Geochemical exploration in the special landscape of thickly-covered grassland was carried out with unconventional methods, such as mercury vapor in soil, mobile metals and metal-organic form. The results show that the soil vapor mercury method can indicate ore-bearing fault structures, and the mobile metal formation and metal-organic formation can indicate kinds of mineralization. The combination of the two methods seems to be the optimal choice in search for hidden ore deposits in covered grassland.

Through comparison of geogas's blank and sample for different mediums, it is concluded that highly purified liquid capture medium with certain concentration is effective for collection of geogas's samples, which has the advantages of low background, easy operation, and simple analytical procedure. Different mediums have different capture capabilities for different elements. For example, the capture capability of aqua regia is stronger than that of nitric acid for Au, Ag, Cu, Zn. Poly-plastic has some advantage to adhere Au. Therefore, suitable medium and or conjugating use of two mediums should be considered on the basis of type of concerned mineral deposits henceforth.

The electrical extraction method is a new technique which extracts the epigenetic geochemical anomaly information of concealed deposits by physical-chemical means. It is established on the theory of element geochemistry and the outdoor electrical extraction technique. Some good test results were obtained in some known ore deposits. These results show that the electrical extraction method is quite effective in ore exploration.

Exploration geochemistry has made great successes in the discovery of mineral deposits which are difficult to be recognized. Although splendid achievements have been made, exploration geochemistry is facing new difficult-to-be-recognized types of mineral deposits such as sandstone-type uranium, PGE hosted in black shales, rare and dispersed elements and gold associated with oil basin. This paper briefly describes exploration geochemistry for these 4 new difficult-to-be-recognized types of mineral deposits. Deep-penetrating geochemical methods were used in delineation of sandstone-type uranium deposits in Turpan-Hami Basin, Xinjiang. Large-sized gold anomaly was delineated in Shangli oil field, Shangdong, which probably indicates gold mineralization associated with the oil field. The distribution of Pt in China shows that PGE deposits are likely to be found in black shale sequences of southwestern China. Geochemical mapping with over 70 elements will contribute to the exploration of rare and dispersed elements.

In order to probe into the causes of relatively low gold content in samples rich in organic matter from forest-swamp areas of Northeast China, the authors used AAS analysis with aqua regia solution method and AAS analysis with tetracid solution method to determine Au content of samples. The application of the tetracid solution method to eliminating silica gel can obviously raise the determination value of gold. For samples with gold content higher than 10~(-9), the difference between the two methods are especially evident. The above investigation shows that gold in samples rich in organic matter from forest-swamp areas can exist not only in the form of organic combination but also in the colloid or nanometer form. Wrapped by SiO2 colloid, gold can migrate for a long distance in water solution in an active form under the protection of high-concentration organic acid. Nevertheless, the aqua regia solution method fails to determine such SiO2 colloid-wrapped gold.

Based on a study of the regularity governing the distribution of geochemical background fields of such regional characteristic elements as Fe,Mg,Si,K,Sb,Hg and U in 1:200 000 Xiaoergou sheet of Da Hinggan Ling shallowly-covered region, the authors have made a useful discussion on such basic geological problems as boundaries of geological bodies, faults and concealed rock bodies. Field inspection shows that the application of regional geochemical characteristic elements to the study of basic geological problems is effective and seems likely to play an important role in conducting regional geological mapping and improving as well as accelerating geological mapping.

Based on a statistical analysis of the main oil-gas geochemical indices and variation characteristics of 14 major oil-and gas-bearing basins or areas in China, this paper puts forward the criteria for classifying regional geochemical fields of the major oil-and gas-bearing basins. The variation regularity governing regional geochemical background fields of the major oil-and gas-bearing basins in China has been studied. It is pointed out that from west to east the geochemical background fields tend to decrease in intensity. The distribution and variation regularity of the regional geochemical background fields is as follows: The basins in western China are of the high regional background field, the basins in central and eastern China as well as the offshore basins belong to the intermediate regional background field, and the basins in northwestern China are of the low regional background field. Their variation also tends to increase i.e., from west to east, the fields change from uniform fields to nonuniform fields. The moisture coefficients of hydrocarbons tend to change from dry in the west to wet in the east. The zonal field characteristics of such basins as Liupanshan are discussed.

