Geochemical investigation of Pt, Pd, Rh, Ru and Au in cobalt-rich deposits from the Tuamotu Plateau (French Polynesia)

Pt, Pd, Rh, Ru and Au contents were determined in 35 samples of hydrogenous ferromanganese crusts and nodules from the Tuamotu Plateau (French Polynesia), collected during the Nodco II cruise undertaken by IFREMER during March 1987. These samples are characterized by high Pt and Rh contents. A statistical analysis including PGE and data on Mn, Fe, Ni, Co and Cu contents does not reveal significant correlations between the elements. Although meteoritical origin of PGE remains possible, the process of fractionation and deposition is probably hydrogenetic as confirmed by normalization diagrams to chondrite C1. This point of view is supported by the determination of some partition coefficients of PGE between the oxidized phase and the aqueous medium. The deposition mechanism is discussed.