Nature of electrical conductivity of the ancient crystalline base

The generalized popular image of conductivity structure of the crystalline as a tripartite section (high-low-high conductivity of top, middle, and bottom of the base, respectively) is disqualified significantly by recent soundings, in the USSR and elsewhere, by too many exceptions to the rule. The most plausible explanation of such three-dimensional exceptions is the presence of electron-conducting minerals and formations in different positions at great depths, which may affect conductivities of the entire profile.