Sedigheh Ehsani, Nasrin Bayrami Tosanlo
Islamic Azad University, North Tehran branch, Faculty of sciences, Department of geology
Department of Geology science and Research brench ,Islamic Azad University,Tehran. Iran
Key words: Volcanic rocks, Petrology, Geochemistry, Rift, Alborz zone, South Langrood, Iran.
Under studied region is located in Gilan province, in south of Langrood city, Amlash town, among 50° 00′ and 50° 30′ Eastern longitudes and 37° 00′ and 37° 15′ Northern latitudes. Its area is about 450 km2. According to classification of Iran structural zones, this region is located in Alborz-Azarbaijan zones (Nabavi, 1977). In this region the upper part is formed of an Ophiolite Complexes that its uplifting time is upper Cretaceous. Constitutive rocks of this part are rocks of old ocean crust and totally consist of carbonate cretaceous sedimentary rocks, pillow basalts (include basalt, basaltic andesite, andesite and trachyte terms), delorite and gabbro dikes. According to various geochemical and petrological diagrams, the rocks in the study area are tholeiitic, calc-alkaline, calc-alkaline rich in potassium and shoshonitic (two samples) and the degree saturation of alumina located in the range of metaluminous. Magmatic differentiation can also be inferred by crystallization, metasomatism and magma contamination in the crust. In the rift basalts. The differences in the detection of tectonic environment can accrue to alteration and pollution basaltic magma with continental crust, so in total it can be said the conclusions of the tectonic setting is not possible at present And the integration of research done on the remnants of oceanic crust in the Gilan province to reach the conclusion that there will be relatively strong.
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