Original paper

Geochemistry and petrology of basaltic lavas from NE-Qorveh, Kurdistan province, Western Iran

Torkian, A.; Salehi, N.; Siebel, W.

Abstract

Quaternary volcanic rocks at NE-Qorveh, Kurdistan province, western Iran, formed in a post-collisional continental arc setting. This paper focuses on the basaltic rocks of this area. These rocks display microlitic to porphyritic textures with clinopyrox- ene and olivine as phenocrysts and plagioclase, pyroxene, amphibole and biotite as microcrystals. Pyroxenes are either normally zoned or show growth zones with sieve textures. The basalts are alkaline in composition with variable amounts (5–14 %) of normative nepheline. They display positive correlations between MgO and CaO, FeO, TiO2, Ni and Cr and negative correlation between MgO and SiO2 and these trends can be accounted for by various degrees of fractional crystallization. Geochemical characteristics such as enrichments in large ion lithophile elements (Ba, Sr) and light rare earth elements (e. g., La, Ce), negative Nb and Ta anomalies, and positive Pb, Ba, Th anomalies suggest that the lavas were derived from an undepleted or a re-enriched mantle source. High ratios of (Th/Yb)N, (Tb/Yb)N and (Dy/Yb)N and Nb/La < 1 and low ratios of Zr/Nb and Y/Nb show that the melts were generated from a garnet peridotite source by low degree of partial melting.

Keywords

iranintra-plate volcanismne-qorvehalkali-basaltsubduction