Migrating magmatism in a continental arc: Geodynamics of the Eastern Mediterranean revisited

The eastern Pontide orogenic belt in Turkey offers a critical region to evaluate the geodynamic evolution of the eastern Mediterranean region during the late Mesozoic–Cenozoic. Here we synthesize results from our exhaustive database on the geochemical characteristics of adakitic magmatism from 137 bodies covering 7 domains in the southern zone of eastern Pontides. Together with new Pb–Sr–Nd results, we show that the adakitic magmatism in the eastern Pontide belt is clearly linked to slab window processes during ridge subduction, as against the earlier models that assumed partial melting of a delaminated or thickened lower continental crust following collision. The isotopic compositions display a complex pattern and suggest mixing of multiple source materials such as depleted mantle, enriched lithospheric mantle, and upper crust. We also confirm a southward polarity of subduction as against the previous models that assumed a northward subduction. We supplement our model with evidence for a northward propagation of the adakitic magmatism, spatial and temporal variations in arc magmatism, presence of south-dipping reverse faults and a synthesis of the available paleomagnetic data. Our studies also suggest that the Black-Sea is a remnant of the Tethyan ocean that was situated to the north of the arc during the late Mesozoic–Cenozoic as against the correlation to a late Mesozoic–Cenozoic back-arc basin related to a northward subduction of the Paleo- or Neo-tethyan oceanic lithosphere in alternate models.

Research highlights▶ This is the first comprehensive study of its kind on adakites and related rock from the eastern Pontide orogenic belt in Turkey covering 137 bodies in 7 domains and provides breakthrough results in understanding the geodynamic evolution of the eastern Mediterranean region during late Mesozoic–Cenozoic. ▶ Based on major, trace and REE geochemistry and Pb–Sr–Nd results, we demonstrate that the adakitic magmatism in eastern Pontidie belt is linked to slab window processes during ridge subduction, as against the earlier models that assumed partial melting of a delmainated or thickened lower continental crust following collision. We also propose a challenging geodynamic model on southward polarity of subduction as against the previous models that assumed a northward subduction. ▶ We supplement our model with evidence from a northward propagation of adakitic magmatism, spatial and temporal variations in arc magmatism, presence of south-dipping reverse faults and a synthesis of the available paleomagnetic data. ▶ Our studies also bring out a challenging new concept that the Black-Sea is a remnant of the Tethyan ocean that was situated to the north of the arc during late Mesozoic–Cenozoic as against correlation to a late Mesozoic–Cenozoic back-arc basin related to northward subduction of the Paleo- or Neo-tethyan oceanic lithosphere.