U-Pb zircon chronological constraints for three stages of synorogenic plutonic magmatism of the Greater Caucasus Svaneti segment, Georgia

The Greater Caucasus fold-thrust belt is the northernmost expression of the Caucasus orogen and is accreted to the southern margin of the Precambrian Scythian platform. This paper presents new data of zircon LA-ICP-MS U-Pb geochronology of the Svaneti segment plutons of this orogen. The data indicate three major stages of plutonic magmatic activity that correspond to major orogenic events in the region: 1- Ordovician (Caledonian orogenesis), 2-Late Carboniferous (Variscan orogenesis) and 3Middle Jurassic (Cimmerian orogenesis). In the Early Ordovician (ca. 480 Ma), the granitoid protoliths crystallsized, wich later, during the Variscan orogeny, deformed and metamorphosed (biotite orthogneisses). At the second stage, during Late Variscan orogenesis, Upper Carboniferous granodiorite-granite plutons (318-312 Ma) were emplaced within Caledonian migmatised gneissic infrastructure of the Pass and Elbrus subzones. At the third stage, the Middle Jurassic monzo-syenite plutonic activity is preserved in the Paleozoic-Triassic Dizi series. The ages of the Middle Jurassic plutons gradually decreases from north to south (177, 168, and 164 Ma), which indicates the time and direction of the Dizi basin closure. Combining of the spatial analysis with chronological constraints provided by these plutons leads to the conclusion that the northern margin of Neotethys subduction, were proceeding from south to north.