Petrographic and petrogenetic studies of adakitic magmatism of Gavdel (Shivar Dagh) in Garehdagh-South Arminian Zone (Northwest of Iran)

Gavdel intrusive body situated in NW Iran and NE of Urumieh-Dokhtar zone a part of Garehdagh, South-Arminian Zone (Arasbaran). The major outcrops of intrusive including 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 with SiO2 in the range of (59.1-67.8 wt%), Al2O3 (14.09-18.3 wt%) percent, high content Sr (507.18-1150 ppm), high ratios of Sr/Y (32.93-83.54), La/Yb (14.64 – 87.47) and low contents of Y (12.05-16.13 ppm), which can be indicate 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 contents of HREE and Y can be related to occurrence of garnet or amphibole in residual source of adakitic magmas. High content of Sr and depletion of Ta, Nb and Ti can be related either to absent of plagioclase and presence of Fe-Ti oxides in melt residue or fractionation of titanomagnetite and amphibole minerals with respect to petrographic indications. Tearing of subduted slab and their partial melting in concert with crustal assimilation through magma arising can be produce adakitic magma in studied area and NW Iran.