The Petrology and Geochemistry of Granitoid Rocks in the Troud Area of Northeastern Shahrood

The Troud area is located 120 km northeast of the city of Shahrood in the northern part of the Central Iran Zone. Granitoids in the Troud area range from monzonite to granite. Quartz, plagioclase, and orthose were the main minerals found in the granitoids. Accessory minerals included biotite, hornblende, sphene, and opaque minerals. Various textures of granular, graphic and prethite were observed in these rocks. Based on various diagrams of major and trace elements, this rock is I-type arc calk-alkaline, meta to para-aluminous, of continental origin formed at the subduction zone. All these characteristics, combined with low Al2O3/(FeO + MgO + TiO2) and (Na2O +K2O)/(FeO + MgO + TiO2) ratios along with high Mg# values, suggest that it originated through dehydration melting of alkaline mafic lower crustal source rocks.