Petrology and genesis of Vash granitoid NW Natanz (Isfahan)

The Vash granitoid is located in NW Natanz and is a part of Uromieh-Dokhtar magmatic belt in Central Iran. This pluton is probably of Oligo-Miocene age and is the result of extensive magmatism which occurred during and post of the Alpine Orogeny.The composition of the pluton ranges from granodiorite to tonalite. The main minerals are quartz, plagioclase, alkali-feldspar and ferromagnesian minerals are biotite and amphibole. It contains a number of dioritic enclaves with different sizes. Based on geochemical studies, the Vash granitiod is similar to those of the subalkaline, calcalkaline series, metaluminous, and displays typical features of magnesian I-type granites. The pluton is characterized by enrichment in large ion lithophile elements (LILE) such as Rb, Ba, K, Ce and depletion in high field strength elements (HFSE) such as Y, Nb and Zr. The chondrite normalized REE patterns are characterized by moderate to high LREE enrichment [(La/Yb)N=7.93-13.17] and unfractionated HREE [(Gd/Yb)N=1.09 to 1.88]. Granodiorites show least fractionated in HREE and a weak negative Eu anomalies (Eu/Eu*=0.69-1.16). The studied magma was likely derived from primary magma in the lower crust originated by partial meling of crustal protoliths as well as basaltic magmas formed by partial melting of mantle wedges. The Vash granitoid displays mineralogical and geochemical characteristics typical of volcanic arc granites related to an active continental margin. Tectonic setting of Vash granitoid may be syn-subduction magmatism or post-collisional magmatism due to extensional phases after collision of Lut microcontinent and Arabic plate.