Nano-Mineralogy and Mineralization of the Polymetallic Nodules from the Interbasin of Seamounts, the Western Pacific Ocean

Abstract

Ferromanganese (Fe-Mn) polymetallic nodules are significant marine mineral resources containing various metal elements of substantial economic and scientific research value. Previous studies have primarily focused on the mineralogy and geochemistry of the nodules, while research on their nano-mineralogy is still lacking. In this study, we conducted scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) porous structure gas adsorption/desorption, and specific surface area analysis to examine the nano-mineralogy and mineralization of the polymetallic nodules from the interbasin of seamounts in the western Pacific Ocean (IBSWP). The results indicate that the growth profiles of the IBSWP polymetallic nodules exhibit microstructural features such as laminated, stromatolithic, columnar, and mottled structures. The mineral compositions are primarily composed of Fe-Mn minerals and detritus, including quartz; minerals from the feldspar group; and minerals from the clay group. The Fe-Mn phase minerals are relatively poorly crystallized. The Mn-phase minerals contain vernadite and small amounts of todorokite, buserite, and birnessite, while the Fe-phase minerals are mainly comprised of amorphous FeOOH. The main ore-forming minerals consist of nano-minerals, and the nanostructures of the polymetallic nodules endow them with unusually large specific surface areas and pore volumes, resulting in strong adsorption properties. The unique nano-properties and surface/interface adsorption effects of Fe-Mn minerals play a crucial role in controlling the enrichment of ore-forming elements.