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

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