for batch processing and can improve the efficiency. A method was adopted for the desorption of light hydrocarbons in head space by oscillation and heating. The optimization of main analytical conditions and quality assessment and control in analysis were discussed. The detection limits of the method for the light hydrocarbons in head space is 0.018×10^-6 (methane), The precision of the method is 6.6% (methane)~16%(isobutane)RSD. The detection limits of the method for the acidolysis hydrocarbon is 0.016 μL/kg (methane), and the precision of the method is 2.2%(methane)~19%(pentane)RSD. The method has been applied to a great quantity of real sample analysis, with satisfactory results obtained.

Exemplified by the exploration in a certain sea area in China, the authors discussed the correlation analytical method and its application to airborne gravity and magnetic anomalies. Through computation of the correlation coefficient of airborne gravity and magnetic anomalies in combination with geological characteristics, the authors divided airborne gravity and magnetic anomalies into three types, namely homologous, half homologous and non-homologous anomalies, described these three kinds of anomalies and inferred the features of the source and geological characteristics. The results can not only reduce the multi-solution of geological interpretation but also make the interpretation more in accord with the reality.

In recent years, three-dimensional seismic acquisition was carried out in Jiyang depression, even second-round three-dimensional seismic acquisition was completed in some complex oil and gas blocks and many complex media and small fault block reservoirs were studied. As a result, the oil and gas production in the Shengli oil field has been steadily growing. However, it is difficult for the traditional seismic acquisition design technology to meet the current production requirements, and hence the authors selected the steep slope belt of the Shengli exploration area to build velocity model and form a set of observation system optimization design technological series suitable for the second-round Shengli exploration district collection through the seismic wave illumination and object-oriented geometric optimization and design technology research based on the theory of wave equation. The research results show that the technological series can ensure the integrity of the form of steep geological structure and the improvement of the imaging quality of micro structures such as minor fault blocks and small sand bodies.

Porosity is an important parameter in reservoir description.Reservoir porosity is mainly influenced and controlled by sedimentary facies and diagenesis.In this paper the method of porosity prediction in the overpressure environment by utilizing TDI (time-depth index) has been studied.The key to this method lies in establishing the correlation model and recovering burial history curve including recovering denudation and decompaction correction.In the process of calculating TDI,the overpressure value is predicted according to the 3D velocity field and pressure coefficient,and is introduced into the formula of effective burial depth calculation to correct the affect caused by the overpressure environment.Porosity prediction model suitable for overpressure formation has been established.It can provide scientific basis for oil and gas exploration of deep zones.

Due to the particularity of the 3D seismic exploration method,there is a large gap between the practical construction area and the controlled target full fold area demanded in the acquisition of 3D seismic exploration of the coal field.In cost estimation,however,the coal mine only takes the target area into account,which results in economic differences between the construction team and the coal mine.Aimed at solving this problem,this paper brings forward a method that reduces the construction area by ignoring some receivers under the premise of guaranteeing the full fold area in designing 3D seismic acquisition,which not only ensures the construction quality but reduces the cost of the construction team as well.

In the exploration of coal resources, the static caused by the shallow target depth and the rolling ground influences the coalfield seriously, and coal exploration is mainly focused on faults, collapse columns, and other small structures, which sets higher demands on static correction. Therefore, the static problems which aim at tackling complicated surface in coalfield exploration are especially important. The authors calculated the tomographic static of the forward modeling data records and the actual data and, as a result, the influence of complex surface was eliminated effectively, resulting in the obtaining of high-quality stack profiles.

This paper uses finite difference algorithm of high-order staggered-grid simulate Kelvin-Voigt viscoelastic media of seismic waves and meanwhile introduces the perfectly matched layer(PML) absorbing boundary condition into its boundary. Numerical simulation demonstrates that the effect of this algorithm of absorbing boundary is very good and the wavefield of viscoelastic media obtained from high-order finite difference is relatively accurate. An analysis of viscoelastic wavefield simulation shows that the energy of the reflected wave becomes weaker, the attenuation of the high frequency wave is much more apparent in comparison with that of the low frequency wave, the main frequency becomes closer to the low frequency, and the effective bandwidth is narrower, which all induce low resolution of seismic wave according to the simulation of viscoelastic wavefields. Besides, the attenuation of PS-wave is much more rapid in comparison with that of PP-wave and the peak frequency becomes lower gradually with the increase of the propagating distance. It is also shown that the absorption and attenuation are more apparent with the increase of viscosity coefficient by analysis of the absorption and attenuation of seismic wave in different viscosity coefficient media.

