Nature of orogenesis and volcanism in the Caucasus region based on results of regional tomography

Solid Earth - Tập 3 Số 2 - Trang 327-337
Iván Koulakov1, Irina Medved1, I. Amanatashvili2, V. Meskhia2
1Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia
2Ilia State University, Tbilisi, Georgia

Tóm tắt

Abstract. In the paper, we discuss the problem of continental collision and related volcanism in the Caucasus and surrounding areas based on the analysis of the upper mantle seismic structure in a recently derived model by Koulakov (2011). This model, which includes P and S-velocity anomalies down to 1000 km depth, was obtained from tomographic inversion of worldwide travel time data from the catalogue of the International Seismological Center. It can be seen that the Caucasus region is squeezed between two continental plates, Arabian to the south and European to the north, which are displayed in the tomographic model as high-velocity bodies down to about 200–250 km depth. On the contrary, a very bright low-velocity anomaly beneath the collision area implies that the lithosphere in this zone is very thin, which is also supported by strong horizontal deformations and crustal thickening indicating weak properties of the lithosphere. In the contact between stable continental and collision zones, we observe a rather complex alternation of seismic anomalies having the shapes of sinking drops. We propose that the convergence process causes crustal thickening and transformation of the lower crust material into the dense eclogite. When achieving a critical mass, the dense eclogitic drops trigger detachment of the mantle lithosphere and its delamination. The observed high-velocity bodies in the upper mantle may indicate the parts of the descending mantle lithosphere which were detached from the edges of the continental lithosphere plates. Very thin, or even absent, mantle parts of the lithosphere leads to the presence of hot asthenosphere just below the crust. The crustal shortening and eclogitisation of the lower crustal layer leads to the dominantly felsic composition of the crust which is favourable for the upward heat transport from the mantle. This, and also the factors of frictional heating and the radioactivity of felsic rocks, may be the origin of volcanic centres in the Caucasus and surrounding collisional areas.

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Tài liệu tham khảo

Adamia, S. A., Chkhotua, T., Kekelia, M., Lordkipanidze, M., Shavishvili, I., and Zakariadze, G.: Tectonics of the Caucasus and adjoining regions: implications for the evolution of the Tethys ocean, J. Struct. Geol., 3, 437–447, 1981.

Adamia, S. A., Zakariadze, G., Chkhotua, T., Sadradze, N., Tsereteli, N., Chabukiani, A., and Gventsadze, A.: Geology of the Caucasus: A Review, Turkish Journal of Earth Sciences, 20, 489–544, 2011a.

Adamia, S. A.: Plate tectonics and evolution of the Alpine system: discussion, Geol. Soc. Am. Bull., 86, 719–720, 1975.

Adamia, S. A., Mumladze, T., Sadradze, N., Tsereteli, E., Tsereteli, N., and Varazanashvili, O.: Late Cenozoic tectonics and geodynamics of Georgia (SW Caucasus), Georgian International Journal of Sciences and Technology 1, 77–107, 2008.

Al-Lazki, A. I., Sandvol, E., Seber, D., Barazangi, M., Turkelli, N., and Mohamad, R.: Pn tomographic imaging of mantle lid velocity and anisotropy at the junction of the Arabian, Eurasian and African plates, Geophys. J. Int., 158, 1024–1040, 2004.

Allen, M., Jackson, J., and Walker, R.: Late Cenozoic reorganization of the Arabia-Eurasia collision and the comparison of short-term and long-term deformation rates, Tectonics, 23, 1–16, 2004.

Artemieva, I. M.: Lithospheric structure, composition, and thermal regime of the East European craton: Implications for the subsidence of the Russian Platform, Earth Planet. Sci. Lett., 213, 429–444, 2003.

Babeyko, A. Y. and Sobolev, S. V.: Quantifying different modes of the late Cenozoic shortening in the central Andes, Geology, 33, 621–624, 2005.

Babeyko, A. Y., Sobolev, S. V., Trumbull, R. B., Oncken, O., and Lavier, L.: Numerical models of crustal scale convection and partial melting beneath the Altiplano-Puna plateau, Earth Planet. Sci. Lett., 199, 373–388, 2002.

