Adakite magmatism within the Sabzevar ophiolite zone, NE Iran: U-Pb geochronology and Sr-Nd isotopic evidences
نویسندگان
1 Department of Petrology, School of Geosciences, Shahrood University of Technology, Shahrood,Iran
2 Department of Petrology, School of Geosciences, Shahrood University of Technology, Shahrood,Iran
3 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, P.O. Box 9825 China
4 Department of Petrology, School of Geosciences, Shahrood University of Technology, Shahrood,Iran
doi
10.22059/geope.2017.242944.648352چکیده
Numerous post-ophiolite intrusions exposed into the late Cretaceous–Paleocene Sabzevar ophiolite belt, northeast Iran. The intrusions consist of calc-alkaline intermediate to felsic rocks with metaluminous to peraluminous in nature and adakitic affinities. Based on U-Th-Pb dating on separated zircons by SHRIMP Ⅱ, the emplacement age of these rocks into the ophiolite zone is constrained to ~45 Ma. All intrusions show similar MORB –like initial Nd and Sr values of 0.512911 to 0512846 and 0.704758 to 0.703790, respectively, with positive εNd (45 Ma) values of +5.26 to +6.45 implying their cogenetic nature. These isotopic signatures combined with geochemical evidences are corresponding to parental adakitic magmas derived from wet partial melting of a garnet-amphibolite source from Sabzevar subducted oceanic lithosphere. After emplacement in the deep magma storage region (equal to 700-900 MPa), this magma evolved to intensify adakitic signatures via amphibole–dominated magma fractionation.
