Evaluation of impact processes in the formation of Neshveh volcanic rocks, NW Saveh

Neshveh volcanic rocks located in the NW Saveh are parts of the Uromeyeh-Dokhtar magmatic arc. The rocks are mainly basalt, basaltic andesite, andesite and trachyandesite in composition. Petrographical studies represent some evidences for the lack of equilibrium between crystals and magma, such as sieve texture, two generation of fresh and altered plagioclase, reaction rim, corrosion and rounding of phenocrysts. Major and trace element diagrams show, although crystal differentiation was effective in the evolution of the study rocks, the scatter and unusual trends, which are observed in some diagrams in comparing with fractionation trend, reflect magma mixing and contamination were also important during magma generation. Inconsonance and high variations in Sr concentrations together with binary diagrams of Nb/Y-Nb and Rb-Zr/Rb reveal magma mixing role in the evolution of Neshveh volcanic rocks. Considering the above facts, we can conclude that magma mixing and magmatic differentiation were the important processes in formation of the Neshveh volcanic rocks. As well as, the incorporation of new magmatic pulse(s) with differentiation magma is the most effective mechanism for the evolution of volcanic rocks from the study area.