Original paper

Petrology of leucocratic granitoids in the northwest of Iran with emphasis on leucocratic I-type granites from SW Saqqez

Athari, Seyed Fakhraddin; Sepahi, Ali Asghar; Moazzen, Mohssen


The leucocratic granitoids of NW Iran including S-type, A-type and I-type leucogranites, are located in the Sanandaj-Sirjan Metamorphic Belt (SSMB) and Alborz-Azarbaijan Zone (AAZ). I-type leucogranites have been reported from the BukanMahabad, Meshgin-Shahr and Saqqez areas. The Tamuteh leucogranites (SW Saqqez) are located in the SSMB and are composed of syenogranite, monzogranite, granodiorite, tonalite and microtonalite. These rocks are subalkaline (calc-alkaline), metaluminous and weakly peraluminous and their characteristics resemble the I-type magmatic granites. They are also magnesian and weakly ferroan, calc-alkalic to calcic and diopside-normative. They are cut by later lamprophyric dykes. Leucogranites contain low concentrations of Rb, Y, FeOtot+MgO, Zr, Th, U, Ce and high concentrations of SiO2, Ba and high Sr/Y and Ba/Rb ratios. They show general trends of decreasing contents of some major oxides (Al2O3, Fe2O3, P2O5 and TiO2) with increasing SiO2 but CaO and K2O amounts show no regular patterns. According to tectonic discrimination diagrams, they were generated in a volcanic arc setting. Normalized trace element patterns show enrichments in LILEs (Rb, Ba, K, Th and Ce) relative to HFSEs (Nb, Zr, P and Ti) and are very similar to calc-alkaline subduction-related rocks from orogenic belts. Major and trace element signatures of these rocks indicate that they may have resulted from contamination of mantle-derived magmas by continental crust during a subduction event.


alborz-azarbaijan zonecalc-alkalineirani-type leucogranitelamprophyreleucocratic granitoidmetaluminoussanandaj-sirjan metamorphic beltsaqqeztamutehvolcanic arc setting