Mineralogy, Geochemistry and radiometric age of mafic dikes in Delbar metamorphic complex (southeast of shahrood)

Delbar metamorphic complex composed of schists, amphibolites and gneisses with migmatitic views belong to Neoprotrozoiec (Precambrian) is located in southeast of Shahrood. Debar metamorphic complex crosscut by at least three series of mafic dikes, with different ages (Precambrian, Jurassic and Tertiary). Jurassic dikes intruded in Precambrian metamorphic complex and upper Triassic - lower Jurassic metamorphosed detrital sedimentary rocks (equivalent to the Shemshak Formation), but not continue in the middle Jurassic sandy limestone and lower Cretaceous (Neocomian) limestones. Amphiboles of the mafic dikes are Edenite type Ca group amphiboles. Barometry based on the Al+3 content of the amphiboles indicated 4-5 Kbar presuers equivalent to the final equilibrium of amphiboles, illustrated 14-15 Km depths to the implacement of the studied dikes in the crust. U-Pb Age dating on apatites from the mafic dikes, indicated 152± 35 Ma age which completely confirmed field and stratigraphic relationships. The mafic dikes have alkaline to calc-alkaline nature based on the geochemical characteristics. The parental magma produced from 15% partial melting of a spinel lherzolite mantle source. These mafic dikes generated in a back arc extentional setting related to the continental crust extentions of central Iran caused by Neotethys plate subduction under it. This event is related to the magmatism of early Cimmerian orogeny.