Geodynamic Development of Eurasian Active Margin During

Journal of Environmental Science and Engineering B9 (2020) 248-260 D doi:10.17265/2162-5263/2020.06.003 DAVID PUBLISHING Geodynamic Development of Eurasian Active Margin during Closing of Thetys Ocean, Depending on the Scale of Mantle-Crustal Sources Influence at Pre- and Post-collision Settings, Controlled by Geological and Geochemical Indicators Vladimir I. Gugushvili Department of Metallogeny, Al. Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Jikia 16, Tbilisi 0186, Georgia Abstract: Phanerozoic geodynamic evolution development of Tethys Ocean, its collision and closing, revealed at the Eurasian active margin in pre- and post-collision stages during convergence of Afro-Arabian and Eurasian continents. Subduction of oceanic slab under continental margin revealed in steady state subduction and steepening of subducting slab provoked the incursion of mantle diapir. The steady state subduction is related with island arc setting whereas steepening provoked incursion of mantle diaper interarc-backarc and minor ocean settings. They are controlled by geological indicators—volcagenic, petrochemical, geochemical, tectonic and metallogenic. Each of them is determined by scale of mantle-crustal influence, controlled by intensity and level of mantle diapir incursion in the crust rising from interarc-backarc to minor oceanic setting. The island arc setting is characterized by blocking, which as others by extension of rifting (interarc-backarc) caused spreading out from zone of volcanic activity and mineralization sialic crusts, whereas minor ocean setting caused by spreading out from zone of volcanic activity and mineralization sialic and basaltic crusts. So mantle crustal influence rising from island arc to minor ocean settings controlled type of volcanism and mineralization in pre-collision development. At the closing of ocean occurred the precollision setting which is transferred in post-collision revealed in orogenesis. It is divided in two stages. The first initial stage occurred in penetration hot fluids from the mantle in sialic crust smelted from in granitoid melt and leached the gold and trace melts Sb, W, Mg and Hg from sialic crust. The latter are geochemical indicators of post-collision setting. The second final stage revealed in shoshonite-basalt volcanism activity occurred with penetrated mantle material into deep volcanic chambers and characterized with increasing of mantle influence than initial stage of post-collision activity. Key words: Pre- and post-collision settings, crustal-mantle sources, geological indicators. 1. Introduction modern plate tectonic with subduction and spreading of oceanic crust and forming ocean and continents. At the Precambrian after cratonization the Earth crust The collision and closing ocean revealed in forming of is divided by sialic, basaltic and rigid upper mantle continental active margin, as evolution of Tethys and Au and base metals—Pb, Zn and Cu which were ocean at Eurasian margin at pre- and post-collision redistributed within them. Au and Pb contained in stages. Our studied region occurred in the Western sialic, Zn—in basaltic, whereas Cu is rested in mantle segment of Eurasian active margin, within Iran, [1]. In Phanerozoic the plume tectonic is alternated by Caucasus, Turkey and Balcan-Carpaths (Fig. 1). We tried to show in geodynamic development exemplified Corresponding author: Vladimir I. Gugushvili, Ph.D., professor, research fields: volcanology, matallogeny, geodynamic. of this (Fig. 1) region based of plate-tectonic data. Geodynamic Development of Eurasian Active Margin during Closing of Thetys Ocean, 249 Depending on the Scale of Mantle-Crustal Sources Influence at Pre- and Post-collision Settings, Controlled by Geological and Geochemical Indicators Fig. 1 Map of the Western Tethysides (Stampfli, et al. [2]) . minor ocean, backarc, marginal Volcanic Massive Sulfide mineralization; subduction related with porphyry, epithermal and kuroko type mineralization; postcollision orogenic and intrusive related lode and porphyry mineralization. 