Grounded-source transient electromagnetic method (TEM) has many advantages such as deep exploration, flexible arrangement in rough terrain and high working efficiency. Recently it has got much attention and a series of new methods are available, ranging from surface to airborne and borehole method. In this paper, the authors review the research history of long-offset TEM (LOTEM), short-offset TEM (SOTEM), multi-channel TEM(MTEM), grounded-source semi-airborne TEM and grounded-source surface to borehole TEM, and summarize their research status in forward modeling, system design, inversion, imaging and field working. The results show that, as a well-developed grounded-source TEM, LOTEM has accumulated many research achievements. Although some progress has been made, the researches on other grounded-source TEMs are still in a primary stage and still need further improvement. Valuable research results in LOTEM, for example, noise suppression technology, high dimensional inversion and point interpretation, can be introduced to these newly developed electromagnetic methods, which can help provide solutions for high working efficiency and high resolution deep exploration.

This paper has summed up the progress of the ERI method over the past decade of years as well as its future development trend in the following aspects: ① A comparison of the performances of the main ERI instruments used at present shows that the ERI instruments tend to develop in the multi-channel, multi-parameter, multi-functional, high-power direction; ② ERI measurement environment has changed from surface measurement to water surface, underwater and cross-hole measurements, with the last three kinds of measurements analyzed in this paper; ③ On the basis of analyzing ERI data processing method and inverse development status, this paper describes three-dimensional and four-dimensional inversion theory of ERI with practical examples; ④ ERT applications are summed up, and several new applications are introduced. It is concluded that, with the improvement of the probing depth and observation precision as well as the diversification of the observation models, the application field of ERI will become broader and broader, and this technique will surely have wide development prospect.

China's complicated geological background and metallogenic environment have decided that the regional geochemical exploration can play an important role in the field of China's mineral resources prospecting. This is the strategic selection under special metallogenic conditions. The first round of regional geochemical exploration of China was carried out during mid-1950s. Since then, we carried out the second and third round of regional geochemical exploration. Until now, China's regional geochemical exploration has gone through a history of 70 years, and showed unique functions in fields of the exploration and development of nonferrous metals, precious metals as well as the rare minerals, rare earth and scattered minerals. According to incomplete statistics, during 36 years (1979~2015) of the second and third round of regional geochemical exploration, totally 182 different kinds of large to super-large scale deposits were discovered in China mainly by means of regional geochemical exploration. Of which, 61 deposits have nonferrous metals, 93 deposits have precious metals, 24 deposits have critical and scarce minerals, and 4 deposits have other kinds of minerals. On average, 5.06 large to super-large deposits were discovered each year, and one large to super-large deposit was discovered within every 37,000 square kilometers-Calculated on the basis that the second and third round of regional geochemical exploration covered 6.68 million square kilometers' area of China. Regional geochemical exploration has achieved outstanding results in the field of mineral prospecting, and made great contributions in terms of ensuring and promoting China's economic development. As our country's basic, public good and strategic geological work, regional geochemical exploration comes into the 21^st century marked by big data and earth system science. Based on high precision and good quality big data, guided by metallogenic geochemical theories, and supported by modern science and technology, the regional geochemical exploration will start a new period of development. In the future, we'll continue to carry out the high technical standard and high quality regional geochemical exploration, achieve our goal of complete covering the whole area of mainland China with regional geochemical exploration, and provide more strategic prospective areas for our country's mineral resources exploration. On the basis of high-precision big data, metallogenic theories and modern science and technology, we'll establish AI and IT application system, so as to push forward the exploration and utilization of deep minerals, buried deposits as well as the critical and scarce minerals which are difficult to identify, and achieve greater breakthroughs in the geological exploration of mineral resources. By using big data technics, China's regional geochemical exploration team will continuously solve the mineral resources exploration and evaluation problems, and in this process, our geochemical exploration system will be gradually integrated into our country's science and technology advancement.

