The Geological Features of Shizigou Ophiolites in Qimantage Area

The Shizigou ophilite occurs in the western of East Kunlun,that is the eastern of the suture zone in Qimantage.Its L-RRE elements have weakly depleted features,with a gradual increase of the total of REE from ultra-basic rocks to basic rocks and basic volcanic rocks,which belong to MORB and the whole rock chemical compositions of which are consistent with low-Ktholeiite of the MORB.They all inherit the characteristic of the source of the mantle with the same distribution patterns,and their REE show a characteristic of basic volcanic rocks and back-arc basin basalts.The ratio of the ε_Nd (t) shows the source of basalts is from D-mantle,and the overall geochemical features suggest the main composition feature of N-MORB with the characteristic of E-MORB at the same time.They formed at the subduction-related environment of the back-arc basin at Late Ordovician and experienced more than three superposition and transformation of the tectonic deformation and the metamorphism and finally transported to the surface at Early-Silurian.