Burov, E. B. and Diament, M.: The effective elastic thickness (Te) of continental lithosphere: What does it really mean?, J. Geophys. Res., 100, 3905–3928, https://doi.org/10.1029/94JB02770, 1995.

Burov, E. B. and A. B. Watts: "The long-term strength of continental lithosphere: "jelly sandwich" or "crème-br\\^{u}lé"?", GSA Today, 16, 4–10, 2006

DeMets, C., Gordon, R., Argus, D., and Stein, S.: Current plate motions, Geophys. J. Int., 101, 425–478, 1990.

Dewey, J. F. and Bird, J. M.: Mountain belts and new global tectonics. J. Geophys. Res., 74, 2625–2467, 1970.

Dewey, J. F., Hempton, M. R., Kidd, W. S. F., Saroglu, F., and Şengör, A. M. C.: Short,ening of continental lithosphere: The neotectonics of eastern Anatolia – A young collision zone, in: Collision Tectonics, edited by: Coward, M. P. and Ries, A. C., London, Geol. Soc. London, 3–36, 1986.

Djanelidze, C., Klopotovskaya, N., and Maisuradze, G.: Holocene volcanites and lake beds near Goristsikhe settlement, International Union for Quarternary Research (INQUA), 11th Congress Guidebook for Excursion A-16, 28–31, 1982.

England, P. C. and Houseman, G. A.: Extension during continental convergence with application to the Tibetan Plateau, J. Geophys. Res., 94, 17561–17579, 1989.

Ershov, A. V. and Nikishin, A. M.: Recent Geodynamics of the Caucasus-Arabia-East Africa Region, Geotectonics, 38, 123–136, 2004.

Forte, A., Cowgill, E., Bernardin, T., Kreylos, O., and Hamann, B.: Late Cenozoic deformation of Kura fold-thrust belt, southern Greater Caucasus, Geol. Soc. Am. Bull., 122, 465–486, 2010.

Gök, R., Sandvol, E., Türkelli, N., Seber, D., and Barazangi, M.: Sn attenuation in the Anatolian and Iranian plateau and surrounding regions, Geophys. Res. Lett., 30, 8042, https://doi.org/10.1029/2003GL018020, 2003.

Hearn, T. M. and Ni, J.: Pn velocities beneath continental collision zones: The Turkish-Iranian plateau, Geophys. J. Int., 117, 273–283, 1994.

Innocenti, F., Mazzuoli, R., Pasquare, G., Radicati, F., and Villari, L.: Tertiary and Quaternary volcanism of the Erzurum-Kars area (Eastern Turkey). Geochronological data and geodynamic evolution, J. Volcanol. Geoth. Res., 13, 223–240, 1982.

International Seismological Centre, Bulletin Disks 1-9 [CD-ROM], Internatl. Seis. Cent., Thatcham, United Kingdom, 2001.

Jull, M. and Kelemen, P. B.: On the conditions for lower crustal convective instability, J. Geophys. Res. 106, 6423–6446, 2001.

Kay, R. W. and Kay, S. M.: Delamination and delamination magmatism, Tectonophysics, 219, 177–189, 1993.

Keskn, M., Pearce, J. A., and Mitchell, J. G.: Volcanostratigraphy and geochemistry of collision-related volcanism on the Erzurum-Kars Plateau, North Eastern Turkey, J. Volcanol. Geoth. Res., 85, 355–404, 1998.

Khain, V.: Structure and main stages in the tectono-magmatic development of the Caucasus: an attempt at geodynamic interpretation, Am. J. Sci., 275-A, 131–156, 1975.

Koronovsky, H. and Demina, L.: Disappeared Pliocene volcanoes of the Main Caucasian Range and grandiose explosion of the Kazbegi at the beginning of Pleistocene (North Caucasus) Problems of Geodynamics, Petrography and Metallogeny of the Caucasus, Proceedings of the Scientifi c Sessions, Baki, 92–103, 2007. (in Russian),

Koulakov, I.: High-frequency P and S velocity anomalies in the upper mantle beneath Asia from inversion of worldwide traveltime data, J. Geophys. Res., 116, B04301, https://doi.org/10.1029/2010JB007938, 2011.

