سنگ نگاري، ژيوشيمي و سازوكار جايگيري كمپلكس حلقوي هشتسر

Petrography, Geochemistry and Emplacement Mechanism of Hashtsar Ring Complex

Hashtsar ultramafic - mafic intrusive complex is located at about 20 km east of the Kaleybar city in the eastern Azerbaijan Province. This alkaline ring complex is formed by the penetrative of undersaturated and oversaturated different magmatic phases with Late Eocene to Oligocene - Miocene ages. Petrographical studies show that this massive consists of three main phases. The first phase is composed of magnetite mela alkali pyroxenite, plagioclase bearing alkali pyroxenite and mela alkali gabbro with coarse grained gabbroic dykes. The second phase consists of the nepheline bearing leuco gabbro - diorite to nepheline monzodiorite and nepheline monzonite, and the third phase is syenite and quartz - monzosyenite to granite with calk-alkaline affinity. Geochemical studies indicate that undersaturated phases are intensively enriched in trace elements, especially in LILE and LREE. These magmas have generated from the parental magma with a potassic alkaline affinity from a metasomatic mantle. The different rocks types of undersaturated phases were produced by the liquid immiscibility, crystal fractionation and accumulation processes. The calc-alkaline magma of the third phase is probably resulted from the lower crust melting due to penetrative of first and secondary phases. Particular and ring emplacement of this complex is concluded by the eruption and discharge of huge and zoned magma chamber, after the caldera subsidence such as, volcanic string of Majid Abad formation in the Hashtsar region.