New U-Pb zircon geochronological data for Takestan magmatic rocks (Western Alborz) and their significance for the interpretation of Paleogene magmatism in Iran

The Takestan area is in the western part of the Alborz magmatic arc. Magmatic rocks of the area consist of plutonic rocks (e.g. granitoids), effusive volcanic, and pyroclastic rocks. Using U-Pb zircon LA ICP-MS dating, we conclude that major parts of Takestan plutonic rocks were emplaced at 41-39 Ma (Late Eocene, Bartonian), but a small part of these rocks have ages of similar to 37 Ma (Late Eocene, Priabonian). The dacitic rocks have an age of similar to 39 Ma (Late Eocene, Bartonian) and the rhyolitic rocks are the youngest part of the magmatic rocks of the region with ages of 37-35 Ma (Late Eocene, Priabonian). Old zircons are present in all of granitoid and volcanic samples, except for a dacitic sample. They are interpreted both as earlier components in a long-lived magma chamber and inherited zircons from older continental crust. The age of magmatic rocks in the western part of the Alborz magmatic arc decreases from east to west, but the ages of the majority of them are limited to Palaeogene. The studied rocks like other Palaeogene magmatic rocks of Iran were possibly formed in a subduction related tectonic environment. Indeed, the Palaeogene magmatism of Iran is akin to geodynamic events related to Neotethyan subduction beneath Iranian micro-continent at the southern part of Eurasia.