Variscan orogeny in the Black Sea region

Okay, Aral I.; Topuz, Gültekın

doi:10.1007/s00531-016-1395-z

Cited by 108 publications

(67 citation statements)

References 98 publications

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“…The crystalline massifs record magmatic events at ~540 Ma and ~480 Ma, as well as low‐pressure/temperature metamorphism and magmatism at ~340‐310 Ma (Figure b; Gamkrelidze et al, ; Mayringer et al, ; Rolland et al, , Rolland et al, ). Given that similarly aged magmatic rocks have been reported in the Greater Caucasus (Figure a; Somin, ; Shengelia et al, ), these massifs have been speculated to share a Paleozoic tectonic history with the Greater Caucasus crystalline rocks north of the MCT (Mayringer et al, ; Okay & Topuz, ), but this correlation is not universally accepted (e.g., Rolland et al, ).…”

Section: Tectonic Settingmentioning

confidence: 99%

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

et al. 2020

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Along the northern margin of the Arabia-Eurasia collision zone in the western Greater Caucasus, the Main Caucasus Thrust (MCT) juxtaposes Paleozoic crystalline basement to the north against Mesozoic metasedimentary and volcaniclastic rocks to the south. The MCT is commonly assumed to be the trace of an active plate-boundary scale structure that accommodates Arabia-Eurasia convergence, but field data supporting this interpretation are equivocal. Here we investigate the deformation history of the rocks juxtaposed across the MCT in Georgia using field observations, microstructural analysis, U-Pb and 40 Ar/ 39 Ar geochronology, and 40 Ar/ 39 Ar and (U-Th)/He thermochronology. Zircon U-Pb analyses show that Greater Caucasus crystalline rocks formed in the Early Paleozoic on the margin of Gondwana. Low-pressure/temperature amphibolite-facies metamorphism of these metasedimentary rocks and associated plutonism likely took place during Carboniferous accretion onto the Laurussian margin, as indicated by igneous and metamorphic zircon U-Pb ages of~330-310 Ma. 40 Ar/ 39 Ar ages of~190-135 Ma from muscovite in a greenschist-facies shear zone indicate that the MCT likely developed during Mesozoic inversion and/or rifting of the Caucasus Basin. A Mesozoic 40 Ar/ 39 Ar biotite age with release spectra indicating partial resetting and Cenozoic (<40 Ma) apatite and zircon (U-Th)/He ages imply at least~5-8 km of Greater Caucasus basement exhumation since~10 Ma in response to Arabia-Eurasia collision. Cenozoic reactivation of the MCT may have accommodated a fraction of this exhumation. However, Cenozoic zircon (U-Th)/He ages in both the hanging wall and footwall of the MCT require partitioning a substantial component of this deformation onto structures to the south. Plain Language Summary Collisions between continents cause deformation of the Earth's crustand the uplift of large mountain ranges like the Himalayas. Large faults often form to accommodate this deformation and may help bring rocks once buried at great depths up to the surface of the Earth. The Greater Caucasus Mountains form the northernmost part of a zone of deformation due to the ongoing collision between the Arabian and Eurasian continents. The Main Caucasus Thrust (MCT) is a fault juxtaposing old igneous and metamorphic (crystalline) rocks against younger rocks that has often been assumed to be a major means of accommodating Arabia-Eurasia collision. This study examines the history of rocks along the MCT with a combination of field work, study of microscopic deformation in rocks, and dating of rock formation and cooling. The crystalline rocks were added to the margins of present-day Eurasia about 330-310 million years ago, and the MCT first formed about 190-135 million years ago. The MCT is likely at most one of many structures accommodating present-day Arabia-Eurasia collision.

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Section: Tectonic Settingmentioning

confidence: 99%

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

et al. 2020

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“…In the NE Mediterranean, the Istanbul‐Zonguldak and Sakarya terranes are both intruded by Ordovician‐Silurian (460–430‐Ma) granitoids (Okay et al, ; Özmen & Reischmann, ). Carboniferous flysch in the Istanbul Zone contains zircons and rutiles of early Carboniferous age, suggesting that the Istanbul and Sakarya zones were juxtaposed during Early Carboniferous, that is, prior the Variscan orogeny in this region (Okay & Topuz, ). Moreover, in the Serbo‐Macedonian Massif, a small continental inlier called Pirgadikia (Himmerkus et al, ; Meinhold et al, ; Figure ) is attached to the Ordovician‐Devonian basement of the Vertiskos unit.…”

