Petrology and source of Plio-Quaternary volcanic rocks in southwest of Nir, South of Yazd

In the southeast of Nir, south of Yazd Povince, several acidic volcanoes  rocks are exposed and form the youngest volcanic rocks in this region with dacite-rhyodacite composition. These rocks are composed of plagioclase, hornblende, biotite and quartz phenocrysts with trachytic and hyallomicrolithic porphyry texture. Based on geochemical data, the magmatic affinity of these rocks is calc-alkaline with enrichment of LILE and depletion of HFSE. These characteristics with steep decrease pattern of rare earth elements and negative anomaly of HFSE, such as Nb, Ti and P, indicate the formation of magma in active continental margin. Higher levels of SiO2, Sr, Sr/Y, and La/Yb with low levels of MgO, Yb, and Y, indicate high silica adakite affinity. It seems that the formation of parental magma of these rocks is consequence of the melting of garnet amphibolite or eclogite rocks of subducted metamorphosed Neotethys oceanic lithosphere in the Central Iran- Arabian plate collision zone during the Neogene time.