An international team led by Istanbul Technical University has identified a previously unknown volcanic system in northwestern Iran that formed during the Late Cretaceous period, approximately 101 to 97 million years ago. Named the Azerbaijan Continental Magmatic Arc, the system formed in what is now part of the Arabia-Eurasia collision zone.
The researchers examined volcanic and plutonic rocks from multiple locations across northwestern Iran, focusing on formations along the Siah Cheshmeh-Khoy-Misho-Tabriz Fault. They used zircon U-Pb geochronology to establish ages, Hf isotope analyses to investigate material sources, and whole-rock geochemistry to examine chemical composition. The results revealed signatures consistent with continental arc magmatism, a process that occurs when one tectonic plate sinks beneath another and generates magma rising through the overlying continental crust.
Dr. Ali Mohammadi, the study's corresponding author at Istanbul Technical University, stated: "This study shows that the magmatic history of northwestern Iran is more complex than previously recognized. By integrating geochronological, isotopic, and geochemical evidence, we identified a Late Cretaceous continental arc that was subsequently obscured by later tectonic processes."
The research, published in Geoscience Frontiers, involved scientists from the Institute of Tibetan Plateau Research and Xinjiang Institute of Ecology and Geography at the Chinese Academy of Sciences, ETH Zurich, Karadeniz Technical University in Turkey, and Damghan University in Iran.
Tectonic deformation, erosion, burial beneath sedimentary basins, and younger volcanic activity during the Eocene period had obscured much evidence of the arc's existence. The discovery adds to previous reconstructions of Iran's magmatic activity, which centered on two major features: the Sananda-Sirjan Magmatic Arc and the Urumieh-Dokhtar Magmatic Arc. Researchers suggest the Siah Cheshmeh-Khoy-Misho-Tabriz Fault may mark a major tectonic boundary connected to changes in the ancient Neo-Tethys Ocean system, potentially including slab rollback and volcanic arc migration.