Due to historical reasons, the present coordinate systems of the geological, geophysical and geochemical exploration results are basically WGS84, BJ54 or XA80 systems; nevertheless, according to the NASG requirements on the overall use of CGCS2000 coordinates, in the future the coordinates for all kinds of results should be CGCS2000 coordinates, which causes inconvenient situation in using the results and in comprehensive research work. As a professional geographic information system software, ArcGIS has a wide range of applications in various walks. In this paper, the authors briefly introduced the ArcGIS built-in coordinate system, studied and deduced the calculation formula of the MOLODENSKY coordinate conversion method in ArcGIS, put forward the method to get the conversion and precision evaluation of transformation parameters between different ellipsoids, and cited practical examples for verification. On such a basis, the specific ideas and points for attention were analyzed for each coordinate system in the conversion of ArcGIS software to CGCS2000.

Due to the difference of the physical and chemical properties between the normal paraffin and the isoalkane which have the same molecular weight,they are affected by the physical and chemical property of soil substrate and other external environmental factors and are hence likely to have some differentiation effects during migration,rendering their distribution in space characterized by some signature and regularity.Isomerization rate indicators φ_iC4 /φ_nC4 and φ_iC5 /φ_nC5 can expose to some extent the characteristics and regularity.With the isomerization rate indicators φ_iC4 /φ_nC4 and φ_iC5 /φ_nC5 ,we can determine organic maturity,path and direction of light hydrocarbon migration and light hydrocarbon generating environment,and study biochemical degradation of light hydrocarbon.

The finite element method has the characteristics of strong adaptability in simulating the electromagnetic response of rugged topography and complex geological bodies. In recent years, it has been widely used in the three-dimensional (3D) forward modeling of magnetotelluric (MT) sounding. However, the finite element method also has some shortcomings in terms of computational efficiency. The large amount of calculation and long running time of the method are the main factors that lead to the lag of the practical process of the 3D MT inversion technology based on the finite element method compared with the 3D MT inversion technology based on the finite difference method. In order to improve the 3D forward speed of MT, the authors adopt the forward modeling scheme which uses the direct solver PARDISO and does not need divergence correction to solve the large-scale linear equations corresponding to the vector finite element method, and obtain the MT response of the geoelectric model under such different terrain conditions as flat and rugged topography. Under the conditions of medium-scale calculation, through the comparison between the direct solution method without divergence correction and the iterative solution method with divergence correction, the authors have detected that the direct solution method without divergence correction has advantages in calculation accuracy and calculation time, especially in the calculation. In terms of time, the ratio of the calculation speed of the direct solution and the iterative solution is raised by more than ten times.

The present paper makes a brief description of the progress of several main electric methods which havebeen developed quite rspidly since 1980's.They include induced polarization method,frequency spectrum IPmethod,trandient electromagnetic method, controlled-source audio-frequency magnetotelluric method and GPR.

According to the regional geophysical data, the Altun-Qilian arc giant gravity gradient zone is located at the northeastern edge of the Qinghai-Tibet block and forms the boundaries between Qinghai-Tibet block, Tarim basin and North China block. With the NEE-trending gravity gradient zone, this zone reflects the Altun fault characterized by both sinistral strike-slip and thrust. West Qilian is characterized by alternate NWW-trending arc gravity high and gravity low, which reflects the framework of squeeze nappe, thrust superposition and basin-range coupling within the Qilian orogenic belt. Between Dunhuang and Jinta, due to the tail effect of northeast Altun fault, a series of NNE-trending pull-apart fault basins associated with NEE-trending strike-slip fault and filling of mainland alkaline basalt in the pull-apart space were produced, which caused corresponding magnetic anomalies characterized by gravity low. Due to energy reduction and conversion, the Altun fault terminated in Huahai fault of Jinta basin, thus not extending eastward.

Porphyry copper deposit is the most important copper deposit type in China. With the deepening of mineral exploitation, exploration geochemistry in mineral exploration has become increasingly important. Based on related literature, this paper sums up the exploration geochemical research results of porphyry copper deposits, which include such aspects as geochemical characteristics, exploration methods, anomaly evaluation and prospecting indicators. Exemplified by the Fujiawu copper deposit, this paper reports the latest advances in the study of porphyry copper deposits.

