INGREDIENTS OF RAPID EXHUMATION AND DETACHMENT FAULTING: A CASE STUDY FROM MENDERES CORE COMPLEX, WESTERN TURKEY

The Menderes Core Complex is a unique example of rapidly-exhumed mid-to-lower crustal rock bodies in the footwall blocks of low-angle detachment faults in highly-extending terrains similar to Cordillerian core complexes of western U.S. Paleozoic crsytalline footwall block intruded by syn-extensional calk-alkaline intrusions of Early Miocene age. Based on the initial crystallization and cooling ages of the syn-extensional granitoid intrusions and our thermochronological findings, the Central sub-massif bounded by the Alasehir detachment fault underwent accelerated uplift and faster exhumation in the latest Cenozoic than the Northern and Southern sub-massifs. The asthenospheric upwelling and the related Na-alkaline, OIB-like Kula volcanism was responsible for latest doming and rapid extension of the Central sub-massif. The Menderes Massif has experienced a diachronous uplift and cooling history during its extensional tectonic evolution in the late Cenozoic. Lithospheric thinning and asthenispheric melting resulted in significant thermal weakening of the young post-orogenic crust produced higher geothermal gradients and played a significant role in core complex formation. The occurrence of these basaltic lavas points to the presence of the shallow asthenosphere at the base of the thinned lithosphere, whereas their alignment in NE-SW direction coincide with NE-striking, rotational scissor faults in the region. As one of the major fault types, lithospheric-scale, high-angle rotational faults forming as extension-parallel structures in most of highly-extending terrains play significant role during the exhumation and crustal denudation processes. Diachronous uplift and exhumation of the Menderes core complex appear to be controlled by asthenospheric upwelling and convective asthenispheric mantle below tectonically rapid-extending regions. This tectonic model indicates that major ingredients of rapid exhumation and formation of core complexes and their detachment faults is significant thermal and mechanic weakening of the young post-orogenic crustal blocks.