Late Jurassic Paleotethyan oceanic slab break-off revealed by Sr-Nd-Hf isotopes of Na-rich adakitic granites from northwestern Turkey

•Late Jurassic adakitic magmatism was discovered in the western Sakarya Zone.•The adakitic rocks originated from the Paleotethyan oceanic slab.•Asthenospheric upwelling due to slab break-off caused melting of oceanic slab.•All the data suggest that they were formed in a post-collisional setting.•Closure of Paleotethys triggered opening of Neotethys in a back arc to the south.