Petrology, mineral chemistry and Sr-Nd-Pb isotopic compositions of granitoids in the central Menderes metamorphic core complex: Constraints on the evolution of Aegean lithosphere slab

Plutonic associations in the central Menderes metamorphic core complex are suitable rocks in order to understand the magma forming processes in extended terrains. Syn-extensional Salihli and Turgutlu granitoids have granodioritic composition and contain monzonitic and monzodioritic microgranular enclaves. They are transitional metaluminous/peraluminous and high-K calc-alkaline in character and are located on 1- and S-type transition. Salihli and Turgutlu granodiorites are geochemically similar to each other while their microgranular enclave chemistry is in contrast with low SiO2 and high Mg # values. Mineral chemistry data from granodiorites and mafic microgranular enclaves confirm their shallow emplacement at about 7 km. Geochemical modelling suggests that syn-extensional granitoids were derived from the mixing of mantle and lower crustal components, which were finally modified by a significant amount of upper crustal contamination and fractional crystallization processes at shallow crustal levels. Early-Middle Miocene syn-extensional granitoids across the Aegean region form a magmatic belt associated with roll-back of the Aegean lithosphere slab. Roll-back induced magmatism together with ductile deformation in western Turkey ceased after cooling of the Salihli granodiorites at 12.2 Ma. But core-complex related magmatism was continuous in the Cycladic metamorphic core complex during Late Miocene and was followed by an active arc volcanism in the southern Aegean. Such abrupt change from ductile to brittle mode of extension in western Turkey can be explained by opening of a slab window on the Aegean lithosphere slab, which would lead to upwelling of fertile subslab asthenospheric mantle, forming transitional and finally OIB-type basalts. (C) 2013 Elsevier B.V. All rights reserved