Crustal Lg Attenuation Beneath the Iranian Plateau: Implications for Cenozoic Magmatism Related to Slab Subduction, Slab Break-Off, and Mantle Flow

Cenozoic magmatism is present across the Iranian Plateau but, despite playing an important role in the geodynamic evolution of the young plateau, remains poorly understood. In this study, the crustal thermal structure beneath the Iranian Plateau is investigated by high-resolution Lg-wave attenuation tomography using a newly compiled data set, which consists of records from three recent temporary seismic arrays (for a total of 197 stations) and previous regional networks. Strong Lg attenuation is mainly observed beneath the Zagros orogenic belt, Urumieh-Dokhtar magmatic arc (UDMA), Makran magmatic arc, Lut magmatic zone, and Alborz reararc magmatic belt, which covers not only tectonic boundary belts but also the active internal zones of the Iranian Plateau. Combining deep seismological observations and geochemical data, the strong crustal attenuation characteristics beneath the northwestern and southeastern UDMA suggest that Miocene–Quaternary magmatism was activated by slab detachment-induced upwelling after the cessation of oceanic subduction. Western Makran is characterized by strong Lg attenuation with a NE trend. The age of the Paleogene–Quaternary Makran volcanism decreases toward the NE and is likely related to the change in subduction dip. Diffuse magmatism and strong crustal attenuation are present in the northern Lut Block rather than the entire Lut–Afghan collision zone, which is likely associated with the accumulation of mantle magmas driven by the potential northward asthenospheric flow. In northern Iran, a strong attenuation anomaly spans the entire E‒W Alborz magma belt, suggesting that partial crustal melting and mantle thermal sources may exist in this region.