Non-Plate-Tectonic (Autonomous) Folding and Thrusting in the Earth’s Crust

The formation of fold–thrust dislocations of stratified rocks in the Earth’s crust has been considered as a consequence of the lateral compression of such rocks by converging platforms or lithospheric plates over the last 150 years within the framework of a geosyncline concept and then according to the concept of plate tectonics. Such convergences are reliably confirmed by current geodetic measurements. At the same time there are less popular ideas that present the formation of these dislocations as a result of various local, autonomous processes. The essence of the problem is that the domination of directionally ordered horizontal compression over the value of lithostatic pressure in the Earth’s crust, which is unambiguously determined according to the data of focal mechanisms of earthquakes and in the measurements on stresses in situ in mine workings, makes it necessary to prefer the global mechanism of compression in the form of convergence of horizontally moving lithospheric plates. This convergence is reliably established on a global scale and by modern high-precision geodetic GPS measurements. However, similar GPS measurements, but on regional or local networks rather than on global ones, have shown an opposite result in a few cases. They revealed an increase in the width of representative segments of the mountain belts, rather than a decrease. A detailed study of the geological structure of such areas has indicated that the main role in their formation is played by scaly thrusts, sometimes transforming into small covers, and linear folds and groups of such folds associated with these dislocations and subordinate to them. The formation of such a cover-thrust tectonic structure continues now. For several years, the authors have developed a hypothesis according to which fold–thrust dislocations in the Earth’s crust are formed as a result of an increase in the volume of stratified rocks and as a consequence of an increase in the area of these rocks. They cause volume expansion stresses, similar to the stresses of external compression; crumple; and are dissected by thrusts and reverse faults, tending to cover adjacent territories. It is assumed that the increase in the volume (volume expansion) and the areas of stratified rocks is a result of the entry of additional mineral material with ascending flows of deep mineralized fluids. The increase in the volume and the width of the mountain structure during the formation of its tectonic structure is indirectly confirmed by the near-vertical formations detected in the Earth’s crust in several regions by geophysical methods, which have different velocity characteristics compared to the enclosing environment. These formations can be interpreted as channels of permeability for the penetration of deep fluids—the cause of an increase in rock volume. This suggests that the process of autonomous folding and thrusting in the Earth’s crust really exists in the regional plan, first and foremost, within the mobile mountain belts, along with a global plate-tectonic mechanism.