Petrological constraints on the origin of the plutonic massif of the Ghaleh Yaghmesh area, Urumieh–Dokhtar magmatic arc, Iran

The Oligocene Ghaleh Yaghmesh plutonic massif (GYPM) consists of diorite, quartz-diorite, tonalite and granodiorite and evolving from metaluminous nature. All the samples are predominantly medium-K calc-alkaline series, having typical characteristics of I-type granitoids. A significant geochemical criteria of the GYPM is the impoverishment of high-field-strength elements (HFSE) (e.i. Zr, Nb, Ti and Hf) and the overabundance of large-ion-lithophile elements (LILE) (e.i. K, Sr, U, Ba and Cs), with respect to the light rare elements (LREE) as compared to chondritic concentration. These geochemical criteria suggest the involvement of sedimentary components in the generation of rocks studied. Furthermore, variable Pb/Ce amounts, linear trend of all rocks studied on Ti/Zr vs. Yb/Hf diagram, as well as some characteristics petrographic features (e.i. acicular apatite, corroded margin of the plagioclases, the amphiboles and some of the pyroxenes, oscillatory zoning of plagioclases) and the presence of mafic microgranular enclave (MME) indicate that the Ghaleh Yaghmesh parental magma was likely generated by the partial melting of a mixed source dominantly composed of amphibolite and possibly meta-sedimentary source. The overall geochemical and petrographic features are consistent with the interpretation of the Urumieh–Dokhtar Magmatic Arc as an active continental margin during subduction of the Neo-Tethyan oceanic crust underneath the Central Iranian microcontinent.