Alkaline lamprophyric province of Central Iran

Paleozoic lamprophyres exhibit good exposures in the western part of the Central–East Iranian microcontinent. These rocks crop out as volcanoes, dykes, and plugs. The constituent minerals are amphibole, clinopyroxene, plagioclase, K‐feldspar, olivine, Cr‐spinel, titanite, biotite, and ilmenite. The main textures in volcanic lamprophyres are porphyritic, trachytic, microlithic, and variolitic, whereas in dykes and plugs, intergranular texture is common. These lamprophyres are regionally metamorphosed in some areas. Petrographical and geochemical characteristics of the studied rocks suggest that they are classified as alkaline lamprophyres and camptonites. They are enriched in alkalis (Na₂O + K₂O), large ion lithophile elements, and light rare earth elements, and the features of trace element concentrations are similar to those of within‐plate basalts. This study suggests that the lamprophyres were derived from different degrees of partial melting of metasomatized amphibole‐bearing spinel lherzolite. Subduction of Paleo‐Tethys oceanic crust from the Early to late Paleozoic resulted in enrichment in fluids in the mantle, and lamprophyric magmatism occurred along the minor and major faults. This limited but typical lamprophyric magmatism in a broad area of Central Iran suggests that, in spite of the long length of the Paleozoic (～250 my), it was a relatively calm era from the viewpoint of magmatism in Central Iran.