Exploration geochemistry"is developing from a mineral prospecting technique to a young branch of applied earth science. It is expected that this young science would make extraordinary contributions to solving important resources and environmental problems during the 21th century. This point of view hasn' t even been fully acknowledged by a large number of exploration geochemists themselves.The scope of application of exploration geochemistry will be widened so drastically in the coming decades that the title of "applied geochemistry" will be more suitable for harmonizing its development.Applied geochistry as a branch of geosciences, is just taking shape. It is a multi disciplinary activity by chemists, geochemists, mathematicians, physists, geologists, agronomists, environmentalists etc. There is a scientific journal which bears the same name, but the results of study in this field have been widely scattered in different journals. No scientific society with this title has been organized. So there is a great chance for the Association of Exploration Geochemists to change its name to the Association of Applied Geochemisty, in order to attract a large number of multidisciplinary oriented scientists toward the same end of making greater contributions in solving important resources and environmental problems. The idea of geochemical mapping as the basic support for the development of applied geochemistry will help the multidisciplinary scientists to broaden their horizon from problems very local to problems with regional or even global overviews.

With the development of oilfield water analyzing technique, a series of achievements have been made in the application of oilfield water geochemical technique. In this paper, the oilfield water analyzing technique, the oilfield water chemical composition classification and pattern recognition technique as well as the relationship between oilfield water composition and oil/gas reservoirs are summarized. The development trend of oilfield geochemical research has also been pointed out.

Numerous geochemical anomalies delineated by 150 000 drainage sediment survey in northern Hebei are weak and gentle anomalies or single element anomalies. In the "high, large and comprehensive" anomaly areas,a bunch of large and medium size deposits such as the Fengning silver deposit have been discovered, and in the low anomaly areas,some medium and small size deposits such as the Wanquansi deposit and the Chapeng deposit have also been detected,which proves that low anomalies at favorable structure positions and volcanic intrusive areas also have good indicating significance.

1: 200 000 regional geochemical exploration work has been carried out in the forest swamp area of eastern Inner Mongolia, which can be divided into four different stages. Based on a review of the techniques used and results obtained in these four different stages, it is held that, with the gradual deepening of the understanding of such a specific landscape, the working methods and techniques have been improved steadily. Eight ore spots and seventeen mineralized spots have been discovered, of which there are seventeen silver zinc deposits and one gold deposit. The result of geochemical exploration is quite satisfactory and can objectively reflect the surface geochenmical characteristics of structures and rock-forming and ore forming processes in the working area, thus remarkably raising the reliability and truthfulness of geochemical information.

Up to 2000, regional geochemical exploration in rock areas of Xinjiang had nearly been completed with the covering area of 857 400 km². The author introduced the results of regional geochemical exploration of Xinjiang,and the existing problems,and made prospects for the future work in this region.

The abundances of 14 ore forming elements such as Au, Ag, Cu, Pb, Zn, Sb, Hg, W, Sn, Mo, U, Cr, Ni and Co in exposed crust and various rocks within different geochemical landscapes have obvious significance in the division and study of geochemical blocks of stream sediments. The application of abundances of chemical elements in rocks to the study of geochemical blocks can not only find out the geneses of geochemical blocks of stream sediments in different landscape regions but also provide the comparison conditions for the study of geochemical blocks. Therefore, the abundances of chemical elements in different tectonic units or geochemical landscape regions should be set up, and the study of their relationship with abundances of chemical elements in rocks and stream sediments should be strengthened so as to provide important and more rational evidence for the division and interpretation of geochemical blocks.

Based on investigation of landscape characteristics and test of middle large scale geochemical exploration methods in forest swamp areas within Northeast China, the authors studied some theories and methods for ore prospecting, such as characteristics of landscape geochemistry, modes of occurrence of elements and mechanism and factors affecting their migration and concentration, and media, granularity and methods for sampling. Some regularities governing secondary geochemical dispersion and enrichment are summarized, and some geochemical exploration methods are suggested for this area.