Studying the occurrence of natural gas hydrates (NGHs) is of profound significance for NGH exploration. The evaluation of the NGH saturation mainly relies on the Archie equation using the electrical parameters of rocks. The key to accurately calculating the NGH saturation is to select corresponding values of rock electrical parameters for different geological environments, especially the porosity index (m) and the saturation index (n). However, it is still a challenge to select the optimal m and n values for NGH evaluation in resistivity logging. To ascertain the relevant resistivity regularity of NGHs and the determination method of rock electrical parameter values in the Archie equation, this study systematically reviewed relevant references and summarized the resistivity influencing factors of NGHs. Moreover, this study analyzed the influencing factors for the accurate evaluation of the NGH saturation based on the Archie equation. Accordingly, this study generalized the resistivity characteristics of NGH-bearing sediments and proposed the application research direction of the Archie equation.

Four basic problems in the application of Ground penetrtion-radar are discussed in this paper:(1) the wave-impedance of electromagnetic wave transmission in strata; (2) the reflectivity and transmissivity of electromagnetic field at the subsurface of strata; (3) reflective phase and propagating velocity of electromagnetic wave in strta; (4) detection depth of the Ground-penetration radar.

The generation of batches of GPS coordination is one of the most important tasks before the performance of the magnetic field work. This paper deals mainly with the batch generation of measuring point coordinate for magnetic field work by using Microsoft Visual C++ and Mapgis. The authors successfully designed and implemented a software witch could generate a batch of GPS points for magnetic field work and successfully used it in the TonganXiaoniuchang magnetic survey project of Sichuan Province.

The exposed crust is the critical interface where the lithosphere interacts with the pedosphere, hydrosphere, and atmosphere. The petrogeochemical map of the exposed crust can provide essential fundamental geochemical data for investigating the distributions and cycles of elements among different spheres. However, the plotting of the large-scale petrogeochemical map of the exposed crust has been constrained by the limited data volume and mapping technology. Consequently, no such a map covering the Chinese continent is available. This study proposed an innovative mapping technology roadmap based on over 16,000 petrogeochemical data and fundamental geological information. First, the databases for petrogeochemical information, stratigraphic structure information, and spatial information of geological units were constructed. Second, the geospatial information of strata and rock masses was extracted from the basic databases. Third, the petrogeochemical information was assigned to strata and rock masses to obtain their spatial distributions and element contents. Fourth, the spatial distribution patterns of 76 elements in the exposed crust were visualized using geographical information system (GIS) technology. Additionally, this study analyzed the challenges in the mapping process, including geological information accuracy, the lack of samples for special lithologies, reliability assessment, and scope of application, finally proposing corresponding solutions. The petrogeochemical map of the exposed crust demonstrates significant application potential, providing foundational data for investigating geochemical background and rock-sediment element cycling.

Based on recent English literature,this paper has summed up the present state and development of important gravimeters in the world,described a new type digital supergravimeter,and a new designing idea for gravimeter,viz. the application of absolute scale to the measurement of relative gravity.

The Xinfang gold deposit resides in the gold polymetallic ore concentration area in eastern Liaoning Province. Based on regional metallogenic patterns and existing exploration results, the southern part of the Yalu River fault zone, where the Xinfang gold deposit is located, shows significant potential for gold resources. As exploration progresses, more gold ore bodies are expected to be discovered in the gold deposit area. However, the lack of effective deep exploration techniques limits further exploration and exploitation in the area, failing to effectively reveal the extensions of lithological boundaries and the distributions of fault structures in the area. This study presented the first application of the wide-field electromagnetic method in the area. Based on the obtained results and geological engineering information, this study delineated the electrical layers within a depth of 3 km, determining the thickness of the Neoproterozoic cap rocks and inferring several fault zones. Combined with existing geological data, this study identified the low-resistivity anomaly zone at a depth of about 1 km as an extensional structural plane caused by ductile shearing. Overall, this study provides valuable geophysical data for establishing a geological prospecting model for eastern Liaoning Province, holding significant research value for geological and mineral exploration in the area.

In this paper, recent advances in the research and development of quantum magnetometers have been described together with some suggestions on further research work.

