At the crossroads of the Lesser Caucasus and the Eastern Pontides: Late Cretaceous to early Eocene magmatic and geodynamic evolution of the Bolnisi district, Georgia

Article Article scientifique Article At the crossroads of the Lesser Caucasus and the Eastern Pontides: Late Cretaceous to early Eocene magmatic and geodynamic evolution of the Bolnisi district, Georgia eng 2020 author Moritz Robert 27897 author Popkhadze Nino author Haessig Marc 865855 author Golay Titouan 822177 author Lavoie Jonathan 807499 author Gugushvili Vladimer author Ulianov Alexey 735099 author Ovtcharova Maria 593060 author Grosjean Marion Jeanne 0000-0002-2108-7411 876822 author Chiaradia Massimo 0000-0003-4943-2480 110575 author Dumitrica Paulian 105872 10.1016/j.lithos.2020.105872 0024-4937 https://linkinghub.elsevier.com/retrieve/pii/S0024493720305077 The Bolnisi district is a distinct tectonic zone of the Lesser Caucasus, which is considered to represent the eastern extremity of the Turkish Eastern Pontides. Late Cretaceous, low-K, calc-alkaline to high-K rhyolite of the Mashavera and Gasandami Suites is the predominant rock type of the district, and is accompanied by subsidiary dacite, and rare high-alumina basalt and trachyandesite of the Tandzia Suite. The Mashavera and Gasandami rhyolite and dacite have yielded U-Pb LA-ICP-MS and TIMS zircon ages between 87.14 ± 0.16 and 81.64 ± 0.94 Ma, which are in line with the Coniacan-Santonian ages of radiolarian fauna of the Mashavera Suite. The felsic rocks of the Mashavera and Gasandami Suites were deposited during a ~6.6 m.y.-long silicic magmatic flare-up event, which together with the Tandzia Suite mafic rocks, documents Late Cretaceous bimodal magmatism in an extensional tectonic setting. Trace element data indicate that high Y-Zr, low- to high-silica rhyolite and dacite, and low Y-Zr high-silica rhyolite have been erupted, respectively, from coeval deep and shallow crustal reservoirs. The rocks of the bimodal magmatic event are overlain by high-K volcanic rocks of the Campanian Shorsholeti Suite, which have been erupted during slab roll-back and steepening, from magmas produced by deep melting of a metasomatised mantle. Eocene postcollisional felsic intrusions crosscut the Late Cretaceous rock. The Coniacian to early Campanian bimodal magmatism, and the subsequent high-K magmatism of the Bolnisi district are contemporaneous and share geochemical characteristics with the Late Cretaceous magmatism of the Eastern Pontides. It documents the existence of a Late Cretaceous regional silicic magmatic province, and subsequent high-K magmatism during slab steepening. This regional magmatic evolution coincided with the opening of the Black Sea and the Adjara-Trialeti basins. This evolution was coeval with the wanning stages of northern Neotethyan subduction, after a ~40 m.y.-long magmatic lull along the southern Eurasian convergent margin. Early Eocene adakite-like magmatism affected both the Bolnisi district and the Eastern Pontides, demonstrating a common postcollisional magmatic evolution. Northern Neotethys Lesser Caucasus Silicic magmatic flare-up Bimodal and high-K magmatism Eastern Pontides Dewey 550 Swiss National Science Foundation Contrasting Cretaceous-Tertiary gold and copper ore formation along the Tethyan arc (Serbia-Bulgaria-Greece-Georgia-Armenia) 121510 CH Projects Swiss National Science Foundation Episodic Mesozoic to Tertiary ore-forming events along the Lesser Caucasus and adjoining tectonic provinces 138130 CH Projects Swiss National Science Foundation Episodic Mesozoic to Tertiary ore-forming events in successive geodynamic settings in an accretionary orogenic belt: the case of the Tethys orogenic belt 155928 CH Projects Swiss National Science Foundation Metallogeny of the Lesser Caucasus (Georgia, Armenia and Azerbaijan) 128324 CH Programmes Swiss National Science Foundation SCOPES 118901 42 Département des sciences de la Terre 154 false 692 Mineral Resources and Geofluids Lithos 378-379 105872 11912ade-d66c-4afc-9af3-ab3647df2367 Article (Published version) Public BolnisiLateCretEarlyEocenemagmatismandevolution.pdf 9852065 application/pdf OA OTHER openAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre

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At the crossroads of the Lesser Caucasus and the Eastern Pontides: Late Cretaceous to early Eocene magmatic and geodynamic evolution of the Bolnisi district, Georgia	Lithos			2020	314	272

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