Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Geochemical study of “Arash Syenite” (Central Iran) with Special Emphasis on Alkali Metasomatism

Document Type : Original Research Paper

Authors
Mohammad Vali Valizadeh 1
Arash Sharifi 2
1 Department of Geology, Faculty of Science, Tehran University, Tehran , Iran
2 Geology Division, Iranian National Center for Oceanography (INCO), Tehran, Iran
Abstract
        Arash Syenite is located in central Iran and in Bafq metallogenic province, and has intruded into the Precambrian-Cambrian volcanic-sedimentary sequences. Size and distribution of minerals are not uniform in all parts of the body and vary from chilled margins to the central part of the pluton. Effects of tectonic movements, existence of uncommon textures in plagioclase crystals and the appearance of metasomatic textures are the main evidence for metasomatism. Study of elemental concentration deduced from mass balance calculation reveals the effects of alkaline metasomatism in Arash Syenite. Gain in K2O (and Rb) and Al2O3 with parallel losses in Fe2O3, CaO, Na2O, Ba and Sr are shown. Relative increase in Nb and Zr are due to leaching of mobile cations in this pluton.
Decrease in Zr and Nb with parallel increase in SiO2, which is one of the most identical factors for the calc-alkaline differentiation, is remarkable in Arash Syenite. There is a clear change in Y, Th and Nb relative to Zr in this pluton and based on the constant ratio of Zr/Nb, the role of contamination and assimilation of country rock is insignificant in the petrogenesis of this pluton. Negative anomaly for Nb and TiO2 suggest a subduction-related origin for the Arash Syenite.
Keywords
Alkali metasomatism
Central Iran
Syenite
Esfordi

Subjects

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Scientific Quarterly Journal of Geosciences
Volume 14, Issue 53
Autumn 2004, Vol. 14, No. 53
Autumn 2004
Pages 2-15