Petrology and geochemistry of some granitoid and intermediate rocks in southwest of the Qorveh area (Kurdistan)

Abstract

In the southwest of the Qorveh area, north of the Sanandaj-Sirjan zone, there are outcrops of acidic and intermediate rocks including monzogranite, granodiorite, tonalite and diorite. According to petrographical studies, plagioclase, alkali-feldspar, quartz, amphibole, clinopyroxene and biotite. Geochemical and mineralogical studies indicate that these rocks are metaluminous to some peraluminous, belonging to calc-alkaline magma series and having I-type characteristics. The REE normalized chondrite pattern of the samples show the M-type tetrad effect and relatively negative Eu anomalies. All of petrography and geochemistry data show fractionation crystallization REE-enriched minerals e.g. feldspar, amphibole, apatite and titanite followed by magma-fluids reaction in late crystallization phenomena are the most important factors for the formation of tetrad effect in these rocks. Lanthanides tetrad effects are recognizable in REE patterns of the samples and they change versus Y/Ho, K/Rb, Zr/Hf, Sr/Eu and Eu/Eu* ratios in accordance with evolution trend of granitoid. These rocks are enriched in LILE (i.e. U, Rb, K, Th) and LREE and show some depletion in Nb, Hf, Ti, Ta, Ba, Zr and P. LILE and LREE enrichment and HSFE depletion of the samples are indication of their formation in subduction zone

Keywords

• Petrology
• Geochemistry
• Qorveh area
• Sanandaj-Sirjan zone