On deep electric conductivity of the lithosphere in the Tobol-Ishim interfluve (West Siberia)

On the basis of exploration magnetotelluric soundings (MTS) carried out by the Tyumen Geological Survey in 1980–1981 within the Tobol-Ishim interfluve, the top of the conductive horizon with the electric resistivity of dozens of Ω m is identified in the geoelectrical section at a depth of 75–80 km. Two segments of the locally elevated top of this horizon are revealed. One segment, where the depth of the top of the conductor is 60–65 km, corresponds to the region of the Kiselevskii fault-the main fault in this territory; another segment is associated with the edge zone of the Ishim branch of the Triassic rift system within the West Siberian Plate. Within this segment, the top of the conductive layer rises to a depth of 55-60 km. It is assumed that the Ishim geoelectrical anomaly, which projects into the geothermal anomaly and is coherent with the features of the deep geological structure of its display region, is conditioned by the element of the mantle-crustal magmatogene fluid paleosystem.