On the deep seated faults in the Northern Caucasus

Abstract

Research subject . The paper describes large tectonic zones in the North Caucasus, which can be classified as deep faults according to a number of features. Among these formations are the Ancient axial fault zone earlier described by G.D. Azh-girei, which we attributed to Hercynian structures (with the presence of pre-Paleozoic); the Indosinian axial fault zone and the Main Caucasian fault (overthrust). Materials and methods . The Ancient axial fault zone is considered as a suture zone, which arose as a result of Varis с an (Hercynian) folding during the interaction of the Transcaucasian and East European tectonic plates (EETP). The Indosinian axial fault zone contains fragments of Variscan nappes and neoautochthonous deposits of the same age. Results. The surface manifestation of the Indosinian axial fault zone was a tectonic-formational zone of the Front Range, which is located at the junction, on one side, with the newly formed hard crystalline massif crust at the site of the Ancient zone (Main Range), and, on the other side, with EETP. This zone continued to be active later, during the Cimmerian and Alpine tectonic events. At the same time, the formation of new granite magmatic melts could occur. The driving mechanism is assumed to have been opposite undercrust convection flows. Although there are conflicting views on the Main Caucasian fault, it seems clear that this was a deep-seated and magma-producing zone at the pre-Callovian time. This fault is likely to have been formed as a consequence of the intraplate subduction, which is continuing at present. Conclusions. The presence of hyperbasite bodies in the fault zones under consideration is not a sign of their depth in the Caucasus. In the present structure, the mixtite zone lying under the flysch of the southern slope of the Greater Caucasus and overlapping the Transcaucasian massif can be considered as a large collision line currently under development. Some other faults present in the region, which are supposed to be deep, have also been considered.