The New Data on the Structure of the Continental Crust Based on the Results of Electromagnetic Sounding with the Use of Powerful Controlled Sources

摘要

On the basis of the summarized results of multiannual deep soundings with the use of powerful controlled sources, it is suggested to subdivide the Earth's crust, which is traditionally identified by seismic data, into two parts, namely, upper and lower. The upper crust of 10-15 km thick is more conductive and is the most actively involved in geologic processes. Its principal peculiarities are sharp horizontal heterogeneity and a wide range of variations of specific electric resistance for rocks (from 1 to 10~5 Ohm m), a higher brittle-ness, and the presence of fluids that drain the suprastructure from the day surface owing to the supply of meteor waters to depths. The lower crust (in the depth interval from 10-15 to 35-45 km) is distinctive by the high specific electric resistance (10~5-10~6 Ohm m) and horizontal homogeneity of electric properties. Electric conductivity of the lower crust is mostly determined by the influence of planetary physical-chemical parameters (pressure, temperature, viscosity), phase transitions of substances, and geodynamic peculiarities of evolution for different segments of the Earth, rather than by geologic processes observed near the day surface.