New methods and technologies were used to conduct 1:200 000 regional geochemical exploration in Wuchagou sheet, Inner Mongolia. The regional geochemical information obtained quite objectively reflects surface geochemical characteristics of lithosphere in this area. Quite a few geochemical anomalies with ore prospecting significance were detected, which, as shown by preliminary inspection, reflect mineralization. Characteristics of geochemical background distribution provide relatively objective geochemical data for the evaluation of resources and environment and the study of basic geology.

Based on the theory of primary halo zoning and taking into account the element associations and the axial zoning of an orebody at different ore forming stages as well as the spatial superimposition, this paper has established a new model for prognosis of blind orebodies?the structural superimposed halo model. This model has been proved to be effective in the prognosis of blind orebodies in certain gold ore districts and their surrounding areas.

Multi elements primary geochemical anomalies are well developed in the Qulong porphyry Cu Mo deposit. The anomalies of ore forming elements Cu and Mo(Ag) are characterized by high intensity and large size, and accord quite well with the mineralization. The anomalies of associated elements Au, Bi, Pb, As, Sb and Hg are mainly distributed on both sides of the ore anomalies, whereas the anomalies of B Co and Ni Mn Zn are spread around the ore anomalies. Na₂O occurs as negative anomalies while K₂O appears as positive anomalies in the ore district. Based on the above-mentioned association of elements, the horizontal zoning, and the Na₂O poor and K₂O rich ore forming environment, it is considered that the Qulong Cu-Mo deposit is a typical porphyry deposit subjected to strong denudation.

Stream sediment survey with density of 1 sample /km² led to the delineation of a Pt, Pd, Au geochemical anomaly belt in Sujiaying Zejiaping area. The distribution of Pt was completely coincident with the Pd and Au anomalies which are obviously controlled by NNW or NS trending structures. It is inferred from the size and intensity of Pt, Pd and Au anomalies that some PGE deposits may occur in Sujiaying Zejiaping area.

Sampling density in geochemical mineral exploration is controlled by such factors as geochemical landscape, stream distribution and geomorphic evolution. Fractal area density, drainage area ratio and altitude coefficient can reveal the forming mechanism of these three aspects. As the foundation of the sampling density theory, the factor model of sampling density could guide the formulation of sampling density and sampling layout in geochemical mineral exploration.

Methods and Technologies for regional geochemical anomaly follow up and inspection were tested at some ore districts (ore spots) in forest swamp areas of Northeast China, with peat and humus layer soil as the sampling media. It is discovered that the measured contents of such major ore forming elements as Au, Ag, Cu, Pb and Zn are basically consistent with their contents in stream detrital sediments and residual slope materials, both reflecting orebodies satisfactorily. Studies show that organic matter can be used in geochemical exploration within such landscape areas.

Different liquids, pure water and hydrochloric acid, nitric acid and aqua regia were tested with ICP-MS analysis to collect borehole nanoscale material, and concentrations of elements in varied liquids were determined. The application of 3% nitric acid and 3% aqua regia yielded good results in nanoscale　material geochemical survey in known concealed ore districts.

The Xiaoquan-Xinchang Gas Field in west Sichuan and the Houwujiahu Gas Field in south Songliao Basin were selected as the study areas, and core samples from 14 wells were analyzed for such indices as heating released hydrocarbon, acid extracted hydrocarbon and fluorescence so as to study vertical hydrocarbon micromigration. Being influenced by the physical properties of rocks, heating-released hydrocarbon and fluorescence indices show positive gradient in varying degrees. Acid extracted hydrocarbon concentration, however, shows negative gradient in some sectors of oil and gas wells or is not correlative with other geochemical indices. Based on these results, the authors established the hydrocarbon microseepage model and made dynamic simulation. The results of simulation coincide with the measured data.