Because the power frequency is complex and will produce heavy electromagnetic noise in magnetotelluric sounding, the distortion of electromagnetic signal and the troubles in data processing and interpretation may occur under the condition of serious disturbance. In order to provide reference for weakening and suppressing the interference, the authors set the line current source above the ground level to simulate the power lines, inferred the formula and calculated the electromagnetic field. The results show that, even if the transmission distance is 500 m, the disruption field can still completely submerge target signals. However, this interference field has its fixed features, so the following conclusions can be drawn through the calculation and discussion of these features:On the one hand, the electromagnetic field generated by power lines is a plane wave which can be converted into useful signal outside a wavelength; On the other hand, within the wavelength, the situation that apparent resistivity in both directions encounters interference at the same time can be avoided by arranging the electrodes according to the direction of the electric field and magnetic field.

The metal detection technology based on electromagnetic induction has very long application history and is the most popular technology for mine detection; besides, it plays a leading role in the mine detection domain. In this paper, the authors first introduce the basic principle of pulse induction and then propose a new metal detection technology that uses multi-periods and bipolar pulses, and finally give some experimental results. This new technology not only preserves high sensitivity of the traditional technology but also has the capacity of working under all ground conditions. It is a new development of the land mine detection technology.

Because of numerous interference factors in stimulating,receiving and propagating processes,the waveform of the reflected wave is distorted in the data,which will affect the quality of the stacking section.Therefore,waveform correction is the chief factor which should be considered before stacking.This paper brings forward the pseudomultichannel matching method aiming at remedying some defects in the single channel matching method.The proposed method has higher precision in amplitude,phase and travel time,and can acquire good effect in the low signal-to-noise data.In addition,it can gain waveform fidelity and improve the quality of the stacking section.Its validity and applicability have been proved by the processing of seismic data.

The application effect of weight of evidence modeling in small-medium scale metallogenic prediction is fairly good,but researches on weight of evidence modeling of medium-large scale metallogenic prediction in small low working level areas are very insufficient. In this paper, the authors selected a certain medium-large scale work area and a small low working level area in Alxa region. According to geological features in combination with spatial position analysis, appropriate evidence factors were selected. By linking each evidence factor with NE grid size of 80 m×40 m, the authors analyzed and calculated spatial relationship between the evidence and Cu high points on the basis of weight of evidence modeling in MORPAS system. Spatial distribution of favorable ore-prospecting areas is expressed intuitively through graphics. Two trenchs intersect the ore body, suggesting that the model is also suitable for the medium-large scale and small low working level area metallogenic prediction.

As an important method in potential field data processing and interpretation, Euler deconvolution has aroused widespread attention among researchers because it can provide automatic or semi-automatic estimates of source locations and depths under the condition of less priori information. This paper described the principles of Euler deconvolution, summarized its improvement as well as related problems that geophysical experts both in China and abroad have been working on in recent decades, analyzed the choice of structural index and the stability of Euler solution and the others. The future research emphasis and developing direction of Euler deconvolution are pointed out in this paper, which are of important significance for practical use of Euler deconvolution in potential fields.

This paper deals with the utilization of OpenCV open-source library in nuclear data processing, discusses the realization of the smoothing of OpenCV-based spectrum by several different kinds of methods and Kalman filter, and describes the OpenCV-based peak-finding method. A test of NASVD algorithm indicates that in large matrix data operation, the cost of OpenCV method is about 1/3 that of the traditional method. It is concluded that OpenCV can increase the efficiency of data processing and hence has a good application prospect in the field of nuclear data.

A weighted parabolic Radon transform approach is proposed based on the basic principle and computation method of conventional band-limited forward and inverse parabolic radon transform.The proposed algorithm is applied to prestack seismic wavefield restoration and reconstruction,such as the missing offset interpolation and anti-alias resampling in the offset direction;The weight coefficient is determined by seismic data in x-τ domain,i.e.,the weight coefficient varies in different iteration processes.For the seismic data from uniform sampling,this paper gives the reconstruction result of missing near offset extrapolation and resampling for anti-alias seismic data.The test results demonstrate that the presented weighted parabolic radon transform is effective for seismic wavefield reconstruction,with the characteristics of robustness,high precision and high efficiency.

Airborne geophysical data often suffer from corrugations or line level errors, which can be adjusted or removed by using levelling procedure. Levelling is a critical step in airborne geophysical data processing and interpretation. Microlevelling routine can be applied to removing the remaining line level after tie line leveling. Based on practical aeromagnetic data levelling, the authors deal in detail with the principle of microlevelling and key steps in microlevelling procedure. For the purpose of microlevelling data, a directional high pass filter perpendicular to the flight line direction is first employed to produce a decorrugation noise grid. The noise grid is then extracted as new channel flight data. Amplitude limiting and low pass filtering can be applied to the noise channel so as to remove the residual geological signal and leave only the component of line level drift, which is then subtracted from the original data to produce the final microlevelled data. This paper has also discussed some key technical problems in airborne geophysical data leveling, especially in microlevelling. The discussion in this paper may be useful in practical data processing.