2. Material dacite-rhyolite volcanic activity, where Au-Pb-Zn-Cu porphyry and Kuroko type stratiform mineralization 2.1 Pre-collision Development are related to calc-alkaline volcanic activity [4]. The In the Caucasus the plate-tectonic study was ore forming process here is controlled by blocking beginning in 1974 [3]. Now the region is studied in related to granodiorite intrusive stocks tumiscenced detail. sea bottom and elevated the islands (Uplifted blocks). The precollision stage of geodynamic development On the islands ignibrite volcanic activity was was revealed by steady state subduction and terminated by cauldron-subsidence (subside blocking). steepening of subducting slab. The initial activity of The blocking at Madneuli, so at Tsiteli-Sopeli steady state subduction began by regional deposits both are synvolcanic. The mineralization as metamorphism and granitization at fluid temperature porphyry, so in Kuroko type deposits’ is related to 350-750 °C. The arising temperature up to granodiorite stocks and volcanic chambers and 1,100-1,200 °C smelting from subducting slab sources of ignimbrite explosion terminated by andesitic magma challenged calc-alkaline volcanic cauldron subsidence [4]. activity of island arc setting. So, volcanogenic indicator here is calc-alkaline The Bolnisi Ore District (Fig. 2) is a good example volcanics related to steady state subduction, of island arc setting, where at the Madneuli and Tsiteli metallogenic—Au, Pb, Zn, Cu mineralization leaching Sopeli gold-base metals porphyry deposits occurred in from sialic, basaltic crust and mantle (the slab was 250 Geodynamic Development of Eurasian Active Margin during Closing of Thetys Ocean, Depending on the Scale of Mantle-Crustal Sources Influence at Pre- and Post-collision Settings, Controlled by Geological and Geochemical Indicators Fig. 2 Geological map of Bolnisi ore district. I Madneuli cluster, II Bectaqari cluster. deepening inmantle). The tectonic indicator is represented by its two stages. The initial-lower blocking the geochemical cryteria are ratias of St and Campanian stage consists of trachyodacitic volcanic Pb isotopes in the ore bearing rock 87Sr/86Sr = suite intensively alternated by gold-bearing k-fieldspar 0.705-0.715, 208Pb/204Pb = 39 [4]. The similar metasomatites and is not subjected by rifting. The geological indicators were determined in the Pontides subalkal volcanism and alkali alteration must be (Turkey) (Fig. 3), Panaguirishte ore district (Bulgaria) related to initial stage of alkali alteration and must be and Timock region (Serbia), related to island related with initial stage of back arc setting, where calc-alkaline volcanism, porphyry and Kuroko type rifting and spreading out sialic crust from zone of mineralization and synvolcanic tectonics [5] (Fig. 4). volcanic activity was not determined. It is the reason In the Bolnisi ore district neighboring to of low sulfidation gold mineralization and participation Turonian-Santonian clusters of Madneuli occurred of Pb in porphyry ores. Ascending succession of the Campanian Beqtakari cluster. Madneuli and Beqtakari goldbearing Lower Campanian rocks was alternated clusters are divided by regional postvocanic foult (Fig. by Upper Campanian Shorsholety suite of shoshonites 2). The Beqtakari belongs to backarc setting and is alkali olivine basalts and tholeiites [4, 6] (Fig. 5). Geodynamic Development of Eurasian Active Margin during Closing of Thetys Ocean, 251 Depending on the Scale of Mantle-Crustal Sources Influence at Pre- and Post-collision Settings, Controlled by Geological and Geochemical Indicators Fig. 3 Geotectonic scheme of Turkey with metallogeny of sulfide deposits after Engin (Engin, [6]. Deposits: 1: Murgul, 2: Madenkoy, 3: Lahanos, 4: Guzelayla, 5: Derekoy (Kircaleli), 6: Cutlalar, 7: Akdagmeni, 8: Bakibaba (Küre), 9: Ashikoy (Küre), 10: Arapchan, 11: Balya, 12: Demirbocu, 13: Altinoluk, 14: Kulakchitligi, 15: Bozkur, 16: Aladag, 17: Hyuilu, 18: Derekoy (Kaizery), 19: Keban (Elazig), 20: Maden (Elazig), 21: Madenkoy (Siirt). The diabase apophyses of its volcanic chamber that The first stage of rifting is related to consist porphyry mineralization coincided with shoshonite-trachyandesite volcanism. It is in epidote-tcoizite propylitization [4]. Therefore, Achara-Thrialetyi zone at ascending sucsetion Shorsholety suite belongs to second stage of backarc overlined the tholeiite-olivine basalt series and setting. The similar situation (Fig. 4) is known in the belongs to transitional stage of interarc-backarc Panaguirishte ore district, where high sulfidation settings [3]. Its initial stage similarly as island arc Au-Pb-Zn-Cu Chelpech goldbearing deposit is divided setting is characterized by booking tectonics by blocking from Zn-Cu Tsar Asen and Vlaikov Vruh ignimbrite activity, cauldron subsidence and subalkali porphyry deposits [5]. trachyodacite volcanic activity without rifting. The better example of back arc rifting and olivine The minor ocean setting in the studied region is the basalt-tholeiite volcanism and stratiform Volcanic Paleozoic Küre complex (Fig. 3) which consists of Massive Sulfide Cu-Zn mineralization is Hudes group ophiolites type volcanics and dunite-peridotite intrusions. of deposits (Hudes, Urup, Daud) of for Range of The complex contains serpentinized peridotites cumulate North Caucasus [7, 8]. Its genesis may be explained gabbro, pillow lavas intercalated with massive lava by spreading out sialic crust by rifting from zone of

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