It is of great importance to study and identify geochemical anomalies caused by some interfering factors and find out the eliminating methods in developing and applying comprehensive oil and gas geochemical exploration techniques so as to recognize the real anomaly information associated with oil and gas activities. Four interfering factors have been preliminarily summarized as follows: ①interference of surface special landscape; ②interference caused by soil characteristics such as clay minerals in soil, chemical compositions and soil acidity; ③underground non-oil and gas sources like faults, high carbon matter or coal layer and rocks; ④other factors, such as pollution, river flow or atmospheric influence. Characteristics of interfering anomalies and their eliminating method are also discussed.

An ultrasound bath extraction technique was applied in the modified BCR sequential extraction method for lead speciation in sediments. The extraction time of the modified BCR was optimized and the time consumed for all three stages was dramatically shortened compared with the conventional BCR. Contents of extractable metals obtained by both the conventional and the modified methods were measured by hydride-generation Atomic Fluorescence Spectrometry. The results of each fraction obtained by both methods were statistically compared. With a much shorter operating time, the proposed modified BCR sequential extraction method could serve as a valid alternative to the conventional shaking.

The Bayanbaolidao gold ore district lies in Sonid Left Banner of Inner Mongolia.The fractured alteration zone and the mylonitized zone are related to gold mineralization of this area.On the basis of geological, geophysical and geochemical achievements,geophysical and geochemical exploration models were constructed.With correlation analysis and "Geshifa" method, the axial zoning sequence of the elements is defined as As-Sb-Hg-Bi-Li-Sr-Ba-Ag-Pb-Au-Cu-Zn-Sn-V-Co-Cr-Ni-Ti-Mo-W.The front halo elements are As,Sb,Hg and Bi.The essential elements that form the mineral deposit are Au, Cu and Zn.The rear halo elements are Ti,Mo and W.According to the axial zoning characteristics,the criterion for the denudation extent of the gold deposit is w(As)×w(Sb)×w(Bi)/w(Ti)×w(Mo)×w(W).The determination of ore-prospecting criteria provides the basis for further geological exploration.

A study of geochemical tracing for the anomaly source of Pt and Pd in stream sediments shows that the Pt and Pd source in some stream sediment samples is derived from the weathering products of the nickel ore. A nickel orebody 130 m wide and 325 m long at surface with nickel content of 0.23% and highest Pt and Pd grade of 0.4g/t was discovered based on the data obtained from the soil and rock survey. Prediction of Pt, Pd and Ni potentials was made for Dacao area.

Spread in Yushu and Guolou areas in southern Qinghai Province and Ganzi and Aba areas in western Sichuan Province is mainly the cold highland covered with grass, called the cold grassy highland. To the east of these areas is shallowly-moderately dissected mountains. The unconsolidated overburden is composed of residual soil, clinosol and stream sediments. The modes of occurrence of the major indicator elements for gold mineralization, namely Au, As and Sb, occur mainly in such stable forms as sulfides, crystalline iron oxides and silicate residues, and subordinately as organically bound metals. It is held that, under the conditions of low temperature, cold grassy highland and low mountains or hills, the migration and enrichment of Au, As and Sb are mainly attributed to biogeochemical activities.

The Variscan-Indosinian granites are distributed in a large area covered with forests in central Jinlin Province.Fettered by traditional geological theory, geologists have regarded the area as "virgin land" in search for nonferrous metals.However, the new generation of geochemical reconnaissance at a scale of 1:200 000 led to the discovery of the Fuanbu W-Mo deposit, which is of great potential. The results of the geochemical reconnaissance show that the method used is effective in ore prospecting and also has such merits as reduction of vegetation damage in mineral exploration and protection of environment.

Based on a study of methods and techniques of regional geochemical exploration and starting with division of natural landscape units for geochemical exploration, this paper has dealt with such problems as the recognition of main landscape areas and zones, the selection of regional geochemical exploration methods, the basic principles for dividing natural landscape areas, and the major landscape areas and zones in Qinghai Province.

