Intermediate Conducting Layers in the Continental Earth’s Crust—Myths and Reality

Abstract

The nature and scale of intermediate conducting layers propagation in the continental earth’s crust are discussed in this paper. The myth on the existence of intermediate conducting layers in the Earth’s crust at the depth of 10–20 km firstly appeared owing to results of the super-deep dipole-dipole sounding performed in the Gulf of Finland in 1946. Since then for the many decades a large number of anomalies of electrical conductivity in the earth’s crust have been detected. The authors of these studies interpreted the anomalies as the existence of intermediate (sub horizontal) conducting layers of fluidal (or temperature) origin at the depths of the first tens of kilometers, same as in the Gulf of Finland. But analysis of experimental data presented in the article allows to conclude that in most cases the anomalies of electrical conductivity in the Earth’s crust appears due to presence of a steeply dipping electronically conductive sulfide and carbon (graphite) bearing rocks of organic nature («SC-Layer» of Semenov). Fluids exist only in the uppermost part of the continental Earth’s crust in the depth interval from 2–3 to 7–10 km. They are detected as intermediate conductive area associated with the influence of dilatancy-diffusive processes and named as “DD-layer”. The nature of electrical conductivity anomalies in the Earth’s crust represents fundamental problem in the interpretation of the deep sounding data. Solution of the problem determines the role of crustal conductors in the study of geological structure and composition of the Earth’s interior.