COLLISIONAL VOLCANISM OF CAUCASIAN SECTOR IN ALPINE FOLDED BELT
DOI:
https://doi.org/10.17721/1728-2713.66.02Keywords:
collision, volcanism, Caucasian segment, Alpine fold-and-thrust beltAbstract
Subaerial volcanism within the Caucasian segment of the Alpine fold-and-thrust belt has occurred in overall meridional compression up to the present time. Collisions characteristic of the Late Miocene changed the nature of subduction and caused a complex pattern of extensional stress fields, with SW and SE shear zones, sublatitudinal shears, and thrusts of the Caucasian orientation being predominant. There are singled out meridional compression areas to match local areas of extensional shear zones. Surficial manifestations of volcanism are commonly linked to the environments of local extension into regional area of submeridional compression. Collisional volcanites relating generally to the calc-alkaline series have geochemical features characteristic of both subduction zone rocks and continental rift rocks. The ratio of Si, K, Mg and Ti oxides on the ternary diagram shows collisional volcanites proper to be located between the fields of subductional volcanites and volcanites of continental rifts. Collisional volcanites have distinctive geological features: 1) Minor manifestation of fractional crystallizations (if any). 2) Antidromic sequence of volcanic eruptions (decrease in the silica content and increase in alkalinity). 3) High concentration of non-coherent and LRRE elements in basic rocks. 4) Low depths of basaltic magma generation. 5) Considerable lateral heterogeneity in the chemical composition of volcanites. Tholeiites tend to increase southwards, while geodynamic environment evolves in continental rifting. The principal reason for lateral heterogeneity could be found in various types of melting, metasomatism, substratum and crystalline basement, change of pressure-temperature conditions, and magma chambers. Andesite-dacite melts undergo subsequent heating from 750-850°С to 1150°С and an increase in the internal pressure from 0.6-0.8 GPa to 1.5 GPa. The basalts of the Caucasian segment, compared with the basalts of other geodynamic environment, are significantly enriched with Zr, which allows including fields of continental collisional volcanites to common discriminative Zr-Ti, Zr-Y, Zr-Ti-Y diagrams. There is a geochemical distinction between continental collisional volcanites of the Caucasus and suprasubduction rocks of the island arcs – a decrease in LREE content and differentiation shifting from basic to acid rocks.
References
Demina L.I. Koronovskiy N.V., (1998). Evolution of magmatic melts in conditions of continental collision [Evolyutsiya magmaticheskikh rasplavov v usloviyakh kontinental'noy kollizii]. Izvestiya sektsii nauk o Zemle RAYEN – Proceedings of the Section of Earth Sciences RAS, 1, 106–121 (In Russian).
Demina L.I., Simonov D.A., (1999). Volcanics as indicators of process of continental collision [Vulkanity kak indikatory protsessa kontinental'noy kollizii]. Dokl. RAN – Reports RAS, 366, 6, 793–796 (In Russian).
Ivanov D.A., Bubnov S.N., Volkova V.M. et al., (1993). The isotopic composition of strontium and neodymium in quaternary lavas of the Greater Caucasus in connection with the problem of their petrogenesis [Izotopnyy sostav strontsiya i neodima v chetvertichnykh lavakh Bol'shogo Kavkaza v svyazi s problemoy ikh petrogenezisa]. Geokhimiya – Geochemistry, 3, 343–352 (In Russian).
Kengerli T.N., (1995). New interpretation of geological and tectonic structure of the South-Western Caucasus. Major problems exploration and use of mineral resources of the North Caucasus [Novaya interpretatsiya geologo-tektonicheskogo stroyeniya YugoZapadnogo Kavkaza. Osnovnyye problemy geologicheskogo izucheniya i ispol'zovaniya nedr Severnogo Kavkaza]. Sevkavgeologiya Publishing, Yessentuki, 302-304 (In Russian).
Koronovskiy N.V., (1968). Geological structure and history of development of Volcano Elbrus. Elbrus glaciation [Geologicheskoye stroyeniye i istoriya razvitiya vulkana El'brus. Oledeneniye El'brusa]. МGU Publishing, Moscow, 346 (In Russian).
Koronovskiy N.V., Demina L.I., (1999). Collisional stage of the Caucasian sector Alpine orogen: geodynamics and magmatism [Kollizionnyy etap razvitiya Kavkazskogo sektora Al'piyskogo skladchatogo poyasa: geodinamika i magmatizm]. Geotektonika – Geotectonics, 2, 1735 (In Russian).
Koronovskiy N.V., Demina L.I., (2004). Igneous petrogenesis collision stage development of the Caucasus. Modern problems of geology [Magmaticheskiy petrogenezis kollizionnogo etapa razvitiya Kavkaza. Sovremennyye problemy geologii]. Trudy geologicheskogo instituta RAN – Proceedings of the Geological Institute of RAS, 565, 370-391 (In Russian).
Koronovskiy N.V., Demina L.I., (1996). Model collisional volcanism of Caucasus segment of the Alpine belt [Model' kollizionnogo vulkanizma Kavkazskogo segmenta Al'piyskogo poyasa]. Dokl. RAN – Reports RAS, 350, 4, 519–522 (In Russian).
Milanovskiy Ye.Ye., Koronovskiy N.V., (1973). Orogenic volcanism and tectonics of the Alpine belt of Eurasia [Orogennyy vulkanizm i tektonika Al'piyskogo poyasa Yevrazii]. Nedra Publishing, Moscow, 280 (In Russian).
Popov V.S., Semina V.A., Nikolayenko YU.S., (1987). Geochemistry lof atest Caucasus volcanics and their origin. Geochemistry continental volcanism [Geokhimiya noveyshikh vulkanitov Kavkaza i ikh proiskhozhdeniye. Geokhimiya kontinental'nogo vulkanizma]. Nauka Publishing, Moscow, 5, 240 (In Russian).
Fel'dman I.S., (1996). Dehydration and electrical conductivity: presuppositions and consequences. Geophysical prerequisites and consequences of crustal dehydration [Degidratatsiya i elektroprovodnost': predposylki i sledstviya. Geofiz. predposylki i sledstviya degidratatsii zemnoy kory]. Abstracts of the International meeting, Moscow, 1996, (In Russian).
Irvine T.N., Barager W.R.A.D., (1971). Chemical classification of the common volcanic rocks. J. Earth Sci., Canada, 8, 523–548.
Miyashiro A., (1974). Volcanic rock series in island arcs and active continental margine. Amer.J. of Sci., 274, 321–355.
Pearce J.A., Bender J.F., De Long S.E. et al., (1990). Genesis of collision volcanism in Eastern Anatolia. Jour. of Volcanol. and Geotherm. Res., Turkey, 44, 189–229.
Pearce J.A., Cann J.A., (1973). Tectonic setting of basic volcanic rocks determined using trace element analyses. Earht Planet. Sci. Lett., 19, 290–300.
Pearce J.A., Norry M.J., (1979). Petrogenetic Implications of Ti, Zr, Y and Nb Variations in Volanic Rocks. Contrib. Mineral. Petrol, 69, 33–47.
Tarney J., Sanders A.D., Mattey D.P. et al., (1981). Geochemical aspects of back-art spreading in the Scotia See and western Pacific. Phil. Trans. R. Soc., London, A300, 263–285.
Downloads
Published
Issue
Section
License
Copyright (c) 2024 Visnyk of Taras Shevchenko National University of Kyiv. Geology
This work is licensed under a Creative Commons Attribution 4.0 International License.
Read the policy here: https://geology.bulletin.knu.ua/licensing
