Fe-Skarn Deposits Related to the Almoughlagh Batholith, Western Iran

The Almoughlagh Batholith intruded during the Oligomiocene period the Triassic-Jurassic volcano-sedimentary sequence of the Songhor Series, occurring within the Sanandaz-Sirjan tectonic zone. The Baba Ali magnetite deposit is hosted by meta-dioritic rocks, the dioritic pluton intruded the Songhor Series earlier during the Late Kimmerian (-136Ma) orogeny. The Chenar deposit is much smaller and is hosted by metamorphosed carbonate rocks interbedded with the Upper Songhor Series. The intrusion of Almoughlagh Batholith skarnized the meta-diorite and the impure carbonate units and the associated hydrothermal activity was accompanied by magnetite mineralization. The Baba Ali deposit has been identified as a calcic Fe-skarn, while the Chenar deposit has characteristics of calcium-magnesium skarn. The batholith consists of rocks belonging chiefly to the quartz-syenite and syenogranite groups, which are low in modal quartz, metaluminous to peraluminous and calc-alkaline in composition. A descending temperature regime, beginning at the peak of thermal metamorphism (566°C) and ending with the main phase of magnetite mineralization (450-350°C) has been deduced.