The digital datasets generated in a MBES survey are readily manipulated in classification schema, usually with the intent to elucidate seabed geology, geomorphology and marine habitats ( Frejer et al., 2021 Lipton et al., 2016). In an early-stage exploration of their contract areas, the contractors typically employ 12 kHz multibeam echosounder (MBES) to get high-resolution bathymetric data ( DeWolfe & Ling, 2018 Global Sea Mineral Resources, 2018 Interoceanmetal Joint Organization, 2014 Lipton et al., 2016 Ruhlemann et al., 2011). States parties to the United Nations Convention on the Law of the Sea can sponsor public or private groups or enterprises, that may apply to the International Seabed Authority (ISA) for approval of plans of work for exploration for minerals resources (such as polymetallic nodules) in the area, which corresponds to the ocean floor and subsoil thereof, beyond the limits of national jurisdiction (International Seabed Authority, 2001). Biological material provides trace metals in a reduced state that can be oxidised and adsorbed into the open structures of the slowly precipitating phyllomanganate minerals within nodules. In the CCZ, the nodules are found at the seabed surface in a very soft sediment – seawater mix termed as the semi-liquid layer or geochemically active layer ( Bender et al., 1966 Callender & Bowser, 1980). This is thought to result from significant metal supply via net bio-carbonate/silicate export from the sea-surface critical metal release near the seabed via a combination of water depth relative to the lysocline and distance from continental land masses meaning an absence of competitor detrital sediments ( International Seabed Authority, 2010a Lipton et al., 2016 Morgan, 2003). Polymetallic (also called ferro-manganese) nodules are found in all of the world’s oceanic basins at the seabed surface, however, the nodules in the CCZ have consistently high metal grades, particularly of nickel, cobalt, copper and manganese.
The CCZ hosts a major seabed deposit of polymetallic nodules located between the Clarion and Clipperton fracture zones in the tropical north Pacific ( Horn et al., 1973 International Seabed Authority, 2010b Lipton et al., 2016).
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