Compositional variation and genesis of ferromanganese crusts in the central segment of Emperor Chain Guyots, Pacific Ocean

We studied the morphology, mineral composition, and chemical composition of ferromanganese (Fe-Mn) crusts from the central segment of the Emperor Chain Guyots (Jingū, Ōjin, and Nintoku). These Fe-Mn crusts are characterized by a 10 Å manganese phase, amalgamated with vernadite (δ-MnO₂), exhibiting significant variation in their mineralogical composition when compared to those associated with other Pacific seamounts. Notably, these Co-rich crusts are highly enriched in lead, with concentrations reaching up to 5303 ppm and an average of 3029 ppm. They show elevated levels of molybdenum (up to 1429 ppm, with an average of 879 ppm) and tungsten (up to 287 ppm), approximately double those found in other global ocean regions. A remarkable enrichment of rare earth elements and yttrium (REY) was also observed, with a cumulative level of 5431 ppm. The concentrations of manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), and nickel (Ni), in combination with the REY distribution patterns, suggest that these Fe-Mn crusts are primarily of hydrogenic origin. Nonetheless, there is evidence of a hydrothermal contribution, particularly linked to the Late Pliocene volcanic rejuvenation phase (3.97–3.21 million years ago) of the Pacific Plate.