<p>Seafloor massive sulfide (SMS) deposits in back-arc basins provide key analogues for volcanogenic massive sulfide systems and are increasingly considered prospective targets for seafloor mineral exploration. Along the Central Spreading Ridge (CSR) of the North Fiji Basin, hydrothermal venting and SMS mineralization occur in adjacent ridge segments that differ markedly in axial morphology and fault structure, implying contrasting accretionary styles and permeability structure. Here, we integrate ship-based multibeam bathymetry, near-bottom microbathymetry and imagery by remotely operated vehicle, and bulk sulfide geochemistry of samples from the CSR N15 segment (KF2) and the CSR NS segment (KF3) to evaluate segment-scale tectono-magmatic controls on vent distribution, chimney/mound architecture, and ore composition. KF2 is characterized by a graben-bounded axial valley and caldera-related structures that host dense clusters of predominantly inactive chimneys and large collapse mounds. In contrast, KF3 lacks a pronounced axial valley and is dominated by constructional volcanic ridges and flood-basalt plains, where fewer but proportionally more active chimneys occur as isolated edifices localized along minor, near-vertical faults. Sulfide bulk compositions show negligible Pb, consistent with formation in a sediment-free ridge setting. Cu–Zn systematics and ore mineralogy indicate that Cu-rich, chalcopyrite-bearing assemblages are more prevalent in KF2, whereas Zn-rich, sphalerite-dominant assemblages prevail in KF3, with chalcopyrite largely restricted to conduit linings in a limited subset of active chimneys. These results show that segment-scale differences in magma supply, fault-controlled permeability, and hydrothermal maturity modulate vent longevity and metal partitioning along the CSR.</p>