The Lengshuiqing magmatic Ni-Cu ore deposit and the Gaojiacun intrusion, located in the western margin of the Yangtze craton in China, was emplaced into the early Neoproterozoic metamorphosed volcanic-sedimentary rocks, granites and diorites. The Lengshuiqing deposit is hosted in four small mid-Neoproterozoic mafic-ultramafic intrusions. It is the largest Neoproterozoic magmatic Ni-Cu ore deposit in the western margin of the Yangtze craton in China, with 210 thousand tons of metal nickel. Of which the 101 intrusion contain 160 thousand tons of metal nickel. The intrusions are dominated by lherzolite, olivine websterite, websterite and gabbro, with sulfide mineralization associated with ultramafic rocks in the lower parts of the intrusions. The Gaojiacun intrusion is the largest Neoproterozoic mafic-ultramafic intrusions in the western margin of the Yangtze craton. It can be divided into the outer zone and inner zone. The outer zone is mainly characterized by olivine-free mafic-intermediate rocks, including gabbro, hornblende gabbro, and diorite. The inner zone is dominated by olivine-bearing mafic-ultramafic rocks, including dunite, lherzolite, and troctolite, other than a few clinopyroxenite. Five layers of sulfide mineralization with 2-4 meter and 0.6 to 1.3 wt % Ni grade in the Gaojiacun ultramafic portion were discovered in the latest drill cores. The samples used in this study were collected from drill cores of the Lengshuiqing 101 intrusion (ZK37801, ZK37802) and Gaojiacun inner zone (ZK3902) and outer zone (field outcrop). We report additional data such as chronology, mineralogy, systematic mineral compositions (Cr-spinel, olivine and clinopyroxene), new PGE data, and complementary whole-rock chemical and Sr-Nd-S-Os isotopic compositions. These data, together with geological constraints, are used to evaluate the competing geodynamic models (subduction versus mantle plume) that have been proposed for the associated basaltic magmatism, as well as the fundamental controls on the genesis of this type of magmatic Ni-Cu ore deposit. The implications of the results from this study for Ni exploration at both global and regional scales are assessed. Finally, combined with the regional geological background, the tectonic setting of the western margin of the Yangtze in the Neoproterozoic is also discussed.The ages of the host intrusions of the Lengshuiqing deposit were dated at ~820 Ma. In the paper, the Gaojiacun outer zone is determined using a SIMS, dating at 824 &plusmn; 6 Ma (hornblende gabbro, GJC1603) The most forsterite contents of olivine crystals in the Lengshuiqing and Gaojiacun intrusions are 86 mol% and 85 mol%, respectively, indicating that their parental magma experienced moderate degrees of fractional crystallization. Olivine crystals in the intrusions are depleted in Ca (<1000 ppm), a common feature for arc-type mafic-ultramafic intrusions worldwide. Moreover, clinopyroxene and Cr-spinel in the Lengshuiqing and Gaojiacun intrusions are remarkably similar to those in arc-type olivine-clinopyroxene cumulates elsewhere in the world, whereas significantly different from the rift-related Jinchuan intrusion. Based on the Fe-Ni exchange coefficient between olivine and sulfide liquid, the estimated oxidation state for the Lengshuiqing deposit and Gaojiacun intrusion are close to QFM + 1. Whole rock samples from these intrusions are all characterized by moderate light REE enrichments relative to heavy REE, moderate to significant degrees of negative Nb-Ta anomalies. The Lengshuiqing deposit has positive &epsilon;Nd(t) from +1.1 to +5.8, and low (87Sr/86Sr)i from 0.7038 to 0.7050. The Gaojiacun intrusion has positive &epsilon;Nd(t) from +1.3 to +4.5, and low (87Sr/86Sr)i from 0.7044 to 0.7055. The isotope data indicate that the parental magma for these intrusions experienced only minor degrees of crustal contamination that cannot fully account for the observed negative Nb-Ta anomalies in the rocks. The data imply that the parental magmas were already depleted in Nb and Ta prior to crustal contamination. Taken together, the data support the view of an arc setting for the Lengshuiqing and Gaojiacun mafic-ultramafic intrusions. Like most other arc-type magmatic sulfide deposits, the PGE tenors of the Lengshuiqing deposit are very low. The estimated initial contents of PGEs in the parental magma are 0.25 ppb Pd, 0.006 ppb Ir for the Lengshuiqing and 0.12 ppb Pd, 0.02 ppb Ir for the Gaojiacun, which are two orders of magnitude lower than those in PGE undepleted picrites of continental flood basalt provinces such as the Emeishan and Siberian traps. Their PGE tenors are mainly controlled by the variable R-factors and moderate degrees of sulfide liquid fractionation on cooling. 34S, &gamma;Os(t) and S/Se of the sulfide ores in Lengshuiqing deposit are from -4.0 to +1.3 &permil;, from 115 to 320, and from 4,800 to 12,500, respectively. 34S and S/Se of the sulfide ores in Gaojiacun intrusion are +2.3 to +3.3 &permil;, and from 4,100 to 5,100, respectively. These values are significantly different from typical mantle values, and indicate that addition of external sulfur played a major role in triggering sulfide saturation in the magma. According to the MELTS simulation and calculation for the S content at sulfide saturation in the fractionated magma, alone the fractional crystallization process cannot result in sulfide saturation in magma. Therefore, the addition of crustal sulfur played the most important role in sulfide saturation. Rounded sulfide inclusions in some olivines and even spinels indicate that sulfide saturation could take place before/during olivine and spinel crystallization.Together with the rock composition, spatiotemporal distribution and geochemical characteristics of all reported Neoproterozoic magmatic rocks in the western margin of the Yangtze, we believe that these rocks (>820 Ma) are more in line with the genetic model of the island arc magma system, whereas obviously do not conform to the genetic model of the mantle plume. Considering the ore-forming factors of the magmatic Cu-Ni sulphide deposit, we believe that the Gaojiacun intrusion has the possibility of hosting a large-scale arc-type magmatic sulfide deposit at depth.