The Daijiazhuang lead-zinc deposit is the first large-size lead-zinc deposit discovered by geochemical exploration technique in Gansu Province. In this paper, the authors have reviewed the process of discovering this deposit, studied its geological and geochemical characteristics, discussed the prospects for further mineral exploration in the ore district, and dealt with the experience and lessons drawn from the geochemical exploration for lead, zinc and other nonferrous mineral deposits.

Based on a study of the metallogenic regularity and geochemical characteristics of Au,Pb and Zn deposits, the authors deal in this paper with the orientations of further ore-prospecting work in Fengtai area of Shaanxi Province and have already preliminarily delineated four targets in that area.

Based on the test of methods and technologies for multi-target geochemical survey in shallow overburden area of Hefei City, this paper has put forward the method relatively suitable for multi-target geochemical survey in this area and described preliminarily the environmental conditions of the area, thus providing scientific grounds and basic data for the prevention and cure of local fluorine-excess and iodine-deficiency diseases and the tackling of agricultural and environmental problems. This test can serve as the basis for further multi-target geochemical survey.

Being a new frontier science, environmental geochemistry deals with the abundance and deficiency of elements and the quality of soil as well as the influence of these factors upon the agricultural environment. This paper has made a comparative analysis of geochemical characteristics of soil in the Jinan-Jiyang study area so as to probe into the above problem in this area.

This paper reports some preliminary achievements made in multi-objective geochemical survey of Nanjing-Zhenjiang area, deals with some related problems such as the determination of the background values of soil elements, the inspection and appraisal of geochemical anomalies and the deepgoing studies aiming at meeting the needs of agricultural geology.

Based on accurate quantitative 53-element analytical data of 832 samples from the soil first environment and 3 061 samples from the soil second environment of Chengdu City, this paper determined through calculation background values and excess and deficiency limitations of 13 sorts of nutrient and useful elements necessary for plants such as N and 5 sorts of harmful elements like Cd and, on such a basis, carried out an evaluation of soil environment quality and selection of base areas for high-quality agricultural products in Chengdu City.

Hg accumulation in soil around urban areas is one of the most serious problems in environmental geochemistry.However, no effective method is available for determining the accumulative amount of Hg in Hg anomalous areas, and the conclusion on the mode of occurrence of Hg is questionable.In this paper,the correlativity method of elements was used to determine the baseline of Hg in soil,and then to determine the Hg accumulative amount according to this baseline and the Hg content in soil.The results show that Hg accumulation is to some extent related to cinnabar.

Based on a comparison of soil and hydrogeochemical characteristics between the liver cancer area and the surrounding normal area, in combination with the human landscape of the liver cancer area, this paper deals tentatively with the pathogeny of the liver cancer in Shende area. An analysis shows that the major factor responsible for the liver cancer seems to be the abnormally high content of NH₄⁺, NO₂^-, NO₃- in water of the liver cancer area.

This paper deals with characteristics of eco-environmental geochemistry in relation to human health and crop growth and, on such a basis, provides basic regional geochemical data for such requirements as environmental improvement, prevention and cure of endemic disease and agricultural production.

In this paper, a simple method for normalization of geochemical data is described. It can be used to reduce the differences between different analytical batches and normalize the data from different areas which have different background values. The method lies in using the ratio of the original analytical value to mean or median value in the batch multiplied by a reference value. The transfer value is given the name apparent content. Two examples are given in this paper to illustrate the details of adjusting the differences.

A geochemical exploration database was constructed for data from 1:50 000 geochemical stream sediment survey conducted in an area of about 7000 km² in Xiao Qingling region. On the basis of studying and comprehensively analyzing the ore-forming regularity, a quantitative prognostic model was established. With this model, three first-grade Au target areas was delineated.

A database was established for 1:50 000 geochemical data from an area of 57 357 km² in southern Shaanxi Province on the basis of regional geochemical management system software and MAPGIS Geography Information System （GIS） software. At the same time, data processing and mapping were performed by means of the database. With the useful information extracted, the characteristics of the regional geochemical field and the enrichment regularity of some elements in southern Shaanxi Province can be studied and analyzed. Combined with geological and geophysical data, the database is helpful to ore prognosis and the second round of ore prospecting.