U-Pb dating and geodynamics of mafic bodies at the southern margin of Lake Urmia, an evidence of Cretaceous magmatism in northwest Iran

In the northwestern part of the Sanandaj-Sirjan zone, mafic intrusive bodies are aligned with the trend of the Zagros orogenic belt. In this part of the Iranian lithosphere, magmatic activity occurred during three main periods: Cretaceous, Eocene, and Miocene-Quaternary. In the first of two stages, the magmatic activity was associated with subduction-related magmatism at the active continental margin, whereas the last phase was characterized by calc-alkaline magmatism related to post-collision regime. The intrusive mafic bodies of Qobadlo, Chupankareh, and Qaraqoshun at the southern margin of Lake Urmia in the northern part of the Sanandaj-Sirjan zone intruded within the complex of Cretaceous shale, shale-sandstone, and siltstone. U-Pb dating on zircon performed on these bodies indicates an age of 99 Ma. The SiO2 content of these bodies ranges from 46.17 to 53.35%, Al2O3 13.1 to 18.49 % Fe2O3 3.11 to 5.8%, and their TiO2 content ranges from 1.9 to 4.0%. Positive anomalies of large ion lithophile elements and LREE compared with negative anomalies of elements such as Nb, P, Zr, and Ta (HFSE), the La/Nb, Ba/Nb ratios, and the REE pattern show a good correlation with the magmatic rocks of subduction zones.