volcanics of Julfa: implications for tectonic evolution of northwestern Iran

The study area is located in the southwest of Julfa, northwestern Iran. The lithologic units in the Pireshagh- Gharebolagh area include various igneous and sedimentary units of Middle to Late Paleozoic. The Paleozoic units consist of basalts, clastics and limestone of Devonian as well as acidic volcanics, sandstone and limestone of Permian ages. Based on geochemical studies, the Devonian basaltic volcanism in the south of Gharebolagh displays intra-plate signatures similar to oceanic island basalts (OIB). Also, major and trace element geochemistry of acidic volcanics (rhyolite and equivalent pyroclastics) in the Pireshagh area is identical to anorogenic magmatic rocks (A-type granites). On the basis of U- Pb zircon geochronology, the rhyolitic rocks are 297.8 ± 4 Ma in age correlating with the beginning of Permian. The dating result helps to better understand the stratigraphic position of rhyolites, while the previous studies, geological maps, point to Devonian age for them. Our finding shows that the Middle to Late Paleozoic magmatics of northwestern Iran formed by two distinct extensional tectonic events of Devonian and Permian ages. Since the Central Iran and Alborz indicate the same extensional tectonic phases in Devonian and Permian so, during Middle to Late Paleozoic, northwestern Iran along with Central Iran and Alborz were parts of the Cimmerian terranes with the same geotectonic scenario.