On the deep seated faults in the Northern Caucasus

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 Varisсan (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.

1. Adamia Sh.A. (1968) Doyurskie obrazovaniya Kavkaza [Pre-Jurasic formations of Caucasus]. Tbilisi, Metsniere-ba Publ., 294 p. (In Russian)

2. Adamia Sh., Belov A.A., Lordkipanidze M., Somin M.L. (1982) Field excursion Guidebook of International Working meeting on the Caucasus. Project No. 5 IGCP Tbilisi publ., 84 p.

3. Andreev V.K., Baranov G. I., Grekov I.I., Ermakov V.A., Litovko G.V., Oslopov D.S., Prokuronov P.V., Saakov V.G., Snezhko V.A., Shempelev A.G., En-na N.L. (1999) Geologicheskii atlas Severnogo Kavkaza. Masshtab 1 : 1 000 000. Ob”yasnitel’naya zapis-ka [Geological Atlas of the Northern Caucasus. Scale 1 : 1 000 000. Explanatory note]. Essentuki, Regional Publ., 130 p. (In Russian)

4. Aubin Jean. (1965) Geosinclines. Developments in Geotectonics. Elseiver Publ. Amsterdam-London-New New York.

5. Azhgirei G.D., Baranov G.I, Kropachev S.M., Panov D.I., Sedenko S.M. (1976) Geologiya Bol’shogo Kavkaza [The Geology of Greater Caucasus]. Moscow, Nedra Publ., 263 p. (In Russian)

6. Baranov G.I. (1968) Tectonics. The structure of the basement, Front Range zone. Geologiya SSSR, t. IX [The Geology of USSR, vol. IX]. Moscow, Nedra Publ., 608618. (In Russian)

7. Baranov G.I. (1991) Tectonic researches in the North Caucasus. Tezisy dokladov VII konferentsii po geologii i poleznym iskopaemym Severnogo Kavkaza [Thesis of reports on Geology and mineral resources of the North Caucasus of the VII Regional conference]. Essentuki Region. Publ., 91-93. (In Russian)

8. Baranov G.I., Grekov I.I. (1980) Pre-Upper-Paleozoic structure of the North Caucasus. Tektonika Sredizemnomorsk-ogopoyasa [Tectonics of the Mediterranean belt]. Moscow, Nauka Publ., 162-171. (In Russian)

9. Baranov G.I., Omel chenko V.L., Prutskii N.I. (1995) The tectonic events sequence and their expression in the present North Caucasian structure. Osnovnye problemy geo-logicheskogo izucheniya i ispolzovaniya nedr Sev. Kavkaza [The main problems of geologic explorations and using North Caucasian resources]. Essentuki Region. Publ., 63-65. (In Russian)

10. Belov A.A., Omel’chenko V.L. (1976) Ophiolites in the Marukh nappe structure and some questions of the stratigraphy and magmatism of the Front Range Paleozoic of the Northern Caucasus. Geotectonics, 41(2), 60-70.

11. Belov A.A., Omel’chenko V.L. (1986) Late-Variscan and Post-Variscan overthrusts in the Pre-Upper-Paleozoic basement of the North Caucasus. Izv. Vyssh. Uchebn. Zaved. Geology, Exploration, (9), 14-20. (In Russian)

12. Belousov V.V., Troshikhin B.M. (1937) A brief geological sketch of the area Pshekha and Belaja in the North-West Caucasus. Zapiski VMO. Ser. 2. Ch. XVI, (4). (In Russian)

13. Dotduev S.I. (1986) On the nappe structure of the Greater Caucasus. Geotectonics, (2), 94-106. (In Russian)

14. Gamkrelidze I.P, Shengeliya D.M. (2005) Dokembriisko-pa-leozoiskii regionalnyi metamorphism, granitoidnyi magmatism i geodinamika Kavkaza [Precambrian-Paleoso-ic regional metamorphism, granitoid magmatism and geodynamics of the Caucasus]. Moscow, Nauchnyi mir Publ., 460 p. (In Russian)

15. Geological handbook. V. 2. (1955) Moscow, Gosgeoltekhiz-dat Publ., 204 (In Russian)

16. Geological handbook. V. 1. (1973) Moscow, Nedra Publ., 175-176. (In Russian)

17. Geological handbook. V. 1. (2010) St.Petersburg, VSEGEI Publ., 271-272. (In Russian)

18. Goguel J. (1965) Traite de tectonique. Masson et Cie- edi-teurs, Paris, 457 p.

19. Gogel’ Zh. (1969) Osnovy tektoniki [The basics of tectonics]. Moscow, Mir Publ., 440 с. (In Russian)

20. Grekov I.I., Kropachev S.M., Momot S.P., Koren’ T.N. (1974) Marukh nappe in Paleozoic of North Caucasus. Sovetskaya geologiya, (2), 77-84. (In Russian)

21. Grekov I.I., Prutskii N.I., Enna N.L. (2005) Northern Caucasus geothermal zoning and tectonodynamics (An attempt of the geological interpretation of the convective heat flow). Regional’naya geologiya i metallogeni-ya [Regional Geology and Metallogeny]. St.Petersburg, VSEGEI Publ., (25), 52-59. (In Russian)

22. International tectonic lexicon. Introductory issue. (1979) Edi-or-in-chief: J.G. Dennis. E. Schweizerbart sche Verlagsbuchhandlung (Nagele u.Obermiller). Stutgart, 142 p.

