We reported zircon SIMS U-Pb ages, the whole rock geochemistry of the Shuanglang gabbro located in Longsheng County, North Guangxi from the western Jiangnan Orogen in this manuscript, to decipher their petrogenesis and tectonic setting. Samples comprised clinopyroxene and plagioclase with minor K-feldspar and Fe-Ti oxides. The Shuanglang gabbro with a zircon SIMS U-Pb age of 782±9 Ma. The bulk-rock have SiO₂ (50.05%~51.85%), Al₂O₃ (14.53%~15.42%) and CaO (6.95%~7.19%) contents, and MgO (8.97%~11.33%) and total FeO (10.63%~11.92%) contents. The samples display ocean island basalt (OIB)-like geochemical signatures, with the enrichment of light rare earth elements (LREE) and large-ion lithophile elements (LILE) relative to heavy rare earth elements (HREE), with insignificantly negative Nb, Ta anomalies, and have high (⁸⁷Sr/⁸⁶Sr)_i (0.709 990~0.711 788) and negative εNd(t) (-2.4~-1.4) values resulted from the upper crust contamination. They are suggested to have originated from a small degree (3%~4%) of partial melting of the upwelling asthenospheric man-tle in an extensional setting of the garnet stability field. Based on the spatial distribution of the mafic-ultramafic rocks during 780~750 Ma in the western Jiangnan Orogen reported in both this study and previous publications and comprehensive analyses of them, we indicate that the subducted slab break-off triggered the partial melting of upwelling asthenosphere, which resulted into the formation of the OIB-like mafic-ultramafic rocks during 780~750 Ma in the western Jiangnan Orogen.