Variete des environements geologiques et relations avec les depots ferromanganesiferes de l'ocean

During the world tour of R/V Jean Charcot , 2 types of polymetalic deposits have been investigated: the cobalt-rich crusts in the Tuamotu Archipelago (French Polynesia) and the manganese nodules in the Clarion-Clipperton Fracture Zone. In the South Pacific Ocean, a genetic model of site bearing cobalt-rich crusts has been identified: the polymetallic deposits are located at a 1,000 m water depth on a subsident fossil atoll built on a volcanic substrate. In the North Pacific Ocean, a 2 months cruise has been conducted on the basis of preexisting data (seabeam, bottom photographs, nodules and sediment sampling). Three types of geological environment have been characterized: a sedimentary plateau, an area particularly representative of the abyssals hills province and an area characterized by seamounts.