Systematics of distributions of various elements between ferromanganese oxides and seawater from natural observation, thermodynamics, and structures

Abstract

Metal oxides including iron oxides, manganese oxides, and ferromanganese oxides have been frequently found at seafloor as a result of the release of dissolved iron and manganese from various sources including hydrothermal activities. These precipitates can adsorb or incorporate various elements, which can affect the behavior of the elements in marine environment. In addition, these precipitates can be resources of rare metals due to their high abundances in ferromanganese oxides. In this review, our aims are (i) to summarize distribution of various trace elements between ferromanganese oxides and seawater, (ii) to understand the distributions based on thermodynamic parameters, and (iii) to show the relationship between the distribution and structural information of the species adsorbed onto the ferromanganese oxides. For this purpose, our original data of chromate adsorption on ferrihydrite was also included. These attempts enable us to obtain systematic explanation of the solid-water distributions of various elements in marine environment, which in turn gives us clearer view on (i) the mechanism of isotopic fractionation during adsorption which is linked to the understanding of paleo environment based on the isotope geochemistry and (ii) prediction of abundances of various elements in the ferromanganese oxides that are important from the viewpoint of exploration of marine resources.