Geochemistry, petrogenesis and magmatic evolution in the olivine gabbro dikes of south of Germi city


1 Department of Geology, Faculty of Sciences, Lorestan University, Khorramabad, Iran

2 Department of Geology, Faculty of Earth Sciences, Shahid Beheshti Universiry, Tehran, Iran

3 Department of Geology, Payame Noor University, 19395-3697 Tehran, I. R. of Iran


An association of olivine-gabbroic dikes is located in the northwest of Iran, south-southwest of Germi city (Ardebil province), with N-S trend in the Talesh zone. Mineralogically, these rocks consists of phenocrysts of plagioclase, clinopyroxene (augite) and olivine with minor minerals of biotite, amphibole, apatite, opaque and zircon. The dominant textures in these rocks are porphyry, granular and ophitic. From the chemical aspect, the parent magma is alkaline nature. The spider diagram with a positive lead anomaly indicates the crustal assimilation process with LREE enrichment compared to HREE which is related to enriched mantle. The trend of major oxides vs. SiO2 on Harker diagrams indicates evolution process through differentiation, with slight metasomatism which can be related to subducted slab derived fluid. Based on the aforementioned evidences, the olivine gabbros were formed from an extensional back arc basin resulting from subducting oceanic crust in the northern branch of NeoTethys located between the blocks of Toriid-Anatolli in the south of Armenia beneath the crust of Quafqaz and Armenia.