Geological,geophysical and hydrogeological means were applied to the study of radioactive anomalies in eastern Qaidam basin.Based on analyzing the depositional environment,hydrogeological environment and material composition of sand bodies in the anomalous area,this paper studied in detail the genesis of radioactive anomalies in Quaternary sediments(Q_3-4).Some conclusions have been reached: 1.The anomalies result from the leaching of Quaternary detrital minerals;2.The anomalies are spatially controlled by the mud-platform facies of Quaternary(Q_3-4) alluvial fan margin and the oxidation-reduction interface of phreatic water.It is thought that the anomalies are valuable in the study of metallogenic process,but have little significance in guiding ore prospecting work at depth.

With the deepening of the study of the transient electromagnetic method, the application of this method has become increasingly extensive since its introduction to China in 1970s. To solve the problem of sustainable development of the Dachang mine, the authors carried out a new round deep prospecting in the periphery of Dachang by adopting high-power TEM. The result is satisfactory in that the inferred mine fits well with the known information. It is concluded that this prospecting method is effective in Dachang, and that the new anomaly targets delineated by high-power TEM is reliable. The successful application of the high-power TEM in Dachang shows that this technique is effective in deep prospecting of metallic deposits.

According to the present situation of iron and steel industry in China, this paper has discussed the significance of aeromagnetic anomalies in iron ore exploration. These aeromagnetic anomalies are distributed in Quaternary cover area. Through aeromagnetic data processing, the authors put forward an opinion that the positive vertical quadratic derivative region can be used as a factor for discussing the distribution regularities of ore deposits. Aeromagnetic data and other data such as Bouguer anomaly data and geological map data are also discussed. It is considered that these aeromagnetic anomalies can be used in prospecting for iron deposits and that there exist a lot of iron deposits there.

In the mineralization concentration area with most crowded ore deposits and ore spots within the western North Qilian metallogenic sector along the Cuogou-Xiaochanggan ore belt, quite a few copper ore deposits and ore spots were discovered. These ore deposits (spots) are mostly massive sulfide ones with relatively high ore grade. Nevertheless, their ore bodies are comparatively small, and the prospecting for deep concealed ore bodies seems to be a rather difficult task. With representative practical examples, this paper has discussed characteristics of geophysical and geochemical anomalies in this area and the related ore-prospecting problem.

This paper has studied the characteristics and formation mechanism of the anomalies caused by radon and its daughters over the sandstone uranium deposit,described the recoil of the Alpha particles,the cluster effect and the natural electric field over the sandstone uranium deposit,and analyzed geological characteristics of the sandstone uranium deposit.The U-Ra balance,the magnetic susceptibility,and the change of the natural voltage are also discussed.The results obtained are of instructive significance in explaining the anomalies of radon and its daughters over the sandstone uranium deposit.

The Dongfang tree farm in northern Da Hingganling volcanics belt is situated in the northeastern part of the Deerbugan metallogenic belt. Its silver anomalies are Ag, Mo, Zn, Au and As composite anomalies. The Ag anomalies mainly assume planar distribution, with some high-value anomalies in zonal distribution. The anomalies are large in size, and have concentration zoning, concentration centers and high standard deviations as well as high threshold values, associated locally with Mo anomalies. The anomaly area shows planar argillation alteration and low denudation degree, quite similar to the Wunugetushan large-size porphyry Cu-Mo deposit in the same metallogenic belt in ore-forming geological conditions and anomaly characteristics. Besides having very good vista in prospecting for porphyry Ag (Au) polymetallic deposits, the anomaly area is likely to have hydrothermal veinlike Ag (Au) polymetallic deposits.

Controlled by unique geological conditions,the distribution of elements and geochemical anomalies and element associations of anomalies in Guichi area show obviously specific characteristics.The correct utilization of geochemical methods can yield satisfactory ore-prospecting results.Considering the geological data of this area,this paper points out three sectors with ore-prospecting potential.

1:200000 stream sediment survey shows that Dadongshan area of Guangdong Province is enriched in Sn, W, Bi, Pb, Ag, F and B, which are characterized by uneven distribution and high degree of superimposed enrichment. The delineated composite anomalies are large in size and show quite a few concentration centers. In this paper, Tanling and Chengjia concentration centers were chosen to analyze the anomaly characteristics and geological settings. It is held that these centers have favorable ore-forming conditions and ore-prospecting potential, and hence are suitable places in search for greisen type, altered tectonic belt type, altered rock body type and quartz vein type Sn and W deposits.

This paper describes the assembly method of the Aeromagnetic Gradiometric System which can be used not only in horizontal (including transverse and longitudinal plane) but also in vertical gradient survey on the Y-5 fixed-wing aircraft with the single engine and the double wings. The method and the results of applying AADCII Automatic Aeromagnetic Digital Compensator are also preliminarily discussed. Repeated tests prove that this compensation method is very effective.

The HTS RF SQUID magnetometer is characterized by low noise, high sensitivity, and wide dynamic and frequency ranges. It can therefore be used to measure the magnetic field directly. Theoretically, the HTS RF SQUID magnetometer has superiority over the conventional inductive probe in TEM application. The tentative TEM survey for comparison was carried out in field by using HTS RF SQUID magnetometer and induction, and the results show that larger detection depth could be expected in TEM survey by using the HTS RF SQUID magnetometer.

