Petrological and Geodynamical Constraints of Chaldoran Basaltic Rocks, NW Iran: Evidence from Geochemical Characteristics

The Chaldoran area in the northwestern portion of Iran has a Mesozoic oceanic crust basement. The studied rocks of this region can be divided into three groups: ophiolitic gabbros and pillow lavas, ophiolitic volcanoclastics and Eocene lava flows. Ophiolitic mafic rocks exhibit a continental volcanic arc nature while Eocene lava flows are of an OIB-like nature. During the Mesozoic era, the Chaldoran region was situated in the active continental margin of the Iranian plate due to Neotetyhan subduction beneath the SSZ (Sanandaj-Sirjan Zone). As the Neo-Tethyan subduction regime changed, a rift in the Chaldoran area was generated which caused a continental back arc basin during the Upper Cretaceous period. A spreading basin in the oceanic ridge along with the creation of newly formed oceanic crust gave rise to oceanic islands which became active and formed volcanoclastic rocks in the Chaldoran Oceanic crust. These were the result of ascending continental arc nature plumes that formed in the sub-oceanic crust and extended up to the Neo-Tethys subducted slab in the mantle wedge. After the basin finished spreading in the early Paleocene, sedimentation followed continuing up to the Middle Eocene. During the Upper Eocene, alkaline and OIB-like volcanism was active in the Chaldoran area due to the breaking off of the Neo-Tethyan subducted slab in the sub-oceanic crust of the Chaldoran area causing the development of an asthenospheric window.