The Generation of Eocene Mafic Dike Swarms During the Exhumation of a Core Complex, Biarjmand area, NE Iran

Abstract Several swarms of parallel E–W dikes cuts late Neoproterozoic- to early Paleozoic (540 Ma) basement in the Biarjmand area, NE Iran. The microgabbroic doleritic dike are several hundred meters long and 0.5 3 wide. U–Pb dating their zircon grains yields a crystallization age 46.0 ± 7.1 Ma for swarms. have SiO2 contents 46.0–49.3 wt%, Fe2O3 9.80–14.8 wt% with variable MgO (4.92–9.16 wt%), TiO2 (1.47–2.65 K2O (0.33–1.13 wt%). low high field strength elements (HFSEs), some similarities transitional mid-ocean ridge basalts (T-MORB) based on chemical composition. Positive ${\varepsilon}_{Nd}(t)$ values +5.2 +6.0 samples imply that basaltic magma was generated from depleted lithospheric mantle. After closure Sabzevar ocean obduction large mantle peridotite body over continental crust Cretaceous-Paleocene, gravitational instability central Iran/Eurasia plate collision zone triggered exhumation old coeval injection mafic magma. During exhumation, mylonitic deformation brittle-ductile structures affected metagranite host rocks. cut Cretaceous ophiolite, disparting ophiolite members probably occurred during Cenozoic. similar ages other Eocene magmatic rocks Urumiah (Urmia) Dokhtar arc (UDMA), western Iran, is consistent rapid extensional regime suture an earlier This process provided suitable setting basement, emplacement swarm, development shallow basins this area.