ZIRCON U-PB AGE AND GEOCHEMICAL CONSTRAINTS on THE MAGMATIC AND TECTONIC EVOLUTION IN IRAN

This study reports new zircon LA-ICPMS U-Pb and whole-rock Ar-Ar age data, coupled with geochemical analyses, for magmatic rocks from different areas or continental fragments of Iran, including the Urumieh-Dokhtar magmatic arc (UDMA), Sanandaj-Sirjan structural zone (SSSZ), Alborz Range, Central Iran, Lut and Sistan suture zone. Our analytical results, combined with literature data, allow us to better constrain the magmatic and tectonic evolution of Iran and neighboring regions. As part of an ongoing project focused on Cenozoic pre- to post-collisional magmatism in the Caucasus/Iran/Turkey orogenic belt, this study also identifies the occurrences of several Paleozoic-Mesozoic magmatic events, such as Cambrian (518-511 Ma) granite and rhyolite from Bafq area in the Central Iran, Triassic (~203 Ma) granites from Binalud area in NE Iran, and Jurassic (~165 Ma) granitoids in the UDMA, SSSZ and Lut Block. While the first belongs to the widespread late Neoproterozoic-Cambrian magma suite in Iran affiliated with subductions along the margin of Gondwana, the third affirms the notion that the Neotethyan subduction and resultant UDMA started evolving from at least middle Jurassic. By dating a large number of Cenozoic igneous rocks in Iran, this study that would form a main dataset to explore the magmatic evolution before and after the Arabia-Eurasia continental collision reaches to following major conclusions: (1) the pre-collisional, calc-alkaline magmatism in the UDMA appears to cease southeastward, taking place in the late Oligocene (~27 Ma) in Tabriz, the middle Miocene (~16 Ma) in Esfahan and the late Miocene (~7 Ma) in Kerman areas; (2) the magmatism in the Alborz Range occurred in two stages, dominantly in the Eocene (peaked at ~50-38 Ma) and subordinately in post-late Miocene (<7 Ma), with a long magmatic quiescence; (3) the voluminous volcanism that occurred within the Lut and Sistan suture zone mainly erupted from the middle Eocene to Oligocene (44-25 Ma); and (4) the post-collisional magmatism, of small-volume though widespread, started from 15-11 Ma with intraplate basalts in Tabas and Neh areas, eastern Iran and from ~11 Ma with absarokites in Urumieh area, NW Iran.