Based on the newest regional aeromagnetic data, this paper describes the magnetic field characteristics of the arcuate structure in Alxa area. In the light of manifestation and distribution pattern of the magnetic fields, the author has separated them into nine positive or negative anomaly zones. The paper discusses arcuate distribution characteristics of the bedrock uplifted and downwarping zones and also the genesis of the arcuate structure.

In the light of geological and geophysical settings of central Inner Mongo lia and on the basis of the composite model established by the author, the two-dimensional interpretation technique is adopted to conduct prognosis of concealed ore deposits in this area. It is held that the Dongdeling area is characterized by the distribution of concealed ore-bearing rock series. The paper points out the presence of concealed copper-zinc polymetallic deposits "beneath the ore-bearing sequence-Baiyinbulagou gabbro-diabase and the jocks (a³) on the southern side of its contact zone.

In recent years, with the improvement of the radiometric tecbnique, rema-rkable advances have been made in the application of radiometric method to the prospecting for oil and gas fields. Portable microcomputerized instruments and equipments have been developed. In field work, high-precision and multi-parameter radiometric survey has been carried out; in indoor work, radiome tric stations have been utilized to undertake data processing and interpretation. Through integrated investigation of some oil and gas fields and model experi mentation on migration regularity of radioactive elements, new understanding has been gained concerning the relationship between radioactive anomalies and oil-gas accumulations and the formation mechanism of anomalies. Lots of case studies demonstrate that radiometric method is a simple, convenient, rapid, economical, practical and safe method in search for oil and gas fields and will surely yield good economic benefits in petroleum exploration.

The application of ground-probing radar to the engineering-geological inve-stigation has just begun in China. This paper describes the testing results of theintroduced pulso-EKKO IV pulse time-domain ground-probing radar produced by the Canadian Probe and Software Company on engineering sites. Geologists from the China University of Geosciences (Wuhan) successively made experi ments and investigations on eight engineering sites in less than one year, which involved 14 geological problems concerning five different types of rocks and soils. As a result, large quantities of data and part of stuff on drilling and dig ging verification have been obtained. These results demonstrate that this instru mental system has fairly good capacity of geological recognition, can solve to leseer or greater extent many engineering-geological problems that have been posed, possesses sufficient ability to reach the required engineering-geological depth and shows fairly high resolution power. The instrument is portable and highly automatized and the efficiency of on-the-spot work is very high. Besi des, the interference of urban environments is small, the work is nondestructive, and working sites can be chosen at will.

In the light of the basic electrochemical properties of electrolyte solutions and on the basis of the electric field distribution theory of conductive electrical prospecting, this paper,taking homogeneous isotropic media as an example, makes a fairly detailed discussion on what factors are related to the time needed for the migration of ions for some distance in the point-source electric field and to the masses of substances extracted by electrodes (liquid and solid element receivers) .on such a basis,in Combination with the modelling results of the geoelectrochemical godograph,the algorithms are given for ionic mobi lity, migration distance and migration concentration.

In water-research work of hydrogeological-engineering geophysical prospe cting, we employed quite a few array techniques embodying the flexibility of the electrical method in accordance with conditions of different geomorphologic and geologic units and differing geological-geophysical and topographic chara cteristics. In the light of local conditions, we had a definite purpose for dete ction in mind and gave full play to the role of electrical method in search for water, thus achieving fairly good results in water-prospecting work either in loose beds or in structural fissures-of bedrocks.

This paper studies the distribution of gold and the trace element geoche mistry related to gold metallization within Wuqiangxi Formation of Proterozoic Banxi Group in Mobin area, southwestern Hunan. Wuqiangxi Formation of this area is characterized geochemically by obvious depletion in Au, Hg and Sr and enrichment in As and Sb with Co/Ni>1 and Au/Ag and Sr/Ba very low. The spatial distribution of gold shows some regularity: from the distant strata to the wall rocks beside the ore vein within the ore deposit, five zones can be successively detected, i. e., background zone, depleted zone, enriched zone.deple-ted zone and enriched zone, with the last four zones forminga conjugate system. The two processes of gold depletion resulted from two separate hydrothermal leaching processes different from each other in time, scale and geochemical characteristics. Such multi-stage leaching led to two-phase metallization In the Mobin gold deposit. The appearance of the depleted areas or zones of gold and other ore-forming elements seems ubiquitous to some extent, thus serving as an important indicator in ore prospecting.