Petrology of the Molataleb village granitoid (North of Aligudarz), NW of Isfahan, low temperature peraluminous I-type

The Molataleb granitoid lies in the Sanandaj-Sirjan Zone and composed of granodiorites، tonalites and minor diorites which intruded into the Jurassic (Lias-Dogger) shales and slates. Quartz، plagioclase، orthoclase، biotite، amphibole، tourmaline، andalusite، garnet، apatite and zircon are the major and minor minerals of these rocks. The essential petrological characteristics of the body are، the P2O5 content decreases versus the SiO2 wt% increases، the content of aluminium saturation index (ASI= 1-1. 1)، the trend of increasing of Zr vs SiO2، the chemistry of biotites and the formation temperature of the body (500-700°C)، all are the remarkable features of low temperature medium peraluminous I-type granites. The descending trend of Al2O3، TiO2، Eu and Zr against Larsen Index and also the decrease of K/Rb ratio versus Rb suggest fractional crystallization of plagioclase in the studied granitoid samples. The chondrite-normalized REE''s diagrams display LREE''s enrichment relative to HREE''s. This can be owing to low degree partial melting or relatively enrichment of alkali elements in the source rocks associated with subduction zone. The alkali elements enrichment may be due to crustal contamination. Also، the high level of LILE''s and the HFSE''s depletion indicates that magmatism occurred in subduction of Neotethyan oceanic crust beneath Central Iranian microplate and the studied intrusive body is classified as volcanic arc granite (VAG).