EXAMINING EXHUMATION OF HIGH-PRESSURE ROCKS IN AN AEGEAN METAMORPHIC CORE COMPLEX: COMBINING STRUCTURAL ANALYSIS WITH GEO- AND THERMOCHRONOLOGY

Tectonic processes that exhume high-pressure metamorphic rocks from great depths in syn-convergent back-arc settings are not well understood. Miocene syn-convergent back-arc extension in the Attic-Cycladic Crystalline Belt of the Aegean Sea has been instrumental in the development of a conceptual understanding of detachment faulting in back-arc settings and of the mechanisms that influence the exhumation of high-pressure rocks in metamorphic core complexes. Based on Aegean observations, two contrasting exhumation mechanisms have been proposed: subduction induced extrusion-wedge underplating and low-angle normal fault extension. The islands of Andros, Tinos, and Evvia in the NW Cyclades are ideal settings for investigating how low-angle normal faults assist or influence high-pressure rock exhumation. Tinos is a Cordilleran-style metamorphic core complex consisting of the classic Cycladic Blueschist Unit, high-pressure rocks, in the footwall exhumed along several low-angle normal faults in the North Cycladic Detachment System. On Evvia, the Cycladic Blueschist Unit occurs in contractional-style nappe stacks exhumed by an extrusion wedge during subduction, subsequently modified and exhumed by detachment faulting. A low-angle normal fault on the island of Andros 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 high-resolution geochronological, thermochronological, and structural study to examine the spatiotemporal transition of kinematic and thermal regimes in the area from Tinos to Evvia. This study presents new detrital and metamorphic zircon U-Pb and (U-Th)/He data from various structural levels exposed on Andros and Tinos. These geo- and thermochronometric data combined with structural observations appear to contradict existing models for the structural evolution of the study area, indicating multiple phases of detachment faulting. Additionally, we examine the relationship of upper and lower plate metamorphic rocks with the tectonically anomalous Makrotantalon Unit on Andros. These new data aim to elucidate the magnitude, temporal, and spatial variability of these two tectonic processes in exhuming the Aegean back arc high-pressure rocks.