ИСТИНА

The structure and nature of Ladoga anomaly has been the object of research for more than 40 years. In recent years, significant progress has been made thanks to the synchronous MT-MV profiling carried out by the LADOGA working group on the Vyborg-Suojärvi trace [Sokolova et al., 2016], as well as the shallow DC profiling with the use of multi electrode installations in combination with AMT soundings [Zhamaletdinov et al., 2018]. High electrical conductivity of the upper part of the section (up to 1-2 km) has been explained by the presence of electronically-conductive sulfide and graphite-bearing rocks. The most popular hypothesis about the nature of the deeper part of the anomaly (about 20 km) was a fluid one, presented by B.N. Klabukov (2006). However, this treatment faces a whole series of contradictions in the terms of petrology, rheology, information on the heat flux, etc. [Yardley & Valley, 1997; Artemieva, Shulgin, 2015; Pavlenkova, 1996; Karakin et al., 2002]. The modern MT-MV sounding experiment of the LADOGA group, made it possible to construct a new sufficiently resolved model of Lake Ladoga anomaly resistivity cross-section. In this model the deep conductivity structure is represented by a series of inhomogeneous conductive tectonic plates gently dipping to SW and interpreted as a series of thrusts developed along the Early Proterozoic formations containing graphite in their composition by [Mints, Sokolova et al., 2018]. At the same time, graphite plays the role of "lubricant", which facilitates the slipping of Proterozoic metamorphic plates during accretion (thrusting) of to the edge of the Karelian craton in the Svekofenian time and later.