The East Kunlun Orogen is located in the northern part of the Tibetan Plateau and has received significant attention in tracing the evolution of Paleo-Tethys Ocean. In this study, we present U-Pb zircon geochronology, geochemistry and Sr-Nd isotopic data on the Kengdenongshe tholeiitic gabbro in the eastern part of the orogen. The gabbro is characterised by high and variable MgO and Fe 2 O 3 , as well as low K 2 O and TiO 2 contents, typical of low-K tholeiitic series. The rock shows enrichment in large-ion lithophile elements, depletion in high field strength elements, with rare earth element signature similar to that of a back-arc basin basalt. The rock displays relatively low and uniform ( 87 Sr/ 86 Sr) i ratios and high ε Nd (t) values. These geochemical and isotopic features are interpreted to represent magma derivation from partial melting of an enriched asthenospheric source. Our model envisages that the initial melting started in the garnet-facies (~4%) and continued in the spinel-facies (~6%). The geochemical and isotopic systematics of the gabbro are consistent with magma generation in a back-arc basin setting triggered by the subduction of the Paleo-Tethys Ocean. In conjunction with the data on mafic magmatic suites in the region, we trace a progressive change in source from asthenosphere to increasingly enriched mantle wedge. Our study proposes a transition in the geodynamic setting of the east Paleo-Tethys Ocean from back-arc extension during the Late Permian to continued subduction during the Late Permian and Middle Triassic.