Minerals Report - International Seabed Authority

Current patterns, topography, bottom sediment and rock types and coverage,
seamount size, water depth, and size and magnitude of the oxygen-minimum
zone determine the make-up of the seamount communities, and population
density and diversity. Research and development on the technology of
mining crusts are only in their infancy. Detailed maps of crust deposits and a
better understanding of small-scale seamount topography are required to
design the most appropriate mining strategies.
2. Introduction
Cobalt-rich iron-manganese (ferromanganese) oxyhydroxide crusts
(see photographs in Appendix 1), hereafter called Fe-Mn crusts, are
ubiquitous on hard-rock substrates throughout the ocean basins. They form
at the seafloor on the flanks and summits of seamounts, ridges, plateaus, and
abyssal hills where the rocks have been swept clean of sediments at least
intermittently for millions of years. Crusts form pavements up to 250 mm
thick on rock outcrops, or coat talus debris. Fe-Mn crusts form by
precipitation from cold ambient bottom waters (hydrogenetic), or by a
combination of hydrogenetic and hydrothermal precipitation in regions
where hydrothermal venting occurs, such as near oceanic spreading axes,
volcanic arcs, and hotspot volcanoes. Fe-Mn crusts contain sub-equal
amounts of iron and manganese and are especially enriched in cobalt,
manganese, lead, tellurium, bismuth, and platinum relative to their
lithospheric and seawater concentrations (Table 1). There are two practical
interests in Fe-Mn crusts, the first being their economic potential for cobalt,
but also for manganese, nickel, and platinum, and possibly also titanium, rare
earth elements (REEs), tellurium, thallium, phosphorus, and others. The
second interest is the use of crusts as recorders of the past 60 million years
(Ma) of oceanic and climatic history. Besides the high cobalt contents
compared to abyssal Fe-Mn nodules, exploitation of crusts was viewed as
advantageous because most high quality crusts occur within the Exclusive
Economic Zone (EEZ; Fig. 1) of island nations and, therefore, are not subject to
some of the perceived problems of recovery of mineral resources occurring in
international waters.
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