Petrography, Geochemistry and mineral chemistry of igneous rocks in southwest of Qeidar, northwest of Iran

The studied area is located in the south of Zanjan province, southwest of Qeidar and in Urmia-Dokhtar magmatic arc. The igneous rocks of the southwestern region of Qeidar include volcanic rocks (basanite, analcime bearing basalt, basalt, trachybasalt, and trachydacite) and pyroclastic rocks (volcanic breccia and agglomerate). In the mentioned rocks, the analcime bearing basaltic rocks have a larger volume in the region. The main minerals are plagioclase, analcime and clinopyroxene, along with some secondary minerals, including opaque minerals. According to the microprobe results, pyroxenes are of diopside type and plagioclase is of anorthite-rich type. The main texture of these rocks is porphyritic texture. In the studied area, there are dykes with porphyry texture containing very coarse euhedral pyroxene crystals that they have cut Cretaceous units and Eocene volcanic rocks. Based on chemical data, the lava flows have nearly alkaline affinity. The basalt spider diagram has positive anomalies for elements such as Cs, Ba and Pb and negative anomalies for elements such as Nb and Ti. The tectonic environment of the studied volcanic rocks is active continental margin, and their magma has been originated from the metasomatized mantle wedge with fluids released from the subducting plate, and during ascent they have suffered a little crustal contamination.