EXHUMATION OF HIGH-PRESSURE ROCKS IN THE AEGEAN BACK ARC: TUG-OF-WAR OF TITANS ON ANDROS AND TINOS ISLANDS

Tectonic processes that exhume high-pressure metamorphic rocks from great depths in syn-convergent back-arc settings are not well known. Miocene syn-convergent back-arc extension seen in the Attic-Cycladic Crystalline Belt of the Aegean Sea is used as a proxy for understanding detachments and is a key area for observing how contractional and extensional mechanisms influence high-pressure metamorphic core complex exhumation. Previous workers propose two different titans of exhumation mechanisms: subduction induced extrusion-wedge underplating versus low-angle normal fault extension. Andros, Tinos, and Evia Islands in the Attic-Cycladic Crystalline Belt of the Aegean Sea are ideal for addressing how critical low-angle normal faults are in high-pressure rock exhumation. Tinos Island is a Cordilleran-style metamorphic core complex consisting of classic Cycladic Blueschist Unit high-pressure rocks exhumed along several low-angle normal faults in the North Cycladic Detachment System. Conversely, Evia displays the Cycladic Blueschist Unit in nappe stacks exhumed by an extrusion wedge during thrusting. Understudied Andros Island’s low-angle normal fault has been considered part of the North Cycladic Detachment System, but the temporal evolution of thrusting and extension has not yet been explored. Andros is ideally positioned for a detailed geochronological, thermochronological, and structural study to examine the spatiotemporal transition of kinematic and thermal regimes between Tinos and Evia. New U-Pb-He and (U-Th)/He geo-/thermochronometry from Andros and Tinos help elucidate the magnitude, temporal, and spatial variability of these two fundamental titans of tectonic processes in exhuming the Aegean back arc high-pressure rocks.