Field geological investigation along two routes of Rutog-Shiquanhe and Duobuza-Gertse across the Bangong Lake suture was carried out. Among the samples collected, two mafic dykes of gabbro and diabase from the Rutog ophiolite belt display flatten chondrite-normalized rare earth element patterns, typical of oceanic-ridge basalt. Their zircon U-Pb ages of 181. 9±2. 6 Ma (MSWD=11. 5) and 184. 4±4. 4 Ma (MSWD=2. 2) dated by LAICPMS technique indicate that the Bangong Lake middle Tethys oceanic basin was opened during the Late Early-Jurassic Epoch. Meanwhile, olivine diabase samples collected from the Shiquianhe-Gertse ophiolite belt have high K2O (1.49%-1.56%) and Al2O3 (14.76%-15.21%) contents with high Fe2O3/FeO ratios (1.73-2.49), and are rich in large ion lithophile elements (Rb, Ba, Th, Sr) and light rare earth elements (LREE). They display oceanic island basalt (OIB) affinity in tectonic discrimination diagrams for mafic magmatic rock.
