Variabilities and enrichment mechanisms of the dispersed elements in marine Fe–Mn deposits from the Pacific Ocean

•A systematic study on “dispersed elements”: Ga, Ge, Se, Cd, In, Te, Re and Tl in marine Fe-Mn deposits.•Compared with the Earth’s crust and the pelagic clay, the marine Fe–Mn deposits are highly enriched in Te, Tl, Se and Cd.•Se, Cd, Te and Tl concentrations in marine Fe–Mn deposits show some specific variations on global, regional, intra crust/nodule scales and different water depth.•Under conditions of hydrogenetic and hydrogenetic-diagenetic, Cd, Se, Te and Tl are incorporated in marine Fe-Mn deposits mainly by adsorption onto the Mn-oxides or/and Fe oxyhydroxides.•The processes of coupled redox and coprecipitation on Fe-Mn(oxyhydr)oxides could generate Te enrichment.