Petrography, geochemistry and mineral chemistry of the Almogholagh intrusive rocks (Hamedan, Iran): Evidences for their shallow-level emplacement

The Almogholagh plutonic body with about 10 km2 is located 15 km of West of Hamedan city and on the Sanandaj-Sirjan zone. The Almogholagh pluton consists of diorite and gabbroic diorite, monzodiorite, quartz monzodiorite, monzonite, quartz monzonite, syenite, quartz syenite and alkali granite. Intergranular and granular are common textures of these rocks. The igneous rocks of the Almogholagh pluton were injected in two periods in the Cretaceous (from 138 to 95 Ma). Syenites, Quartz syenites and alkali granites were infused in the second phase and the remaining rocks have developed in the first stage. The igneous rocks of the Almoghlagh pluton have the A-type granitoids creteria. The magma generating the Almogholagh igneous rocks is formed by low degree partial meting (~7%) from depleted mantle with a garnet-spinel lherzolite composition. Results of the amphibole and plagioclase in the quartz syenite and quartz monzonite thermobarometry show that the mean temperature of the Almogholagh pluton formation is ~715 oC and the mean of its pressure is 2.18 Kb. Textural and thermobarometry evidences suggest a shallow-level (~5 km) emplacement for the Almogholagh pluton.