An international research team led by Istanbul Technical University has documented the existence of a previously unrecognized volcanic system in northwestern Iran that formed during the Late Cretaceous period. The discovery, published in Geoscience Frontiers, identifies what researchers have named the Azerbaijan Continental Magmatic Arc, which was active from approximately 101 to 97 million years ago when the ancient Neo-Tethys Ocean was undergoing significant geological transformation.
The volcanic system had remained largely hidden from the geological record due to multiple obscuring factors over millions of years. Tectonic deformation, erosion, burial beneath sedimentary basins, and a subsequent volcanic episode during the Eocene period all contributed to concealing evidence of the system’s existence. To reconstruct this overlooked geological chapter, the research team examined volcanic and plutonic rock samples collected from multiple locations across northwestern Iran, with particular focus on formations along the Siah Cheshmeh-Khoy-Misho-Tabriz Fault.
Researchers employed advanced analytical techniques to determine when the rocks formed and identify their source materials. These methods included zircon U-Pb geochronology for age determination, Hf isotope analyses to investigate material origins, and whole-rock geochemistry to examine chemical composition. The resulting data revealed signatures consistent with continental arc magmatism, a geological process occurring when one tectonic plate descends beneath another, generating magma that rises through overlying continental crust.
The discovery expands understanding of northwestern Iran’s geological development, as previous research focused primarily on two major magmatic features: the Sananda-Sirjan Magmatic Arc and the Urumieh-Dokhtar Magmatic Arc. The newly identified system indicates that the region experienced a separate continental arc episode during the Late Cretaceous period. Researchers suggest that the Siah Cheshmeh-Khoy-Misho-Tabriz Fault may mark a significant tectonic boundary connected to Neo-Tethys Ocean system changes, potentially including slab rollback and volcanic arc migration processes.
Beyond its regional significance, the findings illustrate how Earth’s geological history becomes obscured over immense timescales. Ancient magmatic arcs rarely survive as continuous, easily recognizable formations due to tectonic fragmentation, erosion, sedimentation, and subsequent geological activity. By identifying surviving fragments of ancient structures, scientists can better understand tectonic plate descent, volcanic arc shifts, continental crust growth, and the closure of ancient ocean systems that shaped modern landscapes across the Eastern Mediterranean, Middle East, and Western Asia.
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