Mineralogy, geochemistry and genesis of the polymetallic crusts and nodules from the South China Sea

•SCS crusts/nodules are mainly hydrogenetic, and grew faster than most hydrogenetic Fe–Mn deposits worldwide.•The SCS crusts/nodules show typical marginal sea characteristics.•The SCS crusts/nodules have potentially economic concentrations of REY, Pt, Co, Li, Ba, Pb, Sr, Te and Tl.•δ56/54Fe (−0.248‰ to −0.811‰) are similar to the Atlantic crusts, suggesting a terrigenous Fe sources.•187Os/188Os ratios (0.953–1.052; avg. 1.003) are close to the modern ocean.