Abstract
Metamorphic basement rocks, that are exposed beneath the very low-grade to unmetamorphosed Upper Jurassic-Eocene formations north of the Torud fault zone within the Great Kavir Block, were investigated to elucidate the origin of their protoliths and the pressure and temperature conditions of metamorphism. The basement, previously assumed as a pre-Cambrian metamorphic complex, is mostly formed by amphibolite-facies orthogneisses (tonalite, granodiorite, and granite) with amphibolites and small amounts of metasediment-micaschists. Major- and trace-element geochemistry in combination with U–Pb age dating of zircon showed that the protoliths formed during Late Neoproterozoic continental arc magmatism that has also been identified in other tectonic blocks of Central Iran. In addition to quartz, feldspar(s), micas in orthogneisses, and amphibole + plagioclase in amphibolite, all rocks may contain garnet that shows prograde zoning. Kyanite was found only in some Al-rich amphibolite together with gedrite. The PT conditions of the rocks, based on conventional geothermobarometry and the pseudosection method, show a medium-pressure amphibolite-facies metamorphism. Ar–Ar age dating of muscovite reveals that this metamorphism occurred in the Middle Jurassic (166 Ma) and related to the closure of the Neotethyan basin.
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Acknowledgments
This work is a part of the PhD thesis of M. Rahmati-Ilkhchi at the Institute of Petrology and Structural Geology (Charles University in Prague) and was supported by the Geological Survey of Iran as well as by the Ministry of Education, Youth and Sports of the Czech Republic (Research Project MSM21620855). K. Schulmann (Strasbourg) is thanked for facility to obtain K–Ar age data of biotite and muscovite. Christoph Hauzenberger and Marlina A. Elburg are thanked for careful and thorough reviews of the manuscript. We also thank Ingo Braun for helpful comments and editorial responsibility.
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Rahmati-Ilkhchi, M., Faryad, S.W., Holub, F.V. et al. Magmatic and metamorphic evolution of the Shotur Kuh metamorphic complex (Central Iran). Int J Earth Sci (Geol Rundsch) 100, 45–62 (2011). https://doi.org/10.1007/s00531-009-0499-0
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DOI: https://doi.org/10.1007/s00531-009-0499-0