LAUSR

Abstract The Almogholagh batholith in the northern Sanandaj-Sirjan magmatic–metamorphic zone comprises three intrusive bodies (gabbroic diorite, quartz syenite, and quartz monzonite) that were generated during the northeastward subduction of Neo-Tethys beneath the Iranian sector of the Eurasian plate. These bodies intruded at different time phases and are related to post-collision magmatism. The quartz syenite and quartz monzonite rocks with specifications of metaluminous, generally ferroan, alkalic to alkali-calcic types, high content of Na 2 O + K 2 O, Zr, Ce, Ga, Y, Nb, Ta, and rare earth elements, and depleted in Eu, Sr, and Ti show borderline characteristics between A 1 and A 2 types granitoids but with more affinity to A 2 type. The gabbroic dioritic rocks show borderline specifications between A 1 and I types rocks but with more affinity to I type. Distinctive spiked peak patterns in spider diagrams accompanied by (La/Yb) CN values equal to 2.44 to 6.11 and a Ba/La ratio >3 indicate the magmatism activity in the volcanic arc environment. The characteristics (Ba/Rb) PN PN 143 Nd/ 144 Nd > 0.512638 in some samples, e t Nd > 0, e t Sr > 0, and high content of Nb, Ta, and Zr (589 ppm) demonstrate the involvement of the mantle source, subducted slab fluids, high flux of mantle-derived halogen-rich volatiles, and contamination within the crust during the petrogenesis of intrusions. After the initial collision, the operation of minor subduction (with slab break-off) or foundering of the lithospheric mantle (delamination) occurred because of asthenospheric upwelling and heat flows in the mantle in the Sanandaj-Sirjan zone. Stretch and local disruptions were created by these heat flows; simultaneously, magma was formed and ascended upward.