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.

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.

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.

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.

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.

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.

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 Fe-Cu-U mineralization in the Luzong area in Anhui Province occurs primarily within the syenite mass and along its contact zone with surrounding rocks. Effectively delineating the syenite mass using geophysical exploration methods is a scientific issue that needs to be addressed urgently for mineral exploration breakthroughs in the Luzong area. Therefore, based on 358 rock samples from scientific drilling borehole ZK01 at a burial depth of 2 012 m in the Luzong area, this study measured their petrophysical properties, including density, magnetism (magnetic susceptibility and remanent magnetization intensity), electrical properties (resistivity and polarizability), and elastic wave velocity. The results indicate that syenites manifested low density and weak magnetic characteristics, providing prerequisites for syenite identification through gravity and magnetic explorations in borehole ZK01 or similar geological conditions. The strata and syenite-monzonite masses in the borehole exhibited medium-to-high resistivity characteristics with nonsignificant differences, increasing the difficulties in electrical prospecting. The syenite-monzonite masses displayed lower compressional and shear wave velocities compared to the volcanic layer in the Zhuanqiao Formation, laying a foundation for distinguishing strata from rock masses through seismic exploration.

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.

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.

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.

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.

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.

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.

This study conducted a profile spectrum survey in the southern Anhui Province using a portable gamma-ray spectrometer. Based on the differences in types and quantities of natural radioactive elements present in geological bodies, this study compared the stack plots of the characteristic parameters of U, Th, and K with geologic-topographic maps to further delineate the occurrence locations of ore bodies. Additionally, this study investigated the applicability of gamma-ray spectra to the exploration of fluorite deposits and provided empirical suggestions for parameter surveys and anomaly determination. The experimental results indicate that gamma-ray energy spectroscopy applies the exploration of fluorite minerals. Notably, Th can be used as a primary indicator, exhibiting low-amplitude anomalies, which correspond well with ore bodies. Besides, this element is applicable to other surrounding rock conditions. The analysis and verification from the perspective of environmental protection revealed that the gamma-ray radiation dose rates induced by fluorite vein ore bodies are far lower than their background values and can be used as a preliminary basis for ore prospecting.

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

An analysis of the relationship between the elements in the earth's crust and the life elements and a study of the pathogenesis of some typical endemic diseases have revealed that unbalance of trace elements in geochemical environments is likely to result in human diseases. The factors affecting the balance of trace elements in human bodies are geochemical environments and nutrition components. The authors hold that the important measures that can guarantee the balance of trace elements in human bodies lie in the optimization and utilization of geochemical environments and the balance of bioavailable trace elements from the nutrition.

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.

This study aims to further clarify the characteristics of uranium deposits and faults in a uranium mining area in Xingyi City, thereby laying a solid foundation for subsequent drilling operations. Soil radon measurements were conducted using the FD216 environmental radon meter. The data obtained were analyzed comprehensively to determine the content and distribution of radon in the soil, delineate the anomaly halos of soil radon, and refine the properties of concealed faults. Furthermore, the metallogenic characteristics of uranium deposits were examined, combined with geological and geochemical exploration data. This study revealed a strong correlation between soil radon content and fault strike. The most significant radon anomaly zones are located in the southwest and central-northeast sides. Uranium deposits in the study area occur in fault fracture zones and are associated with strata. The uranium exploration target might be located within the fault zone in the first member of the Middle-Lower Triassic Jialingjiang Formation.

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.

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.

Three Thiobacillus ferrooxidans strains with strong arsenic resistance and capacity of sulfide ore decomposition, namely M1s, 1# and Malan, were used for a microbial oxidation and leaching experiment on DBF ore from Shimian County, Sichuan Province. The arsenic content and pH change in the microbial oxidation process and the optimum leaching conditions of gold were studied intensively. The change of the microbial oxidation process with time and the optimum leaching conditions of gold are given in the paper.

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 deals with the problem of "acquisition footprint" in recording geometry. The effect of "acquisition footprint" on the seismic attributes and reservoir prediction was first analyzed, and then the self-adaptive filtering method was used to eliminate the "acquisition footprint", thus inhibiting the interference of "acquisition footprint" in the post-stack seismic data. Based on an analysis of the effects on seismic attributes and reservoir prediction before and after eliminating the "acquisition footprint", the authors put forward a method for eliminating acquisition footprint.

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.

This paper deals with the classification of piles,the multiple factors responsible for the defects and the necessity of perfection inspection.It is held that the reflected wave theoretical basis and the activation and receiving sensor constitute the crux of the inspection technique for one dimensional rods. The consistency of the frequency interpretation of reflected wave signal with the transient mechanic impedance method is illustrated with practical engineering examples.The paper also expounds the theory and grounds of applying sonic transmission method to inspect the perfection of the foundation pile,the discrimination basis and examples of the inspection,and the latest sound CT technique and its inspection achievements.

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.

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.

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.

Based on model experiment and practical application of magnetic method for detection of underground cultural relics,this paper systematically describes the mechanism,technique,character and effects of applying magnetic method to the detection of underground cultural relics.From survey through data processing to interpretation of achievements,it probes step by step into the working method,technological features,anomaly regularity and means for inference and interpretation of magnetic archaeology.With practical examples,the paper recommends an oprable and popularizable working system,emphatically deals with the merits and prospects of magnetic archaeology,and points out the content and direction of further research work.

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.

The all direction imagery theory for local gravity and magnetic anomaly sources in complex conditions has been formulated for the first time in recent years. In the present paper the outline of this theory is expounded, which includes the general forward series expressions for gravity and magnetic fields with complex variable of finite downward 2D-body, the all directional continuance and all directional inversion of 2D-body gravity and magnetic fields with complex variable, and so on.

The contamination of heavy metals in soil constitutes a serious environmental risk. This paper discusses the concept of bioavailability/accessibility of heavy metals and the affecting factors, presents the progress in the study of experimental methods of selective extraction, and indicates the data application and research direction. The speciation and bioavailability of heavy metals in soil depend on elemental geochemical behavior, source of contaminants, physico-chemical condition of soil, rhizosphere enhancement and some other factors. Single and sequential selective extraction is the effective and operational methods to reflect the speciation and bioavailability of heavy metals in soil. As hand-to-mouth activity is the important pathway for soil Pb exposure to children, in vitro digestion methods have been developed to evaluate the bioaccessibility of heavy metals. Bioavailability and bioaccessibility of soil contaminants seem to be the key parameters for risk assessment. The results of selective extraction also provide the basis for contaminated soil remediation.

In the past, mainly metallic and nonmetallic elements were used as indica-tors in geochemical prospecting for metallic deposits, and the experimental useof organic gases as indicators has been reported only in foreign literature inrecent years. As no such test has been carried out in China, light hydrocarbonanalytical method suitable for exploration of metallic deposits has pot yetbeen developed and tested. This paper presents a newly-developed analyticalmethod for light hydrocarbon. The sample is placed in a vacuum vessel anddecomposed with acid to release hydrocarbon gases which are then determinedby gas chromatography. Nine items(C₁-C₅)of alkyl olefin can be determined si-multaneously. The detection limit for the sample is quite low:0.1 μl/kg formethane, with detection rate 100% and relative deviation not in excess of±20%. The analyses of we than3000 samples prove this method to be re-liable. Trial survey with this method was conducted in lead-zinc deposits, golddeposits and faulted areas, where light hydtocarbon gases prove to be extensi-vely existent and form distinct anomalies. Facts show that light hydrocarbongases seem to be a good geochemical indicator which is worth further investi-gation.It is for the first time that the hydrocarbon gas survey was performed inmetallic deposits of China.

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.