Petrology and tectonomagmatic setting of granitoid intrusions of Mahoor area, southwest of Nehbandan


Department of Geology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran


The Mahoor area is located, about 135 km south-west of Nehbandan in the center of Lut Block. The area comprises outcrops of Eocene volcanic and pyroclastic (Eocene) that were intruded by several intrusive rocks consist mainly of diorite as dykes and stocks. Chemical classification shows that plutonic rocks are gabbro-diorite, diorite, monzodiorite and tonalite. These granitoids are high-K calc-alkaline series and they are meta-aluminous. Magnetite suitability (1485×10-5 SI) mineralogical and geochemical features show that they belong to magnetite granitoid series (I type). Enrichment in LREE rather than HREE and enrichment in LILE rather than HFSE, and typical anomalies of Nb, Ta and Ti are important evidences that show the intrusions were formed in a mamgmatic belt of subduction zone. Eu element show negative anomaly and Eu/Eu* ratios are from 0.65 to 0.88. Negative anomaly of Eu is due to presence of plagioclase in magma source. Geochemical studies show that Mahoor granitoids are co-genetic and they formed in subduction zone and belong to calc-alkaline volcanic arc setting in active continental margins. Mineralization is present as disseminated and hydrothermal vein related to monzonite and diorite porphyry.