With wave spectrum analytical techniques of spatial geochemical data, one can obtain abundant information of the geochemical field, understand characteristics of geochemical fields of study areas from various aspects, extract essential oil and gas related knowledge from all kinds of data, pick up more accurate anomalous oil and gas information and objectively predict oil and gas perspective areas. Case histories show that low frequency filtering reveals the main features of geochemical field, intermediate frequency filtering is consistent with oil and gas fields, and high frequency filtering reflects shallow effects and noises which are difficult to be interpreted. By combining low and intermediate frequency results with results from different frequency fields, one can pick up anomalous oil and gas information more precisely.

This paper describes the achievements made in the application of an integrated geochemical technique, i.e., the organic hydrocarbon gas survey combined with primary halo survey, to deep ore prognosis and its ore prospecting potential in the ore district. The application of this technique can be regarded as a tentative experiment to broaden the geochemical prospecting technique and method for metallic deposits (especially for deep concealed deposits), and also as a useful investigation for further understanding of geochemical anomalies around orebodies and improving the ore prospecting geochemical model.

The characteristics, objectives,principles and tasks of ecological geochemical mapping have been elucidated in this paper according to information acquired abroad. The tasks of ecological geochemical mapping include rational land use and regional programming, investigation of environmental geochemical baseline related to human health,prognosis of mineral resources and researches on agricultural geochemistry.

Remediation of soil contaminated by heavy metals remains a difficult problem in the world. Phytoremediation is a new technique to eliminate contaminants or weaken their adverse effects on ecosystem by such means as phytoextraction, phytodegradation, phytovolatilization, rhizofiltration, phytostabilization and hydraulic pumping. Hyperaccumulator and accumulator plants play an important role in soil remediation. In the past decade some achievements have been made on the selection of hyperaccumulator plants and investigation of their mechanism on detoxification and hyperaccumulation with the help of molecule biology and gene technique as well as rhizosphere treatment and planting management. With the introduction of molecular biology and gene technique, we can expect a breakthrough in this technology in near future.

Based on studies of such geochemical characteristics of Songxian County area as natural climatic and soil features, major and minor elements of parent rocks, physical and chemical properties of soil, total content of nutritive elements, effective state of nutritive elements and distribution of heavy metal elements, this paper deals with the background of soil agricultural geology, abundance and shortage of nutritive elements and soil environmental quality in this area, thus pointing out the way forward for agricultural production and adjustment of production structure.

77 soil samples and 34 soil sections from intermontane basins and alluvial plains along the Yangtze River and hilly lands in southeast Hubei were analyzed. A systematic analysis of pH and E_h values and arsenic concentration indicates that soil material is the chief factor affecting the content of As. Under the same geographical and climatic conditions, the pH and E_h values of soil seem to be the most important factors governing the vertical distribution of As. In the ore cluster areas, the soil is contaminated by As both naturally and artificially. There are many conspicuous physical and chemical differences between the two kinds of polluted soils in the vertical distribution of As content and in the pH values of soil.

Based on grain size determination, X-ray diffraction physical phase analysis and element composition analysis of floating dusts over the intersections of No. 1 Ring Road and No. 2 Ring Road as well as the thoroughfare of Renming Road in Chengdu City,the authors studied the composition,contents and associations of elements as well as spatial distribution of floating dusts over Chengdu City. On such a basis, some preliminary suggestions are made concerning the reduction of floating dust pollution.

In this paper, the authors studied environmental geochemistry of Hohhot, divided soil secondary environments according to their qualities, probed into the soil environmental geochemical element migration, and put forward some opinions for tackling various environmental geochemical problems.

Based on an analysis of samples from soil, sediments and atmosphere, the authors made a preliminary study of polycyclic aromatic hydrocarbons in Lalu wetland within suburban districts of Lhasa City. The averages of 16 sorts of polycyclic aromatic hydrocarbons amount to 82.45×10^-9, and the polycyclic aromatic hydrocarbons consist of both low cyclic ones and high cyclic ones. It is held that the polycyclic aromatic hydrocarbons in the wetland soil are derived mainly form the atmosphere.