With the conventional P wave normal moveout correction based on hyperbolic moveout, the events on the far offset have a significant departure from hyperbolic moveout on CDP gather and long offset stacked section on wide azimuth seismic data in some areas of Tarim Basin. Nonhyperbolic moveout is caused by anisotropy and vertical inhomogeneity of velocity in VTI media. With the short offset RMS moveout velocity, the author obtained the anisotropic parameters by using scanning and traveltime inversion separately. The image was improved greatly by anisotropy velocity analysis in VTI media using the anisotropic parameters acquired.

This paper deals with the basic principle of applying trace element technique to near-surface oil and gas geochemical exploration, the classification of trace element observational methods, the oil-indicating significance of the criteria, the advance in the application of the trace element method to oil and gas exploration, and the development trend of the trace element geochemical researches.

Many researchers hold that natural gamma-ray curves have fractal characteristics. Using the fractal theory, the authors studied some natural gamma-ray curves. The result shows that the fractal characteristics of the natural gamma-ray curves are related to the extent of radioactive concentration in strata. The fractal characteristics exist within a certain range but disappear when the radioactive concentration exceeds a certain value. The adaptability of fractal characteristics in natural gamma-ray curves should be carefully analyzed.

The sound wave equation simulation method has been traditionally used in forward simulation of GPR. Nevertheless, as the radar wave is a kind of electromagnetic wave and the spread of the wave accords with Maxwell equation, the result of simulation is not precise enough. To solve this problem, the authors adopted the finite difference time domain method to perform simulation on the basis of Maxwell equation. In addition, the migration processing was conducted for the simulation result. It is found out that this method is correct and feasible.

Model JDF-1 Borehole Seismometer is a force balance feedback seismometer. Besides describing the main technical specifications and the structural characteristics of this seismometer, this paper recounts the application of this instrument to the seismic observation and the engineering vibration measurement.

The coherency/variance cube technique has been developed in recent years as a new technique of seismic data interpretation.In this paper,C3 coherency and variance cube algorithms are emphatically discussed.The authors have designed a software for processing seismic data in the coherency/variance cube technique.Using time slice and leveled layer slice,we can explore small faults and analyze geological structures through investigating the similarity of seismic signals between adjacent traces on the seismic cube.An analysis and interpretation of practical data show that the coherency/variance cube technique is very effective in fault interpretation in that it can improve the interpretation precision and shorten the exploration period.

Among the denoising methods, Donoho's threshold method is most widely applied.Due to its single threshold value,however, it cannot separate signal from noise completely at each step of scale and hence its denoising effect is not satisfactory. By comparatively analyzing Donoho's hard threshold and soft threshold method, this paper puts forwards a golden section method, which combines the advantages of both methods. The simulation denoising result shows that better denoising effect can be achieved by this modified wavelet threshold method, and the signal-to-noise ratio can be improved.

Resistivity tomography has been widely used in metallic ore deposits,petroleum reservoirs,civil engineering and hydrogeology due to its high resolution for the underground structures.With the Active X technology,the resistivity tomography software can realize the automatic plot by using Surfer.

Rock physics lies in the study of the physical properties of rocks related to seismic properties, especially the quantitative study of the relationship between elastic properties of rocks and their seismic properties with various fluid distributions. This relationship is important in the prospecting and exploitation of oil and gas, and hence rock physics is highly praised as a tool for"opening the door to quantitative interpretation". This paper has briefly reviewed the development of the rock physics and described the designing objects of the rock physics analysis system (RPAS). By combining core measurements with well logging and seismic information, RPAS provides a convenient tool for theoretical and experimental analysis. The ideas behind the design and implementation of RPAS are given, and the user's needs are analyzed. This paper describes the framework of RPAS and its concrete functions. Developed by object-oriented programming and Qt, RPAS is characterized by friendly graphical interface and flexible interactive manipulations. It is open and easy to transplant.

There is a strong single frequency interference wave around 50 Hz in seismic records when a high-tension line crosses over a seismic line in the process of field seismic data acquisition.The authors studied the interference wave using sine wave in time domain and subtracted it from seismic records for the purpose of suppressing the interference wave.Theoretical and real data results prove the feasibility of the method in suppression of strong single frequency which is unlikely to be suppressed by conventional filtering methods.The most major advantage of the method lies in the fact that only the interference wave with single frequency can be suppressed,and the loss of useful signal is very limited.

Many factors affect the quality of crops during their growing, and the chief factor the authors are concerned about is the soil and its influence on the rice quality. Based on an analysis of the nutrition composition of rice, the authors infer that there exist a set of characteristic elements that affect the rice quality, thus converting the agriculture problem to a geochemical problem. At the same time, according to the distribution features of the characteristic elements in soil, the authors deduce the distribution of rice quality, which can serve agricultural planning and further processing.

This paper is based on a study of the urban dust in Xi'an City, especially the environmental geochemical anomaly of lead in the street dust. Five environmental geochemical pollution sites were selected, i.e., Xixinjie, Anyuanmen, Longshoucun, Fangzhicheng and Zhonglou. The causes for the formation of environmental anomalies of lead are tentatively interpreted in this paper.

According to working principles of the ground probing radar (GPR), several successful examples illustrating the application of GPR to bad geological condition forecast in subway construction in Huangzhuang of Beijing are described. The bad geological condition instances and the importance of geological forecast are expounded. With these engineering examples, the authors have summed up the experience and means for the application of GPR to geological forecast in tunnel construction.