Magmatic and metamorphic evolution of the Shotur Kuh metamorphic complex (Central Iran) |
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Authors: | Mahmoud Rahmati-Ilkhchi Shah Wali Faryad Franti?ek V Holub Jan Ko?ler Wolfgang Frank |
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Institution: | (1) Institute of Petrology and Structural Geology, Charles University in Prague, Albertov 2, 128 43 Prague, Czech Republic;(2) Geological Survey of Iran, Tehran, Iran;(3) Department of Earth Science and Centre for Geobiology, University of Bergen, Allegaten 41, 5007 Bergen, Norway;(4) Central European Argon Laboratory, Slovak Academy of Sciences, Valasška, Bratislava, Slovakia; |
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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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