Under the mountains of northwestern Iran, traces of a volcanic system that operated about 100 million years ago are preserved. An international team led by Istanbul Technical University has identified the remains of a previously unknown continental magma arc complex.
The system is called the Azerbaijan Continental Magma Arc. It was active between 101 and 97 million years ago, during the Late Cretaceous, when the ancient Tethys Ocean was undergoing significant geological changes.
The discovered structures are located in an area that is now part of the collision zone between the Arabian and Eurasian plates. It was the movement of these plates that gradually changed the geological appearance of the Middle East and Western Asia.
The traces of the ancient volcanic system were not easy to recognize. Later tectonic movements deformed the rocks, erosion removed some of them, and sedimentary deposits covered others. Thus, an entire magmatic arc complex has been left out of earlier reconstructions of Iran's geological past.
In the northwest of Iran, geologists have discovered the remains of a volcanic arc that was active about 100 million years ago. Zircon age measurements connect the scattered rocks. More on this: https://t.co/DaAie2aITi #Geology https://t.co/QQXBrafYlN
— Forschung und Wissen (@ForschungWissen) October 29, 2026Scientists have studied volcanic and plutonic rocks from several locations in the northwest of the country. The results indicate that they are associated with continental magmatism – a process that usually occurs in areas where one tectonic plate is subducted under another.
„This study shows that the magmatic history of northwest Iran is more complex than previously thought. "By combining geochronological, isotopic and geochemical data, we have identified a Late Cretaceous continental arc that was subsequently hidden by tectonic processes," says Ali Mohammadi of Istanbul Technical University.
The discovery can help geologists trace how ancient plates moved, how volcanic arcs changed their location and how continental crust formed. It also provides a new opportunity to study the processes that led to the gradual closure and final disappearance of the Tethys Ocean.
Tethys played an important role in the development of the Eastern Mediterranean, the Middle East and West Asia. Its disappearance is associated with the formation of the modern relief in these areas. The newly discovered magma arc adds a missing piece to this story and shows how fragments of ancient geological systems can survive even though the structure itself has long since disappeared from the surface.
The study is published in the journal Geoscience Frontiers.