Petrography, Geochemistry, Genesis and Tectonic Setting of Bibi Maryam Granitoid (Afzal Abad-Nehbandan)

Bibi Maryam Granitoid body with 5 km2 exposure area is located in the east Iranian ophiolite mélange belt in Sistan suture zone. This intrusive body consists of tonalite- quartzdiorite and granodiorite. The main mafic minerals are hornblende and biotite in quartzdiorite-tonalite. Existence of microdioritic enclave in tonalite and its absence in granodiorites is one of the main characteristics of the body. Perthitic and granophyric textures in granodiorites represent low water vapor pressure and relatively fast crystallization, respectively. Geochemical study of rock samples shows that the body is calc-alkaline and metaluminous to peraluminous. Trace element patterns in spider diagrams represent a trough for Nb and enrichment for K, Rb, Ba and Th that indicate contamination by crustal materials. Although Bibi Maryam intrusive body cuts the ultramafic rocks, it lacks petrographic and geochemical characteristics of oceanic plagiogranites. The geochemistry of the body is comparable with I-type granitoids and based on tectonic setting it can be classified as orogenic and VAG type.