Tectonomagmatic Evolution of the Paleogene Arc System of Iran

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A team of scientists from the California Institute of Technology, in collaboration with scientists from the University of Tehran and University of Lyon, are conducting a a combined field and laboratory study aimed at understanding the tectonic evolution of southeastern Iran between 35 and 50 million years ago. Volcanic rocks in this region are predominantly alkalic in character, rather than the calc-alkalic composition expected for subduction-related volcanism associated closure of an ocean basin prior to continental collision. Structures in this area are similar to those found in core complexes in western United States, suggesting that the lava sequences were associated with extension. The investigator team is testing the hypothesis that a temporal relationship exists between magmatism and lithospheric extension within the arc system and are comparing the timing of extension with that of the development of the alkaline magmas. Structural, paleomagnetic, and thermochronologic studies are being conducted in the Saghad area in southeastern Iran. The team is mapping the detachments and their hanging wall imbricate normal faults, characterizing the shear direction in mylonites below the fault zone, using thermochronology to determine whether footwall gneisses and plutons cooled rapidly in association with unroofing along the Neybaz-Chatak fault zone, and using paleomagnetic studies of Cretaceous limestones to assess vertical axis rotations within and around the core complexes.