The　Jiangnan　orogenic　belt　(JOB)　has　been　interpreted　as　a　suture　zone　between　the　Yangtze　craton　and　Cathaysian　terranes　in　South　China.　The　Neoproterozoic　mafic-ultramafic　rocks　are　extensively　exposed　in　the　western　JOB,　providing　an　ideal　opportunity　to　study　the　Neoproterozoic　assembly　and　tectonic　evolution　of　South　China.　We　present　integrated　field　and　geochemical　studies　including　LA-ICP-MS　zircon　U-Pb　dating,　and　whole-rock　major　and　trace　element　and　Sm-Nd　isotope　analyses　of　the　Neoproterozoic　mafic-ultramafic　rocks　exposed　in　the　northern　Guangxi　Province,　South　China.　Geochronological　results　show　that　the　magmatic　events　took　place　in　two　distinct　periods:　the　early　Neoproterozoic　(861-834　Ma)　and　the　late　Neoproterozoic　(770-750　Ma).　Early　Neoproterozoic　ultramafic　rocks　of　the　Sibao　Group　have　positive　epsilon(Nd)(t)　values　(+　2.7　to　+　6.6)　whereas　mafic　rocks　exhibit　negative　epsilon(Nd)(t)　values　(-5.8　to　-0.9).　The　basaltic　rocks　show　TiO2　contents　of　0.62-0.69　wt.%　and　Mg-number　of　59-65,　and　also　display　an　enrichment　of　light　rare　earth　elements　(LREEs)　and　pronounced　negative　Nb,　Ta　and　Ti　anomalies　on　chondrite-　and　primitive　niantle-normalized　diagrams,　consistent　with　subduction-related　geochemical　signatures.　Late　Neoproterozoic　rocks　of　the　Danzhou　Group　show　epsilon(Nd)(t)　values　(-123　to　+3.19)　for　both　ultramafic　and　mafic　rocks.　The　basaltic　rocks　have　TiO2　contents　of　1.01-1.33　wt.%　and　Mg-number　of　57-60,　and　have　a　mixture　of　MORB-　and　arc-like　geochemical　affinities,　inferred　to　have　formed　in　an　extensional　arc　environment.　Geochemical　signatures　suggest　that　all　rock　types　in　this　study　were　derived　from　subarc　mantle　wedge　sources　and　underwent　various　degrees　of　crustal　contamination.　Thus,　we　suggest　that　subduction　may　have　continued　to　ca.　750　Ma　in　the　western　JOB,　implying　that　the　amalgamation　event　between　the　Yangtze　craton　and　Cathaysian　terranes　was　later　than　750　Ma.　(C)　2015　International　Association　for　Gondwana　Research.　Published　by　Elsevier　B.V.　All　rights　reserved.