23. Kamzolkin V.A., Somin M.L., Latyshev A.V., Vidya-pin Ju.P., Ivanov S.D. (2018) About the discovery of the Late-Wendian basement within Blyb metamorphic complex of Front Range and prerequisites of the Armov tectonic nappe identification. Problemy tektoniki i geodi-namiki zemnoi kory i mantii. Materialy Tektonicheskogo soveshchaniya. Tom I [Problems of tectonics and geodynamics of the Earth’s crust and mantle. Materials of tectonic conference. Vol. I]. Moscow, GEOS Publ., 251-255. (In Russian)

24. Khain V.E., Mikhailov A.E. (1985) Obshchaya geotektoni-ka [General geotectonics]. Moscow, Nedra Publ., 326 p. (In Russian)

25. Lavrishchev V.A., Prutskii N.I., Semenov V.M., Bashkirov A.N., Grekov I.I., Chernykh V.I., Prokuronov P.V., Saakov V.G. (2002) Gosudarstvennaya geologicheskaya karta RFmasshtaba 1: 200 000. List K-37-V. (Krasnaya Polyana) [State Geologic Map of RF of Scale 1 : 200 000. Sheet K-37-V. Explonatory note]. St.Peterburg, VSEGEI Publ., 213 p. (In Russian)

26. Leonov M.G. (2007) Tectonic-gravitational mixtites of central segment of Southern slope of Great Caucasus. Bol’shoi Kavkaz v alpiiskuyu epokhu, glava 6 [Alpine History of Great Caucasus, chapter 6]. Moscow, GEOS Publ., 231-250. (In Russian).

27. Leonov Yu.G. (2007) Cimmerian and late Alpine tectonics of the Greater Caucasus. Bol’shoi Kavkaz v alpiiskuyu epokhu, glava 9 [Alpine History of Great Caucasus, chapter 9]. Moscow, GeOS Publ., 317-340. (In Russian).

28. Makarovskii O.V. (1982) Structure of Main overthrust zone of Greater Caucasus in Abkhazia. Izv. AN SSSR, Ser. Geol., (5), 111-116. (In Russian)

29. Milanovskii E.E., Khain V.E. (1963) Geologicheskoe stroe-nie Kavkaza [Geological structure of the Caucasus]. Moscow, Moscow Stat. Univ. Publ., 357 p. (In Russian)

30. Miashiro Akiho, Aki Keiti, §engёr A.M. (1982) Orogeny. Chichester, John Willey &Sons Limited Publ.

31. Omel’chenko V.L. (2007) Position of the Blyb Complex in the Pre-Mesozoic Crustal Structure of the Front Range Zone in the Northern Caucasus. Geotectonics, 41(4), 306-314.

32. Omel’chenko V.L. (2011) Geologicheskoe stroenie Tsen-tralnogo Kavkaza. Sovremennye predstavleniya o geolo-gii i metallogenii regiona [Geologic structure of Central Caucasus. Modern ideas about geology and metallogeny of region]. LAP LAMBERT Academic Publishing. Saar-brucken, 222 p. (In Russian)

33. Omel’chenko V.L., Riabov G.V., Isaev V.S. (2017a) Tectonics and geologic evolution of the Front Range Zone of the Greater Caucasus. Geologiya i geofisika Yuga Rossii, (1) 40-56. (In Russian)

34. Omel’chenko V.L., Riabov G.V., Isaev V.S. (20176) On possible oil and gas potential of the ancient core of the Greater Caucasus. Sovremennye problemy geologii, geo-fiziki i geoekologii Severnogo Kavkaza [Present problems of geology, geophysics and geoecology of Northern Caucasus. Vol. VII, pt 1]. Moscow, Nauka Publ., 159170. (In Russian)

35. Peive A.V. (1945) New data on tectonics of the Southern slope of the Central Caucasus. Sovetskaya geologiya, (7), 23-46. (In Russian).

36. Pis’mennyi A.N., Pichuzhkov A.N., Zarubina M.A., Gorbachev M.A., Verdi S.N., Grekov I.I., Gamasa Ju.N. (2004) Gosudarstvennaya geologicheskaya karta RF masshtaba 1 : 200 000. List K-38-I, VII (Kislovodsk) [State Geologic map of RF of Scale 1 : 200 000. Sheets K-38-I, VII. Explonanory note]. St.Petersburg, VSEGEI Publ., 275 p. (In Russian)

37. Read H.H., Watson J. (1975) Earth History. Part II. Later Stages of Earth History. The Macmillan press LTD, London, 221 p.

38. Rutten M.G. (1969) The Geology of Western Europe Elsei-ver Publ. Amsterdam-London-New New York.

39. Shempelev A.G. (1978) On the deep expression of the Main Caucasian overthrust. Geotektonika, (6), 57-65. (In Russian)

40. Somin M.L. (2007) Strukturnaya pozitsiya i geodinami-cheskie usloviya formirovaniya metamorficheskikh kom-pleksov Bol ’shogo Kavkaza i Kuby. Dis. ... doct. geol.-min. nauk [Structural position and geodynamic conditions of formation of metamorphic complexes of the Greater Caucasus and Cuba. Dr. geol. and min. sci. diss.]. Institute of the Earth physics, RAN, 56 p. (In Russian)

41. Terminy i ponyatiya, ispolzuemye pri prognozno-metallo-genicheskikh issledovaniyakh [Terms and concepts used in the prognostication and metallogenic studies]. (1991) (Eds. A.I. Krivtsov and V.M. Terentiev). St.Petersburg, VSEGEI Publ., 188 p. (In Russian)

42. Vidyapin Yu.P., Somin M.L. (2007) The structure of the Main Caucasian fault (“overthrust of the Main Range”) in the Sancharo-Avadkhara region (NW Caucasus). Bull. MOIP, Sect. Geol., 82(2), 13-20. (In Russian)