Geochemical signatures and tectonic setting of the basalts from the Dongqiao region, Xizang

The Dongqiao ophiolites crop out mostly in the central part of the Bangong Lake-Nujiang suture zone, in which the ophiolites are well preserved. The trace and rare earth element analyses show that the basalts in the Dongqiao ophiolites display the noticeably LREE-enriched right-leaning REE distribution patterns. La/Yb_N=7.05-12.02. The elements Th, Nb, Ta, Zr and Hf exhibit slightly positive anomalies. The geochemical signatures cited above have disclosed that these basalts are assigned to the oceanic-island basalts(OIB), and remarkably vary from the mid-oceanic ridge basalts(MORB) and island-arc basalts(IAB). The basalts in the Dongqiao ophiolites are interpreted to be formed in the oceanic-island environments where the lithospheric uplifting took place in the oceanic plates, and represent the oceanic lithospheric remnants in the oceanic-island enviroments during the formation and development of the Bangong Lake-Nujiang oceanic basin.