During the exploration of the underground medium structure, the gradiometer as well as its new deployment styles for various applications has become an important research topic of world concern. This paper describes various kinds of gradiometers based on torsion balance and difference algorithm and deals with the principle of each instrument. In addition, the absolute gradiometers based on the laser and atom interference are also described. In the last part of this paper, the design of the measurement light path is presented. The results obtained by the authors can serve as the technologic reference for developing gradiometer.

The main tasks of geophysical prospecting techniques in search for golddeposits are detection of or--controlling fault zonesl fracture zones and altera-tion zones, delineation of ore-bearing rock bodies and strata, determination of weak mineralization zones and search for quartz veins and other ore-bearing veins. Such traditional techniques as gravity, magnetic method, induced polari zation method and extremely low frequency electromagentic method all prove to be effective. Tests show that piezoelectric method, radio method and seis mic induced polarization method are quite promising. In addition, the study of thermoelectricity and thermoluminescent characteristics of rocks and mine rals is a new subject which deserves due consideration and will play an acti ve role in prognosis of ore resources and evaluation of ore potential.

Urban dust constitutes an important problem in urban environmental science.A review is given in this paper on the advances in the study of urban dust in various aspects both in China and abroad, such as physicochemical characteristics,spatialtemporal distribution,source,migration and transformation,bioeffect and environmental quality assessment.The future development prospects are also pointed out.It is an urgent task to study the source of urban dust at different spatial scales,the mechanism of migration and transformation and the environmental quality assessment.

In performing gas-prospecting work by means of neutron and density logging in strata with complicated lithology, one often meets with the trouble of multiple solutions caused by the disturbance of complicated lithology if the difference in neutron and density porosities is used alone to indicate gas zones. The logging gas-prospecting model, the calibration formula, the lower limit value of the gas zone and the criteria for verifying gas zones established in this paper have renewed the neutron and density logging gas-prospecting method and can repress the disturbance resulting from complex lithology, thus eliminating the possibility of multiple solutions. Case studies of logging gas-prospecting given in this paper demonstrate that the renewed method can indicate low porosity gas zones in strata with complicated lithology and improve the resolution, direct perceivability and piecision of this method, thus yielding better gas-prospecting results.

This paper makes a brief review of the development of logging andborehole geophysical prospecting work conducted by various units affiliated toMinistry of Geology and Mineral Resources in the past 40 years, especially inthe last 10 years. In methnds and techniques, the collection system has deve-loped from semiautomatic and automatic analog recording to digital recording,the methods and borehole instruments have increased from several sorts totens of sorts with the gradual realization of seriation and combination, andthe graduation technique has growll out of nothing, indicating that our workhas entered the stage of digitization. In method application and softwaredevelopment, the logging has successfully extended its application flom coalfi-eld to more than twenty types of ore deposits, the borehole geophysicalprospecting has expanded its utilization from metallic deposits to the fields ofhydrological engineering and environmental geology and thus yielded goodgeological effects and economic benefits, and the software development hasgrown from its first-step work to the in-situ operation and management, datacollection, interpretation and mapping as well as indoor further proccessing,interpretation and mapping and imaging in combination with the CT techni-que. All these achievements demonstrate that our work has possessed somecharacteristics of modern borehole geophysical techniques. finally, the paperpredicts the prospects of the work.

The artificial source electromagnetic method is an important technique for deep resource exploration. The key challenge is to improve the depth and precision of detection through innovative technology. The detection mode of electromagnetic methods is evolving from far-field to near-field, and the study of near-source electromagnetic methods has become an international research frontier in recent years. Building on the recent advancements in wide-field electromagnetic methods and multi-channel transient electromagnetic methods, the short-offset transient electromagnetic method (SOTEM) has been further developed and proposed. The distinguishing features of SOTEM are its stronger signals and wider bandwidth, which are advantageous for achieving the detection requirements of greater depth and higher precision. This special issue presents eight articles covering the methods, techniques, software, and applications of SOTEM, providing strong support for the growing need for high-resolution subsurface detection.

Based on a brief description of the basic principle of the Acoustic Doppler Current Profiler (ADCP) and exemplified by some typical environmental monitoring engineering cases, this paper gives a brief account of the achievements made by this technique in such engineering fields of Hong Kong as marine environmental quality monitoring and marine engineering environmental evaluation. The practical engineering application shows that the adoption of ADCP technique could yield satisfactory environmental monitoring result. The importance and effectiveness of applying this technique to environmental quality monitoring is also explained.

