Geochemistry and petrogenesis of Givshad volcanic and subvolcanic rocks (southwest of Birjand, east of Iran)

The study area is located 41 Km Southwest of Birjand, in the northern part of Sistan suture zone. An Eocene dioritic subvolcanic body together with andesites and basaltic andesites have intruded into the paleogene shales and sandstones. The main textures in these rocks are porphyric with microgranular groundmass, porphyric and glomeroporphyritic. Plagioclase (oligoclase-andesine) and amphibole (green hornblende) are the main phenocrysts. Biotite, clinopyroxene and rare olivine are the remaining minerals of these rocks. The negative anomaly in high field strength elements (HFSE) such as Nb and Ti in these rocks point to the geochemical characteristic of magmatic arcs. High ratio of LREE/HREE, Sr/Y (Ave. 44.33), La/Yb (Ave. 12.48), the amount of SiO2 and the absence of Eu negative anomaly show that these rocks are similar to adakites. On the base of obtained data, the magmatism can be the result of a post collision process in a subduction regime originated from an eclogite source.