Characteristics of Co-rich ferromanganese nodules and crusts sampled in French Polynesia

摘要: Abstract Co-rich ferromanganese nodules and crusts were sampled at water depths of about 1000 m on the southern flanks Tuamotu Archipelago in French Polynesia. Crusts developed a hard sedimentary substrate form continuous encrustation, 2.5 cm average thickness, plateaus slopes seamounts. Nodule clusters occur within tops plateaus. A detailed study structure, mineralogy geochemistry established following: (1) nodule crust cores are made up phosphatized breccia with brecciated biogenous limestone elements, which reflects gradual subsidence archipelago since middle Eocene; (2) two discontinuous growth episodes oxide zones separated by deposition carbonate-apatite; (3) Co increases according to morphological layers, from inner layer (0.5% Co) peripheral where concentrations reach 2%; (4) enrichment appears be related Oxygen Minimum Layer. The characteristics samples Polynesia similar those other regions North Pacific. should considered as potential metal resource, similarly Hawaiian-Emperor Line Islands-Mid-Pacific Mountains system.