A number of metamorphosed mafic rocks occurred within the Paleozoic strata in the Chenxing and Bangxi regions at the northern side of the Changjiang-Qionghai Fault in Central Hainan Island. These metamorphosed mafic rocks are tholeiites in chemistry. They are characterized by extreme depletion of Th, Nb, Ta and LREEs, resembling the depleted N-type mid-ocean ridge basalts (MORE). Field relations suggest that the protolith of the metamorphosed mafic rocks were likely formed in Paleozoic. These metamorphosed mafic rocks with N-type MORB geochemical features were probably the remnants of the Paleo-Tethys oceanic crust.