Studies of magmatic evolution and petrogenesis of the granitoid bodies of Yazd

The granitoid bodies of Yazd belonging to the Oligo-Miocene in age located in the central part of Urumiaeh-Dokhtar volcanic belt. These bodies intruded into the Cretaceous limestone of the Taft formation and pyroclastic rocks of the Eocene. These rocks generally show granular texture; and porphyroid، granophyric، graphic، perthite، myrmekitic and anti-rapakivi textures are occasionally identified. On the basis of field observations and petrographic and geochemical studies، the Yazd intrusive bodies fall within the range of alkali-granite to tonalite in composition and belong to high temperature I-type (Cordilleran) ACG، VAG، Post-COLG and HSS groups. Various geochemical diagrams show the enrichment of LILE، LREE and depletion of HREE and HSFE. These are the characteristics of calc-alkaline magma developed in subduction regime of active continental margin (ACM). Therefore، it is suggested that the magma was generated from the subducted oceanic crust (Neothety) and evolved mantle wedge above it. The magma was generated at the base of crust owing to crust melting and subsequent differential crystallization، assimilation and contaminations (AFC)، all are involved in magmatic evolution. Proposed geotectonic model of the area could be similar to the central Andes model، in which magma generated by polygenic and polystages phenomena.