Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Radiometric Age of Mafic Parts and Metamorphic Hosts of Sikhoran Ultramafic-Mafic Complex, Southeastern Iran

Document Type : Original Research Paper

Authors
Habibollah Ghasemi 1
Mosayeb Sabzehei 2
Thierry Juteau 3
Herve Bellon 3
Mohammadhashem Emami 4
1 Department of Geology, Faculty of Sciences, Shahrood University, Shahrood, Iran
2 Geological Survey of Iran, Research Institute for Earth Sciences, Tehran, Iran
3 Universite de Bretagne Occidentale, Brest, France
4 Geological Survey of Iran
Abstract
Sikhoran Ultramafic-Mafic Complex, in southeastern Iran, has intruded into the Palaeozoic metamorphic rocks  and is overlain by Mesozoic colored mélanges with fault boundary. The age of   the complex and  other similar complexes have Stratigraphically been supposed to be Palaeozoic. Detailed field and laboratory  studies particularly, isotope geochemistry, not only revealed the age of different parts of the complex, but more significantley  also showed  its  polygenetic nature.
     Radiometric age determinations by K-Ar method on minerals and whole rocks of different parts of the complex show 305±7 Ma for biotite of host Palaeozoic gneiss, 330±8 Ma  for muscovite of anatectic granite intrusions in host Palaeozoic gneiss, 325±17 Ma  for amphibole of host Palaeozoic amphibolites (Middle-Late Carboniferous), 250-280 Ma for amphibole of  gabbro-pegmatoid dykes cutting the ultramafic-mafic cumulates (Permian), 184-220 Ma for amphibole and plagioclase of some gabbro-pegmatoid dykes and basic migmatites resulted form amphibolite anatexis in the contact of isotropic gabbros with Paleozoic metamorphic rocks of host amphibolites (Middle-Late Triassic, the age of  isotropic gabbro emplacement), 81-160 Ma for  whole rock samples of diabasic dykes (Middle Jurassic-Upper Cretaceous) and finally 81±2 Ma  for phengitic muscovite of Ashin colored mélange mica schists.
Keywords
Sikhoran
Ultramafic
Mafic
-Anatectic
Carboniferous
Permian Kumulate
Pegmatoid
Isotrop
Phengite
Ashin

Subjects

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Scientific Quarterly Journal of Geosciences
Volume 13, 51-52
Spring & Summer 2004, Vol. 13, No. 51-52
Summer 2004
Pages 58-67