Petrography,geochemistry and geodynamic environment of potassic alkaline rocks in Eslamy peninsula,northwest of Iran |
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Authors: | B Hajalilou M Moayyed Gh Hosseinzadeh |
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Institution: | 1.Department of Geology,Payame Noor University,Tabriz,Iran;2.Department of Geology,University of Tabriz,Tabriz,Iran |
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Abstract: | Eslamy peninsula, 360 km2 in area, is located in the eastern coast of Urmieh lake in the northwest of Iran. This peninsula is a complex stratovolcano
with a collapsed center, which is elevated due to later intrusions of sub-volcanic masses with trachytic to microsyenitic
composition. The composite cone consists of a sequence of leucite tephrite, tephrite, leucite basanite, basanite and related
pyroclastic rocks. Magmatic activities in the Eslamy peninsula begin with potassic alkaline to ultrapotassic and basic, silica-undersaturated
shoshonitic rocks and they are followed by intrusions of lamprophyric dykes and end with acidic magmatism including trachytic,
microsyenitic, syenitic and phonolitic domes. The original magma of the Eslamy peninsula rocks has a potassic alkaline nature
(Roman type) rich in LREE and LILE and depleted of HREE. These characteristics suggest that the origin of magma can be from
deep mantle with a garnet lherzolite composition, a low partial melting rate which has been contaminated by crustal materials
in its way up. Fractional crystallization of olivine, diopsidic clinopyroxene and leucite played an important role in the
evolution of magmas. Scrutinizing the geodynamic environment of Eslamy peninsula rocks in discrimination diagrams indicates
that these rocks must have been formed in a post-collision magmatic arc setting. |
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