Based on data available in China and abroad, the authors have made a comparative analysis and study of the water quality characteristics of rainfall runoff on roofing of different construction materials and road surface of different materials, pointed out three major factors affecting water quality of urban rainfall runoff, and dealt with the practical significance of collecting and utilizing urban rainwater.

A soil gas radon survey was performed on a large scale to determine the distribution of radon in soil of Zhuhai City in Guangdong Province by means of a portable radon monitor of a semiconductor alpha spectroscopy. The survey sampled 469 sites covering an area of more than 100 km². The average of soil radon concentration in the soil depth of 0.6 m is 55.94 ± 58.54 kBq/m³ in Zhuhai urban area, whereas the concentration is 7.14±8.75, 37.64±25.92, and 151.25±196.23 kBq/m³ in the Quaternary sediments, the mixtures of sediments and weathered grain of granite, and the weathered granite in Doumen District, respectively. The high radon potential areas are located within biotitic granites and new industrial districts, as indicated by the strong correlation between the radioactivity level and geological lithology. The mean value of soil gas radon concentration in Zhuhai urban area (ZUA) is about ten times as high as that in Guangzhou, Quanzhou and Jinjing City. The results show that Zhuhai area has higher radon potential, and hence protective measures against radon should be taken into account.

The Laowan gold belt is located in the eastern part of the Qinling orogenic belt, between the Nanyang and Wucheng basins. It boasts super-large gold resources hosted by moderate- to low-temperature magmatic-hydrothermal gold deposits formed during the Late Yanshanian. To explore the second exploration space and achieve new prospecting breakthroughs, this study investigated the primary halo of the No.59 ore body in the Laowan gold belt. Multiple statistical methods were employed to analyze the correlations among ore-forming elements. Accordingly, reliable geochemical indicators were identified to predict deep prospecting orientations. The results show that the primary halo of the No. 59 ore body exhibits an axial zoning sequence of Sn, Ba, As, Au, Pb, Cu, Sb, Ag, Mo, Bi, W, Hg, and Zn. The front-halo element Hg appears late in sequence, positioned after ore-forming elements Au, Ag, Pb, and Cu, suggesting the presence of blind ore bodies at depth or significant extension of the known ones to a burial depth of 650 m and above. In contrast, the rear-halo element Sn appears early in the sequence, indicating that the ore body was somewhat denuded. Correlation, cluster, and factor analyses were used to investigate the affinities between ore-forming elements and other metallic elements. Strong correlations were observed among Cu, Ag, and Au, establishing them as effective prospecting indicators within the deposit area. The cumulative index ratio of front- to rear-halo elements showed an increasing trend at a burial depth of 650 m, where a well-developed and non-closed anomaly was revealed by the F2 factor score contour. This suggests promising prospecting potential at this depth and deeper parts. Based on the comprehensive analysis, this study posits that the area at and below the burial depth of 650 m in borehole ZK3041 along the exploration line 304 is an exploration target. A prediction borehole drilled north of borehole ZK3041 saw the extension of No.59 ore body at a burial depth of about 720 m. Moreover, the assessment indicators show that the ore body still holds significant prospecting potential in the deeper part.

The development of the gravity gradiometer is described simply in this paper, and the measuring principle and development experience of the rotating accelerometer gravity gradiometer are emphatically discussed. On the basis of researches on the existing airborne gravity gradiometer, the prospects of the airborne gravity gradiometer are also presented.

This paper makes a generalized description of the scientific and technical advances in magnetic prospecting in China, which include such aspects as gro und magnetic survey, acromagnetic survey, marine magnetic survey, magnetism of rocks, paleomagnetism, absolute measurement of geomagnetic field. data pro cessing and interpretation of magnetic anomalies, and development tendency of this field.