Koulakov, I. and Sobolev, S. V.: A Tomographic Image of Indian Lithosphere Break-off beneath the Pamir Hindukush Region, Geophys. J. Int., 164, 425–440, 2006.

Lavier, L. L. and Steckler, M. S.: The effect of sedimentary cover on the flexural strength of continental lithosphere, Nature 389, 476–479, https://doi.org/10.1038/39004, 1997.

Lebedev, V., Chernishev, I., Dudauri, O., Arakelyants, M., Chugaev, A., Golzman, Y., and Vashakidze, G.: Geochronology of Neogene-Quaternary dacitic volcanism of the Javakheti highland (Lesser Caucasus, South Georgia), Proceedings of Geological Institute of Academy of Sciences of Georgia, 119, 535–544, 2004. (in Russian)

Lebedev, V., Bubnov, S., Dudauri, O., and Vashakidze, G.: Geochronology of Pliocene volcanism of Javakheti highland (Lesser Caucasus). Article 2. Eastern part of the Javakheti highland, Regional Geological Correlation, Stratigraphy, Geol. Correl., 16, 101–123, 2008. (in Russian)

Maggi, A. and Priestley, K.: Surface waveform tomography of the Turkish-Iranian plateau, Geophys. J. Int. 160: 1068–1080, 2005.

Neprochnov, Y. P., Kosminskaya, I. P., and Malovitsky, Y. P.: Structure of the crust and upper mantle of the Black and Caspian seas, Tectonophysics, 10, 517–538, 1970.

Pearce, J., Bender, J., De Long, S., Kidd, W., Low, P., Guner, Y., Saroglu, F., Yilmaz, Y., Moorbath, S., and Mitchell, J.: Genesis of collision volcanism in Eastern Anatolia, Turkey, J. Volcanol. Geoth. Res., 44, 189–229, 1990.

Sandvol, E., Al-Damegh, K., Calvert, A., Seber, D., Barazangi, M., Mohamad, R., Gok, R., Turkelli, N., and Gurbuz, C.: Tomographic omaging of Lg and Sn propagation in the Middle East, Pure Appl. Geophys., 158, 1121–1163, 2001.

Sarker, G. and Abers, G. A.: Deep structures along the boundary of a collisional belt: attenuation tomography of P and S waves in the Greater Caucasus, Geophys. J. Int., 133, 326–340, https://doi.org/10.1046/j.1365-246X.1998.00506.x, 1998.

Sobolev, S. V. and Babeyko, A. Y.: What drives orogeny in the Andes?, Geology, 33, 617–620, 2005.

Sobolev, S. V., Babeyko, A. Y., Koulakov, I., and Oncken, O.: Mechanism of the Andean orogeny: insight from the numerical modelling, in: The Andes – Active Subduction Orogeny, edited by: Oncken, O., Chong, G., Franz, G., Giese, P., Götze, H.-J., Ramos, V. A., Strecker, M. R., and Wigger, P., Frontiers in Earth Sciences, 1, Springer, 513–535, 2006.

Stüwe, K.: Heat sources of Cretaceous metamorphism in the Eastern Alps – a discussion, Tectonophysics, 287, 251–269, 1998.

Tutberidze, B.: Geology and Petrology of Alpine Late Orogenic Magmatism of the Central Part of Caucasian Segment, Tbilisi University Publishers, Tbilisi, 1–340, 2004. (in Russian)

Villasenor, A., Ritzwoller, M. H., Levshin, A. L., Barmin, M. P., Engdahl, E. R., Spakman, W., and Trampert, J.: Shear velocity structure of central Eurasia from inversion of surface wave velocities, Phys. Earth Planet. Int., 123, 169–184, 2001.

Zakariadze, G., Dlek, Y., Adamia, S., Oberhansli, R., Karpenko, S., Bazylev, B., and Solov'eva, N.: Geochemistry and geochronology of the Neoproterozoic Pan-African Transcaucasian Massif (Republic of Georgia) and implications for island-arc evolution of the late Precambrian Arabian-Nubian Shield, Gondwana Res., 11, 97–108, 2007.