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

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...

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Bibliographic Details
Published in:Tectonics (Washington, D.C.) D.C.), 2020-03, Vol.39 (3), p.n/a
Main Authors: Vasey, Dylan A., Cowgill, Eric, Roeske, Sarah M., Niemi, Nathan A., Godoladze, Tea, Skhirtladze, Irakli, Gogoladze, Salome
Format: Article
Language:English
Subjects:
Accretion
Amphibolites
Apatite
Arabia‐Eurasia continental collision
basement evolution
Biotite
Carboniferous
Cenozoic
Continents
crustal exhumation
Crystalline rocks
Deformation
Earth crust
fold‐thrust belt
Geochronology
Geochronometry
Geological time
Greater Caucasus Mountains
Magma
Mesozoic
Metamorphism
Mountains
Muscovite
Paleozoic
Rifting
Rock
Sedimentary facies
Shear zone
shear zone formation
Uplift
Zircon
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Summary: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 40Ar/39Ar geochronology, and 40Ar/39Ar 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. 40Ar/39Ar 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 40Ar/39Ar biotite age with release spectra indicating partial resetting and Cenozoic (
ISSN:0278-7407
1944-9194
DOI:10.1029/2019TC005828