Geochemistry and tectonic environment of metaluminous granitoids of Sirjan, Urmia-Dokhtar magmatic belt, Iran

The Takht batholith is located to Sirjan and the southeastern part of the Urmia-Dokhtar magmatic belt. This complex has wide range of composition, including syenogranite, monzogranite, granodiorite, tonalite, quartz diorite, and gabbro. These rocks have clear contact surfaces with together, so that mafic rocks in margins and acidic rocks in centre of batholith were exposed. All mentioned units are I-type and have metaluminous and calc-alkaline nature, in composition. Abundance of hornblende, biotite and magnetite, absence of muscovite, garnet, cordierite..., wide variety of rocks, existence of magma mingling evidence, all are well-matched with their I-type nature. Linear trends of trace elements in harker diagrams and also identical trends of elements in spider diagrams, are indicated that the study rocks have genetic relationship with each other and have derived from the same parental magma. Enrichment of the study samples in LILE and LREE relative to HSFE and HREE show that these intrusions may have generated in an active continental margin from an enriched mantle source. In addition, negative anomalies of Nb and Ta along with enrichment of K, Rb, Th and Cs, implies to arc-related environment, as well as, interaction of crust and assimilation of crustal material during the process of their formation. Therefore, due to the Neotethys oblique subduction beneath the central Iran, basic parental magmashas formed from a metasomatized mantle. These melts during the ascent to upper crust horizons via assimilation and fractional crystallisation (AFC process) had formed the intermediate and felsic bodies. Finally the formed granitoids have intruded by deep faults especially Chahar Gonbad fault as compression injection.