A LOW-TEMPERATURE THERMOCHRONOMETRIC PERSPECTIVE ON THE SUBDUCTION-TO-COLLISION TRANSITION IN THE CAUCASUS REGION (Invited Presentation)

The Caucasus orogen developed in response to the Arabia-Eurasia collision and spatially records various stages in the progressive closure of a series Mesozoic Peri-Tethyan basins (Black and Caspian seas) and initiation of collision between a Mesozoic-Cenozoic island arc terrane to the south (Lesser Caucasus and Eastern Pontides) with the Proterozoic-Paleozoic continental margin of Eurasia to the north. The relatively narrow width of these back-arc basins (<500 km?), and the recency of their consumption (< 5 Mya?) provides insight into plate tectonic process that are commonly dispersed in time and space, including the localization of deformation along a continental-oceanic boundary in response to far-field plate stress (eastern Pontides), the development of an accretionary prism above a subducting oceanic plate (Azerbaijan) and the nascent development of a continent-continent collision zone (Georgia). The subaerial exposure of much of this region and the distinct zircon crystallization ages associated with the Eurasian continental margin and impinging island arc provide an apparently unrivaled natural laboratory for understanding the tectonic, structural, and sedimentologic evolution of a convergent margin. Here we compile low-temperature thermochronometric (primarily apatite and zircon (U-Th)/He and apatite fission-track) data from the Greater Caucasus, Lesser Caucasus and eastern Pontides with detrital zircon U-Pb data from Cenozoic strata in the Caucasus region. Placing these data in tectonic and structural context derived from geologic field work allows us to elucidate the evolution of structural style, variations in the magnitude of exhumation, and changes in provenance that accompany the transitions from subduction initiation to subduction accretion to continental collision . Determining the partitioning of deformation between upper and lower plates of the orogen, the localization of deformation with respect to colliding continental blocks and the closing basin, and shifts in provenance and structural vergence with progressive convergence in the Caucasus yield general insights for unravelling the tectonic histories of collisional orogens.