An investigation into the variability of ferromanganese crusts in the NE Atlantic

Abstract

With the growth of renewable technologies, patterns in the demand for mineral resources required have shifted, with increasing demand for emerging technologies and a growing reliance on a wider suite of elements. Given their extreme enrichment in many of these critical elements, ferromanganese (FeMn) crust deposits have the potential to be an important future resource but the variability at the scale of a prospective exploration site remains poorly understood. This problem is acute for FeMn crust understanding in the Atlantic Ocean where fewer in-depth studies have been carried out to date. This study provides a systematic investigation into the distribution of FeMn crusts and the variation in texture and composition at the scale of an individual
seamount in the NE Atlantic. Relationships with environmental factors are investigated to provide an improved understanding of the formation, distribution and preservation processes that influence FeMn crust characteristics at this local scale. Ferromanganese crusts from Tropic Seamount were observed across a range of water depths and environments, and distribution modelling predicted highest presence probabilities
in summit and flank regions. The distribution of FeMn crusts at this scale is driven by both the substrate characteristics and interactions of local topography and current regimes which exert fundamental controls on the distribution of exposed hard surface and the period of exposure for FeMn crust precipitation. Concentrations of Co (mean of 0.5 wt%) and Te (mean of 51 ppm) in Tropic Seamount FeMn crusts showed the highest concentrations in summit regions, and coincide with regions of active surface erosion. Significant variability in composition was observed across the seamount. Statistical analyses of composition, alongside element mapping and textural studies,
showed that the high variability in FeMn crust composition is affected by local scale topography. Combined with the interaction with local current regimes, this can play a key role in determining the flux of detrital material to FeMn crusts and associated dilution of hydrogenetic FeMn phases.

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Identifiers

ORCID for Sarah Atinta Howarth: orcid.org/0000-0002-8017-8954

ORCID for Rachael James: orcid.org/0000-0001-7402-2315

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