The far-field interplay between Neo-Tethys slab break-off and Eocene granitic magmatism in the Sanandaj-Sirjan Zone, Iran

This study investigates the Late Eocene Davarijan granite (sensu stricto) in the northern Sanandaj-Sirjan Zone through integrated whole-rock geochemistry, Sr-Nd isotopes, and zircon U-Pb and white mica ⁴⁰Ar/³⁹Ar geochronology. The new data constrains the timing of crystallization, cooling, and magma sources, providing crucial insights into crustal evolution and tectonic processes in the Azna-Dorud region of the Zagros orogenic system. Zircon U-Pb ages (34.6 ±1.9 Ma; 35.45 ±0.42 Ma) and white-mica ⁴⁰Ar/³⁹Ar cooling ages (33.48 ±0.16 Ma) indicate rapid post-emplacement cooling (~10.5 ℃/Myr) during the Late Eocene and earliest Oligocene. The granites display high-K alkaline, slightly peraluminous composition and geochemical features typical of A-type granites (specifically of A₂; by high Y/Nb). ⁸⁷Sr/⁸⁶Sri (0.706741-0.707001), ε_Nd(t) (-0.99 to +0.46), and T_DM2 ages (0.85-1.1 Ga), together with the presence of ~ 57 Ma inherited zircons, suggest partial melting of an isotopically rejuvenate ancient felsic crustal source (likely a tonalite) with limited mantle input. These findings strongly support a post-collisional tectonic setting linked to the terminal stage of the Neo-Tethys Ocean subduction and provide valuable constraints on the geodynamic evolution of the Arabia-Eurasia collision zone.