Petrology and geochemistry of the post eocene felsic intrusives in ardestan area, Northeast of Isfahan, Iran

Felsic intrusions in the studied area are post Eocene and this region is located in the northeast of the Esfahan province. This area belongs to Uremia - daughter magmatic belt in Central Iran. Composition of Felsic intrusions are granodiorite and tonalite. The main minerals include: quartz, plagioclase, alkali feldspar and ferromagnesian minerals are amphibole are biotite. Most of ferromagnesian minerals alterated to chlorite and epidote. On the base of geochemical studies, granitoids are ranging from sub-alkaline, metaaluminous, magnesium series and Itype igneous rocks. These rocks enriched of LILE such as Rb, Ba, K, Ce and depletion of HFSE such as Y, Nb and Zr. REES chondrite normalized patterns indicate moderate to high enriched LREEs [(La/Yb)N= (1.27-18.22)] and a relatively depleted of HREEs [(Gd/Yb)N= )1/02-3/32)] with Eu Negative anomalies [Eu/Eu*= (9.55-9.57)]. Felsic magma are generated partial melting of crustal protoliths and mantle-derived basaltic magmas emplaced into the lower crust. These felsic intrusions rocks have mineralogical field and geochemical characteristics typical of volcanic arc granites related to an active continental margin. Probably, the Ardestan granitoids are the result of the subduction of neo- Tethyan oceanic plate below the Lut microcontinent and this oceanic residual plate during Mesozoic to Cenozoic time. Dehydration of subducted oceanic crust and partial melting of mantle wedge caused partial melting of subcontinental lithosphere, which resulted in the formation of metasomatized and enriched mafic arc magmas, and led to the formation of the Ardestan granitoid.