37. Multi-Electrode Electrical Profiling Results in the Northern Ladoga Area

DC electrical profiling with the use of Method of External Sliding Dipole (MESD) has been made along the profile Sevastyanovo-Hijtola-Sujstamo of 200 km length. The profile crosses the Ladoga anomaly of high conductivity. Interpretation of MESD results is performed in two stages. At the first stage, a one-dimensional inverse problem is solved using the Zohdy procedure (Zohdy 1989). The starting model is set in the form of a multilayered section with the number of layers equal to the number of deletions from the feeding line plus one (first) layer for the results of measurements inside the line. The depths to the base of the layers and their resistivity are taken equal to the corresponding values of the effective distances and to the apparent resistivity at corresponding distance. Further, an iterative selection of the theoretical model of the medium occurs before obtaining agreement with the experimental data within the error of observations. At the second stage, a quasi-2D section is constructed by symmetrically shifting the deep sounding centers with relation to the supply line AB to the southwest and northeast as the receiving dipoles MN move in opposite directions. The results of profiling, as well as the results of the study of samples from outcrops and boreholes, indicate the connection of anomalies with the presence of electron-conducting sulphide-carbonaceous rocks. Obviously, they explain the nature of the upper part of the regional Ladoga conductivity anomaly.