Mineralogy and mineral chemistry of lamprophyres in the NW Iran

There are numerous outcrops of lamprophyric rocks, as sill and dikes, in the northwestern part of Iran. These rocks can be classified in two mica- and amphibole-rich types. Amphibole-rich type includes amphibole, olivine psudomorphs, and clinopyroxene phenocrysts in the matrix of feldspar and altered glass. Mica-rich lamprophyres include mica and clinopyroxene phenocrysts in the matrix of feldspar and glass. Amphiboles represent kaersutite composition and mica crystals mainly show phlogopitic composition. Clinopyroxene crystals have mainly salite-diopside composition. Clinopyroxenes in the amphibole-rich type have higher Al2O3 content. Studied lamprophyres are formed in a high oxygen fugacity condition and their magmas have been experienced low pressure crystallization. According to nature of minerals, mica-rich lamprophyres have calc alkaline nature and are minette and amphibole –rich type represents alkaline nature and can be consider as comptonite. Mica-rich lamprophyres originated from phlogopite and/or potassic amphibole bearing metasomatized lithospheric mantle in a orogenic tectonic setting. Amphibole-rich lamprophyres probably originated from a lherzolite mantle that includes fluid-bearing minerals.