LITHODEMIC UNITS OF THE FUSHUI BASIC COMPLEX IN THE NORTH QINLING MOUNTAINS AND ITS MAGMATIC EVOLUTION

The Neoproterozoic Fushui complex is located on the north side of the Shangnan Danfeng fault zone in the North Qinling. Through 1∶50 000 regional geological mapping, the complex is divided in ascending order into five lithodemic units: the Jinpen medium fine grained meta pyroxenite, Heitangou fine grained dark meta grabbro, Macaogou medium grained meta grabbro, Dingjiagou medium grained meta grabbro diorite and Baliwan medium coarse grained meta amphibole biotite monzonite syenite. These units are called by a joint name the Fushui sequence. The intrusive sequence of the various units is determined on the basis of the contact relationships and features of inclusions contained in rocks. The various units form a relatively complete magmatic evolutionary sequence and have distinct comagmatic evolutionary features in terms of the rock composition, petrochemical composition and trace element and rare earth element compositions. The complex was formed in the active continental margin island arc tectonic setting.