Element abundances of the continental crust and rocks cited in the past and recent literature have been based on compilations of data from various studies. This leads to uncertainties in sample representativeness and data quality. The present study is based on systematic collection of 28 253 individual rock samples over an area of 3.3 million km² in eastern China, east of eastern longitude of 105°.The sampling involves more than 800 igneous intrusive bodies and metamorphic complexes as well as more than 500 type stratigraphic sections. From the individual rock samples, 2 718 composite samples were made and analyzed for 77 elements by 15 specific methods, dominantly XRF and INAA. Analytical quality was controlled by international and national preliminary geochemical reference materials of GSR, GAu and GPt series. Synthetic results from geological, geochemical and geophysical studies were used to construct crustal constitution model, from which element abundances of the continental crust in the North China platform, the upper crust and exposed crust in eastern China, chemical composition of igneous rock in China and of sedimentary rock and metamorphic rock in eastern China were derived.

The Audio-frequency Magnetotelluric (AMT) sounding method is an electrical exploration technique widely used for shallow to medium-depth geological investigations. Its data quality is influenced by various factors, including cultural electromagnetic interference, electrode polarization, and grounding resistance. This study focuses on the impact of electrode polarization and grounding resistance on AMT data quality. First, the mechanisms of electrode polarization and the influence of grounding resistance on apparent resistivity and impedance phase are theoretically analyzed. Then, based on measured data, the effects of electrode polarization and grounding resistance on apparent resistivity and phase curves are investigated. Finally, a comparative analysis of 2D inversion results from field data is conducted to reveal how grounding resistance affects geological interpretation. The results indicate that electrode polarization significantly degrades data quality in the low-frequency band, though this can be mitigated through data processing techniques, while its effect on high-frequency data is negligible. Unstable grounding resistance mainly influences the high-frequency range, causing notable reductions in apparent resistivity and phase, which gradually stabilize toward the low-frequency band. Moreover, unstable grounding resistance may lead to inversion results that deviate from the true geoelectrical structure, thereby resulting in erroneous geological interpretations. The findings of this study provide important guidance for field data acquisition and processing.

Based on results obtained in the application of shallow seismic method to the detection of karst collapse in Tangshan, this paper has studied technical lines for detecting karst collapse in concealed karst areas, put forward technological measures for improving effects of seismic exploration and seismic resolution ratios, and analysed means for geological interpretation of seismic time profiles.

Geophysical prospecting techniques have been increasingly used in various aspects of exploration work. They can also be used in the monitoring, prediction, prevention and tackling of geological hazards. In this paper, the application effects of such geophysical methods as GPR, electric method and seismic exploration are discussed and he application effects of other methods are also summarized. Some problems concerning geological hazard exploration are put forward at the end of this paper.

Researches on the soil data of ecological geochemical environment in Zhanhua winter jujube growing area show that some important factors such as distribution, transform rule and modes of occurrence of beneficial and harmful elements in soils affect Zhanhua winter jujube quality and food safety. The elements such as Mo, Cd, Co, Hg, S, N and Se have the great influence on the quality of the winter jujube, and high content of Mo, Cd, Co, Hg and S, especially Hg, S and Cd, will reduce the fruit quality. Where these elements reach a certain content, they will severely reduce the fruit quality. On the contrary, the elements N and Se can improve the fruit quality of the winter jujube. It is suggested that the increase of the effective state content of Fe, K and water-extracting Se or decrease of the effective state content of B, Cu, P and N is favorable for the improvement of the winter jujube quality. The results obtained by the authors indicate clearly the way forward for fertilizer application and field management in growing winter jujube.

Based on the idea of wavelet transform,this paper puts forward a new technique for denoising log curve.First,wavelet decomposition of log curve is carried out in accordance with Mallat tower algorithm,then a nonlinear soft threshold is used to restrain and leach noise in the wavelet field,and finally the reconstructed log curve is obtained through wavelet reverse transform.The result shows that the technique is more effective than the traditional filtering method.