This paper aims at solving the extraction of weak gravity anomaly signal under strong noise background, which is one of the key techniques in airborne gravity survey. Remez exchange algorithm design linear phase FIR low-pass filter was employed according to equiripple Chebyshev approximation theory,and model data were used to verify the effectiveness of the method. GT-1A airborne gravity system measurement data were utilized to conduct filter test. It is shown that the same results as the GT-1A system Kalman smooth filter can be obtained on the basis of the Remez exchange algorithm design linear phase FIR equiripple low-pass filter in the free air gravity anomaly under certain conditions.

Electrical imaging survey (EIS) was conducted in a refuse sanitary landfill in Tongzhou District of Beijing. By adopting quasi-Newton inversion algorithm, the authors implemented the inversion of EIS data and obtained the cross-sections of resistivity. Based on the results, the authors infer the filling limits of the refuse sanitary. It is shown that the inferred results are in good agreement with the borehole data.

In a typical hydrocarbon contamination field of Jizhong (central Hebei) plain, the authors carried out the investigation by using GPR and high-density resistivity methods, and surveyed geophysical shallow hydrocarbon contamination situation. The corresponding analysis of GPR and resistivity imaging anomalies shows that the hydrocarbon contamination is characterized by low resistivity and high dielectric constant. The contamination plume in the oil drain block was mapped. The authors hold that this kind of geophysical analytical method should be popularized.

Based on analyzing the spatial distribution patterns of surface soil and atmospheric (dry and wet) deposition of Lanzhou covering 1663 km², the authors concluded that the average content of Hg in surface soil is 0.14×10^-6 with the peak value being 6.38×10^-6, and that burning coal is the main source of Hg in surface soil. The annual mean value of total Hg content in air of Lanzhou is 28.62×10^-9,whereas the value during the heating period and non-heating period is 48.48×10^-9 and 9.42×10^-9,respectively. Ac-cording to the National Environmental Quality Standards for Soil, the area of Grade I Hg quality in surface soil of Lanzhou reaches 1376.1 km², while Grade Ⅱ, III, Ⅳ possesses 246.8 km², 31.7 km² and 8.4 km² respectively. The area of Grade I accounts for 82.75% of the whole study area, while the percentage for GradeⅡ,III,Ⅳ is 14.84%,1.91% and 0.51%, respectively. It is found that the areas of Grade III and Ⅳ are mainly distributed around the Petrochemical Plant of Xigu District and Lanzhou Second Heat and Power Factory in Chengguan and Qilihe districts.

In the Changkou tunnel project construction of Yunnan Province, three kinds of data respectively from high-density electric method, seismic wave CT between the hole and the ground and advanced forecast were used to carry out detection according to different geological problems. The results of the detection can reflect quite clearly various geohazards, suggesting that, as basic techniques, geophysical methods can play important roles in the tunnel advanced detection.

Raleigh wave exploration has been widely used in geotechnical investigation and geotechnical inspection in recent years. For the purpose of meeting the need of the exploration and achieving the best exploration result, we should make in-site test before the work, following the principle "from the known to the unknown", preliminarily understand stratigraphic and geophysical conditions of the surveyed area through the test, determine the distance between points, the distance between channels and the distance between deviations, the excitation ways and the instrument parameters and select the best observation window according to the aim and requirement of the exploration task in combination with the geological, topographic and physical conditions. Engineering examples on the application of transient Raleigh wave exploration are given, and it is shown that the Raleigh wave exploration method has great application potential for inspecting the shallow ground.

Based on the propagation of the surface wave in shallow strata and the correlation between surface wave phase-velocity and geotechnical parameters, the authors employed MASW to make engineering investigation, obtained the surface wave phase-velocity profile through data processing, and inferred the backfilling range of the field according to the surface wave phase-velocity structure. Drilling data show that the transient MASW is reliable and can yield good results.

Based on the finite difference method, the authors established the forward model for the ground-penetrating radar electromagnetic waves propagation in the river, simulated the typical conditions of different underwater formations, and obtained the corresponding 2D image. Through a comparison with the actual detecting reflected image of the river and an analysis of the simulation image and the interpretation of the actual radar detection image, the feasibility and rationality of the ground-penetrating radar method in detecting the river course were studied.