Acomparision among several computer terrain correction methods in regional gravity survey is made, besed on a test conducted in three areas with different topographic complexities. Moreover, the accuracy of terrain correction of the zone of 1-2km calculated with a grid of 1×1km² is also discussed.

Based upon a series of researches done by earlier investigators on problems concerning earth waves, an approximate formula for calculating the lateral waves arriving from the earth (limestone) -air interface is given in this paper, with special reference to the geoelectrical characteristics of the karstic terrain. This formula is explicit in physical sense, easy to calculate, and simple for numerical inversion. The result of the numerical calculati onshows good consistence with the asmptotic expansion solution. In addition, taking into consideration of the geoelectric features of the karstic terrain, some kind of digital modelling are made for the synthesis of earth waves in terms of different combinations of electromagnetic and geometric parameters, and whereby the dependence of the amplitude ratio of the lateral to the direct waves upon the freguency of electromagnetic waves, the distance between boreholes, the depth of the measured point, and upon the electrical paramenters has been studied, indicating thus the capability of the double-hole EMmethod to obtain interference curves with apparent extremes for direct and lateral waves in karstic terrain.All inferences in this paper are drawn primarily from the geoelectrical environment of the karstic terrain, but they can be valid for other areas with low absorption media.

Primary dispersion halos from a impregnation type Nb-Ta granite in Hunan have been dealt with in this paper. Using Nb, Ta, W, Sn, Be, Li, Rb, Cs as indicator elements, the author has successfully detected ore anomalies and then delineated ore bodies. As evolution of elements finds expression in ore body associations, abundance of minerals and variations in typomorphic minerals, mineralogical features such as mineral halos and characters of typomorphic minerals seem likely to furnish their own information for ore detection. Vertical zoning of primary halos suggests that, in locating ore bodies, Li, Rb, Cs, Bi, Aa may be used as distant indicator elements whereas Nb, Ta, Be serve well as near-ore indicator elements.

During the soil survey at a scale of 1:50,000 Sn-Pb-Cu-Zn anomalies were found on the east flank of the Huishuiwan overturned anticline axis lying at Huishuiwan, Changning County. On the basis of this geochemical survey a program of IPinvestigation at a scale of 1:10,000 was carried out which led to the delineation of some enriched zones of cassiterite sulphides. All these investigations were reported by verification by drilling. Ten boreholes were drilled within the anomalies and six of them intersected commercial ore-beds with a total thickness of 116.2m. The investigated area seems to be quite promising and the verification is continuing.

Gold was determined by neutron activation method and then used as a direct indicator element for gold deposits in a promising gold area of Shandong Province; some encouraging data obtained in this test are summarized in this paper. The sensibility of neutron activation method for gold is 10^-8 and the efficiency is 9 samples per diem.Induced potential methlod was also performed in this area. In Hedong mining district, a geochemical anomalous zone delimited by a threshold of 0.68g (gold)/t coincided satisfactorily with the induced potential anomaly and the ore body itself; in Wanger shan mining district, the geochemical anomaly was also in conformity with the ore body whereas no induced potential anomaly was recorded; in induced potential anomalies of an unknown area, gold as determined by neutron activation method detected two anomalies (No. Iand No. II), drilling has already discovered an ore body within No. 1 anomaly and will continue to verify the reliability of No. 2 anomaly.

This paper first describes the main characteristics of the magneto telluric method with a review on its evolution from scalar impedance theory to tensor theory, then deals with its data processing and interpretation techniques. The latest advances in this method are mentioned and some field examples given to demonstrate its effectiveness in solving geologic problems of oil-gas exploration.