Given the particularity of biological samples, this study employed microwave digestion and inductively coupled plasma-optical emission spectrometry (ICP-OES) for the simultaneous determination of 12 elements in biological samples, including aluminum (Al), ferrum (Fe), magnesium (Mg), calcium (Ca), sodium (Na), potassium (K), manganese (Mn), phosphorus (P), titanium (Ti), barium (Ba), strontium (Sr), and zinc (Zn). By optimizing the pretreatment conditions of microwave digestion samples, this study selected the mixed reagent of reverse aqua regia (10 mL) and hydrogen peroxide (1 mL) as the digestion reagent, and an appropriate experimental procedure for the microwave digestion system to ensure complete decomposition of samples. Moreover, this study selected the optimal plasma excitation conditions, analytical spectral lines of elements, and background subtraction position to ensure high determination sensitivity of elements and interference-free spectral lines. This study plotted the calibration curve with the national primary reference materials for biological components as the calibration series, making the calibration series consistent with the sample matrix as much as possible. The simultaneous determination method had a total dilution multiple of 100, eliminating the interference of the matrix effect. The results show that this method had a detection limit of (0.04~4.93)×10^-6 and a relative standard deviation (RSD) of 1.41%~5.13%, showing high precision. As verified by the national primary reference materials, this method had a relative error (RE) within ±10% and determined values consistent with standard values. Therefore, this method is accurate and reliable, meeting the analysis requirements of biological samples.

To identify areas potentially rich in metal minerals, this study proposed a prospecting method based on tectono-geochemistry weak information extraction. After the exploration scope was determined, sampling points were arranged using a grid pattern, followed by chemical tests on the collected samples. Through static extraction, centrifugation, and dynamic extraction, weak tectono-geochemical information in the samples was extracted. Then, the distribution of metal minerals within fault zones was analyzed based on the extraction results, and thus metal mineral prospecting was completed. During the geological exploration in the Wuminggou-Baidungou area in the Wulonggou, Dulan County, Qinghai Province, the mineral structures within the exploration area were analyzed using extracted weak tectono-geochemical information. As a result, among the 17 fault zones identified, a 500 m long metal ore body was delineated in fault zone Ⅳ, six ore bodies with lengths ranging from 180 to 400 m were determined in fault zone Ⅵ, and two ore bodies with lengths ranging from 550 to 800 m were delineated in fault zone Ⅺ. The remaining ore bodies were identified as blind ore bodies. The application of tectono-geochemistry weak information extraction for metal mineral prospecting yielded significant achievements, meeting the practical needs of metal mineral exploration. This method can be widely applied to metal mineral prospecting in similar geological settings.

From 1990, the Commission on Exploration Geophysics, Geological Societyof China would write a review every year to report some major advances inexploration geophysics in the previous year, and this paper is the second one.In 1990, the application of various major exploration methods to variousfields prodeeded approximately on the same scale as that in 1989, with lotsof technical advances made. Quite a few new China-made seismic instrumentsand equipments passed appraisal, including remote measuring data-collectingsystems, seismic sources and detectors. The application of 3D, high sensiti-vity, S wave and Rayleigh wave seismic exploration and vertical seismicprofile was further broadened. Varied new China-made logging and undergro-und geophysical instruments and equipments passed appraisal, which includednumerical control logging systems and microcomputerized borehole and galleryelectromagnetic wave systems. A number of new microcomputer logging dataprocessing and interpretation systems were developed. In addtiion, several newChina-made microcomputerized instruments for electrical method began to beproduced in 1990. The ground radar system began to be used in engineeringsurvey. In cooperation with Soviet geophysicists, a new electrical method,i. e.,differential normalized method, was tested in oil fields of China with initialresults obtained. Drill holes for the first time arranged directly on the basisof high-precision gravity survey revealed industrial oil flows in 1990. As 1990 was the last year of the 7 th Five-Year Plan in China, this paper has alsomade a brief review on the progress of exploration geophysics gained in vari-ous major fields in the past five years.

Integrated geologic,seismic sounding,gravity and magnetic field and paleomagnetic studies show that the Alxa Dunhuang landmass is a rigid block with a complete,unified Precambrian crystalline basement.Bordered by Ruoqiang-Xingxingxia fault on the west and Helan Mountain on the east,and wedging itself beneath Qinghai-Tibet plateau on the south and Xingmeng Paleozoic fold system on the north,it occupies a rather large area(91°E～106°E,38°N～42°N).Being an important component part of the North China platform,the Alxa-Dunhuang landmass not only hindered the northward transmission of compressive principal stress of the Indian plate but also caused the close connection of the Tarim platform with the North China platform to form the greater Chinese platform.