Abstract: Some outcrops of amphibolites occur as tectonic slices and lenses in the Niujingshan area,and play an important role in deciphering the tectonic evolution of the Changning-Menglian Tethyan ocean in southwestern China. The petrological,whole-rock geochemical and zircon U-Pb and Hf isotopic data for the amphibolites from the Niujingshan area in the Changning-Menglian suture zone are reported in details in the present paper. The cathodoluminescence (CL) images reveal that the zircons extracted from the amphibolites are of magmatic origin. The LA-ICP-MS zircon U-Pb dating results for the amphibolites yield a weighted mean ²⁰⁶Pb/²³⁸U age of 272±1.2 Ma (MSWD=1.1,n=21),representing crystallization age of the protoliths of the amphibolites. The geochemical analyses show that the amphibolites have SiO₂ contents ranging from 51.83% to 52.6%,relatively low total alkali (Na₂O+K₂O)contents ranging from 3.33% to 4.16%,and high Na₂O/K₂O ratios of 5.8-19.8. Major elements show the low-K tholeiitic magma series of the amphibolites,while the trace elements show the typical features of normal mid-oceanic ridge basalts (N-MORB)of the amphibolites. The protolith restoration study for the amphibolites indicates that the parent rocks of the amphibolites are gabbro with N-MORB affinity. The initial Hf isotope ratios (¹⁷⁶Hf/¹⁷⁷Hf)_i of the zircons extracted from the amphibolites range from 0.282906 to 0.282956, with corresponding ε_HF(t)values of 10.7-12.5. These zircons have depleted mantle Hf model ages (t_DMI)of 416-499 Ma,with an average of 466 Ma,obviously older than the timing (272 Ma)of the zircon growth. It is suggested from the whole-rock geochemical signatures and zircon U-Pb and Hf isotopic data that the Changning-Menglian Tethyan ocean has a long-term depleted mantle with the ages of 416-499 Ma during the Late Palaeozoic (272 Ma). In the light of the comprehensive study mentioned above and the presence of the Early Palaeozoic oceanic crust remnants and oceanic subduction-induced high-Mg adakites,we propose that the Changning-Menglian ocean is a Proto- and Palaeo-Tethyan ocean with a long and complicated evolutionary history,and the mid-oceanic ridge spreading once took place and resulted in the formation of N-MORB oceanic crust during the Late Palaeozoic (272 Ma).