Petrography and petrogenesis of igneous rocks attributed to Proterozoic within Ahangaran- Qayen area

The study area is located in Southern Khorasan Province, about 90 Km southeast of Qayen and 120 Km northeast of Birjand. The oldest rocks in this area, which are attributed to Proterozoic, consist of volcanic rocks and intrusive bodies with no sign of thermal metamorphic in volcanic rocks. Volcanic rocks include basalt, trachy-andesite and dacite, which have been metamorphosed to green schist facies. The compositions of the intrusive bodies attributed to Proterozoic ranges are diorite to granite. The magmatic nature of old volcanic rocks is mostly tholeiitic as these rocks in the area show a tholeiitic trend, and from thetectonomagmatic environment they belong to the tholeiitic oceanic island arcs. The magmatic nature of these intrusive bodies is sub-alkaline and the magma is of calc-alkaline type, therefore their tectonic settings belong to continental arc granite. These rocks in the studied area formed within active continental margin as a result of subduction phenomenon.