Assessment of the Mineral Resource Potential of Atlantic Ferromanganese Crusts Based on Their Growth History, Microstructure, and Texture

Abstract

Abstract:The decarbonisation of our energy supply is reliant on new technologies that are raw material intensive and will require a significant increase in the production of metals to sustain them. Ferromanganese (FeMn) crusts are seafloor precipitates, enriched in metals such as cobalt and tellurium, both of which have a predicted future demand above current production rates. In this study, we investigate the texture and composition of FeMn crusts on Tropic Seamount, a typical Atlantic guyot off the coast of western Africa, as a basis for assessing the future mineral resource potential of Atlantic Seamounts. The majority of the summit is flat and covered by FeMn crusts with average thicknesses of 3-4 cm. The crusts are characterized by two dominant textures consisting of either massive pillared growth or more chaotic, cuspate sections of FeMn oxides, with an increased proportion of detrital and organic material. The Fe, Mn, and Co contents in the FeMn oxide layers are not affected by texture. However, detrital material and bioclasts can form about 50% of cuspate areas, and the dilution effect of this entrained material considerably reduces the Fe, Mn, and Co concentrations if the bulk samples are analyzed. Whilst Tropic Seamount meets many of the prerequisites for a crust mining area, the thickness of the crusts and their average metal composition means extraction is unlikely to be viable in the near future. The ability to exploit more difficult terrains or multiple, closely spaced edifices would make economic feasibility more likely.

Measurement and modelling of deep sea sediment plumes and implications for deep sea mining

“…The sediment used for the plume experiments ( Fig. 2a) was predominantly "muddy sand" (on average 1% gravel, 84% sand and 15% silt/clay) and pelagic in origin 25 . Pterapod shells were clearly visible in the plumes created in the plume experiments (Fig.…”

“…2d) of 3 cm (on average) and up to 16 cm. Typically, the crust has bulk and dry densities of 1950 kg/m 3 and 1740 kg/m 3 , respectively 25 . The crust material Plume observations.…”

“…2). Cobalt-rich crust also occurs on the flanks as pavements and as loose blocks, associated with slope collapse 25 .…”

Bacterioplankton reveal years-long retention of Atlantic deep-ocean water by the Tropic Seamount

“…We combined these techniques in a case study of bacterioplankton growth in the sheath-water of a typical, standalone seamount -Tropic Seamount located in the North-Eastern tropical Atlantic Ocean 24 . Tropic Seamount was selected because it is sufficiently (~3,000 m) tall to retain deep-ocean water yet its summit is deep enough below the ocean surface (~1,000 m) to cause no pronounced surface seamount effect, which would unnecessary complicate the already challenging assessment.…”

Geochemical Investigations of Fe-Si-Mn Oxyhydroxides Deposits in Wocan Hydrothermal Field on the Slow-Spreading Carlsberg Ridge, Indian Ocean: Constraints on Their Types and Origin

“…Previous studies reported on three processes which gave rise to the Fe-oxyhydroxide deposits (i) The Fe-Si-Mn types that are predominantly formed by diffuse hydrothermal flow [3,12]. (ii) The Fe-Si-Mn types that are precipitated by seawater [31][32][33][34] and (iii) the Fe-Si-Mn types that are formed by mass wasting and corrosion of pre-existing sulfides [2,14]. However, these processes rarely occur in isolation and each may play an essential role in the precipitation of Fe-Mn oxyhydroxides at different stages [35,36].…”