Mineral chemistry and petrology of lamprophyric dyke in Guyposhti Mountain (northwest Maragheh-East Azarbaijan)


Department of Earth Sciences, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran


The study area is located about 30 km northwest of Maragheh in East Azerbaijan. The lamprophyric dyke intruded the Shemshak sedimentary rocks. Based on stratigraphic evidences, the age of dyke is probably Early Cimmerian. The principal minerals of the lamprophyric dyke consist of plagioclase (andesine -oligoclase), biotite (eastonite), phlogopite, olivine and clinopyroxene (diopside) with ocellar texture. The average chemical composition of clinopyroxene and plagioclase is En42.3, Wo46, Fs11.7 and Ab51.74, An30.92, Or17.34 respectively. According to the mineralogical and geochemical evidences, the studied lamprophyre samples are kersantite belonging to calc-alkaline lamprophyre.The plotted spider diagrams for the rock samples indicate the light rare-earth elements (LREE) and incompatible elements enrichment compared to heavy rare earth elements (HREE). The parent magma is probably generated from garnet lherzolite mantle with low rate partial melting. The studied lamprophyre dyke formed in intraplate and post collision environment which translocated possibly in basins and ruptures in related with fault systems.