Petrogenesis of granitic unit of Naqadeh complex, Sanandaj-Sirjan Zone, NW Iran

The granitic unit is a component of the Naqadeh plutonic complex, NW of Sanandaj-Sirjan Zone (NW Iran). This unit is composed of high-K calc-alkaline, slightly peraluminous (ASI = 1.12-1.17) evolved monzogranites. These monzogranites have 41.85 +/- 0.81 Ma (zircon U-Pb sensitive, high-resolution ion microprobe (SHRIMP) age) with two inherited zircon ages of 98.5 +/- 1.7 and 586.6 +/- 13.1 Ma, respectively. The only enclave type consists of quartz-amphibolite enclaves indicating residual parental rocks. Chemical and isotopic ((87)Sr/(86)Sr(40Ma) = 0.708638; epsilon Nd(40Ma) = -4.26) characteristics of monzogranites suggest that they could be derived by partial melting of crustal mafic rocks followed by some assimilation of metasedimentary rocks. With regards to inherited zircon age and quartz-amphibolite composition of Naqadeh granite, the old mafic rocks of this complex (Naqadeh dioritic rocks with similar to 100 Ma) can be considered as parental rocks, and their partial melting under high water content, and assimilation of produced melt by metasedimentary rocks, would lead to the generation of a Naqadeh granitic unit.