Petrology and Geochemistry of the Granitoid Massif of Boroujerd
Abstract
The Boroujerd granitoid massif is as a small portion of Sanandaj-Sirjan zone. It is elongated and parallel the prevailing schistose it in the metamorphic rocks by the trend of NW-SE and consist of quartz diorites, granodiorites, monzogranites and sphene granite. Granodiorites are the most dominant rocks. Petrological, mineralogical, field and geochemical investigations suggest that the Boroujerd granitoid is similar to those of the high-K calc-alkaline series, metaluminous to weakly peraluminous, and displays features typical of I-type granites. Low Al2O3/(FeO+ MgO + TiO2) and (Na2O + K2O) / (FeO + MgO + TiO2) ratios, and the trace and rare-earth elements patterns suggest that these rocks formed along a destructive plate margin and were derived from a lower crustal source. This granitoid magma involves partial melting of lower crustal protoliths and frac-tional crystallization of the melts in higher crustal levels can generate the whole spectrum of rock types represent in the Boroujerd massif. Mantle-derived basaltic magmas emplaced into the lower crust are the most likely heat sources for partial melting.
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