The age and geochemistry of the Bardkish syenite, northwest Iran: Syenite formation during Neo‐Tethyan subduction

Abstract

SHRIMP U-Pb dating of zircon from two representative samples of the Bardkish syenitic pluton, Urumieh plutonic complex, northwestern Iran, yielded a Late Cretaceous weighted mean 206 Pb/ 238 U age of 91.1 ±0.8 Ma (Turonian). The pluton is characterized by high K 2 O content, Ti-Nb-Ta depletion, enrichment in light rare earth elements and large ion lithophile elements compared to high field strength element, Mg-rich biotite and calcic amphibole, suggesting a shoshonitic affinity. Geochemical features of the Bardkish syenite are consistent with derivation by fractional crystallization of initial mafic parent magmas. It is most likely that primary magma of the syenite originated from a metasomatized subcontinental lithospheric mantle source with minor crustal component, and underwent a fractional crystallization process during its emplacement. The estimates of trapping pressures and temperatures suggest that crystallization began at the middle crustal level (less than 11 km) near 700-730 C. The generation of the Bardkish syenite could be related to the subduction of Neo-Tethyan oceanic crust beneath the Central Iranian microcontinent and it possibly marks a major magmatic episode prior to the final closure of the Neo-Tethyan ocean in northwest Iran.

Post‐collisional alkaline lamprophyre magmatism in northern Iran: Implications from whole‐rock geochemistry and mineral compositions

“…Elsewhere in Iran lamprophyres and alkaline magmatism are mostly related to Neotethys suture zones along with the Zagros Mountain range, and around the Central Iranian Micro‐continent (CIM) (e.g., Jafari et al, 2020; Omrani et al, 2018; Omrani et al, 2013b). Late Cretaceous to Late Miocene lamprophyres with sannaite, camptonite, minette and spessartite compositions are reported from NW Iran (e.g., Aghazadeh et al, 2015).…”

Petrogenesis of mafic rocks from northwest Iran (Piranshahr) and comparison with northeast Iraq ophiolites: Implications for slab window magmatism in an evolving Neotethys arc

“…The onset of Neotethys subduction in Iran is recorded by the initiation of magmatism along the Sanandaj-Sirjan zone (Agard et al, 2005(Agard et al, , 2011Jafari et al, 2020;Mehdipour Ghazi & Moazzen, 2015;Rolland, 2017). Subduction beneath the Sanandaj-Sirjan zone is considered to have initiated in the Triassic (Dercourt et al, 1986) and possibly continued until the Eocene (Mazhari et al, 2015;Zhang et al, 2018).…”