Petrology of alkaline lavas in North Jirandeh (East of Lushan)

In the north of Jirandeh and east of Lushan, which are located in the mountains south of the central Alborz, a series of volcanic rocks are unconformablly located on the Middle Eocene limestone. These rocks have alkaline affinity of different types of lamprophyre and are studied for the first time from the petrology point of view. The texture of these rocks is porphyric to microporphic with microlithic matrix. The phenocrysts and microphenocrysts of the collected samples are generally olivine, alkaline pyroxenes and biotite, which are located in olivine, pyroxene, plagioclase, amphibole, very fine nepheline crystals, apatite and metal ores groundmass. Geochemical studies of these rocks indicate that these rocks are alkaline lamprophyres and the magma is the result of partial melting of an asthenospheric mantle source similar to OIB. They are classified in garnet lherzolite facies and were emplaced in an intercontinental rift tectonic environment.