University of Isfahan Petrological Journal 2228-5210 9 1 2018 05 22 Mineral chemistry, thermobarometry and tectonomagmatic setting of Late-Cretaceous volcanic rocks from the Kojid area (south of Lahijan, northern Alborz) Mineral chemistry, thermobarometry and tectonomagmatic setting of Late-Cretaceous volcanic rocks from the Kojid area (south of Lahijan, northern Alborz) 133 164 22517 10.22108/ijp.2017.104651.1033 FA Morteza Delavari Department of Geochemistry, Faculty of Earth Sciences, University of Kharazmi, Tehran, Iran Razieh Moradi Department of Geochemistry, Faculty of Earth Sciences, University of Kharazmi, Tehran, Iran Amir Ali Tabbakh Shabani Department of Geochemistry, Faculty of Earth Sciences, University of Kharazmi, Tehran, Iran Journal Article 2017 06 09 The volcanic rocks of Kojid area (south of Lahijan) crop out in northern Alborz. They show mainly pillow structure with numerous cross-cutting dykes. Based on lithostratigraphic relationships and interpillow pelagic limestones, the volcanics are Late Cretaceous in age. The volcanics of Kojid area are predominantly basic in composition (olivine basalt and basalt) and minor more evolved suites such as trachyandesite and dacite. Olivine phenocrysts display forsterite (Fo) content of 63 to 83%. The phenocrystic and interstitial clinopyroxene crystals are augite to diopside in composition, with Na2O, Al2O3 and TiO2 contents of 0.24- 0.68, 2.3-6.53 and 1-5.1 wt.%, respectively. Furthermore, plagioclase is labradorite (An%= 51-68). The results of various geothermobarometric methods of clinopyroxene, plagioclase and olivine indicate good correlation with each other. Different thermometric calculations yielded temperatures in the range of 1100 to 1250 °C which are compatible with temperatures of basic melts. Moreover, clinopyroxene and plagioclase barometry of the phenocrysts (4 to 8 Kb) and interstitial phases ( The volcanic rocks of Kojid area (south of Lahijan) crop out in northern Alborz. They show mainly pillow structure with numerous cross-cutting dykes. Based on lithostratigraphic relationships and interpillow pelagic limestones, the volcanics are Late Cretaceous in age. The volcanics of Kojid area are predominantly basic in composition (olivine basalt and basalt) and minor more evolved suites such as trachyandesite and dacite. Olivine phenocrysts display forsterite (Fo) content of 63 to 83%. The phenocrystic and interstitial clinopyroxene crystals are augite to diopside in composition, with Na2O, Al2O3 and TiO2 contents of 0.24- 0.68, 2.3-6.53 and 1-5.1 wt.%, respectively. Furthermore, plagioclase is labradorite (An%= 51-68). The results of various geothermobarometric methods of clinopyroxene, plagioclase and olivine indicate good correlation with each other. Different thermometric calculations yielded temperatures in the range of 1100 to 1250 °C which are compatible with temperatures of basic melts. Moreover, clinopyroxene and plagioclase barometry of the phenocrysts (4 to 8 Kb) and interstitial phases ( https://ijp.ui.ac.ir/article_22517_5ee35370da8f66a3caa3af458c489939.pdf