Impact assessment of polymetallic nodule mining in the deep sea


This month, Dr. Anna Lichtschlag has been using the BOSCORF ITRAX to assess the geochemistry of sediments potentially containing valuable marine resources:

Polymetallic nodules are small concretions found worldwide on the seafloor in water depth of up to 6000 m. The nodules contain economically significant amounts of metals such as Ni, Cu, Zn, Co and Mo and for this reason they are a target for future mining operations. During mining of the nodules the seafloor sediments might be widely disturbed down to ½ m or more and this might lead to large-scale ecological and environmental impacts. To manage this environmental impact of mining operations a detailed knowledge of sediment geochemistry, and the depositional and biogeochemical processes operating in the sediments is essential.

The highest density of polymetallic nodule is reported from the Clipperton Fracture Zone (CCFZ) in the central equatorial Pacific. In 2015 we collect 6-m long sediment cores from the UK claim area and from an environmental protected zone (APEI: Areas of Potential Environmental Interest) from the CCFZ during an expedition with the NERC research vessel James Cook (JC120). The expedition was part of the EU MIDAS project (Managing Impacts of Deep-seA reSource exploitation,, a multidisciplinary research programme investigating the environmental impacts of extracting mineral and energy resources from the deep-sea environment.

We use the ITRAX core scanner to understand the high-resolution distribution and variation of elements, especially metals, in the sediment in the different areas of the CCFZ. More important, our results will help to understand if mining of Mn-nodules might have different environmental impacts in different areas of the CCFZ, depending on the redox-conditions and metal contents of the underlying sediments.