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 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 ...