Section: Phases Of Accretion Of Peri‐gondwanan Terranes To Laurussiamentioning

confidence: 99%

New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

2018

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Between the eastern Mediterranean basin in the South and the East European (Baltica) Craton to the north, we distinguish two fundamental pre‐Variscan geological domains: an Internal domain, which hosts Ordovician‐Devonian (450–400 Ma) igneous rocks and detrital zircon populations, and an External domain, which contains no 450‐ to 400‐Ma zircon ages. From the Balkan Peninsula to the Turkish plate, the aforementioned Internal domain includes the Serbo‐Macedonian Massif, the Istanbul and Sakarya terranes, whereas the External domain, holding a more distal position relative to Baltica, includes the Pelagonian terrane and the External Hellenides. The two domains are interpreted as two consecutive (i.e., Caledonian and Variscan) Paleozoic accretionary belts, attached to the southern margin of Baltica. The Cycladic and Pelagonian terranes are currently juxtaposed along strike of the central Hellenides in Northern Greece. The Cycladic Massif is a Cadomian‐type terrane, while the Pelagonian displays an Avalonian‐type affinity. Despite its Avalonian affinity, the Pelagonian lacks Ordovician‐Devonian (450–400‐Ma) zircon ages. In contrast, detrital zircon grains of such ages are abundant in the Cycladic Massif. In this study, the Ordovician‐Devonian detrital zircon population is recognized also in pre‐Variscan (>310‐Ma) Cycladic Basement from Ios and Naxos Islands, affiliating the Cycladic Massif with the Internal (Caledonian) domain. This indicates that the Caledonian accretion incorporated some Cadomian‐type terranes. It also suggests that the protolith of the Cycladic blueschists was deposited within the Internal domain, that is, northeast of the Pelagonian terrane. This recognition helps to reconstruct the Paleozoic and Mesozoic paleogeography of the peri‐Gondwanan terranes.

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“…In the far south part of the orogenic belt, the same time span is represented by Alaskan‐type mafic‐ultramafic intrusions whose source is interpreted to be subcontinental lithospheric mantle that was metasomatized during the subduction of Paleotethyan oceanic lithosphere (Eyuboglu et al, ; Eyuboglu, Dudas, Santosh, Xiao, et al, ). Late Paleozoic granitoids are also widespread in the central and western Pontides, with ages clustered between 320 and 250 Ma (e.g., Gücer et al, ; Nzegge et al, ; Okay et al, ; Okay & Topuz, ; Şahin et al, ; Sunal et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Tectonics 320 and 250 Ma (e.g., Gücer et al, 2016;Nzegge et al, 2006;Okay & Topuz, 2017;Şahin et al, 2012;Sunal et al, 2006).…”

Section: 1029/2017tc004837mentioning

confidence: 99%

Petrology, Geochronology and Tectonic Setting of Early Triassic Alkaline Metagabbros From the Eastern Pontide Orogenic Belt (NE Turkey): Implications for the Geodynamic Evolution of Gondwana's Early Mesozoic Northern Margin

et al. 2018

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The Triassic geodynamic evolution of the Pontides Belt, which geographically corresponds to northern Anatolia, is still a matter of debate. We present and interpret geological, petrographical, geochemical, and geochronological data from small, discordant, metagabbroic rocks exposed in the Tokat Massif. Field and petrographic characteristics distinguish four subgroups: (i) medium‐grained, slightly lineated, clinopyroxene‐rich metagabbros; (ii) fine‐grained, nonlineated, clinopyroxene‐rich metagabbros; (iii) medium‐grained, nonlineated, brown amphibole‐rich metagabbros; and (iv) medium‐grained, slightly lineated, brown and blue amphibole‐rich metagabbros. Magmatic kaersutites give 39Ar/40Ar plateau ages of 244.6 ± 0.5 and 243.16 ± 0.92 Ma and overlap the U‐Pb age of titanite from a clinopyroxene‐rich sample. Inherited zircons (~460, ~880, and ~2600 Ma) in fine‐grained clinopyroxene‐rich metagabbros indicate interaction with a range of crustal rocks during the intrusion. The blue amphiboles are magnesioriebeckites that formed during metamorphism or late‐stage crystallization. Geochemical data, including whole rock major and trace element concentrations, and Sr‐Nd‐Pb isotope compositions reveal that both clinopyroxene‐ and amphibole‐rich metagabbros are alkaline in composition but derived from distinct mantle sources. They are compositionally distinct from mafic igneous rocks in the contemporaneous Permo‐Triassic Karakaya Complex that is well exposed in the western part of the Pontides Belt. Considering all data, we suggest that the Pontides Belt was shaped above a south dipping subduction zone during Permo‐Triassic and the alkaline gabbros that were emplaced into crustal rocks during Early Triassic back‐arc rifting of the northern margin of Gondwana.

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Variscan orogeny in the Black Sea region

Cited by 108 publications

References 98 publications

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

New Detrital Zircon Geochronology From the Cycladic Basement (Greece): Implications for the Paleozoic Accretion of Peri‐Gondwanan Terranes to Laurussia

Petrology, Geochronology and Tectonic Setting of Early Triassic Alkaline Metagabbros From the Eastern Pontide Orogenic Belt (NE Turkey): Implications for the Geodynamic Evolution of Gondwana's Early Mesozoic Northern Margin

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