Petrographic and petrogenetic studies of adakitic magmatism of Gavdel (Shivar Dagh) in Garehdagh-South Arminian Zone (Northwest of Iran) (Irankuh Pb-Zn deposit, Southwest of Isfahan)

Gavdel intrusive body, situated in NW Iran and NE of Uromieh-Dokhtar zone, is a part of Garehdagh, South-Arminian Zone (Arasbaran). The major outcrops of intrusive include of granodiorite, monzonite accompanied with granodioritic dyke. The studied samples display granular texture with essential minerals of, plagioclase, K-feldspar, amphibole ± quartz ± clinopyroxene. Geochemically, the studied rocks characterized by SiO2 in the range of (59.1-67.8%), Al2O3 (14.09-18.3%), high Sr (507.18-1150 ppm) content , high ratios of Sr/Y (32.93-83.54), La/Yb and low Y (12.05-16.13) contents, which can indicate the adakitic characters of studied rocks. These features of Gavdel intrusive display geochemical similarity with high SiO2 adakites (HAS) that comprise enriched LREE, LILE and depleted HFS elements such as Ta, Nb, and Ti. The fractionated REE pattern and low HREE and Y amount can be related to the occurrence of garnet or amphibole in residual source of adakitic magmas. High content of Sr and depletion of Ta, Nb and Ti can be ascribed either to the absence of plagioclase and the presence of Fe-Ti oxides in melt residue or fractionation of titanomagnetite and amphibole minerals with respect to petrograhic indications. Subducted slab breaking off followed by its partial melting and the overlying sediments accompanied by crustal assimilation through magma rising generated the magma in the studied area and the NW of Iran.