RESPONSE TO SLAB ROLL-BACK: REVEALING THE GEODYNAMIC HISTORY OF WESTERN TURKEY FROM THE BIGA PENINSULA TO THE MENDERES MASSIF (Invited Presentation)

Western Turkey and the Aegean region have global importance due to their role as the planet’s largest zone of active continental extension. The region is the type locality of a tectonic “switch”, where crustal dynamics changed over a short geological timescale from contraction to extension. Based on a number of geophysical, tectonic, and geochemical developments, extensional processes in western Turkey are dominated by the roll-back of the subducting African slab along the Hellenic arc in the Aegean Sea. We seek to understand how the process is recorded in the rock record via multiple geochemical recorders, including ages of intrusive igneous assemblages and the P-T-t history of its garnet-bearing metamorphic rocks. The idea that the temporally progressive extension from the northern portion of western Turkey to the south is recorded by a series of intrusive igneous rocks from the Biga Peninsula through the northern and central portions of the massif appears unsupported by zircon and monazite ages from a series of granites. For example, we find early to middle Miocene zircon grains in central Biga Peninsula granites (19.6±2.0 Ma, 15.7±3.3 Ma, 14.3±3.0Ma, U-Pb ages, ±1s) that overlap in age with zircon grains from northern Menderes Massif intrusions (17.2±0.8 Ma, 16.0±0.9 Ma, 15.7±0.6 Ma) and with monazite grains from central Menderes detachment exhumed granodiorites (15.0±2.80 Ma, 15.0±1.7 Ma, Th-Pb, ±1s). In addition, new garnet-based P-T modeling suggests pulses of shortening/burial and extension/exhumation may have occurred during the Eocene-Oligocene prior to large-scale extension that began in the Late Oligocene-Miocene. The results have implications for our understanding of how subduction roll-back is recorded in the rock record in general, the temporal relationship of the exhumation of the Menderes Massif to other Aegean core complexes, and the plate tectonic dynamics that led to the assembly of western Turkey.