Conductivity anomalies in the Baltic Shield in Finland

In 1981–84 six arrays of 30 or 31 magnetometers were operated on the Baitic Shield in central and southern Finland to deduce information about the electrical conductivity within the Earth's crust. The magnetometer sites cover the area with 20–60 km spacing allowing the identification of large-scale electrical structures within the crust. Each array recorded the three orthogonal magnetic field components on analogue film for about two months simultaneously at all the stations. Altogether 17 magnetic variation events of 2–6hr length have been digitized and analysed.
This paper includes results of the last array in south-western Finland, a comparison of two methods of induction vector estimation and combination of results from all the arrays. Four zones of anomalously high electrical conductivity have been observed. They are all interpreted as lying at depths greater than 5 km. The 'Oulu Anomaly' is wider than the others and rather short, about 100 km. The 'Southern Finland Anomaly' is probably a 500 km-long narrow zone. This and the 'Ostrobothnian Anomaly' surround three sides of the large Central Finland Granite area. The 'Outokumpu Anomaly' is probably deeper lying than the others. Blocks separated by these anomalies are presented. The blocks have different average resistivities.     

磁通门磁力仪在野外安装的实施方案

“十五”期间,我国分别在四川西昌、甘肃天祝和重庆三峡地区架设地磁台阵3个,约27个台点。密集型地磁台阵野外架设条件要求相对较高,在我国尚无完整可靠方案供参考。笔者依靠四川西昌台阵建设实际情况,进行野外模拟实验安装,对安装中的材料、方法和注意事项进行了分析,初步形成了一套较为实用的架设方法。     

Exploring Placer Gold Deposits through Integrated Geophysical and Geochemical Techniques at the Confluence of the Indus and Kabul Rivers, NW Pakistan

Analysis of the anomalous magnetic mineral intensities and geochemistry for placer gold deposits are presented for those of the Attock area at the confluence of the Indus and Kabul rivers in northwestern Pakistan. Two grids covering an area of 10x18 m2 and 8x10 m2 were analyzed using a G-858 Cesium Vapor Magnetometer. The anomalous zones obtained were plotted on contour maps, 2D and 3D magnetic intensity maps. Based on the magnetic anomalies, grid-1 of the study area was sampled at three different anomalous zones for geochemical analysis. These zones contain gold concentrations, ranging from 2.11 ppm to 6.109 ppm with an average of 4.01 ppm. Increase in gold concentration in the subsurface within the anomalous zones indicates that magnetometer survey followed by a geochemical analysis can potentially narrow down the gold-bearing anomalous zones.