To meet the urgent demand raised by the development plan for Lianyun-gang City of Jiangsu Province, geophysicists conducted in1985 airborne remote sensing and comprehensive geophysical survey, ground electrical sounding area measurement, microseismologic network surveillance and transverse wave veloci-ty determination for borehole earth block. Based on the data obtained and the historical seismic data. thin paper has made an evaluation on the stableness of geological structures in Lianyungang area. According to integrated remote sen sing and geophysical prospecting data, some 2,000km² of Lianyungang urban area has been divided into four foundation types. It is pointed out that the five diluvium divisions are areas suitable for construction, that the widely-distributed mud layer area has weak anti-shearing capacity and considerable sedi mentation rate, and that the ancient stream channels and sand layer subareas in the mud layer area have the potential danger of sand soil liquidation.The field foundation and seismic intensity zoning was made according to horizontal acceleration spectra of the field foundation, indicating that areas of type Iand type IIhave, favorable engineering geologic conditions. Using statis tical methods, this paper also predicts probability for earthquakes of magnitude 5 in 50 and 100 years.

Based on an analysis of the data obtained from 1:1,000,000 aeromagnetic structural survey, this paper brings forward some new ideas concerning geolo gical characteristics of Alxa area. Some newly-discovered Mesozoic-Cenozoic sedi mentary depression, in particular, provide grounds for further petroleum recon naissance. The division of regional structures in this area and the oil-gas pro spect of the sedimentary depressions are also discussed.

The present paper begins with a brief description of tens of newest tech niques for determining radon and its daughter products. Then. regarding the migration mechanism of radon, the authors advance a "composite model of geo-chemical halos" which emphasizes the view that radon, travels integratedly and by stages. They also give an account of some recent interpretations on radon migration put forward by researchers in the world, which include such theories as diffusion, convection, drawing and transportation. With some practical appli cations as examples, they point out the effectiveness of applying radon survey to prospecting, especially to prospecting for radioactive ore resources.

Using the calculations of linear digital filtering method, this paper affairms the existence of the specious phenomena in the resistivity togging of horizontal strata. and makes it clear that these phenomena occur only on the cross section with low-resistance conducting basement. In addition, it gives qualitative interpretation for their physical essence. The authors study emphatically the quantitative relationships between critical polar distance, maximum deviation of apparent resistivity, surface resistivity and thickness. As for the three-la yered section with low-resistance conducting basement, in case when the first layer is locally thickened, the boundary element numerical technique is used to calculate the apparent resistivity profile curve of symmetrical quadrupole which is larger than critical polar distance, and the results demonstrate convincingly the practical significance of the specious phenomena in data interpretation.

This paper deals with the main principle of the phase transformation me thod in electromagnetic frequency sounding, which can be realized in the PC-1500 computer.It will remedy the defect that phase cannot be measured dire-ctly, and thus has remarkable practical use. Calculation shows that the trans formed phase curve is consistent with the theoretical phase curve in shape and is characterized by distinet layering and strong capacity for reflecting basement at grent depth. Like the measured phase curve. it can reflect. geoelectric informa tion and characteristics of cross section. On such a basis, a method is proposed which uses phase and amphimde to carry out intergrated frequency sounding interpretation. This method has been employed to interpret frequency sounding conducted in Suibin survey area of Heilongjiang province, and the result is quite in conformity with the drilling and seismic data.

This paper describes in brief the achievements of barometric altimetry in high-precision aeromagnetic survey.The main technical indices and standardization of 1241Mtype miniature barometric altitude sensor are given first. Tests demonstrate the necessity of barometric altitude daily variation survey and the optimum control limits for setting up the station.The factors affecting the precision of barometric altimetry are investigated in several aspects. The accuracy of barometric altimetry of 124Msystem is te sted by utilizing known elevation points of China. The comparison of 55 points shows that the accuracy is higher than + 5m. Under the ideal condition, the flight at different heights over the runway of the airport suggests that this method is quite consistent with such radio altimetric techniques as 263,265 and ALT-55.Acomplete set of barometric altimetric techniques and data-processing me thods suitable for high -precision aeromagnetic survey in China has been deve loped. The practical work performed in1985 and 1987 all reaches the high pre cision of above -10m, demonstrating that this set of methods is feasible and technically advanced, has high-precision and can yield reliable results.

This paper describes characteristics of groundwater geochemical anomalies in dry season and rainy season of an arid and desert area in Inner Mongolia. The regional ground water geochemical sampling conducted respectively during the dry season and the rainy season in1981 suggests that the contents of ma jor indicator elements show obvious seasonal changes. Compared with things in the dry season. the peak value of hydrogeochemical anomalies in the rainy season moves toward the lower position, the hydrogcochemieal anomalies al most completely disappear over or near the known ore belts.and the concentra tion centers of the anomalies move to some place far away from the ore belt. Adetailed discussion has been given concerning the influence of evaporation-concentration on the formation and migration of hydrogeochemical anomalies in this area.

Based on extensive collection and thorough investigation of basic geochemical data obtained from the surface and the drill cores of No. 3 orebody in AQore deposit, the authors have made a detailed description on geochemical ano-malies of this orebody with the help of modern geochemieal exploration methods. It is demonstrated that there exist in surrounding rocks well-developed primary halos consisting of Pb, Zn. Ba. Mn, Cu,Co and Mo which show distinct vertical zoning. The zonality index calculation indicates an arrangement order of Pb-Zn-Ba-Mn-Co-Mo-Co-Cu-from the surface to the depth. On such a basis, geochemical prospecting criteria have been summarized, interpretation and eva luation have been made for geochemical anomalies discovered along the peri phery of the orebody and over two neighbouring mineralization sites. The data obtained all have practical ore prospecting significance.