Petrography and Geochemistry of the Tertiary volcanics of Tabas, Iran

The volcanic rocks of Shotory mountain range located in the east of Tabas town with Eocene age, are a small part of Lut volcanism and incorporate a continuous spectrum which is composed of basalt to Rhyolites. Pyroclastic rocks are often under contact of V.R and their volume is less then volcanism. Basalts are the first sign of volcanism among the volcanic rocks of the aforesaid area. According to petrographic studies, texture of volcanic rocks is mainly porphyric with vitric current, semi current and cryptocrystalline groundmass. Biotite is only dark mineral in falsic volcanic rocks (Rhyolites and Dacites) and clinopyroxene augite in andesites. Considering field oxides and REE, spider diagrams, geochemical characteristics and their much similarities with And range and west USA volcanism; volcanic rocks of shotory are dependent to calc-alkalinr rich (k) related to subduction continental zone where probably result of subduction oceanic plate between Afganistan block (Hyrmand) and Iranian block (LUT) under Iranian block in upper cretaceous and together with forming ophiolite melanges of east Iran. The volcanic rocks in the above-mentioned area have been generated at trace definition and cristallization basaltic magma together with repeated injection of new melt in magma chamber and a little assimilation in source.