Petrogenesis and tectonic implications of Neoproterozoic to Cenozoic A-type granitoids in NW Iran: geochemical and tectonic constraints

In the northwest of Iran, in the Sanandaj-Sirjan zone, type A granitoid masses related to the Late Neoproterozoic-Lower Cambrian (Ajab Shir rhyolites, Chaipareh, Mahneshan, Misho, Saqez and Sufi Abad), Mesozoic (south of Dehgolan, Ebrahim-Attar), Cenozoic (Harris and Takab) exist. In terms of geochemical characteristics, the granitoid rocks of Late Neoproterozoic-Lower Cambrian time show the characteristics of magmas related to volcanic arcs, which were formed due to a tectonic window (SCLM) in the final/post-pan-African orogeny stages. In other words, the magmatism of the active continental margin of Cadomin in Iran occurred after the main phase of Pan-African orogeny and simultaneously with the stretching of the continental crust in the Arabian-Nubian shield. But the granitoid rocks of the Mesozoic era (Late Triassic- Early Jurassic) were formed by Paleo Tethys subsidence. Cenozoic (Eocene) granitoid rocks were formed in a tensile environment after the collision of the Arabian and Eurasian plates. Most A-type granites are peraluminous, rich in iron and show enrichment of LREE elements compared to HREE. Also, the amount of MgO, CaO, Sr, Ba, Nb-Ta and Eu is low in them. Most of the granites of Sanandaj-Sirjan zone are located in the A1 range, but some are also located in the A2 range, which is due to metasomatism by fluids originating from the oceanic crust or slab-derived melts. All these granites were formed in a tensile environment.